Intermediate temperature steam electrolysis in a molten salt electrolyte

Abstract

Disclosed is an electrolyzer, comprising: a cathode, comprising a cathode catalyst and a cathode separator; an anode, comprising an anode catalyst and an anode separator; a cathode flow field, comprising an inlet and an outlet; wherein the cathode flow field is in contact with the cathode; an anode flow field, comprising an inlet and an outlet; wherein the anode flow field is in contact with the anode; and an electrolyte wherein the cathode separator and the anode separator each independently comprise a porous hydrophobic material. Also disclosed are methods of producing H2 and O2 using the electrolyzer.

Description

[0001] MTV-24525

[0002] INTERMEDIATE TEMPERATURE STEAM ELECTROLYSIS INA MOLTEN SALT ELECTROLYTE

[0003] RELATED APPLICATION

[0004] This application claims the benefit of priority to U.S. Provisional Patent Application serial number 63 / 749,148, filed January 24, 2025.

[0005] BACKGROUND

[0006] Hydrogen can serve as a clean energy intermediate, linking renewable power generation to other energy sectors, including industry and transportation. Green hydrogen can be used both as a fuel and as a starting material for industrial chemical synthesis to reduce carbon emissions. Accordingly, efficient and clean methods of producing hydrogen are needed.

[0007] SUMMARY OF THE INVENTION

[0008] In some embodiments, the present disclosure relates to an electrolyzer, comprising: a cathode, comprising a cathode catalyst and a cathode separator;

[0009] an anode, comprising an anode catalyst and an anode separator;

[0010] a cathode flow field, comprising an inlet and an outlet; wherein the cathode flow field is in contact with the cathode;

[0011] an anode flow field, comprising an inlet and an outlet; wherein the anode flow field is in contact with the anode; and

[0012] an electrolyte,

[0013] wherein the cathode separator and the anode separator each independently comprises a porous hydrophobic material.

[0014] In some embodiments, the present disclosure relates to a method of producing H2 and O2 from steam, comprising:

[0015] a) supplying steam to the inlet of the cathode flow field of the electrolyzer of the disclosure;

[0016] b) applying an electrical potential difference across the cathode and the anode of the electrolyzer;

[0017] c) collecting H2 through the outlet of the cathode flow field; andMTV-24525

[0018] d) collecting O2 through the outlet of the anode flow field.

[0019] BRIEF DESCRIPTION OF THE DRAWINGS

[0020] FIG. 1 is a schematic representation of a cell configuration with a hydrophobic layer and catalyst in the cathode and anode included as separate components.

[0021] FIG. 2 is a schematic representation of a cell configuration with a hydrophobic layer in the cathode and anode deposited directly on the catalyst.

[0022] FIG. 3 is a plot showing the current with a 2.2V applied cell voltage with a cell configuration as specified in Example 1 and FIG. 1.

[0023] FIG. 4 is a plot showing the current under potentiostatic polarization.

[0024] FIG. 5 is a chromatograph of the anode stream showing less than 0.03% H2 in the output stream (H2 peak shown in a box).

[0025] FIG. 6 is a plot showing galvanostatic polarization running at currents between 50mA and 400mA in a system described in Example 3.

[0026] DETAILED DESCRIPTION OF THE INVENTION

[0027] Commercial water electrolyzer technologies can be divided into two categories: proton exchange membrane (PEM) electrolyzers and alkaline electrolyzers. At a fundamental level, the two systems differ by the ion transporting charge in the electrolyte. In PEM electrolyzers, water is oxidized to form oxygen gas and protons, which are transported through an fluoro-polymer membrane to the cathode where they are reduced to H2. In contrast, alkaline electrolyzers employ the opposite approach: hydrogen evolution (HER) occurs at the cathode with water as a proton donor. The produced hydroxide ions then carry the ionic current to the anode, where they are oxidized to form O2.

[0028] Existing electrolyzer technologies all suffer from critical tradeoffs that impede their widespread use for deep decarbonization. PEM electrolyzers are capable of operating at high current densities and can be ramped up and down rapidly in response to variable renewable powerMTV-24525

[0029] supply. However, they require specialty membranes (Nafion) and expensive iridium- and platinum-based catalysts that dramatically increase the capital cost of the electrolyzer. Additionally, resource limitations on iridium cap the ultimate scale of deployment of PEM to a small fraction of the massive 550 GW capacity required by 2030 (water electrolyzer capacity was 11 GW in 2022).

[0030] In contrast, alkaline electrolyzers employ low-cost components and use entirely earth-abundant catalysts (e.g. steel, nickel). Thus, alkaline electrolyzers have lower capital costs and do not suffer from supply chain constraints on scaling. However, alkaline electrolyzers operate at lower current densities and cannot be cycled up and down to follow variable renewable electricity supply. The current regulatory landscape in the US makes this latter deficiency particularly problematic. To qualify for credits under the Inflation Reduction Act after 2028, the electricity used in a hydrogen production facility must have been generated in the same hour that it is used. This temporal matching requirement emphasizes the need for technologies that use low-cost materials while enabling dynamic operation.

