Moisture power generation device

Abstract

A moisture power generation device comprising: a first electrode and a second electrode; and a functional layer disposed between the first electrode and the second electrode, the functional layer emitting charge carriers, the functional layer comprising at least two sublayers, the first sublayer acting as a moisture reservoir for the second sublayer to provide moisture to the second sublayer, and the second sublayer generating charge carriers in response to moisture available from the first sublayer.

Description

[Technical Field]

[0001] This patent application claims priority from Australian Patent Application Publication No. 2022902105 filed on 27 July 2022 and Australian Patent Application Publication No. 2023901264 filed on 28 April 2023, which are incorporated herein by reference in their entireties.

[0002] The present invention relates to moisture-generating devices, and more particularly to moisture-generating devices that include a layer that functions as a moisture reservoir. [Background technology]

[0003] Harvesting green energy from the environment will play a crucial role in the development of future energy supplies due to the scarcity of traditional energy sources. Moisture, one of the most abundant green energy sources, is still being utilized for energy harvesting and thermal energy-to-electricity conversion. Recently, moisture generators (MEGs) with ionizable groups or polar bonds in nanomaterials have been widely investigated for harvesting energy from environmental moisture and converting it into electricity through hygroscopic and iontophoretic migration. For example, oxygen functional groups in the surface of carbon nanomaterials interact with water molecules from moisture, dissociating them to generate mobile hydrogen ions. Therefore, more hydrogen ions in the outer layer exposed to moisture contribute to the hydrogen ion concentration difference for electrical potential. Furthermore, MEGs have also been demonstrated for use in wearable devices by harvesting moisture from breath or the environment, which offers great potential for self-powered wearable devices.

[0004] Generally, metal oxides (TiO2) and carbon-based materials (graphene oxide, polymers) have polar bonds or oxygen-based groups (-OH and -COOH) that form H +It has been adopted for MEG because it can absorb ions and induce electrical potential. In particular, graphene oxide (GO) exhibits a high specific surface area, abundant oxygen-based groups, and good mechanical properties, as well as rapid moisture absorption and stable electrical output. Furthermore, GO can be modified with oxygen-based groups or internal structures to further improve its electrical output. In recent studies, flexible MEGs based on graphene oxide have been developed with a thickness of 0.8 mm. 2 It has demonstrated an open-circuit voltage of 0.7 V at a small size of 1000 W. However, the voltage or current of the MEG is strongly related to the relative humidity (RH) in the environment, which indicates an instantaneous output that hinders its widespread application in power generation. Furthermore, the electrical output of the MEG needs further improvement so that it can be applied for power-supply devices with high power. The mechanism and enhancement of power generation should also be investigated to better determine its fabrication and application in power-supply devices in the future. Summary of the Invention [Means for solving the problem]

[0005] In one embodiment, a moisture power generation device includes a first electrode and a second electrode, and a functional layer disposed between the first and second electrodes, the functional layer emitting charge carriers, the functional layer including at least two sublayers, the first sublayer acting as a moisture reservoir for the second sublayer to provide moisture to the second sublayer, and the second sublayer generating charge carriers in response to moisture available from the first sublayer.

[0006] The inclusion of a water / moisture reservoir sublayer in a moisture harvesting (MEG) device facilitates controlling the delivery of moisture to the second (functional) sublayer. The functional sublayer may also be referred to as the active sublayer. The functional sublayer releases a charge upon absorbing moisture. For example, functional groups in the functional layer generate charge carriers by dissociating water molecules from moisture. The moisture reservoir itself contains water molecules, providing moisture delivery to the functional sublayer that is less dependent on environmental humidity conditions. The moisture harvesting device can generate charge under both low and high humidity conditions; for example, water in the moisture reservoir sublayer evaporates at low humidity and adsorbs water at high humidity. This can facilitate less fluctuation in the performance of the MEG device when environmental humidity conditions change, since moisture delivery to the functional sublayer can be maintained.

[0007] This sublayer can retain moisture and thus provide that moisture to other layers, thereby serving as a pool for other layers in the moisture-generating device. This sublayer functions as a moisture source for other sublayers in the moisture-generating device. This sublayer, acting as a moisture reservoir, can also be referred to as a hydration layer because it can hydrate the other sublayers. The advantage of providing a sublayer that functions as a moisture reservoir for the second sublayer is that it can hydrate the second sublayer. Moisture can be provided from the first sublayer to the second sublayer, meaning that the second sublayer can be hydrated even in low-humidity environmental conditions. Thus, the first sublayer can help hydrate the second sublayer even in extreme conditions (0% RH) due to the abundance of water in the ambient environment or within the first sublayer. The reservoir sublayer acts like a pool that can release water at low humidity and store water at high humidity.

[0008] These sublayers may have different primary functions, with the first sublayer acting as a moisture reservoir (hydration layer) for the second sublayer, and the second sublayer acting as a functional (active) layer that dissociates charge carriers upon absorbing moisture.

[0009] In another embodiment, the first sublayer comprises a polymer.

[0010] Polymers can be hydrated to contain a high water content. Polymers can be efficient moisture absorbers, meaning that moisture can be absorbed into moisture-harvesting devices even in low-humidity environments. This allows moisture to be absorbed more easily into moisture-harvesting devices than those with a single non-polymeric (e.g., GO) functional layer. This efficient moisture absorption property allows moisture harvesters to absorb water in low-humidity environments and improve the electrical performance of moisture-harvesting devices in low-humidity environments. Examples of polymers include 4-styrenesulfonic acid (PSSA), PSSNa, PAA, PVA, PSLi, PSSK, PSSNH4, PSSMg2, PSSAl3, PSSH, chitin, chitosan, cellulose, starch, rubber, alginate, carrageenan, polyamide, polyphenol, organic polyester, inorganic polyester, and polyanhydride. Polymers include hydrogels. Some advantages of polymers include flexibility, stretchability, ease of device fabrication, cost-effectiveness, translucency at low humidity, and processability.

[0011] Some polymers have hydrophilic functional groups and can therefore be water reservoirs. The polymers can also form a framework for holding salts.

[0012] In another embodiment, the first electrode, the second electrode and the functional layer are arranged in a stacked arrangement.

[0013] The stacking orientation is beneficial because it allows the interface between layers to have a relatively large surface area in the direction of charge movement between the electrodes. This creates a relatively large interface surface area between layers (e.g., a much larger surface area compared to the cross-sectional surface area of ​​the layers that would be used in the end-to-end interfacial connection between the layers). This large interface surface area reduces the internal resistance of the moisture harvesting device and provides the opportunity for high current compared to smaller contact areas. In principle, in-plane alignment would also work, but the internal resistance would be very high because ion migration requires a long path. The large interface surface area also allows a larger surface area for moisture to penetrate from the first sublayer into other sublayers.

[0014] In another embodiment, the sublayers are arranged in a stacked configuration to form a functional layer.

[0015] In another embodiment, the first and second sublayers are adjacent sublayers within the functional layer.

[0016] The adjacent sublayers provide an electrical interface between the surface of the first sublayer, which acts as a moisture reservoir for charge carrier transport between the layers, and the surface of the second sublayer. The adjacent sublayers allow direct moisture transport between the layers.

[0017] In some examples, the functional layer is a two-layer structure having two layers: a first sublayer that acts as a moisture reservoir for a second sublayer, and the second sublayer is the functional sublayer.

[0018] In another embodiment, the first sublayer releases charge carriers when the moisture power generating cell is exposed to moisture.

[0019] An advantage is that both the functional sublayer and the first sublayer are MEG layers. This may provide the advantage that additional charge carriers may be provided to the moisture harvesting device by the first sublayer in addition to those provided by the functional sublayer. This increase in the number of charge carriers may increase the electrical performance (such as voltage output) of the device compared to a single-layer MEG.

[0020] In another embodiment, the second sublayer has a net charge that is opposite to the charge of the charge carriers in the first sublayer.

[0021] The net charge of the second sublayer, which is opposite to the charge of the charge carriers in the first sublayer, is advantageous for attracting charge carriers from the first sublayer. These charge carriers in the first sublayer can be released. For example, if the second sublayer (e.g., a GO layer) has a net negative charge, protons or other cations present in the first sublayer (e.g., a polymer) are attracted toward the second sublayer. This charge attraction can facilitate increased charge flow through the MEG device and improve the electrical properties of the MEG device. Some examples may include increasing the voltage and current of a water-charged device.

[0022] In another embodiment, the second sublayer comprises a carbon-based material.

[0023] In another embodiment, the second sublayer comprises graphene oxide.

[0024] Graphene oxide is known to be a MEG material. Graphene oxide has a higher density than many other porous materials (e.g., Mxene). GO can adsorb excess water from the polymer layer. Because GO is negatively charged, it can attract protons or other positive charge carriers from the polymer layer.

[0025] In another embodiment, the moisture generating device is configured such that a second sublayer is positioned between the first layer and the second electrode, the second layer having a top surface facing toward the first sublayer and a bottom surface facing toward the second electrode, and the moisture generating device is configured to resist ingress of moisture into the bottom surface of the second sublayer.

[0026] An advantage of resisting moisture ingress into the bottom surface of the second sublayer is that a moisture gradient can be created across the moisture-powered device, which can create a charge gradient within the MEG device.

[0027] In another embodiment, the second electrode is insulating against moisture.

[0028] In another embodiment, the second sublayer is adjacent to and electrically connected to the second electrode.

[0029] In another embodiment, the first sublayer comprises an ionic salt.

[0030] The concentration of salt also plays an important role in device performance. The presence of ionic salt in the polymer layer provides mobile ions that can act as a medium for enhancing the ion concentration gradient across the device. This increases the number of ions in the first (water) layer. MEG devices containing ionic salt in the polymer layer can have higher voltage output than devices without ionic salt. These free ions significantly enhance the conductivity of the polymer layer.

[0031] Salts include NaCl and KCl. Li, Na, and K are considered Group 1 alkali metals.

[0032] Ionic salts also help the polymer absorb more water. They are hydrophilic salts.

[0033] In another embodiment, the first sublayer comprises a hydrogel.

[0034] Hydrogels are three-dimensional networks of polymer chains. They are cross-linked polymers. Hydrogels are hydrophilic and can absorb large amounts of water. The advantage of using hydrogels is that they have good moisture absorption properties. They can absorb moisture even in low-humidity environments. Hydrogels can be hydrated and provide a moisture source to adjacent sublayers. This makes them effective for use as moisture reservoirs (hydration layers). Hydrogels have a three-dimensional framework. This structure provides operational durability because, once hydrated, the structural integrity of the hydrogel layer can be maintained even in humid environments. This allows MEG devices to maintain their performance. Hydrogels are also versatile in that they can be doped with various ions. These are ionic hydrogels. For example, metal ions and salts can be infused into the hydrogel. This provides flexibility in charge carriers when designing MEG devices.

[0035] Hydrogels offer excellent water retention and can contain induced mobile ions. The hydrophilic nature of hydrogels with efficient moisture absorption means that the device is less limited by environmental humidity conditions compared to single-layer conventional MEGs and can still generate electricity in low-humidity environments.

[0036] In another embodiment, the first sublayer is doped with charge carriers.

[0037] Introducing additional charge carriers can improve the electrical performance of moisture-powered devices. + Abundant H from dissociation of ions + In a humid environment where ions and ions are present, the dominant charge carriers are H + ions. In a lower humidity environment, there are fewer H + Although the ions are dissociated due to the reduced amount of moisture, the metal ions from the first sublayer remain mobile and therefore can contribute to the electrical performance of the MEG device.

[0038] In another embodiment, the device is configured to absorb moisture from the environment, and its electrical performance improves in more humid environments.

[0039] The device may be arranged to absorb moisture from the environment, and the design of the device is arranged to allow absorption of moisture from the environment into the device, which is driven into the functional layers to provide electrical performance of the device.

[0040] According to a further aspect, a moisture power generation device includes a first electrode and a second electrode, a functional layer that releases charge carriers to the first electrode and the second electrode, and a layer that functions as a moisture reservoir to provide moisture to the functional layer.

[0041] In another embodiment, a layer that acts as a moisture reservoir to provide moisture to the functional layer is disposed between the first and second electrodes.

[0042] In another embodiment, the functional layer comprises at least two sublayers, a first sublayer that functions as a moisture reservoir and a second sublayer that provides charge carriers when provided with moisture.

[0043] According to a further aspect, a moisture power generation device includes a first electrode and a second electrode, and a functional layer disposed between the first electrode and the second electrode, the functional layer releasing charge carriers when the power generation cell is exposed to moisture, the functional layer including at least two sublayers, the sublayers being stacked between the first electrode and the second electrode (and adjacent layers being electrically connected), one of the sublayers being a polymer sublayer.

[0044] In another embodiment, the polymer sublayer acts as a moisture reservoir for adjacent sublayers when the power generating cell is exposed to moisture.

[0045] In another aspect, a moisture power generation device includes a first electrode and a second electrode, and a functional layer disposed between the first electrode and the second electrode, the functional layer releasing charge carriers when the power generation cell is exposed to moisture, the functional layer including at least two sublayers, the sublayers being stacked between the first electrode and the second electrode (and adjacent layers being electrically connected), and being polymer sublayers, one of the sublayers acting as a moisture reservoir for the adjacent sublayer when the power generation cell is exposed to moisture.

[0046] In another aspect, a power-generating cell includes a first electrode, a second electrode, and a functional layer located between the first electrode and the second electrode, the functional layer releasing charge carriers when the power-generating cell is exposed to moisture.

[0047] In another embodiment, the functional layer comprises at least two sublayers, the sublayers being stacked between a first electrode and a second electrode, and adjacent sublayers being electrically connected.

[0048] Each of the sublayers can release charge carriers when the power-generating cell is exposed to moisture. Each of the sublayers comprises a different material. The first of the sublayers can be a polymer sublayer. The polymer sublayer can be one of PSSA, PSSNa, PAA, PVA, PSSLi, PSSK, PSSNH4, PSSMg2, PSSAl3, and PSSH. The second of the sublayers can comprise one of MXene, MXene oxide, PVA, PAA, and GO.

[0049] In another embodiment, a second of the sublayers is adjacent to the first polymeric sublayer.

[0050] In another embodiment, the second of the sublayers comprises a carbon-based material that releases charge carriers when exposed to moisture.

[0051] In another embodiment, a first of the sublayers, which is a polymer sublayer, is adjacent to and electrically connected to the first electrode.

[0052] In another embodiment, the first electrode is porous to moisture.

[0053] The first electrode may include Ag, Zn, Zn plate, Zn foam, Al, Mg, Cu, Ni, Fe, or Ti.

[0054] In another embodiment, a second of the sublayers is adjacent to and electrically connected to the second electrode.

[0055] In another embodiment, the second electrode is insulating against moisture.

[0056] In another embodiment, the sublayers have different moisture absorption properties. In another embodiment, the moisture absorption properties of the sublayers decrease from the sublayer adjacent the first electrode to the sublayer adjacent the second electrode.

[0057] In another embodiment, the first of the sublayers, which is a polymer layer, acts as a moisture reservoir for the adjacent sublayer when the power generating cell is exposed to moisture.

[0058] In another embodiment, the first electrode exhibits an electrochemical reaction when contacted with moisture.

[0059] In another embodiment, the first electrode comprises at least one active metal: Al, Cu, Ni, Al, Zn, Zn foam, Mg, Fe, or Ti.

[0060] In another embodiment, the functional layer comprises PSSNa.

[0061] In another aspect, a power-generating cell includes a first electrode and a second electrode, and a functional layer located between the first electrode and the second electrode, the functional layer releasing charge carriers when the power-generating cell is exposed to moisture, the functional layer including at least two sublayers, the sublayers being stacked between the first electrode and the second electrode, each of the sublayers releasing charge carriers when the power-generating cell is exposed to moisture, a first of the sublayers being a polymer sublayer and electrically connected to an adjacent sublayer.

[0062] In another embodiment, the first of the sublayers is PSSNa.

[0063] In another embodiment, one of the sublayers is electrically connected to the second electrode and comprises GO.

[0064] In another aspect, a power-generating cell includes a first electrode and a second electrode, and a functional layer located between the first electrode and the second electrode, the functional layer releasing charge carriers when the power-generating cell is exposed to moisture, and the functional layer including PSSNa.

