Method for regulating and controlling performance of paper-based microfluid fuel cell based on papermaking technology

Abstract

The invention discloses a method for regulating and controlling the performance of a paper-based microfluid fuel cell based on a papermaking technology, and relates to the technical field of paper-based microfluid fuel cells. The pore structure of the paper base is improved by using a papermaking technology, so that the paper base is more beneficial to capillary flow of electrolyte, diffusion and transportation of reactants and conduction of ions among electrodes, and commercial filter paper widely applied to the existing PMFC is replaced, so that the problem of low performance of the PMFC caused by slow liquid absorption speed and large ohmic resistance of the paper base is solved, and the service life of the PMFC is prolonged. The mass transfer and electric conduction requirements of the PMFC are met, a structural basis is provided for improving the performance of the PMFC, and the power output of the PMFC is improved. The papermaking technology and the PMFC are combined, and the method has wide application prospects and practical value.

Description

Technical Field

[0001] The invention relates to the technical field of paper-based microfluid fuel cells, and in particular to a method for regulating the performance of paper-based microfluid fuel cells based on papermaking technology. Background Art

[0002] Microfluidic fuel cells utilize the laminar flow characteristics of microfluidics to allow two electrolyte solutions containing fuel or oxidant to be naturally stratified without the need for expensive polymer electrolyte membranes for isolation. This design eliminates the complex water and heat management issues in polymer membrane fuel cells, greatly reduces manufacturing costs, improves design flexibility, and broadens the range of fuel options. However, traditional microfluidic fuel cells still require external pumps to drive the flow of electrolyte solutions, which inevitably increases the complexity of the system. In addition, its low energy density is also an issue that urgently needs to be addressed.

[0003] In recent years, research on paper-based microfluidic fuel cells (PMFCs) has gradually come to the forefront. This type of fuel cell usually uses filter paper as a substrate to carry electrodes, current collectors and electrolyte solutions. It has the advantages of small size, light weight, strong flexibility, and is easy to integrate into small detection systems, such as medical test strips for blood sugar and pregnancy tests, and various wearable devices. In addition, paper is biodegradable, low cost, and can be easily folded to change its shape and structure. At the same time, as a substrate for delivering electrolytes, the porous fiber structure of paper allows the electrolyte to flow inside it by capillary action, thus eliminating the need for external pumps. These advantages make PMFCs highly applicable, especially in small portable electronic devices, which can further reduce the size of the device, making it more environmentally friendly and more convenient to use. However, at present, the power output of PMFCs is still generally low.

[0004] So far, most of the research on improving PMFC power output has been done by connecting multiple single cells in series or in parallel. Although this method can effectively increase the battery output, the complexity of the overall structure of the device also increases. The performance of a single PMFC has long been limited by the low liquid absorption rate of commercial filter paper, resulting in insufficient fuel supply on the anode side and hindered ion conduction between electrodes, which is mainly attributed to the unoptimized pore structure of commercial filter paper.

[0005] Therefore, being able to effectively and cost-effectively increase the power output of a single PMFC cell is a technical problem that needs to be solved at present. Summary of the invention

[0006] The purpose of the present invention is to provide a method for regulating the performance of paper-based microfluidic fuel cells based on papermaking technology, aiming to improve the pore structure of the paper substrate through papermaking technology, replace the commercial filter paper widely used in existing PMFCs, and thus improve the power output of PMFCs.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a method for preparing a paper-based microfluidic fuel cell based on papermaking technology, comprising the following steps:

[0009] (1) Preparation of paper-based materials:

[0010] a. preparing pulp; b. filtering out water from the pulp to achieve preliminary forming of paper; c. drying the paper; d. flattening the paper to obtain the paper base material;

[0011] (2) Preparation of paper-based microfluidic fuel cells:

[0012] The paper-based material prepared in step (1) is processed into a predetermined shape, and the battery assembly is fixed on the surface of the paper-based material to prepare a paper-based microfluidic fuel cell.

[0013] Furthermore, the pore structure of the paper-based material is regulated by adjusting the stirring time during the pulp preparation process.