[0031] Alkaline electrolyzers are unable to operate dynamically due to two pernicious problems: (1) reverse currents and (2) gas crossover. The first problem stems from the fact that alkaline electrolyzers operate with flowing concentrated KOH electrolyte. Thus, during system turndown, the electrolyte provides a short-circuiting pathway for reverse current flow between the anode and cathode on either side of each bipolar electrode. This causes larges changes in the redox state of each catalyst that leads to catastrophic failure of the device. The second problem, gas crossover, stems from the finite solubility of H2 and O2 in the electrolyte which leads to a constant crossover flux of gases between the electrodes. During system turndown, the rate of O2 and H2 production is reduced, but the crossover flux remains constant leading to gas mixtures that can approach or exceed the 2% H2 in O2 explosive limit. Both fundamental challenges make alkaline water electrolysis ill-suited to dynamic operation with intermittent renewable energy sources like wind and solar.

[0032] In some embodiments, the present disclosure relates to intermediate temperature steam electrolyzer that employs a molten hydroxide electrolyte. In some embodiments, the disclosed system does not require precious metal catalysts and can avoid using costly membrane components required in PEM electrolyzers. By flowing steam rather than caustic KOH, the system overcomes the reverse current problem, and the lower gas solubility in a molten electrolyte mitigates gasMTV-24525

[0033] crossover. These intrinsic advantages serve to marry the key advantages of PEM and alkaline systems.

[0034] DEFINITIONS

[0035] 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. As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] EXEMPLARY EMBODIMENTS

[0041] In some embodiments, the present disclosure is related to an electrolyzer, comprising: a cathode, comprising a cathode catalyst and a cathode separator;

[0042] an anode, comprising an anode catalyst and an anode separator;MTV-24525

[0043] a cathode flow field, comprising an inlet and an outlet; wherein the cathode flow field is in contact with the cathode;

[0044] an anode flow field, comprising an inlet and an outlet; wherein the anode flow field is in contact with the anode; and

[0045] an electrolyte,

[0046] wherein the cathode separator and the anode separator each independently comprises a porous hydrophobic material.

[0047] In some embodiments, the cathode further comprises a first layer and a second layer wherein

[0048] the first layer is in contact with the second layer;

[0049] the first layer comprises the cathode catalyst;

[0050] the second layer comprises the cathode separator;

[0051] the first layer is in contact with the electrolyte; and

[0052] the second layer is in contact with the cathode flow field.

[0053] In some embodiments, the first layer is disposed on the second layer.

[0054] In some embodiments, the thickness of the second layer is about 0.001 cm to about 0.1 cm. In some embodiments, the thickness of the second layer is about 0.001 cm to about 0.1 cm, about 0.005 cm to about 0.1 cm, about 0.01 cm to about 0.1 cm, about 0.05 cm to about 0.1 cm, about 0.001 cm to about 0.05 cm, about 0.005 cm to about 0.05 cm, about 0.01 cm to about 0.05 cm, about 0.001 cm to about 0.01 cm, or about 0.005 cm to about 0.01 cm. In some embodiments, the thickness of the second layer is about 0.01 cm to about 0.05 cm.

[0055] In some embodiments, the anode further comprises a third layer and a fourth layer, wherein

[0056] the third layer is in contact with the fourth layer;

[0057] the third layer comprises the anode catalyst;

[0058] the fourth layer comprises the anode separator;

[0059] the third layer is in contact with the electrolyte; and

[0060] the fourth layer is in contact with the anode flow field.

[0061] In some embodiments, the third layer is disposed on the fourth layer.

[0062] In some embodiments, the thickness of the fourth layer is about 0.001 cm to about 0.1 cm. In some embodiments, the thickness of the fourth layer is about 0.001 cm to about 0.1 cm,MTV-24525

[0063] about 0.005 cm to about 0.1 cm, about 0.01 cm to about 0.1 cm, about 0.05 cm to about 0.1 cm, about 0.001 cm to about 0.05 cm, about 0.005 cm to about 0.05 cm, about 0.01 cm to about 0.05 cm, about 0.001 cm to about 0.01 cm, or about 0.005 cm to about 0.01 cm. In some embodiments, the thickness of the fourth layer is about 0.01 cm to about 0.05 cm.

[0064] In some embodiments, the cathode separator is in a form of cathode separator particles; the cathode separator particles are in contact with the cathode catalyst; and

[0065] the cathode separator particles are in contact with the cathode flow field.

[0066] In some embodiments the cathode separator particles are disposed on the cathode catalyst. In some embodiments, the cathode separator particles form an admixture with the cathode catalyst.

[0067] In some embodiments, the anode separator is in a form of anode separator particles; the anode separator particles are in contact with the anode catalyst; and

[0068] the anode separator particles are in contact with the anode flow field.

[0069] In some embodiments the anode separator particles are disposed on the anode catalyst. In some embodiments, the anode separator particles form an admixture with the anode catalyst.

