Decentralized sorption-based atmospheric water-hydrogen device

Abstract

A unified, modular system designed for decentralized, off-grid hydrogen production is provided. The system can include a device that integrates photovoltaic (PV) generation, atmospheric water harvesting (AWH) using a hydrogel sorbent, and a proton exchange membrane (PEM) electrolyzer into a single architecture for simultaneously harvesting water and producing hydrogen. The device can rely on a hydrogel stage that passively captures atmospheric moisture during nighttime hours and, once solar irradiance becomes available during the day, the hydrogel can be thermally regenerated using solar heat, releasing liquid water that is subsequently fed to a PEM electrolyzer. Simultaneously, a PV panel can generate electrical power to split this water into hydrogen and oxygen, thus co-locating energy and water generation in a single compact footprint.

Description

Attorney Docket No.: MIT 26048 PCT | 88212-427690DECENTRALIZED SORPTION-BASED ATMOSPHERIC WATERHYDROGEN DEVICEGOVERNMENT RIGHTS

[0001] This invention was made with government support under HR0011-21-2-0001 awarded by the Defense Advanced Research Projects Agency, and DE-EE0009679 awarded by the U.S. Department of Energy. The government has certain rights in the invention.CROSS REFERENCE TO RELATED APPLICATION

[0002] The present disclosure claims priority to and the benefit of U.S. Provisional Application No. 63 / 713,578, entitled “Decentralized Sorption-Based Atmospheric Water- Hydrogen Device,” filed on October 29, 2024, the content of which is incorporated by reference herein in its entirety.FIELD

[0003] The present disclosure relates to a decentralized green hydrogen production device, and more particularly relates to a sorbent-based atmospheric water harvesting material (desiccant) strategically deployed either as a coating on a photovoltaic (PV) cell or within a separate dedicated unit for the purpose of hydrogen production.BACKGROUND

[0004] The escalating challenges posed by climate change and water scarcity necessitate innovative solutions in the energy sector. In fact, it is estimated that population and economic growth will lead to an additional 1.8 billion people living in moderate to severe water scarcity regions by 2050, with 80% of those residing in developing countries. Limited access to potable w ater leads not only to community health decline and transmission of waterborne diseases, but also profoundly impacts the economic uncertainty of a region, further reducing the quality of life for local inhabitants. As a result, global industries have invested millions of dollars in research to attempt to alleviate the burden and find solutions to the world’s impending water shortages.

[0005] One option that has been explored as a possible solution to water scarcity is the adoption of hydrogen as a clean, versatile alternative to traditional energy sources.Attorney Docket No.: MIT 26048 PCT | 88212-427690Hydrogen, particularly when produced through the process of electrolysis using renewable energy sources like solar power, stands at the forefront of the transition towards a more sustainable and low-carbon future. This process, known as green hydrogen production, is gaining traction as a viable method for clean energy generation.

[0006] The path to fully harnessing green hydrogen's potential is fraught with obstacles, including the significant demand for water and the limitations in production efficiency due to the reliance on natural sunlight alone. First, the production of green hydrogen, especially in arid or water-scarce regions, faces the critical challenge of water availability. Further, current solar-powered green hydrogen systems often struggle to surpass energy conversion efficiencies of 10%, hindered by suboptimal energy capture, conversion processes, and losses during electrolysis. Overcoming these efficiency and sustainability barriers is important for the scalability and broader application of green hydrogen as a reliable energy' carrier.

[0007] Accordingly, there is a need for green hydrogen production methods that are not only efficient but also sustainable in their water use.SUMMARY

[0008] The present application is directed to a system that is capable of simultaneously harvesting water and producing hydrogen. For example, the system can be designed to efficiently produce both hydrogen and potable water by leveraging atmospheric humidity' as a water source, thus reducing reliance on external water supplies. The system can include a decentralized green hydrogen production device that integrates sorption-based atmospheric water harvesting (SAWH) with solar energy conversion. The device can include one or more photovoltaic (PV) cells that capture solar energy'. The device can include a sorption-based atmospheric water harv esting material, e.g., a lithium chloride-loaded polyacrylamide (PAM- LiCl) hydrogel sorbent, that can be deployed as a coating on the PV cells and / or within a separate dedicated unit. This sorbent material can absorb water vapor from the ambient air passively and / or actively. The PV cells can simultaneously generate electricity' and desorb water from the sorbent material. In some embodiments, the desorbed w ater can be directed via a gravity -fed condensation on a naturally or force-convected heat sink. The vapor from the hydrogel can then be condensed on a surface and can be fed, dripped, and / or directed to an anode surface of the proton exchange membrane (PEM) cell, where it can undergo electrolysis to split into hydrogen and oxygen. In some embodiments, a storage unit can beAttorney Docket No.: MIT 26048 PCT | 88212-427690 used to store the hydrogen for later use. In some embodiments, the hydrogen can be used as a reduction agent to produce clean fuel, such as, for example, ammonia and / or methanol.

[0009] Optimization of system performance can occur via heat and mass transfer analyses, including PV to PEM scaling and sorbent to hydrogen production comparisons. The system can also passively replenish the surface of the PEM(s) while maintaining adequate pressure between the anode and cathode. It will be appreciated that the decentralized nature of this device can make it ideal for remote applications, offering a reliable source of both energy and clean water for point of use applications.

[0010] One embodiment of a hydrogen production system includes a sorbent-based atmospheric water harvesting material, one or more photovoltaic (PV) cells, a condenser, a heat sink, and a hydrogen production cell. The condenser is configured to capture water vapor from the sorbent-based atmospheric water harvesting material. The hydrogen production cell has a photovoltaic (PV) electrolyzer circuit. The electrolyzer circuit includes a proton exchange membrane (PEM) that is configured to perform electrolysis on desorbed water received from the sorbent-based atmospheric water harvesting material to split the desorbed water into hydrogen and oxygen.

[0011] One or more of the following features can be included. The hydrogen production system can be configured to simultaneously harvest water and produce hydrogen. The system can further include a storage unit configured to store the hydrogen. The water can be condensed by gravity’. The sorbent-based atmospheric water harvesting material can be a PAM-LiCl hydrogel. The PAM-LiCl hydrogel can be deployed as a coating on the one or more PV cells or within a separate dedicated unit. The one or more PV cells can be configured to capture solar energy' to generate electricity’ while simultaneously desorbing water from the sorbent material. The sorbent-based atmospheric water harvesting material can be disposed between the one or more PV cells and the condenser. The sorbent-based atmospheric water harvesting material can be disposed between the one or more PV cells and the PEM. The sorbent-based atmospheric water harvesting material can be disposed between the PEM and the heat sink. The hydrogen production system can have a water production capacity of about lL / m2 / day and a hydrogen production capacity of about 5 ml / min. The system can be configured to operate passively.Attorney Docket No.: MIT 26048 PCT | 88212-427690

[0012] In another aspect, embodiments relate to a method of hydrogen production include absorbing moisture from a condenser surface using a hydrogel and exposing one or more photovoltaic (PV) cells that are associated with the hydrogel to incident solar irradiation to convert the solar irradiation to electricity. Using the electricity, the method further includes powering a hydrogen production cell having a photovoltaic (PV) electrolyzer circuit comprising a proton exchange membrane (PEM) to form a hydrogen product. Additionally, the method includes heating the hydrogel using excess heat from the one or more PV cells to desorb a condensed water from the hydrogel, and collecting the hydrogen product.

