Green hydrogen generation by metal-assisted two-step water splitting for portable hydrogen power stations, hydrogen refueling stations, and other applications

Abstract

Methods of producing hydrogen, comprising: contacting water and at least one of activated Zn and activated Fe under conditions sufficient to give rise to molecular hydrogen and the corresponding oxide of at least one of the activated Zn and activated Fe. A method of generating power, comprising: contacting water and at least one of activated Zn and activated Fe under conditions sufficient to give rise to molecular hydrogen and the oxide of the at least one of the activated Zn and activated Fe; effecting power generation from a fuel cell with the molecular hydrogen; optionally using at least some of the power evolved from the fuel cell to reform at least some of the oxide of the at least one of the activated Zn and activated Fe to the at least one of the activated Zn and activated Fe.

Description

GREEN HYDROGEN GENERATION BY METAL-ASSISTED TWO-STEP WATER SPLITTING FOR PORTABLE HYDROGEN POWER STATIONS, HYDROGEN REFUELING STATIONS, AND OTHER APPLICATIONSRELATED APPLICATIONS

[0001] The present application claims priority to and the benefit of United States patent application no. 63 / 600,171, “Green Hydrogen Generation By Metal -Assisted Two- Step Water Splitting For Portable Hydrogen Power Stations, Hydrogen Refueling Stations, And Other Applications,” filed November 17, 2023. All foregoing applications are incorporated herein by reference in their entireties for any and all purposes.GOVERNMENT RIGHTS

[0002] This invention was made with government support under 2047851 awarded by the National Science Foundation. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present disclosure relates to the field of materials science and to the field of hydrogen generation.BACKGROUND

[0004] At present the field of hydrogen generation and storage faces a number of challenges. A challenge with green hydrogen production is that large scale production of green H2 (e.g., at the rate of thousands of kilograms of H2 per hour) can be comparatively expensive. Consequently, over 95% of the H2 produced worldwide is not green H2 but is grey H2, produced through a non-sustainable process involving steam reforming of natural gas and co-production of CO2, a major greenhouse gas.

[0005] A further challenge relates to hydrogen storage in that even if green H2 is produced at a large scale, effectively storing this H2 is not straightforward because H2 is a low-density gas at room temperature and it takes up a lot of space, meaning that H2 needs to be compressed in pressurized gas cylinders / tanks before the uses. H2 compression,however, can consume over 30% of the total energy required. Furthermore, the storage capacity of compressed H2 tanks is restricted due to safety considerations associated wi high-pressure flammable gases. Although solid-state H2 storage has been proposed as ; alternative way to store H2, materials that can reversibly store and release H2 at practice temperatures and pressures are still under development. Thus, at the present time, the 1 of pressurized gas cylinders is the most practical approach to store H2 for on-site and 01 board applications.

[0006] Additionally, hydrogen infrastructure presents challenges in that new applications such as electric vehicles and drones powered by H2 fuel cells suffer from tl lack of H2 refueling infrastructures. For instance, in the U.S. there are currently only 6C functional H2 refueling stations, many of which are in California. Accordingly, there is long-felt need in the art for improved methods of hydrogen production.SUMMARY

[0007] In meeting the described long-felt needs, the present disclosure provid method of producing hydrogen, comprising: contacting water with at least one of active Zn and activated Fe under conditions sufficient to give rise to molecular hydrogen and corresponding oxide of the at least one of the activated Zn and activated Fe.

[0008] Also provided is a method of producing an activated metal, comprising at least one of (1) forming an admixture of a hydrogen evolution catalyst, and at least o of nanoporous Zn and Fe, so as to give rise to an activated one of the at least one of nanoporous Zn and Fe; and (2) contacting at least one of a ZnGa alloy and a FeGa alloA with carbon powder and a hydrogen evolution catalyst so as to give rise to an activated least one Zn and Fe.

[0009] Additionally provided is a method to form nanoporous Zn and / or nanoporous Fe, the method comprising contacting an amount of particulate Zn alloy or alloy with an alkaline solution, the contacting being performed under conditions suffici to give rise to nanoporous Zn or Fe. The method can be performed over the course of 1 few minutes, as opposed to a few days, like existing approaches.

[0010] Further provided is a method of reforming an activated material, comprising: applying an electrical voltage or a current to an oxide of activated Zn or activated Fe under conditions sufficient to give rise to molecular oxygen and thecorresponding activated metal. For green hydrogen generation, the voltage or current c: be obtained from green electricity (e.g., hydropower, solar power, wind turbine, sustainable electric grid).

[0011] Additionally provided is a method of generating power, comprising: contacting water and at least one of activated Zn and activated Fe under conditions sufficient to give rise to molecular hydrogen and the oxide of the at least one of the activated Zn and activated Fe; and effecting power generation from a fuel cell using the molecular hydrogen.

[0012] Also disclosed is a method of producing hydrogen, comprising: contacting water and at least one of activated Zn and activated Fe under conditions sufficient to give rise to molecular hydrogen and the oxide of the at least one of the activated Zn and activated Fe; and at least one of storing the molecular hydrogen and using the molecular hydrogen to effect power generation from a fuel cell.

[0013] Further disclosed is a water splitting reactor, the water splitting reactoi optionally configured for two-step operation, the water splitting reactor comprising a fi electrode for hydrogen evolution that comprises at least one of activated Zn and activat Fe with a hydrogen evolution catalyst, the water splitting reactor comprising a counter electrode for oxygen evolution that comprises an oxygen evolution catalyst, the two-ste water splitting reactor configured to (1) contact the first electrode and water so as to spontaneously evolve molecular hydrogen and the corresponding oxide of the least one activated Zn and activated Fe, and (2) communicate a current across the corresponding oxide of the least one of activated Zn and activated Fe so as to reform the metal of the corresponding oxide of the least one of activated Zn and activated Fe and give rise to molecular oxygen.

[0014] Without being bound to any particular theory or embodiment, one can any type of water (e.g., water containing salts, pure water) to produce hydrogen from activated metals, although acid and highly alkaline solutions can be susceptible to dissolving Zn and / or Fe. To convert metal oxide back to activated metal, one can use water containing at least a small amount of salt (e.g., with a pH of between 7 and 12), s that the water exhibits ionic conductivity.

[0015] Additionally disclosed is a power generation system, comprising: a fu( cell configured to evolve a current and voltage from hydrogen; and a water splittingreactor as described herein, the power generation system configured to communicate th molecular hydrogen from splitting reactor to the fuel cell to generate a current.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In the drawings, which are not necessarily drawn to scale, like numera may describe similar components in different views. Like numerals having different le suffixes may represent different instances of similar components. The drawings illustn generally, by way of example, but not by way of limitation, various aspects discussed ii the present document. In the drawings:

[0017] FIG. 1. Summary of scalable green H2 generation via two-step metal- assisted water splitting. Herein Zn is used as an example of metal. Step 1: metal hydro! in H2O to spontaneously produce H2 and a solid metal oxide by-product without the net of any electrical power. Step 2: Recovery of active metal from metal oxide in 5-15 minutes using clean electrical power.