[0014] Furthermore, the pore structure of the paper-based material is regulated by adjusting the fiber surface density.

[0015] Furthermore, the pore structure of the paper-based material is regulated by adjusting the pressure of the flattening treatment.

[0016] Furthermore, the stirring time for preparing the pulp is 1-15 min, more preferably 6 min; the concentration of the pulp is 0.83-6.67 mg / ml, more preferably 3.33 mg / mL; the fiber surface density of the paper-based material is 0.01-0.08 g / cm 2 , more preferably 0.04 g / cm 2 ; The pressure of the paper flattening process is 1-2.5MPa, more preferably 1MPa.

[0017] Furthermore, the method for preparing pulp includes chemical method, mechanical method, chemical-mechanical method, semi-chemical method or waste paper pulping; the method for filtering out moisture includes flat mesh filtration, pressed mesh filtration, round mesh filtration, screen filtration or filter cloth filtration; the method for drying paper includes natural drying, high temperature drying or freeze drying; the method for smoothing paper includes cold pressing, hot pressing or ironing.

[0018] Furthermore, the paper-based material is a multi-layer composite material.

[0019] Furthermore, the method for preparing the multilayer composite material comprises the following steps:

[0020] a. Prepare pulp to obtain pulp with different fiber lengths:

[0021] b. Pulps with different fiber lengths are added to the filter device respectively, the water in the paper is filtered out to obtain wet paper, and then the different wet papers are stacked to form a multi-layer structure. After that, they are pressed with a pressing plate in the filter device to discharge the remaining water and ensure the close fit between different layers, so as to achieve the preliminary formation of the multi-layer structure of the paper;

[0022] c. Paper drying;

[0023] d. The paper is leveled to obtain the paper-based material.

[0024] Furthermore, when preparing multi-layer structure paper, pulp with short fiber length is used as outer layer pulp material, and pulp with long fiber length is used as middle layer pulp material.

[0025] The present invention also provides a paper-based microfluid fuel cell prepared by the method.

[0026] Figure 1 It is a schematic diagram of the process of the technical solution of the present invention.

[0027] like Figure 2 As shown, the production process of PMFC based on papermaking in the present invention is mainly divided into two steps: papermaking and battery manufacturing. Among them, the papermaking process is mainly divided into the following four steps. First, make pulp, and the available technologies include chemical method, mechanical method, chemical mechanical method, semi-chemical method, waste paper pulping, etc.; secondly, filter out the moisture in the pulp to achieve the initial forming of paper, and the available technologies include flat screen filtration, press screen filtration, round screen filtration, screen filtration, filter cloth filtration, etc.; then completely remove the moisture in the formed wet paper, and the available drying technologies include natural drying, high temperature drying, freeze drying, etc.; finally, the dried paper is flattened, and the available technologies include cold pressing, hot pressing, ironing, etc.

[0028] To use the above paper as the battery substrate of PMFC, it is first necessary to divide the flow channel of appropriate size. The available technologies include mechanical cutting, laser cutting, photoresist etching, batik, flexographic printing, etc.; secondly, load the electrode into the corresponding area of ​​the flow channel. The available technologies include split electrode patch installation, electrode ink deposition, screen printing, roll-to-roll printing, 3D printing, etc.; then connect the electrode to the current collector. The available technologies include split current collector patch installation, current collector ink deposition, screen printing, roll-to-roll printing, 3D printing, etc.; finally, package the entire battery. The available technologies include hot pressing packaging, adhesive packaging, injection molding packaging, mechanical packaging, etc.

[0029] The present invention regulates the pore structure of the paper base by regulating the pulp properties (fiber size, fiber concentration, type of additives, etc.) and process parameters (fiber loading, drying conditions, leveling conditions, etc.) during the papermaking process, making it more conducive to the capillary flow of the electrolyte, the diffusion movement of the reactants, and the conduction of ions between the electrodes, thereby greatly improving the performance of paper-based microfluidic fuel cells, far exceeding existing batteries of the same type based on commercial filter paper.