[0013] One or more of the following features can be included. The hydrogen product and the condensed water can be formed simultaneously. Hydrogen production can occur on a daily cycle, in which absorption occurs when the hydrogel is exposed to nighttime ambient air, and desorption occurs during daytime. The method can further include feeding the condensed water to a cathode side of the PEM to facilitate water splitting via electrolysis. The condensed water can be fed to the cathode side by gravity. The method can include adjusting one or more of ambient temperature, ambient air flow, voltage, or current to one of increase or decrease an amount of hydrogen product produced. Increasing the amount of hydrogen product produced can decrease an amount of condensed water formed. The method can further include adjusting a composition of the hydrogel based on one or more of ambient temperature, ambient air flow, voltage, current, assumptions on solar input, or breeze data. Adjusting the composition of the hydrogel can further include altering one or more of a thickness or consistency of the hydrogel. The method can further include optimizing hydrogen production by performing one or more of heat and mass transfer analyses, PV to proton exchange membrane (PEM) scaling, or hydrogel to hydrogen production comparisons. The method can further include maintaining adequate pressure between an anode and a cathode of the hydrogen production cell during optimization. The method can further include optimizing a size ratio of the one or more PV cells to a size of the hydrogel to ensure that the desorbed water forms condensed water in the PV electrolyzer circuit.BRIEF DESCRIPTION OF THE DRAWINGS

[0014] This disclosure will be more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, in which:Attorney Docket No.: MIT 26048 PCT | 88212-427690

[0015] FIG. 1 A is a perspective view of one embodiment of a system of the present embodiments exposed to an ambient environment;

[0016] FIG. IB is a perspective view of another embodiment of a system of the present embodiments exposed to the ambient environment;

[0017] FIG. 2A is a schematic illustration of operation of a device of the system of FIG. 1A during nighttime;

[0018] FIG. 2B is a schematic illustration of operation of the device of the system of FIG. 1A during daytime;

[0019] FIG. 3 is a graph illustrating a spectral distribution of solar energy that shows the dual use of high-energy photons for photovoltaic electricity generation and low-energy photons for photothermal water release;

[0020] FIG. 4A is another schematic illustration of operation of the device of the system of FIG. 1A during both daytime and nighttime;

[0021] FIG. 4B is a graph illustrating water production during an absorption phase of the device of FIG. 1A and hydrogen production during the desorption phase of the device of FIG. 1A;

[0022] FIG. 5 is a schematic side view of the components of FIG. 4A;

[0023] FIG. 6A is a schematic illustration of heat and mass transport of the system of FIG.1 A showing relative dimensions of the device; and

[0024] FIG. 6B is a perspective view of a time lapse of hydrogen collection following operation of the system of FIG. 1A.DETAILED DESCRIPTION

[0025] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the systems compositions, designs, and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the systems, compositions, and methods specifically described herein andAttorney Docket No.: MIT 26048 PCT | 88212-427690 illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present disclosure is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present disclosure. Like-numbered components across embodiments generally have similar features unless otherwise stated or a person skilled in the art would appreciate differences based on the present disclosure and / or his / her knowledge.Accordingly, aspects and features of every embodiment may not be described with respect to each embodiment, but those aspects and features are applicable to the various embodiments unless statements or understandings are to the contrary'.

[0026] Further, to the extent features, layers, sides, objects, steps, or the like are described as being “first,’’ “second,” third,” etc., and / or “lower,” “upper,” “middle,” etc., such numerical and / or location ordering / identification is generally arbitrary', and thus such numbering can be interchangeable unless indicated or otherwise understood by those skilled in the art to not be interchangeable. To the extent that the instant disclosure includes various terms for components and / or processes of the disclosed systems, compositions, designs, and methods, and the like, one skilled in the art, in view of the claims, present disclosure, and knowledge of the skilled person, will understand such terms are merely examples of such components and / or processes, and other components, designs, processes, and / or actions are possible.

[0027] The present disclosure generally provides for a system having a decentralized green hydrogen production device, e.g, a sorption-based atmospheric water-hydrogen (SAWH2) device, that integrates water absorption-desorption processes with solar energy conversion, offering a dual solution to the pressing needs for energy' and clean water. The SAWH2 device of the present embodiments can function as part of a fully integrated, solar-powered atmospheric water harvesting and hydrogen production system that operates using only’ ambient humidity and solar irradiance without requiring external water infrastructure, pressurization, or desalination. The device of the present embodiments can include: (i) a photovoltaic (PV) panel to supply power, (ii) a hygroscopic hydrogel to absorb and release atmospheric water vapor, and (iii) a proton exchange membrane (PEM) electrolyzer to convert the harvested water into hydrogen fuel.Attorney Docket No.: MIT 26048 PCT | 88212-427690

[0028] The device of the present embodiments has many benefits over conventional green hydrogen systems. For example, by leveraging a passive heat and mass transfer architecture, this compact and self-contained unit can provide both clean water and green hydrogen, and is capable of operating in off-grid, arid, or infrastructure-scarce regions. In fact, sorption-based atmospheric water harvesting (SAWH) can emerge as an energy -efficient solution for obtaining ultra-pure water off-grid, crucial for applications such as green hydrogen production. It will be appreciated that this technology- can harness ambient thermal energy for water absorption and desorption, minimizing the need for external power sources. Additionally, SAWH can be integrated into the thermal management of photovoltaic (PV) cells, enhancing their efficiency and longevity by mitigating heat stress. Moreover, by expanding the usable wavelength range of the solar spectrum. SAWH can contribute to a marked increase in the efficiency of hydrogen production, leveraging broader solar energy conversion pathyvays. As a result, the system of the present embodiments can be a scalable, decentralized hydrogen generator that is both water self-sufficient and energy efficient.