[0070] In some embodiments, the porous hydrophobic material is independently selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PF A), fluorinated ethylene propylene (FEP), polyvinyl fluoride (PVF), and polyvinylidene fluoride (PVDF), or a combination of any of them.

[0071] In some embodiments, the porous hydrophobic material is PTFE.

[0072] In some embodiments, the porous hydrophobic material is PF A.

[0073] In some embodiments, the porous hydrophobic material is FEP.

[0074] In some embodiments, the porous hydrophobic material is PVF.

[0075] In some embodiments, the porous hydrophobic material is PVDF.

[0076] In some embodiments, the electrolyte is a molten electrolyte. In some embodiments, the molten electrolyte has a melting temperature of about 140° C to about 300° C. In some embodiments, the molten electrolyte has a melting temperature of about 150° C to about 300° C, about 160° C to about 300° C, about 170° C to about 300° C, about 180° C to about 300° C, about 190° C to about 300° C, about 200° C to about 300° C, about 220° C to about 300° C, about 240° C to about 300° C, about 260° C to about 300° C, about 280° C to about 300° C, about 140° C to about 280° C, about 150° C to about 280° C, about 160° C to about 280° C,MTV-24525

[0077] about 170° C to about 280° C, about 180° C to about 280° C, about 190° C to about 280° C, about 200° C to about 280° C, about 220° C to about 280° C, about 240° C to about 280° C, about 260° C to about 280° C, about 140° C to about 260° C, about 150° C to about 260° C, about 160° C to about 260° C, about 170° C to about 260° C, about 180° C to about 260° C, about 190° C to about 260° C, about 200° C to about 260° C, about 220° C to about 260° C, about 240° C to about 260° C, about 140° C to about 240° C, about 150° C to about 240° C, about 160° C to about 240° C, about 170° C to about 240° C, about 180° C to about 240° C, about 190° C to about 240° C, about 200° C to about 240° C, about 220° C to about 240° C, about 140° C to about 220° C, about 150° C to about 220° C, about 160° C to about 220° C, about 170° C to about 220° C, about 180° C to about 220° C, about 190° C to about 220° C, about 200° C to about 220° C, about 140° C to about 200° C, about 150° C to about 200° C, about 160° C to about 200° C, about 170° C to about 200° C, about 180° C to about 200° C, about 190° C to about 200° C, about 140° C to about 180° C, about 150° C to about 180° C, about 160° C to about 180° C, about 170° C to about 180° C, about 140° C to about 160° C, or about 150° C to about 160° C. In some embodiments, the molten electrolyte has a melting temperature of about 140° C, about 150° C, about 160° C, about 170° C, about 180° C, about 190° C, about 200° C, about 210° C, about 220° C, about 230° C, about 240° C, about 250° C, about 260° C, about 270° C, about 280° C, about 290° C, or about 300° C.

[0078] 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.

[0079] In some embodiments, the molten electrolyte comprises a eutectic mixture of two or more alkali metal hydroxides selected from LiOH, NaOH, KOH, CsOH, Ca(OH)2, Mg(0H)2, and Ba(OH)2. In some embodiments, the molten electrolyte comprises KOH. In some embodiments, the molten electrolyte comprises NaOH. In some embodiments, the molten electrolyte comprises KOH and NaOH.

[0080] In some embodiments, the molten electrolyte comprises a eutectic mixture of two or more electrolytes selected from alkali metal halides and alkaline-earth metal halides. In some embodiments, the molten electrolyte comprises MgCL, KC1, and NaCl.MTV-24525

[0081] In some embodiments, the electrolyte further comprises ceramic material.

[0082] In some embodiments, the ceramic material is in the form of particles, fibers, felt, or a combination of any of them.

[0083] In some embodiments, the ceramic material is selected from the group consisting of ZrO2 , LiAlCh , yttria-stabilized zirconia, AI2O3 , HfCL, TiCh , and MgO, or a combination of any of them.

[0084] In some embodiments, the electrolyte comprises ceramic particles. In some embodiments, the ceramic particles are selected from the group consisting of ZrCh particles, Li AIO2 particles, yttria-stabilized zirconia particles, AI2O3 particles, TiCh particles, and MgO particles, or a combination of any of them. In some embodiments, the ceramic particles comprise

[0085] ZrO2 particles. In some embodiments, the ceramic material comprises HfO2 felt. In some embodiments, the ceramic material comprises HfO2 fibers.

[0086] In some embodiments, the diameter of the ceramic particles is about 0.1 pm to about 20 pm. In some embodiments, the diameter of the ceramic particles is about 0.5 pm to about 20 pm, about 1 pm to about 20 pm, about 2 pm to about 20 pm, about 3 pm to about 20 pm, about 5 pm to about 20 pm, about 8 pm to about 20 pm, about 10 pm to about 20 pm, about 12 pm to about 20 pm, about 15 pm to about 20 pm, about 0.1 pm to about 10 pm, about 1 pm to about 10 pm, about 2 pm to about 10 pm, about 3 pm to about 10 pm, about 5 pm to about 10 pm, or about 8 pm to about 10 pm. In some embodiments, the diameter of the ceramic particles is about 0.1 pm, about 1 pm, about 2 pm, about 3 pm, about 4 pm, about 5 pm, about 6 pm, about 7 pm, about 8 pm, about 9 pm, about 10 pm, about 12 pm, about 14 pm, about 16 pm, about 18 pm, or about 20 pm. In some embodiments, the diameter of the ceramic particles is about 3 pm to about 10 pm.

