Electrochemical hydrogen pumping coupled with catalytic membrane reactor and its applications

Abstract

Disclosed is a method of dehydrogenation of hydrogen-containing compounds in a reactor comprising a catalytic chamber, an electrochemical chamber, and an H-conductive membrane, comprising dehydrogenating the hydrogen-containing compound to produce hydrogen atom equivalents and oxidizing the hydrogen atom equivalents on the anodic H-conductive membrane. The reaction between the protons and a molten electrolyte in the electrochemical chamber generates water, which is decomposed on a counter electrode producing hydrogen. The hydrogen can be used in hydrogenation reactions. Also disclosed is a method of reducing a substrate, for example, a substrate dissolved or dispersed in the molten electrolyte.

Description

[0001]MTV-21725 ELECTROCHEMICAL HYDROGEN PUMPING COUPLED WITH CATALYTIC MEMBRANE REACTOR AND ITS APPLICATIONS RELATED APPLICATIONS This application claims the benefit of priority to U.S. Provisional Patent Application No.: 63 / 651,522, filed May 24, 2024. GOVERNMENT SUPPORT This invention was made with government support under CHE-2102669 and CHE- 2400167 awarded by the National Science Foundation. The government has certain rights in the invention. BACKGROUND The exchange of hydrogen equivalents between chemical species plays a key role in fuel processing, commodity and fine chemical synthesis, as well as hydrogen production and storage. The removal of hydrogen equivalents from molecules is often thermodynamically unfavorable and / or kinetically sluggish, leading to low equilibrium conversion, high temperatures of operations, catalyst deactivation, and unselective reactivity. Hydrogen equivalents can be removed from molecules electrochemically. However, current electrochemical dehydrogenation methods suffer from catalyst deactivation, electrode corrosion, sluggish kinetics, and / or limited mass transport. Likewise, there are limited methods for efficiently delivering the removed hydrogen equivalents to drive other chemical transformations. Accordingly, better methods of electrochemically driving the exchange of hydrogen equivalents between chemical species are needed. SUMMARY OF THE INVENTION In some embodiments, the present disclosure relates to a method of hydrogen production, comprising: (a) providing a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane, wherein: the membrane is located between the catalytic chamber and the electrochemical chamber; FoleyHoagUS12882195.4 MTV-21725 the catalytic chamber comprises a catalyst layer; and the electrochemical chamber comprises a counter electrode and a molten electrolyte; (b) introducing a gaseous mixture comprising a hydrogen-containing compound to the catalytic chamber; (c) contacting the hydrogen-containing compound with the catalyst layer, thereby producing hydrogen atom equivalents (HAEs)and a dehydrogenated compound; (d) transferring the HAEs across the membrane; (e) applying an electrical potential difference between the membrane and the counter electrode, thereby oxidizing the HAEs to generate protons; (f) contacting the protons with the molten electrolyte, thereby generating protonated electrolyte anions; and (g) contacting the protonated electrolyte anions with the counter electrode, thereby reducing the protonated electrolyte anions and generating recovered hydrogen. In some embodiments, the present disclosure relates to a method of reducing a substrate, comprising: (a) providing a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane, wherein: the membrane is located between the catalytic chamber and the electrochemical chamber; the catalytic chamber optionally comprises a catalyst layer; and the electrochemical chamber comprises a counter electrode and a molten electrolyte; (b) providing the substrate in the electrochemical chamber; (c) introducing to the catalytic chamber a gaseous mixture comprising hydrogen or a hydrogen- containing compound; (d) if the gaseous mixture comprises a hydrogen-containing compound, contacting the hydrogen- containing compound with the catalyst layer, thereby producing HAEs and a dehydrogenated compound; (e) if the gaseous mixture comprises hydrogen, contacting the hydrogen with the catalyst layer or the H-conductive membrane, thereby producing HAEs; (f) transferring the HAEs across the membrane; FoleyHoagUS12882195.4 MTV-21725 (g) applying an electrical potential difference between the membrane and the counter electrode, thereby oxidizing the HAEs to generate protons and placing the protons in contact with the molten electrolyte, thereby generating protonated electrolyte anions; and (h) contacting the counter electrode with the substrate and the protonated electrolyte anions, thereby generating a reduced substrate. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a photograph of an electrochemical cell containing molten electrolytes. The Swagelok® parts, including union cross and union tee, introduced gas into the system via two customized jackets. A single-bore alumina tube is sandwiched between two customized jackets with the H-conducting membrane at the bottom, which serves as the working electrode. Counter and reference electrodes are introduced to the system via a two-bore alumina tube. FIG. 2 shows a schematic of the electrochemical cell containing an H-conducting palladium membrane (palladium foil + palladium black) as the H-oxidizing anode. Palladium black has high surface area and can dissociate hydrogen species from the gas flow and transport hydrogen atoms through the membrane. The palladium foil also serves as the working electrode (WE) to electrochemically oxidize the hydrogen atoms to protons on the palladium surface in contact with the molten hydroxide (Na / KOH) electrolyte. Pt and Ni wire serve as the reference and counter electrode (RE, CE), respectively. Pure hydrogen is introduced to the electrolyte side so that Pt RE can serve as a reversible hydrogen electrode (RHE). The three-electrode system is controlled by a potentiostat. FIG.3 shows a polarization curve obtained upon supply of pure argon gas on the Pd black side of the palladium membrane. The scan rate of the potential is 50 mV / s. FIG.4 shows polarization curves obtained upon supply of 100% H2or 5 vol.% H2 / Ar with different flow rates or 100% H2on the Pd black side of the palladium membrane. The scan rate of the potential was 20 mV / s. The Ohmic drop was compensated with 90% iR correction. The geometric surface area of the Pd foil exposed to the molten electrolyte was ~0.5 cm2. FIG. 5 shows a schematic illustration of the electrochemical cell for ammonia or ethane dehydrogenation. A catalyst layer is integrated below the palladium membrane. FoleyHoagUS12882195.4 MTV-21725 FIG. 6 shows the polarization curves upon supply of 1 sccm NH3on the Pd black side of the palladium membrane. The catalyst layer was Ru+Cs supported on porous graphite felt. The scan rate of the potential was 20 mV / s. The Ohmic drop was compensated with 90% iR correction. The geometric surface area of the Pd foil exposed to the molten electrolyte was ~0.5 cm2. FIG. 7 shows the correlation between hydrogen flow rate and current at palladium anode. The hydrogen flow rate from the electrochemical compartment was determined by gas chromatography using pure argon as the sweep gas. FIG. 8 shows the conversion efficiency of ammonia with Ru+Cs catalyst under different working conditions. The conversion efficiency of NH3was calculated with residual H2in the ammonia exhaust determined by gas chromatography and anodic current assuming 100% Faradaic efficiency. FIG. 9 shows the polarization curves upon supply of 1 sccm C2H6on the Pd black side of the palladium membrane. The catalyst layer was Pt supported on carbon black. The scan rate of the potential was 20 mV / s. The geometric surface area of the Pd foil exposed to the molten electrolyte was ~0.5 cm2. FIG. 10 shows the flow rate of H2and C2H4in the ethane exhaust stream at open-circuit potential or 0.45 vs. RHE. The flow rates were determined by gas chromatography. FIG.11 shows a schematic illustration of the electrochemical cell for steel production with an H-oxidizing anode. The molten electrolyte melt consists of MgCl2, KCl and NaCl with a eutectic point of 385 °C. Protons generated at the palladium anode interact with dispersed Fe2O3powder to form Fe3+, which is further reduced at the Fe counter electrode. A catalyst layer for dehydrogenation reactions is integrated below the palladium membrane to provide a hydrogen source. FIG.12. is a schematic illustration comparing intermediate temperature electrochemically driven Pd membrane dehydrogenation with a molten hydroxide (this work) with passive pressure- driven Pd-membrane dehydrogenation and low-temperature electrochemically driven Pd- membrane hydrogenation with aqueous electrolytes. FoleyHoagUS12882195.4 MTV-21725 FIG. 13 is a schematic depiction of a cell configuration designed for electrochemical hydrogen pumping in Pd-membrane-based electrochemical hydrogen separation using an H2-Ar mixture. FIG. 14 is a plot of open-circuit potential (OCP) vs. H2partial pressure with temperatures changing from 200 to 400 °C in Pd-membrane based electrochemical hydrogen separation using an H2-Ar mixture. The total flow rate of the H2 (balance Ar) stream with varied H2 partial pressure gas was maintained at 10 sccm. FIG. 15 shows linear sweep voltammograms (5 mV s−1scan rate) with different hydrogen partial pressures on the thermochemical side at 300 °C. The total flow rate of the H2-Ar gas with varied H2partial pressure gas was maintained at 80 sccm. FIG.16 shows linear sweep voltammograms (5 mV s−1scan rate) with Pd foils (25 μm and 100 μm) and 25 μm Pd-Ag (75 wt.%: 25 wt.%) foil. The measurement was conducted with 40 sccm 0.05 atm H2at 300 °C. FIG.17 shows a comparison of H2flux across the membrane as a function of the difference in the square roots of the hydrogen partial pressures between the two sides of the membrane, with a feed of 40 sccm 0.05 atm H2(circles) or 80 sccm 0.01 atm H2(squares) at 300 °C. The electrochemical-driven hydrogen permeation is compared with pressure-driven hydrogen permeation assisted with an Ar sweep gas (10 – 80 sccm) and vacuum (<1 mbar, hollow symbols). FIG. 18 shows a comparison of H2permeation rate under various conditions, with a feed of 0.05 atm H2(balance Ar) at 300 °C. “without E-chem input” refers to hydrogen permeation measured without the presence of molten electrolyte or under OCP conditions if molten electrolyte is present. “e” denotes the electrochemical configuration in the presence of the molten electrolyte. The hydrogen permeation was measured with a retentate stream of 40 sccm 0.05 atm H2with a permeate / cathode stream of 10 sccm Ar or H2, as denoted in brackets. The dashed box indicates the maximum hydrogen permeation rate that can be achieved with Ar sweep gas or vacuum. The hydrogen permeation under pumping conditions was calculated from the limiting current in the polarization curve. Error bars indicate the standard deviation from at least three independent experiments. FoleyHoagUS12882195.4 MTV-21725 FIG. 19 shows a schematic of a cell configuration designed for ammonia decomposition promoted by electrochemically driven hydrogen separation. FIG. 20 shows linear sweep voltammograms (5 mV s−1scan rate) of Pd and Pd-Ag membrane in ammonia decompositions promoted by electrochemically driven hydrogen separation at 200 and 250 °C with the H2production rate on the right axis. The thickness of the Ru+Cs / CNT catalyst layer is 3.5 mm. FIG.21 is a plot showing H2production rate under OCP and hydrogen pumping conditions as a function of NH3flow rate at 250 °C. The hydrogen pumping was performed by chronoamperometry in limiting current region. Error bars indicate the standard deviation from at least three independent experiments. FIG.22 is a plot showing hydrogen production rate disclosed herein (catalyst thickness of 1.5 mm) compared with prior work on thermochemical ammonia decomposition without hydrogen removal. The activity comparison is based on a Ru-mass normalized basis. FIG.23 is a plot showing ammonia conversion vs. H2separation factor as disclosed herein (catalyst thickness of 3.5 mm) in comparison to prior studies of ammonia cracking coupled to H2separation. The H2separation factor (bottom axis) is defined as the ratio of pumped H2to residual H2. Note that the lines and open symbols do not convey H₂ separation factor information but are included solely for comparative analysis of ammonia conversion. FIG.24 is a plot showing hydrogen production rate as a function of catalyst layer thickness at 250 °C during ammonia decomposition. Error bars indicate the standard deviation from at least three independent experiments. FIG. 25 is a plot showing hydrogen partial pressure in the catalyst layer under OCP and active hydrogen pumping conditions for catalyst thickness of 1.5 mm and 5.5 mm. FIG. 26 is a schematic showing how the hydrogen partial pressures in the catalyst layer and at the membrane|gas interface is determined under active hydrogen pumping conditions. The hydrogen partial pressure at the membrane|gas interface (pi) is determined from the Richardson’s FoleyHoagUS12882195.4 MTV-21725 equation using the hydrogen permeability (PH2) and diffusion-limited hydrogen flux in the limiting current regime (jlim) while its counterpart in the catalyst layer (pc) is measured by GC. FIG.27 is a plot showing hydrogen partial pressure difference (pc−pi) between the catalyst layer and at the membrane|gas interface under active hydrogen pumping condition as a function of catalyst layer thickness. FIG. 28 is a schematic representation of a cell configuration designed for methylcyclohexane dehydrogenation promoted by electrochemically driven hydrogen separation. FIG.29 is a plot showing linear sweep voltammograms (5 mV s−1scan rate) of Pd and Pd- Ag membrane at 200 and 250°C in methylcyclohexane dehydrogenation promoted by electrochemically driven hydrogen separation with the H2production rate on the right axis. The thickness of the Pt / C catalyst layer is 1.5 mm. FIG.30 is a plot showing H2production rate under OCP and hydrogen pumping conditions as a function of methylcyclohexane flow rate at 250 °C in methylcyclohexane dehydrogenation promoted by electrochemically driven hydrogen separation. The hydrogen pumping was performed by chronoamperometry in limiting current region. Error bars indicate the standard deviation from at least three independent experiments. FIG. 31 is a plot showing methylcyclohexane conversion as a function of reaction temperature under OCP and hydrogen pumping conditions. The gray dashed line represents the thermodynamic conversion limit of methylcyclohexane to toluene without hydrogen extraction. FIG. 32 is a plot showing methylcyclohexane conversion vs. H2separation factor / separation yield as disclosed herein in comparison to prior work on methylcyclohexane dehydrogenation coupled to H2separation. The H2separation factor is defined as the ratio of pumped H2to residual H2. Note that the lines and open symbols do not convey H₂ separation factor information but are included solely for comparative analysis of methylcyclohexane conversion. FIG. 33 is a plot showing the effect of temperature on the polarization curves of Pd membrane at 300 °C. The linear sweep voltammograms (5 mV s−1scan rate) were obtained upon supply of 80 sccm 0.05 atm H2to the thermochemical side. FoleyHoagUS12882195.4 MTV-21725 FIG.34 is a plot showing the effect of flow rate on the polarization curves of Pd membrane at 300 °C. The linear sweep voltammograms (5 mV s−1scan rate) were obtained varied flow rates of 0.05 atm H2supplied to the thermochemical side. FIG. 35 is a plot showing limiting current density normalized to the square root of the effective hydrogen partial pressure versus the flow rate. Effective H2partial pressures were estimated by subtracting the permeated hydrogen from the 0.05 atm feed H2 stream. The normalized limiting current density plateaus at flow rates above 40 sccm, indicating the absence of mass transport limitations at the Pd|gas interface. FIG. 36 is a plot showing the effect of Pd surface roughness on the polarization curves of Pd membrane at 300 °C. The linear sweep voltammograms (5 mV s−1scan rate) were obtained upon supply of 40 sccm 0.05 atm H2to the thermochemical side. The surface area of the roughened Pd foil (membrane|electrolyte interface) is about 50 times higher than that of the smooth Pd (membrane|electrolyte interface). FIG. 37 is a plot showing H2production rate at the cathode measured by GC vs. H2formation rate computed from the current passed. The measurement was conducted with a series of constant applied current with 40 sccm 0.05 atm H2in the thermochemical compartment and 10 sccm Ar in the electrochemical compartment. FIG. 38 is a plot showing durability testing of a Pd membrane cell at 300 °C. Chronopotentiometry at 300 mA cm−2was conducted with 40 sccm 0.05 atm H2supplied to the thermochemical compartment and 10 sccm H2to the electrochemical compartment. A 60 mV increase in potential was observed over 25 hours which recovered to the initial value following voltammetric cycling. FIG. 39 is the Arrhenius plot of electrochemically driven hydrogen permeability of a Pd membrane. The data were collected when a Pd foil was polarized to the limiting current region, ~500 mV vs. RHE. The feed to the thermochemical side was 80 sccm 0.05 atm H2. And final H2partial pressure at the membrane|gas interface was taken from the residual H2gas measured in the output stream of the thermochemical side by GC. Independent permeability data points based on pressure driven method from previous work (Davis, W. D., “Diffusion of gases through metals. I. FoleyHoagUS12882195.4 MTV-21725 Diffusion of hydrogen through palladium,” Knolls Atomic Laboratory (1954)) are shown for comparison. FIG. 40 is the Arrhenius plot of electrochemically driven hydrogen permeability of a Pd- Ag membrane. The feed to the thermochemical side is 80 sccm 0.05 atm H2. And the actual partial pressure at the membrane|gas interface was determined from the downstream gas by GC. Independent permeability data points based on pressure driven method from previous work (Serra, E. et al., “Hydrogen and deuterium in Pd-25 Pct Ag alloy: Permeation, diffusion, solubilization, and surface reaction,” Metall. Mater. Trans. A Phys. Metall. Mater. Sci.1998, 29, 1023) are shown for comparison. FIG. 41 is a plot showing a comparison of H2production rate of Pd and Pd-Ag foil under electrochemical hydrogen pumping conditions. The feed to the thermochemical side is 40 or 80 sccm 0.05 H2at 300 °C. FIG. 42 is a plot showing catalyst dependence of the polarization curves of a Pd-Ag foil with 10 sccm NH3at 250 °C. The current is negligible in the absence of catalyst and weak in the presence of Ru / CNTs. FIG.43 is a plot showing H2production rate of Pd and Pd-Ag membranes under OCP and hydrogen pumping conditions as a function of NH3flow rate at 250 °C. The hydrogen pumping was performed by chronoamperometry in the limiting current region. Error bars indicate the standard deviation from at least three independent experiments. FIG. 44 is a plot showing NH3conversion of Pd and Pd-Ag membranes under OCP and hydrogen pumping conditions as a function of NH3flow rate at 250 °C. The dashed line indicates the thermodynamic conversion limit of NH3at 250 °C without hydrogen extraction. Error bars indicate the standard deviation from at least three independent experiments. FIG. 45 is a plot showing reaction order in H2for ammonia decomposition at 250 °C. The measurement was conducted with a H impermeable membrane (25 μm nickel foil) without the presence of a molten electrolyte. Data collected by varying H2partial pressure with 4 sccm NH3, 0.5 sccm N2and balanced by Ar to a total flow rate of 10 sccm. The ammonia decomposition rate FoleyHoagUS12882195.4 MTV-21725 was determined by quantifying the amount of generated H2using in line GC. The conversion of NH3was maintained below 3% in all cases. FIG. 46 is a plot showing a comparison of hydrogen partial pressure at the membrane|gas interface (estimated from OCP) and average across the catalyst layer (measured by in line GC). The comparison was performed with a Pd foil with a catalyst thickness of 1.5 mm or 5.5 mm at 250 °C. The flow rate of introduced NH3 was 2 sccm. FIG.47 is a plot showing a comparison of polarization curves for electrochemically driven Pd membrane dehydrogenation of methylcyclohexane with and without the Pt / C catalyst layer at 250 °C. The current is negligible in the absence of the Pt / C catalyst. The feed is 10.41 μL min−1methylcyclohexane and 2 sccm Ar (molar ratio 1:1). FIG.48 is a plot showing toluene selectivity and H2 / toluene ratio under different hydrogen extraction conditions at 250 °C. The feed is 2.6 μL min−1methylcyclohexane and 0.5 sccm Ar (molar ratio 1:1). Toluene selectivity is defined as the ratio of produced toluene to consumed methylcyclohexane. Error bars indicate the standard deviation from at least three independent experiments. FIG.49 is a plot showing the effect of methylcyclohexane flow rate on methylcyclohexane conversion at 250 °C. The molar ratio of methylcyclohexane and Ar was maintained at 1:1. The dashed line indicates the thermodynamic conversion limit of methylcyclohexane to toluene at 250 °C without hydrogen extraction. Error bars indicate the standard deviation from at least three independent experiments. FIG.50 is a plot showing conversion of ethane as a function of temperature. The black line with square markers shows the conversion attained under open-circuit