[0029] At least one novel feature of the present embodiments is the ability to utilize a sorbent-based system 100 to produce hydrogen and water as a byproduct. This approach not only enhances the efficiency and sustainability of hydrogen production, but also harnesses atmospheric humidity as a water source. The system 100 can include a device 101 that integrates yvater harvesting and hydrogen generation into a single, thermally coupled platform. As shown in FIG. 1 A, the device 101 can be exposed to the ambient enydronment yvhere it is capable of leveraging sunlight and air alone to poyver the co-production of yvater and hydrogen, e.g. producing hydrogen and / or performing passive and / or active water harvesting. In this way, the device 101 can combine two components of decentralized water and green hydrogen production — a sorbent based water harvesting system and a PV electrolyzer circuit — to provide a self-sustaining solution capable of operating in almost any climate, and notably, the most challenging climates. The device 101 can be fully- decentralized, with water harvesting from ambient air and production of green hydrogen using photovoltaic power, with low-grade thermal energy occurring concurrently. It will be appreciated that for the purposes of this disclosure, in some embodiment, the system 100 can include the device 101 and no additional components, which allows for the device 101 and the system 100 to be used interchangeably in some iterations of the system.Attorney Docket No.: MIT 26048 PCT | 88212-427690

[0030] Unlike traditional approaches that rely on hygroscopic photocatalysts or direct air electrolyzers, the device 101 can include a sorbent-based atmospheric water harvesting material, e.g., desiccant [metal-organic framework (MOF) / zeolite / silica / hygroscopic salt] or hydrogel impregnated with desiccant 102, for passive water capture and evaporative cooling, a photovoltaic (PV) panel, PV cell, or PV 104, and a proton exchange membrane (PEM) electrolyzer 106 that is powered by solar energy (shown in more detail in FIGS. 2A-2B). Coupling the PV panel 104 with a hydrogel 102 not only enhances PV efficiency through cooling, but can also supply clean water for electrolysis. The hydrogel 102 can be deployed either as a coating on the backside of the photovoltaic (PV) cell 104, adhered to a heat sink affixed to the rear of the PV cell 104, or within a separate dedicated unit that is solely focused on water harvesting to supply water to the surface of the PEM 106, a hydrogen production cell, and / or a hydrogen storage unit. In certain embodiments, such as whenever the rate of water produced or condensed on the PEM 106 exceeds the instantaneous rate of water at which hydrogen splitting occurs, an overflow conduit 117, as shown in FIG. IB, can be provided to divert the excess water into one or more storage tanks. The overflow conduit 117 can be designated as a pathway that diverts excess condensed water away from a region of the PEM 106 / condenser 107 when the instantaneous demand for electrolysis is exceeded. The overflow conduit 117 directs surplus liquid either into the storage unit 113 via a spigot 111 (shown in FIG. 4A) for later electrolyzer feed or into secondary- outlets for potable water, agriculture, sanitation, or cooling applications. For example, the stored water can subsequently be used to supply the PEM electrolyzer 106 during periods of low water yield, or alternatively directed for secondary- uses such as potable drinking w ater, agricultural irrigation, distilled water production, sanitation, or evaporative cooling applications.

[0031] In some embodiments, the hydrogel 102 can include a lithium chloride-loaded polyacrylamide (PAM-LiCl) hydrogel sorbent that can aim to increase hydrogen production efficiency while lowering the overall cost, though it will be appreciated that any hydrogel (desiccant) or sorbent combination that is sufficient for absorption and thermal desorption driven by the temperature of the proton exchange membrane (PEM) 106 and the ambient humidity can be used. The PAM-LiCl hydrogel 102 can be chosen as the sorbent material due, at least in part, to its favorable moisture uptake, even in low humidity- environments, high absorptive productivity (1.8 g / g), low desorption enthalpies, and / or proven mechanical stability when deployed as a cyclically loaded SAWH material. Moreover, the PAM-LiClAttorney Docket No.: MIT 26048 PCT | 88212-427690 hydrogel-salt composite 102 can exhibit rigorously quantified heat and mass transport properties in all types of environments.

[0032] Hygroscopic hydrogels can offer innovative solutions to critical global challenges such as water scarcity and climate change by harnessing ambient humidity to produce potable water and by leveraging sorption-desorption processes for sustainable cooling and heat storage. These materials may be particularly valuable for enhancing energy efficiency across various applications due, at least in part, to their strong moisture affinity in both ambient air and pure vapor environment. The device 101 can be designed to effectively cycle the sorbent 102 and demonstrate its record performance in both urban and rural environments.

[0033] One example of the composition of the hydrogel 102 of the present embodiments can be synthesized as follows, with the appreciation that this composition is merely exemplary:

[0034] Synthesis ofPAM-LiCl Hydrogels: The hydrogel 102 can be synthesized via radical polymerization of acrylamide monomers (AM, Sigma- Aldrich) in an aqueous solution of lithium chloride (LiCl, Sigma-Aldrich). The composite was fabricated to achieve approximately a 4 gram salt per gram polymer hydrogel at about 20% RH. First, approximately 18.3 g of LiCl was dissolved in approximately 50 milliliters of deionized water (DI H2O, Sigma- Aldrich) and stirred the solution until cool, e.g., for about four (4) hours. Then, approximately 4.6 grams AM was added and stirred for an additional approximately 15 minutes. Next, approximately 0.016 grams of ammonium persulfate (APS, Sigma-Aldrich), approximately 0.028 g N,N’ - methylenebisacrylamide (MBA, Sigma- Aldrich), and approximately 1.3 pL tetramethylethylenediamine (TEMED, Sigma- Aldrich) were added to the solution, stirred for approximately one (1) minute, and the solution was poured directly into the hydrogel stage of the device. The hydrogel-salt composite can be polymerized rapidly but was allowed approximately six (6) hours to set prior to use to ensure equilibrium. The table below summarizes the ingredients and their approximate quantities:Table 1: Ingredients and their approximate quantitiesIngredient Quantity [g]De-ionized water 50.000Lithium chloride (LiCl) 18.300Acrylamide (AM) 4.600Ammonium Persulfate (APS) 0.016Attorney Docket No.: MIT 26048 PCT | 88212-427690N,N'-methylenebisacrylamide (MBA) 0.028Tetramethylethylenediamine (TEMED) 0.013

[0035] The size ratio of the PV 104 to the hydrogel 102 can be optimized to ensure the captured moisture is desorbed and condensed into liquid water into the PEM electrolyzer 106, coupled with sufficient thermal insulation (not shown) to avoid thermal loss. Given a sufficient amount of harvested water into the electrolyzer, the main driving force of hydrogen production via the PEM 106 can be electrical generation through the PV panels 104.