[0018] FIGs. 2A-2B (low magnification): (FIG. 2A) low magnification image Z oAko at.% powder particles before scalable fabrication of nanoporous Zn by deallo} or selective leaching of Al. (FIG. 2B) Corresponding nanoporous Zn powder particles after selective removal of Al by dealloying.

[0019] FIGs. 3A-3B. (high magnification): (FIG. 3A) High magnification irm of Z oAleo at.% powder particles before selective removal of Al by dealloying. (FIG. Corresponding nanoporous Zn powder particles after selective removal of Al by dealloying.

[0020] FIG. 4 ICP (upper) and EDX (lower) analysis of pristine ZmoAleo at.0 / powder particles before and after selective removal of Al by dealloying, which confirm that most of the Al has been removed within 30 minutes with residual Al around 5 at.% less.

[0021] FIG. 5 XRD comparison of the pristine Zn-Al parent alloy, which contains Al and Zn two phases, and the dealloyed nanoporous Zn powder, which only contains Zn phase. More importantly, the Al peaks vanish within the first 10 minutes ol dealloying.

[0022] FIG. 6 H2 generation yield test shows that the yield is significantly enhanced by mixing nanoscale Zn powder with a small amount of Ni / C powder (red curve) or Pt / C powder (blue curve) used as a hydrogen evolution catalyst.

[0023] FIG. 7A. Real images of Znioo-xGaxalloy showing the activation proce towards spontaneous metal hydrolysis. The rapidly solidified Znioo-xGaxalloy in the let image can be crushed into particles. These mm-scale particles can be further ground in1 fine powder (activation process) with addition of carbon and H2 evolution catalyst as shown in the right panel of FIG. 7A.

[0024] FIG. 7B. Real images of (FIG. 7B(a) and 7B(b)) slurry electrodes usin PVDF / NMP binder and ZnO powder from hydrolyzed activated Zn (FIG. 7B(a)) befon and (FIG. 7B(b)) after delamination from Cu foil, (FIG. 7B(c)) ink electrode with PTF1 binder, and (FIG. 7B(d)) pellet-pressed electrode without binder.

[0025] FIGs. 8A-8B. (FIG. 8A) Typical cyclic voltammetry tests in IM NaOI from -2 V to -1 V vs. Hg / HgO at 5 mV / s using Hg / HgO reference electrode; (FIG 8B) Typical chronoamperometric curve obtained during the reduction of ZnO back to activ; Zn in IM NaOH at -1.8 V vs. Hg / HgO for 5 mins.

[0026] FIG. 9. (top) X-ray diffraction patterns before (blue curve) and after (black curve) the electroreduction of ZnO back to Zn in IM NaOH at -1.8 V vs. Hg / Hg The lack of ZnO peaks between 30 and 40 degrees in the black curve illustrates a comp reduction, (bottom) X-ray diffraction patterns of Fe before (black) and after (red) reach with water to produce hydrogen and iron oxide (Fe3O4).

[0027] FIGs. 10A-10B. Shortest reduction time tests in IM NaOH with varioi reduction time under the same potential at -1.8 V vs. Hg / HgO. From XRD patterns, Zn slurry electrode (FIG. 10A) can be fully reduced to Zn, in 15, 10, and 5 minutes due to lack of ZnO peaks from 30 to 40 degrees, but (FIG. 10B) is only partially reduced to Zi 4 and 3 minutes. Thus, the shortest time to fully reduce ZnO to Zn is 5 minutes.

[0028] FIG. 11. Simplified schematic of rechargeable H2 powerpack. Herein i is used as an example. Active metals reacting with H2O in the left part of setup product green H2 and a solid metal oxide by-product. Then, generated H2 is fed into a protonexchange membrane (PEM) fuel cell and reacts with air. Electrons released from such reaction are forced through external circuit and provide power for mobile applications.The reaction product in fuel cell, H2O, is pumped into left setup for recovery of active metal from metal oxide through electricity.

[0029] FIG. 12. Images of the portable hydrogen powerpack that supplies electricity to the drone. The Zn fuel reacts with NaOH solution and produces H2 in the black reaction chamber; then, the produced wet gas flows into a gas-liquid separator wl excess water is stored. The wet gas is dried through molecular sieves located under the black reaction chamber. The dried pure hydrogen is supplied to the fuel cell in the blue box to generate electricity. It powers the drone through the connection on top of the fue cell box.

[0030] FIG. 13. Image of an exemplary drone powered by the disclosed technology.

[0031] FIG. 14 provides high- and low-magnification SEM images of (FIG. 1 FIG. 14C) gas-atomized Zn-Al alloy particles before dealloying and (FIG. 14B, FIG. L nanoporous Zn (NP-Zn) particles after dealloying; FIG. 14D illustrates several hundred grams of activated NP-Zn powder made according to the present disclosure.

[0032] FIG. 15 illustrates the effect of Zn activation on H2 generation from th Zn-water reaction (FIG. 15 A) bulk Zn powder, (FIG. 15B) nanoporous Zn (NP-Zn) powder without Ni catalyst, (FIG. 15C) NP-Zn powder with Ni catalyst, (FIG. 15D) Ek generation yield of bulk Zn (trace A), NP-Zn (trace B), and NP-Zn with catalyst (traceDETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0033] The present disclosure may be understood more readily by reference t( the following detailed description of desired embodiments and the examples included therein.

[0034] Unless otherwise defined, all technical and scientific terms used hereir have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are described below, although methods and materials similar or equivalent to those described herein can be used in practice or testing. All publications patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting.

[0035] The singular forms “a,” “an,” and “the” include plural referents unless context clearly dictates otherwise.

[0036] As used in the specification and in the claims, the term "comprising" c include the embodiments "consisting of' and "consisting essentially of.” The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients / steps and permit the presence of other ingredients / steps. However, such description should be construed as also describing compositions or processes as "consisting of and "consisting essentially of the enumerated ingredients / steps, which allows the presence of only the named ingredients / steps, along with any impurities that might result therefrom, and excludes other ingredients / steps.

[0037] As used herein, the terms “about” and “at or about” mean that the amo or value in question can be the value designated some other value approximately or abc the same. It is generally understood, as used herein, that it is the nominal value indicati ±10% variation unless otherwise indicated or inferred. The term is intended to convey similar values promote equivalent results or effects recited in the claims. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and / or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measuremen error and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter or other quantity or characteristic is “about” or “approximate” whether or not expressly stated to be such. It is understood that where “about” is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise.

[0038] Unless indicated to the contrary, the numerical values should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value b less than the experimental error of conventional measurement technique of the type described in the present application to determine the value.

[0039] All ranges disclosed herein are inclusive of the recited endpoint and independently of the endpoints. The endpoints of the ranges and any values disclosedherein are not limited to the precise range or value; they are sufficiently imprecise to include values approximating these ranges and / or values.

[0040] As used herein, approximating language can be applied to modify any quantitative representation that can vary without resulting in a change in the basic fund to which it is related. Accordingly, a value modified by a term or terms, such as “abow and “substantially,” may not be limited to the precise value specified, in some cases. Ir least some instances, the approximating language can correspond to the precision of an instrument for measuring the value. The modifier “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, expression “from about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” can refer to plus or minus 10% of the indicated number. For example, “about 10%” can indicate a range of 9% to 11%, and “about 1” can mean from 0.9-1.1. Other meanings of “about” can be apparent from the context, such as rounding off, so, for example “about 1” can also mean from 0.5 to 1.4.