[0030] Furthermore, the present invention obtains a composite paper substrate with a multi-level pore structure through papermaking technology, wherein the electrolyte flow area located in the middle layer selects large pores to promote its capillary flow, and the electrode deposition area located in the outermost layer selects small pores to prevent catalyst penetration waste and internal short circuit of the battery, thereby taking into account both catalyst utilization and capillary flow rate, and effectively avoiding internal short circuit of the battery.

[0031] Furthermore, the papermaking technology of the present invention can be used to wrap the anode inside the paper substrate, thereby isolating it from the external air and avoiding the generation of mixed potential and parasitic current at the anode.

[0032] The present invention discloses the following technical effects:

[0033] The present invention relates to a novel paper-based microfluidic fuel cell (PMFC) technology, which uses papermaking technology to improve the pore structure of a paper substrate, making it more conducive to the capillary flow of an electrolyte, the diffusion transport of reactants, and the conduction of ions between electrodes, thereby replacing the commercial filter paper widely used in existing PMFCs, thereby improving the problem of low PMFC performance caused by the slow liquid absorption speed and large ohmic resistance of the paper substrate, meeting the mass transfer and conductivity requirements of the PMFC, providing a structural basis for improving the performance of the PMFC, and increasing the power output of the PMFC.

[0034] The invention combines papermaking technology with PMFC, thereby effectively improving the power output of PMFC, and has broad application prospects and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a schematic diagram of the process of the technical solution of the present invention;

[0037] Figure 2 It is a preparation flow chart of the technical solution of the present invention;

[0038] Figure 3 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell according to Example 1 of the present invention;

[0039] Figure 4 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell according to Example 2 of the present invention;

[0040] Figure 5 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell according to Example 3 of the present invention;

[0041] Figure 6 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell according to Example 4 of the present invention;

[0042] Figure 7 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell according to Example 5 of the present invention;

[0043] Figure 8 This is a schematic diagram of the structure of a paper-based microfluidic fuel cell according to Example 6 of the present invention;

[0044] Among them, 1-paper substrate, 2-current collector, 3-cathode, 4-anode, 5-conductive silver grid;

[0045] Fig. 9 The performance comparison of PMFC using homemade paper and commercial filter paper in Example 2 of the present invention is shown; wherein, a is a comparison curve of current density and power density of paper-based microfluid fuel cells based on self-made paper and commercial filter paper (slow filter paper and fast filter paper) in Example 2; b is a comparison curve of single electrode performance of paper-based microfluid fuel based on self-made paper and commercial filter paper (slow filter paper and fast filter paper) in Example 2; c is a comparison curve of activation time of paper-based microfluid fuel cells based on self-made paper and commercial filter paper (slow filter paper and fast filter paper) in Example 2; d is a comparison curve of impedance of paper-based microfluid fuel cells based on self-made paper and commercial filter paper (slow filter paper and fast filter paper) in Example 2;

[0046] Fig.10 The performance of the battery prepared with different stirring times in Example 2;

[0047] Fig.11 The performance of the battery prepared with different cellulose surface densities in Example 2;

[0048] Fig.12 The performance of the battery prepared using different hot pressing pressures in Example 2. DETAILED DESCRIPTION

[0049] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0050] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0051] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0052] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0053] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0054] Currently, PMFC has two structures: split and integrated. The former uses independent electrode and current collector modules, so external packaging is required to provide assembly pressure to press them on the paper base surface. The latter deposits the electrodes and current collectors completely on the surface or inside of the paper base, so no external packaging is required to provide assembly pressure.

[0055] Example 1

[0056] Figure 3 Schematic diagram of the PMFC single cell structure of Example 1 of the present invention. The cell adopts a split structure and a typical Y-shaped flow channel, and two streams of electrolyte are sucked in from the two tentacles of the Y respectively.