[0036] In some embodiments, using the PAM-LiCl hydrogel sorbent 102 of the present embodiments, (approximately 1.79 gg1and 3.86 gg1at relative humidity (RH) of approximately 30% and approximately 70%, respectively), a device water production capacity of about lL / m2 / day and a hydrogen production capacity of about 5 ml / min can be obtained.

[0037] While a PAM-LiCl hydrogel sorbent is discussed herein, some additional nonlimiting examples can include polyacrylamide (PAM), polyvinyl alcohol (PVA), calcium chloride (CaCh). lithium bromide (LiBr), metal organic frameworks, and / or zeolites. For example, during water absorption, the desiccant or sorbent can absorb water vapor, or adsorb in the event that LiCl is used, from the surrounding air, from the surrounding air, either passively (e.g., natural diffusion) or actively (e.g., via forced convection, pressure swing, or vacuum swing). Solar energy can be used to produce electricity from the PV cell 104 while simultaneously desorbing water from the desiccant, which then can be employed for water splitting via electrolysis of water. Optimization of the performance of the system can be performed, and can include PV to PEM scaling, sorbent to hydrogen production comparisons, as well as novel insights into passively replenishing the PEMs surface while maintain adequate pressure between the anode and the cathode. Moreover, further optimization can be performed by investigating the impact of electrolytic pressure, surface wettability, and the exposed surface area of the cathode, utilizing a hydrophilic metal wick or polymer pillar array for enhanced water management, and optionally incorporating the overflow conduit 117 (as shown in FIG. IB) for diverting excess condensed water to a storage reservoir for later use in electrolysis or secondary applications. It will be appreciated that alternate arrangements of the system 100 are possible. For example, FIG. IB illustrates an alternative arrangement of a system 100' of the present embodiments, which utilizes a device 10T. AsAttorney Docket No.: MIT 26048 PCT | 88212-427690 shown, the device 101' can include a PV cell 104 in a similar arrangement as that of the device 101, having the overflow conduit 117, as discussed above in the discussion of FIG. IB, and a water collection tank or storage tank or storage unit 1 13 where produced hydrogen, or water in some embodiments, can be stored, as noted above. It will be appreciated that the overflow conduit 117 and the storage unit 113 can be used for either of the devices 101, 101' and are only being presented and discussed with respect to FIG. IB due to their presence in the figure. As shown, the storage unit 113 can be an inverted graduated cylinder, though various other forms of storing hydrogen can be used in conjunction with the device 101'. In some embodiments, the PEM 106 can be semi-decoupled for replacement, as in FIG. IB, though it is appreciated that in alternative embodiments, the PEM 106 can be affixed to a shell of the device 101'.

[0038] The device 101 can be optimized for maximum production and efficiency, for example by selecting parameters which maximize water productivity and thermal efficiency in a variety of environments, including a semi-arid environment. That is. the device 101 can be optimized for various material properties. For example, one or more such factors as ambient temperature, ambient air flow, voltage, current, assumptions on solar input, and / or breeze data, among other factors, can be measured and adjusted during optimization. In some embodiments, a material of the condenser 107 and / or a material to which the PV cell 104 is mounted can be changed to one or more of aluminum, copper, or the like to account for increased needs of heat retention of the system, for example. Moreover, the material of the PV 104 can be selected based, at least in part, on its performance, thickness, footprint, and / or coupling to the PEM 106.

[0039] Additionally, or alternatively, a composition of the hydrogel 102 can be adjusted, e.g., increased or decreased thickness, altered consistency, and so forth, to account for the needs of the system. Optimization can yield results, in some embodiments, as high as about 1.5 L of hydrogen at a generation rate of about 133 L / m2pv / day and about 240 L / m2PEM / day at an efficiency of about >13%. Additional details regarding optimization and orientation of various components, and various teachings pertaining to the device, can be found in International Application No. PCT / US / 2025 / 044292, filed under the Patent Cooperation Treaty entitled “Solar-Driven Hygroscopic Hydrogel Device for Atmospheric Water Harvesting,” filed on August 29. 2025, the content of which is incorporated by reference in its entirety.Attorney Docket No.: MIT 26048 PCT | 88212-427690

[0040] A thickness of the hydrogel 102 can vary. In some embodiments, a thickness of the hydrogel 102 can be about 4 millimeters, which can be a good trade-off between moisture uptake, desorption efficiency, and material cost. Thicker gels can exhibit higher thermal inertia and slower desorption rates, while thinner gels reduced total water capacity. At about 4 millimeters, the hydrogel 102 can reach near-equilibrium moisture content within approximately 8 hours, aligning well with typical nighttime absorption windows in diurnal operation. The coupling of passive AWH and direct-feed electrolysis, enabled by validated hydrogel modeling and thermal integration, can position the device 101 as a modular, scalable solution for decentralized water and hydrogen co-production.

[0041] The device 101 can operate in two distinct phases: nighttime absorption of atmospheric moisture into the hydrogel 102, followed by daytime desorption and electrolysis driven by solar input, as discussed further below. Uniquely, the device 101 can leverage the full solar spectrum, with high-energy photons driving photovoltaic conversion to power hydrogen production, while low-energy photons are captured as photothermal heat to regenerate the sorbent and release water on site. This dual-mode utilization can ensure efficient energy conversion and maximized productivity from a single solar input. Moreover, by employing a modular configuration, the hydration and electrolysis subsystems of the device 101 can be decoupled, allowing independent optimization and eliminating the use of external liquid water supplies, brine disposal, or embedded electrolytes that are common in conventional devices. Further still, unlike seawater-based hydrogen systems, the SAWFL device 101 of the present embodiments does not rely on coastal access, and can avoid the complexity of inert environments or membrane degradation under ultra-dry conditions. Instead, the device 101 can offer a robust, scalable, and low-maintenance solution for producing clean fuel and water in situ, using only sunlight and air, resources that are universally available, which can help bridge the gap between water security and green hydrogen access in off-grid and climate-vulnerable regions.

[0042] For the purposes of the present disclosure, the device 101 can simultaneously harvest water and produces hydrogen using photovoltaic energy'. It will be appreciated that while the present disclosure discusses hydrogen production and / or water harvesting as occurring simultaneously, the device 101 can operate with each of these processes occurring sequentially for at least a portion of the device operation. Specifically, while “simultaneously,” as used in the present disclosure, can refer to a portion of the two processesAttorney Docket No.: MIT 26048 PCT | 88212-427690 overlapping at a single point of time, or over multiple points in time, a person skilled in the art will recognize that there may occur a time in which hydrogen is produced while water is not yet still harvested due to the use of the produced hydrogen in the eventual harvesting of water, as discussed above and in greater detail below, which can still be referred to as simultaneous. That is, a slight delay may occur between the hydrogen production and the water harvesting due to a portion of the hydrogen being used for water harvesting, this would still be considered simultaneous for the purposes of the present disclosure.