[0087] In some embodiments, the electrolyte comprises about 1 wt% to about 80 wt% ceramic material. In some embodiments, the electrolyte comprises about 30 wt% to about 60 wt% ceramic material. In some embodiments, the electrolyte comprises about 5 wt% to about 80 wt%, 10 wt% to about 80 wt%, 20 wt% to about 80 wt%, 30 wt% to about 80 wt%, 40 wt% to about 80 wt%, 50 wt% to about 80 wt%, 60 wt% to about 80 wt%, 70 wt% to about 80 wt%, 1 wt% to about 60 wt%, 5 wt% to about 60 wt%, 10 wt% to about 60 wt%, 20 wt% to about 60 wt%, 30 wt% to about 60 wt%, 40 wt% to about 60 wt%, 50 wt% to about 60 wt%, 1 wt% to about 40 wt%, 5 wt% to about 40 wt%, 10 wt% to about 40 wt%, 20 wt% to about 40 wt%, 30 wt% toMTV-24525

[0088] about 40 wt%, 1 wt% to about 20 wt%, 5 wt% to about 20 wt%, or 10 wt% to about 20 wt% ceramic material. In some embodiments, the electrolyte comprises about 1 wt%, about 5 wt%, about 10 wt%, about 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, about 60 wt%, about 70 wt%, or about 80 wt% ceramic material.

[0089] In some embodiments, the electrolyte comprises about 1 wt% to about 80 wt% ceramic particles. In some embodiments, the electrolyte comprises about 5 wt% to about 80 wt%, 10 wt% to about 80 wt%, 20 wt% to about 80 wt%, 30 wt% to about 80 wt%, 40 wt% to about 80 wt%, 50 wt% to about 80 wt%, 60 wt% to about 80 wt%, 70 wt% to about 80 wt%, 1 wt% to about 60 wt%, 5 wt% to about 60 wt%, 10 wt% to about 60 wt%, 20 wt% to about 60 wt%, 30 wt% to about 60 wt%, 40 wt% to about 60 wt%, 50 wt% to about 60 wt%, 1 wt% to about 40 wt%, 5 wt% to about 40 wt%, 10 wt% to about 40 wt%, 20 wt% to about 40 wt%, 30 wt% to about 40 wt%, 1 wt% to about 20 wt%, 5 wt% to about 20 wt%, or 10 wt% to about 20 wt% ceramic particles. In some embodiments, the electrolyte comprises about 1 wt%, about 5 wt%, about 10 wt%, about 20 wt%, about 30 wt%, about 40 wt%, about 50 wt%, about 60 wt%, about 70 wt%, or about 80 wt% ceramic particles. In some embodiments, the electrolyte comprises about 30 wt% to about 60 wt% ceramic particles.

[0090] In some embodiments, the electrolyte further comprises water. In some embodiments, the electrolyte further comprises about 0 wt% to about 30 wt% water. In some embodiments, the electrolyte further comprises about 1 wt% to about 30 wt%, about 5 wt% to about 30 wt%, about 10 wt% to about 30 wt%, about 15 wt% to about 30 wt%, about 20 wt% to about 30 wt%, about 25 wt% to about 30 wt%, about 0 wt% to about 20 wt%, about 1 wt% to about 20 wt%, about 5 wt% to about 20 wt%, about 10 wt% to about 20 wt%, about 15 wt% to about 20 wt%, about 0 wt% to about 10 wt%, about 1 wt% to about 10 wt%, about 5 wt% to about 10 wt%, about 0 wt% to about 5 wt%, or about 1 wt% to about 5 wt% water. In some embodiments, the electrolyte further comprises about 0 wt%, 1 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, or 30 wt% water.

[0091] In some embodiments, the cathode catalyst comprises Ni, Fe, Co, Mn, Cr, Pt, Pd, Rh, Ir, Ag, Cu, or Au, or a combination of any of them. In some embodiments, the cathode catalyst comprises compressed Ni foam.MTV-24525

[0092] In some embodiments, the anode catalyst comprises Ni, Fe, Ni, Fe, Co, Mn, Cr, Pt, Pd, Rh, Ir, Ag, Cu, or Au, or a combination of any of them. In some embodiments, the anode catalyst comprises compressed Ni foam.

[0093] In some embodiments, the electrolyzer further comprises a cathode current collector, wherein the cathode current collector is in contact with the cathode catalyst or the cathode flow field. In some embodiments, the cathode current collector is in contact with the cathode catalyst. In some embodiments, the cathode current collector is in contact with the cathode flow field.