potential, which closely approaches the calculated equilibrium conversion shown by the grey curve with empty triangular markers. The red line with circular makers shows the conversion under polarization of the cell close to the limiting current, leading to a 3.5-fold improvement in conversion compared to OCP conditions at 550 °C and far exceeding the nominal equilibrium conversion at that temperature. FoleyHoagUS12882195.4 MTV-21725 DETAILED DESCRIPTION OF THE INVENTION Dehydrogenation is a chemical process involving the removal of molecular hydrogen. It plays a key role in fuel processing, commodity, fine chemical synthesis and even hydrogen storage. For example, one of the largest scale dehydrogenation reactions is the dehydrogenation of ethylbenzene to styrene, a precursor for the synthesis of rubbers and plastics. However, the dehydrogenation process usually requires the use of catalysts at high temperatures since dehydrogenation of many species is highly endothermic. Moreover, the dehydrogenation catalysts can be kinetically inhibited by the presence of H2as the generated hydrogen competes for catalytic sites with the substrate. For instance, the dehydrogenation of propane is reported to have a negative reaction order respective to hydrogen. Thus, it is desirable to in situ remove the generated hydrogen from the catalytic system to promote the dehydrogenation reaction. In some embodiments, the dehydrogenation reactions are kinetically and thermodynamically promoted by coupling thermochemical catalysis of dehydrogenation to electrochemical oxidation of hydrogen equivalents to electrons and protons. The electrochemical driving force is used to drive an otherwise thermodynamically unfavorable and kinetically sluggish dehydrogenation reaction. Given that most thermochemical catalysis of dehydrogenation occurs in the temperature range of 150 to 600 °C, this coupling requires an electrolyte that remains stable and ionic conductive in this temperature range. The most viable electrolytes are based on molten salts, which are dissociated into mobile ions with high ionic conductivity. However, one challenge encountered with these media is the limited solubility for gaseous reactants or hydrogen. The maximum current obtainable in these electrolytes is limited by mass transport. Another challenge is that catalytic sites exposed to electrolytes are prone to deactivation via mechanisms such as poisoning, restructuring, and dissolution. In some embodiments, this impasse is overcome by separating thermochemical dehydrogenation from electrochemical oxidation by an H-conducting membrane. An H- conducting membrane is impermeable to molten electrolytes but allows for H2dissociation into H-atoms and efficient H-atom conduction, enabling the coupling of thermochemical dehydrogenation to electrochemical hydrogen oxidation. In some embodiments, such a design also serves the additional purpose of efficiently supplying reducing equivalents to a molten salt electrochemical cell to conduct reductive FoleyHoagUS12882195.4 MTV-21725 transformations, either via dehydrogenation reaction or the direct introduction of H2. Many anodic reactions in molten salts rely on the generation of O2or a sacrificial anode (e.g., graphite) to supply electrons for the reductive transformation at the cathode. However, the biggest challenge is the irreversible corrosion of the anode materials, especially under such oxidative and corrosive conditions at elevated temperatures. Even with the most corrosion-resistant metals, like platinum and gold, anode corrosion is still the major factor that leads to degradation and reduced efficiency of the process. Thus, supplying reducing equivalents to an anode that can perform electrochemical hydrogen oxidation can significantly reduce the polarization below the redox potential of the anode material and thus eliminate anode corrosion. Moreover, the relatively facile reaction kinetics of electrochemical hydrogen oxidation compared to the production of O2can serve to improve reaction efficiency by reducing or eliminating parasitic overpotential losses. Hydrogen is a promising clean energy vector for decarbonizing heavy industry and transportation, but its transport is challenging. Hydrogen carriers like ammonia and hydrocarbons are lead candidates for long-distance large-scale H2transport, mandating efficient low-carbon methods for driving endothermic H2regeneration and separation from these carriers at point of use. A hydrogen partial pressure differential across a hydrogen selective membrane can be used to drive endothermic dehydrogenation processes, but this approach often results in moderate hydrogen separation and requires downstream pressurization. In some embodiments, the present disclosure addresses those challenges by employing a hydrogen-selective Pd-based membrane as the anode of a molten electrolyte electrochemical cell along with a hydrogen evolving platinum or nickel cathode. This construct enables electrochemically driven H2separation at the temperatures required for thermochemical dehydrogenation catalysis. In some embodiments, low applied anode potentials of < 0.3 V are sufficient to drive diffusion-limited H-transport across the Pd membrane with a 4-fold enhancement in hydrogen separation rate at 300 °C relative to conventional pressure- driven separation with concomitant hydrogen concentration from 0.05 to 1.0 atm. Interfacing the anode with a dehydrogenation catalyst enables electrochemically promoted ammonia cracking and methylcyclohexane dehydrogenation. Electrochemical H2separation enhances the rate of both reactions at low temperatures (200-250 °C), drives conversion beyond thermodynamic limits to 91% and 94%, respectively, and generates a concentrated, high purity stream of H2. Pd membrane-based hydrogen separations operate via H2dissociation, transport of interstitial hydrogen atoms and H-H recombination. This has been conventionally used to FoleyHoagUS12882195.4 MTV-21725 selectively remove hydrogen from dehydrogenation reaction systems with the benefits of hydrogen purification and overcoming equilibrium limitations. However, this strategy relies on a hydrogen partial pressure differential across the membrane—usually assisted with the use of sweep gas or vacuum, leading to limited hydrogen permeation and the need for additional downstream pressurization. Additionally, H-permeable Pd membranes have also been interfaced with conventional aqueous electrolytes at room temperature and used as cathodes to generate reactive H species for hydrogenation catalysis. In some embodiments, the Pd membrane can be employed as an anode for dehydrogenation catalysis by inverting the polarity in this construct. If the interstitial H atoms in Pd membrane could be converted to electrons and protons, then electrochemical input could be used to drive H-permeation and promote dehydrogenation catalysis. Hydrogenation reactions are typically exothermic and kinetically facile at room temperature, while the analogous dehydrogenation processes are typically thermodynamically uphill and kinetically sluggish, requiring high operating temperatures (>200 °C) far exceeding the boiling point of water. In some embodiments, electrochemically driven dehydrogenation can be achieved if Pd membranes is interfaced with stable proton-conducting electrolyte at the requisite temperatures of dehydrogenation catalysis (200-500 °C). In some embodiments, interfacing a H-permeable membrane (e.g., Pd or Pd alloy) with a proton-conducting molten electrolyte and a suitable dehydrogenation catalyst would enable electrochemically driven dehydrogenation and separation of H2from candidate hydrogen carriers such as ammonia and methylcyclohexane. In such a configuration, the membrane acts as both a H-conductor and hydrogen oxidation anode, converting permeated H species to electrons and protons in the presence of a positive bias (FIG. 12). Since linear changes in the electrochemical potential lead to logarithmic changes in H-activity at the Pd / electrolyte interface, this approach would furnish driving forces for hydrogen permeation far in excess of that achievably with conventional pressure-driven H2separation. The produced electron and protons generated at the Pd-membrane anode recombine at a platinum or nickel cathode to regenerate hydrogen. Since molten electrolytes display low H2solubilities, they effectively block passive back diffusion of H2, enhancing separation efficiency. This construct allows for the generation of concentrated, high purity H2from dense hydrogen carriers driven by renewable electricity. FoleyHoagUS12882195.4 MTV-21725 Electrochemical polarization drives hydrogen permeation To examine the viability of electrochemical hydrogen separation at intermediate temperatures, the model hydroxide Pd-membrane electrochemical cell as shown schematically in FIG. 13 was constructed. The setup consisted of a thermochemical compartment and an electrochemical compartment separated by a Pd H-conductive membrane. For initial studies, a dehydrogenation catalysis was omitted, and the thermochemical compartment was exposed to an H2-Ar gas with varying hydrogen partial pressure. The electrochemical compartment consisted of a 51:49 mol% Na:K eutectic molten hydroxide electrolyte along with a Pt reference, and Pt wire or Ni mesh counter electrode. Unless otherwise stated, 1 atm of hydrogen was continually flowed over the molten hydroxide electrolyte to limit the requirements for post-separation or concentration for permeated hydrogen (see FIG. 1 and Examples for full details of cell design). Thus, the Pt reference electrode served as a reversible hydrogen electrode (RHE) and all potentials are reported relative to this value. The relationship between the open-circuit potential (OCP) of the Pd membrane electrode and the hydrogen partial pressure was first examined across a range of temperatures (FIG. 14). Upon a change of H2partial pressure in the thermochemical compartment from 0.01 atm to 0.025atm (corresponding to 1% and 2.5% H2 (Ar balance)), a change of−23.7 mV in OCPfrom 115.4mV to 91.7 mV at 300 °C was observed. The overall trend was linear with a slope of −57.7 mV dec−1. This is in line with the value (−56.9 mV dec−1) calculated from the Nernst equation (EOCP= −RT / 2F*ln(PH2)) at 300 °C. The same linear trend also held at 200 °C and 400 °C with slope of −45.7 mV dec−1and −67.5 mV dec−1, also in line with the Nernst equation at those temperatures. The foregoing observation indicates that the Pd working electrode was able to carry out reversible proton-coupled electron transfer (Volmer step) to interconvert Pd-H and electron / proton equivalents in the molten hydroxide electrolyte with an Pd-H activity set by the H2pressure on the thermochemical side. Importantly, since the gas stream on the cathode-facing electrochemical side is always held at 1 atm H2, the foregoing observations indicate that net oxidation of dissolved H2negligibly influences the observed potential, likely due to limited H2transport in the molten electrolyte—arising from its inherently low H2solubility—and / or sluggish H2dissociative adsorption at the Pd membrane|electrolyte interface. These data further evince that the OCP of Pd membrane serves as a real-time readout of Pd-H activity at the Pd|electrolyte interface which is equilibrated with the activity of H2 on thermochemical side in the absence of current flow. FoleyHoagUS12882195.4 MTV-21725 To examine if the permeated hydrogen species can be oxidized on the Pd membrane, linear sweep voltammograms (LSVs, 5 mV s−1) of the Pd-H oxidation reaction was monitored as a function of H2partial pressure at 300 °C and treated as quasi-steady state polarization curves (FIG. 15). The temperature dependence of the polarization curves can be found in FIG. 33. At a hydrogen partial pressure of 0.01 atm, sweeping the applied potential positive of the OCP resulted in a rapid rise in current density from 0 to 115 mA cm−2over a modest increase in potential from 116 to 300 mV. The current then plateaued to a potential-independent limiting value of 120 mA / cm2, diagnostic of transport-limited Pd-H oxidation. As the H2partial pressure on the thermochemical side was increased to 0.025 atm and 0.05 atm, the corresponding limiting current densities increased to 225 mA cm−2and 355 mA cm−2, respectively. The strong sensitivity of the limiting current to H2partial pressure indicates that H transport through the Pd membrane, rather than transport limitations in the electrolyte, sets the limiting current density. Flow rate dependence experiments further support that mass transport limitations are negligible in the thermochemical compartment when the flow rate exceeds 40^sccm (see FIG.34 and FIG.35). Across all conditions examined, an overpotential of less than 200 mV was required to reach a limiting current plateau, indicating that the Pd-H oxidation reaction is highly efficient at the Pd|molten hydroxide interface. This overpotential can be further lowered by roughening the Pd surface to increase the active sites available for catalyzed Pd-H oxidation (see FIG.36). As the hydrogen partial pressure was further increased to 0.4 atm and 1.0 atm, the polarization curve showed an exponential rise of current density with no detectable plateau up to 500 mA cm−2. Under these conditions, current densities of 500 mA cm−2were readily achieved at overpotentials of less than 110 mV. These data indicate that at high H2pressures, H transport to the Pd|electrolyte interface no longer limits the reaction in this potential range, and the kinetics are dominated by the reverse Volmer reaction for oxidizing Pd-H at the electrolyte interface. Overall, these studies establish that this system is capable of rapid H permeation and Pd-H oxidation, resulting in net H2oxidation catalysis at high current densities and low overpotentials. Though the above data evince the oxidation of permeated hydrogen at the Pd anode, the amount of equivalent hydrogen regenerated at the counter electrode is unknown from the above polarization data. Thus, the Faradaic efficiency of hydrogen regeneration was examined under different current densities using an Ar sweep gas (FIG. 37). In all cases, it was found that the increase in H2 flow rate in the cathode stream quantified by in-line gas chromatography (GC) FoleyHoagUS12882195.4 MTV-21725 analysis matched that calculated from the hydrogen oxidation current, corresponding to a 100% Faradaic efficiency for net electrochemical H2pumping across the cell. This finding evinces the absence of detectable parasitic reactions at either the anode or cathode and highlights the lack of detectable back diffusion of H2across the cell. Thus, these above findings support the proposed mechanism of action in the system, as shown in FIG. 13. In the thermochemical compartment, hydrogen molecules dissociate into hydrogen atoms on the Pd black surface and transport through the Pd membrane to the Pd|electrolyte interface. These hydrogen atoms undergo oxidation on the Pd membrane, forming protons under the applied positive bias. The generated protons then react spontaneously with hydroxide ions to generate water, which is reduced at the counter electrode to generate hydrogen and regenerate hydroxide ions. The durability of this process was evaluated over 25 hours of continuous operation at a constant current density of 300 mA cm−2, showing no substantial change in the measured potential (see FIG. 38). The Faradaic efficiency also remained at 100% at the end of experiment (Table 1). The factors that determine the rate of Pd-H oxidation at the membrane anode at 300 °C with a dilute 0.05 atm H2feed stream were examined (FIG. 16). As the thickness of the Pd membrane increases from 25 μm to 100 μm, it was observed that the transport-limited current density decreased from 292 mA cm−2to 111 mA cm−2. This finding further supports the notion that H transport across the Pd membrane limits the rate of Pd-H oxidation in the limiting current regime. Indeed, at Pd-Ag (25 wt.%Ag) alloy membrane, which is known to display higher H- permeability, gave rise to a 40% higher limiting current than pure Pd foil. The above effects on limiting current density are quantitatively in line with the Richardson’s equation, which states that hydrogen flux across the membrane is inversely proportional to membrane thickness and directly proportional to the difference in the square roots of hydrogen partial pressures across the membrane, scaled by the permeability. To quantify the effect of the electrochemical driving force on hydrogen flux across the membrane, the electrochemical systems (with an applied potential in the limiting current regime) were compared to a passive Pd membrane lacking an electrochemical interface, assisted with an inert gas sweep or vacuum (FIG.17). For the passive Pd membrane, Ar was employed as a sweep gas on the permeate side, paired with a 40 sccm 0.05 atm H2stream (circles) contacting the retentate side. At a sweep rate of 10 sccm, the H2flux reached 3.7 mmol s−1m−2which further increased to 5.5 mmol s−1m−2at 40 sccm. Further increase in flow rate from 40 sccm to 80 sccm, FoleyHoagUS12882195.4 MTV-21725 however, leads to a plateau of the H2flux (5.67 mmol s−1m−2) across the membrane. This limiting flux is also observed with applied vacuum (< 1 mbar) to the permeate side. These data points of the passive Pd membrane deviated significantly from what would be expected from the Richardson’s equation (dashed line), which only holds under the assumption that H2dissociation and H-H recombination the Pd surfaces is fast relative to H diffusion through the membrane. Consequently, the observation deviation suggests that hydrogen permeation is limited by sluggish H-H recombination on the permeate side under H-lean conditions. In contrast, the H2flux exceeds 16 mmol s−1m−2with electrochemical-driven hydrogen permeation, ~3 fold higher than the maximum H2flux that can be achieved with the passive Pd membrane. Moreover, this difference further increases to ~6 fold when an 80 sccm 0.01 atm H2stream is introduced to the retentate side (squares). Therefore, these observations highlight the value of fast electrochemical H oxidation over sluggish H-H recombination in promoting hydrogen permeation under H-lean conditions. The H2permeation rate under various operating conditions was further compared, with a feed of 0.05 atm H2at 300 °C (FIG. 18). For these studies, H2was employed as a sweep gas on the electrochemical / permeate side, paired with a 0.05 atm H2stream contacting the thermochemical / retentate side. In the absence of the electrochemical cell (passive Pd membrane), a negative H2 formation rate (−3.8 sccm) was observed due to the back diffusion of H2 from the permeate side (1 atm H2) to the retentate side (0.05 atm H2). In contrast, in the presence of a molten electrolyte and the absence of any current flow (OCP conditions), this passive diffusion was completely eliminated with no detectable crossover of H2in either direction irrespective of the relative ratios of H2on either side. This is likely because the presence of molten hydroxide suppresses hydrogen crossover due to its inherently low hydrogen solubility and / or by hindering H2dissociation or H-H recombination at the membrane|electrolyte interface, which is consistent with the observation in the OCP studies conducted in FIG. 14. These findings highlight the importance of such suppression of H2back transport for maximizing the efficiency of electrochemically driven hydrogen permeation. Compared to a passive Pd membrane tested with 10 sccm Ar, active electrochemical hydrogen pumping not only enabled a 4-fold enhancement from 0.269 sccm to 1.10 sccm in hydrogen separation but also enabled in-situ concentration (1 atm. H2vs. 0.05 atm. H2) compared to traditional pressure-driven permeation methods. Common hydrogen permeation rates were observed irrespective of whether Ar or H2was employed as the sweep gas in the electrochemical chamber, further evincing the lack of passive H2 crossover and FoleyHoagUS12882195.4 MTV-21725 establishing that the H2permeation is purely given by the current density passed. The hydrogen permeation can be further enhanced with Pd-Ag foil and this enhancement is more significant if the flow rate of the input H2stream increases (see FIG. 41). Taken together, the foregoing data evince that this membrane is capable to extracting hydrogen from dilute streams, offering the opportunity to drive and promote dehydrogenation reactions that are inhibited by the buildup of hydrogen – as detailed below. Electrochemically-driven hydrogen permeation promotes ammonia decomposition Electrochemical hydrogen pumping can be employed to drive thermocatalytic dehydrogenation reactions. First, ammonia decomposition was examined since ammonia is considered to be an ideal hydrogen carrier candidate. In conventional thermal ammonia cracking, hydrogen is known to inhibit reaction kinetics on Ru- or Ni-based catalysts, impeding high conversion at moderate temperatures even in the absence of thermodynamically limitations. Additionally, conventional ammonia decomposition produces a mixture of H2, N2, and residual NH3that requires expensive downstream separations and recycle loops. Pd membrane-based dehydrogenation could, in principle, address both of these challenges by (a) kinetically promoting the reaction by removing inhibiting H2and (b) selectively separating the H2from the reaction medium as it is generated. To test these hypotheses, a carbon nanotube-supported and Cs-promoted Ru catalyst (Ru-Cs / CNTs) was employed in this study because it is known to catalyze ammonia decomposition at low temperatures (< 400 °C). The Ru-Cs / CNTs