[0043] Another novelty of the present embodiments can be the ability to use a single device interface to leverage a single power source, e.g., solar thermal energy, for simultaneous hydrogel electrolysis and hydrogen desorption for water production. For example. FIGS. 2A- 2B schematically illustrate the operating principle of the SAWFL device 101, which leverages ambient humidity and natural sunlight to enable decentralized production of clean water and green hydrogen, in greater detail. As shown, in use, the outward-facing solar PV panel 104 can be oriented toward incident sunlight, converting solar energy into electricity while generating waste heat. The proton exchange membrane (PEM) 106 can be disposed on an opposite side of the hydrogel 102 from the PV panel 102. The PEM 106 can be configured to perform electrolysis on desorbed water received from the hydrogel 102 to split the desorbed water into hydrogen and oxygen. The PEM 106 can be associated with a condenser, e.g., heat sink condenser 107. with the PEM 106 being disposed on top of. inside, and / or at an angle relative to the condenser 107. For the purpose of this disclosure, it will be appreciated that the condenser 107 can function as a condensing heat sink, thereby serving a dual function of both a condenser and a heat sink. For example, in some embodiments, the condenser 107 can be a thermally conductive heat sink that allows for dual use of solar energy: high-energy photons generate electricity for hydrogen electrolysis, while low-energy photons are absorbed as heat to trigger hydrogel desorption and water release. The condenser 107 can establish a temperature gradient (T1-T3) necessary to drive vapor flow' and condensation. For example, the condenser 107 can capture water vapor from the hydrogel 102, condense it to liquid water during the desorption phase, and direct it to the PEM 106, as discussed in greater detail below.

[0044] In some embodiments, the hydrogel 102 can be embedded in a modular housing beneath the PV panel 104 and regenerate passively using incident solar heat. To minimize footprint of the device 101 and facilitate integration w ith compact hydrogen generation units.Attorney Docket No.: MIT 26048 PCT | 88212-427690 an air gap of about 20 to about 30 millimeters can be used between the hydrogel 102 and the condenser 107. can allow efficient vapor transport and maintaining thermal separation between stages. Moreover, the compact configuration can reduce volume and weight, enabling scalable deployment in off-grid environments.

[0045] In use, the solar PV 104 can provide power to the PEM 106, while the hydrogel 102 can serve dual functions as both a sorbent material and PV evaporative cooling solution. Notably, the decoupling of the PEM 106 and the sorbent components can allow the hydrogel 102 to function without needing electrolytes for electrolysis. This strategic integration can leverage advancements in both technologies, optimizing performance by capturing ambient vapor in the hygroscopic gel during nighttime when humidity peaks (i.e.. maximized water uptake). During daylight, solar energy can be converted to electricity by the PV 104, which powers the PEM 106, while excess heat can be transferred to the hydrogel 102, initiating evaporative cooling and / or desorption. This design can enable efficient vapor transport via natural convection and / or condensation through a passively and / or actively cooled condenser 107.

[0046] As shown, the PEM 106 can include an anode 103 and a cathode 105. To enable efficient water collection, a natural convection-driven vapor path directs the released moisture toward the condenser 107, where it is cooled either passively or actively and liquefied. The anode 103 can be decoupled from the condenser 107 such that water condensation is limited to a surface of the condenser 107. Gravity7then can feed and / or flow the condensed water to an anode side 103 of the PEM 106, where unincumbered water splitting can occur.

[0047] As shown, the system 100 of the present embodiments can replace the conventional top enclosure of the PEM electrolyzer (typically located on the anode side) with a hydrophilic wi eking interface, scaffold, or porous wick 110. By positioning the wick 1 10 as shown, pressure between the anode 1 3 and cathode 105 can be maintained, while a high porosity of the scaffold 110 can maximize whetting of the anode side, thereby keeping the cathode side dry. This wick 110 can ensure even wetting, sustain capillary-driven flow, and preserve pressure across the membrane during operation. In certain embodiments, the wick 110 can exhibit a porosity7betw een about 50% and about 95%, with a preferred range between about 70% and about 90%, and an average pore size of about 10 to about 400 pm, sufficient to generate capillary7pressures adequate for sustaining liquid supply to the catalyst layer withoutAttorney Docket No.: MIT 26048 PCT | 88212-427690 external pumping. The high porosity of the wick 110 can enhance water distribution to the catalyst sites while minimizing mass transport limitations and ohmic losses.

[0048] As shown, the wick 110 can be in direct contact with the hygroscopic hydrogel 102 and can serve two roles: (i) it continuously replenishes water to the anode 103 via capillary- driven transport from the desorbing hydrogel 102. compensating for water consumed during electrolysis, and (ii) it maintains persistent hydration of the PEM 106, which can sustain ionic conductivity and avoid membrane dry -out under variable humidity conditions.

[0049] Additionally, the physical presence of the wick 110 can introduce a mild compressive preload at a membrane-electrode assembly interface 112. This mechanical contact can be used to maintain intimate contact between the anode 103 and a surface of the PEM 106, especially in the absence of active water pressurization. Without sufficient pressure at the anode-PEM-cathode junction, hydrogen generation can cease due to increased contact resistance and water transport inefficiencies. The passive preload from the wick 110 can ensure stable membrane hydration and consistent electrochemical performance.

[0050] Replacing the conventional top enclosure of the PEM electrolyzer 106 with the wick 110 can enable a >45 % increase in current density at ~ 1.85 V compared to a regular PEM 106, highlighting a significant enhancement in ionic conductivity and reduced interfacial resistance. Among the various configurations of the PEM 106 that were tested — including PEMs embedded in a saturated wi eking column and PEMs with foam-based wicks at a 45° tilt — to simulate vertical and lateral water redistribution under passive operation. These arrangements can also minimize local dry -out and improved overall system consistency, especially used for off-grid or intermittently powered systems where active cooling, rehydration, or pumping infrastructure is unavailable.

[0051] Further still, the hydrophilic wick 110 can be designed with an integrated overflow port (not shown) at its upper boundary to manage excess water produced during high- humidity7or over-generation conditions. For example, when the rate of water desorption from the hydrogel 102 exceeds the uptake capacity of the PEM electrolyzer 106, surplus liquid accumulates at the interface with the wick 110. Rather than saturating the membrane or disrupting electrolyzer operation, this excess water can be passively diverted through the overflow port into a secondary7collection reservoir. This can ensure uninterrupted hydrogen generation while simultaneously enabling parallel potable water production. The dual-outputAttorney Docket No.: MIT 26048 PCT | 88212-427690 configuration can enhance the overall water utilization efficiency of the system 100 and can make the device 101 suited for deployment in regions requiring both clean fuel and drinking water from ambient air and sunlight alone.