[0094] In some embodiments, the electrolyzer further comprises an anode current collector, wherein the anode current collector is in contact with the anode catalyst or the anode flow field. In some embodiments, the anode current collector is in contact with the anode catalyst. In some embodiments, the anode current collector is in contact with the anode flow field.

[0095] In some embodiments the present disclosure relates to a method of producing H2 and O2 from steam, comprising:

[0096] a) supplying steam to the inlet of the cathode flow field of the electrolyzer disclosed herein;

[0097] b) applying an electrical potential difference across the cathode and the anode of the electrolyzer;

[0098] c) collecting H2 through the outlet of the cathode flow field; and

[0099] d) collecting O2 through the outlet of the anode flow field.

[0100] In some embodiments, molten electrolyte is maintained at a temperature of about 140 °C to about 300 °C. In some embodiments, the molten electrolyte is maintained at a temperature of about 150° C to about 300° C, about 160° C to about 300° C, about 170° C to about 300° C, about 180° C to about 300° C, about 190° C to about 300° C, about 200° C to about 300° C, about 220° C to about 300° C, about 240° C to about 300° C, about 260° C to about 300° C, about 280° C to about 300° C, about 140° C to about 280° C, about 150° C to about 280° C, about 160° C to about 280° C, about 170° C to about 280° C, about 180° C to about 280° C, about 190° C to about 280° C, about 200° C to about 280° C, about 220° C to about 280° C, about 240° C to about 280° C, about 260° C to about 280° C, about 140° C to about 260° C, about 150° C to about 260° C, about 160° C to about 260° C, about 170° C to about 260° C, about 180° C to about 260° C, about 190° C to about 260° C, about 200° C to about 260° C, about 220° C to about 260° C, about 240° C to about 260° C, about 140° C to about 240° C,MTV-24525

[0101] about 150° C to about 240° C, about 160° C to about 240° C, about 170° C to about 240° C, about 180° C to about 240° C, about 190° C to about 240° C, about 200° C to about 240° C, about 220° C to about 240° C, about 140° C to about 220° C, about 150° C to about 220° C, about 160° C to about 220° C, about 170° C to about 220° C, about 180° C to about 220° C, about 190° C to about 220° C, about 200° C to about 220° C, about 140° C to about 200° C, about 150° C to about 200° C, about 160° C to about 200° C, about 170° C to about 200° C, about 180° C to about 200° C, about 190° C to about 200° C, about 140° C to about 180° C, about 150° C to about 180° C, about 160° C to about 180° C, about 170° C to about 180° C, about 140° C to about 160° C, or about 150° C to about 160° C. In some embodiments, the molten electrolyte is maintained at a temperature of about 140° C, about 150° C, about 160° C, about 170° C, about 180° C, about 190° C, about 200° C, about 210° C, about 220° C, about 230° C, about 240° C, about 250° C, about 260° C, about 270° C, about 280° C, about 290° C, or about 300° C. In some embodiments, the temperature is about 140 °C to about 250 °C. In some embodiments, the temperature is about 200 °C to about 230 °C.

[0102] In some embodiments, steam is supplied at a temperature of about 140 °C to about 300 °C. In some embodiments, steam is supplied at a temperature of about 150° C to about 300° C, about 160° C to about 300° C, about 170° C to about 300° C, about 180° C to about 300° C, about 190° C to about 300° C, about 200° C to about 300° C, about 220° C to about 300° C, about 240° C to about 300° C, about 260° C to about 300° C, about 280° C to about 300° C, about 140° C to about 280° C, about 150° C to about 280° C, about 160° C to about 280° C, about 170° C to about 280° C, about 180° C to about 280° C, about 190° C to about 280° C, about 200° C to about 280° C, about 220° C to about 280° C, about 240° C to about 280° C, about 260° C to about 280° C, about 140° C to about 260° C, about 150° C to about 260° C, about 160° C to about 260° C, about 170° C to about 260° C, about 180° C to about 260° C, about 190° C to about 260° C, about 200° C to about 260° C, about 220° C to about 260° C, about 240° C to about 260° C, about 140° C to about 240° C, about 150° C to about 240° C, about 160° C to about 240° C, about 170° C to about 240° C, about 180° C to about 240° C, about 190° C to about 240° C, about 200° C to about 240° C, about 220° C to about 240° C, about 140° C to about 220° C, about 150° C to about 220° C, about 160° C to about 220° C, about 170° C to about 220° C, about 180° C to about 220° C, about 190° C to about 220° C, about 200° C to about 220° C, about 140° C to about 200° C, about 150° C to about 200° C,MTV-24525

[0103] about 160° C to about 200° C, about 170° C to about 200° C, about 180° C to about 200° C, about 190° C to about 200° C, about 140° C to about 180° C, about 150° C to about 180° C, about 160° C to about 180° C, about 170° C to about 180° C, about 140° C to about 160° C, or about 150° C to about 160° C. In some embodiments, steam is supplied at a temperature of about 140° C, about 150° C, about 160° C, about 170° C, about 180° C, about 190° C, about 200° C, about 210° C, about 220° C, about 230° C, about 240° C, about 250° C, about 260° C, about 270° C, about 280° C, about 290° C, or about 300° C. In some embodiments, steam is supplied at a temperature of about 140 °C to about 250 °C.