[0065] In order that the invention may be more clearly understood and put into practice, reference will now be made to a preferred embodiment of an assembly according to the invention. The description which follows is given by way of non-limiting example only and makes reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0066] [Figure 1] 1 illustrates a moisture generator battery cell having a functional layer, a first electrode, and a second electrode. [Figure 2] 1 illustrates a moisture generator battery cell having a functional layer, a first electrode, and a second electrode. [Figure 3] 1 illustrates an example of acidification of the functional layer of a moisture generator battery cell. [Figure 4] Figure 4(a) shows a structural diagram of one embodiment of MEG. Figure 4(b) shows a photograph of the device after acid treatment. Figure 4(c) shows the morphology of GO / PVA before acid treatment. Figure 4(d) shows the morphology of GO / PVA after acid treatment. [Figure 5] Figure 1 shows the voltage output of a GO / PVA film acidified with 32 wt% HCl at various relative humidities (RH). [Figure 6-1] Figure 6 shows the voltage output of GO / PVA films treated with various HCl concentrations. Figure 6(a) shows the voltage holding power. Figure 6(b) shows the maximum voltage output. [Figure 6-2] Figure 6(c) shows the voltage output of the GO / PVA film treated with various HCl concentrations. Figure 6(d) shows the voltage cycle. Figure 6(d) shows the current cycle. [Figure 7] Figure 7(a) shows the XRD patterns of the GO and GO / PVA films, and Figure 7(b) shows the interlayer spacing of the GO and GO / PVA films. [Figure 8] Figure 8(a) shows the XPS spectra of GO / PVA films with and without HCl acidification. Figure 8(b) shows the ratio of chemical bonds in GO / PVA films with and without HCl acidification. [Figure 9] Figure 9(a) shows the voltage holding power for 1 unit, 2 units, and 4 units. Figure 9(b) shows the current cycle for 1 unit, 2 units, and 4 units. Figure 9(c) shows the maximum voltage and current for 1 unit, 2 units, and 4 units. [Figure 10] Figure 10(a) is a photograph of the acidified GO / PVA on carbon cloth and its voltage output at room humidity of 45%. Figure 10(b) is the voltage output of flat acidified GO / PVA on carbon cloth at RH=75%. Figure 10(c) is the voltage output of acidified GO / PVA wrapped on a glass bottle with a diameter of 2 cm. Figure 10(d) is the voltage output of acidified GO / PVA wrapped on a glass bottle with a diameter of 1 cm. Figure 10(e) is the pattern design of the device array on FTO glass. Figure 10(f) is a photograph of a working computer powered by two devices in series. [Figure 11] 11(a) is a diagram of the device fabrication for a single MEG unit, FIG. 11(b) is a diagram of four units in series for voltage measurement, and FIG. 11(c) is a diagram of four units in parallel for current measurement. [Figure 12] Figure 12(a) shows a photograph of the GO film on the FTO glass, and Figure 12(b) shows the voltage cycle of the GO film at ΔRH = 75%. [Figure 13] Figure 13 shows the voltage output of GO / PVA films with various thicknesses (Figure 13(a) is 6.21 μm, Figure 13(b) is 12.23 μm, Figure 13(c) is 15.53 μm, and Figure 13(d) is 23.73 μm) after 32% HCl washing. [Figure 14] The voltage output of membranes with different areas (Figure 14(a) is 0.5 x 0.5 cm2, Figure 14(b) is 1.0 x 1.0 cm2, and Figure 14(c) is 1.5 x 1.5 cm2) is shown. [Figure 15] Figure 15(a) shows the FTIR spectra of the GO film, GO / PVA film, and HCl-washed GO / PVA film. Figure 15(b) shows the Raman spectra of the GO film, GO / PVA film, and HCl-washed GO / PVA film. [Figure 16] Figure 16(a) shows the voltage output of the GO / PVA membrane washed with 80 wt% acetic acid, Figure 16(b) shows the voltage output of the GO / PVA membrane washed with 20 wt% sodium hydroxide, Figure 16(c) shows the XPS spectrum of the GO / PVA membrane washed with 80 wt% acetic acid, and Figure 16(d) shows the XPS spectrum of the GO / PVA membrane washed with 20 wt% sodium hydroxide. [Figure 17] Figure 17(a) shows the fabrication of GO / PVA patterns after acidification with 32 wt% HCl, and Figure 17(b) shows two units in series to power a practical device. [Figure 18] Schematic of the fabrication of Ag electrodes. [Figure 19] Figure 19(a) is a digital photograph of the experimental setup showing the sample chamber for water generation and electrical connections, and Figure 19(b) is a digital photograph of the experimental setup showing the Keysight system for measuring the electrical output. [Figure 20] Diagram of five units in series for electrical output measurement. [Figure 21] Figure 21(a) is the voltage discharge curve of a single MEG battery cell with one resistor unit of 2000k ohms at RH=75%. Figure 21(b) is the voltage retention of a 5-connected MEG battery cell over 5.3 hours. Figure 21(c) is the voltage cycle of a 5-connected MEG battery cell. Figure 21(d) is the current cycle of a 5-connected MEG battery cell. [Figure 22] MEG with various functional layers for harvesting water from the environment is shown: Figure 22(a) is a diagram of abundant and sustainable water in the environment; Figure 22(b) is a structural diagram of the MEG device; Figure 22(c) is the voltage output of the GO film at RH=75%; Figure 22(d) is the voltage output of the PVA film at RH=75%; Figure 22(e) is the voltage output of the GO / PVA film at RH=75%. [Figure 23]Figure 23 shows a comparison of the electrical output of MEGs with various protonations. Figure 23(a) shows the voltage holding power of MEGs acidified with various HCl concentrations at RH = 75%. Figure 23(b) shows the Vmax of MEGs acidified with various HCl concentrations at RH = 75%. Figure 23(c) shows the voltage output of MEGs acidified with 32.0% HCl at various RHs. Figure 23(d) shows the EIS of MEGs with and without 32.0% HCl acidification at 55% room humidity. Figure 23(e) shows the current output of MEGs acidified with various HCl concentrations at RH = 75%. The Ag electrode area of ​​a single MEG is 0.5 × 0.2 cm2. Figure 23(f) shows the voltage output cycle of MEGs acidified with various HCl concentrations. Wet N2 was input to increase the electrical output until the moisture reached a maximum value and was then removed by dry N2 for one cycle. [Figure 24] Characterization and illustration of GO / PVA membranes during acidification are shown. Figure 24(a) shows power generation in acidified GO / PVA membranes. Protons in the functional groups of GO are mobilized by moisture absorption, resulting in charge separation through proton migration toward the inner layer. Conversely, the migration direction is reversed upon dehumidification, contributing to charge recombination. Figure 24(b) shows XPS spectra of GO / PVA membranes with and without HCl acidification. Figure 24(c) shows the ratio of chemical bonds in GO / PVA membranes with and without HCl acidification. Figure 24(d) shows the functional group changes during HCl acidification. After HCl acidification, C-O bonds are converted to C=O bonds, which have better stability. [Figure 25] Theoretical determination of the structural and proton-bonding properties of functionalized graphene oxide using DFT calculations. H-bonds of O-surface functionalized graphene oxide without (Figure 25(a)) and with (Figure 25(b)) carbon vacancies. H-bonds of OH-surface functionalized graphene oxide without (Figure 25(c)) and with (Figure 25(d)) carbon vacancies. HCl acidification promotes the formation of carbon vacancies. [Figure 26]Figure 26 shows the electrical output of MEG with various units at RH=75%. Figure 26(a) shows the current output of 1 unit, 2 units in parallel, and 4 units. The Ag electrode area of ​​1 unit is 0.5 × 0.2 cm2. Figure 26(b) shows the voltage holding power of 1 unit, 2 units in series, and 4 units. Figure 26(c) shows the Vmax and maximum current output of 1 unit, 2 units, and 4 units. [Figure 27] We demonstrate the use of MEG as a power source in various practical applications. Figure 27(a) shows the voltage output of an acidified GO / PVA film wrapped on a glass bottle with various curvatures at RH=75%. Figure 27(b) shows the Vmax of acidified GO / PVA on carbon cloth before and after 2000 bending cycles. Figure 27(c) shows the voltage output of a commercial capacitor charged by MEG at RH=75%. Figure 27(d) shows the electrical output of resistors with various resistances connected to MEG at RH=75%. Figure 27(e) shows the voltage signal of a pressure sensor powered by MEG at 55% room humidity. Figure 27(f) shows a photograph of a commercial pressure sensor powered by a single MEG at RH=55% room humidity. Figure 27(g) shows a photograph of a working computer powered by 2 series × 20 parallel MEGs at RH=75%. [Figure 28] Figure 1 shows XRD of pristine, HCl-acidified, and HNO-acidified GO films. [Figure 29] XPS spectra of GO films on FTO glass are shown. Figure 29(a) shows the pristine GO film without acidification. Figure 29(b) shows the GO film acidified by HNO3 vapor. Figure 29(c) shows the O / C ratio of the pristine GO film and the GO film acidified by 70 wt% HNO3 solution and vapor. [Figure 30] 1 illustrates the power output of one embodiment of an MEG device. [Figure 31] 1 illustrates the power output of one embodiment of an MEG device. [Figure 32] The morphology of the GO / PVA membrane is shown in Figure 32(a) - the surface of the pristine membrane. Figure 32(b) - the cross section of the pristine membrane. Figure 32(c) - the surface of the membrane acidified with 32% HCl. Figure 32(d) - the cross section of the membrane acidified with 32% HCl. [Figure 33]1 shows an MEG device having a functional layer with two sublayers. [Figure 34] 1 shows an MEG device having a functional layer with two sublayers. [Figure 35] 1 shows an MEG device having a functional layer with two sublayers. [Figure 36] 1 shows an MEG device having a functional layer with two sublayers. [Figure 36b] 1 shows an MEG device having a functional layer with two sublayers. [Figure 37] 1 shows a moisture-powered device comprising two sublayers. [Figure 38] The current characteristics of various samples of power generating cells are shown. The cell performance is measured in various humidity environments (RH%). [Figure 39] 1 shows the current characteristics of various samples of power generating cells. [Figure 40] 1 shows the voltage characteristics versus time of a first sample #1 having a silver (Ag) first electrode and a second sample #2 having a Zn plate first electrode. [Figure 41] 1 shows the electrical performance of various moisture-powered devices. [Figure 42] The voltages of the power generating devices with various second sublayers are shown. [Figure 43] 1 shows the voltage of moisture power generating devices with various first sublayers. [Figure 44] 1 shows the voltage across various sublayers in a moisture-generating cell for a cell containing a GO sublayer and a cell containing an acidified GO sublayer. [Figure 45] 1 shows the electrical performance of various moisture power generating cells with different top electrodes. [Figure 46] Further sample voltage results are shown. [Figure 47] 1 shows the voltage of a moisture harvesting device with a single functional layer disposed between an Ag top electrode and a CNT bottom electrode. [Figure 48]Figure 48(a) shows a schematic diagram of the HMEG with various applicable conditions, Figure 48(b) shows the sustainable power performance, and Figure 48(c) shows the self-healing via absorption of environmental moisture. Figure 48(d) shows a schematic diagram of the HMEG structure. Figure 48(e) shows the long-term measurement of the electrical performance of the HMEG at 25°C and 45%±10% RH. Figure 48(f) shows a radar plot showing the overall performance comparison of recently reported MEGs. [Figure 49] The power generation performance of the HMEG is shown in Figure 49(a). Figure 49(b) shows the voltage output under various RH conditions. Figure 49(c) shows the dynamic monitoring of the voltage output in response to varying RH. Figure 49(d) shows the power generation performance of the HMEG under various operating conditions. Figure 49(e) shows the cyclic weight measurement of HMEG with various gel contents exposed to oven (50°C, 15% RH) and ambient conditions (25°C, 45% RH) for 30 consecutive minutes. The original samples were dehydrated in an oven (HT) for 30 minutes, followed by absorption at ambient conditions (RT) to recover the moisture loss. Figure 49(f) shows the weight and current recovery of oven-dried (30 minutes) HMEG after settling at ambient conditions (25°C, 45% RH) for 1 hour with various LiCl concentrations. Figure 49(g) shows the voltage holding power of the HMEG exposed to ambient conditions (30%-65% RH) for 4 months. The inset shows the enlarged curve. Figure 49(h) shows the Voc and Isc of the HMEG under various loads at 45% RH. Figure 49(i) shows the comparison of the electrical performance between the proposed HMEG and the existing MEG. [Figure 50]The parameters affecting the output performance are shown. Figure 50(a) shows the electrical output of HMEG with various GO layer thicknesses at 45% RH. Figure 50(b) shows the electrical output of HMEG with various LiCl concentrations at 45% RH. Figure 50(c) shows EIS measurements of hydrogels with various LiCl concentrations. Figure 50(d) shows the water absorption capacity of HMEG-0% LiCl, HMEG-1.2% LiCl, and HMEG-4.8% LiCl. Figure 50(e) shows the effect of salt concentration on the weight and current output recovery of HMEG. Figure 50(f) shows Raman spectra of hydrogels with (i) 0% LiCl and (ii) 4.8% LiCl. Analysis of the state of water in the hydrogels by tracking the OH peak. The peaks at 3223 and 3400 cm-1 indicate free water. The peaks at 3515 and 3630 cm-1 indicate intermediate water. Figure 50(g) shows the water absorption capacity of HMEG with various hygroscopic salts at 45% RH. Figure 50(h) shows the electrical performance of HMEG with various hygroscopic salts at 45% RH. [Figure 51] The operating principle of the HMEG is shown in Figure 51(a) and Figure 51(b). Figure 51(b) shows FIR spectra of hydrogels with various concentrations of LiCl. Figure 51(c) shows XRD analysis of hydrogels with and without LiCl. Figure 51(c) shows 2D Raman mapping of hydrogels with various concentrations of LiCl to indicate the internal water content. Figure 51(d) shows XPS etching analysis of the underlying GO after peeling from the hydrogel. Figure 51(e) shows the voltage contribution of each component layer at 25 °C and 0% RH. Figure 51(f) shows a schematic diagram of the proposed operating mechanism under various conditions: (i) ambient conditions, (ii) high humidity (>65%), and (iii) low humidity (<15%). Due to its excellent water absorption ability, the hydrogel begins to harvest moisture from the humid airflow. Under dry conditions, water evaporation within the hydrogel is initiated. [Figure 52]Demonstration of the HMEG is shown. Figure 52(a) shows a series connection of the HMEG demonstrating the ability to scale up the voltage output. Figure 52(b) shows the voltage output versus the number of units, demonstrating a linear relationship. The inset shows the generated voltage from 168 devices and the magnified curve. Figure 52(c) shows a schematic of the flexible HMEG connected in series. Figure 52(d) shows 39 LEDs with a "UNSW" pattern powered by 168 devices connected in series. Figure 52(e) shows the charging of 100 μF and 470 μF capacitors by a single cell of the HMEG and each of the 168 cells. The inset shows the circuit for the charging process. Figure 52(f) shows the current response of the synapse device driven by a pulse train (amplitude: +3 V, width: 10 ms, duration: 30 ms) powered by the charging capacitor. The inset shows a schematic of the synapse device. Figure 52(g) shows the powered commercially available smart window and ink screen: i) and iii) before connection. ii),iv) After connection. [Figure 53] The fabrication process of hydrogel-based MEG is shown. [Figure 54] 1 shows a schematic diagram of the internal structure of a hydrogel. [Figure 55] Photographs of LiCl powder (a-c) and PVA-LiCl hydrogel (d-f) before and after water absorption are shown. Figure 55(a): LiCl powder before water absorption. Figure 55(b): LiCl powder after 2 hours of water absorption at 45% RH and deliquescence of the salt was observed. Figure 55(c): LiCl powder completely deliquesces into liquid after 24 hours of water absorption. Figure 55(d): PVA-4.8% LiCl hydrogel before water absorption. Figure 55(e): PVA-4.8% LiCl hydrogel after 2 hours of water absorption at 45% RH, no physical changes were observed. Figure 55(f): PVA-4.8% LiCl retains its original state after 24 hours of absorption. [Figure 56] Figure 56(a) shows the measurement conditions in an oven (50°C, 15% RH), and Figure 56(b) shows the stability of the voltage output of HMEG-4.8%LiCl at 50°C and 15% RH. [Figure 57] 1 shows the electrical performance of the HMEG at 0% RH. [Figure 58]Figure 58(a): Voltage generation performance and Figure 58(b): Current generation performance of a device with a single GO layer at various RH. [Figure 59] The power generation performance of a device with a single GO layer at 0% RH is shown. [Figure 60] Figure 60(a): Hydrogels were set at -20°C for 40 minutes, 2 hours, and 24 hours. The hydrogels retained their original appearance; no frozen areas were observed after 1 day. Figure 60(b): Hydrogels with 0 and 4.8% LiCl were set at 50°C for 1 hour. Small shrinkage was observed in the hydrogel with 4.8% LiCl. [Figure 61] Figure 61(a): Voltage performance, and Figure 61(b): Current performance under ambient conditions (25°C, 40% RH) and in an oven (50°C, 15% RH). [Figure 62] The devices without LiCl were peeled off from the substrate after 1 day at room conditions. [Figure 63] Cyclic voltage and weight measurements of HMEG with 4.8% LiCl exposed to oven (50° C., 15% RH) and ambient conditions (25° C., 45% RH) for 30 consecutive minutes. [Figure 64] Water retention of HMEG with various concentrations of LiCl. [Figure 65] Power output of the device with external resistor connection at 45% RH. [Figure 66] The long-term voltage stability of the devices without the hydrogel layer and the bGO layer under room conditions. [Figure 67] Figure 67(a) and Figure 67(b) show the effect of hydrogel thickness on the performance of the HMEG. Figure 67(c) shows the electrical performance of the HMEG with various electrode sizes. [Figure 68] Water absorption capacity of pure GO layer at 25 °C and 45% RH. [Figure 69] Figure 69(a) is a schematic illustration of the interactions between salt ions and water molecules in a low concentration hydrogel, and Figure 69(b) is a schematic illustration of the interactions between salt ions and water molecules in a high concentration hydrogel. [Figure 70]This shows the change in the ratio of intermediate water to free water in the hydrogel when LiCl salt is introduced. [Figure 71] Voltage output of HMEGs assembled with different top electrodes (FIG. 71(a): CNT, FIG. 71(b): Ag, and FIG. 71(c): Cu) at 45% RH. [Figure 72] XPS analysis to reveal the resistance of Li and Cl ions throughout the underlying GO layer. [Figure 73] Figure 73(a) is a cross-sectional SEM image of the exfoliated GO layer, Figure 73(b) is the EDS mapping of Cl element, and Figure 73(c) is the EDS mapping index. [Figure 74] Figure 74(a) is a photograph of the bottom GO after peeling off the top hydrogel layer, and Figure 74(b) shows the Voc and Isc of the bottom GO and pristine GO at 45% RH. [Figure 75] Figure 75(a) shows the CV curves of HMEG under various working conditions. [Figure 76] Figure 76(a) shows a photograph of 168 units connected in series, and Figure 76(b) shows a photograph of the LED lighting. [Figure 77] Figure 77(a) is a photograph of 168 units connected in series in the flat state, and Figure 77(b) is a photograph of 168 units connected in series in the bent state. [Figure 78] FIG. 1 is a schematic diagram of the circuit design of an MEG-powered E-ink display. DETAILED DESCRIPTION OF THE INVENTION

[0067] Single-layer MEG device: In an exemplary device, a functional layer of a moisture-harvesting battery cell is provided. The moisture-harvesting device generates electricity when exposed to moisture due to the interaction of the moisture with the material. Ionization occurs when HO molecules promote the dissociation of functional groups (-OH and -COOH) within the functional layer. The mobilized H + The ions are released as charge carriers for power generation. + At least some of the ions remain mobile to provide the electrical properties of the functional layer.

[0068] Moisture includes H2O molecules. H2O molecules can exist in liquid (water) or water vapor. The term "moisture" is used in this application and should be understood to refer to H2O molecules in any state.

[0069] The functional layer includes at least one composite layer including a carbon-containing material and a binder. The carbon-containing material may include a carbon nanomaterial.

[0070] One example of a carbon-containing material is graphene oxide (GO). Graphene oxide (GO) is known to exhibit high specific surface area, abundant oxygen-based groups, and good mechanical properties, as well as rapid moisture absorption and stable electrical output. Other examples of carbon-containing materials include carbon nanotubes, MXene, or carbon nitride (CN).

[0071] The binder provides interfacial adhesion between the functional layer and the electrode when the electrode is applied to the functional layer. The binder provides stability of the adhesion between the functional layer and the electrode. A functional layer including a binder maintains good adhesion to the electrode (e.g., over time, electrical testing, and exposure to moisture). Improved adhesion provides improved mechanical adhesion between the functional layer and the electrode. Improved adhesion also provides improved electrical stability over multiple charging cycles. Without a binder, the functional layer may exhibit poor stability and reliability of electrical performance. For example, the functional layer may detach from the electrode. The binder may be conductive or non-conductive.

[0072] Binders include electrically insulating polymers. Examples of binders include: polyvinyl alcohol (PVA), polyvinyl butyral (PVB), poly(methyl methacrylate) (PMMA), and polyvinylpyrrolidone (PVP). PVA has abundant hydroxyl groups that allow moisture to be absorbed from the environment. PVA also has good viscosity, making it a good candidate for printing. As discussed above in connection with binders, PVA provides stable attachment of the functional layer to the electrode.

[0073] Within the device, the functional layer is a composite layer containing graphene oxide (GO) and polyvinyl alcohol (PVA). The PVA can modify the spacing between the graphene oxide layers. The PVA can increase the spacing between the graphene oxide layers. The increased spacing can increase the maximum voltage and current of the MEG battery cell containing the composite layer of graphene oxide and polyvinyl alcohol.

[0074] The inclusion of a binder can increase the interlayer spacing of the carbon-containing material compared to the interlayer spacing of the binder-free carbon-containing material. The increased interlayer spacing allows for greater penetration of moisture into the functional layer. The greater penetration of moisture allows for a greater number of H + This allows ions to dissociate. However, if the layer spacing increases too much, the internal resistance of the functional layer increases.

[0075] In an exemplary device, a functional layer for a water-powered battery is provided, the functional layer comprising graphene oxide having a ratio of C=O bonds to C-C bonds greater than 1:9. Examples of a ratio greater than 1:9 include 2:9, 1:8, 1:5, etc. In some embodiments, the ratio of C=O bonds to C-C bonds is greater than 1:8, or greater than 1:7, or greater than 1:6, or greater than 1:5. In some embodiments, the ratio of C=O bonds to C-C bonds is less than 1:1. The bond ratio in the functional layer can be measured, for example, by using X-ray photoelectron spectroscopy (XPS).

[0076] C=O is a double bond between an oxygen atom and a carbon atom. CC is a single bond between a carbon atom and another carbon atom.

[0077] As discussed above, the functional layer can be comprised of a carbon-based material and a binder. The carbon-based material can be graphene oxide. The binder can be a polymer binder selected to bond with the conductive substrate. Examples of polymer binders include one or more of the following: PVA, PVB, PMMA, or PVP.

[0078] In some embodiments, the graphene oxide and polymer binder are a generally homogeneous mixture, with the graphene oxide and polymer binder mixed in a mass ratio ranging from 100:1 to 2:1.

[0079] In an exemplary device, a functional layer of a moisture-powered cell is provided, the functional layer including treated graphene oxide having a layer spacing greater than the layer spacing of the graphene oxide from which the treated graphene oxide is made.

[0080] In the functional layer, the processed graphene oxide may have a ratio of C=O bonds to C-C bonds of greater than 1:9. Examples of ratios greater than 1:9 include 2:9, 1:8, 1:5, etc. In some embodiments, the ratio of C=O bonds to C-C bonds is greater than 1:8, or greater than 1:7, or greater than 1:6, or greater than 1:5. In some devices, the ratio of C=O bonds to C-C bonds is less than 1:1. The bond ratio in the functional layer can be measured, for example, by using X-ray photoelectron spectroscopy (XPS).

[0081] In an illustrative example, the layer spacing of the treated graphene oxide is ≧0.799 nm.

[0082] As discussed above, the functional layer can be comprised of a carbon-based material and a binder. The carbon-based material can be graphene oxide. The binder can be a polymer binder selected to bond with the conductive substrate. Examples of polymer binders include one or more of the following: PVA, PVB, PMMA, or PVP. The layer spacing of the treated graphene oxide can be ≧1.00 nm or ≧1.10 nm.

[0083] In an exemplary device, the functional layer includes multiple sublayers, at least one of the sublayers having a first ratio of C=O to C-C bonds and at least one of the other sublayers having a second ratio of C=O to C-C bonds, the first ratio being higher than the second ratio, with each sublayer having a different ratio of C=O to C-C bonds, and the sublayers arranged to define a gradient in the ratio through the functional layer.

[0084] In an exemplary device, a moisture-harvesting battery cell includes a functional layer, a first electrode, and a second electrode. The functional layer is disposed between and electrically connected to the first electrode and the second electrode. The moisture-harvesting battery cell is configured to generate a moisture sorption gradient across the functional layer when exposed to moisture.

[0085] The water-powered battery cell is charged by the reaction of H2O molecules with the functional layer of the water-powered battery cell to produce ionization. The H2O molecules can be provided in a liquid, liquid water, or water vapor. The water includes H2O molecules. During ionization, the water is brought into contact with the functional layer and promotes dissociation of the functional groups (-OH and -COOH) of the functional layer. This results in the formation of mobilized H + as charge carriers for power generation.

[0086] Both sides of the functional layer (e.g., the top side of the functional layer) are mobilized H + High concentration of mobilized H compared to the concentration of ions + A charge gradient is generated across the functional layer by creating a charge gradient across the functional layer (having ions). This charge gradient generates a potential difference across the functional layer. Mobilized H + Ions are high H + From the ion concentration region to low H + The molecules migrate to the region of concentration, generating a current through the functional layer.

[0087] Mobilization H + Because ions are generated by dissociation of functional groups when the functional layer is exposed to moisture, a charge gradient can be created across the functional layer by also creating a moisture absorption difference between the two sides of the functional layer. For example, if the top side of the functional layer is exposed to moisture, a high concentration of H + is released in the top layer due to the reaction of moisture with the functional layer. If the bottom layer of the functional layer is not exposed to moisture or is exposed to less moisture, a low concentration of H + Ions are released at the bottom layer. This difference in moisture exposure across the functional layer creates a charge gradient across the functional layer, charging the MEG battery cell.

[0088] The charge gradient across the functional layer is related to the voltage output of the MEG battery cell. Generally, the greater the protonation gradient across the functional layer, the greater the voltage of the MEG battery cell.

[0089] The electrical performance of an MEG battery cell can be improved by creating a moisture absorption differential across the MEG battery cell. In some exemplary embodiments, a moisture absorption differential is created across the functional layer of the MEG battery cell when the MEG battery cell is exposed to moisture. This moisture absorption differential creates a moisture absorption gradient across the functional layer. The moisture absorption differential creates an ion gradient across the functional layer when the water-based battery cell is exposed to moisture.

[0090] In some exemplary devices, differential moisture absorption is achieved across the functional layer by providing first and second electrodes comprising different electrode materials. The electrodes are asymmetric. Preferably, the electrodes have asymmetric moisture absorption characteristics such that the electrodes allow different amounts of moisture to penetrate into the electrodes and contact the functional layer.

[0091] The first electrode of the MEG device can be porous to moisture, and the second electrode can be impermeable to moisture.

[0092] The first electrode allows moisture to penetrate into the electrode and into the functional layer. The second electrode is configured to resist moisture from penetrating into the electrode and into the functional layer. The second electrode may not allow any moisture to pass through the electrode, as it may prevent moisture from penetrating into the electrode and into the functional layer. The second electrode may be waterproof. The second electrode may provide resistance to moisture penetration by preventing at least a portion of the moisture from penetrating into the electrode.

[0093] The first electrode may comprise silver nanowires or zinc, nickel, magnesium or other metals.

[0094] The second electrode may include at least one of FTO, ITO, carbon nanotubes, graphene or carbon black, and MXene.

[0095] Factors used to control moisture absorption into the functional layers of a battery cell include the design of the electrodes and the materials used for the electrodes.

[0096] The choice of materials used for the electrodes can affect the electrical performance of MEG battery cell devices. Improved performance of MEG battery cell devices can be achieved if moisture can penetrate one surface of the functional layer more than the other surfaces of the battery cell. This creates a moisture absorption differential across the battery cell, as one surface of the functional layer is exposed to and absorbs more moisture than the other surfaces. For example, a difference in moisture contacting the top and bottom surfaces creates an electrical potential across the functional layer.

[0097] Referring now to FIG. 1 , an MEG battery cell 100 includes a composite GO / PVA layer 110. This is the functional layer of the MEG battery cell. A first electrode 130 is attached to a first surface 120 of the GO / PVA layer 110. A second electrode 150 is attached to a second surface 160 of the GO / PVA layer 110. In the example of FIG. 1 , the first surface 120 and the second surface 160 are opposite sides of the composite GO / PVA layer. For purposes of explanation, electrode 130 will be referred to as the bottom electrode and electrode 150 will be referred to as the top electrode. It should be apparent that the orientation of the battery cell is not limiting and these labels are used for explanation purposes only.

[0098] The GO / PVA layer 110 has length (l) and depth dimensions that are much larger than its thickness (E). For example, the thickness of the GO / PVA layer is about 0.5 mm, the length is about 1 cm, and the depth is about 1 cm. The surface area of ​​surfaces 120 and 160 is large compared to the thickness.

[0099] 1 , the battery cell is configured to promote water absorption into the top surface 160 of the GO / PVA layer 110 and resist water absorption into the bottom surface 120 of the GO / PVA layer 110. This configuration promotes creating a moisture absorption differential between the surfaces of the functional layers when water is applied to the battery cell. This promotes an abundance of water absorbed into the top surface of the functional layer 160 and a lack of water absorbed into the bottom surface of the functional layer 120.

[0100] In FIG. 1 , the electrode 150 is configured to cover only a portion of the top surface 160 of the GO / PVA layer. The electrode does not fully cover the top surface 160. The remainder of the top surface of the GO / PVA layer is left uncovered. This allows direct contact of moisture onto the top surface. A larger top electrode can result in a larger current carrying capacity to the electrode junction through the GO / PVA. However, if the electrode is too large, water may be prevented from escaping the GO / PVA layer and moisture may also be prevented from contacting the surface through the electrode.

[0101] In FIG. 1, the top electrode 150 is silver.

[0102] In another device, electrode 150 may cover the entire top surface 160 of the GO / PVA layer. Such an electrode should be hygroscopic, allowing moisture to penetrate into the electrode and onto the GO / PVA layer. Such an electrode may be porous. In one embodiment, electrode 150 comprises silver nanowires.

[0103] In Figure 1, electrode 130 extends across the entire bottom surface of the GO / PVA layer. Electrode 130 covers the bottom surface of the GO / PVA layer. Examples of suitable materials for the first electrode include carbon-based materials (e.g., carbon nanotubes or graphene). Other suitable materials for the bottom electrode include FTO, ITO, MXene, Au, Pt, and carbon black.

[0104] By covering the bottom surface, electrode 130 reduces the penetration of water through electrode 130 into GO / PVA layer 110. Preferably, electrode 130 prevents water from penetrating into GO / PVA layer 110. Preferred electrodes have moisture insulating properties to resist water penetration into the GO / PVA layer.

[0105] Preferably, the first electrode 130 has moisture insulating properties to resist moisture penetration into the GO / PVA layer 110. Moisture penetration into the first electrode 130 and into the GO / PVA layer is reduced by using an electrode with moisture insulating properties. Preferably, the first electrode 130 prevents moisture penetration into the GO / PVA layer 110 through the electrode 130. In the example of FIG. 1 , the electrode 130 extends across the entire bottom surface of the GO / PVA layer. Examples of suitable materials for the first electrode include carbon-based materials (e.g., carbon nanotubes, graphene). Other suitable materials for the bottom electrode include FTO, ITO, MXene, Au, Pt, and carbon black.

[0106] Additional resistance to moisture penetration can be provided by mounting the first electrode 130 on a separate substrate. This can improve the moisture resistance properties of the bottom layer by requiring any moisture that penetrates the bottom layer 120 of the battery cell to first penetrate into the substrate and then into the first electrode 130 in order to penetrate into the GO / PVA layer.

[0107] In the example of Figure 1, the electrode 130 covers the surface of the GO / PVA layer 110. As shown in Figure 1, the first electrode 130 extends across the entire bottom surface of the GO / PVA layer 110. This configuration shields the entire surface from direct contact with moisture. As discussed above, this helps reduce moisture penetration across the bottom surface of the cell.

[0108] The electrical performance of a battery cell can also be improved by selecting an electrode material with suitable mechanical properties. Improved electrical performance can be achieved by using an electrode comprising a material with similar mechanical properties to the GO / PVA composite layer (e.g., a material with a similar thermal expansion coefficient to the composite layer). By having similar thermal expansion coefficients, the functional layer composite layer 110 and the electrode 130 tend to expand and contract proportionally. This maintains adhesion between the composite layer 110 and the electrode 130 during use. A small amount of PVA between the GO and the electrode also improves mechanical properties. This facilitates extending the use of MEG battery cells by preventing poor electrical contact and increased resistivity at the interface between the electrode and the composite layer over time.