[0057] (1) Paper base manufacturing: A certain amount of cellulose fibers was mixed with an appropriate amount of water by a mechanical method, and then the mixture was broken up and cut into a uniformly dispersed fiber solution (3.33 mg / mL) by a blender for 6 min. The fiber solution was then poured into a filter device with a fixed filter area by a press filter method, and most of the water was filtered out by a press plate to obtain a wet paper base. The wet paper base was then placed in a 60°C oven and dried thoroughly by a high-temperature drying method to obtain a dry paper base. Finally, the dry paper base was placed in a hot press and hot-pressed at 90°C and 1 MPa for 5 min to obtain a finished paper base.

[0058] (2) Battery manufacturing:

[0059] First, the finished paper base obtained by papermaking is cut into a Y-shaped paper base 1 by mechanical cutting; then the current collector 2, cathode 3 and anode 4 are installed on the same side surface of the paper base 1 by external pressure using a patch installation method; finally, all battery components are fixed between two end plates by a mechanical packaging method.

[0060] The main feature of the battery is that the cathode 3 and the anode 4 of the battery are located on the same side surface of the paper substrate, and a certain electrode distance is maintained between the two.

[0061] During actual operation, the two tentacles at the bottom of the battery are immersed in different electrolytes. After the corresponding electrolytes soak the electrode area, the battery can be activated and supply power to the outside. The electrode conductivity of this battery is good and the power density is high; the structure is relatively complex and requires external packaging to provide assembly pressure, so most of them are not flexible. This battery structure is more suitable for some high power density application scenarios.

[0062] Embodiments 2-4 provide a PMFC with an integrated structure, and there are three options for electrode placement: two electrodes are located on the same surface of the paper substrate (embodiment 2), two electrodes are located on different surfaces of the paper substrate (embodiment 3), and some or all of the electrodes are located inside the paper substrate (embodiment 4).

[0063] Example 2

[0064] Figure 4 Schematic diagram of the PMFC single cell structure of Example 2 of the present invention. The cell adopts a typical Y-shaped flow channel, and two streams of electrolyte are sucked in from the two tentacles of the Y respectively.

[0065] (1) Paper base preparation: same as in Example 1;

[0066] (2) Battery manufacturing:

[0067] First, the finished paper base obtained by papermaking is cut into a Y-shaped paper base 1 by mechanical cutting; then the current collector 2 is loaded onto the surface of the paper base 1 by a patch installation method; then the cathode 3, the anode 4 and the conductive silver grid 5 are directly deposited onto the same side surface of the paper base 1 by a deposition method; finally, all battery components are fixed inside the plastic film by a hot pressing packaging method.

[0068] The main feature of the battery is that the cathode 3 and the anode 4 of the battery are located on the same side surface of the paper substrate, and a certain electrode distance is maintained between the two.

[0069] In actual operation, the two tentacles at the bottom of the battery are immersed in different electrolytes respectively. After the corresponding electrolytes infiltrate the electrode area, the battery can be activated and supply power to the outside. This type of battery can effectively avoid internal short circuits caused by electrode ink penetration, does not require external packaging to provide assembly pressure, and is highly compact and flexible; but due to the large electrode spacing (especially for batteries with larger electrodes), the ion transmission resistance between the electrodes is large, resulting in a large internal resistance of the battery and a low power density. This electrode solution is more suitable for PMFCs with small electrodes.

[0070] Example 3

[0071] Figure 5 Schematic diagram of the PMFC single cell structure of Example 3 of the present invention. The cell adopts an integrated structure and a typical strip-type flow channel, with only one stream of electrolyte being sucked in from the bottom.

[0072] (1) Paper base preparation: same as in Example 1;

[0073] (2) Battery manufacturing:

[0074] First, the finished paper base obtained by papermaking is cut into strip-shaped paper base 1 by laser cutting; then the current collector 2 is loaded on the surface of the paper base 1 by patch installation; then the cathode 3, anode 4 and conductive silver grid 5 are directly deposited on the two side surfaces of the paper base 1 by deposition; finally, all battery components are fixed inside the plastic film by hot pressing packaging. The main feature of the battery is that the cathode 3 and anode 4 of the battery are located on different side surfaces of the paper base 1 and face to face.