[0104] In some embodiments, steam is supplied at a pressure of about 6 psi to about 200 psi. In some embodiments, steam is supplied at a pressure of about 10 psi to about 200 psi, about 20 psi to about 200 psi, about 40 psi to about 200 psi, about 60 psi to about 200 psi, about 80 psi to about 200 psi, about 100 psi to about 200 psi, about 120 psi to about 200 psi, about 140 psi to about 200 psi, about 160 psi to about 200 psi, about 180 psi to about 200 psi, 10 psi to about 150 psi, about 20 psi to about 150 psi, about 40 psi to about 150 psi, about 60 psi to about 150 psi, about 80 psi to about 150 psi, about 100 psi to about 150 psi, about 120 psi to about 150 psi, about 140 psi to about 150 psi, 10 psi to about 100 psi, about 20 psi to about 100 psi, about 40 psi to about 100 psi, about 60 psi to about 100 psi, about 80 psi to about 100 psi, about 10 psi to about 50 psi, about 20 psi to about 50 psi, about 30 psi to about 50 psi, or about 40 psi to about 50 psi. In some embodiments, steam is supplied at a pressure of about 6 psi, about 6 psi, about 10 psi, about 20 psi, about 30 psi, about 40 psi, about 50 psi, about 60 psi, about 70 psi, about 80 psi, about 90 psi, about 100 psi, about 110 psi, about 120 psi, about 130 psi, about 140 psi, about 150 psi, about 160 psi, about 170 psi, 180 psi, about 190 psi, or about 200 psi.

[0105] 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.MTV-24525

[0106] EXAMPLES

[0107] Example 1: Generation of H2 in a cell depicted in FIG. 1

[0108] As shown in FIG. 1, the cell was constructed by stacking components between two custom Inconel flow blocks. Each flow block was equipped with ports for gas introduction and gas release and a flow field. A porous polytetrafluorethylene membrane (0.01” thickness) was then stacked to separate the flow fields from the rest of the cell. Catalyst in the form of compressed Ni foam was then added with a Ni foil current collector flag. Between the cathode and anode, a gasket made with expanded PTFE (1 / 16” thickness) was stacked. A hole was cut in the gasket and filled with 5:4 hydroxide eutectic: zirconia powder. The hydroxide eutectic was comprised of 1:1 mol: mol sodium hydroxide and potassium hydroxide. Zirconia powder had 6 pm particle size. A total of 2 g of this mixture was mixed with ~2 mL water to form a concentrated slurry and sealed in the cell. The symmetric construction was then secured with stainless steel screws and nuts with insulating jackets used to ensure no electrical contact between flow fields.

[0109] The cell was heated in an oven to 220 °C overnight with steam and argon flowing to the cathode and argon flowing to the anode. Excess water in the electrolyte was expected to evaporate during this time. The oven temperature was then increased to 230 °C and allowed to equilibrate for 30 minutes prior to performing electrochemical measurements.

[0110] Potentiostatic polarization yielded steady current, punctuated by spikes due to bubble release, on the timescale of hours. One representative trace under potentiostatic polarization is shown in FIG. 3. Galvanostatic polarization led to stable or declining cell voltages over time. One representative trace under potentiostatic polarization is shown in FIG. 4. Additionally, faradaic efficiency and gas crossover were probed periodically during the measurement. Gas chromatography analysis of the cathode stream showed 90% faradaic efficiency for H2. Gas chromatography of the anode stream showed less than 0.03% H2 in the output stream (FIG. 5).

[0111] Example 2: Generation of H2 in a cell depicted in FIG.2

[0112] As shown in FIG.2, the cell is constructed by stacking components between two custom Inconel flow blocks. Each flow block is equipped with ports for gas introduction and gas release and a flow field. A compressed Ni foam catalyst with a gas transporting layer composed of Ni nanoparticles and polytetrafluoroethylene nanoparticles deposited on one side is then stackedMTV-24525

[0113] with the gas transporting layer facing the flow block. Between the cathode and anode, a gasket made with expanded PTFE (1 / 16” thickness) is stacked. A hole is cut in the gasket and filled with 5:4 hydroxide eutectic: zirconia powder. The hydroxide eutectic is comprised of 1:1 mol: mol sodium hydroxide and potassium hydroxide. Zirconia powder has 6 pm particle size. A total of 2 g of this mixture is mixed with ~1 mL water to form a concentrated slurry and sealed in the cell. The symmetric construction is then secured with stainless steel screws and nuts with insulating jackets to ensure no electrical contact between flow fields.

[0114] The cell is heated in an oven to 220 °C overnight with steam and argon flowing to the cathode and argon flowing to the anode. Excess water in the electrolyte is expected to evaporate during this time. The oven temperature is increased to 230 °C and allowed to equilibrate for 30 minutes prior to performing electrochemical measurements.