[0052] The device 101 can facilitate energy and mass transfer throughout the cyclical day- night operation. As shown in FIG. 2A, and discussed above, during nighttime, the hygroscopic hydrogel 102 can passively capture moisture from ambient air, driven by elevated relative humidity. As solar irradiance increases during the day, low-grade heat from the PV panel 104 can be transferred to the hydrogel 102, triggering water desorption to drive both electrical output and thermal regeneration of the hydrogel, releasing water vapor. Simultaneously, electricity produced by the PV panel 104 can be directed to the PEM electrolyzer 106, positioned downstream from the hydrogel 102. The desorbed vapor condenses into liquid water and is delivered to the anode 103 of the PEM electrolyzer 106. This clean water serves as the feedstock for electrolysis, while the PV -powered electrolyzer 106 can drive hydrogen evolution at the cathode 105. The modular and compact configuration of the SAWFE device 101 can avoid the need for external power, water, or grid infrastructure, enabling off-grid hydrogen and water production from sunlight and air alone. The system 100 can therefore maximize energy utilization, reduce component redundancy, and offer a compact, self-contained solution for co-producing water and hydrogen in remote and resource-limited settings.

[0053] It will be appreciated that the PV panel 104 can be experimentally matched and scaled to the PEM electrolyzer 106 to ensure electrical compatibility under real-world irradiance conditions. The operating current and voltage of the PV cell 104 can be aligned with the PEM's polarization behavior, allowing direct coupling without the need for intermediate power conditioning circuitry. This direct integration can minimize electrical losses and enable efficient energy transfer from solar to electrochemical domains.

[0054] FIG. 3 illustrates a spectral distribution of solar energy that shows the dual use of high-energy photons for photovoltaic electricity generation and low-energy' photons for photothermal w ater release. As shown, high-energy photons can photovoltaic conversion to power hydrogen production while low-energy photons can be captured as photothermal heat to regenerate the sorbent and release water on site. A band gap can occur between the high- energy and the low-energy7photons to define a threshold at which photons contribute to electronic excitation in the photovoltaic material, with photons above the band gap drivingAttorney Docket No.: MIT 26048 PCT | 88212-427690 electricity' generation and photons below the band gap contributing primarily to thermal energy. This separation can allow for simultaneous utilization of the full solar spectrum, wherein higher-energy photons maximize electrical output for electrolysis while lower- energy photons enable efficient desorption of water from the sorbent. In certain embodiments, spectral splitting, wavelength-selective coatings, or photonic structures can be incorporated to further direct and optimize the partitioning of photons toward either photovoltaic conversion or photothermal water harvesting.

[0055] To further characterize system performance, the operating point of the system 100 can be evaluated, with the operating point being a location where an output current of the PV cell 104 and voltage match the input demand of the PEM 106 — defining the system’s realtime hydrogen production rate and its solar-to-hydrogen (r|sm) efficiency. The equation governing this efficiency is:Rate of H2production x Gibbs Free Energy (or HHV) STH^0) —Total Solar Irradiation X areawhere AG is the Gibbs free energy (or HHV) of hydrogen, and Gsoiar is the incident irradiance. Simulations and experiments to test these values, in some embodiments, can be conducted under ideal laboratory' conditions, using standard 1 sun illumination, direct PV- PEM electrical coupling, and optimized thermal environments.

[0056] FIG. 4 A offers another illustration of the operation of the device 101 during an example sorption-desorption process. As shown, the gel sorbent 102 can capture water vapor during nighttime or low-light conditions, and upon exposure to sunlight, desorb liquid water that is routed via the overflow conduit 117 to the electrolyzer cell 109. As shown, the PV 104 and the gel sorbent 102 can be separated by a heat spreader 120, which can serve as a conductor while maintaining the seal inside the device 101. A detailed discussion of the heat spreader can be found below with respect to FIG. 6A.

[0057] The electrolyzer cell 109 can produce hydrogen 115 for storage in the storage tank 113, while excess water 111 can be collected for secondary uses. FIG. 4A therefore highlights the integrated nature of the system 100, demonstrating both day-night cycling and multifunctional water routing. FIG. 4B further illustrates exemplary water and hydrogen production performance over time. A person skilled in the art will appreciate that these figures are provided for completeness and enablement, and alternate schematic variations orAttorney Docket No.: MIT 26048 PCT | 88212-427690 datasets may also be applicable within the scope of the present embodiments. As shown, the PEM 106 can be an electrochemical cell or electrolyzer (EC) 109 that creates a voltage difference across the PV 104. As previously discussed, during daytime, after heat is absorbed by the PV 104, a temperature difference between the PV 102 and the condenser 107 can result in condensation being formed on a surface of the condenser 107. As show n, in some embodiments, the condensed water can be fed, for example via gravity, from a spigot 111 out of the condenser 107 as potable water, e.g., in an event of an overflow, while the hydrogen gas product can be collected into the storage unit 113 for later use.

[0058] FIG. 5 provides further details of the hydrogen gas collection process around the EC 109. As shown, the anode 103 can be exposed to condensed water while the cathode 105 can remain isolated from liquid water to presen e efficient gas evolution. A hydrophilic foam wick 110 can be positioned to deliver w ater uniformly to the anode side of the proton exchange membrane (PEM), while maintaining structural support and capillary-driven flow. In this embodiment, the gel sorbent 102 can be situated adjacent to the enclosure to facilitate desorption and direct liquid transport. A condensing heat sink and associated thermal gradient (T1-T3) are illustrated to highlight the role of temperature differentials in driving water vapor flow and condensation. The enclosure can further allow for routing of hydrogen gas away from the PEM 106 to an outlet for collection.

[0059] Through implementation and validation of the device 101, optimization of the amount of SAWH materials is possible, as is reducing the device footprint to deliver low-cost off-grid hydrogel production and additional water production for secondary’ purposes (e.g., drinking, agriculture, cooling, etc.). Water and hydrogen production can increase, as shown in FIG. 4B, with curve (A) showing w ater production during the absorption phase and curve (B) showing hydrogen production during the desorption phase. As shown, while there is a delay in the start of the desorption phase, hydrogen production amounts can increase quickly over time, with volumes of up to 400 millimeters being produced in about 300 to about 350 minutes. The near-linear trend of water production (A) indicates consistent release kinetics of the sorbent material, while the subsequent rise of hydrogen production (B) demonstrates efficient coupling betw een desorbed w ater and electrochemical conversion. In certain embodiments, optimization of sorbent loading, thermal management, or PEM wetting can reduce the observed lag period, thereby enabling faster startup and higher yield. Further, the correlation between curves (A) and (B) illustrates that water harvested on-site can be directlyAttorney Docket No.: MIT 26048 PCT | 88212-427690 converted into hydrogen without requiring external purification, highlighting the dual functionality of the device for both energy and water security.