[0041] Further, the term “comprising” should be understood as having its ope ended meaning of “including,” but the term also includes the closed meaning of the ten “consisting.” For example, a composition that comprises components A and B can be i composition that includes A, B, and other components, but can also be a composition made of A and B only. Any documents cited herein are incorporated by reference in th entireties for any and all purposes.

[0042] Any embodiment or aspect provided herein is illustrative only and doe not limit the scope of the present disclosure or the appended claims. Any part or parts < any one or more embodiments or aspects can be combined with any part or parts of any one or more other embodiments or aspects.

[0043] The disclosed technology addresses the challenges described herein. ( objective of the disclosed technology is to produce H2 when needed (on-demand, onboard, on-site) by taking advantage of the fact that some metals and metalloids can spontaneously react with water to generate three products as shown in Table 1 in the ca of aluminum (Al), magnesium (Mg), zinc (Zn), and iron (Fe). Those three reaction products are:

[0044] H2gas

[0045] A solid by-product in the form of metal oxide / hydroxide, and

[0046] Heat

[0047] To mitigate the issues associated with H2 storage, compression, delive and transportation, in the past decades, various scientists and engineers have proposed using metal-water reactions (also referred to as metal hydrolysis) to produce H2 on- demand, on-board, and on-site. This approach is attractive because it is easier and safer handle and transport metals and water to produce H2 when needed, compared with handling and transporting compressed flammable H2 gas. The metal-water reaction has to attain prevalence in the H2 production field, however. Without being bound to any particular theory or embodiment, this may be because of the following issues:

[0048] Although thermodynamically these metal-water reactions can proceed practice, the kinetics of these reactions is very sluggish. This is partly because once the reaction between the metal and water starts, the metal oxide / hydroxide solid by-produccan form a conformal water-blocking coating around the metal, which prevents water f coming into direct contact with the metal underneath. Therefore, the metal must be activated to enable the metal-water reaction to proceed with a high H2 generation rate. ' disclosed technology provides methods to activate zinc (Zn) and iron (Fe).

[0049] Most metal-water reactions are highly exothermic, and consequently inefficient. For example, in the case of the aluminum -water reaction, the energy associi with the amount of heat released is the same as the energy contained in H2 generated, h other words, the aluminum -to-FF energy efficiency (defined as the energy content of FL generated from the aluminum-water reaction divided by the total energy content of aluminum) is only 50%. The remaining 50% of energy is released as heat. If this heat is not harvested and converted into a useful form of energy (such as heat-to-electricity), tl the energy efficiency of the aluminum-water reaction will not be higher than 50% (see first row of Table 2 for details).

[0050] In fact, even if the heat released from the aluminum-water reaction is harvested for reuse, only a fraction of that heat (around 30%) can be effectively reused since the efficiency of practical state-of-the-art heat harvesting systems is usually arour 30%. As non-limiting examples of the present disclosed technology, we use the zinc- water and iron-water reactions, which are significantly less exothermic and thus more efficient. For example, the amount of heat released during the reaction of zinc with wat is only 13% of the total energy content of zinc. Hence, the corresponding zinc-to-H2 efficiency is 83% (see second row, Table 2 for details). Further, the amount of heat released during the reaction of iron with water is around 7% of the total energy content iron. Hence, the corresponding iron-to-H2 efficiency is 93% (see third row, Table 2 for details).

[0051] Metal-water reactions are one-way reactions, meaning that when the metal reacts with water to produce H2 and the corresponding metal oxide / hydroxide, th metal oxide / hydroxide cannot be recycled / regenerated on-board or on-site for reuse. Hence metal-water reactions are single-use. In this disclosed technology, we provide ai effective and fast method to regenerate / recycle the Zn oxide solid by-product on-demai on-board, or on-site from the zinc-water reaction for reuse, as well as regenerating / recycling the Fe oxide solid by-product from the iron-water reaction for reuse.

[0052] Further details of this disclosed technology are provided below, using exemplary, non-limiting features.

[0053] Feature 1

[0054] A first feature of this disclosed technology is a scalable method to produce green H2 via an innovative two-step water-splitting process. In the first step or hydrogen evolution step (which we also refer to as the discharge step), activated Zn or activated Fe spontaneously reacts with water or with any other aqueous solution to produce H2 and the corresponding metal oxide, such as zinc oxide (ZnO) for the reactic between activated Zn and water, and iron oxide (e.g., FesCU, or / and Fe2O3, as shown in FIG. 9, bottom panel) for the reaction between activated Fe and water.

[0055] In the case of activated Zn, for example: During the reaction between activated Zn and water molecule (H2O), Zn traps the oxygen atom from H2O to become ZnO, releasing H2 gas in the process. This first step is the hydrogen evolution step (whi we also refer to as the charge step), illustrated in FIG. 1 (top).

[0056] The second step is the oxygen evolution step (which we also refer to a the charge step). In this second step, clean electrical power is used to release the oxygei atom that was trapped by Zn in the form of ZnO, regenerating in that way activated Zn. Regenerated Zn can be reused multiple times. This second step is illustrated in FIG. 1 (bottom). Like with the conventional approach to split water into H2 and O2 by one-ste] water electrolysis, during our two-step water splitting, H2O is also split into H2 (step 1) and O2 (step 2). H2 produced through our two-step water-splitting process is green H2 because clean electrical power is used, and the two steps do not involve CO2 emissions By comparison, producing a large amount of green H2 (e.g., at the rate of thousands of kilograms of H2 per hour) using conventional one-step water electrolyzers is challengin and requires a considerable investment. This is mainly because since in conventional 01 step water electrolyzers, H2 and O2 gases are produced simultaneously, sophisticated membranes known as proton exchange membranes (PEMs) or anion exchange membra (AEMs), depending on the pH, are required to separate the H2 and O2 gases produced.

[0057] For the two-step water-splitting technology disclosed here, a membran not required to separate H2 and O2 because these two gases are not released at the same time. Another advantage of the disclosed process is that a large amount of green H2 cai produced during the discharge step (step 1) and without the need for electrolyzers, andwithout the need of electricity, simply by bringing a large amount of activated Zn in contact with water. Spent Zn (i.e., the ZnO solid by-product) can be regenerated in at 1< 5 minutes in step 2, as will be demonstrated later. Besides activated Zn metal, activated metal can also be used to split water in a similar two-step process. Compared to conventional one-step water electrolyzers, another significant advantage of the disclose two-step water-splitting technology is that hydrogen production and electricity consumption are decoupled. In other words, electricity is not required to produce hydrogen; electricity is only needed to regenerate the spent ZnO back to Zn. Therefore, disclosed two-step water splitting technology can be used to produce cheaper hydrogen without electricity, during peak electricity demand (when grid power electricity is expensive), and only use electricity to convert the ZnO back to Zn during off-peak how when grid power is the cheapest. In contrast, conventional one-step water electrolyzers continually need electricity to produce hydrogen, including during peak hours when demand for electricity is the highest.