[0109] In Figure 1, the first electrode is a carbon nanotube. In another device, the first electrode is graphene, which has similar mechanical properties to the GO / PVA composite layer.

[0110] In devices where the functional layer is pure graphene oxide, a small amount of PVA or other adhesive may be applied between the functional layer and the electrode to improve adhesion.

[0111] Another benefit of the first electrode 130 extending across the entire surface of the GO / PVA layer 110 is that the contact area between the GO / PVA layer 110 and the electrode 130 is increased compared to an electrode extending partially across the entire GO / PVA layer. This larger contact area results in an increased surface area for electrical junction. The larger contact area may reduce the electrical resistance of the junction.

[0112] Preferably, the bottom electrode 130 includes one or more of the following properties: moisture repellency, waterproofness, moisture resistance, flexibility; good adhesion at the interface with the composite layer; flexibility; light weight; a thermal expansion coefficient similar to that of the composite layer; good adhesion at the GO / carbon nanotube interface; high conductivity; and flexibility.

[0113] The considerations for the top electrode 150 are different from those for the bottom electrode 130. To create a moisture gradient across the functional layers of the MEG battery cell, moisture absorption into the top surface 160 of the GO / PVA layer is promoted.

[0114] In FIG. 1 , electrode 150 is configured to cover only a portion of the top surface 160 of the GO / PVA layer. The remainder of the top surface is left uncovered and exposed to allow direct contact of moisture onto the top surface when the MEG battery cell is exposed to moisture. Electrode 150 can be porous. Electrode 150 can be porous to moisture. A larger top electrode with a larger contact area with the functional layer can result in a larger current-carrying capacity to the electrode junction through the GO / PVA. However, if the electrode is too large, water may be prevented from escaping the GO / PVA layer, and moisture may also be prevented from contacting the surface through the electrode.

[0115] Shown in Figure 2 is another MEG battery cell. Figure 2 includes the same GO / PVA functional layer 110 and first electrode configuration 130 described above in connection with Figure 1. In Figure 2, the second electrode 250 is porous. The second electrode 250 is porous to allow moisture penetration. The second electrode 250 covers the surface 160 of the GO / PVA functional layer. In another device, the second electrode may partially cover the surface 160 of the functional layer.

[0116] The porosity of electrode 250 allows moisture to penetrate into the electrode and into the top surface of GO / PVA layer 110. As a result, larger electrodes can be used that cover a larger portion of the top surface of the GO / PVA functional layer but allow moisture to be absorbed into the GO / PVA layer. Moisture is absorbed and penetrates through electrode 250 into the surface of functional layer 110. A porous electrode increases the contact area between electrode 250 and the GO / PVA surface, facilitating achieving high currents. In the example of FIG. 2, second electrode 250 covers the top surface of GO / PVA layer 160.

[0117] In FIG. 2, electrode 250 is a silver nanowire-based electrode.

[0118] More generally, examples of porous second electrodes include electrodes containing metal nanowires. Preferably, the metal should have good corrosion resistance and a lower work function compared to GO. Because the metal nanowires have a network structure, moisture can penetrate into the electrode and into the GO / PVA layer.

[0119] The top electrode is applied as an ink. Preferably, the ink contains 0.1% to 20% by weight of silver nanowires. In one exemplary embodiment, the ink is a 1% by weight silver nanowire ink. The ink is drop-coated, gravure-coated, or screen-coated onto the MEG device.

[0120] In an exemplary embodiment, a moisture power generation cell is provided, in which a work function gradient is generated between a first electrode, a functional layer, and a second electrode, where the work function of one of the first electrode or the second electrode is higher than the work function of the functional layer, and the work function of the other of the first electrode or the second electrode is lower than the work function of the functional layer.

[0121] The electrical performance of a water-powered cell and the choice of electrode material are also influenced by the work function of the material. GO has a work function of approximately 4.7-4.9 eV.

[0122] A suitable electrode configuration can induce a Schottky barrier at the electrode / GO interface that can better align with the direction of proton diffusion in GO, thereby enhancing voltage output. In particular, GO has a work function of approximately 4.7-4.9 eV, so a top electrode with a smaller work function would hinder the recombination of electrons and protons. One suitable material is zinc, which has a work function of 4.3 eV, much smaller than GO. In one exemplary embodiment, the top electrode is a zinc foil approximately 0.5 mm thick.

[0123] Preferably, the bottom electrode has a higher work function than the GO / PVA layer, which creates a work function gradient across the MEG battery cell device from the first electrode to the GO / PVA functional layer and second electrode.

[0124] The work function gradient can increase from the first electrode to the second electrode, or from the second electrode to the first electrode. Thus, the work function of one electrode is higher than that of the GO / PVA layer, and the work function of the other electrode is lower than that of the GO / PVA layer. When the work function of one of the first electrode or the second electrode is higher than that of the composite layer, and the work function of the other of the first electrode or the second electrode is lower than that of the composite layer, a work function gradient is generated between the first electrode, the composite layer, and the second electrode.

[0125] Preferably, the electrically insulating polymer is water-soluble. The GO solution and binder solution are mixed in a 1:1 mass ratio by sonication. Other mixing mass ratios, ranging from 100:0 to 100:200, can be used. A 1:1 ratio has been found to provide good attachment of GO / PVA to the substrate and electrodes.

[0126] Preferably, the GO solution and binder solution are in the form of an ink, which is printable.

[0127] The following description describes fabrication techniques and considerations for a moisture generator battery cell. The battery cell includes at least one functional layer between two electrodes. The functional layer can include graphene oxide. The functional layer can include a composite layer including a carbon-containing material and a binder. The carbon-containing material can be graphene oxide (GO). The binder can be polyvinyl alcohol (PVA).

[0128] Various configurations of electrodes and substrates are described for various embodiments and fabrication techniques. The functional layer is deposited on the electrode substrate so that the bottom surface of the functional layer is in contact with the electrode substrate. Another electrode is placed on top of the layer to complete the battery cell.

[0129] The binder improves the adhesion of the layer to the electrode.

[0130] Other materials can be used in place of GO and / or PVA. Carbon nanotubes are an alternative to GO. Oxygen-containing polymers with tunable electrical properties can be used in place of graphene oxide.

[0131] The functional group density of an MEG battery cell can be tuned to change the electrical properties of the MEG battery cell. The functional group density can be tuned by an acid treatment. Acid treatments are described below and include immersion treatments and vapor treatments. The acid treatment can be applied before or after the functional layer is deposited on the electrode. The acid treatment can be applied to the functional layer while the layer is in liquid form or when the functional layer is in film form.

[0132] In an exemplary method, GO powder was synthesized by oxidation of graphite powder according to the Hummers method. A 20 mg / mL GO solution was obtained by dispersing GO powder in distilled water by sonication for 30 min. A 20 mg / mL polyvinyl alcohol solution was obtained by dissolving PVA powder (molecular weight 13,000-23,000) in distilled water at 90 °C for 30 min.

[0133] Some samples were made of fluorine-doped tin oxide (FTO) glass measuring 2.5 × 2.5 cm. 2 It was cut into pieces and used as the substrate / bottom electrode. Other conductive substrates can be used instead of the FTO coated glass (e.g., ITO coated glass or other conductive electrode materials).

[0134] In some other devices, substrates / electrodes of various sizes were used. In these embodiments, fluorine-doped tin oxide (FTO) glass was used, measuring 1.0 × 2.0 cm. 2 It was cut into pieces and used as the substrate / bottom electrode.

[0135] The FTO glass was then washed with ethanol and deionized water, followed by 30 minutes of UV radiation, which can remove organic impurities on the substrate.

[0136] The GO solution and the polyvinyl alcohol solution are mixed in a 1:1 mass ratio by sonication. Other mixing mass ratios, ranging from 100:0 to 100:10, can be used. A 1:1 mass ratio can provide good attachment of GO / PVA to the substrate.

[0137] This mixture is 1 x 1 cm 2 It was dried directly onto FTO glass at 50°C for 12 hours to form a GO / PVA film. Additional layers of this mixture can be applied to increase the thickness of the GO / PVA layer. Typically, additional layers are deposited after the previous layer has dried. In other embodiments, the layers can be various mixtures.

[0138] The mixture can be applied to a substrate by using various methods. In one exemplary method, the mixture can be applied by using spin coating or drop coating techniques. Printing techniques, including screen printing, can also be used to apply the mixture. Printing techniques are particularly useful when the mixture is an ink.

[0139] The concentration of the material can be controlled, which affects the porosity.

[0140] In another embodiment, carbon cloth was used as the electrode substrate, which is conductive and flexible. The carbon cloth was immersed in the GO / PVA solution for 10 minutes and dried for 12 hours. Other immersion periods may be used. Various drying periods may be used.

[0141] A top electrode can be applied to the membrane before or after the acid treatment of the MEG battery cell (described below).

[0142] There are several considerations of electrode construction that can affect the performance of MEG battery cell devices, including the water absorption and repulsion characteristics of the electrodes, the mechanical properties of the electrodes, and the work function of the electrodes. These are discussed next in relation to each electrode.

[0143] In another system, a method for fabricating a functional layer of a water battery cell is provided. The functional layer is provided as a mixture. The mixture is exposed to an acid treatment. The mixture can be a solution of graphene oxide. The mixture can be a mixture of graphene oxide and a polymer binder.

[0144] The acid treatment involves applying an acid to the mixture. Preferably, the acid is at least one of hydrochloric acid, nitric acid, or sulfuric acid. The acid treatment can be a liquid treatment or a vapor treatment.

[0145] Preferably, creating the mixture comprises mixing a solution of graphene oxide. The mixture may comprise mixing a solution of graphene oxide with a solution of a polymer binder. Exposing the mixture to an acid treatment comprises mixing a liquid acid into the mixture. The mixture is a printable solution, and in one embodiment, the acid treatment involves mixing the acid with the printable solution prior to printing the functional layer onto the substrate.

[0146] In other systems, the method includes applying an acid treatment after the mixture is applied to a substrate. The substrate can be an electrode.

[0147] The acid treatment can be applied while the mixture is in liquid form. The acid treatment can be applied when the mixture is in solid form (e.g., as a functional layer deposited on an electrode).

[0148] In an exemplary system, the acid used during the acid treatment has a concentration in the range of 0.1 to 70% by weight. The acid used during the acid treatment has a concentration in the range of 1 to 30% by weight to 50% by weight. The acid concentration can be selected based on the acid used in the acid treatment.

[0149] The acid treatment has the effect of increasing the ratio of C=O bonds to C-C bonds in the functional layer.

[0150] In some embodiments, the method includes creating multiple mixtures, each containing graphene oxide and a polymer binder, and then exposing each mixture to a different acid treatment so that each mixture has a different ratio of C=O to C-C bonds. The various mixtures are then stacked to form a functional layer containing a series of sublayers, the mixtures being stacked in order of the ratio of C=O to C-C bonds. The functional layer containing the series of sublayers is positioned between a top electrode and a bottom electrode to form a MEG battery cell.

[0151] The step of preparing a mixture of graphene oxide and a polymer binder includes dissolving water-soluble graphene oxide in water to form a graphene oxide solution, dissolving a water-soluble polymer binder in water to form a polymer binder solution, and mixing the graphene oxide solution and the polymer binder solution.

[0152] The graphene oxide solution and the polymer binder solution are mixed in a 1:1 mass ratio.

[0153] The graphene oxide solution may contain 10 to 30 mg / mL of graphene oxide.

[0154] The graphene oxide solution may contain 10-30 mg / mL of polymer binder.

[0155] In one example, to treat the MEG, the MEG battery cell was immersed in hydrochloric acid for 10 minutes. The MEG battery cell was then washed with distilled water for 10 minutes. The MEG was then dried at 50°C for 12 hours for electrical measurements. Various samples were immersed in hydrochloric acid with various concentrations, and then the electrical properties of each sample were tested. Hydrochloric acid with concentrations of 0.5 wt%, 1 wt%, 16 wt%, and 32 wt% was used.

[0156] In this example, the bottom surface of the GO / PVA layer was attached to a conductive substrate. The conductive substrate is liquid-resistant, so it resists acid penetration through the conductive substrate and onto the bottom surface of the GO / PVA layer. Therefore, it is assumed that the bottom surface of the layer was not directly exposed to hydrochloric acid.

[0157] Preferably, the MEG battery cell was processed before the top electrode was applied to the GO / PVA layer. Thus, the first electrode was applied to the GO / PVA layer, and the first electrode and GO / PVA sample was processed. In this example, the sample was processed with only a single electrode attached.

[0158] The benefit of applying the second electrode to the functional layer after applying the acid treatment is that the surface of the functional layer is not covered by the electrode during the treatment. This means that the surface area of ​​the membrane that the acid comes into contact with is not reduced. Another benefit of applying the second electrode after applying the acid treatment is that the acid will not damage the second electrode.

[0159] In other systems, the acid treatment is applied after the second electrode is applied to the functional layer.

[0160] The method steps include preparing a GO / PVA mixture, depositing the GO / PVA mixture on an electrode to form a GO / PVA layer, applying an acid treatment, and applying a second electrode to the GO / PVA layer.

[0161] As discussed above, in other embodiments, the GO / PVA solution can be mixed with acid before application to the substrate. In this case, the GO / PVA mixture is mixed with acid. The GO / PVA mixture can be an ink. This solution is then deposited onto a conductive substrate after acid treatment.

[0162] In other exemplary devices, multiple layers of solution may be deposited. A first layer is deposited on a conductive substrate. After the layer dries, another layer is deposited on top of the first layer. After this other layer dries, additional layers may be deposited. Depending on the electrical properties required, each layer may contain the same or different solutions. For example, a first layer may contain a solution that has not been mixed with acid. Another layer may be deposited on the first layer containing a solution mixed with an acid having a specific concentration (e.g., 1%). Another layer may contain a solution mixed with various concentrations of acid. The multiple layers together form a functional layer.

[0163] An alternative device uses an alternative acid treatment technique, in which the MEG battery cells are treated with acid vapor. The acid vapor technique can be used in place of the acid soak technique described above. A variety of vapor treatments can be used.

[0164] In an exemplary device, a functional layer 310 (e.g., a GO / PVA layer) is suspended above an HCl solution 320, as shown in FIG. 3. HCl vapor 330 is emitted from the HCl solution 320 and contacts the GO / PVA layer 310. The acid vapor is absorbed into the surface of the GO / PVA layer. Various procedures can be used to generate vapor from the HCl solution; for example, a MEG material can be placed on top of the HCl solution and the container heated. For example, the HCl solution can be heated from room temperature to 100°C.

[0165] In Figure 3, no electrodes or substrates are shown. In another embodiment, the GO / PVA layer is deposited on an electrode before the acid treatment. The electrode can be a conductive substrate. The electrode can be deposited on a substrate, and the functional layer can be deposited on the electrode before the acid treatment.

[0166] Preferably, the MEG battery cell and acid are contained in a sealed box to prevent escape of HCl vapor.

[0167] Preferably, the HCl solution has a concentration of 32% by weight. HCl solutions of various concentrations can be used, such as 0.5%, 1%, 16%, and 32% by weight. The concentration can be in the range of 0.5% to 36% by weight. Preferably, the concentration is in the range of 20% to 36% by weight. Most preferably, the concentration is in the range of 30% to 36% by weight.

[0168] In the exemplary treatment, the exposure time is 1 hour. Longer or shorter treatment times can be used to vary the exposure time of the MEG battery cells to the HCl vapor.

[0169] After exposure to HCl vapor, the MEG battery cell is dried, for example, the battery cell can be placed in an oven for drying.

[0170] The advantages of the vapor treatment compared to the immersion technique include the fact that liquids, especially water molecules, from the HCl solution are less likely to penetrate into the MEG battery cell. Water molecules that penetrate into the battery cell will evaporate during drying, creating cracks in the GO / PVA composite layer, damaging the battery cell and reducing its electrical performance.

[0171] Another advantage of steam treatment includes reduced drying time compared to immersion of the battery cells in an HCl solution.

[0172] Other acids can be used to treat the functional layer. HNO3 (nitric acid) can be used. Nitric acid is typically available at 0.1 to 98% by weight. Sulfuric acid can also be used for the acid treatment. Sulfuric acid is typically available at 0.1 to 98% by weight.

[0173] Description: In a first system, the functional layer of the water-powered battery cell includes graphene oxide having a ratio of C=O bonds to C=C bonds greater than 1:9. The atomic ratio of C=O bonds to C=C bonds can be greater than 1:8, or greater than 1:7, or greater than 1:6, or greater than 1:5. The ratio of C=O bonds to C=C bonds can be less than 1:1.

[0174] C=O is a double bond between an oxygen atom and a carbon atom. CC is a single bond between a carbon atom and another carbon atom.

[0175] The functional layer is composed of graphene oxide and a polymer binder selected to bond to the conductive substrate. The polymer binder can be one or more of PVA, PVB, PMMA, or PVP. The conductive substrate forming the electrode can be attached to another substrate.

[0176] In some devices, the graphene oxide and polymer binder are a substantially homogeneous mixture of graphene oxide and polymer binder in a range of 100:1 to 2:1. In some devices, the functional layer comprises a processed graphene oxide having a layer spacing greater than the layer spacing of the graphene oxide from which the processed graphene oxide is made. In some devices, the processed graphene oxide has a ratio of C=O bonds to C-C bonds greater than 1:9. The ratio of C=O bonds to C-C bonds can be greater than 1:8, or greater than 1:7, or greater than 1:6, or greater than 1:5. The ratio of C=O bonds to C-C bonds can be less than 1:1. In some devices, the layer spacing of the processed graphene oxide is ≧0.799 nm.

[0177] The treated graphene oxide consists of graphene oxide and a polymer binder selected to bond it to a conductive substrate, which can be one or more of PVA, PVB, PMMA, or PVP.

[0178] The layer spacing of the treated graphene oxide can be ≧1.00 nm or ≧1.10 nm.

[0179] The functional layer may include multiple sublayers, at least one of the sublayers having a first ratio of C=O to C-C bonds and at least one of the other sublayers having a second ratio of C=O to C-C bonds, the first ratio being higher than the second ratio. In some devices, each sublayer has a different ratio of C=O to C-C bonds, and the sublayers are arranged to define a gradient in the ratio of C=O to C-C bonds through the functional layer.

[0180] In another system, a moisture-generating cell includes (a) a first electrode and a second electrode, and (b) a functional layer according to any one of the other aspects, wherein the functional layer is disposed between the first electrode and the second electrode and is electrically connected to the first electrode and the second electrode.

[0181] The first electrode may be porous to moisture, and the second electrode may be moisture-proof. The second electrode may include at least one of FTO, ITO, carbon nanotubes, MXene, graphene, carbon black, or a metal. The first electrode may allow moisture to penetrate through the first electrode and into the functional layer. The moisture includes HO molecules. The HO molecules may exist in liquid water or water vapor. The HO molecules may exist simultaneously in liquid water and water vapor.

[0182] The first electrode may comprise zinc, nickel, aluminum, magnesium, or other metals. Preferably, the first electrode may be a silver nanowire. The first electrode may be partially covered with silver particles (e.g., from a silver paste).

[0183] Preferably, to create a work function gradient between the first electrode, the functional layer and the second electrode, the work function of one of the first electrode or the second electrode is higher than the work function of the functional layer, and the work function of the other of the first electrode or the second electrode is lower than the work function of the functional layer.

[0184] A method for fabricating a functional layer of a water battery cell includes the steps of (a) fabricating a graphene oxide mixture, and b) exposing the mixture to an acid treatment.

[0185] In another method, a method for fabricating a functional layer of a water battery cell includes the steps of (a) forming a mixture of graphene oxide and a polymer binder, and (b) exposing the mixture to an acid treatment.

[0186] In the method, the acid treatment includes applying at least one of hydrochloric acid, nitric acid, or sulfuric acid to the mixture. The acid treatment can be a liquid treatment or a vapor treatment. In the method, creating the mixture includes mixing a solution of graphene oxide with a solution of a polymer binder. In the method, exposing the mixture to the acid treatment includes mixing a liquid acid into the mixture.

[0187] In the method, the mixture is a printable solution and the acid treatment involves mixing an acid with the printable solution prior to printing the functional layer onto the substrate. The method can include applying the acid treatment after the mixture is applied to the substrate.

[0188] In the method, the acid used in the acid treatment has a concentration in the range of 0.1 to 98% by weight. The acid used in the acid treatment can have a concentration in the range of 1 to 30% to 98% by weight. The method can include creating multiple mixtures, each containing a carbon-based material and a polymer binder, then exposing each mixture to a different acid treatment such that each mixture has a different ratio of C=O bonds to C-C bonds, and then stacking the various mixtures to form a functional layer comprising a series of sublayers, the mixtures being stacked in order of the ratio of C=O bonds to C-C bonds. Preferably, the carbon-based material is graphene oxide.

[0189] In the method, the step of preparing a mixture of graphene oxide and a polymer binder includes dissolving water-soluble graphene oxide in water to form a graphene oxide solution, dissolving a water-soluble polymer binder in water to form a polymer binder solution, and mixing the graphene oxide solution and the polymer binder solution.

[0190] In this method, the graphene oxide solution and the polymer binder solution are mixed in a 1:1 mass ratio. The graphene oxide solution may contain 10 to 30 mg / mL of graphene oxide. The graphene oxide solution contains 10 to 30 mg / mL of polymer binder.

[0191] Some systems provide a moisture-harvesting battery cell including a functional layer, a first electrode, and a second electrode, the moisture-harvesting battery cell configured to generate a hygroscopic gradient across at least one functional layer upon exposure to moisture. The first electrode and the second electrode may comprise different electrode materials. The first electrode and the second electrode may have different moisture permeability characteristics.

[0192] The first electrode may comprise at least one of FTO, ITO, carbon nanotubes, MXene, graphene, carbon nanoparticles, or carbon black. The second electrode may comprise silver nanowires / particles. The second electrode extends partially over the functional layer.

[0193] The first electrode may have moisture insulating properties to resist the ingress of moisture into the functional layer, and the second electrode may be porous to allow moisture penetration into the functional layer through the second electrode.

[0194] The functional layer of the water-powered battery cell may include at least one composite layer including a carbon-containing material and a binder, the binder may be water-soluble, and the binder may be polyvinyl alcohol (PVA).

[0195] The carbon-containing material can be graphene oxide.

[0196] The binder may facilitate bonding of the functional layer to at least one electrode. The binder may be electrically conductive. The binder may be electrically non-conductive.

[0197] The system may provide a moisture generator battery according to any preceding description, wherein the work function of one of the first electrode or the second electrode is higher than the work function of the composite layer, and the work function of the other of the first electrode or the second electrode is lower than the work function of the composite layer to create a work function gradient between the first electrode, the composite layer, and the second electrode.

[0198] The system may provide an electronic device powered by a moisture-powered cell including a functional layer according to any preceding description. Preferably, the electronic device is configured to have a surface that, in use, is positioned in contact with the subject's skin. Preferably, the electronic device is at least one of a sensor, a memory, or a wireless transceiver.

[0199] The system may provide a battery pack including a plurality of connected moisture generator battery cells including a functional layer according to another aspect, where the moisture generator battery cells may be stacked.

[0200] The system provides an electronic device powered by at least one moisture generator battery cell according to another aspect.

[0201] The water battery generator is configured to have one surface placed in intimate contact with the wearer's skin. The electronic device may include at least one of a sensor, a memory, and / or a wireless transceiver.

[0202] The method provides a method for manufacturing a moisture generator battery cell that includes depositing at least one layer of a mixture of a carbon-containing material and a binder onto a substrate, which is a first electrode, drying the layer of mixture, and applying a second electrode such that the layer is positioned between the electrodes.

[0203] The system provides a moisture generator battery cell including at least one composite layer including a carbon-containing material and a binder. The inclusion of the binder has the advantage of increasing the adhesion of the composite layer to a substrate within the moisture generator battery cell. This may improve the voltage stability of the moisture generator battery cell. The increased adhesion may also improve the current stability of the moisture generator battery cell. The substrate may be an electrode. The binder may be a water-soluble binder. Preferably, the binder is insoluble in acid.

[0204] The layer thickness can be gradually varied by varying the amount of carbon nanomaterial and water-soluble binder.

[0205] The carbon-containing material may be a carbon nanomaterial. The carbon-containing material may be an organic carbon material. Preferably, the carbon-containing material is graphene oxide (GO). Graphene oxide (GO) exhibits a high specific surface area, abundant oxygen-based groups, and good mechanical properties, as well as rapid moisture absorption and stable electrical output. GO can be modified with oxygen-based groups or internal structures to further improve its electrical output, providing tunable electrical properties. Graphene oxide has the advantage of being non-toxic.