catalyst bed was integrated into the thermochemical compartment as shown in FIG. 19. The catalyst layer was positioned below the Pd membrane to minimize the path length over which H2must travel to the Pd membrane. The generated hydrogen permeated through the membrane under electrochemical driving force and evolved at the counter electrode. The unreacted ammonia was trapped by 2.0 M sulfuric acid and the amount of residual hydrogen exiting the reactor on the thermochemical side was quantified by in-line GC. The ammonia conversion was calculated based on the permeated hydrogen (computed from the current passed) and the residual hydrogen detected in the thermochemical compartment outlet. Steady-state polarization curves of Pd-H oxidation were used to examine the effect of applied polarizations and temperature on ammonia decomposition (FIG.20). Control experiments established that the HOR current was negligible if the catalyst layer was absent, thus Pd black did not contribute to ammonia decomposition under these conditions (FIG.42). As the potential of Pd FoleyHoagUS12882195.4 MTV-21725 membrane was increased, the current density rose until a limiting current density of 60 mA cm−2, corresponding to a H2production rate of 0.21 sccm at 200 °C. The limiting current density further increased to 275 mA cm−2at 250 °C, ascribed to enhanced ammonia decomposition kinetics and hydrogen diffusivity at elevated temperatures. The limiting current density can be further enhanced with a Pd-Ag membrane to 450 mA cm−2ascribed to higher hydrogen permeability. To determine if the electrochemical hydrogen pumping promotes the reaction kinetics of ammonia decomposition, the hydrogen production rates under OCP versus those under Pd-H oxidation at the limiting current density were examined as a function of ammonia flow rate at 250 °C (FIG. 21 and FIG.43). For measurements under polarization, the hydrogen separation yield is defined as the fraction of the total produced hydrogen that is separated from the thermochemical side. The overall hydrogen production rates (the aggregate of permeated H2and residual H2) were found to be substantially higher when electrochemical hydrogen pumping was conducted, irrespective of the membrane type or flow rate. Specifically, at an ammonia flow rate of 0.5 sccm a nearly >500% enhancement in hydrogen production rate from 0.116 to 0.585 sccm for the Pd membrane and to 0.626 sccm for the Pd-Ag membrane was observed. This same enhanced hydrogen formation rate was only achievable in the absence of electrochemical pumping at 20- fold higher flow rate corresponding to only ~5% conversion (see FIG.44). This rate enhancement led to an ammonia conversion of 78.1% and 83.3% for Pd and Pd-Ag membrane, respectively (see FIG. 44). Moreover, a separation yield of over 99% was observed, indicating that the majority of the H2produced can be extracted as purified and concentrated hydrogen. Upon increasing the flow rate to 2 sccm and then to 10 sccm (FIG.21), a progressive reduction in the promotion of the total hydrogen production rate upon pumping to 230% and 75% for Pd was observed, respectively. Higher promotion levels of 350% and 120% were observed for Pd-Ag membrane. These trends arise because the higher flow rate leads to lower single pass conversion of the ammonia and thus the kinetic enhancement afforded by H2extraction is less pronounced than at lower flow rates. Additionally, at higher flow rates, the produced H2has a lower residence time in the diffusion layer near the membrane surface, reducing the H2separation yield. Both of these trends can be minimized with a more optimized pathway for gas delivery to the thermochemical side. Second, the higher flow rate leads to lower single pass conversion of the ammonia and thus the kinetic enhanced afforded by H2extraction is less pronounced than at lower flow rates. Both of above trends are mitigated with a higher H permeability membrane, leading to higher observed total H2 FoleyHoagUS12882195.4 MTV-21725 production rates with Pd-Ag vs Pd across all flow rates. The same effects would also be expected to accrue from thinner membranes as well. These studies highlight that in a practical device, the flow rate should be matched to the catalyst bed volume and membrane area so as to achieve the maximal total conversion and H2separation yield. In all of the above studies, the ammonia conversion remained well below the equilibrium conversion limit of 89.4% and the approach-to- equilibrium (based on the residual H2pressure) is less than 6.2×10−3under OCP and 8.8×10−4with hydrogen pumping (Table 2), suggesting that the observed promotion effects are largely kinetic in origin. This inference is in line with the negative reaction order in hydrogen (−0.44) during ammonia decomposition, as determined far from reaction equilibrium in FIG.45. The build-up of hydrogen serves to block active sites for ammonia binding and activation, and thus the reaction kinetics are promoted by in-situ hydrogen removal. To further demonstrate the effectiveness of hydrogen pumping in promoting ammonia decomposition compared to conventional thermal-cracking experiments, hydrogen production rates, which are equivalent to ammonia decomposition rates, on a Ru-mass normalized basis were calculated, as shown in FIG. 22 and Table 3. The hydrogen pumping serves to enhance the performance of the Ru-Cs / CNTs catalysts with hydrogen production rate up to 71.2 mmol gRu−1min−1at 250 °C and 19.6 gRu−1min−1at 200 °C (see stars). The rates of ammonia cracking far exceeded all the state-of-the-art Ru-based catalysts when they are compared under similar weight hourly space velocity (WHSV) conditions and temperatures (3–20 gRu−1min−1at 250 °C, 3–6 gRu−1min−1at 200 °C, see Table 3). Even the most active catalysts reported in literature, Ru-K / MgO and Ru / MgO(111), still require a substantially higher temperature >300 °C to achieve a comparable hydrogen production rate. This comparison highlights the effectiveness of Pd membrane-based hydrogen pumping in enabling high hydrogen production rates at lower temperatures. There are a few studies that employ membrane-based strategies for ammonia decomposition and in situ hydrogen separation, including passive Pd-based membranes, silica membrane and electrochemical protonic conductors. The findings of the present disclosure compare favorably with those prior reports as shown FIG. 23 and Table 4 based on ammonia conversion and H2separation factor / yield. The Pd-Ag membrane hydrogen pumping device delivered a substantial hydrogen separation factor (>100) or yield (>99.0%), along with an ammonia conversion up to 83.7% over the temperature range of 200-250 °C. The ammonia FoleyHoagUS12882195.4 MTV-21725 conversion further increased to 91.6% with an aggregate hydrogen separation factor of >1000 at 250 °C when two identical electrochemical setups were connected in series—effectively simulating a larger electrode area flow path length. Such high ammonia conversion is above the equilibrium conversion limit (89.4% at 250 °C), which has not been achieved in prior studies at these low temperatures. These performance characteristics mainly accrue from the highly active Ru-Cs / CNTs catalyst and high hydrogen separation yield provided by the electrochemical driving force. In contrast, other membrane technologies require much higher temperatures (>350 °C) and assistance with a sweep gas or vacuum to achieve similar levels of conversion (Table 4)— approach which affords more modest rate enhancements and H2separation factors than the presently disclosed electrochemical hydrogen pumping method. Moreover, the pressure differential created by the vacuum may also introduce mechanical stresses that can compromise membrane durability in traditional pressure-driven membrane technologies. In contrast, the presently disclosed method maintains pressure balance and realizes in-situ hydrogen concentration using hydrogen as a sweep gas, resulting in hydrogen partial pressures that are substantially higher than other membrane technologies (Table 4). While solid protonic conductors based on BaCeO3or BaZrO3have been used to promote ammonia decomposition and have been implemented as part of direct ammonia fuel cell, they typically require high temperatures of >500 °C to achieve appreciable current density due to the inherently sluggish solid-state proton mobility. In contrast, the molten hydroxide electrolyte disclosed herein offers much higher ion mobility and concentration, enabling high ionic conductivity and lower temperature operation at high current densities. Though CsH2PO4based superprotonic conductors offer a promising low-temperature route for ammonia decomposition due to their low resistance, the system requires co-feeding of steam along with the ammonia and are therefore susceptible to performance degradation due to H2O-induced poisoning. The presently disclosed molten electrolyte is separated from the ammonia cracking catalyst layer with a dense hydrogen permeable membrane, obviating the need to humidify the feed stream and eliminating crossover of the catalyst constituents to the electrolyte or vise-versa. While high-temperature proton exchange membrane based on ion-pair designs have shown promises in extracting hydrogen from low-concentration sources, they are unable to maintain stable operation above 200 °C and are typical incompatible with the presence of ammonia. Overall, this electrochemical H2separation FoleyHoagUS12882195.4 MTV-21725 serves to kinetically promote ammonia dehydrogenation catalysis while simultaneously generating a concentrated H2stream from a pure-ammonia feed. Coupled H2transport gradients impact the efficiency of catalysis and separation To understand how the transport characteristics of the Ru-Cs / CNTs catalyst layer and membrane impact the reaction kinetics and conversion during electrochemical hydrogen pumping, the change in hydrogen production rate at 250 °C was examined by varying the thickness of the catalyst layer for both Pd and Pd-Ag (FIG.24). As the catalyst layer thickness was increased from 1.5 mm to 5.5 mm, the total hydrogen production rate of Pd membrane rose from 0.77 sccm to 1.19 sccm, consistent with great catalyst loading in the thermochemical compartment. However, the enhancement in hydrogen production under hydrogen pumping relative to OCP declined from 266% to 217% as the catalyst layer thickness was increased from 1.5 mm to 5.5 mm. This diminishment arose because the H flux through the Pd membrane is proportional to the square root of hydrogen partial pressure at the membrane|gas interface, but the H2production rate scales linearly with catalyst loading. Thus, the H2separation flux lagged behind the increase in H2production rate, leading to diminished rate promotion. For this same reason, a reduction of hydrogen separation yield from 95.1% to 92.8% was observed when the catalyst thickness was increased from 1.5 mm to 5.5 mm. All of these trends hold for Pd-Ag membranes, but with higher levels of catalyst promotion and higher separation yield due to the enhanced H permeability in the alloy, as detailed below. The observation in FIG. 24 can be rationalized by quantifying the hydrogen partial pressure in the catalyst layer, which is taken to approximately equal the residual H2measured by GC in the retentate stream. Given the low Péclet number of 0.01-0.05 under OCP conditions, H2transport in the catalyst layer is diffusion-dominated, resulting in a nearly constant hydrogen partial pressure throughout the catalyst layer. This finding was further supported by the close agreement between the hydrogen partial pressures estimated from the measured OCP and those measured by GC (FIG.46). However, with active electrochemical oxidation of Pd-H, the effective hydrogen partial pressure at the membrane|electrolyte interface dropped to nearly zero (since the current reaches a potential-independent plateau). Due to active hydrogen extraction, a new non- equilibrium steady-state was achieved with a reduction in the hydrogen partial pressure in the catalyst layer compared to the OCP conditions (FIG. 25). With a catalyst thickness of 1.5 mm, there was a substantial reduction of the average hydrogen partial pressure in the catalyst layer from FoleyHoagUS12882195.4 MTV-21725 0.107 atm to 0.024 atm for Pd and 0.014 atm for Pd-Ag due to active hydrogen extraction. When the catalyst thickness was increased from 1.5 mm to 5.5 mm, the overall hydrogen partial pressure in the catalyst layer rose under OCP conditions owing to a higher catalyst loading. Yet, hydrogen extraction also reduced the hydrogen partial pressure in the catalyst layer from 0.165 atm to 0.052 atm for Pd and 0.036 atm for Pd-Ag, the increase in hydrogen partial pressure when extending the catalyst thickness from 1.5 mm to 5.5 mm was more pronounced for Pd-Ag (2.6-fold) than Pd (2.2-fold). This suggests that the catalyst layer is contributing to the transport resistance, given the exceptionally high permeability of the Pd-Ag membrane. To further understand if mass transport limitations in the catalyst layer contribute to the above observations, the hydrogen partial pressure difference between the catalyst layer and the membrane|gas interface was quantified under active hydrogen pumping (FIG. 26 and FIG. 27). As displayed in FIG. 26, the hydrogen partial pressure in the catalyst layer (pcat) is taken to equal the residual H2measured by GC. Unlike for most membrane separation systems, the present disclosure provides direct insight into the H2partial pressure at the Pd membrane|gas interface, allowing diagnosis of an H2gradient within the catalyst layer. Since the electrochemical limiting current density (jlim) is correlated with the H2partial pressure at the Pd membrane|gas interface (pint) by the Richardson’s equation (see FIG. 26), the value of the limiting current can be used to back-calculate pint. For Pd membranes, across all catalyst thicknesses, this hydrogen partial pressure difference (pcat− pint) remains near zero (FIG. 27), indicating the rate of H2removal at the membrane|gas interface is insufficiently fast to induce a mass transport gradient in the catalyst layer. In contrast, when a Pd-Ag membrane was employed, a substantial pressure difference was observed, suggesting that the average H2pressure in the catalyst layer is higher than the hydrogen partial pressure at the membrane|gas interface (FIG. 27). While this pressure differential is small, ∆p = 0.003 atm, for the 1.5 mm catalyst layer, it grew to ∆p = 0.017 atm for the 5.5 mm catalyst film. This indicates a substantial hydrogen gradient was present in the catalyst layer for the Pd-Ag membrane system and implies that H2gas transport through the catalyst layer was comparable to the rate of H transport through the Pd-Ag membrane itself. This implies that due to the high permeability Pd-Ag membrane, hydrogen transport in the catalyst layer cannot fully replenish the H2pumped through the membrane, leading to mixed transport control between the membrane and the catalyst layer. In the limit of a thin enough Pd-Ag membrane, it is expected that the membrane itself would present negligible transport resistance, the ideal scenario, and the transport gradient FoleyHoagUS12882195.4 MTV-21725 would exist predominantly in the catalyst layer. In this limit, H2transport through the porous catalyst layer should be optimized to maximize catalytic rate promotion and hydrogen separation yield. These finding highlight that fast electrochemical H oxidation allows one to approach the behavior of an ideal membrane that imposes no limitation on H-transport. Electrochemically driven hydrogen permeation promotes methylcyclohexane dehydrogenation Analogous to the ammonia / N2cycle, the methylcyclohexane / toluene cycle offers a viable route to store and transport hydrogen, enabled by the liquid-phase nature of both compounds. While the technology for toluene hydrogenation is commercially available, the development of portable methylcyclohexane dehydrogenation technologies for point-of-use applications remains more poorly developed and is a key bottleneck for the deployment of methylcyclohexane-toluene cycles. The endothermicity of methylcyclohexane dehydrogenation requires high temperatures (>300 °C) to drive high conversion; however, high temperatures can also degrade catalytic activity and promote deleterious side reactions, such as demethylation and coking. In some embodiments, electrochemical hydrogen permeation was employed to drive methylcyclohexane dehydrogenation to high conversion at low temperatures. Pt / C was chosen as the catalyst because platinum displays high activity for C-H activation relative to C-C scission, representing the most active metal for alkane dehydrogenation. Similar to the setup employed above for ammonia decomposition, a Pt / C catalyst bed was integrated into the thermochemical compartment as shown in FIG. 28. Liquid methylcyclohexane was first vaporized at 160 °C and then introduced with Ar as the carrier gas with a molar ratio maintained at 1:1. The catalyst bed positioned immediately adjacent to the membrane facilitated dehydrogenation of the introduced methylcyclohexane into toluene and hydrogen. The hydrogen permeated through the membrane under an electrochemical driving force and the residual species, including H2and methylcyclohexane and generated toluene, were analyzed by inline GC. Similar to ammonia decomposition, slow scan linear sweep voltammetry of Pd-H oxidation was used to examine the effect of applied polarization and temperature on methylcyclohexane dehydrogenation (FIG.29). Negligible HOR current was observed if the catalyst layer was absent, indicating that the Pd black surface does not substantially contribute to methylcyclohexane dehydrogenation (See FIG. 47). As the potential of Pd membrane was increased, the current density rose until a limiting current density of 162 mA cm−2, corresponding to a H2 production rate FoleyHoagUS12882195.4 MTV-21725 of 0.56 sccm at 200 °C. The limiting current density further increased to 275 mA cm−2at 250 °C, ascribed to enhanced catalytic activity and hydrogen diffusivity at elevated temperatures. Both limiting current densities at 200 °C and 250 °C rose with Pd-Ag membrane to 210 and 610 mA cm−2, respectively, owing to its higher hydrogen permeability. To examine if electrochemical hydrogen pumping promotes the reaction kinetics of methylcyclohexane dehydrogenation, the hydrogen production rates (under OCP and Pd-H oxidation at the limiting current density) were quantified as a function of flow rate at 250 °C (FIG. 30). The overall hydrogen production rates (including permeated H2and residual H2) were found to be notably higher when electrochemical hydrogen pumping was conducted, irrespective of the membrane type or flow rate. Specifically, an over 60% enhancement in hydrogen production rates from 0.67 sccm to 1.06 sccm for Pd (0.66 sccm to 1.13 sccm for Pd-Ag) membrane was observed at a flow rate of 2.6 μL min−1methylcyclohexane. At this flow rate, the hydrogen separation yield reached 94.9% for Pd and further increased to 97.8% for Pd-Ag. As the methylcyclohexane flow rate was increased to 5.2 μL min−1and 10.4 μL min−1, an increase in hydrogen production rate to 1.10 sccm and 1.64 sccm was determined, but an attenuated enhancement of 29% for Pd (40% to Pd-Ag) in the total hydrogen production rate upon electrochemical hydrogen extraction. At these higher flow rates, the hydrogen separation yield declined slightly to 74.8% for Pd and 87.8% for Pd-Ag. Both the attenuated promotion in total H2production and the reduction in H2separation yield is attributed to the low residence of H2in the diffusion layer near the membrane surface. In all cases, hydrogen separation yield and promotion in total hydrogen production rate is higher for Pd-Ag relative to Pd due to higher hydrogen permeability in the former. Methylcyclohexane dehydrogenation is known to display a near zero reaction order in H2and thus the observed promotion in total H2production rate upon H2extraction is not attributed to a kinetic enhancement in the forward rate of dehydrogenation. Instead, H2extraction serves to inhibit the backward hydrogenation reaction leading to an enhancement in aggregate H2production upon pumping. The effect of electrochemical hydrogen pumping on the conversion of methylcyclohexane to toluene at 250 °C was further evaluated (FIG. 48 and FIG. 49). Based on GC quantification, it was determined that the selectivity toward toluene was close to 99.5% under OCP conditions, which was maintained at over 98% even under active hydrogen permeation conditions, suggesting that active hydrogen pumping has a minor effect on toluene selectivity (FIG. 48). The H2 / toluene ratio remained close to 3 under both OCP and active hydrogen permeation conditions, suggesting FoleyHoagUS12882195.4 MTV-21725 that the majority of hydrogen comes from conversion of methylcyclohexane to toluene, rather than coke formation. The high toluene selectivity and low coking observed in this system likely accrue from the low reaction temperature. For example, on a Pt / Al2O3catalyst, increasing the temperature from 280 °C to 400 °C can lead to a substantial decline in the toluene selectivity from 99.8% to 95.7%. Given the near quantitative reaction selectivity, the methylcyclohexane conversion can be calculated simply based on sum of the permeated H2and residual H2. At a flow rate of 2.6 μL min−1methylcyclohexane, the methylcyclohexane conversion under OCP conditions remained below the thermodynamic equilibrium conversion limit of 58.3% with an approach-to-equilibrium in the range of 0.34-0.37 (FIG. 49 and Table 5). However, upon active