[0075] In actual operation, the bottom of the battery is immersed in the electrolyte. After the corresponding electrolyte infiltrates the electrode area, the battery can be activated and supply power to the outside. This solution simplifies the electrolyte configuration and can effectively reduce the internal resistance of the battery; however, the cathode ink and the anode ink may penetrate into the paper substrate and contact each other, causing an internal short circuit in the battery. This electrode solution is more suitable for some PMFCs with large electrodes.

[0076] Example 4

[0077] Figure 6Schematic diagram of the PMFC single cell structure of Example 4 of the present invention. The cell adopts an integrated structure and a typical strip-type flow channel, with only one stream of electrolyte being sucked in from the bottom.

[0078] (1) Paper base preparation: same as in Example 1;

[0079] (2) Battery manufacturing:

[0080] First, the finished paper base obtained by papermaking is cut into strip-shaped paper base 1 by laser cutting; then the current collector 2 is loaded on the surface of the paper base 1 by patch installation method; then the cathode 3, anode 4 and conductive silver grid 5 are directly deposited on the two side surfaces of the paper base 1 by deposition method; thereafter, a layer of paper base 1 is added on one side of the anode 4 by papermaking again, and combined with the paper base 1, so that the anode 4 is embedded in the paper base; finally, the hot pressing packaging method is used to fix all battery components inside the plastic film. Its main features are: the cathode 3 and anode 4 of the battery are located on different side surfaces of the paper base 1, and face to face, and the anode 4 is embedded in the two layers of paper base 1.

[0081] In actual operation, the bottom of the battery is immersed in the electrolyte. After the corresponding electrolyte infiltrates the electrode area, the battery can be activated and supply power to the outside. This electrode solution simplifies the electrolyte configuration and can effectively reduce the internal resistance of the battery. In addition, the paper substrate that absorbs the electrolyte can isolate the anode from the air and provide a more sufficient fuel supply to the anode; however, its battery processing process is more complicated, and the cathode ink and anode ink may penetrate into the paper substrate and contact each other, causing an internal short circuit in the battery. This solution is more suitable for some PMFCs whose anodes cannot contact the air.

[0082] For the integrated PMFC in Example 2-4, the large pore paper base easily causes the electrode ink to penetrate into the paper base during electrode deposition, resulting in catalyst waste and even internal short circuit of the battery; the small pore paper base easily causes the electrolyte capillary flow rate to be too low, resulting in untimely supply of reactants. By adjusting the parameter of the pulp stirring time in papermaking, the pore size of the finished paper base can also be controlled, thereby constructing a special paper base with a composite pore structure, using small pores on the surface of the paper base for depositing electrodes and large pores inside the paper base for absorbing electrolyte.

[0083] Example 5

[0084] Figure 7 This is a schematic diagram of the PMFC single cell structure of Example 5 of the present invention. The cell adopts an integrated structure and a two-stage composite paper base (small pores-large pores). The two electrodes are located on the same surface of the paper base (small pore side), and a typical Y-shaped flow channel is adopted. The two electrolytes are sucked in from the two tentacles of the Y respectively.

[0085] (1) Manufacturing of two-stage composite paper base:

[0086] First, a mechanical method is used to mix a certain amount of cellulose fibers with an appropriate amount of water, and then a blender is used to break up and cut them into evenly dispersed fiber solutions, one of which has a short stirring time (1 min) and the other has a long stirring time (6 min); then a press-mesh filtration method is used, the fiber solution with a long stirring time is first poured into a filter device with a fixed filtration area, and then the fiber solution with a short stirring time is poured on the surface of the former, and then most of the water is filtered out with a pressing plate to obtain a wet paper base; then a high-temperature drying method is used to put the wet paper base into an oven and thoroughly dry it at 60°C; finally, a hot pressing method is used to put the dry paper base into a hot press and hot press it at 90°C at a pressure of 1 MPa for 5 minutes to obtain a finished paper base, which has a two-level composite pore structure (small pores-large pores).