[0115] Example 3: Generation of Hi using Hafnia felt electrolyte

[0116] The cell was constructed by stacking components between two custom Inconel flow blocks. Each flow block was equipped with ports for gas introduction and gas release and a flow field. A porous polytetrafluorethylene membrane (0.01” thickness) was then stacked to separate the flow fields from the rest of the cell. Catalyst in the form of compressed Ni foam was then added with a Ni foil current collector flag. Between the cathode and anode, a gasket made with expanded PTFE (1 / 16” thickness) was stacked. A hole was cut in the gasket and a hydroxide impregnated HfCh felt was placed in the hole. The remainder of the hole was filled with hydroxide eutectic. The hydroxide eutectic was comprised of 1:1 mokmol sodium hydroxide and potassium hydroxide, and approximately 1.5g of the eutectic mixture was added. The HfCh felt was prepared by saturating HfCh in the eutectic mixture prior to assembling the cell at 200 °C overnight. The symmetric construction was then secured with stainless steel screws and nuts with insulating jackets used to ensure no electrical contact between flow fields.

[0117] The cell was heated in an oven to 220 °C overnight with steam and argon flowing to the cathode and argon flowing to the anode. The oven temperature was then increased to 230 °C and allowed to equilibrate for 30 minutes prior to performing electrochemical measurements.

[0118] Galvanostatic polarization yielded stable voltage readout on the timescale of hours. One representative trace under galvanostatic polarization running at currents between 50mA and 400mA is shown in FIG.6.MTV-24525

[0119] Example 4: Generation of H2 using Hafnia fibers electrolyte

[0120] A cell is constructed by stacking components between two custom Inconel flow blocks. Each flow block is equipped with ports for gas introduction and gas release and a flow field. A porous polytetrafluorethylene membrane (0.01” thickness) is then stacked to separate the flow fields from the rest of the cell. Catalyst in the form of compressed Ni foam is layered with a Ni foil current collector flag. Between the cathode and anode, a gasket made with expanded PTFE (1 / 16” thickness) is stacked. A hole is cut in the gasket. This hole in the gasket is filled with an electrolyte comprised of HfCh fibers and a hydroxide eutectic. The hydroxide eutectic employs a mixture of NaOH and KOH. The symmetric construction is then secured with stainless steel screws and nuts with insulating jackets used to ensure no electrical contact between flow fields.

[0121] Steam is supplied to this system under polarization to produce H2 and O2.

[0122] INCORPORATION BY REFERENCE

[0123] 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.

[0124] EQUIVALENTS

[0125] 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.

Claims

MTV-24525CLAIMSWe claim:

1. An electrolyzer, comprising:a cathode, comprising a cathode catalyst and a cathode separator;an anode, comprising an anode catalyst and an anode separator;a cathode flow field, comprising an inlet and an outlet; wherein the cathode flow field is in contact with the cathode;an anode flow field, comprising an inlet and an outlet; wherein the anode flow field is in contact with the anode; andan electrolyte,wherein the cathode separator and the anode separator each independently comprises a porous hydrophobic material.

2. The electrolyzer of claim 1, wherein:the cathode further comprises a first layer and a second layer, wherein the first layer is in contact with the second layer;the first layer comprises the cathode catalyst;the second layer comprises the cathode separator;the first layer is in contact with the electrolyte; andthe second layer is in contact with the cathode flow field.

3. The electrolyzer of claim 2, wherein the thickness of the second layer is about 0.001 cm to about 0.1 cm.

4. The electrolyzer of claim 2, wherein the thickness of the second layer is about 0.01 cm to about 0.05 cm.

5. The electrolyzer of any one of claims 1-4, wherein:the anode further comprises a third layer and a fourth layer, wherein the third layer is in contact with the fourth layer;MTV-24525the third layer comprises the anode catalyst;the fourth layer comprises the anode separator;the third layer is in contact with the electrolyte; andthe fourth layer is in contact with the anode flow field.

6. The electrolyzer of claim 5, wherein the thickness of the fourth layer is about 0.001 cm to about 0.1 cm.

7. The electrolyzer of claim 5, wherein the thickness of the fourth layer is about 0.01 cm to about 0.05 cm.

8. The electrolyzer of any one of claims 1 and 5-7, wherein:the cathode separator is in a form of cathode separator particles;the cathode separator particles are in contact with the cathode catalyst; andthe cathode separator particles are in contact with the cathode flow field.

9. The electrolyzer of any one of claims 1-4 and 8, wherein:the anode separator is in a form of anode separator particles;the anode separator particles are in contact with the anode catalyst; andthe anode separator particles are in contact with the anode flow field.

10. The electrolyzer of any one of claims 1-9, wherein the porous hydrophobic material is independently selected from the group consisting of polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PF A), fluorinated ethylene propylene (FEP), polyvinyl fluoride (PVF), and polyvinylidene fluoride (PVDF), or a combination of any of them.

11. The electrolyzer of claim 10, wherein the porous hydrophobic material is PTFE.

12. The electrolyzer of claim 10, wherein the porous hydrophobic material is PF A.MTV-2452513. The electrolyzer of any one of claims 1-12, wherein the electrolyte is a molten electrolyte.