[0058] Finally, it is worth comparing the water-splitting technology disclosed here with existing state-of-the-art two-step water-splitting technologies. During an existing process, in step 1, electricity is used to produce hydrogen from Ni hydroxide - Ni(0H)2 , which is then converted into Ni oxyhydroxide — NiOOH when it captures oxygen from water; in step 2, heat is used to spontaneously convert the NiOOH back tc Ni(0H)2 and release oxygen without using electricity. Because both H2 and O2 are not produced simultaneously, that technology does not require a membrane to separate thes two gases, like with the two-step water-splitting technology disclosed here. But unlike technology disclosed here, that technology does not decouple hydrogen production fror electricity consumption. Therefore, that technology cannot spontaneously produce hydrogen on-board, on-demand, or on-site when there is no electricity available, unlike two-step water splitting technology disclosed here.

[0059] Feature 2

[0060] A second feature is on two methods to activate Zn and Fe metal to ena them to spontaneously react with water to produce green H2.

[0061] Method 1 : Scalable Zn activation via nanoporosity formation in combination with a hydrogen evolution catalyst.

[0062] A challenge in making nanoporous metals for practical applications is scalability of the process - although a few milligrams of nanoporous metals can be mac at the laboratory scale, it is often very difficult to make kilograms of nanoporous metali for large-scale applications.

[0063] The present feature resolves the scalability issue by significantly reduc the dealloying time from several days down to 10-30 minutes. Thus, in doing so, one c reduce the size of the starting Zn-Al parent alloy from a bulk piece of alloy (with thicki of the order of a few millimeters) down to micro-sized alloy powder particles with size the range of 5-200 pm using gas atomization techniques. Making alloy powder by gas atomization is a scalable process, used in industry.

[0064] As a non-limiting example, we used 2 kg of commercial ZnxAlioo-x at. (where 10<x<60) alloy powder (made by gas atomization) to make nanoporous Zn in a scalable manner. This powder has spherical Zn-Al particles with size between 5-50 pm FIG. 2A shows typical spherical powder particles at a low magnification for the composition of Z oAleo at. % (i.e., when x=40); and FIG. 3 A shows a spherical Zn4oA at.% alloy particle at a much higher magnification. Two phases can be observed on the high magnification image in FIG. 3a, namely a light phase (which is a Zn-rich phase), z a dark phase (which is an Al-rich phase). Phase-separated starting materials - such as tl starting materials described here - are considered particularly suitable, but are not required. Next, the Zn-Al powder is introduced in an aqueous solution of sodium hydroxide (NaOH), or other alkaline solution, with molarity in the range of 0.5-3 M to selectively etch away Al from the alloy, a process known as dealloying. Because the particle size in the starting Zn-Al parent alloy is in the micrometer range (for example, from 1 to 10 pm in size), during dealloying, it takes only 10-30 minutes to remove mos the sacrificial Al and results in acceptable residual Al around 5% or less. (By contrast, : can take days to remove Al from bulk Zn-Al).

[0065] We used Inductively Coupled Plasma (ICP) and Energy Dispersive X- spectroscopy (EDX) to confirm that most of the Al had been removed within 10-30 minutes, with acceptable residual Al around 5 at or less, as shown in FIG. 4. Besides th chemical composition, we used X-ray diffraction (XRD) techniques to confirm that bef dealloying, the starting Zn-Al parent alloy contains two phases (Al-rich phase and Zn-r phase), and after dealloying, the corresponding nanoporous Zn powder contains only oiphase, namely Zn phase, as shown in FIG. 5. It can be seen from the red (10-minute) X curve in FIG. 5 that the Al peaks vanish within the first 10 minutes of dealloying, confirming that 10 minutes are sufficient to make nanoporous Zn in the powder form, a opposed to several days when nanoporous Zn is made in the bulk form.

[0066] It should be understood that although the foregoing example utilizes spherical Z oAleo at.% alloy particles, such particles are not a requirement, as other particles - such as FexAlioo-x - can be used. Such particles can be treated with alkaline solution to etch Al away from the alloy, leaving nanoporous Fe behind.

[0067] Further activation of the synthesized nanoporous Zn to enhance the rat of hydrogen generation during its reaction with water: As previously reported, the rate H2 generation using pure nanoporous Zn is relatively low. Without being bound to any particular theory or embodiment, this is because pure Zn is not intrinsically a good hydrogen evolution material, even in the nanoscale format, as illustrated by the black curve in FIG. 6, which shows the relatively low H2 generation yield of nanoscale Zn. Therefore, to fully activate nanoscale Zn, one can introduce a small amount of H2 evolution catalyst. The following are example ways of doing so.

[0068] First way: By mixing nanoscale Zn powder with a small amount of NL powder or Pt / C powder used as a hydrogen evolution catalyst, the H2 generation yield i significantly enhanced as shown in by the blue curve (B; for Pt / C catalyst) and red cun (C; for Ni / C catalyst) in FIG. 6. Thus, we activate our nanoporous Zn powder by mixin with commercial Ni / C and Pt / C powder (Vulcan Pt / C with Pt-to-C ratio between 1 :100 and 40: 100 in weight percentage, including all intermediate ratios and ranges of ratios) Besides Ni / C and Pt / C, other common H2 evolution catalysts can be used as well. Othe such catalysts include, without limitation, ruthenium, iridium, cobalt, molybdenum disulfide (M0S2), tungsten carbide (WC), copper, iron, and nickel phosphide (Ni2P).

[0069] Second way: Direct introduction of Ni or Pt catalyst in the Zn-Al parei alloy before dealloying. Instead of adding the Ni / C or Pt / C catalyst in the dealloyed nanoporous Zn powder, Ni or Pt can be added in the starting ZnxAlioo-x at. % (where 10<x<60) parent alloy in the form of (ZnyNii-y)xAlioo-x or (ZnyPti-y)xAlioo-x and selectiv remove Al using the same dealloying protocol described above, to end up with nanopoi ZnyNii-yor ZnyPti-ywhere y (the ratio between Zn and Ni or between Zn and Pt) can b tuned to obtain a desired enhancement. This approach can be effective, and besides NiPt, other common H2 evolution catalysts can be used as well. In the foregoing, y can b( from 0.01 to 0.99, or from 0.1 to 0.9, or from 0.2 to 0.8, or from 0.3 to 0.7, or from 0.4 0.6, or even 0.5.

[0070] Third way: Direct deposition of Ni or Pt catalyst in nanoporous Zn powder during or after dealloying. Firstly, during dealloying: Another effective method introduce Ni or Pt catalyst in nanoporous Zn is to add Ni ions or Pt ions in the dealloyii solution using water-soluble salts of Ni or Pt. In this case, during dealloying, either (a) Ni or Pt ions are reduced and deposited onto the surface of the dealloyed nanoporous Z or (b) depending on the pH of the dealloying solution, Ni ions can deposit on the surfac of nanoporous Zn as Ni(0H)x, which is also catalytically active toward H2 evolution. Secondly, after dealloying: Ni or Pt catalyst can also be deposited on the surface of nanoporous Zn after dealloying by using a solution containing Ni ions or Pt ions obtain from water-soluble salts of Ni or Pt, in combination with a suitable reducing agent to reduce Ni ions or Pt ions and precipitate them onto the surface of nanoporous Zn. Besic Ni and Pt, other common H2 evolution catalysts can be used as well. This can be seen i FIGs. 15A-15D. In particular, trace A in FIG. 15D provides the hydrogen generation y obtained on nanoporous Zn loaded with Ni catalyst; the Ni catalyst was deposited usin^ the method described herein.