[0087] (2) Battery manufacturing:

[0088] First, the paper base with a two-level composite pore structure (small pores-large pores) obtained by papermaking is cut into a Y-shaped paper base 1 by mechanical cutting; then the current collector 2 is loaded on the surface of the paper base 1 by patch installation; then the cathode 3, anode 4 and conductive silver grid 5 are directly deposited on the surface of the small pore side of the paper base 1 by deposition; finally, all battery components are fixed inside the plastic film by hot pressing packaging. The main feature of the battery is that the cathode 3 and anode 4 of the battery are located on the same surface of the smaller pores of the paper base, and a certain electrode distance is maintained between the two.

[0089] In actual operation, the two tentacles at the bottom of the battery are immersed in different electrolytes. After the corresponding electrolytes soak the electrode area, the battery can be activated and supply power to the outside. This composite pore structure of the paper base can effectively prevent the electrode ink from penetrating into the paper base, thereby avoiding the waste of catalyst.

[0090] Example 6

[0091] Figure 8 This is a schematic diagram of the PMFC single cell structure of Example 6 of the present invention. The cell adopts an integrated structure and a three-level composite paper base (small pores-large pores-small pores). The two electrodes are located on different side surfaces of the paper base and adopt a typical strip-type flow channel. Only one electrolyte is sucked in from its bottom.

[0092] (1) Three-level composite paper base manufacturing:

[0093] First, a mechanical method is used to mix a certain mass of cellulose fibers with an appropriate amount of water, and then a blender is used to break up and cut them into evenly dispersed fiber solutions, one of which has a short stirring time (1 min) and the other has a long stirring time (6 min); then a press-mesh filtration method is used to pour the fiber solution with a long stirring time into a filter device with a fixed filtration area, and then the fiber solution with a short stirring time is poured on the surface of the former, and then the fiber solution with a long stirring time is poured on the surface of the first two, and finally most of the water is filtered out with a pressing plate to obtain a wet paper base; then a high-temperature drying method is used to put the wet paper base into an oven and thoroughly dry it at 60°C; finally, a hot pressing method is used to put the dry paper base into a hot press and hot press it at 90°C at a pressure of 1 MPa for 5 minutes to obtain a finished paper base, which has a three-level composite pore structure (small pores-large pores-small pores).

[0094] (2) Battery manufacturing:

[0095] First, the paper base with a three-level composite pore structure (small pores-large pores-small pores) obtained by papermaking is cut into strip-shaped paper base 1 by laser cutting; then the current collector 2 is loaded on the surface of the paper base 1 by patch installation; then the cathode 3, anode 4 and conductive silver grid 5 are deposited on the surfaces on both sides of the small pores of the paper base 1 by deposition; finally, all battery components are fixed inside the plastic film by hot pressing packaging. The main feature of the battery is that the cathode 3 and anode 4 of the battery are located on the surfaces on both sides of the small pores of the paper base 1, and face to face.

[0096] In actual operation, the bottom of the battery is immersed in the electrolyte. After the corresponding electrolyte infiltrates the electrode area, the battery can be activated and supply power to the outside. This composite pore structure of the paper base can effectively prevent the electrode ink from penetrating into the paper base, thereby avoiding catalyst waste and internal short circuit of the battery.

[0097] Battery performance measurement:

[0098] The present invention combines papermaking technology with PMFC, and adjusts the pore structure of paper by controlling various parameters in the papermaking process, thereby optimizing the power generation performance of the battery.

[0099] The paper substrate is a single pore structure with an integrated battery structure, where the cathode and anode electrodes are distributed on the same side of the paper substrate. The electrode area of ​​the cathode and anode is 10 mm × 2 mm, and the electrode spacing is 4 mm. The cathode catalyst is MnO 2 (6mg / cm 2 ), the anode catalyst is Pt-Ru / C (0.1 mg / cm 2); the cathode electrolyte is 3M KOH, and the anolyte is 3M KOH+2M ethanol; the paper substrates used include two commercial filter papers (slow type and fast type) and a variety of self-made papers with different pore structures. During the papermaking process, the pore structure is mainly regulated by controlling the pulp stirring time, cellulose surface density and paper hot pressing pressure.