hydrogen extraction, this equilibrium limit can be exceeded, reaching over 75% with a Pd-Ag membrane. In line with the observations above, at higher flow rates and lower residence times, the methylcyclohexane conversion remained below the equilibrium limit. In a large scale device, the flow rate would be scaled with the effectively electrode area to preserve conversion levels roughly constant as the electrode area as increased. In this way, the desired conversion and hydrogen separation yields can be realized simply by extending catalyst beds and membrane area, as explicitly explored below. The thermodynamic conversion limit can also be overcome at lower temperatures with active hydrogen pumping (FIG. 31). At 225 °C, the methylcyclohexane conversion under active hydrogen pumping reaches 51.3% (triangle), well beyond the thermodynamic limit of 29.5% (dashed line) and OCP conversion of 20.6% (square). The approach-to-equilibrium (based on the residual H2pressure) decreases from 0.28 to 2.62×10−4(Table 5). Likewise at 200 °C, methylcyclohexane conversion under active hydrogen pumping reaches 31.9%, well beyond the equilibrium value of 13.7% and OCP value of 10.1%. Accordingly, the approach-to-equilibrium declines from 0.32 to 2.06×10−4(Table 5). This indicates that hydrogen pumping is particularly well-suited to promote low-temperature methylcyclohexane dehydrogenation and can potentially take advantage of low-grade heat. To demonstrate that further enhancement can be realized with an extended catalyst bed and membrane, electrochemical hydrogen pumping was performed with two identical electrochemical setups connected in series. With this series configuration, a total conversion of up to 94% at 250 °C was observed (star in FIG. 31), suggesting that a near stoichiometric conversion can be realized with an extended catalyst bed and membrane or multiple passes through the reactor. FoleyHoagUS12882195.4 MTV-21725 The presently disclosed findings compare favorably relative to other studies using membrane-based strategies for methylcyclohexane dehydrogenation and hydrogen separation, including zeolites, silica, glass, and passive Pd-based membranes (Table 6). FIG. 32 shows an evaluation and comparison of results obtained using different membrane reactors reported in literature with those of the presently disclosed electrochemical hydrogen pumping strategy. Consistent with the ammonia decomposition experiment, the data are plotted as methylcyclohexane conversion vs hydrogen separation factor / yield. The presently disclosed Pd- Ag membrane hydrogen pumping device provides exceptional performance in hydrogen separation and methylcyclohexane conversion over the temperature range of 200-250 °C. Although many other membrane reactors have been found to push methylcyclohexane dehydrogenation beyond equilibrium conversion, the presently disclosed electrochemical hydrogen pumping cell compared favorably to them. For example, silica and organosilica membranes present conversion enhancements from 59.2% to 93.4% and from 45.3% to 86.9%, respectively, but with modest separation factors of 2.2 and 20.4, respectively. The performance disclosed herein displays superior conversion enhancement of 51.3% to 94.4% while also furnishing a separation factor of 313.5. This superior performance is enabled by the electrochemical driving force and high permeability of Pd-Ag membrane in a dual cell configuration. Furthermore, unlike all other passive membrane separation approaches with a hydrogen partial pressure of less than 20 kPa (Table 6), these performance characteristics are paired with in-situ hydrogen concentration to 101.3 kPa, thus obviating the need for post- pressurization or additional separation steps. Derivation of Nernst equation for OCP FIG. 14 shows a concomitant decrease in the open circuit potential against the reversible hydrogen electrode potential (RHE) with the increase of hydrogen partial pressures in the thermochemical compartment. The deviation of the open circuit potential away from the RHE potential is established by reversible proton-coupled electron transfer (Volmer step) at the Pd|electrolyte interface. The OCP-hydrogen partial pressure relationship can be derived using the following chemical equations: H2dissociative adsorption at Pd|gas interface: H2↔ 2H*H transport through the Pd membrane to the Pd|electrolyte interface: 2H*↔ 2H· ↔ 2H*†FoleyHoagUS12882195.4 MTV-21725 Volmer step for Pd-H oxidation at the Pd|electrolyte interface: 2H*†↔ 2H++ 2e−For the Volmer step: Equation 1- 1 where ^^ୌ∗^and ^^ୌశ represent H* activity at the Pd|electrolyte interface and protonic activity, respectively. Under OCP conditions, assuming there is no net H transport through the Pd membrane, the H* activity at the Pd|gas (^^ୌ∗) and Pd|electrolyte (^^ୌ∗^) interface should be equal: ^^ୌ∗^ = ^^ୌ∗Equation 1- 2 The H* activity at the Pd|gas interface can be further established by the hydrogen partialpressure (^^ୌమ) in the thermochemical compartment via:^^ୌ∗ = ^^^^ ^.ହୌమEquation 1- 3 Thus, Equation 1- 4 For the reversible hydrogen electrode exposed to 1 atm H2:^^ ᇱୖୌ^ = ^^^ + ^^^^⁄ ^^ ln^^^ୌశ^Equation 1- 5 Thus, Equation 1- 6 The above equation revealed the relationship between open circuit potential and hydrogen partial pressure in the thermochemical compartment, with a prediction exactly matching the presently disclosed experimental data points. This correlation suggests that the open circuit potential can be used as an online readout of hydrogen partial pressure present in the thermochemical compartment. FoleyHoagUS12882195.4 MTV-21725 Richardson’s equation and hydrogen permeability The Richardson’s equation is as follows: Equation 2- 1 The hydrogen flux (JH2) is a function of permeability (PH2), membrane thickness (d), and hydrogen partial pressure (pH2). The permeability can be further expressed in terms of a permeability coefficient (P0H2) and activation energy (Ea) as per the Arrhenius equation. For sufficiently thick palladium membranes (d > 10 μm), the bulk diffusion through the Pd membrane is typically regarded as rate controlling. Considering Fick’s first law and Sievert’s law – the amount of dissolved hydrogen atoms in crystal lattice is proportional to the square root of hydrogen partial pressure, thus n = 0.5. Thus, permeability is a product of diffusivity and solubility. Under polarization to the limiting current regime, the effective hydrogen partial pressure at themembrane|electrolyte interface approaches zero. Thus, Equation 2-1 can be simplified as: Equation 2- 2 The hydrogen flux can be increased with increased permeability (Pd-Ag vs. Pd or increased temperature), reduced thickness (100 μm vs. 25 μm) and increased partial pressure. The limitingcurrent density (jlim) can be used to extract the permeability data using the following equation: Equation 2- 3 The experiments were conducted by recording the limiting current density and reading the residual hydrogen partial pressure in the outlet of the retentate stream via GC. The permeability data extracted by this analysis for Pd and Pd-Ag are consistent with those determined independently in the literature using conventional pressure-driven methods, as shown in FIG. 39 and FIG. 40. Calculation of Péclet number for H2transport in the catalyst layer during ammonia decomposition FoleyHoagUS12882195.4 MTV-21725 The Péclet number (Pe) is a dimensionless number that compares the rate of convectivetransport to the rate of diffusive transport of a species in a system and is defined as follows:^^ ∙ ^^^^^^ =^^^^^Equation 3- 1 Where u is gas linear velocity (cm s−1), L represents catalyst thickness (cm) and Deffis effective diffusivity (cm2s−1). When Pe ≪ 1, transport is diffusion-dominated and the system behaves like a fully mixed continuous stirred-tank reactor (CSTR) with uniform composition throughout the system. In contrast, Pe ≫ 1 indicates convection-dominated transport, characteristic of a plug flow reactor (PFR), where concentration gradients are preserved along the flow direction. While the linear velocity and catalyst thickness are known for a given system, the key challenge lies in estimating the effective diffusivity of H2in the NH3environment. Assuming the generated N2is negligible, the system can be treated as H2-NH3binary gas system. Thus, the diffusivity in a binary system (DAB) can be calculated according to Fuller-Schettler-Giddings(FSG) model: Equation 3- 2 Where T = temperature, K P = pressure, bar MA, MB= molecular weights of A and B, g mol−1MAB= 2[(1 / MA)+(1 / MB)]−1(3.58 g mol−1for H2-NH3binary gas) ∑vis defined by summing atomic diffusion volumes (4.62 for H2and 11.47 for NH3) Thus, H2diffusivity in NH3at 250 °C is 2.81 cm2s−1from Equation 3-2. The effective diffusivity in a porous media can be calculated as follows: Equation 3- 3 Where ε / τ = porosity / tortuosity ratio^^^^ or ^^^^ = ଶଷ ^^ ଼ோ்^.ହ^^గெ ^ , Knudsen diffusion coefficient (rp is pore diameter and M is molarmass) FoleyHoagUS12882195.4 MTV-21725 For CNTs powder, porosity can be calculated based on bulk density (ρbulk) and solid density(ρsolid) below:^^^^ = 1 − ୠ^୪୩^^^୭୪୧^Equation 3- 4 The tortuosity can be further estimated from the porosity according to the Bruggemanrelation9:^^ = ^^ି^.ହEquation 3- 5 Given the bulk density (~0.15 g mL−1) and solid density (2.1 g mL−1), Equation 3-4 and 3-5 yield a porosity of 0.93 and tortuosity of 1.04, respectively. Therefore, the porosity / tortuosity ratio is 0.894, which is used as an estimate for the Ru-Cs / CNTs catalyst layer. The calculated Knudsen diffusion coefficients for H2and NH3are 39.1 cm2s−1and 13.4 cm2s−1, respectively, if assuming a pore diameter of 5 μm for the catalyst layer. Thus, Equation 3-3 yield an effective diffusivity of 2.2 cm2s−1for H2. Since 2 sccm NH3is introduced into the catalyst layer (1.5-5.5 mm catalyst layer thicknesses), the gas linear velocity is estimated to 0.128 cm s−1at 250 °C. Thus, the calculated Pe according to Equation 3-1 is 0.05 and 0.014 for catalyst thickness of 1.5 and 5.5 mm, respectively. Both Pe values are much less than one, suggesting that the system can be treated as a CSTR. Calculation of hydrogen partial pressure at the membrane|gas interface in ammonia decomposition According to Equation 2-3, the hydrogen partial pressure at the Pd membrane|gas interface (pint) under hydrogen pumping (in the limiting current regime) can be calculated using thefollowing equation: Equation 4- 1 According to Equation 1-6, the hydrogen partial pressure at the Pd membrane|gas interfaceunder OCP can, thus be calculated using the following equation:^^୧୬^ FoleyHoagUS12882195.4 MTV-21725 Equation 4- 2 Table 1 H2production rate measured by GC vs. H2formation rate computed from passed current after a 25-hour durability test.* *The measurement was conducted under constant current electrolysis at 300 mA cm−2with 40 sccm 0.05 atm H2in the thermochemical compartment and 10 sccm Ar in the electrochemical compartment.aThe GC sampled the gas stream every 20 minutes. Table 2 Calculation of approach-to-equilibrium of ammonia decomposition under OCP or hydrogen pumping conditions at 250 °C. FoleyHoagUS12882195.4 MTV-21725 aThe reaction quotient (Q) is based on the equation: ^^ = , ^^^ୌ యrepresent partial pressures of N2, H2and NH3, respectively. bFor the approach-to-equilibrium calculation, the equilibrium constant (K) at 250 °C is 5.15 atm. Table 3. Comparison of the presently disclosed data with state-of-art Ru catalysts for ammonia decomposition under atmospheric pressure. FoleyHoagUS12882195.4 MTV-21725 *Data in the bracket were obtained with electrochemical H2extraction. a The term “CNTs” is an acronym for carbon nanotubes. FoleyHoagUS12882195.4 MTV-21725 ainom marofsrotcaerenarbmera-eht-fo-etatsemos thctiartwxeatH2ad tudoeshtoilw csid .neoisylr retunsesvnseerocrpp cdiee rreusht hpaefsm oo enmt toos anirreedad tpn ekmucon arCoitbie.sht 4opneil mabo tacTeadD*- 35 - FoleyHoagUS12882195.4 MTV-21725enaxeholcyclyhtemrofsrotcaerenarbmemtra-eht-fo-etatsemoshtiwat awd ndes. oe isrolrcu esssvnie odr cyl ptcdniererseuseh arp epse om ethm ttonfa eo re dnod tsn eikr ucaanrpoi bm teo an htC.e6g nio aterld aby Dah *Ted- 37 - FoleyHoagUS12882195.4 MTV-21725 DEFINITIONS Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art of the present disclosure. The following references provide one of skill with a general definition of many of the terms used in this disclosure: Singleton et al., Dictionary of Microbiology and Molecular Biology (2nd ed. 1994); The Cambridge Dictionary of Science and Technology (Walker ed., 1988); The Glossary of Genetics, 5th Ed., R. Rieger et al. (eds.), Springer Verlag (1991); and Hale & Marham, The Harper Collins Dictionary of Biology (1991). As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise. The transitional term “comprising”, which is synonymous with “including,” “containing,” or “characterized by,” is inclusive or open-ended, and does not exclude additional, unrecited elements or method steps. The transitional phrase “consisting of” excludes any element, step, or ingredient not specified in the claim. The transitional phrase “consisting essentially of” limits the scope of a claim to the specified materials or steps and those that do not materially affect the basic and novel characteristic(s) of the claimed invention. Ranges provided herein are understood to be shorthand for all of the values within the range. For example, a range of 1 to 50 is understood to include any number, combination of numbers, or sub-range from the group consisting 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50. Unless specifically stated or obvious from context, as used herein, the term "or" is understood to be inclusive; any species linked by "or" also includes any mixture thereof. Unless specifically stated or obvious from context, as used herein, the terms "a", "an", and "the" are understood to be singular or plural. Unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from context, all numerical values provided herein are modified by the term about. As used herein, the term “transition metal” refers to elements found in groups 3 through 12 of the periodic table of the elements. Transition metals include, but are not limited to, ruthenium, FoleyHoagUS12882195.4 MTV-21725 cobalt, nickel, iron, gold, copper, zinc, platinum, palladium, chromium, vanadium, molybdenum, copper, rhenium, iridium, rhodium, niobium, tantalum, and manganese. As used herein, the term “alkali metal” refers to elements found in group 1 of the periodic table of the elements, e.g., Li, Na, K, and Cs. As used herein, the term “alkali earth metal” refers to elements found in group 2 of the periodic table of the elements, e.g., Mg, Ca, and Ba. As used herein, the term “salt” refers to an acid addition salt derived from an inorganic acid, such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, metaphosphoric acid, and the like, where an acidic proton is replaced by a metal ion, e.g., an alkali metal ion (e.g. lithium, sodium, potassium), an alkaline earth ion (e.g. magnesium, or calcium), or an aluminum ion. Inorganic basic salts include aluminum hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate, sodium hydroxide, and the like. Inert salts can have as their cation an element from group 1 or 2 of the periodic table of the elements and an anion comprising an element from the groups 15-17 of the periodic table of the elements. Such cations include Li+, Na+, K+, Rb+, Cs+, Mg2+, and Ca2+. Such anions include CO32-, HCO3-, PO43-, HPO42-, H2PO4-, NO2-, NO3-, SO42-, HSO4-, F-, Cl-, Br- and I-, CH3COO-, and CF3COO-. Exemplary salts include Li2CO3, K2HPO4, MgCl2, NaCl, KCl, etc. As used herein, the term “H-conductive membrane” refers to a dense non-porous membrane that allows for transport of hydrogen atom equivalents. In some embodiments, an H- conductive membrane allows for transport of hydrogen atoms or proton / electron pairs. Materials suitable for an H-conductive membrane include, but are not limited to, palladium, niobium, vanadium, tungsten, molybdenum, or tantalum, or a combination thereof. For example, an H- conductive membrane can comprise or consist of palladium or palladium alloy. Further, an H- conductive membrane comprises, for example, an alloy of palladium, niobium, vanadium, tungsten, molybdenum, or tantalum, or a combination thereof. In some embodiments, an H- conductive membrane comprises, for example, doped perovskites oxides, such as yttrium-doped BaCeO3, ytterbium-doped SrCeO3, or yttrium-doped BaZrO3, or a combination thereof. In some embodiments, an H-conductive membrane comprises, for example, a cerium-based oxide, such as Gd-doped ceria. In some embodiments, an H-conductive membrane comprises, for example, lanthanum tungstate or its doped form, doped bismuth oxide, hydrated tungsten oxide, or nickel oxide, or a combination thereof. FoleyHoagUS12882195.4 MTV-21725 As used herein, the term “hydrogen atom equivalent” refers to any atomic or molecular species consisting of atoms each having a single proton in the nucleus. Hydrogen atom equivalents (HAEs) include, but are not limited to, a hydrogen atom, and a proton / electron pair. As used herein, the term “hydrogen evolution catalyst” refers to a material capable of catalyzing decomposition of water into hydrogen and hydroxyl anions. Hydrogen evolution catalysts include, but are not limited to, platinum group metals (e.g., Pt, Pd, Ru, Ir, and Rh), as well as non-noble metals and compounds thereof, such as Ni, Mo2C, WC, MoS2, and NiCo2Px. In some embodiments, the present disclosure relates to a method of hydrogen production, comprising: (a) providing a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane, wherein: the membrane is located between the catalytic chamber and the electrochemical chamber; the catalytic chamber comprises a catalyst layer; and the electrochemical chamber comprises a counter electrode and a molten electrolyte; (b) introducing a gaseous mixture comprising a hydrogen-containing compound to the catalytic chamber; (c) contacting the hydrogen-containing compound with the catalyst layer, thereby producing hydrogen atom equivalents (HAEs) and a dehydrogenated compound; (d) transferring the HAEs across the membrane; (e) applying an electrical potential difference between the membrane and the counter electrode, thereby oxidizing the HAEs to generate protons; (f) contacting the protons with the molten electrolyte, thereby generating protonated electrolyte anions; and (g) contacting the protonated electrolyte anions with the counter electrode, thereby reducing the protonated electrolyte anions and generating recovered hydrogen. In some embodiments, the hydrogen-containing compound is selected from the group consisting of ammonia, a hydrocarbon, and alcohol, or is a mixture thereof. In some embodiments, hydrogen-containing compound is ammonia. In some embodiments, the hydrogen- containing compound is a hydrocarbon. In some embodiments, the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, methanol, ethanol, isopropanol, 2-butanol, cyclohexanol, and FoleyHoagUS12882195.4 MTV-21725 ethylbenzene. In some embodiments, the hydrogen-containing compound is a hydrocarbon. In some embodiments, the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, ethanol, isopropanol, 2- butanol, cyclohexanol, and ethylbenzene. In some embodiments, the hydrogen-containing compound is methanol. In some embodiments, the hydrogen-containing compound is ethane. In some embodiments, the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n-butene, isobutene, benzene, toluene, styrene, formaldehyde, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone. In some embodiments, the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n- butene, isobutene, benzene, toluene, styrene, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone. In some embodiments, the dehydrogenated compound is ethylene. In some embodiments, the dehydrogenated compound is styrene. In some embodiments, the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% of the hydrogen-containing compound. For example, the gaseous mixture comprises about 1 vol.% to about 100 vol.%, about 5 vol.% to about 100 vol.%, about 10 vol.% to about 100vol.%, about 20 vol.% to about 100 vol.%, about 10 vol.% to about 100 vol.% ̧about 30 vol.% toabout 100 vol.%, about 40 vol.% to about 100 vol.% ̧about 50 vol.% to about 100 vol.%̧about60 vol.% to about 100 vol. about 70 vol.% to about 100 vol.% ̧about 80 vol.% to about 100vol.% ̧about 90 vol.% to about 100 vol.% ̧0.1 vol.% to about 90 vol.%, about 0.1 vol.% toabout 80 vol.%, about 0.1 vol.% to about 70 vol.%, about 0.1 vol.% to about 60 vol.%, about 0.1vol.% to about 50 vol.% ̧about 0.1 vol.% to about 40 vol.%, about 0.1 vol.% to about 30 vol.% ̧about 0.1 vol.% to about 20 vol.%̧about 0.1 vol.% to about 10 vol.%̧about 1 vol.% to about 90vol.% ̧about 1 vol.% to about 70 vol.% ̧about 1 vol.% to about 50 vol.% ̧about 1 vol.% toabout 30 vol.% ̧about 1 vol.% to about 10 vol.% ̧about 5 vol.% to about 90 vol.% ̧about 5vol.% to about 70 vol.% ̧about 5 vol.% to about 50 vol.% ̧about 5 vol.% to about 30 vol.% ̧about 5 vol.% to about 10 vol.% ̧about 10 vol.% to about 90 vol.% ̧about 10 vol.% to about 70vol.% ̧about 10 vol.% to about 50 vol.% ̧about 10 vol.% to about 30 vol.% ̧about 20 vol.% toabout 90 vol.% ̧about 20 vol.% to about 70 vol.%¸ about 20 vol.% to about 50 vol.%̧about 20vol.% to about 30 vol.% ̧about 30 vol.% to about 90 vol.% ̧about 30 vol.% to about 70 vol.%̧about 30 vol.% to about 50 vol.% ̧about 40 vol.% to about 90 vol.% ̧about 40 vol.% to about 70FoleyHoagUS12882195.4 MTV-21725vol.% ̧about 40 vol.% to about 50 vol.% ̧about 50 vol.% to about 90 vol.% ̧about 50 vol.% toabout 70 vol.