[0060] FIGS. 6A-6B illustrate operation of the device 101 of FIGS. 1 A-1B with component temperatures as a function of solar flux, the daytime humidity, experimental hydrogen productivity compared to daytime solar flux, and intermittent PV-PEM electrical performance during the device operation cycle, respectively. FIG. 6A in particular illustrates heat and mass transport of the system with relative dimensions of the device 101, in which T is the location of the thermocouple during experimentation and t is the thickness of each section. Further, values of PV, plate, gel, v, cond. foam, and fin represent the photovoltaic, heat spreader plate 120, hygroscopic hydrogel 102, vapor, condenser porous aluminium foam and condenser fin, respectively. It is noted that the plate 120 can operate as a heat spreader or transfer layer positioned between the PV 104 and the hydrogel 102 to ensure efficient thermal transfer from the photovoltaic cell 104 into the hydrogel layer 102 for water desorption, while also acting as a sealing barrier to prevent vapor leakage during water generation. In certain embodiments, the plate 102 may also function as a detachable interface, enabling PV replacement or servicing without requiring permanent bonding or mechanical fasteners. Thus, when direct screw-mounting of the PV is impractical, the plate 120 can provide a preferred modular attachment solution. Following operation of the device 101. hydrogen can be collected in the storage unit 1 13, which can be a graduated cylinder as shown in the time lapse of FIG. 6B. In the present embodiments, a total of about 1,000 millileters can be collected over about six and a half hours, though it will be appreciated that the amount can be varied based on adjustments made to operation of the system 100.

[0061] It will be appreciated that the system 100 of the present embodiments can be PV- PEM limited. That is, while the system can supply both energy and potable fresh water, an amount of hydrogen that the system 100 produces can be tuned as desired. For example, in some embodiments, the system 100 can be toggled between maximum hydrogen production and more efficient water harvesting. When hydrogen production is at its maximum, water harvesting rates can be diminished and when hydrogen production is at its minimum, water harvesting rates can be increased due to the hydrogen that is being produced by the instant system being put towards conversion into water. It will be appreciated, however, that for purposes of the present disclosure, the instant system will most often be operated with theAttorney Docket No.: MIT 26048 PCT | 88212-427690 target of increasing hydrogen production due to the goal of superior water harvesting being more efficient.

[0062] TESTING AND RESULTS

[0063] To validate the feasibility’ and scalability of the device 101 in real-world conditions, two different PV modules were experimentally tested: a 1 10 mm x 60 mm cell and a larger 120 mm x 110 mm cell. These modules were selected based on their commercial availability and optimal matching to the PEM's electrical requirements to maximize operating point alignment and system efficiency. The 120 x 110 mm module, which was integrated into the prototype of FIGS. 1 A-1B, demonstrated a peak hydrogen generation rate of 343 mL / hr and a total yield of 1.5 L over 7.5 hours of operation — equivalent to 880 L / m2PEM / day. Simultaneously, it generated more water (917 mL / m2gel / day) than was required for PEM operation, confirming the potential to scale the system for simultaneous water and fuel production. A smaller 110 x 60 mm module also delivered stable hydrogen generation, achieving a peak rate of -230 mL / m2PEM / hr and total daily hydrogen output approaching 1.2 L, with consistent internal thermal gradients and PV-PEM electrical matching.

[0064] These two modules highlight the flexibility and robustness of the architecture of the device 101, confirming that a modular scaling approach with varying PV sizes can still yield high solar-to-hydrogen (STH) efficiencies. Across tests, STH efficiencies between 9% to 13% were recorded in ambient conditions, with modeled ideal PV-PEM combinations exceeding 20% and hydrogen production rates over 220 L / mPEM2 / h approaching the theoretical maximum of -240 L / mPEM2 / h under 1 sun conditions, both under realistic assumptions. These values were achieved without the need for desalination, active water management, or external infrastructure, relying solely on ambient humidity7and solar flux. Moreover, device enhancements, such as the replacement of the PEM top cover with the hydrophilic aluminum wick 110, enabled a >45% increase in electrolyzer current density by promoting sustained hydration and pressure-enhanced contact at the membrane-electrode interface. This design improvement simplifies the system by eliminating use of active compression or hydration controls and offers passive stability under tilting or off-angle solar conditions, which is critical for practical field deployment.

[0065] The values of the system 100 and device 101 of the present embodiments outperformed conventional seawater-to-hydrogen platforms w hile eliminating the energyAttorney Docket No.: MIT 26048 PCT | 88212-427690 penalty of salt removal, and maintain a modular and deployable configuration. This performance surpasses many traditional photocatalytic systems and matches or exceeds the reported output of seawater electrolysis platforms, without the added complexity or energy burden of desalination and pressurization systems.