[0100] When the pulp stirring time is 3 minutes and the cellulose surface density is 0.02g / cm 2 , the performance of PMFC based on the self-made paper and commercial filter paper is compared under the same manufacturing conditions of 1 MPa. Fig. 9 , where the battery assembly method is Figure 4 shown.

[0101] The experimental results show that the performance of PMFC using self-made paper is significantly better than that of PMFC using commercial filter paper. Fig. 9 a It can be seen that the performance of the fast filter paper is slightly better than that of the slow filter paper, with the peak power density (PPD) and maximum current density (MCD) increasing from 1.2 mW / cm 2 and 4.6mA / cm 2 Increased to 1.8mW / cm 2 and 6.5mA / cm 2 This is mainly due to the more efficient fuel supply to the anode due to its faster capillary flow. However, this positive effect is very limited, and significant mass transfer losses are encountered in both cases. For the self-made paper, the PPD and MCD further increase to 5.4 mW / cm 2 and 42.3mA / cm 2 , which are 4.5 and 9.2 times of those of low-speed filter paper, respectively, indicating that mass transfer loss has been greatly improved. Fig. 9 b It can be seen that the anode performance of PMFC based on commercial filter paper is significantly lower than that of PMFC based on self-made paper, indicating that self-made paper is superior to commercial filter paper in fuel supply. Fig. 9 c shows the activation time of different PMFCs, measured from the moment the bottom of the cell contacts the electrolyte until the open circuit voltage stabilizes. The activation times of PMFCs using slow filter paper, fast filter paper, and self-made paper are 2940 seconds, 1700 seconds, and 350 seconds, respectively, proving that the capillary flow rate in the self-made paper is faster. Fig. 9 d compared their ohmic resistance (the intercept of the impedance curve on the X-axis), which was 65.1Ω, 47.8Ω and 13Ω respectively, proving that the ion conduction resistance in the self-made paper is smaller. These results show that the paper with specific pore parameters obtained by papermaking is more suitable as a substrate for PMFC than the existing commercial filter paper.

[0102] Further, in Example 2 ( Figure 4In order to show the effect of different pulp stirring time on battery performance in papermaking process, the hot pressing pressure was 1MPa and the cellulose surface density was 0.04g / cm 2 Under these conditions, five stirring times were selected: 1min, 3min, 6min, 9min and 15min. Fig.10 The battery performance under different stirring times. The experimental results show that when the stirring time is about 6 minutes, the battery performance is the best, and the MCD is 48.9mA / cm 2 , PPD is 6.3mW / cm 2 , while further extension of the stirring time leads to a decrease in battery performance. This is because the long stirring time cuts the paper fibers shorter, resulting in a smaller porosity and thinner paper thickness. The former will weaken the paper's liquid absorption speed, resulting in slower fuel supply and reduced anode performance, but it can also prevent excessive penetration of the catalyst ink, concentrate the catalytic active sites near the current collector, and improve the utilization of the catalyst; while the latter will affect the battery's ion transport. The thicker the paper, the more ion transport paths it can provide (for electrodes on the same surface), thereby reducing the battery's ohmic impedance and improving battery performance. Therefore, under the combined effect of the two, the battery performance is optimal when the stirring time is 6 minutes.