% ̧about 60 vol.% to about 90 vol.%¸ about 60 vol.% to about 70 vol.%̧or about70 vol.% to about 90 vol.%¸of the hydrogen-containing compound. In some embodiments, the gaseous mixture comprises about 100 vol.%, about 90 vol.%, about 80 vol.%, about 70 vol.%,about 60 vol.%, about 50 vol.% ̧about 40 vol.%, about 30 vol.% ̧about 20 vol.% ̧about 10vol.% ̧about 5 vol.% ̧about 1 vol.% ̧or about 0.1 vol.% of the hydrogen-containing compound.In some embodiments, the gaseous mixture consists of the hydrogen-containing compound. In some embodiments, the gaseous mixture does not comprise hydrogen. In some embodiments, the gaseous mixture comprises hydrogen. In some embodiments, the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% of hydrogen. For example, the gaseous mixture comprises about 1 vol.% to about 100 vol.%, about 5 vol.% to about 100 vol.%, about 10 vol.% to about 100 vol.%, about 20 vol.% to about 100 vol.%, about 10 vol.% toabout 100 vol.% ̧about 30 vol.% to about 100 vol.%, about 40 vol.% to about 100 vol.%̧about50 vol.% to about 100 vol.% ̧about 60 vol.% to about 100 vol. about 70 vol.% to about 100vol.% ̧about 80 vol.% to about 100 vol.% ̧about 90 vol.% to about 100 vol.% ̧0.1 vol.% toabout 90 vol.%, about 0.1 vol.% to about 80 vol.%, about 0.1 vol.% to about 70 vol.%, about 0.1vol.% to about 60 vol.%, about 0.1 vol.% to about 50 vol.% ̧about 0.1 vol.% to about 40 vol.%,about 0.1 vol.% to about 30 vol.%̧about 0.1 vol.% to about 20 vol.%̧about 0.1 vol.% to about10 vol.% ̧about 1 vol.% to about 90 vol.% ̧about 1 vol.% to about 70 vol.% ̧about 1 vol.% toabout 50 vol.% ̧about 1 vol.% to about 30 vol.% ̧about 1 vol.% to about 10 vol.% ̧about 5vol.% to about 90 vol.% ̧about 5 vol.% to about 70 vol.% ̧about 5 vol.% to about 50 vol.% ̧about 5 vol.% to about 30 vol.% ̧about 5 vol.% to about 10 vol.% ̧about 10 vol.% to about 90vol.% ̧about 10 vol.% to about 70 vol.% ̧about 10 vol.% to about 50 vol.% ̧about 10 vol.% toabout 30 vol.% ̧about 20 vol.% to about 90 vol.%¸ about 20 vol.% to about 70 vol.%̧about 20vol.% to about 50 vol.% ̧about 20 vol.% to about 30 vol.% ̧about 30 vol.% to about 90 vol.%̧about 30 vol.% to about 70 vol.% ̧about 30 vol.% to about 50 vol.% ̧about 40 vol.% to about 90vol.% ̧about 40 vol.% to about 70 vol.% ̧about 40 vol.% to about 50 vol.% ̧about 50 vol.% toabout 90 vol.% ̧about 50 vol.% to about 70 vol.%¸ about 60 vol.% to about 90 vol.%̧about 60vol.% to about 70 vol.% ̧or about 70 vol.% to about 90 vol.%¸hydrogen. In some embodiments,the gaseous mixture comprises about 100 vol.%, about 90 vol.%, about 80 vol.%, about 70vol.%, about 60 vol.%, about 50 vol.% ̧about 40 vol.%, about 30 vol.% ̧about 20 vol.% ̧aboutFoleyHoagUS12882195.4 MTV-2172510 vol.% ̧about 5 vol.% ̧about 1 vol.% ̧or about 0.1 vol.% hydrogen. In some embodiments,the gaseous mixture consists of hydrogen. In some embodiments, the catalyst layer comprises a support and a catalyst disposed on the support. In some embodiments, the catalyst is dispersed on the support. In some embodiments, the support comprises carbon, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate. In some embodiments, the support comprises carbon, stainless steel mesh, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate. In some embodiments, the support comprises graphite felt. In some embodiments, the catalyst comprises ruthenium, cobalt, nickel, iron, gold, copper, zinc, platinum, palladium, chromium oxide, vanadium oxide, molybdenum oxide, gallium oxide, copper oxide, zinc oxide, iron oxide, carbon, transition metal nitride, transition metal carbide, alkali metal amides, or alkali metal imide, or a combination thereof. For example, in certain embodiments, the catalyst comprises iron carbide, cobalt carbide, nickel carbide, titanium carbide, vanadium carbide, manganese carbide, chromium carbide, iron nitride, cobalt nitride, nickel nitride, titanium nitride, vanadium nitride, manganese nitride, or chromium nitride, or a combination thereof. In some embodiments, the catalyst comprises lithium amide, sodium amide, potassium amide, lithium imide, lithium calcium imide, or lithium magnesium imide, or a combination thereof. In some embodiments, the catalyst comprises ruthenium. In some embodiments, the catalyst comprises platinum. In some embodiments, the catalyst layer further comprises a promoter. In some embodiments, the promoter comprises lithium, sodium, potassium, cesium, calcium, barium, tin, zinc, gallium, indium, or germanium, or a combination thereof. In some embodiments, the promoter comprises cesium. In some embodiments, the promoter comprises magnesium. In some embodiments, the catalyst layer comprises a hydrogen dissociation catalyst. In some embodiments, the hydrogen dissociation catalyst is selected from the group consisting of Pd, Pt, Rh, Ru, Ir, Au, Ag, Cu, Fe, Ni, Co, Re, V, Ta, Mo, or W, or a combination thereof. In some embodiments, the catalyst layer is disposed on the H-conductive membrane. In some embodiments, the catalyst layer comprises ruthenium and cesium. In some embodiments, the support comprises carbon nanotubes; the catalyst comprises ruthenium; and the promoter comprises cesium. FoleyHoagUS12882195.4 MTV-21725 In some embodiments, the molten electrolyte comprises an alkali metal hydroxide, alkali metal carbonate, alkali metal halide, alkaline-earth metal halide, alkali metal perchlorate, alkali metal nitrate, or alkali metal metaphosphate, or a eutectic mixture thereof. In some embodiments, the molten electrolyte comprises an alkali metal hydroxide. In some embodiments, the molten electrolyte comprises a eutectic mixture of two or more alkali metal hydroxides. In some embodiments, the molten electrolyte comprises a eutectic mixture of two or more electrolytes selected from alkali metal halide and alkaline-earth metal halide. In some embodiments, the molten electrolyte comprises KOH and NaOH. In some embodiments, the molten electrolyte comprises MgCl2, KCl, and NaCl. In some embodiments, the molten electrolyte further comprises an inert metal oxide selected from the group consisting of Al2O3, ZrO2, HfO2, Y2O3, or a combination of any of them. In some embodiments, the molten electrolyte further comprises a solid proton conductor. In some embodiments, the solid proton conductor comprises a proton-conducting metal oxide. In some embodiments, the proton-conducting metal oxide is selected from the group consisting of SrZrO3, BaCeO3, BaZrO3, SrCeO3, or a combination of any of them. In some embodiments, the proton-conducting metal oxide is doped with a dopant selected from the group consisting of Y, Sc, In, Gd, Sm, or a combination of any of them. In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the inert metal oxide. In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 80 mol%, about 0.1 mol% to about 70 mol%, about 0.1 mol% to about 60 mol%,about 0.1 mol% to about 50 mol% ̧about 0.1 mol% to about 40 mol%, about 0.1 mol% to about30 mol% ̧about 0.1 mol% to about 20 mol% ̧about 0.1 mol% to about 10 mol% ̧about 1 mol%to about 90 mol% ̧about 1 mol% to about 70 mol% ̧about 1 mol% to about 50 mol% ̧about 1mol% to about 30 mol% ̧about 1 mol% to about 10 mol% ̧about 5 mol% to about 90 mol% ̧about 5 mol% to about 70 mol%̧about 5 mol% to about 50 mol% ̧about 5 mol% to about 30mol% ̧about 5 mol% to about 10 mol% ̧about 10 mol% to about 90 mol% ̧about 10 mol% toabout 70 mol% ̧about 10 mol% to about 50 mol%¸ about 10 mol% to about 30 mol% ̧about 20mol% to about 90 mol% ̧about 20 mol% to about 70 mol% ̧about 20 mol% to about 50 mol% ̧about 20 mol% to about 30 mol% ̧about 30 mol% to about 90 mol% ̧about 30 mol% to about70 mol% ̧about 30 mol% to about 50 mol% ̧about 40 mol% to about 90 mol%̧about 40 mol%FoleyHoagUS12882195.4 MTV-21725to about 70 mol% ̧about 40 mol% to about 50 mol% ̧about 50 mol% to about 90 mol% ̧about50 mol% to about 70 mol% ̧about 60 mol% to about 90 mol% ̧about 60 mol% to about 70mol% ̧or about 70 mol% to about 90 mol% of the inert metal oxide. In some embodiments, themolten electrolyte comprises about 90 mol%, about 80 mol%, about 70 mol%, about 60 mol%,about 50 mol% ̧about 40 mol%, about 30 mol% ̧about 20 mol% ̧about 10 mol% ̧about 5mol% ̧about 1 mol% ̧or about 0.1 mol% of the inert metal oxide.In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the proton-conducting metal oxide. In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 80 mol%, about 0.1 mol% to about 70 mol%, about 0.1mol% to about 60 mol%, about 0.1 mol% to about 50 mol% ̧about 0.1 mol% to about 40 mol%,about 0.1 mol% to about 30 mol% ̧about 0.1 mol% to about 20 mol% ̧about 0.1 mol% to about10 mol% ̧about 1 mol% to about 90 mol% ̧about 1 mol% to about 70 mol% ̧about 1 mol% toabout 50 mol% ̧about 1 mol% to about 30 mol% ̧about 1 mol% to about 10 mol%̧about 5mol% to about 90 mol% ̧about 5 mol% to about 70 mol% ̧about 5 mol% to about 50 mol% ̧about 5 mol% to about 30 mol%̧about 5 mol% to about 10 mol% ̧about 10 mol% to about 90mol% ̧about 10 mol% to about 70 mol% ̧about 10 mol% to about 50 mol% ̧about 10 mol% toabout 30 mol% ̧about 20 mol% to about 90 mol%¸ about 20 mol% to about 70 mol% ̧about 20mol% to about 50 mol% ̧about 20 mol% to about 30 mol% ̧about 30 mol% to about 90 mol% ̧about 30 mol% to about 70 mol% ̧about 30 mol% to about 50 mol% ̧about 40 mol% to about90 mol% ̧about 40 mol% to about 70 mol% ̧about 40 mol% to about 50 mol%̧about 50 mol%to about 90 mol% ̧about 50 mol% to about 70 mol% ̧about 60 mol% to about 90 mol% ̧about60 mol% to about 70 mol% ̧or about 70 mol% to about 90 mol% of the proton-conducting metaloxide. In some embodiments, the molten electrolyte comprises about 90 mol%, about 80 mol%,about 70 mol%, about 60 mol%, about 50 mol% ̧about 40 mol%, about 30 mol%̧about 20mol% ̧about 10 mol% ̧about 5 mol%̧about 1 mol% ̧or about 0.1 mol% of the proton-conducting metal oxide. In some embodiments, the counter electrode comprises a hydrogen evolution catalyst. In some embodiments, the hydrogen evolution catalyst comprises platinum, palladium, rhenium, iridium, rhodium, or nickel, or a combination thereof. In some embodiments, the counter electrode comprises carbon, manganese, iron, cobalt, nickel, zinc, aluminum, or a combination thereof. FoleyHoagUS12882195.4 MTV-21725 In some embodiments, the electrochemical chamber comprises an electrically insulating separator between the membrane and the counter electrode. In some embodiments, the electrically insulating separator comprises alumina, magnesia, silica, chromite, zirconia, or calcium hexaluminate, or a mixture thereof. In some embodiments, the membrane comprises a metal selected from palladium, niobium, vanadium, tungsten, molybdenum, and tantalum, or a combination thereof. In some embodiments, the membrane comprises an alloy comprising palladium, niobium, vanadium, tungsten, molybdenum, or tantalum, or a combination thereof. In some embodiments, the membrane comprises palladium or palladium alloy. In some embodiments, the membrane comprises yttrium-doped BaCeO3, ytterbium-doped SrCeO3, or yttrium-doped BaZrO3, Gd- doped ceria, lanthanum tungstate, doped lanthanum tungstate, doped bismuth oxide, hydrated tungsten oxide, nickel oxide, or a combination thereof. In some embodiments, the membrane comprises an alloy of palladium and silver. In some embodiments, the membrane comprises an alloy of palladium and copper. In some embodiments, the molten electrolyte is maintained at a temperature of about 180 °C to about 1300 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 200 °C to about 1000 °C, about 200 °C to about 800 °C, about 200 °C to about 600 °C, about 200 °C to about 400 °C, about 250 °C to about 1000 °C, about 250 °C to about 800 °C,about 250 °C to about 600 °C ̧from about 250 °C to about 500 °C ̧about 250 °C to about 400°C, about 250 °C to about 350°C, about 300 °C to about 1000 °C, about 300 °C to about 800 °C, about 300 °C to about 600 °C, or about 300 °C to about 400 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 1000 °C, about 800 °C, about 600 °C,about 500 °C, about 450 °C, about 400 °C, about 350 °C ̧about 300 °C¸ or about 250 °C. Insome embodiments, the molten electrolyte is maintained at a temperature of about 450 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 400 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 385 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 350 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 300 °C. In some embodiments, the temperature is about 250 °C to about 500 °C. In some embodiments, the temperature is about 300 °C to about 400 °C. In some embodiments, the method further comprises FoleyHoagUS12882195.4 MTV-21725 h) providing a hydrogenation substrate; and i) reacting the hydrogenation substrate with the recovered hydrogen under conditions sufficient to hydrogenate the hydrogenation substrate. In some embodiments, the method further comprises isolating the dehydrogenated compound. In some embodiments, the present disclosure relates to a method of reducing a substrate, comprising: (a) providing a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane, wherein: the membrane is located between the catalytic chamber and the electrochemical chamber; the catalytic chamber optionally comprises a catalyst layer; and the electrochemical chamber comprises a counter electrode and a molten electrolyte; (b) providing the substrate in the electrochemical chamber; (c) introducing to the catalytic chamber a gaseous mixture comprising hydrogen or a hydrogen- containing compound; (d) if the gaseous mixture comprises a hydrogen-containing compound, contacting the hydrogen- containing compound with the catalyst layer, thereby producing HAEs and a dehydrogenated compound; (e) if the gaseous mixture comprises hydrogen, contacting the hydrogen with the catalyst layer or the H-conductive membrane, thereby producing HAEs; (f) transferring the HAEs across the membrane; (g) applying an electrical potential difference between the membrane and the counter electrode, thereby oxidizing the HAEs to generate protons and placing the protons in contact with the molten electrolyte to generate protonated electrolyte anions; and (h) contacting the counter electrode with the substrate and the protonated electrolyte anions, thereby generating a reduced substrate. In some embodiments, the gaseous mixture comprises a hydrogen-containing compound is selected from the group consisting of ammonia, hydrocarbon, and alcohol, or is a mixture thereof. In some embodiments, hydrogen-containing compound is ammonia. In some embodiments, the hydrogen-containing compound is a hydrocarbon. In some embodiments, the hydrogen-containing compound is selected from the group consisting of ethane, propane, n- FoleyHoagUS12882195.4 MTV-21725 butane, iso-butane, cyclohexane, methylcyclohexane, ethanol, isopropanol, 2-butanol, cyclohexanol, and ethylbenzene. In some embodiments, the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, methanol, ethanol, isopropanol, 2-butanol, cyclohexanol, and ethylbenzene. In some embodiments, the hydrogen-containing compound is methanol. In some embodiments, the hydrogen-containing compound is ethane. In some embodiments, the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% of the hydrogen-containing compound. For example, the gaseous mixture comprises about 1 vol.% to about 100 vol.%, about 5 vol.% to about 100 vol.%, about 10 vol.% to about 100vol.%, about 20 vol.% to about 100 vol.%, about 10 vol.% to about 100 vol.% ̧about 30 vol.% toabout 100 vol.%, about 40 vol.% to about 100 vol.% ̧about 50 vol.% to about 100 vol.%̧about60 vol.% to about 100 vol. about 70 vol.% to about 100 vol.% ̧about 80 vol.% to about 100vol.% ̧about 90 vol.% to about 100 vol.% ̧0.1 vol.% to about 90 vol.%, about 0.1 vol.% toabout 80 vol.%, about 0.1 vol.% to about 70 vol.%, about 0.1 vol.% to about 60 vol.%, about 0.1vol.% to about 50 vol.% ̧about 0.1 vol.% to about 40 vol.%, about 0.1 vol.% to about 30 vol.% ̧about 0.1 vol.% to about 20 vol.%̧about 0.1 vol.% to about 10 vol.%̧about 1 vol.% to about 90vol.% ̧about 1 vol.% to about 70 vol.% ̧about 1 vol.% to about 50 vol.% ̧about 1 vol.% toabout 30 vol.% ̧about 1 vol.% to about 10 vol.% ̧about 5 vol.% to about 90 vol.% ̧about 5vol.% to about 70 vol.% ̧about 5 vol.% to about 50 vol.% ̧about 5 vol.% to about 30 vol.% ̧about 5 vol.% to about 10 vol.% ̧about 10 vol.% to about 90 vol.% ̧about 10 vol.% to about 70vol.% ̧about 10 vol.% to about 50 vol.% ̧about 10 vol.% to about 30 vol.% ̧about 20 vol.% toabout 90 vol.% ̧about 20 vol.% to about 70 vol.%¸ about 20 vol.% to about 50 vol.%̧about 20vol.% to about 30 vol.% ̧about 30 vol.% to about 90 vol.% ̧about 30 vol.% to about 70 vol.%̧about 30 vol.% to about 50 vol.% ̧about 40 vol.% to about 90 vol.% ̧about 40 vol.% to about 70vol.% ̧about 40 vol.% to about 50 vol.% ̧about 50 vol.% to about 90 vol.% ̧about 50 vol.% toabout 70 vol.% ̧about 60 vol.% to about 90 vol.%¸ about 60 vol.% to about 70 vol.%̧or about70 vol.% to about 90 vol.%¸of the hydrogen-containing compound. In some embodiments, the gaseous mixture comprises about 100 vol.%, about 90 vol.%, about 80 vol.%, about 70 vol.%,about 60 vol.%, about 50 vol.% ̧about 40 vol.%, about 30 vol.% ̧about 20 vol.% ̧about 10vol.% ̧about 5 vol.% ̧about 1 vol.% ̧or about 0.1 vol.% of the hydrogen-containing compound.In some embodiments, the gaseous mixture consists of the hydrogen-containing compound. FoleyHoagUS12882195.4 MTV-21725 In some embodiments, the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n-butene, isobutene, benzene, toluene, styrene, formaldehyde, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone. In some embodiments, the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n- butene, isobutene, benzene, toluene, styrene, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone. In some embodiments, the dehydrogenated compound is ethylene. In some embodiments, the dehydrogenated compound is styrene. In some embodiments, the method comprises further isolating the dehydrogenated compound. In some embodiments, the catalyst layer comprises a support and a catalyst disposed on the support. In some embodiments, the catalyst is dispersed on the support. In some embodiments, the support comprises carbon, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate. In some embodiments, the support comprises carbon, stainless steel mesh, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate. In some embodiments, the support comprises graphite felt. In some embodiments, the catalyst comprises ruthenium, cobalt, nickel, iron, gold, copper, zinc, platinum, palladium, chromium oxide, vanadium oxide, molybdenum oxide, gallium oxide, copper oxide, zinc oxide, iron oxide, carbon, transition metal nitride, transition metal carbide, alkali metal amides, or alkali metal imide, or a combination thereof. For example, in certain embodiments, the catalyst comprises iron carbide, cobalt carbide, nickel carbide, titanium carbide, vanadium carbide, manganese carbide, chromium carbide, iron nitride, cobalt nitride, nickel nitride, titanium nitride, vanadium nitride, manganese nitride, or chromium nitride, or a combination thereof. In some embodiments, the catalyst comprises lithium amide, sodium amide, potassium amide, lithium imide, lithium calcium imide, or lithium magnesium imide, or a combination thereof. In some embodiments, the catalyst comprises ruthenium. In some embodiments, the catalyst comprises platinum. In some embodiments, the catalyst layer further comprises a promoter. In some embodiments, the promoter comprises lithium, sodium, potassium, cesium, calcium, barium, tin, zinc, gallium, indium, or germanium, or a combination thereof. In some embodiments, the promoter comprises cesium. In some embodiments, the promoter comprises magnesium. FoleyHoagUS12882195.4 MTV-21725 In some embodiments, the catalyst layer comprises a hydrogen dissociation catalyst. In some embodiments, the hydrogen dissociation catalyst is selected from the group consisting of Pd, Pt, Rh, Ru, Ir, Au, Ag, Cu, Fe, Ni, Co, Re, V, Ta, Mo, or W, or a combination thereof. In some embodiments, the catalyst layer is disposed on the H-conductive membrane. In some embodiments, the catalyst layer comprises ruthenium and cesium. In some embodiments, the support comprises carbon nanotubes; the catalyst comprises ruthenium; and the promoter comprises cesium. In some embodiments, the molten electrolyte comprises an alkali metal hydroxide, alkali metal carbonate, alkali metal halide, alkaline-earth metal halide, alkali metal perchlorate, alkali metal nitrate, or alkali metal metaphosphate, or a eutectic mixture thereof. In some embodiments, the molten electrolyte comprises an alkali metal hydroxide. In some embodiments, the molten electrolyte comprises a eutectic mixture of two or more alkali metal hydroxides. In some embodiments, the molten electrolyte comprises a eutectic mixture of two or more electrolytes selected from alkali metal halide and alkaline-earth metal halide. In some embodiments, the molten electrolyte comprises KOH and NaOH. In some embodiments, the molten electrolyte comprises MgCl2, KCl, and NaCl. In some embodiments, the molten electrolyte further comprises an inert metal oxide selected from the group consisting of Al2O3, ZrO2, HfO2, Y2O3, or a combination of any of them. In some embodiments, the molten electrolyte further comprises a solid proton conductor. In some embodiments, the solid proton conductor comprises a proton-conducting metal oxide. In some embodiments, the proton-conducting metal oxide is selected from the group consisting of SrZrO3, BaCeO3, BaZrO3, SrCeO3, or a combination of any of them. In some embodiments, the proton-conducting metal oxide is doped with a dopant selected from the group consisting of Y, Sc, In, Gd, Sm, or