[0206] Preferably, the binder is polyvinyl alcohol (PVA). PVA has abundant hydroxyl groups that allow moisture to be absorbed from the environment. The absorption of moisture from the environment induces a potential H + The PVA has good viscosity and also improves the attachment of the film to the substrate. The improved attachment produces a stable battery with a constant electrical output over multiple charging cycles. The battery cell provides good voltage retention. The PVA can modify the spacing between the graphene oxide layers. The spacing between the graphene oxide layers can be increased by the PVA. The increased spacing between the layers can increase the maximum voltage and current of the battery cell.

[0207] Preferably, the layer of carbon nanomaterial and water-soluble binder comprises a solution of carbon nanomaterial and a solution of water-soluble binder mixed in a 1:1 mass ratio. The mixture is an ink. The mixture is stable. The mixture can be solution processed. The mixture can be applied to a substrate using various techniques, including printing and coating techniques.

[0208] Preferably, the battery cell includes a first electrode and a second electrode, and at least one layer of carbon nanomaterial and water-soluble binder is located between the first electrode and the second electrode. The electrodes may be deposited by techniques including physical vapor deposition (e.g., sputtering) or by using solution processing techniques (e.g., printing). The first electrode and the second electrode may be composed of different materials, preferably conductive materials.

[0209] Preferably, at least one layer is mounted on a substrate. The substrate may include a first electrode. This allows the battery cell layers to be coated directly onto the bottom electrode, reducing the size of the battery cell. Preferably, the substrate is fluorine-doped tin oxide (FTO) glass. Other electrode substrates, including ITO-coated glass, may be used.

[0210] The substrate is a flexible substrate (e.g., carbon cloth). The use of a flexible substrate creates a flexible battery cell. Flexible battery cells offer opportunities for devices requiring flexibility (e.g., wearables, IoT devices, electronic skin patches).

[0211] The substrate can be stretchable, which allows the battery cell to be used for stretchable electronics.

[0212] Preferably, the second electrode covers a portion of the surface of the carbon layer comprising the material and binder. Preferably, the second electrode does not completely cover the surface of the layer. This allows at least a portion of the layer to be exposed and processable.

[0213] Preferably, at least one layer has at least one of the following properties: moisture stability, cyclable electrical properties (which allow the battery cell to be charged, discharged and recharged), adhesion to the substrate, adhesion to the electrode, solution processability (e.g., printing and coating techniques), deposition techniques (e.g., sputtering).

[0214] Preferably, at least one layer of the carbon-containing material and binder is treatable to modify the oxygen-based functional groups within the at least one layer. Modifying the oxygen-based functional groups may include modifying the oxygen-based functional groups by adding H + The ability of the layer to absorb ions can be increased. Preferably, the modification of the functional groups is an increase in the number of C=O bonds in at least one layer. The increase in the number of C=O bonds increases the number of H ions absorbed by at least one layer. + This may allow for an increase in the number of ions, which may increase the voltage and / or current produced by the battery cell.

[0215] The layer can be treated before being applied to the substrate. The carbon-containing material and binder are mixed with hydrochloric acid before being applied to the substrate. This can produce a generally homogeneous distribution of C=O bonds in the solution containing the carbon-containing material and binder. When deposited on the substrate, the layer of carbon containing material and binder contains a generally homogeneous distribution of C=O bonds.

[0216] Preferably, at least one layer is formed by depositing a composite carbon-containing material and binder onto a substrate followed by drying, and treating the layer to modify the oxygen-based functional groups within the layer is performed by treating the carbon-containing material and binder prior to depositing them on the substrate. Preferably, the carbon-containing material and binder are in the form of an ink.

[0217] The layer can be treated after being applied to a substrate. The layer has a first surface and a second surface, and the layer is treated on either the first surface or the second surface. The advantage of treating one surface of the layer is that the functional groups on the treated surface are altered. This can create a gradient of functional groups throughout the layer. The increase in the functional group gradient can be achieved by increasing the H +This increases the gradient of the ability to absorb ions. + When exposed to ions, this can increase the potential of the battery cell.

[0218] Preferably, the layer is treated by acidification. Preferably, the layer is treated by hydrochloric acid (HCl) acidification. HCl acidification increases the number of C=O bonds. HCl acidification reduces the resistivity of the layer.

[0219] A battery cell may include multiple layers of carbon-containing material and binder. Each layer may undergo different treatments. For example, some layers may be treated with acids having different concentrations. Different concentrations may produce different amounts of C=O bonds within the layers.

[0220] Preferably, at least one layer is a film. Preferably, the water absorption properties of the first electrode and the second electrode are different. Preferably, the layer is applied to the substrate by at least one of the following techniques: spin coating, spray coating, dip coating, drop coating, slot-die coating, nanoimplantation, inkjet printing, spray printing, intaglio printing, screen printing, flexography, offset printing, stamp printing, gravure printing, and aerosol jet printing.

[0221] The viscosity of the mixture can be controlled to facilitate various application processes. The concentration of GO can be varied, and organic materials such as PVA can be added to improve its application and adhesion on various substrates. The adhesion can also be controlled by adding different amounts of organic materials such as PVA.

[0222] Preferably, the concentration of hydrochloric acid is 0.1 to 32 wt %. Preferably, the concentration is 32 wt %. 32 wt % produces good electrical characteristics for the battery cell. Other concentrations of hydrochloric acid may be used. Hydrochloric acid having a concentration of 1% has been found to produce stable electrical characteristics over multiple charge and recharge cycles.

[0223] Some embodiments have a voltage output and a current output, at least one of which is increased upon processing at least one layer.

[0224] The interlayer spacing of at least one layer can be increased by processing, thereby increasing at least one of the voltage output and current output of the battery cell. GO nanosheets typically exhibit a multilayer structure, and the interlayer spacing can be tuned to achieve various physical and chemical properties.

[0225] In another system, a moisture generator battery cell includes at least one layer including a carbon-containing material, the layer being treated to modify oxygen-based functional groups within the layer. Modifying the oxygen-based functional groups includes H + The ability of the layer to release ions can be increased. Preferably, the modification of the functional groups is an increase in the number of C=O bonds in at least one layer. The increase in the number of C=O bonds increases the ability of the layer to release ions. + This may allow for an increase in the number of ions, which may increase the voltage and / or current produced by the battery cell.

[0226] Preferably, the layer is treated after being applied to the substrate. Preferably, at least one layer is formed by depositing a carbon-containing material on the substrate and then drying, and treating the layer to modify the oxygen-based functional groups in the layer is performed by treating the carbon-containing material before depositing it on the carbon-containing material substrate to form the layer. Preferably, the layer is an ink, and the layer is treated by mixing an acid with the ink before depositing the layer on the substrate. Preferably, the layer includes a binder.

[0227] In another system, a battery pack includes a plurality of moisture generator battery cells according to the first aspect or the second aspect. In some embodiments, the moisture generator battery cells are stacked. In some embodiments, the moisture generator battery cells are connected in series. In some embodiments, the moisture generator battery cells are connected in parallel. Some embodiments may include moisture generating battery cells including series and parallel electrical connections between the cells.

[0228] In another system, an electronic device is powered by one or more moisture generator battery cells of the first or second aspect. Preferably, the moisture generator battery cells are configured to have one surface placed in intimate contact with the wearer's skin. Preferably, the electronic device further includes at least one of a sensor, a memory, and / or a wireless communication component / module.

[0229] In another system, a method for manufacturing a moisture generator battery cell includes depositing at least one layer of a mixture of a carbon-containing material and a binder onto a substrate that is an electrode, drying the layer of the mixture, and applying another electrode such that the layer is positioned between the electrodes. A first electrode can be applied to the substrate.

[0230] Preferably, the second electrode is applied to a portion of the second surface of the layer. Preferably, the second electrode does not completely cover the surface of the layer. This allows at least a portion of the layer to be exposed and processable.

[0231] Preferably, the carbon nanomaterial is graphene oxide (GO). Preferably, the water-soluble binder is polyvinyl alcohol (PVA). Preferably, the solution is a mixed solution of GO and PVA in a 1:1 mass ratio.

[0232] Preferably, the method comprises a further step of treating the layers of carbon nanomaterial and water-soluble binder to increase the number of C=O bonds in at least one layer. Preferably, the layers are treated by acidification. Preferably, the acidification is with HCl.

[0233] The depositing method step is carried out by at least one of the following techniques: spin coating, spray coating, dip coating, drop coating, slot die coating, nanoimplant, inkjet printing, spray printing, intaglio printing, screen printing, flexographic printing, offset printing, stamp printing, gravure printing and aerosol jet.

[0234] Preferably, the moisture generator battery cell has a voltage output and a current output, and at least one of the voltage output and the current output is increased upon treating the at least one layer.

[0235] In this method, the first electrode is a material having similar mechanical properties to the composite layer. In this method, the first electrode includes a material having similar thermal expansion to the composite layer. In this method, the first electrode includes carbon nanotubes.

[0236] Preferably, the first electrode has at least one of the following properties: waterproofness, flexibility, and light weight. Its similar structure and expansion coefficient to GO provide excellent adhesion to the composite layer. Therefore, the electrical resistance of the connection is low, increasing electrical conductivity during operation.

[0237] Preferably, to create a work function gradient between the first electrode, the composite layer and the second electrode, the work function of one of the first electrode or the second electrode is higher than the work function of the composite layer and the work function of the other of the first electrode or the second electrode is lower than the work function of the composite layer.

[0238] In this method, the second electrode has a work function lower than that of the composite layer. In this method, the second electrode has a work function lower than that of the composite layer, and the composite layer has a work function lower than that of the first electrode.

[0239] In this method, the second electrode comprises a porous material. Preferably, the second electrode comprises a material that allows water penetration. Preferably, the second electrode comprises silver nanowires.

[0240] In this method, the second electrode comprises zinc.

[0241] Applications for moisture generator battery cells include power sources for thin film transistors, memory devices (e.g., RRAM, memristors), large area electronics, IoT devices, sensors, wearable devices, and electronic skin patches.

[0242] In a moisture generator battery cell, the first electrode has moisture insulating properties to resist the ingress of moisture into the layer.

[0243] In a moisture generator battery cell, the first electrode prevents moisture from entering the layer through the first electrode.

[0244] In the moisture generator battery cell, a first electrode substantially covers a first surface of the layer.

[0245] In the moisture generator battery cell, the first electrode may include a carbon-based conductive material, such as carbon nanotubes, graphene, or carbon black.

[0246] In a moisture generator battery cell, the electrodes are materials that have similar mechanical properties as the composite layers. In a moisture generator battery cell, the electrodes include materials that have similar thermal expansion properties as the composite layers.

[0247] In a moisture generator battery cell, the electrodes include carbon nanotubes.

[0248] Preferably, the electrode has at least one of the following properties: waterproof, flexible, and provides good adhesion at the interface with the composite layer, flexibility, and lightness. The similar structure and expansion coefficient of GO provide very good adhesion at the GO / carbon nanotube interface. Therefore, the electrical resistance of the connection is low, which increases the electrical conductivity during operation.

[0249] In the moisture generator battery, the second electrode contacts the second surface or layer. In the moisture generator battery, the second electrode has a work function lower than the work function of the composite layer. In the moisture generator battery, the second electrode has a work function lower than the work function of the composite layer, which has a work function lower than the first electrode. In the moisture generator battery, the second electrode comprises a porous material. Preferably, the second electrode comprises a material that allows water to pass through. Preferably, the second electrode comprises silver nanowires.

[0250] In a moisture generator battery, the second electrode comprises zinc.

[0251] Section 1: Samples and Results Section 1 below describes the first series of samples and results.

[0252] material GO powder was synthesized by oxidation of graphite powder according to the Hummers method. A 20 mg / mL GO solution was obtained by dispersing GO powder in distilled water by sonication for 30 min. A 20 mg / mL polyvinyl alcohol solution was obtained by dissolving PVA powder (molecular weight 13,000–23,000) in distilled water at 90 °C for 30 min.

[0253] Fabrication of MEG FTO glass is 2.5 x 2.5 cm 2 It was cut into pieces and used as the substrate / bottom electrode. Other conductive substrates can be used instead of the FTO coated glass (e.g., ITO coated glass or other conductive electrode materials).

[0254] The GO solution and the polyvinyl alcohol solution are mixed in a mass ratio of 1:1 by sonication. Other mixing mass ratios from 100:0 to 100:10 can be used.

[0255] This mixture is 1 x 1 cm 2It was dried directly onto FTO glass at 50 °C for 12 hours to form a GO / PVA film. Additional layers of this mixture can be applied to increase the thickness of the GO / PVA layer. Typically, additional layers are deposited after the previous layer has dried.

[0256] The remaining exposed area of ​​the FTO glass was covered with insulating tape and Ag paste was applied as the top electrode, a process that is described in more detail below with reference to Figure 12.

[0257] In an alternative embodiment, a conductive and flexible carbon cloth is used as the electrode substrate. The carbon cloth was immersed in the GO / PVA solution for 10 minutes and dried for 12 hours.

[0258] Figure 4(a) shows a schematic cross-sectional representation of the structure of an MEG battery cell. Figure 4(b) shows a photograph of the MEG battery cell after acid treatment. The GO / PVA layer is deposited on a conductive substrate, so that the bottom surface of the GO / PVA layer is in contact with the conductive substrate. In the example above, the conductive substrate is FTO-coated glass. A top electrode is applied to the top surface of the GO / PVA layer. In this example, the top electrode is Ag paste.

[0259] Figure 12(a) illustrates the process of applying a second (top) electrode onto the GO / PVA layer of a battery cell. Figure 12(a) shows a top view of a sample in which a GO / PVA film was deposited on an FTO glass substrate and acidified. In the example of Figure 12(a), the GO / PVA film partially covers the FTO glass substrate. In other embodiments, the film may completely cover the substrate. In other embodiments, the film may cover other portions of the substrate.

[0260] An insulator is applied over the exposed portion of the substrate. A top electrode is then evaporated onto the top layer of the film. The top electrode is insulated from the bottom electrode to avoid shorting the battery cell. In the example of Figure 12, silver (Ag) paste is used for the top electrode.

[0261] The remaining exposed area of ​​the FTO glass was covered with insulating tape and coated with Ag paste as the top electrode, a process that is described in more detail below with reference to Figure 12.

[0262] Acid treatment of MEG To treat the MEG, the MEG battery cell was immersed in hydrochloric acid for 10 minutes. The MEG battery cell was then rinsed with distilled water for 10 minutes. The MEG was then dried at 50°C for 12 hours for electrical measurements. Various samples were immersed in hydrochloric acid with various concentrations, and then the electrical properties of each sample were tested. Hydrochloric acid with concentrations of 0.5 wt%, 1 wt%, 16 wt%, and 32 wt% was used.

[0263] It is assumed that the bottom surface of the GO / PVA layer was attached to the conductive substrate, and therefore the bottom surface of the layer was not directly exposed to hydrochloric acid.

[0264] The advantage of treating the MEG battery cell before applying the top electrode to the membrane is that after applying the top electrode to the membrane, the surface area of ​​the membrane attached to the top electrode is protected from the acid treatment. This means that the surface area of ​​the membrane that the acid can contact and modify oxygen groups on is reduced. The acid no longer comes into contact with that portion of the surface connected to the top electrode.

[0265] Electrical Testing For example, the top and bottom electrodes of the MEG were connected to a precision source / measurement unit (Figure 20(b)) for electrical output measurement. In this example, a Keysight B2902A measurement unit was used.

[0266] Electrical measurements were performed on the battery cells in environments with various relative humidity (RH). Wet N2 and dry N2 were used to control the RH in the sample chamber. For electrical retention measurements, humidity was input by wet N2 to increase RH (up to 75% RH) and electrical output until the maximum value was reached and stopped for retention measurements. For electrical cycling measurements, humidity was input by wet N2 to increase RH and electrical output until the maximum value was reached, and then removed by dry N2 (up to 0% RH) to decrease RH and electrical output until the minimum value was reached. The voltage and current outputs of multiple battery cells were measured by connecting the battery cells in series and parallel. The voltage retention measurements of batteries washed in 32% HCl at 1%, 25%, and 55% RH are shown in Figure 5. This shows that as the relative humidity increases, the voltage output by the MEG battery cell increases.

[0267] Results and Discussion Figure 4(a) shows a schematic diagram of the MEG, a relatively simple structure for power generation. The device photograph in Figure 4(b) shows the uniform surface and good attachment of the GO / PVA film on the FTO glass, compared to the GO film in Figure 13(a), which shows weak attachment and wrinkles. The morphology of the GO / PVA film with a thickness of 15.53 μm after HCl acidification (Figure 4(d)) shows a smooth surface and dense layer structure due to the addition of PVA, which is similar to the morphology of the GO / PVA film before acid washing (Figure 4(c)). The intact and uniform morphology of the GO / PVA film contributes to stable electrical output during long-term use.

[0268] The voltage output of the GO / PVA film acidified with 32 wt% HCl was recorded at various RH (Figure 5). The maximum voltages of the MEG are 0.01 V (relative humidity (RH) = 1%), 0.25 V (RH = 25%), and 0.61 V (RH = 55%), respectively. Therefore, the MEG exhibits near zero voltage output at RH = 1% and increased voltage output at higher RH, demonstrating that RH is closely related to power generation. Higher RH corresponds to more absorbed water and larger H in the MEG. +contributes to the gradient, leading to a higher voltage output.

[0269] The voltage output of GO / PVA membranes acidified by HCl solutions at various concentrations is shown in Figure 6(b). The maximum voltage increases with thickness (0.74 V, 0.8 V, and 0.85 V for membranes with thicknesses of 6.21 μm, 12.23 μm, and 15.53 μm, respectively), and does not show any clear increase for membranes thicker than 15.53 μm (Figure 13). Thinner membranes facilitate water permeation and promote H2O2 transport throughout the GO / PVA layer. + This reduces the gradient, leading to a lower voltage output. 2 , 1.0×1.0cm 2 , 1.5×1.5cm 2 ) exhibited similar maximum voltage values ​​(Figure 14), demonstrating that the voltage is related to the charge ion gradient rather than the membrane area and that high voltages can be generated by very small areas.

[0270] The voltage retention can be used to evaluate the long-term performance of the device (Figure 6(a)). The voltage of the GO / PVA film increases after exposing the film to humidity and does not show any obvious degradation for over 2 hours (RH = 75%). These results indicate better electrical performance in generating a stable and sustained voltage output compared to that of other GO-based MEGs.

[0271] The maximum voltage of GO / PVA increases with HCl concentration, increasing gradually when the HCl concentration is higher than 16%. The maximum voltage of the GO / PVA film without HCl acidification is approximately 0.49 V, which is almost the same as that of the GO film without HCl acidification (Figure 6(b)). The maximum voltage of the GO / PVA film acidified with 32% HCl is 0.85 V, which is much higher than that of the film without HCl acidification (0.49 V). Therefore, the voltage output of the acidified GO / PVA film is closely related to the HCl concentration. HCl acidification can be employed as a facile and effective method to greatly improve the voltage output of the GO / PVA film.

[0272] The voltage cycling of the GO / PVA film was also studied to evaluate the stability of the MEG (Figure 6(c)). The voltage cycling of the GO film (Figure 12(b)) is not as stable as that of the GO / PVA film, possibly because the PVA provides a stable structure and good attachment of the film to the substrate. The GO / PVA film exhibits similar voltage output within each cycle and the same maximum voltage output, demonstrating that the GO / PVA film can generate a stable voltage output.

[0273] Figure 6(d) shows the short-circuit current (I sc ), which increases with the concentration of HCl (I for membranes acidified with 32%, 16%, 1%, 0.5%, and 0% HCl, respectively). sc The maximum current of the GO / PVA membrane acidified with 32% HCl was approximately 9.28 μA, which was significantly higher than the maximum current of the membrane without HCl acidification (19.71 nA). This result indicates that the H + This is due to the decrease in resistance after the introduction of HCl. The GO / PVA film is presumed to be non-conductive due to the large amount of functional groups attached to the carbon surface. However, the resistivity of the GO / PVA film after acidification with 32% HCl decreased to 0.9–1.2 MΩ, which is beneficial for better electrical performance.

[0274] The diffraction peak of the GO / PVA film shows a lower angle than that of the GO film and shifts to a higher angle after increasing the HCl concentration (Fig. 7(a)). The layer spacing of the GO / PVA film can be calculated by the diffraction angle (Fig. 7(b)).

[0275] The GO / PVA film exhibits a wider layer spacing than the GO film, with the spacing being 0.77 nm for the GO film, 1.26 nm for the GO / PVA film, 1.19 nm for the GO / PVA (1% HCl) film, and 1.10 nm for the GO / PVA (32% HCl) film. The PVA polymer molecules can enter the interlayer of GO, and the carboxyl groups from GO can react with the hydroxyl groups in the crosslinks. The crosslinking between GO and PVA crosslinks adjacent GO sheets, enlarging the layer spacing. This may explain why the GO / PVA film exhibits a wider layer spacing than the GO film.

[0276] Furthermore, the spacing of the GO / PVA film decreases after HCl acidification. The shortened spacing of the GO / PVA film acidified by HCl is due to the + The charge ions (H) induced by HCl acidification may be absorbed by oxygen-based groups and inhibit the cross-linking of GO with PVA. + ), which may result from the FIR spectra of the GO / PVA and GO / PVA(32%HCl) films are almost identical to that of the GO film (Fig. 15(a)). Due to the addition of PVA, the Raman spectra of the GO / PVA and GO / PVA(32%HCl) films are flatter than that of the GO film (Fig. 15(b)). This demonstrates that PVA is not washed away by distilled water or HCl in our fabrication.

[0277] Oxygen-based functional groups are closely related to moisture absorption and power generation, which can be characterized by the C1s region in XPS. To investigate the effect of HCl acidification on the change in functional groups with respect to increased voltage output, GO / PVA films with and without HCl acidification are analyzed in Figure 8. C1s peaks for GO / PVA (0% HCl) with binding energies of 284.8 eV, 286.2 eV, 287.0 eV, and 289.2 eV represent C-C (45.29 at.%), C-O (19.18 at.%), C=O (4.67 at.%), and C-C=O (4.84 at.%). C1s peaks in GO / PVA (32% HCl), with bond energies of 284.8 eV, 285.9 eV, 287.0 eV, and 289.0 eV, representing C-C (28.30 at.%), C-O (14.26 at.%), C=O (20.75 at.%), and C-C=O (4.49 at.%). Therefore, the ratio of C-O bonds decreases after HCl acidification, while the ratio of C=O bonds increases after HCl acidification. The C / O ratio in the GO / PVA film decreases from 2.96 to 2.12 after 32% HCl acidification. This demonstrates that acid oxidation occurs during acid washing. In HCl acidification, epoxy groups can be arranged in a single row, leading to the destruction of C-C bonds. Epoxy chains are oxidized to epoxy pairs and tend to convert to carbonyl pairs because the carbonyl group is more stable in this state. The more polar C=O bonds are oxidized to H. + It is stronger than CO at attracting CO to form hydrogen bonds. Therefore, a higher voltage output allows for more H + This can be attributed to the more C=O bonds that can be absorbed.

[0278] The oxygen-based groups in the GO / PVA films washed with acetic acid and NaOH were also investigated in Figures 16(c) and 16(d), respectively. The GO / PVA films washed with acetic acid exhibited CC (35.96 at.%), CO (22.28 at.%), C=O (1.27 at.%), and OC=O (6.13 at.%), while the GO / PVA films washed with NaOH exhibited CC (37.86 at.%), CO (25.24 at.%), C=O (2.74 at.%), and OC=O (2.47 at.%). The maximum voltages of the GO / PVA films washed with acetic acid and NaOH were 0.34 V and 0.22 V, respectively, which were relatively lower than those of the film acidified with HCl due to the lower proportion of C=O in the GO / PVA films washed with acetic acid and NaOH. Therefore, the proportion of C=O is related to the voltage output of the GO / PVA films. Furthermore, the higher C / O ratio in the acidified film contributes to the lower resistivity of the GO / PVA film, thereby significantly enhancing the current output (from 19.71 nA to 9.28 μA per unit after acidification). Furthermore, the CO and OC=O peaks shift slightly to lower binding energies after HCl acidification.

[0279] GO / PVAMEG battery cells can be directly connected in series or parallel to improve voltage or current output. The schematic diagrams in Figures 11(b) and 11(c) show four battery cells connected in series for voltage measurements and four battery cells connected in parallel for current measurements, respectively.