[0103] Further, in Example 2 ( Figure 4 Based on the structure shown in the figure, in order to show the effect of different cellulose surface densities on battery performance in the papermaking process, four cellulose surface densities were selected under the conditions of stirring time of 3 min and hot pressing pressure of 1 MPa: 0.01 g / cm 2 , 0.02g / cm 2 , 0.04g / cm 2 and 0.08g / cm 2 . Fig.11 The battery performance under different cellulose surface densities. The experimental results show that the cellulose surface density is 0.04g / cm 2 The battery performance reaches the best when MCD is 47.1mA / cm 2 , PPD is 6mW / cm 2; Continuing to increase the cellulose surface density does not have a better effect on the battery. This is because as the surface density increases, the porosity of the paper will decrease slightly, reducing the rate of fuel supply, which will weaken the anode performance of the battery. On the other hand, the thickness of the paper will also increase almost proportionally with the increase in surface density, providing more ion transfer paths and reducing the ohmic impedance of the battery; in addition, when the thickness increases, the lateral diffusion of fuel at a farther position perpendicular to the anode direction to the anode surface will also increase, which can to some extent compensate for the slow fuel supply caused by the weakened liquid absorption rate. Therefore, under the combined influence of these two factors, the cellulose surface density is 0.04g / cm 2 The battery performance is optimal.

[0104] Furthermore, based on Example 2, in order to demonstrate the effect of different hot pressing pressures in the papermaking process on battery performance, the stirring time was 3 min and the cellulose surface density was 0.02 g / cm 2 Under these conditions, three hot pressing pressures were selected: 1MPa, 2MPa, and 2.5MPa. Fig.12 The battery performance under different thermal pressure conditions. The experimental results show that the battery performance is optimal under 1MPa thermal pressure, and the MCD is 42.3mA / cm 2 , PPD is 5.4mW / cm 2 Continuing to increase the hot pressing pressure will weaken the battery performance. This is because high pressure will press the paper fibers more tightly, weakening the paper's liquid absorption speed and leading to worse fuel supply. Therefore, the battery performance is optimal when the hot pressing pressure is 1MPa.

[0105] The present invention combines papermaking technology with paper-based microfluidic fuel cells. The optimized paper-based pore structure is more conducive to the capillary flow of electrolyte, the diffusion transmission of reactants and the conduction of ions between electrodes, thereby greatly improving the power output of the battery.

[0106] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a paper-based microfluidic fuel cell based on papermaking technology, characterized in that: The following steps are involved: (1) Preparation of paper-based materials: a. preparing pulp; b. filtering out water from the pulp to achieve preliminary forming of paper; c. drying the paper; d. flattening the paper to obtain the paper base material; (2) Preparation of paper-based microfluidic fuel cells: The paper-based material prepared in step (1) is processed into a predetermined shape, and the battery assembly is fixed on the surface of the paper-based material to prepare a paper-based microfluidic fuel cell.

2. The method according to claim 1, characterized in that The pore structure of the paper-based material is regulated by adjusting the stirring time during the pulp preparation process.

3. The method according to claim 1, characterized in that The pore structure of the paper-based material is regulated by adjusting the fiber surface density.

4. The method according to claim 1, characterized in that: The pore structure of the paper-based material is regulated by adjusting the pressure of the flattening process.

5. The method according to claim 1, characterized in that The methods for preparing pulp include chemical method, mechanical method, chemical-mechanical method, semi-chemical method or waste paper pulping; the methods for filtering out moisture include flat mesh filtration, pressed mesh filtration, round mesh filtration, screen filtration or filter cloth filtration; the methods for drying paper include natural drying, high-temperature drying or freeze drying; the methods for smoothing paper include cold pressing, hot pressing or ironing.

6. The method according to claim 1, characterized in that The paper-based material is a multi-layer composite material.

7. The method according to claim 6, characterized in that The method for preparing the multilayer composite material comprises the following steps: a. Prepare pulp to obtain pulp with different fiber lengths: b. Pulps with different fiber lengths are added to the filter device respectively, the water in the paper is filtered out to obtain wet paper, and then the different wet papers are stacked to form a multi-layer structure. After that, they are pressed with a pressing plate in the filter device to discharge the remaining water and ensure the close fit between different layers, so as to achieve the preliminary formation of the multi-layer structure of the paper; c. Paper drying; d. The paper is leveled to obtain the paper-based material.

8. The method according to claim 7, characterized in that When preparing multi-layer structure paper, pulp with short fiber length is used as outer layer pulp material, and pulp with long fiber length is used as middle layer pulp material.

9. A paper-based microfluidic fuel cell prepared by the method according to any one of claims 1 to 8.

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