a combination of any of them. In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the inert metal oxide. In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 80 mol%, about 0.1 mol% to about 70 mol%, about 0.1 mol% to about 60 mol%,about 0.1 mol% to about 50 mol% ̧about 0.1 mol% to about 40 mol%, about 0.1 mol% to about30 mol% ̧about 0.1 mol% to about 20 mol% ̧about 0.1 mol% to about 10 mol% ̧about 1 mol%to about 90 mol% ̧about 1 mol% to about 70 mol% ̧about 1 mol% to about 50 mol% ̧about 1FoleyHoagUS12882195.4 MTV-21725mol% to about 30 mol%̧about 1 mol% to about 10 mol%̧about 5 mol% to about 90 mol%̧about 5 mol% to about 70 mol%̧about 5 mol% to about 50 mol%̧about 5 mol% to about 30mol%̧about 5 mol% to about 10 mol%̧about 10 mol% to about 90 mol%̧about 10 mol% toabout 70 mol%̧about 10 mol% to about 50 mol%¸ about 10 mol% to about 30 mol%̧about 20mol% to about 90 mol%̧about 20 mol% to about 70 mol%̧about 20 mol% to about 50 mol%̧about 20 mol% to about 30 mol%̧about 30 mol% to about 90 mol%̧about 30 mol% to about70 mol%̧about 30 mol% to about 50 mol%̧about 40 mol% to about 90 mol%̧about 40 mol%to about 70 mol%̧about 40 mol% to about 50 mol%̧about 50 mol% to about 90 mol%̧about50 mol% to about 70 mol%̧about 60 mol% to about 90 mol%̧about 60 mol% to about 70mol%̧or about 70 mol% to about 90 mol% of the inert metal oxide. In some embodiments, themolten electrolyte comprises about 90 mol%, about 80 mol%, about 70 mol%, about 60 mol%,about 50 mol%̧about 40 mol%, about 30 mol%̧about 20 mol%̧about 10 mol%̧about 5mol%̧about 1 mol%̧or about 0.1 mol% of the inert metal oxide.In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the proton-conducting metal oxide. In some embodiments, the molten electrolyte comprises about 0.1 mol% to about 80 mol%, about 0.1 mol% to about 70 mol%, about 0.1mol% to about 60 mol%, about 0.1 mol% to about 50 mol%̧about 0.1 mol% to about 40 mol%,about 0.1 mol% to about 30 mol%̧about 0.1 mol% to about 20 mol%̧about 0.1 mol% to about10 mol%̧about 1 mol% to about 90 mol%̧about 1 mol% to about 70 mol%̧about 1 mol% toabout 50 mol%̧about 1 mol% to about 30 mol%̧about 1 mol% to about 10 mol%̧about 5mol% to about 90 mol%̧about 5 mol% to about 70 mol%̧about 5 mol% to about 50 mol%̧about 5 mol% to about 30 mol%̧about 5 mol% to about 10 mol%̧about 10 mol% to about 90mol%̧about 10 mol% to about 70 mol%̧about 10 mol% to about 50 mol%̧about 10 mol% toabout 30 mol%̧about 20 mol% to about 90 mol%¸ about 20 mol% to about 70 mol%̧about 20mol% to about 50 mol%̧about 20 mol% to about 30 mol%̧about 30 mol% to about 90 mol%̧about 30 mol% to about 70 mol%̧about 30 mol% to about 50 mol%̧about 40 mol% to about90 mol%̧about 40 mol% to about 70 mol%̧about 40 mol% to about 50 mol%̧about 50 mol%to about 90 mol%̧about 50 mol% to about 70 mol%̧about 60 mol% to about 90 mol%̧about60 mol% to about 70 mol%̧or about 70 mol% to about 90 mol% of the proton-conducting metaloxide. In some embodiments, the molten electrolyte comprises about 90 mol%, about 80 mol%,about 70 mol%, about 60 mol%, about 50 mol%̧about 40 mol%, about 30 mol%̧about 20FoleyHoagUS12882195.4 MTV-21725mol% ̧about 10 mol% ̧about 5 mol%̧about 1 mol% ̧or about 0.1 mol% of the proton-conducting metal oxide. In some embodiments, the counter electrode comprises a hydrogen evolution catalyst. In some embodiments, the hydrogen evolution catalyst comprises platinum, palladium, rhenium, iridium, rhodium, or nickel, or a combination thereof. In some embodiments, the counter electrode comprises carbon, manganese, iron, cobalt, nickel, zinc, aluminum, or a combination thereof. In some embodiments, the electrochemical chamber comprises an electrically insulating separator between the membrane and the counter electrode. In some embodiments, the electrically insulating separator comprises alumina, magnesia, silica, chromite, zirconia, or calcium hexaluminate, or a mixture thereof. In some embodiments, the membrane comprises a metal selected from palladium, niobium, vanadium, tungsten, molybdenum, and tantalum, or a combination thereof. In some embodiments, the membrane comprises an alloy comprising palladium, niobium, vanadium, tungsten, molybdenum, or tantalum, or a combination thereof. In some embodiments, the membrane comprises palladium or palladium alloy. In some embodiments, the membrane comprises. In some embodiments, the membrane comprises yttrium-doped BaCeO3, ytterbium- doped SrCeO3, or yttrium-doped BaZrO3, Gd-doped ceria, lanthanum tungstate, doped lanthanum tungstate, doped bismuth oxide, hydrated tungsten oxide, nickel oxide, or a combination thereof. In some embodiments, the membrane comprises an alloy of palladium and silver. In some embodiments, the membrane comprises an alloy of palladium and copper. In some embodiments, the molten electrolyte is maintained at a temperature of about 180 °C to about 1300 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 200 °C to about 1000 °C, about 200 °C to about 800 °C, about 200 °C to about 600 °C, about 200 °C to about 400 °C, about 250 °C to about 1000 °C, about 250 °C to about 800 °C,about 250 °C to about 600 °C ̧from about 250 °C to about 500 °C ̧from about 250 °C to about400 °C, about 250 °C to about 350°C, about 300 °C to about 1000 °C, about 300 °C to about 800 °C, about 300 °C to about 600 °C, or from about 300 °C to about 400 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 1000 °C, about 800 °C, about 600°C, about 500 °C, about 450 °C, about 400 °C, about 350 °C ̧about 300 °C ̧or about 250 °C. Insome embodiments, the molten electrolyte is maintained at a temperature of about 450 °C. In FoleyHoagUS12882195.4 MTV-21725 some embodiments, the molten electrolyte is maintained at a temperature of about 400 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 385 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 350 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 300 °C. In some embodiments, the temperature is about 250 °C to about 500 °C. In some embodiments, the temperature is about 300 °C to about 400 °C. In some embodiments, the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% of hydrogen. For example, the gaseous mixture comprises about 1 vol.% to about 100 vol.%, about 5 vol.% to about 100 vol.%, about 10 vol.% to about 100 vol.%, about 20 vol.% toabout 100 vol.%, about 10 vol.% to about 100 vol.% ̧about 30 vol.% to about 100 vol.%, about40 vol.% to about 100 vol.% ̧about 50 vol.% to about 100 vol.% ̧about 60 vol.% to about 100vol. about 70 vol.% to about 100 vol.% ̧about 80 vol.% to about 100 vol.% ̧about 90 vol.% toabout 100 vol.% ̧0.1 vol.% to about 90 vol.%, about 0.1 vol.% to about 80 vol.%, about 0.1vol.% to about 70 vol.%, about 0.1 vol.% to about 60 vol.%, about 0.1 vol.% to about 50 vol.% ̧about 0.1 vol.% to about 40 vol.%, about 0.1 vol.% to about 30 vol.%̧about 0.1 vol.% to about20 vol.% ̧about 0.1 vol.% to about 10 vol.% ̧about 1 vol.% to about 90 vol.% ̧about 1 vol.% toabout 70 vol.% ̧about 1 vol.% to about 50 vol.% ̧about 1 vol.% to about 30 vol.% ̧about 1vol.% to about 10 vol.% ̧about 5 vol.% to about 90 vol.% ̧about 5 vol.% to about 70 vol.% ̧about 5 vol.% to about 50 vol.% ̧about 5 vol.% to about 30 vol.% ̧about 5 vol.% to about 10vol.% ̧about 10 vol.% to about 90 vol.% ̧about 10 vol.% to about 70 vol.% ̧about 10 vol.% toabout 50 vol.% ̧about 10 vol.% to about 30 vol.%¸ about 20 vol.% to about 90 vol.%̧about 20vol.% to about 70 vol.% ̧about 20 vol.% to about 50 vol.% ̧about 20 vol.% to about 30 vol.%̧about 30 vol.% to about 90 vol.% ̧about 30 vol.% to about 70 vol.% ̧about 30 vol.% to about 50vol.% ̧about 40 vol.% to about 90 vol.% ̧about 40 vol.% to about 70 vol.% ̧about 40 vol.% toabout 50 vol.% ̧about 50 vol.% to about 90 vol.%¸ about 50 vol.% to about 70 vol.%̧about 60vol.% to about 90 vol.% ̧about 60 vol.% to about 70 vol.% ̧or about 70 vol.% to about 90vol.%¸hydrogen. In some embodiments, the gaseous mixture comprises about 100 vol.%, about90 vol.%, about 80 vol.%, about 70 vol.%, about 60 vol.%, about 50 vol.% ̧about 40 vol.%,about 30 vol.% ̧about 20 vol.% ̧about 10 vol.% ̧about 5 vol.% ̧about 1 vol.% ̧or about 0.1vol.% hydrogen. In some embodiments, the gaseous mixture consists of hydrogen. In some embodiments, the gaseous mixture does not comprise hydrogen. FoleyHoagUS12882195.4 MTV-21725 In some embodiments, the substrate and the molten electrolyte form an admixture. In some embodiments, the substrate and the molten electrolyte form a heterogeneous admixture. In some embodiments, the substrate and the molten electrolyte form a homogeneous admixture. In some embodiments, the substrate is dissolved in the molten electrolyte. In some embodiments, the substrate is a metal oxide. In some embodiments, the metal oxide comprises manganese oxide, iron oxide, cobalt oxide, nickel oxide, zinc oxide, or aluminum oxide, or a combination thereof. In some embodiments of the substrate comprises an oxide of a main group element. In some embodiments, the substrate comprises phosphorus oxide, phosphate, metaphosphate, silicate, silica, tin oxide, indium oxide, gallium oxide, or a combination thereof. In some embodiments, the reduced substrate comprises an elemental metal. In some embodiments, the reduced substrate comprises an elemental main group element. In some embodiments, the reduced substrate comprises elemental phosphorus, silicon, tin, indium, gallium, manganese, iron, cobalt, nickel, zinc, or aluminum, or a combination thereof. As used herein, the term “elemental metal” refers to a metallic element wherein the oxidation state is zero. Elemental metal can refer to a pure sample of a metallic element in the oxidation state of zero or an alloy comprising the metallic element in the oxidation state of zero. As used herein, the term “elemental main group element” refers to a main group element (i.e., a non-metal) wherein the oxidation state is zero. Elemental main group element can refer to a pure sample of a main group element in the oxidation state of zero or mixture of compounds or elements comprising the main group element in the oxidation state of zero. In some embodiments, the present disclosure relates to a method for dehydrogenating a chemical species by coupling thermochemical and electrochemical reactions. In some embodiments, a target substrate is supplied to a device consisting of a catalytic chamber, an electrochemical chamber, and a H-conductive membrane separating the two chambers. In some embodiments, said substrate is converted to hydrogen and a dehydrogenated product in the catalytic chamber. In some embodiments, an electrical potential difference is applied between the membrane and a counter electrode in the electrochemical chamber. In some embodiments, HAEs are transported from the catalytic chamber through the H-conductive membrane and are oxidized FoleyHoagUS12882195.4 MTV-21725 to electrons and protons in the presence of a molten electrolyte. In some embodiments, said electrons and protons are then used to carry out a reduction reaction at the counter electrode. In some embodiments, the present disclosure relates to a method for supplying hydrogen equivalents to a molten-salt electro-reduction process. In some embodiments, the method is performed in a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane separating the two chambers. In some embodiments, the method comprise supplying a hydrogen-containing species to the catalytic chamber, where the H-atom equivalents are transferred to the H-conductive membrane; applying an electrical potential difference between the membrane and a counter electrode in the electrochemical chamber; transporting hydrogen atom equivalents from the catalytic chamber through the H-conductive membrane and oxidizing the hydrogen atom equivalents to electrons and protons. In some embodiments, the protons react spontaneously with constituents in the molten salt electrolyte. In some embodiments the electrons are used to carry out a reduction reaction at the counter electrode. In some embodiments, the substrate is ammonia, alkane, ethylbenzene or alcohol. In some embodiments, said alkane is ethane, propane, n-butane, i-butane, cyclohexane or methylcyclohexane. In some embodiments, the alcohol is methanol, ethanol, isopropanol, 2- butanol or cyclohexanol. In some embodiments, the alcohol is methanol. In some embodiments, the alcohol is ethanol, isopropanol, 2-butanol or cyclohexanol. In some embodiments, the dehydrogenated product comprises ethylene, propylene, n-butene, isobutene, benzene or toluene. In some embodiments, the dehydrogenated product comprises styrene. In some embodiments, the dehydrogenated product comprises formaldehyde, acetaldehyde, acetone, methyl ethyl ketone or cyclohexanone. In some embodiments, the dehydrogenated product comprises acetaldehyde, acetone, methyl ethyl ketone or cyclohexanone. In some embodiments, the catalytic chamber further comprises a flow field, metal mesh, metal washer, gas-permeable sheet and a catalyst layer for the dehydrogenation reaction. In some embodiments, the catalyst and / or promoter is active for ammonia decomposition. In some embodiments, the catalyst comprises ruthenium, cobalt, nickel, iron, transition metal nitrides / carbides, or alkali metal amides / imides. In some embodiments, the promoter comprises lithium, sodium, potassium, cesium, calcium, barium or any combination of two or more thereof. In some embodiments, the catalyst and / or promoter is active for dehydrogenation FoleyHoagUS12882195.4 MTV-21725 of ethane, propane, n-butane, i-butane, methylcyclohexane or ethylbenzene. In some embodiments, the catalyst comprises platinum, palladium, chromium oxide, vanadium oxide, molybdenum oxide, gallium oxide, carbon or iron oxide. In some embodiments, the promoter comprises tin, zinc, gallium, indium, germanium or alkali metals. In some embodiments, the catalyst is active for the dehydrogenation of methanol, ethanol, isopropanol, 2-butanol or cyclohexanol. In some embodiments, the catalyst is active for the dehydrogenation of ethanol, isopropanol, 2-butanol or cyclohexanol. In some embodiments, the catalyst is active for the dehydrogenation of methanol. In some embodiments, the catalyst comprises platinum, palladium, gold, ruthenium, copper, zinc, chromium oxide, copper oxide or zinc oxide. In some embodiments, the H-conductive membrane comprises one of palladium or palladium alloy. In some embodiments, the membrane surface is smooth or roughened with nano-size or micro-sized palladium or palladium-alloy. In some embodiments, the roughening is provided with electrodeposition or electroless deposition. In some embodiments, the H-conductive membrane comprises a metal selected from niobium, vanadium, and tantalum. In some embodiments, the electrochemical chamber comprises a flow field, molten electrolyte, and an electrically insulating separator between the membrane and counter electrodes. In some embodiments, the molten electrolyte comprises alkali metal hydroxides or their eutectic mixtures. In some embodiments, the molten electrolyte comprises alkali metal carbonates or their eutectic mixtures. In some embodiments, the molten electrolyte comprises alkali metal halides, alkaline-earth metal halides or their eutectic mixtures. In some embodiments, the molten electrolyte comprises alkali metal perchlorates or their eutectic mixtures. In some embodiments, the molten electrolyte comprises alkali metal nitrates, or their eutectic mixtures. In some embodiments, the molten electrolyte comprises sodium metaphosphate, lithium metaphosphate, potassium metaphosphate, or a mixture thereof. In some embodiments, the electrochemical chamber contains a reference electrode. In some embodiments, the reference electrode comprises platinum, palladium, rhodium, iridium, rhenium, silver, nickel or carbon. In some embodiments, the reference electrode further comprises Na / Na+reference electrode. In some embodiments, the reduction reaction produces hydrogen. FoleyHoagUS12882195.4 MTV-21725 The invention now being generally described, it will be more readily understood by reference to the following examples, which are included merely for purposes of illustration of certain aspects and embodiments of the present invention and are not intended to limit the invention. EXAMPLES Chemicals and materials The following chemicals were used as received. Any chemicals or materials requiring additional preparation are described in their own subsection below. MilliQ water (Millipore Type 1, 18.2^MΩ^cm) was used as the source of ultrapure water for all applications described below. Potassium hydroxide (KOH, Millipore Sigma, 99.99%); Sodium hydroxide (NaOH, Millipore Sigma, 99.99%); Multi-walled carbon nanotube (MWCNTs, O.D. 6-13 nm × L 2.5-20 μm, Millipore Sigma, 98%); Ruthenium(III) nitrosyl nitrate solution (Ru(NO)(NO3)x(OH)y, x+y=3, Millipore Sigma, 1.5% Ru); Cesium hydroxide monohydrate (CsOH·H2O, Millipore Sigma, 99.95%); Palladium(II) chloride (PdCl2, Millipore Sigma, 99.99%); Hydrochloric acid (37 wt.% HCl in H2O, Millipore Sigma, 99.999%); Sulfuric acid (H2SO4, Millipore Sigma, 95.0-98.0%); Methylcyclohexane (C7H14, Millipore Sigma, 99%); Toluene (C7H8, Millipore Sigma, 99.8%); Platinum on carbon (5 wt.% Pt / C, Millipore Sigma); Drierite desiccant (10-20 mesh, Millipore Sigma); Pd foil (0.025 mm, Thermo Scientific, 99.9%) Pd-Ag foil (75:25 wt.%, 0.025 mm, Thermo Scientific, 99.9%); Au foil (0.025 mm thick, Thermo Scientific, 99.95%); Pt wire (1.0 mm thick, BeanTown, 99.95%), Nickel wire (1.0 mm thick, BeanTown, 99.98%) and Pt gauze (45 mesh, BeanTown, 99.9%) were purchased from VWR. Compressible PTFE gasket (Gore GR, 0.0625” thick) Stainless steel mesh (500 × 500 and 50 × 50), 2-bore alumina tube (O.D. 0.5”, I.D.0.063”) were purchased from McMaster-Carr. Carbon paper (AvCarb MGL190) and nickel foam (80-120 PPI, 1 mm) were purchased from FuelCellStore. Alumina tubes (O.D.0.5”, I.D.0.375”, length 2”) were purchased from AdValue Technology. Example 1: Palladium membrane acting as a H-oxidizing anode As shown in FIG. 1, the electrochemical cell was constructed with two customized stainless-steel jackets. The stainless-steel jacket further consisted of three integrated tubes: bottom FoleyHoagUS12882195.4 MTV-21725 tube (0.5” outside diameter × 0.3” inner diameter × 1” length), middle tube (0.75” outside diameter × 0.5” inner diameter × 0.375” length) and top tube (1.5” outside diameter x 0.5” inner diameter × 0.25” length). Three symmetric holes were drilled through the top tube to accommodate screws used in the assembly. The stainless-steel jackets were interfaced to a Swagelok® union cross and union tee to provide feed gas for the two sides of the H-conducting membrane, including thermochemical compartment and electrochemical compartment. A customized palladium membrane was used as the H-oxidizing anode. A palladium foil (15 mm x 15 mm x 25 μm) was electroplated with palladium black on one side and tailed to a disk (0.5” diameter). The palladium black provided more surface area for hydrogen adsorption and dissociation. A nickel wire (1 mm diameter) connected to a nickel foam served as the counter electrode. A platinum wire (1 mm diameter) integrated with a platinum mesh (50 mesh × 50 mesh) served as the reference electrode. Both electrodes were incorporated into a two-bore alumina tube in order to prevent shorting between the stainless-steel parts and reference or counter electrodes in the electrochemical compartment. The electrochemical cell was assembled by stacking an aluminum gasket (0.5” outside diameter × 0.3” inner diameter × 0.6 mil thickness) on one stainless-steel jacket, followed by the customized palladium membrane (palladium black side facing down), a first gold gasket (0.5” outside diameter × 0.3” inner diameter × 0.001” thickness), an alumina tube (0.5” outside diameter × 0.375” inner diameter × 2” length), a second gold gasket (0.5” outside diameter × 0.375” inner diameter × 0.001” thickness) and completed with the second stainless-steel jacket. Hydroxide pellets (1.2 g sodium hydroxide and 1.6 g potassium hydroxide) were crushed with hydraulic press and introduced to the alumina tube via the opening of the union cross. Standard hex bolts, flat washers, and Belleville washers were used to compress the cell assembly and provide gas-tight seals. A high-temperature wire in contact with the stainless-steel parts of the cell was extended to a potentiostat. Argon gas was introduced to the thermochemical and electrochemical compartment and the entire cell was insulated with fiberglass wool. An electrical heating tape (Omega Engineering), PID controller (Omega Engineering), and J-type thermocouple were used to heat and maintain the cell at 350 °C. The two-bore alumina tube with counter and reference electrodes was then introduced to the electrochemical compartment through the opening of the union cross. As shown in FIG.2, electrochemical hydrogen oxidation on palladium anode was verified with linear sweep voltammetry using a BioLogic potentiostat. In operation, 5 vol.% FoleyHoagUS12882195.4 MTV-21725 hydrogen / argon gas mixture or pure argon was introduced to the thermochemical compartment while pure hydrogen flowed through the electrochemical compartment. The graphs in FIGs.3 and 4 show the relationship between the applied potentials and the current on the palladium anode. When Ar was fed into the thermochemical compartment, the polarization curve in FIG. 3 displayed characteristic features of palladium, including under-potential hydrogen adsorption / desorption and surface oxide formation or reduction. As displayed in FIG. 4, in the presence of 5 vol.