[0071] Method 2: Zinc activation using Ga, carbon powder, and a hydrogen evolution catalyst; one can activate Al using liquid Ga to make Al-Ga alloys.

[0072] Indeed, although the reaction of Al with water to produce H2 gas is spontaneous, in practice, the Al-water reaction will not proceed if Al is not activated. C way to activate Al is by making alloys of Al and liquid Ga, or alloys of Al and eutectic liquid Ga-In-Sn. The role of Ga or eutectic Ga-In-Sn is to expose a fresh Al surface to enable the reaction between Al and water, when liquid Ga or eutectic liquid Ga-In-Sn penetrates through the alloy via grain boundaries. Typically, we made alloys of Zn and liquid Ga, as well as alloys of Zn and eutectic liquid Ga-In-Sn for enhanced hydrogen generation. In order to enhance the rate of H2 generation in Zn-Ga alloys, one can add carbon powder to obtain finer Zn-Ga powder, and to add a H2 evolution catalyst.

[0073] An example protocol to activate Zn is as follows: One can make an all of Zn and Gallium (Ga) with a composition by mass of Znioo-xGaxwt.%, where x varief between 1 and 30 (l<x <30). This alloy can be made by various methods, includingmelting at high temperatures, mechanical milling, physical deposition methods, etc. Foi this disclosed technology, we use high-temperature melting to make our Znioo-xGaxallc by melting the corresponding stoichiometric mass of Zn and Ga, followed by rapid solidification. The rapidly solidified Znioo-xGaxalloy is brittle and can be ground or bal milled into fine powder. FIG. 7A (left panel) shows 200g of rapidly solidified Zmoo-xG; alloy ground into powder. Next, the ground Znioo-xGaxpowder is activated by mixing i1 with a small amount of carbon powder and a suitable H2 evolution catalyst, followed b grinding or ball -milling the mixture to obtain a very fine powder. As examples of H2 evolution catalysts, we used commercial Ni / C and Pt / C powder (Vulcan Pt / C with Pt-tc ratio between 1 :9 and 9: 1 in weight percentage).

[0074] One advantage of using Ni / C or Pt / C is the fact that it already contains carbon. Besides Ni / C or Pt / C, other common H2 evolution catalysts can be used as well Znioo-xGaxpowder and Pt / C (or Ni / C) powder are mixed and further ground and / or ball milled into ultra-fine powder as shown in FIG. 7A (right panel). Depending on the rate which H2 needs to be generated, the mass ratio between the Znioo-XGaxpowder and the Pt / C (or Ni / C) powder catalyst can be varied between 50: 1 (50g of Znioo-XGaxfor 1 gra of Pt / C to produce H2 at an extremely high rate) to 500: 1 (500g of Zmoo-XGaxfor 1 grai of Pt / C to produce H2 at high and practical rates). Fe can be activated in a similar way t replacing Zn with Fe in the above protocol.

[0075] Feature 3

[0076] As a third feature of the present disclosure, during “step 1” from featui above, the reaction between activated Zn (or activated Fe) and water produces green H: gas and ZnO as a solid by-product. Our third feature is a method to implement “step 2” from feature 1 to recycle / regenerate the ZnO solid by-product back to activated Zn. To demonstrate that ZnO can be recycled back to activated Zn, we first react this activated powder with water to produce H2 and ZnO powder, as shown in “step 1” in FIG. 1, thei dry the ZnO powder and use it to make a slurry or ink electrode. Using one of these materials (activated Zn powder, or ZnO powder from hydrolyzed activated Zn), we ma: slurry electrodes (FIG. 7B(a), 7B(b)) or ink electrodes (FIG. 7B(c)) following a slurry ( ink electrode fabrication protocol to make lithium-ion batteries slurry electrodes, and ir the fuel cell community to make ink electrode for membrane electrode assembly (MEA Besides using a slurry electrode and an ink electrode, a pellet electrode can also be macsimply by pressing the powder into pellets (FIG. 7B(d)). The advantage of using pellet electrodes is that the binder is not needed. During slurry or ink electrode preparation, o can mix the following three components:

[0077] - Activated Zn powder (or activated Zn powder in the form of ZnO)

[0078] - Conductive carbon additives, and

[0079] - Binder.

[0080] For the slurry binder (FIG. 7B(a), FIG. 7B(b)), we use the standard 40 mg / mL Polyvinylidene fluoride / N-Methyl-2-pyrrolidone (PVDF / NMP) commonly usei make lithium-ion battery slurry electrodes. For the ink binder (FIG. 7B(c)), we use Polytetrafluoroethylene (PTFE) or NAFION.

[0081] For the slurry, the typical mass ratio between these 3 components can 80: 10: 10, which means 80 wt.% of activated Zn powder (or ZnO powder), 10 wt.% of conductive carbon additives, and 10 wt.% of the binder. Other ratios can be used as wel depending on the desired loading of activated Zn in the slurry; for example, ratios of 75: 15: 10, 70:20: 10, 60:20:20, and 55:25:20. Next, the slurry (or ink) is cast onto a Cu or a glass plate and kept in the fume hood for drying. The drying process can be accelerated by heating the slurry at moderate temperatures and / or dying it in a vacuum oven. After drying, the slurry, which contains 80 wt.% active material, can easily be delaminated (peeled off) from the Cu foil or glass plate as shown in FIG. 7B(a) - 7B(T The typical mass loading of activated Zn in the slurry is 13 mg / cm2. Higher or lower m loading can be achieved by increasing or reducing the thickness of the slurry electrode and / or by varying the abovementioned ratio between the 3 components used in the slur

[0082] Next, to demonstrate that H2 can be produced from the free-standing activated Zn slurry electrode, and that the ZnO solid by-product can be recycled back t< activated Zn, we make an electrochemical cell with a piece of free-standing ZnO slurry electrode from FIG. 7B(a) as the working electrode (mass loading 13 mg / cm2), Pt foil t the counter electrode, mercury / mercury oxide (Hg / HgO) as the reference electrode, anc sodium hydroxide (NaOH) solution with various pHs as the electrolyte (note that becau Zn is susceptible to dissolve / corrode in electrolytes with very high pHs, for practical applications, suitable pHs can be used to prevent Zn dissolution). The activated Zn in tl working electrode slurry will spontaneously react with the electrolyte to produce H2 ga and ZnO solid by-product through step 1. Next, we electrochemically recycle ZnO badactivated Zn in the same cell setup. During the recycling of ZnO back to Zn, the follow reactions take place at the working and counter electrodes, respectively:

[0083] Working electrode:

[0084] Counter electrode:

[0085] Total reaction (Step 2): ZnO - Zn+ I / 2O2

[0086] To further demonstrate the concept, here we choose pH=14, but for practical applications, based on the Pourbaix diagram of Zn, the ideal pH should be between pH=7 and pH=12 to prevent Zn from dissolving / corroding in the electrolyte. 1 standard reduction potential for the reduction of ZnO to Zn at the working electrode (Zi + H2O + 2e’ - Zn + 2OH ) is -1.26 V vs. SHE at pH=14. For this proof-of-concept, we chose Hg / HgO as the reference electrode whose potential in pH=14 NaOH is 0.14 V vs SHE. Thus, the standard reduction potential for the reduction of ZnO to Zn at the worki electrode is -1.40 V vs. Hg / HgO. To investigate this reaction, we used a wider voltage window between -2 V and -1 V vs. Hg / HgO to account for reaction overpotentials and performed cyclic voltammetry (CV) experiments starting from open circuit voltage (O( around -1.4 V vs. Hg / HgO.