14. The electrolyzer of claim 13, wherein the molten electrolyte has a melting temperature of about 140° C to about 300° C.

15. The electrolyzer of claim 13 or 14, 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.

16. The electrolyzer of claim 15, wherein the molten electrolyte comprises an alkali metal hydroxide.

17. The electrolyzer of claim 15, wherein the molten electrolyte comprises a eutectic mixture of two or more alkali metal hydroxides selected from the group consisting of Li OH, NaOH, KOH, CsOH, Ca(OH)2, Mg(0H)2, and Ba(OH)2.

18. The electrolyzer of any one of claims 15-17, wherein the molten electrolyte comprises KOH and NaOH.

19. The electrolyzer of claim 15, wherein the molten electrolyte comprises a eutectic mixture of two or more electrolytes selected from the group consisting of alkali metal halides and alkaline-earth metal halides.

20. The electrolyzer of claim 19, wherein the molten electrolyte comprises MgCl2, KC1, and NaCl.

21. The electrolyzer of any one of claims 1-20, wherein the electrolyte further comprises ceramic material.MTV-2452522. The electrolyzer of claim 21, wherein the ceramic material is in a form of particles, fibers, felt, or a combination of any of them.

23. The electrolyzer of claim 22, wherein the electrolyte comprises ceramic particles.

24. The electrolyzer of claim 21, wherein the ceramic material is selected from the group consisting of ZrCh , LiAlCh , yttria-stabilized zirconia, AI2O3 , HfCh, TiC , and MgO, or a combination of any of them.

25. The electrolyzer of claim 23, wherein the ceramic particles are selected from the group consisting of ZrCh particles, Li AIO2 particles, yttria-stabilized zirconia particles, AI2O3 particles, TiCh particles, and MgO particles, or a combination of any of them.

26. The electrolyzer of claim 24, wherein the ceramic particles comprise ZrO2 particles.

27. The electrolyzer of claim 24, wherein the ceramic material comprises HfO2 felt.

28. The electrolyzer of claim 24, wherein the ceramic material comprises HfO2 fibers.

29. The electrolyzer of any one of claims 23 and 25-26, wherein the diameter of the ceramic particles is about 0.1 pm to about 20 pm.

30. The electrolyzer of claim 29, wherein the diameter of the ceramic particles is about 3 pm to about 10 pm.

31. The electrolyzer of any one of claims 21-30, wherein the electrolyte comprises about 1 wt% to about 80 wt% ceramic material.

32. The electrolyzer of claim 31, wherein the electrolyte comprises about 30 wt% to about 60 wt% ceramic material.MTV-2452533. The electrolyzer of any one of claims 23, 25, 26, 29, and 30, wherein the electrolyte comprises about 1 wt% to about 80 wt% ceramic particles.

34. The electrolyzer of claim 33, wherein the electrolyte comprises about 30 wt% to about 60 wt% ceramic particles.

35. The electrolyzer of any one of claims 1-34, wherein the electrolyte further comprises water.

36. The electrolyzer of claim 35, wherein the electrolyte further comprises about 0 wt% to about 30 wt% water.

37. The electrolyzer of any one of claims 1-36, wherein the cathode catalyst comprises Ni, Fe, Co, Mn, Cr, Pt, Pd, Rh, Ir, Ag, Cu, or Au, or a combination of any of them.

38. The electrolyzer of claim 37, wherein the cathode catalyst comprises compressed Ni foam.

39. The electrolyzer of any one of claims 1-38, wherein the anode catalyst comprises Ni, Fe, Ni, Fe, Co, Mn, Cr, Pt, Pd, Rh, Ir, Ag, Cu, or Au, or a combination of any of them.

40. The electrolyzer of claim 39, wherein the anode catalyst comprises compressed Ni foam.

41. The electrolyzer of any one of claims 1-40, further comprising a cathode current collector, wherein the cathode current collector is in contact with the cathode catalyst or the cathode flow field.

42. The electrolyzer of any one of claims 1-41, further comprising an anode current collector, wherein the anode current collector is in contact with the anode catalyst or the anode flow field.

43. A method of producing H2 and O2 from steam, comprising:MTV-24525a) supplying steam to the inlet of the cathode flow field of the electrolyzer of any one of claims 1-42;b) applying an electrical potential difference across the cathode and the anode of the electrolyzer; c) collecting H2 through the outlet of the cathode flow field; andd) collecting O2 through the outlet of the anode flow field.

44. The method of claim 43, wherein the molten electrolyte is maintained at a temperature of about 140 °C to about 300 °C.

45. The method of claim 44, wherein the temperature is about 140 °C to about 250 °C.

46. The method of claim 44, wherein the temperature is about 200 °C to about 230 °C.

47. The method of any one of claims 43-46, wherein steam is supplied at a temperature of about 140 °C to about 250 °C.

48. The method of any one of claims 43-47, wherein steam is supplied at a pressure of about 6 psi to about 200 psi.

Images