% H2, the anodic current initially displayed a rapid rise and started to plateau at higher potentials. This plateau current increased with the increase of flow rate, suggesting that the hydrogen oxidation rate was limited by mass transport of hydrogen to the palladium membrane surface in the thermochemical compartment. When the gas was switched to 100% H2, the current displayed a trend without limit in mass transport and a current as high as 175 mA was achieved with a potential difference of less than 45 mV. In both cases, the operating potential windows to reach mass transport limit were much lower than the potential at which surface oxide starts to form, demonstrating that the H-conductive palladium membrane is a very effective H-oxidizing anode and thus presents oxidative corrosion in molten electrolytes. Example 2: Promotion of ammonia dehydrogenation with palladium anode An electrochemical cell of the type described in Example 1 was used with the incorporation of a 3-mm catalyst layer (Ru+Cs supported on graphite felt) for ammonia dehydrogenation. The catalyst was prepared by incipient wetness impregnation. Specifically, a 3-mm thick graphite felt substrate (SynLectro) was heated in air at 400 °C for 3 hours to improve surface wetness. The pretreated graphite felt was tailed to a disk with a diameter of 0.3”. An aqueous solution containing RuCl3(0.1 M) and CsNO3(0.25 M) with Cs-to-Ru ratio of 2.5 was added to the graphite felt until the graphite felt was completely soaked. After the impregnation, the sample was dried in an oven at 120 °C overnight, followed by reduction in 5 vol.% H2 / Ar atmosphere at 300 °C for 3 hours. The assembly procedure described in Example 1 was followed except that the catalyst layer was assembled first. The catalyst layer was assembled by first stacking a piece of stainless- steel mesh (50 × 50) which was integrated to a customized stainless-steel spacer (0.5” outside diameter × 0.3” inner diameter × 0.15” thickness). The catalyst supported on the graphite felt disk FoleyHoagUS12882195.4 MTV-21725 was then placed in the center hole of the spacer. The subsequent assembly procedure was the same as described in Example 1. As shown in FIG. 5, ammonia dehydrogenation was coupled with electrochemical hydrogen oxidation on the palladium anode. The process was demonstrated with pure ammonia gas introduced to the thermochemical chamber containing the Ru+Cs catalyst layer. The catalyst layer catalyzed the dehydrogenation of NH3to give N2and H2. H2was adsorbed on palladium black, dissociated and transported to the palladium membrane surface facing the electrolyte. The surface hydrogen was then oxidized to protons and recombined with hydroxide ions to form water, which moved to the surface of the counter electrode (nickel cathode) and was reduced to form hydrogen. FIG. 6 displays the polarization curves of the palladium anode with / without Ru+Cs catalyst. When no catalyst was employed, no appreciable hydrogen oxidation current was observed at 350 °C. In contrast, the limiting hydrogen oxidation current increased to more than 175 mA when the Ru+Cs catalyst was used. This value decreased to about 50 mA after the temperature decreased by 50 °C. These observations suggest that both catalyst and temperature play a key role in ammonia dehydrogenation. FIG. 7 shows the relationship between H2formation rate in the electrochemical compartment and the hydrogen oxidation current. The correlation of these values corresponded to 100% Faradaic efficiency, suggesting that all the electrons were used to generate hydrogen at the nickel cathode and there was no parasitic reaction in the molten hydroxide electrolyte. The effect of the palladium anode on ammonia dehydrogenation is shown in FIG. 8. Compared to the open-circuit potential condition at 350 °C, a more than 8-fold increase of the conversion efficiency was realized with active electrochemical hydrogen oxidation at the palladium anode. A slightly higher enhancement was observed at lower temperature (300 °C). Such impressive enhancements suggest that the presence of hydrogen inhibits the reaction kinetics of ammonia dehydrogenation. Accordingly, this example demonstrates the effectiveness of coupling thermochemical catalysis of dehydrogenation to electrochemical oxidation of hydrogen equivalents to electrons and protons. Example 3: Promotion of ethane dehydrogenation with palladium anode An electrochemical cell constructed in Example 2 was used except the incorporation of commercial 40 wt.% Pt / C catalyst for ethane dehydrogenation. The assembly procedure described in Example 2 was followed except that a piece of carbon paper (0.3” diameter) was introduced to support the Pt / C catalyst layer. FoleyHoagUS12882195.4 MTV-21725 As shown in FIG.5, the ethane dehydrogenation process was coupled with electrochemical hydrogen oxidation on the palladium anode. The example was demonstrated with pure ethane gas introduced to the thermochemical chamber with a Pt / C catalyst layer. The catalyst layer catalyzed the dehydrogenation of C2H6to C2H4and H2, which was adsorbed on palladium black, dissociated and transported to the palladium surface facing electrolyte. The surface hydrogen was then oxidized to protons and recombined with hydroxide ions to form water, which moved to the surface of the counter electrode (nickel cathode) and was reduced to form hydrogen. FIG. 9 displays the polarization curves of the palladium anode with / without Pt / C catalyst at 400 °C. When no catalyst was employed, no significant hydrogen oxidation current was observed. In the presence of Pt / C catalyst, the hydrogen oxidation rate increased to a limiting current of 2.7 mA, suggesting Pt / C can indeed catalyze the ethane dehydrogenation. FIG.10 shows the change of flow rate of H2and C2H4in the thermochemical compartment after changing the potential from open-circuit to 0.45 V vs. RHE. Under open-circuit conditions, the flow rate of C2H4was slightly lower than that of H2, suggesting the presence of carbon deposition. With a more positive polarization, the hydrogen flow rate decreased along with an increase in C2H4formation rate. Generally, the enhancements in C2H4suggest that ethane dehydrogenation could be promoted by coupling thermochemical catalysis of dehydrogenation to electrochemical oxidation of hydrogen equivalents to electrons and protons. Example 4: Steel production coupled to catalytic dehydrogenation with palladium anode As shown in FIG. 11, steel production is coupled to catalytic dehydrogenation with electrochemical hydrogen oxidation on palladium anode. The process is demonstrated with H2- containing gas or H-containing substrates introduced to the thermochemical compartment in the presence of a thermocatalytic catalyst layer. The introduced hydrogen or hydrogen formed in a dehydrogenation process as described in Examples 2 and 3 is adsorbed, dissociated, and transported through the palladium membrane to the electrochemical interface with molten chloride electrolyte (MgCl2-KCl-NaCl) containing dispersed iron oxide. The melting point of MgCl2-KCl- NaCl is lowered to 385 °C following a molar ratio of 44.7: 25.8: 29.4. Under positive polarization, the surface hydrogen on palladium surface is oxidized to electrons and protons, which then leaches out the dispersed iron oxide powder in the molten electrolyte to generate Fe3+and H2O. The generated Fe3+species are further reduced to metallic iron at the iron cathode or graphite cathode. FoleyHoagUS12882195.4 MTV-21725 Alternatively, the Fe3+generated is first reduced to Fe2+on the palladium anode and then further reduced to metallic iron at the cathode. The by-product, H2O, is removed from the system by inert gas, i.e. Ar or N2, in the form of steam. In summary, the thermochemical compartment provides hydrogen sources to depolarize the anode reaction for steel production. Example 5: Preparation of working electrode (Pd-based membrane) A Pd-based disk with electrochemically deposited Pd black was used the working electrode. The palladium black provided more surface area for hydrogen adsorption and dissociation. Specifically, a palladium or palladium-silver foil (15 mm × 15 mm × 25 µm) was assembled in a home-made cell with a circular area (0.31” diameter) exposed to the electrolyte. The foil was first electrochemically cleaned in Ar-saturated 0.5 M H2SO4solution with a 30-cycle voltametric scan between 0.1 V and 1.1 V vs. Ag / AgCl (3M KCl) at a scan rate of 50 mV / s. The electrolyte was then disposed and rinsed with Miili-Q water. About 5 mL 1 M HCl solution containing 15.9 mM PdCl2was transferred to the cell and sparged with Ar for 30 min before the electrochemical deposition of Pd black. For Pd black deposition, the foil was polarized potentiostatically to −0.20 V vs. Ag / AgCl (3M KCl) until 4 C of change was passed. The solution was then disposed, and the treated foil was thoroughly washed with Milli-Q water. The foil was dried under flowing air and then tailored to a disk (0.5” diameter) for electrochemical cell assembly. Example 6: Preparation of reference and counter electrode A platinum wire (1.0 mm diameter) or nickel wire (1.0 mm diameter) connected to a nickel foam served as the counter electrode. A platinum wire (1.0 mm diameter) integrated with a platinum mesh (50 mesh × 50 mesh) served as the reference electrode (when tested under 1 atm. H2). The reference electrode was cleaned with a 30-cycle voltametric scan between 0.1 V and 1.1 V vs. Ag / AgCl in Ar-saturated 0.5 M H2SO4solution. Both electrodes were incorporated into a two-bore alumina tube in order to prevent shorting between the stainless-steel parts and reference or counter electrodes in the electrochemical compartment. FoleyHoagUS12882195.4 MTV-21725 Example 7: Preparation of Ru-Cs / CNTs catalyst precursor The Ru-Cs / CNTs catalyst precursor was prepared by incipient wetness impregnation, modified from a previous report. In a typical synthesis, 60 mg CNTs were weighed and transferred to a 20 mL scintillation vial. An aqueous solution containing 0.106 M Ru3+and 0.30 M Cs+were prepared by mixing 421.8 μL Ruthenium(III) nitrosyl nitrate solution (1.5% Ru content) with 208.2 μL CsOH·H2O solution (0.90 M). 420 μL solution was then transferred via a micropipette to the vial in a drop-wise fashion until the CNTs powders were completely soaked. The vial was then allowed to stand for 30 min before heated in an oven at 120 °C for 3 hours. The resulting granules were then ground into a powder in an agate mortar and stored in a 4 mL glass vial. Example 8: Electrochemical cell assembly As shown in FIG. 1, the electrochemical cell was constructed with two customized stainless-steel jackets. The stainless-steel jacket further consisted of three integrated tubes: bottom tube (0.5” outside diameter × 0.3” inner diameter × 1” length), middle tube (0.75” outside diameter × 0.5” inner diameter × 0.375” length) and top tube (1.5” outside diameter × 0.5” inner diameter × 0.25” length). Three symmetric holes were drilled through the top tube to accommodate screws used in the assembly. The stainless-steel jackets were interfaced to a Swagelok® union cross and union tee to provide feed gas for the thermochemical compartment and electrochemical compartment. In absence of the catalyst layer, the electrochemical cell was assembled by stacking an aluminum gasket (0.5” outside diameter × 0.3” inner diameter × 0.6 mil thickness) on one stainless-steel jacket, followed by the working electrode (palladium black side facing down), a first gold gasket (0.5” outside diameter × 0.3” inner diameter × 0.001” thickness), an alumina tube (0.5” outside diameter × 0.375” inner diameter × 2” length), a second gold gasket (0.5” outside diameter × 0.375” inner diameter × 0.001” thickness) and completed with the second stainless- steel jacket. Note that the gold gaskets can be replaced with compressible PTFE gaskets (0.5” outside diameter × 0.3” inner diameter × 0.0625” thickness). Hydroxide pellets (1.2 g sodium hydroxide and 1.6 g potassium hydroxide) were crushed with hydraulic press and introduced to the alumina tube via the opening of the union cross. Standard hex bolts, flat washers, and Belleville washers were used to compress the cell assembly and provide gas-tight seals. A high-temperature wire in contact with the stainless-steel parts of the cell was connected to a Biologic potentiostat as FoleyHoagUS12882195.4 MTV-21725 the working electrode (The Pd-based membrane was electrically connected to the stainless-steel components). The gas-tightness of the system was evaluated by introducing 10 sccm argon gas into both the thermochemical and electrochemical compartments using an Alicat mass flow controller. The outlet was connected to an Alicat mass flow meter, and the difference between the inlet and outlet flow rates were maintained below 1% prior to proceeding to the next step. An electrical heating tape (Omega Engineering), PID controller (Omega Engineering), and J-type thermocouple were used to heat and maintain the cell at a specific temperature. And the entire cell was insulated with fiberglass wool to eliminate the heat loss. Example 9: Hydrogen pumping experiment The hydrogen pumping experiment was conducted without the introduction of a catalyst layer. After the above cell assembly procedure, the cell was heated to 300 °C in 90 min with 10 sccm argon introduced into both the thermochemical and electrochemical compartment. The two- bore alumina tube with counter and reference electrodes was then lowered into the molten electrolyte. 40 sccm 5 vol.% hydrogen / argon gas mixture was introduced to the thermochemical compartment while 10 sccm hydrogen flowed through the electrochemical compartment. Open- circuit potential measurements, voltammetric scans, and chronoamperometry were carried out using a BioLogic potentiostat. Prior to the electrochemical measurements, the working electrode was cycled between 0.1 V and 0.5 V Vs. RHE at a scan rate of 20 mV / s for 30 cycles. The uncompensated Ohmic resistance of the system was measured using a current-interrupt technique. Example 10: Ammonia decomposition experiment A catalyst layer was incorporated into the electrochemical cell for ammonia decomposition experiment. The assembly procedure described above was followed except that the catalyst layer was assembled first. The catalyst layer was assembled by first stacking a piece of 316 stainless- steel mesh (50 × 50) and carbon paper (AvCarb MGL190) which was integrated to a customized stainless-steel spacer (0.5” outside diameter × 0.3” inner diameter × 4 mm thickness). Approximately 35^mg of the Ru–Cs / CNTs catalyst precursor prepared as described in Example 7 was loaded into a stainless-steel spacer with a depth of 3.5^mm. For catalyst layer thicknesses of 1.5^mm and 5.5^mm, spacers with total thicknesses of 2^mm and 6^mm were used, respectively, FoleyHoagUS12882195.4 MTV-21725 corresponding to catalyst precursor loadings of 15^mg and 55^mg. The subsequent assembly procedure was the same as described above. The cell was heated to 250 °C in 70 min with 10 sccm argon introduced into both the thermochemical and electrochemical compartment. Upon reaching 250 °C, the gas in thermochemical compartment was switched to 10 sccm hydrogen and maintained for 100 min. The two-bore alumina tube with counter and reference electrodes was then lowered into the molten electrolyte, followed by introduction of 10 sccm hydrogen into the electrochemical compartment. The working electrode was cycled between 0 V and 0.25 V Vs. RHE at a scan rate of 20 mV / s for 30 cycles. Afterward, the gas in the thermochemical compartment was switched back to 10 sccm argon for 60 min until the open-circuit potential exceeded 250 mV. Ammonia was then introduced into the thermochemical compartment under open-circuit conditions. Open-circuit potential measurements, voltammetric scans, and chronoamperometry were carried out using a BioLogic potentiostat. Example 11: Methylcyclohexane dehydrogenation experiment A Pt / C catalyst layer was incorporated into the electrochemical cell for methylcyclohexane dehydrogenation experiment. The Pt / C catalyst layer was assembled by first stacking a piece of 316 stainless-steel mesh (50 × 50) and stainless steel mesh (500 × 500) which was integrated to a customized stainless-steel spacer (0.5” outside diameter × 0.3” inner diameter × 2 mm thickness). Approximately 15^mg of the Pt / C catalyst precursor was loaded into a stainless-steel spacer with a depth of 1.5^mm. The subsequent assembly procedure was the same as described above. The cell was heated to 250 °C in 70 min with 10 sccm argon introduced into both the thermochemical and electrochemical compartment. Upon reaching 250 °C, the gas in thermochemical compartment was switched to 40 sccm 5 vol.% hydrogen / argon gas mixture and maintained for 60 min. The two-bore alumina tube with counter and reference electrodes was then lowered into the molten electrolyte, followed by introduction of 10 sccm hydrogen into the electrochemical compartment. The working electrode was cycled between 0 V and 0.5 V Vs. RHE at a scan rate of 20 mV / s for 30 cycles. Afterward, the gas in the thermochemical compartment was switched back to 10 sccm argon for 10 min. Liquid methylcyclohexane was introduced into the system using a infuse only syringe pump at flow rates of 2.6, 5.2, and 10.4^μL / min, and preheated to 160^°C before entering the thermochemical compartment. The flow rate of the carrier FoleyHoagUS12882195.4 MTV-21725 gas, argon, was correspondingly adjusted to 0.5, 2, and 4^sccm. Open-circuit potential measurements, voltammetric scans, and chronoamperometry were carried out using a BioLogic potentiostat. Example 12: Ethane dehydrogenation experiment An electrochemical cell of the type described in Example 8 was used with the incorporation of a Pt 0.5wt.%, Sn 0.25wt.% catalyst supported on Ga 2.0wt%(MgAlO6) procured from Nexceris. Instead of the piece of carbon paper, a stainless-steel mesh (500 x 500, 0.3” diameter) was layered on top of the stainless-steel (50 x 50) mesh to hold the catalyst within the custom stainless-steel spacer. Two experiments were carried out, one in the temperature range of 400 – 475 °C employing a eutectic molten hydroxide mixture of NaOH:KOH with a molar ratio of 51:49 as molten electrolyte, and a second experiment over the temperature range of 475 – 550 °C using pure LiOH as molten electrolyte. The ethane dehydrogenation process was coupled with electrochemical hydrogen oxidation on the palladium anode. The example was demonstrated with pure ethane gas introduced to the thermochemical chamber with the PtSn / Mg(Ga)AlO6catalyst and an argon sweep gas stream in the electrochemical compartment. The catalyst catalyzed the conversion of C2H6 to C2H4 and H2, which was adsorbed on palladium black, dissociated, and transported to the palladium surface facing the molten electrolyte. The surface hydrogen was then oxidized and reacted with hydroxide ions to form water, which diffused to the Ni counter electrode, where it was reduced to form H2and regenerate hydroxide ions. FIG.50 displays the conversion of C2H6as a function of temperature. The black line with square markers shows the conversion attained under open-circuit potential, which closely approaches the calculated equilibrium conversion shown by the grey curve with empty triangular markers. The red line with circular makers shows the conversion under polarization of the cell close to the limiting current, leading to a 3.5-fold improvement in conversion compared to OCP conditions at 550 °C and far exceeding the nominal equilibrium conversion at that temperature. The data suggest that ethane dehydrogenation to ethylene is significantly promoted by removing hydrogen equivalents from the thermochemical chamber under active turnover conditions. FoleyHoagUS12882195.4 MTV-21725 Example 13: Product analysis Hydrogen content was quantified using an on-line gas chromatograph (GC, SRI Instrument Muli-Gas Analyzer #5) equipped with a thermal conductivity detector (TCD) and one MolSieve 5A column and two Hayesep D columns connected in series. For ammonia decomposition experiments, residual ammonia was first absorbed in 2.0 M H2SO4solution and the remaining H2and N2were diluted with 20 sccm argon before passing through a vial containing Drierite desiccants and entering the GC for analysis; For methylcyclohexane dehydrogenation, methylcyclohexane and toluene were trapped by benzyl alcohol, and the residual hydrogen was diluted with 10 sccm argon before GC analysis. Methylcyclohexane and toluene were also quantified by on-line GC using the same SRI Instrument Muli-Gas Analyzer #5, equipped with both a TCD and flame ionization detector (FID), along with one MolSieve 5A column and a 30^m MXT-624 column (Restek) connected in series. The downstream gas mixture was diluted with 20 sccm Ar and introduced to the GC through stainless-steel tubing maintained at 160 °C. INCORPORATION BY REFERENCE All US and PCT patent application publications and US patents mentioned herein are hereby incorporated by reference in their entirety as if each individual patent application publication or patent was specifically and individually indicated to be incorporated by reference. In case of conflict, the present application, including any definitions herein, will control. EQUIVALENTS While specific embodiments of the subject invention have been discussed, the above specification is illustrative and not restrictive. Many variations of the invention will become apparent to those skilled in the art upon review of this specification and the claims below. The full scope of the invention should be determined by reference to the claims, along with their full scope of equivalents, and the specification, along with such variations. FoleyHoagUS12882195.4