[0280] The voltage of 2 × 4 units in series shows good retention for more than 2 hours without any obvious drop (Fig. 9(a)). The maximum voltage of the unit is 0.85 V, 1.70 V, and 3.38 V for 1 unit, 2 units, and 4 units, respectively (Fig. 9(c)). The parallel units also show enhanced current output due to the greater number of units involved (Fig. 9(b)). The maximum current of the unit is 9.28 V, 18.16 V, and 40.69 V for 1 unit, 2 units, and 4 units, respectively. Thus, the voltage and current of the MEG battery cell increase linearly with the power output of a single unit. This demonstrates the potential application in generating high electrical power output with a simple assembly of units (battery cells).

[0281] GO / PVA films by 32% HCl acidification were also fabricated on carbon cloth for flexible device applications. 2 ) can reach 0.506 V at room humidity (RH=45%) (Figure 10(b)).

[0282] The GO / PVA membrane is mounted on glass bottles with various radii to investigate the effect of membrane curvature on the voltage output of the GO / PVA membrane. The voltage of the membranes with various curvatures increases to a maximum value after 150–300 s. The maximum voltage is measured at 0 cm. -1 , 0.5cm -1 , 1.0cm -1 The voltage output of the acidified GO / PVA film on carbon cloth shows stable voltage output on surfaces with various curvatures, demonstrating its great potential in the fabrication of flexible devices.

[0283] Furthermore, device arrays can be easily realized by dividing the film into small pieces to provide practical devices (Fig. 10(e)). An acidified GO / PVA film was first fabricated on FTO glass by the above method, and then the film was divided into 20 parallel cells, and Ag paste was applied as the top electrode (Fig. 17(a)). A unit with 20 parallel cells can be connected in series with other units to improve electrical output (Fig. 17(b)). The array (2 in series × 20 in parallel) can provide enough power to power a computer (Fig. 10(f)).

[0284] In another example, five battery cells were connected in series to test electrical output, an example of which is now described below with reference to Figures 18-21.

[0285] For a single cell, a mixed solution of GO and PVA (mass ratio = 1:1) was used to prepare a GO / PVA film (thickness ≈ 15 μm, area ≈ 1 × 1 cm). 2 The film was dried at 50 °C for 12 h on FTO glass to form a film (area ≈ 0.1 × 0.5 cm), followed by acidification with 32% HCl (by immersing the film in the HCl solution for 10 min). It was then washed with distilled water for 10 min and dried at 50 °C for 5 h. The top Ag electrode was prepared by applying the Ag paste to a film (area ≈ 0.1 × 0.5 cm). 2 ) and dried at 50° C. for 10 minutes (FIG. 18).

[0286] The relative humidity (RH) in the sample chamber was controlled by inputting wet N2 and dry N2 (Figure 19(a)). The electrical output was recorded with a Keysight B2902A precision source / measurement unit (Figure 19(b)). The connection of five cells in series is shown in Figure 20. For the retention force measurements, humidity was input by wet N2 to increase the RH (up to 75% RH) and electrical output until a maximum value was reached, and then stopped for the retention force measurement. For the voltage / current cycle measurements, humidity was input by wet N2 to increase the RH and electrical output until a maximum value was reached. Then, humidity was eliminated by dry N2 (within 0% RH) to reduce the RH and electrical output until a minimum value was reached.

[0287] Tabulation of all experimental results and data

[0288] [Table 1]

[0289] Calculation of the average time for the 5-cell series voltage to return to 80% of its peak value when humidity levels are reintroduced for the humidity cycle experiment. The average time for the 5 cells to return to 80% peak value is 17.75 seconds.

[0290] Based on Figure 21(a), a voltage discharge curve for a single MEG battery cell was generated through connection of a single MEG battery cell with a resistive load (2000 kOhm) at RH=75%. The MEG battery cell was observed discharging for over 7000 s. The voltage retention of the 5-connected MEG battery cell was measured for over 5.3 hours. The voltage output was stable, showing >4.1 V after 5.3 hours in Figure 21(b). Voltage and current cycling was tested for the 5-connected MEG battery cell (Figures 21(c) and 21(d)), with the voltage peaking back above 4 V and the current peaking at approximately 58 uA.

[0291] conclusion We fabricated an MEG battery cell using a GO / PVA film treated with HCl, which can respond to moisture and generate electricity without any other stimuli. By adding PVA, the GO / PVA film exhibits better attachment to the substrate and more stable electrical output. After 32% HCl acidification, a voltage increase from 0.49 V to 0.85 V and a current increase from 9.28 nA to 19.71 μA were recorded at RH = 75%, providing a convenient approach to significantly improve electrical performance. This voltage could achieve retention for more than 2 hours without any apparent degradation, demonstrating its stable electrical output for long-term applications. A voltage of approximately 4.1 V or a peak current of 58 μA was easily generated by a simple assembly of five MEG battery cell units connected in series or parallel, demonstrating its great potential in powering commercial devices. Furthermore, GO / PVA films were also fabricated on soft and flexible carbon cloth, generating a voltage higher than 0.8 V for more than 2 hours. This demonstrates that the GO / PVA film is applicable to the fabrication of flexible devices.

[0292] We present an acidified membrane of GO and polyvinyl alcohol (PVA) for use in MEG battery cells. PVA, with its abundant hydroxyl groups and good adhesion, not only absorbs moisture from the environment but also improves the attachment of the membrane to the substrate, leading to steady electrical output. Furthermore, the voltage and current output of the GO / PVA membrane are greatly improved due to the optimization of functional groups after acidification, providing a simple approach to fabricating MEG with high and steady electrical output. A single MEG battery cell unit can generate a high voltage of 0.85 V and a significant current of 9.28 μA at 75% relative humidity. The MEG battery cell exhibits voltage retention for more than 2 hours without any significant voltage drop. MEG battery cells can also be connected in series and / or in parallel to further improve its electrical output. The voltage of five MEG battery cells in series reaches a maximum of 4.1 V, which is high enough to power several practical electronic devices. Therefore, this MEG battery cell provides a feasible approach to design energy harvesting from abundant moisture when powering practical devices.

[0293] Due to the large demand for power sources, harvesting energy from moisture has attracted growing interest in practical applications due to its abundant source. In this paper, the electrical performance of GO / PVA films fabricated by drop casting and subsequent HCl acidification was investigated to enhance their electrical output. The as-prepared GO / PVA film acidified with 32% HCl could generate an excellent voltage of 0.85 V and a high current of 9.28 μA at 75% relative humidity, which could be further improved by simple assembly (4.1 V or 58 μA (peak) for five units in series or parallel). Electrical output was also achieved on flexible carbon cloth. This presents a simple and effective approach to generate enhanced electrical performance for energy supply in flexible electronics.

[0294] Various embodiments of the battery cells described above provide self-charging batteries that provide high current and voltage outputs in humid environments. Such battery cells have applications in many electronic devices. In particular, the high current and voltage outputs and stable output of the MEG battery cells make some embodiments suitable power sources for many wearable technologies, allowing the battery cells to be placed in high humidity environments (e.g., in contact with human skin, which has humidity levels of approximately 80% to 100%). These high humidity environments require H to maintain the charge on the battery cells. + The MEG battery cell provides ions. Suitable applications include health wearable devices (including various body sensors and electronic skin patches). The voltage and current levels produced by the MEG battery cell allow Internet of Things (IoT) devices (which may include sensors and / or wireless communication modules (e.g., Bluetooth wireless transceivers)) to be powered.

[0295] Section 2: Samples and Results Section 2 below describes the second series of samples and results.

[0296] Acidified GO films were incorporated with a small amount of polyvinyl alcohol (PVA) for MEG applications. PVA, with its hydroxyl groups and good adhesive properties, not only absorbs moisture from the environment but also improves the attachment of the film to the substrate, leading to a stable device structure and steady-state electrical output. Most importantly, the electrical output of the GO / PVA film was greatly enhanced due to the optimization of functional groups and reduced film resistance after acidification, providing a facile approach to fabricate MEGs with high and steady-state electrical output. A single unit achieved a high voltage of 0.85 V and a current of 9.28 μA (92.8 μA cm) at 75% RH, among the highest reported electrical outputs of MEGs. 2 ) can generate an astonishing current 6,12 The MEGs exhibit good voltage retention for over 2 hours without any obvious degradation. The MEGs can also be connected in series or parallel to further improve their electrical output. The voltage and current of four MEG units reach a maximum of 3.38 V and 40.49 μA, respectively (high enough to power some practical electronic devices). Therefore, this paper provides a feasible approach to modifying functional groups in GO and generating enhanced electrical output for powering practical electronic devices.

[0297] Section 2 Sample Methods material Hydrochloric acid (HCl), acetic acid, sodium hydroxide (NaOH), polyvinyl alcohol (PVA) powder (molecular weight 13,000–23,000), Ag paste, and silver nitrate were purchased from Sigma. GO powder was synthesized by oxidation of graphite powder according to the Hummers method. 33 A 20 mg / mL GO dispersion was obtained by dispersing GO powder in distilled water by sonication for 30 min. A 20 mg / mL PVA solution was obtained by dissolving PVA powder in distilled water by stirring at 90 °C for 30 min.

[0298] Fabrication of MEG Fluorine-doped tin oxide (FTO) glass, 1.0 x 2.0 cm 2The FTO glass was then washed with ethanol and deionized water, followed by UV irradiation for 30 minutes. The GO dispersion solution and PVA solution were mixed in a 1:1 mass ratio (the maximum ratio required to achieve good attachment of the GO / PVA film onto the substrate) by sonication for 30 minutes, and then cut into 1.0 × 1.0 cm pieces to be used as the substrate / bottom electrode. 2 To form a GO / PVA film, it was directly dried on the FTO glass at 50°C for 12 hours. The edges of the GO / PVA film were covered with insulating tape to avoid short circuits, and Ag paste was printed on the film as the top electrode. For films fabricated on carbon cloth (substrate / bottom electrode), the carbon cloth was immersed in the above GO / PVA dispersion solution for 30 minutes and then dried at 50°C for 12 hours.

[0299] Chemical treatment of MEG For MEG acidification, MEG was immersed in HCl solutions with various concentrations for 10 minutes. Then, MEG was washed with distilled water until no chloride ions were detected with silver nitrate solution. Next, MEG was dried at 50°C for 24 hours for electrical measurements and powering electronic devices. For MEG washed with other reagents, MEG was immersed in acetic acid or NaOH solution for 10 minutes and then washed with distilled water until pH = 7.

[0300] Electrical measurements The MEG electrodes were directly connected to a Keysight B2902A precision source / measurement unit for electrical output measurements. Wet and dry N2 were used to control the RH in the sample chamber. Compressed N2 was used as dry N2 to reduce the RH in the sample chamber. Wet N2 was obtained by flowing dry N2 into deionized water to increase the RH in the sample chamber. For electrical output retention measurements, humidity was input by wet N2 to increase the RH and electrical output until the electrical measurement was terminated. For electrical output cycling measurements, humidity was input by wet N2 to increase the RH and electrical output until a maximum value was reached, and then removed by dry N2 to reduce the RH and electrical output. The voltage and current outputs of multiple units were measured by connecting the units in series and in parallel, respectively.

[0301] MEG electrical output Moisture from water evaporation is an abundant and sustainable resource on Earth that can be harvested by the MEG and incorporated into a self-powered system (Figure 22(a)). Figure 22(b) shows the schematic structure of the MEG, where a carbon-based material serves as the functional layer, and Ag paste and fluorine-doped tin oxide (FTO) glass serve as the top and bottom electrodes, respectively. Moisture from the environment is absorbed by the hydrophilic functional layer, promoting charge separation between the top and bottom electrodes to realize power generation. To optimize the functional layer, three types of materials (GO, PVA, and GO / PVA) were used to fabricate the device, which was tested at RH = 75%. As shown in Figures 22(c) to 22(e), the maximum voltage (V maxThe voltage outputs are 0.48 V for GO, 0.26 mV for PVA, and 0.50 V for GO / PVA, respectively. Clearly, the GO film outperforms the PVA film in generating high voltage outputs, although clear fluctuations in voltage were observed (Fig. 22(c)). During electrical measurements, the GO film was not securely attached to the FTO glass due to poor interfacial adhesion, reducing the stability and reproducibility of the voltage outputs. Separately, GO / PVA exhibited high and stable voltage outputs because PVA could function as a binder to greatly improve interfacial adhesion (Fig. 22(e)). Therefore, GO / PVA is selected as the functional layer for fabricating MEGs with high and stable electrical outputs.

[0302] The proton concentration gradient across the functional layer is essential for proton migration and therefore governs the voltage output. Generally, a higher concentration gradient can generate a higher voltage, which can be obtained from a higher RH and an enhanced protonation ability of the functional layer. Gao et al. reported that the number of surface protons increases with acidification, thus leading to improved electrical output of paper-based MEG. 13 Here, we used hydrochloric acid (HCl) solutions with various concentrations, including 32.0%, 16.0%, 1.0%, 0.5%, and 0.0%, to treat the GO / PVA membrane and tune the functional group density. As shown in Figures 23(a) and 23(b), the corresponding V max are 0.85 V, 0.82 V, 0.69 V, 0.61 V, and 0.50 V, respectively, indicating good retention for more than 2 hours. Specifically, the V maxis 0.85 V (among the highest reported voltages for a single MEG). Clearly, acidification can greatly improve the voltage output, as it can enhance the protonation capacity and lead to a larger protonation gradient. The electrical output of MEG acidified with 32.0% HCl at an external sweep voltage was investigated. The current output of MEG at a positive external voltage is significantly higher than that of MEG at a negative external voltage. This results from the difference in MEG resistance, which is 0.02–0.26 MΩ at a positive external voltage and 0.35–2.19 MΩ at a negative external voltage. This demonstrates that the acidified GO / PVA membrane generates a large protonation gradient between the top and bottom surfaces. After immersing the membranes (acidified with 0.0% and 32.0% HCl, respectively) in 1 mL of distilled water for 10 min, the pH of the various water-immersed membranes shows the same value. Therefore, the ionized H from the HCl solution + Instead, dissociation of functional groups leads to a protonation gradient.

[0303] To rule out other variables, the surface morphology was characterized for GO / PVA films with 0.0% and 32.0% HCl acidification by using scanning electron microscopy (SEM). Figure 32 shows that the morphology of both films does not demonstrate any significant changes. Meanwhile, cross-sectional SEM images show that both the film microstructure and thickness remain unchanged. Furthermore, the voltage output was measured for 0.5 × 0.5, 1.0 × 1.0, and 1.5 × 1.5 cm films. 2 The voltage was measured on devices with various membrane areas, and showed that the voltage remained almost the same. In addition, the V of the PVA membrane acidified with 32.0% HCl was max is 0.49 V, which is much lower than that of the GO / PVA film acidified with 32.0% HCl. Therefore, it is clear that acidified GO, but not acidified PVA, has a higher voltage output (V max = 0.85 V). Therefore, these results rule out the influence of membrane morphology, membrane area, and PVA on the high-voltage output of the acidified GO / PVA membrane.

[0304] To further confirm that the proton concentration across the membrane induced the potential, various RH values ​​of 1%, 25%, 55%, and 75% were applied on the top surface of the device. As shown in Figure 23(c), the corresponding V max are 0.02 V, 0.22 V, 0.60 V, and 0.85 V. Furthermore, the V of the acidified membranes with top / bottom and top electrode / top electrode at RH=75% max are 0.85 V and 0.02 V, respectively. The MEG with two top electrodes exhibits a nearly zero voltage output due to the negligible protonation gradient between the two top sides of the GO / PVA membrane. Therefore, the protonation gradient is closely related to the voltage output of the MEG. In addition, we investigated the effect of membrane thickness on the voltage output of a GO / PVA membrane acidified with 32.0% HCl. GO / PVA membranes with various thicknesses of 23.73 μm, 15.33 μm, 12.23 μm, and 6.21 μm were able to generate 0.85 V, 0.85 V, 0.80 V, and 0.75 V, respectively. MEGs with thinner GO / PVA membranes promote migration toward the inner layer, leading to a lower gradient of absorbed water between the top and bottom sides, reducing the protonation gradient and voltage output. The above results clearly demonstrate that RH and functional group density within the GO / PVA device simultaneously determine the protonation gradient and voltage output.

[0305] It should be noted that RH is usually an uncontrollable condition for MEGs to generate high voltages in practical applications. Therefore, optimizing the functional group density of the functional layer is particularly important for obtaining the desired voltage and current outputs. As demonstrated in Figure 23(a), HCl treatment can tune the functional group density, thereby generating various voltage outputs. Meanwhile, cycling stability is another key parameter for judging MEG performance. Moisture was transported to the top surface of the device by N2 gas to generate electrical output. When the moisture was extracted by dry N2, the electrical output dropped sharply. Electrochemical impedance spectroscopy (EIS) of GO / PVA with and without HCl acidification was performed at room humidity to analyze the conductivity of various MEGs (Figure 23(d)). GO / PVA with HCl acidification showed a lower resistance than GO / PVA without HCl acidification, which stems from the more mobile ions in the acidified GO / PVA, which is better for achieving high current outputs. Specifically, the maximum current output of the MEG was 19.71 nA (197.1 nA cm) after 32.0% HCl acidification. 2 ) to 9.28 μA (92.8 μA cm 2 ), indicating a significant improvement upon acidification (Fig. 23(e)). Fig. 23(f) shows the cyclic voltage output of MEG acidified with various HCl concentrations. Clearly, with increasing HCl concentration, the device produces a gradually increasing voltage, demonstrating excellent cyclic stability with no obvious degradation with each cycle, which also indicates great potential in humidity sensor applications. The electrical outputs of recently reported MEGs are summarized in Table 1. Clearly, the MEG with acidified GO / PVA in this fabrication exhibits a more comprehensive electrical output than the reported MEGs.

[0306] [Table 2]

[0307] Mechanism of action The proposed mechanism of electricity generation from acidified GO / PVAMEG, including ionization, charge separation, and charge recombination, is shown in Figure 24(a). 18The protons in the functional groups are immobilized without absorption of water from humidity. During ionization, humidity on the top side of the GO / PVA membrane promotes the dissociation of functional groups (-OH and -COOH), which then serve as mobilized H as charge carriers for power generation. + Next, H + is mobilized H + Since the concentration of H is higher on the top side exposed to humidity, it migrates from the top side to the bottom side, achieving charge separation and voltage generation. + The particles migrate in the direction of swimming toward both sides of the apex, leading to charge recombination. 11 Therefore, the charging and discharging process is directly triggered by moisture rather than complex chemical reactions, and as a result, the MEG can be charged quickly and exhibits stable electrical output by harvesting this clean energy.

[0308] To verify the improved MEG device performance resulting from the increased group density after HCl treatment, material characterization techniques such as X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were performed on the films with and without acidification. The diffraction peak of the GO / PVA film exhibits a lower diffraction angle (14.4° to 6.6°) than the GO film and shifts to a higher diffraction angle (6.6° to 8.0°) after increasing the HCl concentration. The layer spacing of the GO / PVA film can be calculated using Bragg's law. The GO / PVA film exhibits a higher layer spacing than the GO film: 0.77 nm for the GO film, 1.26 nm for the GO / PVA film with 0.0% HCl, 1.19 nm for the GO / PVA film with 1.0% HCl, and 1.10 nm for the GO / PVA film with 32.0% HCl. The polymer molecules of PVA may enter into the GO interlayer and enlarge the interlayer spacing, which may explain why the GO / PVA membrane exhibits a wider interlayer spacing than the GO membrane. The cross-linking between GO and PVA may cross-link adjacent GO sheets because the carboxyl groups from GO can react with the hydroxyl groups in the cross-links. 23 , which contributes to a more uniform and stable structure. Furthermore, the layer spacing of the GO / PVA film decreases after HCl acidification. The shortened spacing of the GO / PVA film by HCl acidification is due to the + The charge ions (H) induced by HCl acidification may be absorbed by oxygen-based groups and inhibit the cross-linking of GO with PVA.+ ) can arise from

[0309] Figures 24(b)-24(c) show XPS spectra of the C1s region in GO / PVA films acidified with 0.0% HCl, 1.0% HCl, and 32.0% HCl. The C1s peaks in GO / PVA (0.0% HCl) with binding energies of 284.8 eV, 286.2 eV, 287.0 eV, and 289.2 eV represent C-C (45.29 at.%), C-O (19.18 at.%), C=O (4.67 at.%), and C-C=O (4.84 at.%), respectively. The C1s peaks in GO / PVA (1.0% HCl) with binding energies of 284.8 eV, 286.0 eV, 287.0 eV, and 289.1 eV represent C-C (28.61 at.%), C-O (18.50 at.%), C=O (14.91 at.%), and C-C=O (5.96 at.%), respectively. The C1s peaks in GO / PVA (32% HCl) with binding energies of 284.8 eV, 285.9 eV, 287.0 eV, and 289.0 eV represent C-C (28.30 at.%), C-O (14.26 at.%), C=O (20.75 at.%), and C-C=O (4.49 at.%), respectively. Thus, the proportion of C-O bonds decreases after HCl acidification, while the proportion of C=O bonds increases after HCl acidification. It has been reported that films with more C=O bonds exhibit higher work functions and surface potentials.10 The surface potential of GO / PVA films analyzed by Kelvin probe force microscopy (KPFM) under room humidity (RH = 55%) increased after acidification, which can be attributed to the increased ratio of C=O bonds after HCl acidification.

[0310] After HCl acidification, the epoxy groups can be arranged in a row, which leads to the breaking of the C-C bond. The epoxy chains tend to be oxidized to epoxy pairs and converted to carbonyl pairs, since the carbonyl group is more stable in this state (Figure 24(d)). The C=O, which has a stronger polarity, tends to be converted to H + is better than CO at attracting CO and forming hydrogen bonds. Therefore, a higher voltage output will result in more H from the dissociation of functional groups (-OH and -COOH). +This may be due to the more C=O bonds that attract hydroxyl groups, leading to a larger protonation gradient for superior electrical output. + ) density is the more dissociated H in the film exposed to humidity. + The V of the GO / PVA films washed with acetic acid and NaOH was also investigated to identify the exact functional groups responsible for the improved voltage output. The GO / PVA films washed with acetic acid exhibit CC (35.96 at.%), CO (22.28 at.%), C=O (1.27 at.%), and OC=O (6.13 at.%), while the GO / PVA films washed with NaOH exhibit CC (37.86 at.%), CO (25.24 at.%), C=O (2.74 at.%), and OC=O (2.47 at.%). max are 0.34 V and 0.22 V, respectively, which are much lower than the film acidified by HCl because the ratio of C=O in the GO / PVA films washed with acetic acid and NaOH is much lower. Therefore, the ratio of C=O is closely related to the electrical output of the GO / PVA film.

[0311] First-principles calculations based on density functional theory (DFT) were performed to provide atomistic insight into the observed enhancement of electrical output induced by HCl acidification of graphene oxide. Specifically, we simulated the proton binding process of O- and OH-surface-functionalized graphene oxide with and without carbon vacancies generated by acidification. Our theoretical DFT results showed that the formation of hydrogen bonds between mobile protons and surface-immobilized functional groups is significantly enhanced by the presence of carbon vacancies, which may explain the enhanced electrical output observed experimentally. A summary of our theoretical DFT results is provided in Figure 25.

[0312] Carbon vacancy (V C), mobile protons tend to form strong chemical bonds with O atoms on the carbon surface (Figure 25(a)). In this case, the energy corresponding to the proton bond amounts to 1.12 eV / H, which causes H chemisorption and is therefore detrimental for proton migration (i.e., the interaction between O and H is found to be too strong). On the other hand, the interaction between mobile protons and surface O atoms is weaker than V, since the latter are already strongly adsorbed on graphene oxide. C These interactions are less strong in the presence of defects (i.e., on the order of 0.1 eV). Therefore, these interactions are more effective in transferring charge to the mobile H + ions (Figure 25(b)). This results in numerous hydrogen bonds formed on the carbon surface that involve electrostatic attraction rather than fully covalent interactions, which has been found to be beneficial for proton migration to achieve higher electrical output.

[0313] When considering functional groups (-OH) on the carbon surface, the general conclusions are very similar to those reported in the paragraph above. C It was found that -OH spontaneously desorbs from the carbon surface when H is bonded when the surface is sparse (Figure 25(c)). The effect of -OH desorption is due to the formation of water molecules (relatively weak CO surface bonds (i.e., E OC ≈0.1 eV) to the OH molecular bond), which is clearly undesirable for charge-discharge cycling purposes. Conversely, in the presence of abundant carbon vacancies, V C A nearby immobilized -OH tends to establish a moderate hydrogen bond with the mobile proton (Figure 25(d)). In this latter case, electrons are transferred to the very stable CO surface bond (i.e., E OC ≈3.7 eV) to a covalent OH bond is energetically unfavorable, and therefore the mobile H ion is captured by the functional group (-OH) via modest electrostatic forces.