[0087] Four representative successive CVs are shown in FIG. 8, where it is se that during the negative sweep from OCV down to -2.0 V vs. Hg / HgO, a peak associatf with the reduction of ZnO to Zn is observed at around -1.6 V vs. Hg / HgO. During the positive sweep up to -1.0 V vs. Hg / HgO, a peak associated with the oxidation of Zn to ZnO is observed at around -1.2V vs. Hg / HgO. Thus, ZnO is reduced to Zn below the equilibrium potential, and Zn is oxidized to ZnO above the equilibrium potential. Note that in a real application, one will only need to go below the equilibrium potential to reduce ZnO to Zn (step 2 from Feature 1), then oxidize Zn by reacting with water to produce H2 and ZnO (step 1 from Feature 1).

[0088] During each CV test, there is an obvious peak current at around -1.6 V Hg / HgO associated with the reduction of ZnO to Zn. It should be mentioned that during ZnO reduction to Zn, a fraction of the reduction current comes from the reduction of H to H2, whose theoretical potential is -0.97 V vs. Hg / HgO. When one goes below -0.971vs. Hg / HgO, the reduction of H2O to H2 also contributes to the overall reduction curren and will dominate as the reaction overpotential increases (i.e., more negative potential) Thus, under the current specific condition, the ideal voltage to reduce ZnO to Zn shouhbetween OCV and -1.8V vs Hg / HgO. That voltage window will slightly change depenc on the pH of the electrolyte and on the reaction rate (reaction current density or scan rai

[0089] As further details, when we start with ZnO in the working electrode slurry, no H2 bubbles are observed before the reduction of ZnO to Zn. However, after tl reduction of ZnO to Zn, a lot of H2 bubbles are generated on the slurry electrode, even mins after the reduction of ZnO to Zn. These H2 bubbles come from the reaction of the freshly recycled activated Zn with the electrolyte to produce H2 and ZnO through Step from Feature 1. Then we reduced the ZnO slurry electrode again at various times (e.g., 30, 15, and 5 minutes) by applying the same potential as before and dried it immediatel in the antechamber of the glovebox under vacuum.

[0090] We characterized our slurry electrodes by X-ray diffraction (XRD) as shown in FIG. 9 (top). The blue XRD pattern in FIG. 9 (top) is collected from the slurr electrode of hydrolyzed Zn. (i.e., activated Zn reacted with water to produce H2 and Zn The blue XRD pattern corresponds to ZnO as expected. Once the slurry is reduced, Zn( converted back to Zn as confirmed by the black XRD in FIG. 9 (top). Therefore, these results not only prove the reduction of ZnO back to Zn, but also demonstrate that the slurry electrode has a certain cyclability. In addition, a very important finding is the fac that ZnO can be reduced back to Zn in a short time down to 5 minutes as shown by the data compiled in FIG. 10.

[0091] Feature 4

[0092] As a fourth feature, the disclosed two-step water-splitting approach ca: be used to make a portable and rechargeable hydrogen powerpack for various applicatii including using it to power heavy-lift drones and low-speed electric vehicles. A simplif schema of our rechargeable hydrogen powerpack is shown in FIG. 11. Our rechargeab hydrogen powerpack works as follows: during the discharge step (step 1), zinc electrod react with water to produce green H2 on-demand / on-board. Generated H2 is fed into a hydrogen fuel cell to generate electricity. Hence this discharge step is like the discharge a battery to generate electricity. Because a fuel cell generates electricity and water from the reaction between H2 and O2, the (waste)water from the fuel cell can be collected ani reused to produce more H2 from the reaction between the activated Zn electrode and w; (see FIG. 11). During the charge step (step 2) clean electrical power can be used to redi ZnO back to Zn. This charge step can be achieved in a few minutes (for example, as fa:as 5 minutes for a full charge). This fast-charging property ensures the fuel cell can provide continuous power for mobile applications, such as vehicles and drones.

[0093] The amount of electrical energy that can be generated by our portable rechargeable hydrogen powerpack can be tuned simply using a suitable amount of activated Zn electrode (to produce the desired amount of H2 during the discharge step 1 coupled with a suitable amount of oxygen evolution catalyst at the counter electrode (tc enable the reduction of ZnO back to Zn during the charging step 2). Additionally, an appropriate fuel cell with the right power should be used for electrical energy generatio For the sake of illustration, Table 3 shows a typical composition of a portable and rechargeable hydrogen powerpack that can be used to generate approximately 20 kWh electricity from 1 kg of hydrogen produced on-board. The total mass of all the components, including the mass of the fuel cell, is approximately 49 kg.

[0094] As detailed in non-limiting Table 3, the corresponding specific energy density of this portable power station can be estimated to be in the range of 411-453 Wh kg'1for Zn (and over 500 Wh kg'1for Fe), which is 2-3 times higher than the enen density of practical lithium-ion and lithium-polymer batteries. This 20-kWh energy car used to power heavy -lift drones and low-speed electric vehicles.

[0095] For example, most low-speed electric vehicles use 6 lead-acid batterie (which have a total battery weight above 60 kg), and only yield a driving range of 25 tc miles per full charge. By replacing lead-acid batteries with our rechargeable and portab hydrogen power station, one can achieve a driving range beyond 200 miles in these lov speed electric vehicles, which is approximately 1 order of magnitude higher than the driving range achieved using lead-acid batteries. Furthermore, this portable power generator can be recharged in 5-15 minutes, as demonstrated earlier above.

[0096] One can also assemble a bigger rechargeable and portable hydrogen powerpack which can generate enough energy to power regular electric vehicles and heavy-duty vehicles like buses. For the sake of illustration, since the powerpack from Table 3 can deliver 20 kWh from 1 kg of hydrogen produced on-board, staking 6 powerpacks from Table 3 will give an energy of 120 kWh, which is enough to power regular electric vehicles, and recharge in about 5-15 minutes (compared to about 60 minutes or more for electric vehicles powered by lithium-ion batteries).

[0097] Feature 5

[0098] As a fifth feature, while the rechargeable and portable hydrogen powerpack described in Feature 4 (see FIG. 11) is used to produce electricity, it can als be used to produce green H2. In that case, a fuel cell is not required in the setup in FIG. In the case of green H2 generation, the H2 produced during step 1 is compressed and stc for various applications, including for H2 refueling stations. Once all the activated Zn electrode is converted into ZnO during H2 generation, activated Zn can be regenerated reducing the ZnO electrode back to Zn using clean electrical energy from sunlight (PV panels), wind turbines, hydropower, etc.