[0066] Examples of the above-described embodiments can include the following:1. A hydrogen production system, comprising: a sorbent-based atmospheric water harvesting material; one or more photovoltaic (PV) cells; a condenser configured to capture water vapor from the sorbent-based atmospheric water harvesting material; a heat sink; and a hydrogen production cell having a photovoltaic (PV) electrolyzer circuit comprising a proton exchange membrane (PEM) that is configured to perform electrolysis on desorbed water received from the sorbent-based atmospheric water harvesting material to split the desorbed water into hydrogen and oxygen.2. The system of example 1, wherein the hydrogen production system is configured to simultaneously harvest water and produce hydrogen.3. The system of example 1 or example 2, further comprising a storage unit configured to store the hydrogen.4. The system of example 2 or example 3, wherein the water is condensed by gravity.5. The system of any of examples 1 to 4, wherein the sorbent-based atmospheric water harvesting material is a PAM-LiCl hydrogel.6. The system of example 5, wherein the PAM-LiCl hydrogel is deployed as a coating on the one or more PV cells or within a separate dedicated unit.7. The system of any of examples 1 to 6, wherein the one or more PV cells are configured to capture solar energy to generate electricity while simultaneously desorbing water from the sorbent material.Attorney Docket No.: MIT 26048 PCT | 88212-4276908. The system of any of examples 1 to 7, wherein the sorbent-based atmospheric water harvesting material is disposed between the one or more PV cells and the condenser.9. The system of any of examples 1 to 8, wherein the sorbent-based atmospheric water harvesting material is disposed between the one or more PV cells and the PEM.10. The system of any of examples 1 to 9, wherein the sorbent-based atmospheric water harvesting material is disposed between the PEM and the heat sink.11. The system of any of examples 1 to 10, wherein the hydrogen production system has a water production capacity of about lL / m2 / day and a hydrogen production capacity of about 5 ml / min.12. The system of any of examples 1 to 11, wherein the system is configured to operate passively.13. A method of hydrogen production, comprising: absorbing moisture from a condenser surface using a hydrogel; exposing one or more photovoltaic (PV) cells that are associated with the hydrogel to incident solar irradiation to convert the solar irradiation to electricity; using the electricity, powering a hydrogen production cell having a photovoltaic (PV) electrolyzer circuit comprising a proton exchange membrane (PEM) to form a hydrogen product, heating the hydrogel using excess heat from the one or more PV cells to desorb a condensed water from the hydrogel; and collecting the hydrogen product.14. The method of example 13, wherein the hydrogen product and the condensed water are formed simultaneously.15. The method of example 13 or example 14, wherein hydrogen production occurs on a daily cycle, in which absorption occurs when the hydrogel is exposed to nighttime ambient air, and desorption occurs during daytime.16. The method of any of examples 13 to 15, further comprising feeding the condensed water to a cathode side of the PEM to facilitate water splitting via electrolysis.Attorney Docket No.: MIT 26048 PCT | 88212-42769017. The method of example 16, wherein the condensed water is fed to the cathode side by gravity.18. The method of any of examples 13 to 17, adjusting one or more of ambient temperature, ambient air flow, voltage, or current to one of increase or decrease an amount of hydrogen product produced.19. The method of example 18, wherein increasing the amount of hydrogen product produced decreases an amount of condensed water formed.20. The method of any of examples 13 to 19, further comprising adjusting a composition of the hydrogel based on one or more of ambient temperature, ambient air flow, voltage, current, assumptions on solar input, or breeze data.21. The method of example 20, wherein adjusting the composition of the hydrogel further comprises altering one or more of a thickness or consistency of the hydrogel.22. The method of any of examples 13 to 21, further comprising optimizing hydrogen production by performing one or more of heat and mass transfer analyses, PV to proton exchange membrane (PEM) scaling, or hydrogel to hydrogen production comparisons.23. The method of example 22, further comprising maintaining adequate pressure between an anode and a cathode of the hydrogen production cell during optimization.24. The method of any of examples 13 to 23, further comprising optimizing a size ratio of the one or more PV cells to a size of the hydrogel to ensure that the desorbed water forms condensed water in the PV electrolyzer circuit.

[0067] One skilled in the art will appreciate further features and advantages of the disclosures based on the provided for descriptions and embodiments. Accordingly, the inventions are not to be limited by what has been particularly shown and described. To the extent the present disclosure includes illustrations and descriptions that include prototypes, bench models, or schematic illustrations of set-ups, a person skilled in the art will recognize how to rely upon the present disclosure to integrate the techniques, systems, composition,Attorney Docket No.: MIT 26048 PCT | 88212-427690 designs, and methods provided for into a product and / or production method. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

[0068] Some non-limiting claims that are supported by the contents of the present disclosure are provided below.

Claims

Attorney Docket No.: MIT 26048 PCT | 88212-427690We claim:

1. A hydrogen production system, comprising: a sorbent-based atmospheric water harvesting material; one or more photovoltaic (PV) cells; a condenser configured to capture water vapor from the sorbent-based atmospheric water harvesting material; a heat sink; and a hydrogen production cell having a photovoltaic (PV) electrolyzer circuit comprising a proton exchange membrane (PEM) that is configured to perform electrolysis on desorbed water received from the sorbent-based atmospheric water harvesting material to split the desorbed water into hydrogen and oxygen.

2. The system of claim 1, wherein the hydrogen production system is configured to simultaneously harvest water and produce hydrogen.

3. The system of claim 1. wherein the sorbent-based atmospheric water harvesting material is a PAM-LiCl hydrogel.

4. The system of claim 3. wherein the PAM-LiCl hydrogel is deployed as a coating on the one or more PV cells or within a separate dedicated unit.

5. The system of claim 1. wherein the one or more PV cells are configured to capture solar energy to generate electricity while simultaneously desorbing water from the sorbent material.

6. The system of claim 1, wherein the sorbent-based atmospheric water harvesting material is disposed between the one or more PV cells and the condenser.

7. The system of claim 1. wherein the sorbent-based atmospheric water harvesting material is disposed between the one or more PV cells and the PEM.

8. The system of claim 1. wherein the hydrogen production system has a water production capacity of about l L / m2 / day and a hydrogen production capacity of about 5 ml / min.

9. The system of claim 1, wherein the system is configured to operate passively.Attorney Docket No.: MIT 26048 PCT | 88212-42769010. A method of hydrogen production, comprising: absorbing moisture from a condenser surface using a hydrogel; exposing one or more photovoltaic (PV) cells that are associated with the hydrogel to incident solar irradiation to convert the solar irradiation to electricity; using the electricity, powering a hydrogen production cell having a photovoltaic (PV) electrolyzer circuit comprising a proton exchange membrane (PEM) to form a hydrogen product, heating the hydrogel using excess heat from the one or more PV cells to desorb a condensed water from the hydrogel; and collecting the hydrogen product.

11. The method of claim 10, wherein the hydrogen product and the condensed water are formed simultaneously.

12. The method of claim 10, wherein hydrogen production occurs on a daily cycle, in which absorption occurs when the hydrogel is exposed to nighttime ambient air, and desorption occurs during daytime.

13. The method of claim 10. further comprising feeding the condensed water to a cathode side of the PEM to facilitate water splitting via electrolysis.

14. The method of claim 13, wherein the condensed water is fed to the cathode side by gravity.

15. The method of claim 10, adjusting one or more of ambient temperature, ambient air flow, voltage, or cunent to one of increase or decrease an amount of hydrogen product produced.

16. The method of claim 15. wherein increasing the amount of hydrogen product produced decreases an amount of condensed water formed.

17. The method of claim 10. further comprising adjusting a composition of the hydrogel based on one or more of ambient temperature, ambient air flow, voltage, current, assumptions on solar input, or breeze data.Attorney Docket No.: MIT 26048 PCT | 88212-42769018. The method of claim 10, further comprising optimizing hydrogen production by performing one or more of heat and mass transfer analyses, PV to proton exchange membrane (PEM) scaling, or hydrogel to hydrogen production comparisons.

19. The method of claim 10, further comprising maintaining adequate pressure between an anode and a cathode of the hydrogen production cell during optimization.

20. The method of claim 10, further comprising optimizing a size ratio of the one or more PV cells to a size of the hydrogel to ensure that the desorbed water forms condensed water in the PV electrolyzer circuit.

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