[0314] Overall, our theoretical DFT simulations reproduce the experimentally observed enhancement of electrical power induced by HCl acidification of graphene oxide. The point of increase in hydrogen bond formation is its intrinsic cause.

[0315] Demonstration of application MEG with high voltage and high current can directly power electronic devices such as memristors and sensors, significantly improving their practical applications. To further enhance the voltage or current output, MEG units were directly connected in series or parallel. The maximum currents are 9.28 μA, 18.16 μA, and 40.69 μA for 1 unit, 2 units, and 4 units, respectively (Fig. 26(a)). In addition, V max are 0.85 V, 1.70 V, and 3.38 V for 1 unit, 2 units, and 4 units, respectively (Fig. 26(b)). Thus, the voltage and current of the MEG increase almost linearly with the electrical output of 1 unit (Fig. 26(c)), demonstrating the great potential in generating high electrical output by a simple assembly of units in series or parallel. The enhanced power generation performance may further broaden their potential applications, such as hydrogen catalysis.

[0316] GO / PVA films acidified with 32.0% HCl were also fabricated on carbon cloth for flexible device applications. The acidified GO / PVA films on carbon cloth were attached to glass bottles with various radii to investigate the effect of film curvature on the voltage output of the GO / PVA films. V max is 0.0cm -1 , 0.5cm -1 and 1.0 cm -1The voltages are 0.83 V, 0.85 V, and 0.84 V for films with curvatures of 0.83 V, 0.85 V, and 0.84 V, respectively (Fig. 27(a)). Thus, the acidified GO / PVA film exhibits stable voltage output on flexible substrates with various curvatures, demonstrating its great potential in flexible electronics. To incorporate the GO / PVA film into flexible and wearable applications, the film must exhibit good electrical output upon mechanical motion such as bending. The acidified GO / PVA film on carbon cloth was bent from 0° to 120° within 1 second. The flexible MEG exhibited a significant V max It can withstand 2000 bending deformations without degradation, indicating great potential for flexible and wearable applications (Fig. 27(b)).

[0317] Furthermore, MEG exhibits good stability during charge and discharge cycles. MEG can be directly charged by moisture, with a current of 20 μA cm 2The MEG exhibits a similar charge / discharge process with good stability at each cycle. The power harvested by the MEG from moisture can also directly charge a power storage device (e.g., a commercially available capacitor (20 μF) was charged to 0.80 V in 300 s (Fig. 27(c))), demonstrating great potential for simultaneous energy conversion and storage. The electrical output of an external device powered by the MEG was investigated by connecting load resistors with various resistances (Fig. 27(d)). As the load was increased from 1 kΩ to 3 MΩ, the resistor voltage increased from 0.01 V to 0.81 V, while the current decreased from 8.55 μA to 0.27 μA. The maximum output power of the load resistor was 1.36 μW with a resistance of 0.1 MΩ. Furthermore, a commercially available pressure sensor could be directly powered by a single MEG at room humidity (55%), demonstrating the potential for external pressure stimulation. The electrical signal was generated according to the method described above (Figures 27(e)-27(f)), demonstrating its great potential in powering practical devices at room humidity. Furthermore, device arrays can be easily realized by dividing the membrane into small pieces to power practical devices, since the electrical output is independent of the membrane area. Acidified GO / PVA membrane patterns were fabricated on FTO glass by the above method, followed by dividing the membrane into 20 parallel units and coating Ag paste on the top side of all units as top electrodes to increase their current output. A pattern with 20 parallel units can also be connected in series to improve voltage output. This array (2 in series x 20 in parallel) was able to provide enough power to power a commercial computer (Figure 27(g)).

[0318] conclusion In summary, we use HCl-treated GO / PVA to fabricate MEG because HCl acidification and PVA addition can improve the protonation gradient of MEG on the substrate and the microstructural stability of the acidified film, which are beneficial for achieving high electrical output with good stability, respectively. The top surface of the acidified GO / PVA film is directly exposed to moisture. The bottom side is tightly attached to the FTO glass, which robustly blocks moisture penetration. Driven by this moisture asymmetry, electrical output is generated between the top and bottom sides of the GO / PVA film. As a functional layer, the GO / PVA film surpasses the performance of GO and PVA films by providing high and stable voltage output. The voltage output is closely related to the protonation gradient, which can be improved by HCl acidification and high RH. A high voltage of 0.85 V and a current of 9.28 μA (92.8 μA cm) were obtained. 2 ) was generated by the 32.0% HCl acidified GO / PVA film at RH = 75%, which could be easily enhanced by series or parallel connection (3.38 V or 40.49 μA for four units in series or parallel). The voltage of the acidified GO / PVA film on flexible carbon cloth did not show any clear decrease with film curvature and folding cycles, demonstrating its great potential for flexible and wearable applications. The acidified GO / PVA film could also be easily sectioned into patterns for higher electrical performance and could successfully power a commercial computer, making it promising for harvesting energy from water and powering various practical devices.

[0319] Section 3: Samples and Results Section 3 below describes the third series of samples and results.

[0320] The results shown in Figures 28, 29, 30, and 31 pertain to HNO3-treated MEG samples. The MEG samples comprise a functional layer comprising graphene oxide and a PVA film on FTO glass. (a) Samples without acidification, (b) samples acidified with HNO3 solution, and (c) samples acidified with HNO3 vapor were tested.

[0321] In the first method, for liquid acid treatment, the GO / PVA layer was immersed in HNO solution (70 wt%) for 10 min, then the device was washed with distilled water for 10 min and dried at 50 °C for 12 h.

[0322] In the second method, for steam treatment, the GO / PVA layer was suspended over a HNO solution (70 wt%) in a sealed chamber. The device was then washed with distilled water for 10 min and dried at 50 °C for 12 h.

[0323] The layer spacing was found to increase after acidification (7.92 Å for GO, 7.99 Å for HClGO, and 8.32 Å for HNO3GO). The wider layer spacing contributes to faster swimming motion.

[0324] The O / C ratio in the pristine (non-acidified) GO film is 34.52%.

[0325] The O / C ratios in the GO films acidified with HNO3 solution and HNO3 vapor are 54.31% and 53.80%, respectively. These results demonstrate that the C=O bonds are significantly increased via HNO3 treatment.

[0326] The power output of the device at 80% relative humidity is shown in Figure 30. The samples were approximately 0.5 cm 2 The sample has a zinc top electrode with an area of ​​approximately 1 cm and a carbon nanotube (CNT) bottom electrode. 2 The functional layer has an area of ​​0.01 mm and is treated with 70% HNO3. The bottom electrode is a MW carbon nanotube. For the Zn foil device, it can be seen that the voltage is very high (about 1.6 V) (contributed by the redox behavior of Zn). The current is limited by the contact area between GO and Zn.

[0327] The results in Figure 31 show that the voltage / current is 2 For a sample with a top electrode of Ag paste with an area of ​​1000 V, bending at 70% humidity is shown. maxis 0.89V, and I max is 13.21mA. Current after 100 minutes of operation = 0.19mA.

[0328] Section 4: MEG devices with layered structures Section 4 below describes the fourth series of samples and results.

[0329] The following description further describes the power generating cell (also called a moisture electric generator (MEG) cell, moisture electric generating device or MEG device) with reference to the accompanying drawings.

[0330] 33, a moisture power generating device 3300 includes a first electrode 3310 and a second electrode 3320. Disposed between the first electrode 3310 and the second electrode 3330 is a functional layer, which emits charge carriers to the first and second electrodes. The functional layer may also be referred to as an active layer.

[0331] The functional layer 3330 includes sublayers. In the MEG cell shown in FIG. 33 , the layer 3330 includes a first sublayer 3312 and a second sublayer 3314. The first sublayer 3332 can provide moisture to the second sublayer 3334. Moisture includes water molecules. Water molecules can exist in liquid or water vapor and in humid environments. The first sublayer 3332 acts as a moisture reservoir for the second sublayer 3334. The second sublayer 3334 is a functional sublayer that releases charge carriers in response to available moisture from the first sublayer. The first sublayer, which acts as a moisture reservoir, can be referred to as a moisture sublayer, moisture reservoir sublayer, or hydration sublayer. Typically, the functional layer includes functional groups that generate charge carriers when exposed to moisture by dissociating water molecules. The first sublayer 3332 can provide moisture to the second sublayer 3334 , and the second sublayer 3334 generates charge carriers in response to the moisture received from the first sublayer 3332 .

[0332] For example, if the second sublayer comprises a carbon-based nanomaterial, oxygen containing functional groups within the surface of the carbon-based nanomaterial interact with and dissociate water molecules from the moisture to generate mobile hydrogen ions.

[0333] The moisture reservoir sublayer has moisture absorption and storage properties, is capable of being hydrated, and is capable of providing moisture to other sublayers of the moisture power generating device.

[0334] The inclusion of a moisture reservoir (or water reservoir) sublayer in a moisture harvesting (MEG) device facilitates controlled delivery of moisture to the functional sublayer. The functional sublayer dissociates charge carriers upon absorbing moisture. For example, functional groups in the functional layer generate charge carriers by dissociating water molecules from moisture. Moisture is transferred from the moisture reservoir sublayer to the functional sublayer. The moisture reservoir provides moisture within the functional sublayer. By providing moisture from the first sublayer 3332 to the functional sublayer 3334, the functional sublayer 3334 is less dependent on absorbing moisture from environmental conditions because it can absorb water molecules from the sublayer acting as a moisture reservoir. The second sublayer 3334 can additionally absorb moisture directly from the environment through any surface exposed to the environment, but the second sublayer receives moisture from the first functional layer.

[0335] Assuming moisture is provided from the first sublayer to the second sublayer, the second sublayer is less dependent on the environment as its sole source of moisture, allowing the moisture harvesting device to generate charge under both low and high humidity conditions. This results in less change in the performance of the MEG device when environmental humidity conditions change, as moisture delivery to the second sublayer can be maintained from the first sublayer. Water in the reservoir sublayer will evaporate at low humidity, and the reservoir sublayer will adsorb water from the environment in high humidity environments.

[0336] The moisture sublayer acts as a shock absorber, acting as a buffer between the second sublayer (the functional sublayer) and environmental conditions. The presence of the moisture sublayer produces a more consistent moisture delivery to the functional sublayer than if the functional sublayer were completely dependent on moisture from environmental conditions. The presence of the moisture sublayer allows the functional sublayer to receive moisture regardless of the environmental conditions to which the moisture harvesting device is exposed (assuming the moisture sublayer is sufficiently hydrated).

[0337] A sublayer functioning as a moisture reservoir can retain moisture and thus provide that moisture to other layers, thereby serving as a pool for other layers in a moisture harvesting device. A sublayer can also release moisture to other sublayers to hydrate them, and thus can be referred to as a hydration layer. A first sublayer functioning as a moisture reservoir for a second sublayer can hydrate the second sublayer. Moisture can be provided from the first sublayer to the second sublayer, meaning that the second sublayer can be hydrated even in low-humidity environmental conditions (assuming adequate moisture is available from the first sublayer). Thus, the first sublayer can hydrate the second sublayer even in ambient or extreme conditions (0% relative humidity (RH)).

[0338] The first sublayer is more hydrophilic than the second sublayer, acting as a moisture reservoir to provide moisture to the second sublayer.

[0339] FIG. 34 shows the migration of moisture 3400 from the first sublayer 3332 to the second sublayer 3334.

[0340] In some moisture-powering devices, the first sublayer 3332 is a polymer.

[0341] Some polymers are hydrophilic polymers. Hydrophilic polymers contain hydrophilic functional groups. These hydrophilic polymers can be hydrated.

[0342] Hydrophilic polymers can be efficient moisture absorbers, meaning that the polymer can absorb moisture from the environment even in low-humidity environments. A moisture-harvesting device including a polymer exposed to the environment can absorb moisture into the moisture-harvesting device even in low-humidity environments. This allows moisture to be absorbed into the moisture-harvesting device by the polymer sublayer. This allows the moisture-harvesting device to absorb moisture more easily than a device with a single non-polymer (e.g., GO) functional layer. The efficient moisture absorption property allows the moisture-harvesting device to absorb water in low-humidity environments. This can improve the electrical performance of the device in low-humidity environments.

[0343] Polymers can be hydrated. They can absorb and retain water. A fully hydrated polymer layer can provide moisture to other layers of a moisture-generating device. A hydrated polymer layer can contain abundant water that keeps the second sublayer hydrated. This property allows the polymer layer to provide moisture to other layers of the moisture-generating device under various environmental conditions. Assuming the polymer is fully hydrated, the polymer layer can provide moisture to other layers of the moisture-generating device regardless of environmental humidity conditions. For example, the polymer can provide moisture to other layers of the moisture-generating device under low relative humidity (RH) conditions (e.g., 0%) as well as high relative humidity conditions (e.g., 100%).

[0344] Examples of polymers include 4-styrenesulfonic acid (PSSA), PSSNa, PAA, PVA, PSSLi, PSSK, PSSNH4, PSSMg2, PSSAl3, PSSH, chitin, chitosan, cellulose, starch, gum, alginate, and carrageenan, polyamides, polyphenols, organic polyesters, inorganic polyesters, and polyanhydrides. Polymers include hydrogels.

[0345] The physical properties of some polymers, including flexibility, stretchability, ease of device fabrication, cost-effectiveness or translucency, and ability to function in low humidity, may make them suitable for fabricating moisture-harvesting devices.

[0346] In some moisture power generating devices, the first electrode 3310, second electrode 3320 and functional layer 3330 are arranged in a stacked orientation.

[0347] Reference is now made to Figure 35, which shows a top perspective view of a moisture power generating device. Figure 35 is shown for illustrative purposes only and is therefore not to scale.

[0348] In Figure 35, moisture power generating device 3500 includes a first electrode 3510 (also referred to as the top electrode), a second electrode 3520 (also referred to as the bottom electrode), and a functional layer 3530. The functional layer 3530 includes a first sublayer 3532 and a second sublayer 3534. In the device shown in Figure 35, first electrode 3510 is attached to surface 3533 of the first sublayer. Second electrode 3520 is attached to surface 3535 of the second sublayer. In the device of Figure 35, surfaces 3533 and 3535 are opposite surfaces of the functional layers. It should be apparent that the orientation of the device is not limiting and these labels are used for illustrative purposes only.

[0349] The functional layer 3530 has length (L) and depth (D) dimensions that are much larger than its thickness (E) dimension. For example, the thickness of the functional layer may be about 0.5 mm, the length may be about 1 cm, and the depth may be about 1 cm. The surface areas of the surfaces 3533 and 3535 are large compared to the cross-sectional area of ​​the layer. The surfaces defined by the length (L) and depth (D) dimensions may be referred to as in-plane surfaces. The bottom electrode 3520, second sublayer 3534, first layer 3532, and top electrode 3510 are vertically stacked with large surface areas of the faces connected to each other (rather than the layers being connected in an end-to-end configuration).

[0350] A stacked configuration (with vertically stacked layers) is beneficial because the interfaces between the layers have a large surface area (i.e., a much larger surface area compared to the cross-sectional area of ​​the layers that would be used in the end-to-end interfacial connection between the layers). This large interfacial area reduces the internal resistance of the moisture harvesting device. The large interfacial area provides an opportunity for greater flow of charge carriers.

[0351] The sublayers are stacked vertically to form the functional layers. In the devices of Figures 33 and 35, the sublayers are adjacent. Adjacent layers are electrically connected.

[0352] Positioning the sublayers in an adjacent arrangement provides an electrical interface between the first and second sublayers. The electrical interface facilitates direct transfer of charge carriers between the first and second sublayers. The adjacent arrangement also provides. The adjacent sublayer arrangement also allows for direct moisture transfer between the layers.

[0353] In some instances, the functional layer is a bilayer structure having two sublayers. The first sublayer acts as a moisture reservoir for the second sublayer, and the second sublayer is the functional sublayer. Other devices may include three or more sublayers. In some devices, the first and second sublayers may not be adjacent.

[0354] In some devices, the first sublayer contributes charge to the moisture-powered device. In some moisture-powered devices, the first sublayer can release charge carriers when the moisture-powered cell is exposed to moisture. The first sublayer can have MEG properties and release charge carriers when exposed to moisture. An advantage is that both the second sublayer and the first sublayer are MEG layers. This provides the advantage that charge carriers can be provided to the moisture-powered device by the first sublayer in addition to the charge carriers provided by the second sublayer when the device is exposed to moisture. This increase in the number of charge carriers can increase the electrical performance (such as voltage) of the device compared to a single-layer MEG device.

[0355] In some moisture-powered devices, the second sublayer has a net charge opposite to the charge of the charge carriers released in the first sublayer. For example, if protons tend to be released from the first sublayer, the second sublayer can be selected to have a net negative charge. Graphene oxide, which has a net negative charge (graphene oxide is also a functional layer), is a candidate material for the second sublayer in this case. The net negative charge of the second sublayer is advantageous for attracting positive charge carriers from the first sublayer. This charge attraction can help increase charge flow through the MEG device and improve the electrical characteristics of the MEG device. Some examples can include increasing the voltage and current of the moisture-powered device.

[0356] The second sublayer can be a carbon-based material. For example, the second sublayer can be graphene oxide (GO). Graphene oxide contains multiple functional groups, and therefore, when it absorbs water, it converts H + Dissociates ions. Graphene oxide has a higher density than many other porous materials (e.g., Mxene).

[0357] Graphene oxide is a good candidate material for the second sublayer as it can adsorb excess water from the polymer layer, and GO is also negatively charged, so it can attract generated protons from the polymer layer.

[0358] 36 is positioned to create a moisture gradient across the device. In MEG device 3600, second sublayer 3634 is located between first layer 3632 and second electrode 3620. Top surface 3632 of second sublayer 3634 faces first sublayer 3632. In device 3600, top surface of second sublayer interfaces with first sublayer. Bottom surface 3636 of second sublayer 3634 faces second electrode 3620. Device 3600 is positioned to resist ingress of moisture into the bottom surface of the second sublayer.

[0359] In Figure 36, electrode 3620 extends across the entire bottom surface of the second sublayer. Electrode 3620 covers the bottom surface of second sublayer 3634. Examples of suitable materials for the bottom electrode include carbon-based materials (e.g., carbon nanotubes, graphene). Other suitable materials for the bottom electrode include FTO, ITO, MXene, Au, Pt, and carbon black.

[0360] By covering the bottom surface, electrode 3620 reduces the penetration of moisture from within electrode 3620 into the second sublayer. Preferably, electrode 3620 prevents moisture from penetrating into the second sublayer. Preferred electrodes have moisture insulating properties to resist moisture penetration into the second sublayer.

[0361] Additional resistance to moisture penetration can be provided by mounting the bottom electrode 3620 on a separate substrate. This can improve the moisture resistance properties of the bottom layer by requiring that any moisture penetrating into the second sublayer of the functional layer must first penetrate into the substrate and then into the first electrode 3620 in order to penetrate into the second sublayer.

[0362] In the example of Figure 36, electrode 3620 covers the surface of second sublayer 3634. As shown in Figure 36, bottom electrode 3620 extends across the entire bottom surface of the second sublayer. This configuration shields the entire surface from direct contact with moisture. As discussed above, this helps reduce moisture penetration across the bottom surface of the device.

[0363] An advantage of resisting moisture ingress into the bottom surface of the second sub-layer is that a moisture gradient can be created across the moisture power generating device.

[0364] 36, the MEG device 3600 is configured to promote absorption of moisture into the top surface 3633 of the first sublayer. This configuration promotes creating a moisture absorption differential between the surfaces of the functional layers when the device is placed in a humid environment. This promotes abundant moisture absorption into the top surface of the functional layer 3633 and a lack of moisture absorbed into the bottom surface of the functional layer 3636.

[0365] In the embodiment of Figure 36, the first electrode 3610 is configured to cover only a portion of the top surface 3633 of the first sublayer 3632. The electrode 3610 does not fully cover the top surface 3633. The electrode 3610 partially covers the top surface 3633. The remainder of the top surface 3633 of the first sublayer is left uncovered. The uncovered portion of the top surface 3633 is exposed to environmental conditions. This allows moisture 3640 to directly contact the top surface 3633. A larger top electrode may result in a larger current-carrying capacity through the electrode.

[0366] In some devices, the electrode 3610 may cover the entire top surface 3633 of the first sublayer. Figure 36(b) shows a moisture harvesting device similar to that described above with reference to Figure 36, but in the device of Figure 36(b), the top electrode 3610 covers the top surface 3633 of the first sublayer. Preferably, such a top electrode should be moisture hygroscopic, allowing moisture to penetrate into the electrode and onto the functional layer. Such an electrode may be porous. Such an electrode may be a silver nanowire.

[0367] A larger top electrode with a larger contact area (interface) with the functional layer can result in a larger current carrying capacity through the electrode junction, but if the electrode is too large, water may be prevented from escaping the functional layer and moisture may also be prevented from contacting the surface through the electrode.

[0368] The porous top electrode 3610 allows moisture to penetrate into the electrode and into the top surface 3633 of the functional layer. As a result, if the top electrode 3610 is porous, a larger top electrode can be used that covers a larger portion of the top surface of the functional layer but still allows moisture to be absorbed into the top surface 3633 of the functional layer. Moisture is absorbed into the top electrode 3610 and penetrates through the top electrode 3610 into the surface of the functional layer. The porous electrode allows for an increased contact area between the electrode and the surface of the functional layer, facilitating achieving higher currents. One example of a porous electrode that may be suitable for use as a top electrode is a silver nanowire-based electrode.

[0369] More generally, examples of porous electrodes include electrodes containing metal nanowires. Preferably, the metal should have good resistance to corrosion if intended for long-term use. Because metal nanowires have a network structure, moisture can penetrate into the electrode and into the functional layer.

[0370] If the top electrode fully covers the top surface of the first sublayer (as shown in FIG. 36(b)) but is not porous, the top electrode will prevent moisture from being absorbed into the top surface of the first sublayer. In such a device, moisture can be absorbed into the first sublayer from both sides of the device (and any other portion of the first sublayer will be exposed to environmental conditions). In FIG. 36(b), moisture 3640b and 3640c can be absorbed into the surface area of ​​both sides 3632c and 3236b of the first sublayer. In these cases, the surface area of ​​the first sublayer that can absorb moisture from the environment is significantly reduced compared to devices with electrodes that only partially cover the top surface of the first sublayer and / or porous electrodes. This reduces the amount of moisture that can be absorbed from the environment compared to devices with electrodes and / or porous electrodes that only partially cover the top surface of the first sublayer.

[0371] Sublayers (e.g., polymer layers) that function as moisture reservoirs can contain ionic salts. The concentration of the salts plays an important role in device performance. The presence of ionic salts in the polymer layer provides mobile ions that can serve as a medium for enhancing ion concentration gradients across the device. MEG devices containing ionic salts in the polymer layer can have higher voltage outputs than devices without ionic salts. Such free ions significantly enhance the conductivity of the polymer layer. Salts include NaCl and KCl. Li, Na, and K are considered Group 1 alkali metals.

[0372] The presence of ionic salts within the polymer layer has several advantages: 1) the ionic salts lower the internal resistance and enhance power output through the introduction of mobile ions; 2) the salts enhance the water adsorption capacity of the reservoir sublayer; and 3) the ions respond to changes in humidity. At low humidity, ions at the air-exposed interface become activated due to the loss of bound water molecules, and their ionic hydration energy is greater than that of ions in the bottom region of the hydrogel. Iontophoretic momentum arises from this energy difference.

[0373] The sublayer that functions as a moisture reservoir can be a hydrogel layer. Hydrogels are three-dimensional networks of polymer chains. Hydrogels are hydrophilic and can absorb large amounts of water. The advantage of using hydrogels is that they have good moisture absorption properties. They can absorb moisture even in low-humidity environments. Hydrogels can be hydrated and provide a moisture source to adjacent sublayers. This makes hydrogels effective for use as moisture reservoir layers (hydration layers).

[0374] Hydrogels have a three-dimensional framework. This structure provides operational durability because the structural integrity of the hydrogel layer can be maintained in a humid environment once the hydrogel is hydrated. This allows MEG devices to maintain their performance. Hydrogels are also versatile in that they can be doped with various ions. These are ionic hydrogels. For example, metal ions and salts can be infused into the hydrogel. This provides flexibility in charge carriers when designing MEG devices.

[0375] Hydrogels offer excellent water retention and can contain induced mobile ions. The hydrophilic nature of hydrogels with efficient moisture absorption means that the device is less limited by environmental humidity conditions compared to single-layer conventional MEGs and can still generate electricity in low-humidity environments.