[0099] Small-scale demonstrations (see FIGs. 12 and 13): The powerpack we designed includes a fuel cell (inside of the blue box in FIG. 12), a fuel reaction chambe (the black box in FIG. 12), a gas-liquid separator (the empty bottle in FIG. 12), 3 angstroms molecular sieves tank (the bottle between drone landing gear in FIG. 12), silicone tubes and gas valves. It starts when NaOH solution is injected into the reaction chamber, which contains activated metal fuels, such as Znioo-xGaxalloy with catalyst P1The hydrogen gas produced here is “wet”. Thus, a gas-liquid separator is used here to separate the hydrogen gas from NaOH solution and ensure no liquid flows to the next stage. In the following filtration, 3 angstroms molecular sieves further remove minority water molecules from wet hydrogen gas. Then, the dried hydrogen gas flows into the fr cell for power generation. FIG. 13 shows the drone fixed connecting with the powerpac The generated electrical power from the fuel cell, around 16 - 18.5 kV, is enough and tl only driving force to power the drone. On / off switch of such power supply is controllec the contact of water and activated metal (Zn). In addition, a self-air-cool system can be contained in the fuel cell to ensure the continuous working of the fuel cell at room temperature.

[0100] Aspects

[0101] The following Aspects are illustrative only and do not limit the scope the present disclosure or the appended claims. Any part or parts of any one or more Aspects can be combined with any part or parts of any one or more other Aspects.

[0102] Aspect 1. A method of producing hydrogen, comprising: contacting water and at least one of activated Zn or activated Fe under conditions sufficient to giv< rise to molecular hydrogen and the corresponding oxide of the at least one of the activa Zn and activated Fe.

[0103] Aspect 2. The method of Aspect 1, wherein the activated Zn compris at least one of (1) an admixture of nanoporous Zn and a hydrogen evolution catalyst, ar (2) a ZnGa alloy, carbon powder and a hydrogen evolution catalyst.

[0104] Aspect 3. The method of Aspect 1, wherein the activated Fe compris at least one of (1) an admixture of nanoporous Fe and a hydrogen evolution catalyst, an (2) a FeGa alloy, carbon powder and a hydrogen evolution catalyst.

[0105] Aspect 4. The method of any one of Aspects 1-3, further comprising effecting power generation from a fuel cell with the molecular hydrogen.

[0106] Aspect 5. The method of any one of Aspects 1-4, further comprising reforming the corresponding oxide of the at least one of the activated Zn and activated to the at least one of the activated Zn and activated Fe, the reforming optionally being effected by applying a current to the corresponding oxide, the current being evolved fire power generated from a fuel cell with the molecular hydrogen.

[0107] Aspect 6. A method of reforming an activated metal, comprising: at least one of (1) forming an admixture of a hydrogen evolution catalyst and at least one nanoporous Zn and Fe so as to give rise to an activated one of the at least one of nanoporous Zn and Fe; and (2) contacting at least one of a ZnGa alloy and a FeGa allo with carbon powder and a hydrogen evolution catalyst so as to give rise to an activated least one Zn and Fe.

[0108] Aspect 7. The method of Aspect 6, comprising forming an admixtun a hydrogen evolution catalyst and nanoporous Zn to give rise to an activated Zn.

[0109] Aspect 8. The method of Aspect 6, comprising forming an admixtun a hydrogen evolution catalyst and nanoporous Fe to give rise to an activated Fe.

[0110] Aspect 9. The method of Aspect 6, contacting ZnGa alloy with carbc powder and a hydrogen evolution catalyst so as to give rise to an activated Zn.

[0111] Aspect 10. The method of Aspect 6, contacting FeGa alloy with carb powder and a hydrogen evolution catalyst so as to give rise to an activated Fe.

[0112] Aspect 11. A method of reforming an activated material, comprising

[0113] applying a voltage or current to an oxide of Zn or Fe under condition sufficient to give rise to molecular oxygen and the corresponding metal of the Ze or Fe.

[0114] Aspect 12. The method of Aspect 11, wherein the oxide is Fe oxide.

[0115] Aspect 13. The method of Aspect 11, wherein the oxide is Zn oxide.

[0116] Aspect 14. The method of Aspect 11, wherein a hydrogen evolution catalyst accompanies the oxide of Zn or Fe.

[0117] Aspect 15. The method of Aspect 11, wherein a hydrogen evolution catalyst accompanies the corresponding metal of the Zn or Fe oxide.

[0118] Aspect 16. A method of generating power, comprising: contacting w and at least one of activated Zn and activated Fe under conditions sufficient to give rise molecular hydrogen and an oxide of the at least one of the activated Zn and activated F and effecting power generation from a fuel cell using the molecular hydrogen.

[0119] Aspect 17. The method of Aspect 16, further comprising using at lea some of the power evolved from the fuel cell to reform at least some of the oxide of the least one of the activated Zn and activated Fe to the at least one of the activated Zn and activated Fe.

[0120] Aspect 18. A method of producing hydrogen, comprising: contacting water and at least one of activated Zn and activated Fe under conditions sufficient to gi rise to molecular hydrogen and the oxide of the at least one of the activated Zn and activated Fe; and at least one of storing the molecular hydrogen and using the molecula hydrogen to effect power generation from a fuel cell.

[0121] Aspect 19. A system, comprising: a fuel cell; a supply of water; and amount of at least one of activated Zn or activated Fe, the system configured to contact water and the amount of at least one of activated Zn or activated Fe so as to evolve molecular hydrogen, the system further configured to communicate the molecular hydrogen to the fuel cell so as to evolve a current from the fuel cell.

[0122] Aspect 20. The system of Aspect 19, wherein the system is comprise in a vehicle.

[0123] Aspect 21. The system of Aspect 19, wherein the system is comprise in a backup generator.

[0124] Aspect 22. A power module, comprising: a fuel cell configured to evolve a current from hydrogen; a reaction stage, the reaction stage comprising a first electrode that comprises at least one of activated Zn and activated Fe, the reaction stag< comprising a counter electrode that comprises an oxygen evolution catalyst, the reactio stage configured to (1) contact the first electrode and water so as to evolve molecular hydrogen and the corresponding oxide of the least one of activated Zn and activated Fe and (2) communicate a current across the corresponding oxide of the least one of activa Zn and activated Fe so as to reform the metal of the corresponding oxide of the least on of activated Zn and activated Fe and give rise to molecular oxygen, the power module configured to communicate molecular hydrogen to the fuel cell.

[0125] Aspect 23. The power module of Aspect 22, the power module bein^ arranged to communicate current evolved from the fuel cell to the reaction stage.

[0126] Aspect 24. The power module of Aspect 23, wherein the current is communicated across the corresponding oxide of the least one of activated Zn and activated Fe so as to give rise to molecule oxygen and reform the metal of the corresponding oxide.

[0127] Aspect 25. The power module of any one of Aspects 22-24, wherein power module is comprised in a vehicle.

[0128] Aspect 26. A method of forming nanoporous Zn or Fe, the method comprising: contacting an amount of particulate Zn alloy or Fe alloy with an alkaline solution, the contacting being performed under conditions sufficient to give rise to nanoporous Zn or Fe.

[0129] Aspect 27. The method of Aspect 26, wherein the alkaline solution comprises NaOH.