Claims

1. MTV-21725 CLAIMS We claim:

1. A method of hydrogen production, comprising: (a) providing a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane, wherein: the membrane is located between the catalytic chamber and the electrochemical chamber; the catalytic chamber comprises a catalyst layer; and the electrochemical chamber comprises a counter electrode and a molten electrolyte; (b) introducing a gaseous mixture comprising a hydrogen-containing compound to the catalytic chamber; (c) contacting the hydrogen-containing compound with the catalyst layer, thereby producing hydrogen atom equivalents (HAEs) and a dehydrogenated compound; (d) transferring the HAEs across the membrane; (e) applying an electrical potential difference between the membrane and the counter electrode, thereby oxidizing the HAEs to generate protons; (f) contacting the protons with the molten electrolyte, thereby generating protonated electrolyte anions; and (g) contacting the protonated electrolyte anions with the counter electrode, thereby reducing the protonated electrolyte anions and generating recovered hydrogen.

2. The method of claim 1, wherein the hydrogen-containing compound is selected from the group consisting of ammonia, hydrocarbon, and alcohol, or is a mixture thereof.

3. The method of claim 1 or 2, wherein the hydrogen-containing compound is ammonia.

4. The method of claim 1 or 2, wherein the hydrogen-containing compound is a hydrocarbon. FoleyHoagUS12882195.4 MTV-21725 5. The method of claim 2, wherein the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, methanol, ethanol, isopropanol, 2-butanol, cyclohexanol, and ethylbenzene.

6. The method of claim 5, wherein the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, ethanol, isopropanol, 2-butanol, cyclohexanol, and ethylbenzene.

7. The method of claim 5, wherein the hydrogen-containing compound is ethane.

8. The method of claim 1, wherein the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n-butene, isobutene, benzene, toluene, styrene, formaldehyde, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone.

9. The method of claim 1, wherein the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n-butene, isobutene, benzene, toluene, styrene, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone.

10. The method of claim 8, wherein the dehydrogenated compound is ethylene.

11. The method of claim 8, wherein the dehydrogenated compound is styrene.

12. The method of any one of claims 1-11, wherein the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% of the hydrogen-containing compound.

13. The method of claim 12, wherein the gaseous mixture consists of the hydrogen- containing compound.

14. The method of any one of claims 1-11, wherein the gaseous mixture comprises hydrogen. FoleyHoagUS12882195.4 MTV-21725 15. The method of claim 14, wherein the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% hydrogen.

16. The method of any one of claims 1-15, wherein the catalyst layer comprises a support and a catalyst disposed on the support.

17. The method of claim 16, wherein the support comprises carbon, stainless steel mesh, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate.

18. The method of claim 16, wherein the support comprises carbon, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate.

19. The method of claim 16, wherein the support comprises graphite felt.

20. The method of any one of claims 16-196, wherein the catalyst comprises ruthenium, cobalt, nickel, iron, gold, copper, zinc, platinum, palladium, chromium oxide, vanadium oxide, molybdenum oxide, gallium oxide, copper oxide, zinc oxide, iron oxide, carbon, transition metal nitride, transition metal carbide, alkali metal amides, or alkali metal imide, or a combination of any of them.

21. The method of claim 20, wherein the catalyst comprises iron carbide, cobalt carbide, nickel carbide, titanium carbide, vanadium carbide, manganese carbide, chromium carbide, iron nitride, cobalt nitride, nickel nitride, titanium nitride, vanadium nitride, manganese nitride, or chromium nitride, lithium amide, sodium amide, potassium amide, lithium imide, lithium calcium imide, or lithium magnesium imide, or a combination of any of them.

22. The method of claim 21, wherein the catalyst comprises ruthenium.

23. The method of claim 21, wherein the catalyst comprises platinum. FoleyHoagUS12882195.4 MTV-21725 24. The method of any one of claims 16-23, wherein the catalyst layer further comprises a promoter.

25. The method of claim 24, wherein the promoter comprises lithium, sodium, potassium, cesium, calcium, barium, tin, zinc, gallium, indium, or germanium, or a combination of any of them.

26. The method of claim 24, wherein the promoter comprises magnesium.

27. The method of claim 24, wherein the promoter comprises cesium.

28. The method of any one of claims 1-27, wherein the catalyst layer comprises a hydrogen dissociation catalyst.

29. The method of claim 28, wherein the hydrogen dissociation catalyst is selected from the group consisting of Pd, Pt, Rh, Ru, Ir, Au, Ag, Cu, Fe, Ni, Co, Re, V, Ta, Mo, or W, or a combination of any of them.

30. The method of any one of claims 1-29, wherein the catalyst layer comprises ruthenium and cesium.

31. The method of claim 24, wherein: the support comprises carbon nanotubes; the catalyst comprises ruthenium; and the promoter comprises cesium.

32. The method of any one of claims 1-31, wherein the molten electrolyte comprises an alkali metal hydroxide, alkali metal carbonate, alkali metal halide, alkaline-earth metal halide, alkali metal perchlorate, alkali metal nitrate, or alkali metal metaphosphate, or a eutectic mixture thereof. FoleyHoagUS12882195.4 MTV-21725 33. The method of claim 32, wherein the molten electrolyte comprises an alkali metal hydroxide.

34. The method of claim 32, wherein the molten electrolyte comprises a eutectic mixture of two or more alkali metal hydroxides.

35. The method of claim 32, wherein the molten electrolyte comprises a eutectic mixture of two or more electrolytes selected from alkali metal halide and alkaline-earth metal halide.

36. The method of any one of claims 32-35, wherein the molten electrolyte comprises KOH and NaOH.

37. The method of claim 35, wherein the molten electrolyte comprises MgCl2, KCl, and NaCl.

38. The method of any one of claims 1-37, wherein the molten electrolyte further comprises an inert metal oxide selected from the group consisting of Al2O3, ZrO2, HfO2, Y2O3, or a combination of any of them.

39. The method of any one of claims 1-38, wherein the molten electrolyte further comprises a solid proton conductor.

40. The method of claim 39, wherein the solid proton conductor comprises a proton- conducting metal oxide.

41. The method of claim 40, wherein the proton-conducting metal oxide is selected from the group consisting of SrZrO3, BaCeO3, BaZrO3, SrCeO3, or a combination of any of them.

42. The method of claim 40 or 41, wherein the proton-conducting metal oxide is doped with a dopant selected from the group consisting of Y, Sc, In, Gd, Sm, or a combination of any of them. FoleyHoagUS12882195.4 MTV-21725 43. The method of any one of claims 38-42, wherein the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the inert metal oxide.

44. The method of any one of claims 40-43, wherein the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the proton-conducting metal oxide.

45. The method of any one of claims 1-44, wherein the counter electrode comprises a hydrogen evolution catalyst.

46. The method of claim 45, wherein the hydrogen evolution catalyst comprises platinum, palladium, rhenium, iridium, rhodium, or nickel, or a combination of any of them.

47. The method of any one of claims 1-46, wherein the counter electrode comprises carbon, manganese, iron, cobalt, nickel, zinc, aluminum, or a combination of any of them.

48. The method of any one of claims 1-47, wherein the electrochemical chamber comprises an electrically insulating separator between the membrane and the counter electrode.

49. The method of claim 48, wherein the electrically insulating separator comprises alumina, magnesia, silica, chromite, zirconia, or calcium hexaluminate, or a mixture thereof.

50. The method of any one of claims 1-49, wherein the membrane comprises a metal selected from palladium, niobium, vanadium, tungsten, molybdenum, and tantalum, or a combination of any of them.

51. The method of any one of claims 1-49, wherein the membrane comprises an alloy comprising palladium, niobium, vanadium, tungsten, molybdenum, or tantalum, or a combination of any of them. FoleyHoagUS12882195.4 MTV-21725 52. The method of any one of claims 1-49, wherein the membrane comprises yttrium-doped BaCeO3, ytterbium-doped SrCeO3, or yttrium-doped BaZrO3, Gd-doped ceria, lanthanum tungstate, doped lanthanum tungstate, doped bismuth oxide, hydrated tungsten oxide, nickel oxide, or a combination of any of them.

53. The method of any one of claims 1-49, wherein the membrane comprises palladium or palladium alloy.

54. The method of claim 53, wherein the membrane comprises an alloy of palladium and silver.

55. The method of claim 53, wherein the membrane comprises an alloy of palladium and copper.

56. The method of any one of claims 1-55, wherein the molten electrolyte is maintained at a temperature of about 180 °C to about 1300 °C.

57. The method of claim 56, wherein the temperature is about 250 °C to about 500 °C.

58. The method of claim 56, wherein the temperature is about 300 °C to about 400 °C.

59. The method of any one of claim 1-58, further comprising h) providing a hydrogenation substrate; and i) reacting the hydrogenation substrate with the recovered hydrogen under conditions sufficient to hydrogenate the hydrogenation substrate.

60. The method of any one of claim 1-59, further comprising isolating the dehydrogenated compound.

61. A method of reducing a substrate, comprising: FoleyHoagUS12882195.4 MTV-21725 (a) providing a reactor comprising a catalytic chamber, an electrochemical chamber, and an H- conductive membrane, wherein: the membrane is located between the catalytic chamber and the electrochemical chamber; the catalytic chamber optionally comprises a catalyst layer; and the electrochemical chamber comprises a counter electrode and a molten electrolyte; (b) providing the substrate in the electrochemical chamber; (c) introducing to the catalytic chamber a gaseous mixture comprising hydrogen or a hydrogen- containing compound; (d) if the gaseous mixture comprises a hydrogen-containing compound, contacting the hydrogen- containing compound with the catalyst layer, thereby producing HAEs and a dehydrogenated compound; (e) if the gaseous mixture comprises hydrogen, contacting the hydrogen with the catalyst layer or the H-conductive membrane, thereby producing HAEs; (f) transferring the HAEs across the membrane; (g) applying an electrical potential difference between the membrane and the counter electrode, thereby oxidizing the HAEs to generate protons and placing the protons in contact with the molten electrolyte, thereby generating protonated electrolyte anions; and (h) contacting the counter electrode with the substrate and the protonated electrolyte anions, thereby generating a reduced substrate.

62. The method of claim 61, wherein the catalytic chamber comprises a catalyst layer.

63. The method of claim 62, wherein the catalyst layer comprises a support and a catalyst disposed on the support.

64. The method of claim 63, wherein the support comprises carbon, stainless steel mesh, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate.

65. The method of claim 63, wherein the support comprises carbon, silica, alumina, titania, ceria, zirconia, magnesia, or magnesium aluminate. FoleyHoagUS12882195.4 MTV-21725 66. The method of claim 63, wherein the support comprises graphite felt.

67. The method of any one of claims 63-66, wherein the catalyst comprises ruthenium, cobalt, nickel, iron, gold, copper, zinc, platinum, palladium, chromium oxide, vanadium oxide, molybdenum oxide, gallium oxide, copper oxide, zinc oxide, iron oxide, carbon, transition metal nitride, transition metal carbide, alkali metal amides, or alkali metal imide, or a combination of any of them.

68. The method of claim 67, wherein the catalyst comprises iron carbide, cobalt carbide, nickel carbide, titanium carbide, vanadium carbide, manganese carbide, chromium carbide, iron nitride, cobalt nitride, nickel nitride, titanium nitride, vanadium nitride, manganese nitride, or chromium nitride, lithium amide, sodium amide, potassium amide, lithium imide, lithium calcium imide, or lithium magnesium imide, or a combination of any of them.

69. The method of claim 67, wherein the catalyst comprises ruthenium.

70. The method of claim 67, wherein the catalyst comprises platinum.

71. The method of any one of claims 62-70, wherein the catalyst layer further comprises a promoter.

72. The method of claim 718, wherein the promoter comprises lithium, sodium, potassium, cesium, calcium, barium, tin, zinc, gallium, indium, or germanium, or a combination of any of them.

73. The method of claim 71, wherein the promoter comprises magnesium.

74. The method of claim 71, wherein the promoter comprises cesium.

75. The method of any one of claims 62-74, wherein the catalyst layer comprises a hydrogen dissociation catalyst. FoleyHoagUS12882195.4 MTV-21725 76. The method of claim 75, wherein the hydrogen dissociation catalyst is selected from the group consisting of Pd, Pt, Rh, Ru, Ir, Au, Ag, Cu, Fe, Ni, Co, Re, V, Ta, Mo, or W, or a combination of any of them.

77. The method of any one of claims 62-76, wherein the catalyst layer comprises ruthenium and cesium.

78. The method of claim 71, wherein: the support comprises carbon nanotubes; the catalyst comprises ruthenium; and the promoter comprises cesium.

79. The method of any one of claims 62-78, wherein the gaseous mixture comprises a hydrogen-containing compound and the hydrogen-containing compound is selected from the group consisting of ammonia, hydrocarbon, and alcohol, or is a mixture thereof.

80. The method of claim 79, wherein the hydrogen-containing compound is ammonia.

81. The method of claim 79, wherein the hydrogen-containing compound is a hydrocarbon.

82. The method of claim 81, wherein the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, methanol, ethanol, isopropanol, 2-butanol, cyclohexanol, and ethylbenzene.

83. The method of claim 81, wherein the hydrogen-containing compound is selected from the group consisting of ethane, propane, n-butane, iso-butane, cyclohexane, methylcyclohexane, ethanol, isopropanol, 2-butanol, cyclohexanol, and ethylbenzene.

84. The method of claim 81, wherein the hydrogen-containing compound is ethane. - 77 - FoleyHoagUS12882195.4 MTV-21725 85. The method of any one of claims 61-84, wherein the gaseous mixture comprises from about 0.01 vol.% to about 100 vol.% of the hydrogen-containing compound.

86. The method of claim 85, wherein the gaseous mixture consists of the hydrogen- containing compound.

87. The method of any one of claims 61-78, wherein the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n-butene, isobutene, benzene, toluene, styrene, formaldehyde, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone.

88. The method of any one of claims 61-78, wherein the dehydrogenated compound is selected from the group consisting of ethylene, propylene, n-butene, isobutene, benzene, toluene, styrene, acetaldehyde, acetone, methyl ethyl ketone, and cyclohexanone.

89. The method of claim 88, wherein the dehydrogenated compound is ethylene.

90. The method of claim 88, wherein the dehydrogenated compound is styrene.

91. The method of any one of claim 61-90, further comprising isolating the dehydrogenated compound.

92. The method of any one of claims 61-91, wherein the gaseous mixture comprises hydrogen.

93. The method of claim 92, wherein the gaseous mixture comprises about 0.01 vol.% to about 100 vol.% hydrogen.

94. The method of any one of claims 61-93, wherein the molten electrolyte comprises an alkali metal hydroxide, alkali metal carbonate, alkali metal halide, alkaline-earth metal halide, alkali metal perchlorate, alkali metal nitrate, or alkali metal metaphosphate, or a eutectic mixture thereof. FoleyHoagUS12882195.4 MTV-21725 95. The method of claim 94, wherein the molten electrolyte comprises an alkali metal hydroxide.

96. The method of claim 94, wherein the molten electrolyte comprises a eutectic mixture of two or more alkali metal hydroxides.

97. The method of claim 94, wherein the molten electrolyte comprises a eutectic mixture of two or more electrolytes selected from alkali metal halide and alkaline-earth metal halide.

98. The method of any one of claims 61-96, wherein the molten electrolyte comprises KOH and NaOH.

99. The method of claim 94 or 97, wherein the molten electrolyte comprises MgCl2, KCl, and NaCl.

100. The method of any one of claims 61-99, wherein the molten electrolyte further comprises an inert metal oxide selected from the group consisting of Al2O3, ZrO2, HfO2, Y2O3, or a combination of any of them.

101. The method of any one of claims 61-100, wherein the molten electrolyte further comprises a solid proton conductor.

102. The method of claim 101, wherein the solid proton conductor comprises a proton- conducting metal oxide.

103. The method of claim 102, wherein the proton-conducting metal oxide is selected from the group consisting of SrZrO3, BaCeO3, BaZrO3, SrCeO3, or a combination of any of them. FoleyHoagUS12882195.4 MTV-21725 104. The method of claim 101 or 102, wherein the proton-conducting metal oxide is doped with a dopant selected from the group consisting of Y, Sc, In, Gd, Sm, or a combination of any of them.

105. The method of any one of claims 100-104, wherein the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the inert metal oxide.

106. The method of any one of claims 102-105, wherein the molten electrolyte comprises about 0.1 mol% to about 90 mol% of the proton-conducting metal oxide.

107. The method of any one of claims 61-106, wherein the counter electrode comprises a hydrogen evolution catalyst.

108. The method of claim 107, wherein the hydrogen evolution catalyst comprises platinum, palladium, rhenium, iridium, rhodium, or nickel, or a combination of any of them.

109. The method of any one of claims 61-108, wherein the counter electrode comprises carbon, manganese, iron, cobalt, nickel, zinc, or aluminum, or a combination of any of them.

110. The method of any one of claims 61-109, wherein the electrochemical chamber an electrically insulating separator between the membrane and counter electrode.

111. The method of claim 110, wherein the electrically insulating separator comprises alumina, magnesia, silica, chromite, zirconia, or calcium hexaluminate, or a mixture thereof.

112. The method of any one of claims 61-111, wherein the membrane comprises a metal selected from palladium, niobium, vanadium, tungsten, molybdenum, and tantalum, or a combination of any of them. FoleyHoagUS12882195.4 MTV-21725 113. The method of any one of claims 61-112, wherein the membrane comprises an alloy comprising palladium, niobium, vanadium, tungsten, molybdenum, or tantalum, or a combination of any of them.

114. The method of any one of claims 61-112, wherein the membrane comprises yttrium- doped BaCeO3, ytterbium-doped SrCeO3, or yttrium-doped BaZrO3, Gd-doped ceria, lanthanum tungstate, doped lanthanum tungstate, doped bismuth oxide, hydrated tungsten oxide, nickel oxide, or a combination of any of them.

115. The method of any one of claims 61-112, wherein the membrane comprises palladium or palladium alloy.

116. The method of claim 115, wherein the membrane comprises an alloy of palladium and silver.

117. The method of claim 115, wherein the membrane comprises an alloy of palladium and copper.

118. The method of any one of claims 61-117, wherein the molten electrolyte is maintained at a temperature of about 180 °C to about 1300 °C.

119. The method of claim 118, wherein the temperature is about 250 °C to about 500 °C.

120. The method of claim 118, wherein the temperature is about 300 °C to about 400 °C.

121. The method of any one of claims 61-120, wherein the substrate and the molten electrolyte form an admixture.

122. The method of any one of claims 61-120, wherein the substrate is dissolved in the molten electrolyte. FoleyHoagUS12882195.4 MTV-21725 123. The method of any one of claims 61-122, wherein the substrate is a metal oxide.

124. The method of claim 123, wherein the metal oxide comprises manganese oxide, iron oxide, cobalt oxide, nickel oxide, zinc oxide, or aluminum oxide, or a combination of any of them.

125. The method of any one of claims 61-122, wherein the substrate comprises an oxide of a main group element.

126. The method of claim 125, wherein the substrate comprises phosphorus oxide, phosphate, metaphosphate, silicate, silica, tin oxide, indium oxide, or gallium oxide, or a combination of any of them.

127. The method of any one of claims 61-124, wherein the reduced substrate comprises an elemental metal.

128. The method of any one of claims 61-121, wherein the reduced substrate comprises an elemental main group element.

129. The method of claim 128, wherein the reduced substrate comprises elemental phosphorus, silicon, tin, indium, gallium, manganese, iron, cobalt, nickel, zinc, or aluminum, or a combination of any of them. FoleyHoagUS12882195.4

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