[0376] The first sublayer can be doped with charge carriers. Introducing additional charge carriers can improve the electrical performance of the moisture harvesting device. + Abundant H from dissociation of ions + In a humid environment where ions and ions are present, the dominant charge carriers are H + ions. In a lower humidity environment, there are fewer H + Although the ions are dissociated due to the reduced amount of moisture, the metal ions from the first sublayer remain mobile and therefore can contribute to the electrical performance of the MEG device.

[0377] Section 5: MEG devices having a layered structure and including polymers: Referring now to FIG. 37, a power-generating cell 3700 includes a first electrode 3710 and a second electrode 3730. Disposed between the first and second electrodes is a functional layer 3730. The functional layer releases charge carriers when the power-generating cell 3700 is exposed to moisture. The functional layer has moisture generator (MEG) properties. Moisture includes water molecules. Water molecules can exist in liquid or water vapor and in humid environments. The MEG properties include functional groups that generate charge carriers by dissociating water molecules.

[0378] In the example of FIG. 37 , functional layer 3730 includes two sublayers, 3732 and 3734. Other embodiments may include three or more sublayers. The sublayers are stacked between first electrode 3710 and bottom electrode 3720. In the example of FIG. 37 , both of the sublayers release charge carriers when power generating cell 3700 is exposed to moisture. Both layers have MEG properties. In FIG. 37 , sublayers 3732 and 3734 include different materials. The sublayers may release the same type of charge carriers.

[0379] Sublayer 3732 is a polymer sublayer. In the example of Figure 37, the polymer is 4-styrene sulfonic acid (PSSA). Alternative polymer materials suitable for the polymer layer include PSSNa, PAA, PVA, PSSLi, PSSK, PSSNH4, PSSMg2, PSSAl3, and PSSH.

[0380] PSSA is acidic and can be corrosive. An advantage of other polymeric salt-based materials, including PSSNa, is that the material is neutral and non-acidic. This structure offers the advantage of being able to be implemented in wearable technology.

[0381] Sublayer 3734 releases charge carriers when exposed to moisture. The moisture can be received from polymer layer 3732. Polymer layer 3732 acts as a moisture reservoir. Polymer layer 3732 provides moisture and hydrates layer 3734. In the example of FIG. 37, sublayer 3734 is a graphene oxide (GO) sublayer. GO has advantages over other materials due to its abundance of functional groups. In other examples, sublayer 3734 can be a carbon-based material. In another example, sublayer 3734 can be a polymer layer. Examples of suitable polymers include PVA and PAA.

[0382] MXene and MXene oxide may also be used as sublayers.

[0383] Sublayer 3732 is adjacent to and electrically connected to sublayer 3734. The surface areas of the sublayers form an interface.

[0384] The first electrode 3710 is adjacent to the polymer sublayer 3732. The first electrode 3710 is electrically connected to the polymer sublayer 3732.

[0385] In the example of FIG. 37 , the first electrode 3710 is porous to moisture. Moisture can penetrate into the electrode 3710 and into the polymer layer 3732. In the example of FIG. 37 , the first electrode 3710 partially covers the polymer layer 3732. In another embodiment, the first electrode can completely cover the top surface of the polymer layer 3732. When the power-generating cell 3700 is exposed to moisture, moisture can penetrate directly into the polymer sublayer 3732 through that portion of the sublayer (that is directly exposed to moisture). Moisture can also penetrate into the polymer layer 3732 through the first electrode 3710.

[0386] 37, the first electrode 3710 is Zn foam. In other examples, the first electrode can include Ag, Zn, Zn plate, Zn foam, Al, Mg, Cu, Ni, Fe, or Ti.

[0387] Sublayer 3734 is adjacent to and electrically connected to second electrode 3720. In the example of FIG. 37, second electrode 3720 is carbon nanotubes. Electrode 3720 covers the surface of sublayer 3734. In the example of FIG. 37, second electrode 3720 is insulating against moisture. Second electrode 3720 repels moisture. Moisture cannot penetrate into sublayer 3734 through second electrode 3720.

[0388] In an exemplary embodiment, the second electrode is a carbon nanotube (CNT).

[0389] An advantage of the stack structure and electrode configuration of power-generating cell 3700 is that when power-generating cell 3700 is exposed to moisture, moisture can penetrate into polymer sublayer 3732 either through first electrode 3710 or directly through contact with the surface of sublayer 3732. However, moisture is prevented from penetrating into sublayer 3734 through the second electrode. This configuration creates a moisture gradient across the power-generating cell. In particular, a moisture gradient is created across functional layer 3730.

[0390] Sublayer 3732 is more hydrophilic than sublayer 3734. By placing polymer layer 3732 at ambient conditions rather than GO layer 3734, moisture harvesting device 3700 absorbs more moisture from the environment compared to the GO layer at ambient conditions. This improves the moisture absorption efficiency of moisture harvesting device 3700.

[0391] Another advantage is that this laminated structure can have a much higher voltage output compared to a single-layer MEG. The combination of different moisture absorption properties with the two layers also extends the lifespan of the MEG.

[0392] Sublayers 3732, 3734 may have different moisture absorption properties. In the example of Figure 37, sublayer 3732 has greater moisture absorption properties than sublayer 3734 (i.e., sublayer 3732 is more hydrophilic than sublayer 3734).

[0393] An advantage of sublayer 3732 having greater moisture absorption properties compared to sublayer 3734 is that when power-generating cell 3700 is exposed to moisture, sublayer 3732 can act as a moisture reservoir for sublayer 3734. Thus, moisture is absorbed into PSSA sublayer 3732. The absorbed moisture can permeate into PSSA sublayer 3732 and into GO sublayer 3734 through the interface between the sublayers.

[0394] This allows the layer to function in low humidity. The device can function in low humidity because sublayer 3732 is more hydrophilic and therefore can absorb moisture from the environment even in low humidity environments. In this configuration, the source of moisture for sublayer 3734 is sublayer 3732. This means that hydration of 3734 relies on moisture from sublayer 3732, not the environment (except for those portions of sublayer 3734 that are exposed to the environment (e.g., uncovered sections or edges); in these cases, some moisture may be received directly from the environment in addition to that received from sublayer 3732).

[0395] 37, the first electrode 3710 undergoes an electrochemical reaction when exposed to moisture. This electrochemical reaction may increase the voltage across the power-generating cell 3700. The electrochemical reaction may improve the electrical properties of the power-generating cell.

[0396] Some advantages of polymer-based MEG devices include that they are flexible, stretchable, easy to fabricate, cost-effective, translucent, and capable of functioning in low humidity.

[0397] Advantages of this design include functioning in both low and high humidity and high voltage and current outputs.

[0398] Production technology: These power generating cells were fabricated using the following techniques.

[0399] Carbon nanotubes (CNTs), graphene oxide (GO), and poly(sodium 4-styrenesulfonate) (PSSNa) were separately dispersed in distilled water by sonication for 30 min each. Then, 400 μL of a 20 wt % CNT dispersion was applied to a PET (1 × 2 cm) substrate at 50 °C for 2 h to serve as the bottom electrode. 2 ) and dried. 200 μL of 2 wt % GO dispersion was coated onto a CNT film (1 × 1 cm) at 50 °C for 2 h. 2 Glycerol was mixed with a 5 wt% PSSNa solution in distilled water (PSSNa:glycerol = 5:2) by sonication for 30 min. 200 μL of the mixed solution was applied to a PET (1 × 1 cm) plate at 50 °C for 2 h. 2 ) and then peeled off to obtain a free-standing polymer film. The polymer film was placed on a 0.5 × 0.5 cm 2 The Zn foam was layered on top of the GO film.

[0400] result: Figure 38 shows the current characteristics of various samples of power-generating cells. The cell performance is measured in various humidity environments (RH%). Figure 38 shows the current versus time graphs of moisture-power-generating cells with various types of top electrodes (Zn plate and Zn foam) and operating in various relative humidity environments (60% RH and 85% RH). The samples show mA-range current output. High humidity and large size electrodes lead to good current output.

[0401] Figure 39 shows the short circuit current of various power generating cells. The samples shown in Figure 39 and Table 3 include various sublayers X in combination with the GO sublayer. Table 3 (below) shows the short circuit current of samples with various first sublayers. The size of the samples operating at 85% RH was 0.25 cm. 2 PSSNa exhibits better water absorption and lower resistance, leading to significantly higher current output. A better water adsorption rate results in a higher current output.

[0402] [Table 3]

[0403] Figure 40 shows the voltage characteristics over time for Sample #1 with a silver (Ag) first electrode and Sample #2 with a zinc plate first electrode. The samples include a bottom electrode of carbon nanotubes (CNT), a first sub-layer of PSSNa, and a second sub-layer of GO. The sample with the zinc plate electrode showed an increased voltage of 1.44 V compared to 0.62 V from the sample with the Ag electrode at 85% relative humidity (RH). By using an active metal as the top electrode, the MEG / battery function can be realized in a single device.

[0404] In Figure 41, Sample 1 includes a single functional layer of PSSNa. Sample #2 includes a first sub-layer of PSSNa and a second sub-layer of GO. Sample #3 includes a first sub-layer of PSSNa and a second sub-layer of acidified GO. The combination of PSSNa and acidified GO can achieve high voltage and current. CNT and Zn as the bottom / top electrodes. The GO film was drop-coated on the CNT. The PSSNa film was a free-standing film on the GO.

[0405] The electrical performance of the samples in Figure 41 is shown in Table 4 below.

[0406]

Table 4

[0407] In Figure 42, the voltages of power generation devices with various second sub-layers are shown. The voltages of devices with a ZN top electrode, a first sub-layer of PSSNa, a CNT bottom electrode, and second sub-layers of MXene, PVA, PAA, and GO are shown. Voltage: MXene (1.18 V) < PVA (1.20 V) < PAA (1.31 V) < GO (1.44 V). GO shows the highest voltage. GO has advantages over other materials due to its rich functional groups.

[0408] Figure 43 shows the voltages across the top layer of various dual-layer moisture power generation devices.

[0409] Figure 44 shows the voltage across various sublayers in the power-generating cell for a cell containing a GO sublayer and a cell containing an acidified GO sublayer. The samples in Figure 44 include a Zn electrode and a CNT electrode.

[0410] The inventors believe that the PSSNa layer functions as a MEG and based on the absorption of water (PSSNa + H2O → PSS- + Na+ (MEG)).

[0411] The inventors believe that the Zn foam electrode functions as a battery and according to Zn+2H2O→Zn2++H2+2OH- (battery).

[0412] The inventors have demonstrated that the GO layer acts as MEG and absorbs water (-COOH → -COO- + H + We believe that it functions based on the Multi-Energy Group (MEG).

[0413] Figure 45 shows the electrical performance of various water-powered cells with various top electrodes. All samples contain PSSNa and GO sublayers and a CNT bottom electrode. The sample with the Zn top electrode shows the highest voltage at 1.4 V. A 2MEG+1 battery is also demonstrated.

[0414] Figure 46 shows the voltage results for other samples. Sample #1 includes a PSSNa sublayer and a GO sublayer treated with plasma or UV. The top electrode is Zn, and the bottom electrode is CNT. Sample #2 is a laminated MEG with a PSSNa and GO dual layer. While GO typically has only low power output at low humidity, PSSNa can function at low humidity. Therefore, the combination of the two materials in a single MEG cell allows for effective function at both low and high humidity. On the other hand, polymers can deform at high humidity, so excess moisture in the polymer should be transferred elsewhere to extend retention. Sample #2 includes a Zn top electrode and a CNT bottom electrode.

[0415] In the example of Figure 47, a single functional layer is placed between an Ag top electrode and a CNT bottom electrode. Different samples were tested using different PSSX polymers. The voltage was H+ It is shown that the cation concentration decreases after substitution with other ions.

[0416] Section 6: MEG device with layered structure and including a hydrogel layer: A high-performance MEG with a bilayer structure is now described, in which a hydrogel layer with hygroscopic LiCl is included to enhance not only the electrical output performance but also the long-term operational durability of the moisture-harvesting device. The hydrogel layer forms the first sublayer of the device's functional layer. Referring to the MEG device structure shown in Figure 36, in the following example, the first sublayer 3632 is a hydrogel layer with hygroscopic LiCl, and the second sublayer (functional layer) 3634 is a graphene oxide layer. The bottom electrode 3620 is carbon nanotubes. The top electrode 3610 is Ni foam. The fabrication process is as follows: A carbon nanotube (CNT) dispersion was coated onto a polyethylene terephthalate (PET) film (1 cm × 2 cm) as the bottom electrode. A GO layer (1 cm × 1 cm) on top of the CNT substrate was obtained by drying 100 μL of 2 wt % GO dispersion at 50 °C. The upper hydrogel layer was obtained by drop-coating the as-prepared hydrogel solution onto the GO layer. After gelation is complete, a piece of Ni foam (0.2 cm x 0.5 cm) is placed on the hydrogel as the top electrode.

[0417] The ionic hydrogel-based MEG (HMEG) demonstrated a continuous open circuit voltage (V) of 0.6 V for over 1400 hours at room conditions. oc ) and can maintain a current of 1.2 mA / cm due to the excellent water retention and mobile ions caused by the designed hydrogel. 2 High short circuit current (I sc ) and 71.7 μW cm -2 The device is less restricted in operating conditions than conventional MEGs and can still generate electricity in harsh environments such as 50°C (15% RH) and -20°C (10% RH). Furthermore, HMEGs can deliver ultra-high voltages of 1.2V at 0% RH for over 10 hours.

[0418] result Power generation performance. The HMEG can function in complex environments (e.g., hot, dry, and cold) and exhibits sustainable power output performance and self-healing (Figures 48(a)-48(c)). The functional layer consists of two sublayers: a GO bottom layer (second sublayer) and a hydrogel top layer (first sublayer) (Fig. 48(d)). The layers are fabricated by a simple drop-coating method. Specifically, the as-prepared hydrogel solution is dropped onto the bottom layer (Fig. 53). The precursor self-gelled through the formation of hydrogen bonds between the hydroxyl groups of PVA and glycerol and coordination bonds between the hydroxyl groups and additional ions (Fig. 54). Unlike deliquescent LiCl powder, the PVA-LiCl hydrogel did not show any physical changes upon exposure to ambient conditions, indicating that it may be suitable for long-term use (Fig. 55). In addition, the formed hydrogel contains abundant water, which keeps the underlying GO hydrated (Fig. 48(d)). As shown in Fig. 48(e), the proposed HMEG exhibited outstanding stability in long-term power performance, maintaining an open-circuit voltage (V) of >0.6 V for over 1400 h. oc ) and was able to generate current continuously for over 140 hours at 45% ± 10% RH. The fluctuations in the electrical signal within the curves are primarily attributed to environmental fluctuations in the ambient conditions during the long-term measurements. The HMEG demonstrates better overall performance (Figure 48(f)). Even more surprisingly, the device is also able to generate electrical signals at high temperature and low humidity (50°C, 15% RH) for over 150 hours (Figure 56).

[0419] Similar to other conventional MEGs, RH is a major factor in the power generation performance of HMEGs. However, HMEGs behave uniquely in response to RH variations. As shown in Figures 49(a) and 49(b), the voltage output is inversely proportional to RH, while higher current output can be achieved by increasing RH. Voltage degradation can be observed when RH is above 65%. Interestingly, the maximum V ocis recorded at 0% RH (Fig. 49(a), Fig. 49(b)), and the voltage gradually reaches and remains above 1 V for more than 10 hours (Fig. 57). On the other hand, dynamic monitoring of the voltage output under varying RH is shown in Fig. 49(c), and it is noted that a small burst of voltage (indicated by the arrow) is observed when RH reaches 85%. This is due to the presence of mobile ions (H + This is due to the momentary accumulation of water within the hydrogel, which promotes the hydrolysis of PVA to RH, thus enhancing device performance in the short term. However, excess ions can lead to the collapse of the ion concentration gradient, resulting in a continuous degradation of performance. As a control experiment, both the current output and voltage output of a device composed of a single GO layer show a positive relationship with increasing RH (Figure 58). In particular, negligible power generation is observed at the harsh condition of 0% RH (Figures 58, 59). Since dry GO layers are essentially free of any water, significant RH does not increase the amount of mobile H + This is required to initiate the ionization of functional groups (e.g., -COOH) within GO to release OH. This result strongly indicates that the hydration state of the GO layer determines device performance. Therefore, an additional layer of ionic hydrogel can significantly assist in hydrating the GO layer at ambient or even extreme conditions (0% RH) due to the abundance of water within the hydrogel.

[0420] Apart from room conditions, measurements are also carried out in a refrigerator and an oven to mimic harsh conditions. The hydrogel not only exhibits anti-freeze properties due to the incorporation of glycerol, but also demonstrates resistance to high temperatures via the addition of LiCl salt (Figure 60). Therefore, the function of the HMEG in generating electricity could be maintained regardless of the environment (Figure 48(a)). Since ion migration is affected by temperature, the device performance changes in the corresponding environment. In particular, ion migration becomes stronger at high temperatures (Figure 61), and therefore the HMEG exhibits a higher V of 0.7 V and 340 μA in the oven (50 °C). oc and short circuit current (I sc) respectively. Although the ion mobility at subzero temperatures is significantly lower than that at room temperature, the device can still generate a voltage of 0.4 V with a current output of 75 μA at -20 °C (Figure 49(d)). In addition, excellent self-healing properties are also demonstrated in the HMEG to meet the demands of cycling. Especially for applications in hot and dry regions, weight loss of the hydrogel is inevitable due to water evaporation. Recovery of lost components is a critical factor for performing cycling functions. Therefore, the pristine HMEG was measured in ambient and oven environments to evaluate the cycling potential of the device. As shown in Figure 49(e), the weight of the device decreases after each cycle of dehydration in the oven. Regardless of the thickness of the coated hydrogel, all HMEGs exhibit the ability to recover weight by absorbing ambient moisture. Such self-healing properties benefit from the excellent water absorption ability of the hydrogel. In addition to weight recovery, the current also shares a similar trend in recovery upon absorbing moisture, as shown in Figure 49(f). The recovery capacity is enhanced by a higher concentration of hygroscopic LiCl salt. 100% compensation of water content and 80% recovery of current output are achieved with HMEG-4.8% LiCl due to its excellent water absorption. With respect to HMEG-0% LiCl, its lower water absorption capacity limits current recovery, making it unsuitable for long-term use. Furthermore, detachment from the substrate is observed with HMEG-0% LiCl (Figure 62), while gels with a higher concentration of LiCl (7.2%) remain highly tacky and wet after one day. Therefore, a concentration of 4.8% LiCl is selected for all experiments. The introduction of LiCl serves to endow the hydrogel with improved water absorption capacity, which will be further discussed in relation to the following section. Meanwhile, the fluctuation of the output voltage shows a stable trend over three operating cycles, indicating good stability under various conditions (Figure 63). Water retention capacity is also greatly improved by the addition of LiCl salt. While only 65% ​​weight was retained in HMEG-0% LiCl after 14 days, the device with 4.8% LiCl was able to retain its weight in ambient conditions (Figure 64). This superior water retention allowed the device performance to be maintained over time.As shown in Figure 2(g), HMEG-4.8%LiCl was stored and exposed to ambient conditions without sealing for 4 months (120 days), but no obvious degradation was observed (approximately 96% retention), demonstrating outstanding stability in power generation.

[0421] The power output of the HMEG was further evaluated under various external loads. As shown in Figure 2(h), as the load resistance increases from 1 Ω to 2.5 MΩ, the voltage output increases while the current output decreases to 71.7 μW / cm. 2 The maximum power density was achieved at a load resistance of 4670 Ω (Figure 65), which is an optimal result compared with most inorganic-based MEGs in recent reports (Figure 2(i) and Supplementary Table 1).

[0422] Influence Factors on Output Performance. As mentioned above, the device was designed with a bilayer structure, each with a bottom layer of GO and an upper layer of PVA-LiCl hydrogel. It should be noted that devices consisting of a single GO layer or a single hydrogel layer exhibit a gradual deterioration of voltage output and are certainly not applicable for long-term use (Figure 66). One of the reasons may be the lack of control over ion diffusion. Because the hydrogel with LiCl has a significant water absorption capacity, the ion concentration gradient across the hydrogel can easily collapse over time. Herein, a bilayer structure with stable output is proposed, in which the hydrated GO layer with negative charge nature acts as a screening layer for positively charged mobile ions (e.g., H +) to attract the ions. In this case, the effect of layers on HMEG performance was investigated. Regarding the bottom GO layer, the layer thickness can be controlled by varying the volume of GO solution. The effect of GO layer thickness on voltage is not as clear as its effect on current output, as shown in Figure 50(a). The voltage remains above 0.6 V with various layer thicknesses. Generally, the device voltage is governed by the ion concentration gradient between the top and bottom surfaces of the device. Because the bottom GO layer is fully hydrated due to the added hydrogel, the ion concentration gradient within the GO layer is not significant regardless of GO thickness. Instead, the device current significantly increases with thicker GO layers, saturating at approximately 120 μA. This may be due to the greater dissociation of mobile ions from functional groups in thicker GO films. However, a degradation in current was observed with further increase in GO thickness, which is attributed to the longer migration distance of mobile ions. Meanwhile, the thickness of the hydrogel layer was also investigated. Similar to the GO layer thickness, the hydrogel thickness increases with the number of charge carriers (e.g., Li) in the thicker hydrogel. + ) has a larger effect on the current output (Figure 67).

[0423] In addition, the concentration of added salt also plays an important role in device performance. The presence of ionic salt provides the HMEG with mobile ions that can act as a medium for enhancing the ion concentration gradient across the device. Therefore, the HMEG has a higher voltage output than a device without ionic salt, as shown in Figure 50(b). Notably, these free ions significantly enhance the hydrogel's conductivity. The device resistance obtained from EIS measurements reflects that the hydrogel with 0% LiCl has a resistance 10 times higher than that with 1.2% LiCl (Figure 50(c)). Increasing the concentration to 4.8% (selected as the optimal concentration for this fabrication) further reduces the hydrogel's resistance. The reduced resistance promotes iontophoresis and enhances the device's current output. Therefore, a significant current signal (approximately 120 μA) was recorded when 4.8% LiCl was employed in the HMEG (Figure 50(b)). Furthermore, the water absorption capacity of the hydrogel is also improved by adding salt. Benefiting from its hygroscopic properties, LiCl can significantly absorb moisture and bind with water molecules. Regardless of the concentration of added LiCl, the dehydrated HMEG also demonstrated its ability to absorb water from humidity (Figure 50(d)). However, there was a clear increase in performance (directly proportional to the concentration of added salt), with the water absorption of the optimized design being three times higher than that of the salt-free hydrogel and pure GO (Figures 50(d) and 68). The enhanced water absorption ability is beneficial for realizing the proposed recovery function of HMEG, which promotes water recovery for recharging electrical performance.

[0424] However, as shown in Figure 50(e), a higher weight loss is seen in the hydrogel with a higher ion concentration after settling at 50°C. This is because there are more ions available to interact with water molecules within the hydrogel during the gelation process, resulting in more water pooling (Figure 69). Conversely, less water is present in the low-concentration hydrogel, indicating less water is evaporated during operation. Generally, there are three states of water within a hydrogel: bound water, free water, and intermediate water. Water that forms strong hydrogen bonds with the polymer chains refers to bound water, which requires the highest activation energy to break the bonds before escaping the hydrogel. 47 While free water naturally behaves as bulk water, intermediate water is water with weakly hydrogen-bonded or non-hydrogen-bonded water molecules. 48 Such a water state can be characterized by tracing the OH bond using Raman spectroscopy. As shown in Figure 50(f)(i), the peak at 3515 cm -1 and 3630 cm -1 The Raman shift of σ indicates the presence of intermediate water within the hydrogel. As previously mentioned, the addition of salt can form complexes with the polymer chains, reducing the formation of hydrogen-bonded water and thereby increasing the amount of intermediate water. 50 In other words, the amount of intermediate water in the hydrogel is proportional to the salt concentration. Due to its poorly bound nature, the intermediate water has been reported to evaporate with minimal energy demand. 51 For this reason, a larger amount of water loss can be seen in hydrogels with higher salt concentrations. This difference, as revealed by the Raman spectra of the hydrogels, also shows good agreement with the results of previous studies. The intermediate water ratio increases from 17.9% to 25.6% when 4.8% LiCl is introduced into the pure PVA-glycerol matrix (Figure 50(f)(ii) and Figure 70). Despite the weight loss due to water evaporation at high temperatures, the ionic hydrogel demonstrates its ability to recover weight by capturing water, as shown in Figure 50(e). Higher efficiency in recovering water can be obtained by increasing the ion concentration, which is a prerequisite for effective electrical regeneration.