[0130] Aspect 28. The method of Aspect 26, wherein the particulate Zn or I comprises particulates having a cross-sectional dimension of from about 5 to about 200 micrometers.

[0131] Aspect 29. The method of Aspect 26, wherein the particulate Zn allo comprises ZnAl.

[0132] Aspect 30. The method of Aspect 26, wherein the particulate Fe allo comprises FeAl.

[0133] Aspect 31. A water splitting reactor, comprising: a first electrode for hydrogen evolution that comprises at least one of activated Zn and activated Fe with a hydrogen evolution catalyst; a counter electrode for oxygen evolution that comprises ai oxygen evolution catalyst, the reactor configured to (1) contact the first electrode and water so as to spontaneously evolve molecular hydrogen and the corresponding oxide c the least one of activated Zn and activated Fe, and (2) communicate a current across the corresponding oxide of the least one of activated Zn and activated Fe so as to reform th metal of the corresponding oxide of the least one of activated Zn and activated Fe and rise to molecular oxygen, the water splitting reactor optionally being configured for tw< step operation.

Claims

What is Claimed:

1. A method of producing hydrogen, comprising: contacting water and at least one of activated Zn or activated Fe under conditioi sufficient to give rise to molecular hydrogen and the corresponding oxide of the least one of the activated Zn and activated Fe.

2. The method of claim 1, wherein the activated Zn comprises at least one of (1) ai admixture of nanoporous Zn and a hydrogen evolution catalyst, and (2) a ZnGa alloy, carbon powder and a hydrogen evolution catalyst.

3. The method of claim 1, wherein the activated Fe comprises at least one of (1) ai admixture of nanoporous Fe and a hydrogen evolution catalyst, and (2) a FeGa alloy, carbon powder and a hydrogen evolution catalyst.

4. The method of any one of claims 1-3, further comprising effecting power generation from a fuel cell with the molecular hydrogen.

5. The method of any one of claims 1-3, further comprising reforming the corresponding oxide of the at least one of the activated Zn and activated Fe to tl at least one of the activated Zn and activated Fe, the reforming optionally being effected by applying a current to the corresponding oxide, the current being evolved from power generated from a fuel cell with the molecular hydrogen.

6. A method of reforming an activated metal, comprising: at least one of (1) forming an admixture of a hydrogen evolution catalyst and at least one of nanoporous Zn and Fe so as to give rise to an activated one of the a least one of nanoporous Zn and Fe; and (2) contacting at least one of a ZnGa all and a FeGa alloy with carbon powder and a hydrogen evolution catalyst so as tc give rise to an activated at least one Zn and Fe.

7. The method of claim 6, comprising forming an admixture of a hydrogen evoluti catalyst and nanoporous Zn to give rise to an activated Zn.

8. The method of claim 6, comprising forming an admixture of a hydrogen evoluti catalyst and nanoporous Fe to give rise to an activated Fe.

9. The method of claim 6, contacting ZnGa alloy with carbon powder and a hydro: evolution catalyst so as to give rise to an activated Zn.

10. The method of claim 6, contacting FeGa alloy with carbon powder and a hydros evolution catalyst so as to give rise to an activated Fe.

11. A method of reforming an activated material, comprising: applying a voltage or current to an oxide of activated Zn or activated Fe under conditions sufficient to give rise to molecular oxygen and the corresponding me of the Ze or Fe.

12. The method of claim 11, wherein the oxide is Fe oxide.

13. The method of claim 11, wherein the oxide is Zn oxide.

14. The method of claim 11, wherein a hydrogen evolution catalyst accompanies th oxide of Zn or Fe.

15. The method of claim 11, wherein a hydrogen evolution catalyst accompanies th corresponding metal of the Zn or Fe oxide.

16. A method of generating power, comprising: contacting water and at least one of activated Zn and activated Fe under conditn sufficient to give rise to molecular hydrogen and an oxide of the at least one of activated Zn and activated Fe; effecting power generation from a fuel cell using the molecular hydrogen.

17. The method of claim 16, further comprising using at least some of the power evolved from the fuel cell to reform at least some of the oxide of the at least on< the activated Zn and activated Fe to the at least one of the activated Zn and activated Fe.

18. A method of producing hydrogen, comprising: contacting water and at least one of activated Zn and activated Fe under conditn sufficient to give rise to molecular hydrogen and the oxide of the at least one of activated Zn and activated Fe; and at least one of storing the molecular hydrogen and using the molecular hydrogel effect power generation from a fuel cell.

19. A system, comprising: a fuel cell; a supply of water; and an amount of at least one of activated Zn or activated Fe, the system configured to contact the water and the amount of at least one of activated Zn or activated Fe so as to evolve molecular hydrogen, the system further configured to communicate the molecular hydrogen to the fu< cell so as to evolve a current from the fuel cell.

20. The system of claim 19, wherein the system is comprised in a vehicle.

21. The system of claim 19, wherein the system is comprised in a backup generator22. A power module, comprising: a fuel cell configured to evolve a current from hydrogen; a reaction stage, the reaction stage comprising a first electrode that comprises at least one of activated Zn and activated Fe, the reaction stage comprising a counter electrode that comprises an oxygen evolution catalyst,the reaction stage configured to (1) contact the first electrode and water so as to evolve molecular hydrogen and the corresponding oxide of the least one of activated Zn and activated Fe, and (2) communicate a current across the corresponding oxide of the least one of activated Zn and activated Fe so as to reform the metal of the corresponding oxide of the least one of activated Zn and activated Fe and give rise to molecular oxygen, the power module configured to communicate the molecular hydrogen to the fu cell.

23. The power module of claim 22, the power module being arranged to communic current evolved from the fuel cell to the reaction stage.

24. The power module of claim 23, wherein the current is communicated across the corresponding oxide of the least one of activated Zn and activated Fe so as to gi rise to molecule oxygen and reform the metal of the corresponding oxide.

25. The power module of any one of claims 22-24, wherein the power module is comprised in a vehicle.

26. A method of forming nanoporous Zn or Fe, the method comprising: contacting amount of particulate Zn alloy or Fe alloy with an alkaline solution, the contact! being performed under conditions sufficient to give rise to nanoporous Zn or Fe27. The method of claim 26, wherein the alkaline solution comprises NaOH.

28. The method of claim 26, wherein the particulate Zn or Fe comprises particulate! having a cross-sectional dimension of from about 5 to about 200 micrometers.

29. The method of claim 26, wherein the particulate Zn alloy comprises ZnAl.

30. The method of claim 26, wherein the particulate Fe alloy comprises FeAl.

31. A water splitting reactor, comprising: a first electrode for hydrogen evolution that comprises at least one of activated 1 and activated Fe with a hydrogen evolution catalyst;a counter electrode for oxygen evolution that comprises an oxygen evolution catalyst, the reactor configured to (1) contact the first electrode and water so as to spontaneously evolve molecular hydrogen and the corresponding oxide of the least one of activated Zn and activated Fe, and (2) communicate a current across the corresponding oxide of the least one of activated Zn and activated Fe so as to reform the metal of the corresponding oxide of the least one of activated Zn and activated Fe and give rise to molecular oxygen, the water splitting reactor optionally being configured for two-step operation.

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