[0425] The influence of the type of hygroscopic salt should also be emphasized, as two other common hygroscopic salts, NaCl and KCl, are added to the system. Like Li, Na and K are also identified as group 1 alkali metals. As shown in Figure 3(g), HMEG with LiCl has the best performance in water absorption, followed by NaCl and KCl in that order. This is because Na + and K. + Compared to Li + This can be attributed to the highest degree of hydration of Na, which results from the smaller hydrated ionic radius (Supplementary Table 2), and therefore more water molecules can be surrounded by the ion. In addition, the smaller hydrated ionic radius is also responsible for the higher hydration of Na compared to Li. + and K. + Therefore, the device with lithium ions exhibits the highest current output, while the device with Na + and K. + The ions were observed to follow this order (Figure 50(h)). The voltage performance among various ionic hydrogels also shares a similar trend with corresponding water absorption capacities (Figure 50(h)). The poorer water absorption capacities of the KCl and NaCl hydrogels inhibit the dissociation of mobile ions, thus limiting the ion concentration gradient across the device.

[0426] The electrode size was investigated because the top electrode acts as a current collector, which reflects the effective working area. As shown in Figure 67(c), the current output was demonstrated to be proportional to the effective working area of ​​the electrode, and the current output was found to be 0.04 cm 2 1cm from 2 The current increases from about 80 μA to about 1 mA with increasing electrode size to 1.5 V. In contrast, the voltage is less dependent on the electrode size and still remains around 0.6 V. Furthermore, the type of electrode material also plays an important role in determining the device performance (Figure 71). A symmetric structure is constructed by designing both the top and bottom electrodes with CNT sheets, and materials different from CNT (e.g., Ni, Ag, and Cu) are also employed to develop an asymmetric structure. The symmetric structure exhibits a V of 0.35 V at ambient conditions. ocThe generated electrical signal from the control design also verified that the electricity was induced by ion diffusion dissociated from the functional material in the HMEG (stimulated by moisture from the environment). Regarding the asymmetric structure, the HMEG with Ni electrodes performed best among the selected metal electrodes, followed by Cu and Ag in that order (Figure 2(a)). The difference in electrical output can be attributed to the difference in work function between the two electrodes (Ni, 5.35 eV; Cu, 4.94 eV; Ag, 4.74 eV). Specifically, Schottky contacts are formed with the various electrodes within the device, thereby restricting ion migration to a unique direction. Therefore, the larger the work function difference, the better the electrical output can be obtained.

[0427] Mechanism of hydrogel formation. FTIR spectroscopy was employed to analyze the molecular interactions within the hydrogel (Figure 51(a)). One of the characteristic peaks of PVA is at 3293 cm, which corresponds to the stretching vibration of the hydroxyl group (-OH). -1 1422 and 2925 cm -1 The characteristic peaks at are related to the -CH and -CH stretching vibrations, respectively. Contrary to the other characteristic peaks, the wavenumber of the -OH peak shifts to 3273 cm with the addition of LiCl. -1 This indicates a strong interaction between the added ions with the polymer group. In particular, Li + The ions could form complexes with the hydroxyl groups through coordinate bonds. In this way, partial Li + The ions are attached to the polymer chains to help form a hydrogel. The XRD pattern in Figure 51(b) also shows the Li ions from the hydroxyl groups of the PVA and the hygroscopic salts. + The diffraction peaks at approximately 19° and 20° correspond to the interaction between the PVA ions.

number

number

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[0428] Proposed mechanism for power generation. During the fabrication process, the hydrogel solution was drop-coated directly onto the GO layer, resulting in the formation of interfacial hydrogen bonds between the two layers. Due to the great hydrophilicity of GO, water molecules in the hydrogel solution could easily hydrate and penetrate the GO layer. Meanwhile, oxygen-containing functional groups (e.g., -OH and -COOH) in the GO layer could absorb water and form mobile H + The hydrated GO nanosheets could be dissociated into ions and immobile frameworks. Therefore, hydrated GO has a negatively charged nature and shows potential in trapping counterions. On the other hand, the hydration process increases the interlayer spacing between GO nanosheets, thereby promoting ion separation and allowing more ions to migrate out of the hydrogel. XPS measurements were performed to investigate the elemental composition of the underlying GO, as shown in Figure 51(d) and Figure 72. The peaks at approximately 55 eV and 198 eV correspond to Li1s and Cl2p, respectively. The Cl2p peak is stronger than Li1s, which indicates more Cl + This observation further suggests that Li ions are detected within the GO layer. + Formation of coordinate bonds between ions and hydroxyl groups (partial Li + In contrast, Cl + The ions are not bonded to the functional groups of PVA, and therefore Cl - is the Li in the GO layer + In addition, EDS mapping also confirmed the presence of Cl element in the GO layer, and Cl from the hydrogel to the GO layer. - This reveals the penetration of ions (Figure 73). Taking all these factors into consideration, it was indicated that the deposited hydrogel layer could hydrate the GO layer and leave ions as residues. To determine the involvement of residual ions, the power performance of the pristine GO layer and that of the ion-containing GO layer were compared at 45% RH. The ion-containing GO layer was obtained by peeling it off from the ionic hydrogel, and clear hydration signatures were observed on the GO layer (Figure 74(a)). The voltage of the ion-containing GO layer increased from 0.4 V to 0.6 V, while the current was five times higher, reaching 1 μA (Figure 74(b)). It was found that the residual ions promoted the performance of the GO layer. Details will be discussed in the corresponding context below.

[0429] Similar to conventional MEGs, the generated ion concentration gradient governs power generation in HMEGs. Mobile ions in HMEGs migrate from the top to the bottom of the device under the concentration gradient, inducing a potential difference. Conversely, electrons are collected at the top electrode (representing the generation of current). However, HMEGs performed differently from other MEGs in that they exhibited a positive correlation with RH. The underlying mechanism of HMEGs could be explained by the following three different states, depending on the RH conditions, as shown in Figure 51(f).

[0430] i) At ambient conditions (e.g., 45% RH), the hydroxyl groups in PVA will convert to mobile H + The mobile H from the hydrogel could be dissociated into ions and immobile O skeletons. + Ions can hop through interfacial hydrogen bonds driven by the Grotthuss mechanism, while immobile O groups can hop to hydrated Li via the formation of complexes. + It can support the hopping migration of ions, significantly increasing the conductivity of the hydrogel. Regarding the role of the overhydrated bottom GO layer, dissociated H from GO + The ions have limited contribution to the overall voltage because an ion concentration gradient is weakly established across the overhydrated GO layers. Instead, the dissociated free ions contribute to the improved current output. In this situation, the residual Li in the GO layers + ions serve as additional mobile ions (whose diffusion is guided by the negatively charged surface of hydrated GO) to migrate throughout the GO layer. - Ions also accumulate within the GO layers, helping to build a larger potential difference across the device. Furthermore, the increased interlayer spacing of the hydrated GO layers presents larger nanochannels for enhanced ion transport. The combined effect of the higher potential difference and faster ion diffusion increases the power output of the device at room conditions.

[0431] ii) In a water-rich scenario (e.g., 85% RH), the excellent hygroscopic capacity of ionic hydrogels allows large amounts of water to be harvested from the environment. Initially, the surface exposed to water is exposed to H+ This could explain the short-term voltage increase observed at 80% RH. With increasing time, excess water is retained within the hydrogel, resulting in extensive H + Ions accumulate throughout the hydrogel layer while the underlying GO remains hyperhydrated. In this regard, the device lacks an ion concentration gradient, leading to a continuous degradation of the output voltage (Figure 2(c)).

[0432] iii) In a low-humidity environment (e.g., 0% RH), the voltage of the HMEG was observed to gradually increase rather than decrease, as in other reported HMEGs. CV measurements were first performed to rule out the possibility that the voltage increment was caused by an electrochemical reaction. The CV curves reveal that no significant electrochemical reaction occurs regardless of RH (Figure 75(a)). Furthermore, the top Ni electrode is replaced by an Ag plate, whose reactivity is less intense than that of Ni. As shown in Figure 75(b), the voltage of the HMEG with the Ag electrode is similar to that of the device with Ni and gradually increases even at 0% RH. The voltage of each individual layer is measured by a Ni electrode, as shown in Figure 51(e). The voltages of the GO and hydrogel layers are 0.62 V and 0.6 V, respectively. The device with a bilayer structure exhibits a voltage of approximately 1.2 V, which is the composite voltage of the series-connected hydrogel and GO device. Note that the water in the hydrogel tends to evaporate to reach equilibrium in a low-RH environment. The water molecules and Li + The bonds between ions are broken in this case, allowing the water molecules to evaporate spontaneously. It has been reported that ions bound to more water molecules have lower ionic hydration energy. During water evaporation, ions at the air-exposed interface are activated due to the loss of bound water molecules, and their ionic hydration energy is greater than that of ions at the bottom region of the hydrogel. The momentum of ion migration arises from this energy difference. The ions (Li + ) is released from the hydrolysis of PVA hydroxyl groups at 45% RH. +In contrast, the ability of the device with 0% LiCl to generate electricity is significantly greater than that of the mobile LiCl at 0% RH. + Due to the lack of ions, the hydrogel layer containing LiCl was able to retain its output even at 0% RH. On the other hand, the LiCl released from the ionic hydrogel + The number of ions increases over time, which can be reflected in a continuous increase in the output voltage. For control experiments, HMEG sealed with a waterproof membrane and HMEG with 0% LiCl were measured at 0% RH, respectively. As shown in Figure 51(g), both HMEGs exhibit a stable voltage at only 0.5 V (similar to that at ambient conditions (45% RH)), instead of increasing to over 1 V in the unsealed HMEG with 4.8% LiCl. For the sealed HMEG, water evaporation from the hydrogel is prevented while water is stored within the sample, providing an ambient environment to maintain device performance at 0.5 V. Despite water evaporation from the unsealed HMEG-0% LiCl, negligible improvement was observed, further confirming that the added salt is also important to function as a charge carrier donor when water evaporation occurs. Considering all these, while water evaporation affects the electrical signal, the introduced salt dominates the voltage increment at 0% RH.

[0433] Apart from the hydrogel, the GO layer at this condition contributes to the overall power performance with similar properties to the ion-containing GO at 45% RH (Fig. 74(b)). First, the aforementioned residual ions in the GO layer are responsible for increasing the corresponding voltage from 0.4 V to 0.6 V (Fig. 51(e)). Water evaporation at 0% RH could alleviate the over-hydration state of the GO layer. Instead of functioning as an iontophoretic pathway at ambient conditions, the GO layer acts as a proton donor and is reactivated at low humidity conditions to expand the potential difference, resulting in an increase in power performance.

[0434] Applications of HEMGs. Despite the significant output of a single unit, the total power output needs to be further enhanced to drive commercial electronic devices. The simple fabrication of this workpiece provides the feasibility of scaling up the device to increase electrical output. As shown in Figure 52(a), two devices connected in series were able to generate 1.2 V, doubling the output voltage. This voltage could be further increased by connecting more units, demonstrating a linear relationship with the number of devices (Figures 52(a) and 52(b)). Furthermore, a large-scale connection of 168 units was realized in series on a flexible PET substrate (210 mm × 297 mm) and was able to output a total voltage of approximately 97 V (Figures 5(b) and 5(c), Figure 76(a)). More importantly, the large-scale device exhibited a voltage retention of over 95% during mechanical bending, indicating its great potential as a power source for wearable electronic devices (Figure 77). The "UNSW" pattern designed with 39 LEDs could be directly illuminated by the power supplied by 168 HMEGs (Fig. 52(d) and Fig. 76(b)). Commercially available capacitors could also be employed to store the generated electricity for use on other electronic devices. A 100 μF capacitor and a 470 μF capacitor could be charged to 0.58 V (1 unit) and 30 V (168 units), respectively, at ambient conditions (Fig. 52(e)). In addition, the stored power could be used to generate pulse trains to realize the typical enhanced behavior of synaptic devices (Fig. 52(f)). Furthermore, the charged capacitors could be used to power electronic devices such as smart windows and e-ink screens to display blueprints (Fig. 52(g)). A schematic diagram of the circuit for an MEG-powered e-ink display is shown in Fig. 78.

[0435] essay In summary, we report a high-performance hydrogel-based moisture generator (HMEG). The as-fabricated device generates 1.2 mA / cm at room conditions. 2 Ultra High I sc It can generate a V of 0.6V. ocThe device was able to generate V continuously for over 1400 hours. The device showed the potential to function over a wide range of environmental temperatures (-20°C to 50°C) and RH (0% to 85%), demonstrating its all-weather operativity. In contrast to conventional MEGs, the proposed HMEG provides high voltage at low humidity, achieving a sustainable V of 1.2V. oc was recorded at 0% RH. Due to the abundant water inside the hydrogel, this device may have little dependence on ambient RH; a decrease in RH could cause water evaporation within the hydrogel, enhancing device performance at 0% RH. Furthermore, the exceptional water absorption capacity of the LiCl-containing hydrogel also endowed this device with the ability to recover water loss by absorbing ambient water. This feature contributes to the advantages of cyclic use of the proposed HMEG. Using simple fabrication, a high voltage of 97 V was demonstrated by scaling up the number of cells in series, and this voltage could be maintained after mechanical bending. These excellent properties of the HMEG enable it to be a promising and sustainable power source for a variety of electronic devices. This study also provides insights into moisture power generation and future device design.

[0436] method material Polyvinyl alcohol (PVA, #P1763), glycerol (#G5516), lithium chloride (LiCl), and graphene oxide (GO) were provided by Sigma-Aldrich. Nickel (Ni) foam, silver (Ag), and copper (Cu) plates were purchased. Commercially available carbon nanotube paste was not further processed, while deionized water was collected from a Milli-Q water purification system.

[0437] Synthesis of hydrogels A 15 wt% pure PVA solution was obtained by dissolving PVA powder in DI water at 95°C under magnetic stirring. Once a clear and bubble-free PVA solution was collected, 20 wt% glycerol was added for further stirring. Finally, LiCl powder was blended with the as-prepared mixture to obtain a PVA-LiCl hydrogel solution. Various amounts of LiCl (0, 1.2, 2.4, 4.8, and 7.2%) were added into the system.

[0438] Fabrication of HMEG A carbon nanotube (CNT) dispersion was coated onto a polyethylene terephthalate (PET) film (1 cm × 2 cm) as the bottom electrode. A GO layer (1 cm × 1 cm) on top of the CNT substrate was obtained by drying 100 μL of a 2 wt% GO dispersion at 50 °C. The upper hydrogel layer was obtained by drop-coating the as-prepared hydrogel solution onto the GO layer. After gelation was complete, a piece of Ni foam (0.2 cm × 0.5 cm) was placed on the hydrogel as the top electrode.

[0439] Characterization Before characterization, HMEG was dried in a vacuum oven for 12 hours to eliminate water content within the hydrogel. Fourier transform infrared spectroscopy (FTIR, PerkinElmer Spectrum 100) was performed to investigate the interactions between additives and functional groups. The morphology of HMEG was observed using a scanning electron microscope (SEM, FEI Nova NanoSEM 450). An Autolab (PGSTAT302N) workstation was employed for electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) measurements. The state and amount of water within the hydrogel was evaluated using a Raman spectrometer (Renishaw inVia Reflex) at a wavelength of 532 nm. The elemental composition of HMEG was analyzed by energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). An X-ray diffractometer (XRD) with a Cu Kα radiation source (λ = 1.5418 Å) was employed to analyze the crystallinity of the hydrogel at a scanning rate of 2° / min.

[0440] Water absorption capacity The as-formed hydrogels were dried in an oven (50°C, 15% RH) to remove the internal water content before measuring the water absorption capacity. The dried hydrogels were then set at 45% RH for water absorption. The water absorption capacity was then calculated as follows, where W a , W f and W i represent the water absorption capacity, the weight of the hydrogel after absorption at the corresponding time, and the initial weight of the dry hydrogel, respectively.

number

[0441] Electrical Performance Measurements The electrical output of the device was measured using a Keithley 2400 source meter. The source voltage was set to 0 V when measuring the short-circuit current. Conversely, the open-circuit voltage was measured with a source current of 0 A. The relative humidity was controlled by a flow of N2 through a DI water chamber. To perform cyclic measurements, the sample was connected to the source meter and placed in an oven with a set temperature and RH of 50 °C and 15%. After one cycle of measurements in the oven, the sample was reset in ambient conditions (25 °C and 45%) to absorb moisture and achieve a recovery phase, followed by recording the instantaneous voltage. For subzero temperature measurements, the device was placed in a refrigerator for 10 minutes to reach equilibrium conditions before measurement.

[0442] Where any prior art publication is referred to herein, it will be understood that such reference does not constitute an acknowledgement that the publication forms part of the common general knowledge in the art in Australia or any other country.

[0443] Some features described in some examples and examples above may be used with other specific examples (eg, electrodes).

[0444] In the claims that follow and in the preceding description of the invention, unless the context otherwise requires to indicate language or a necessary implication, the term "comprises" or variations thereof is used in an inclusive sense, i.e., to specify the presence of stated features and not to exclude the presence or addition of other features in various embodiments of the invention.

[0445] It will be understood that the above description refers only to preferred embodiments of the invention, and that variations and modifications to the several exemplary embodiments of the invention are possible without departing from the spirit and scope of the invention, the scope of which is determined from the claims that follow.

Claims

1. a first electrode and a second electrode; a functional layer disposed between the first electrode and the second electrode, the functional layer emitting charge carriers; A moisture power generation device comprising: The functional layer includes at least two sublayers, the first sublayer acts as a moisture reservoir for the second sublayer to provide moisture to the second sublayer; A moisture harvesting device, wherein the second sublayer generates charge carriers in response to moisture available from the first sublayer.

2. The moisture-power generating device of claim 1 , wherein the first sublayer comprises a polymer.

3. The moisture power generation device according to claim 1 or 2, wherein the first electrode, the second electrode, and the functional layer are configured in a stacked arrangement.

4. The moisture power generating device of any one of claims 1 to 3, wherein the sub-layers are arranged in a stacked configuration to form the functional layer.

5. The moisture power generation device according to any one of claims 1 to 4, wherein the first and second sublayers are adjacent sublayers within the functional layer.

6. The moisture power generation device of claim 1 , wherein the first sublayer releases charge carriers when the moisture power generation cell is exposed to moisture.

7. The moisture power generating device of any one of claims 1 to 6, wherein the second sublayer has a net charge that is opposite to the charge of the charge carriers in the first sublayer.

8. The moisture power generating device of any one of claims 1 to 7, wherein the second sub-layer comprises a carbon-based material.

9. The moisture power generation device according to claim 1 , wherein the second sublayer comprises graphene oxide.

10. 10. The moisture power generation device of claim 1, wherein the second sublayer is configured to be positioned between the first layer and the second electrode, the second layer having a top surface facing towards the first sublayer and a bottom surface facing towards the second electrode, and the moisture power generation device is configured to resist ingress of moisture into the bottom surface of the second sublayer.

11. The moisture power generation device according to any one of claims 1 to 10, wherein the second electrode is insulating against moisture.

12. The moisture power generating device of any one of claims 1 to 11, wherein the second sublayer is adjacent to the second electrode and electrically connected to the second electrode.

13. The moisture power generating device of any one of claims 1 to 12, wherein the first sublayer comprises an ionic salt.

14. A moisture-power generating device according to any preceding claim, wherein the first sublayer comprises a hydrogel.

15. The moisture power generating device of any one of claims 1 to 14, wherein the first sublayer is doped with charge carriers.

16. A moisture power generating device according to any preceding claim, configured to absorb moisture from the environment and whose electrical performance improves in more humid environments.

17. a first electrode and a second electrode; a functional layer that emits charge carriers to the first and second electrodes; a layer that functions as a moisture reservoir to provide moisture to the functional layer; Includes a moisture-generating device.

18. The moisture power generation device of claim 17 , wherein the layer that functions as a moisture reservoir for providing moisture to the functional layer is disposed between the first electrode and the second electrode.

19. 19. The moisture power generation device of claim 17 or 18, wherein the functional layer comprises at least two sublayers, a first sublayer that functions as a moisture reservoir, and a second sublayer that provides charge carriers when provided with moisture.

20. A moisture power generation device, comprising: a first electrode and a second electrode; a functional layer disposed between the first electrode and the second electrode, the functional layer releasing charge carriers when the power-generating cell is exposed to moisture; Including, the functional layer includes at least two sublayers, the sublayers being stacked between the first electrode and the second electrode (and adjacent layers being electrically connected); A moisture power generating device wherein one of the sublayers is a polymer sublayer.

21. 21. The moisture power generation device of claim 20, wherein the polymer sublayer acts as a moisture reservoir for adjacent sublayers when the power generation cell is exposed to moisture.

22. A moisture power generation device, comprising: a first electrode and a second electrode; a functional layer disposed between the first electrode and the second electrode, the functional layer releasing charge carriers when the power-generating cell is exposed to moisture; Including, the functional layer includes at least two sublayers, the sublayers being stacked between the first electrode and the second electrode (and adjacent layers being electrically connected); A moisture power generating device, wherein one of the sublayers, which is a polymer sublayer, acts as a moisture reservoir for an adjacent sublayer when the power generating cell is exposed to moisture.

23. A power-generating cell including a first electrode, a second electrode, and a functional layer located between the first electrode and the second electrode, wherein the functional layer releases charge carriers when the power-generating cell is exposed to moisture.

24. 24. The power generating cell of claim 23, wherein the functional layer includes at least two sublayers, the sublayers are stacked between the first electrode and the second electrode, and adjacent sublayers are electrically connected.

25. 25. The power generating cell of claim 23 or 24, wherein each of the sublayers releases charge carriers when the power generating cell is exposed to moisture.

26. 26. The power generating cell of claim 24 or 25, wherein each of the sublayers comprises a different material.

27. The power generating cell according to any one of claims 24 to 26, wherein a first of the sublayers is a polymer sublayer.

28. 28. The power generating cell of claim 27, wherein the polymer sublayer is one of PSSA, PSSNa, PAA, PVA, PSSLi, PSSK, PSSNH4, PSSMg2, PSSAl3, and PSSH.

29. 29. The power generating cell of any one of claims 24 to 28, wherein a second of the sub-layers comprises one of MXene, MXene oxide, PVA, PAA, and GO.

30. 30. The power generating cell of claim 29, wherein the second of the sublayers is adjacent to the first polymer sublayer.

31. The power generating cell of any one of claims 24 to 30, wherein a second of the sublayers comprises a carbon-based material that releases charge carriers when exposed to moisture.

32. 32. The power generating cell of claim 27, wherein the first of the sublayers, which is a polymer sublayer, is adjacent to and electrically connected to the first electrode.

33. The power generating cell according to any one of claims 23 to 32, wherein the first electrode is porous to moisture.

34. The power generating cell according to any one of claims 23 to 33, wherein the first electrode comprises Ag, Zn, a Zn plate, a Zn foam, Al, Mg, Cu, Ni, Fe, or Ti.

35. The power generating cell according to any one of claims 24 to 34, wherein the second of the sublayers is adjacent to and electrically connected to the second electrode.

36. The power generating cell according to any one of claims 24 to 35, wherein the second electrode is insulating against moisture.

37. The power generating cell according to any one of claims 24 to 36, wherein the sublayers have different moisture absorption properties.

38. The power generating cell according to any one of claims 24 to 37, wherein the moisture absorption properties of the sublayers decrease from the sublayer adjacent to the first electrode to the sublayer adjacent to the second electrode.

39. The power generating cell according to any one of claims 24 to 38, wherein a first of the sublayers, which is a polymer layer, functions as a moisture reservoir for adjacent sublayers when the power generating cell is exposed to moisture.

40. The power generating cell according to any one of claims 23 to 39, wherein the first electrode exhibits an electrochemical reaction when in contact with moisture.

41. The power generating cell according to any one of claims 23 to 40, wherein the first electrode comprises at least one active metal: Al, Cu, Ni, Al, Zn, Zn foam, Mg, Fe, or Ti.

42. The power generating cell according to claim 23 , wherein the functional layer comprises PSSNa.

43. A power-generating cell including a first electrode, a second electrode, and a functional layer located between the first electrode and the second electrode, wherein the functional layer releases charge carriers when the power-generating cell is exposed to moisture, and the functional layer includes at least two sublayers, each sublayer being stacked between the first electrode and the second electrode; A power generating cell, wherein each of the sublayers releases charge carriers when the power generating cell is exposed to moisture, and a first of the sublayers is a polymer sublayer and is electrically connected to an adjacent sublayer.

44. 44. The power generating cell of claim 43, wherein the first of the sublayers is PSSNa.

45. 45. The power generating cell of claim 43 or 44, wherein one of the sublayers is electrically connected to the second electrode and comprises GO.

46. A power generating cell including a first electrode, a second electrode, and a functional layer located between the first electrode and the second electrode, wherein the functional layer releases charge carriers when the power generating cell is exposed to moisture, and the functional layer includes PSSNa.

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