Electrochemical hydrogen production using ammonia

Abstract

Contemplated herein is a method for producing hydrogen, the method including: (a) providing an electrochemical reactor having an anode, a cathode, and a membrane between the anode and the cathode; (b) introducing a first stream to the anode, the first stream comprising ammonia or products from ammonia decomposition; and (c) introducing a second stream to the cathode, the second stream comprising water, wherein the hydrogen is electrochemically generated from the water without electrical input. Also contemplated is a system for producing hydrogen from ammonia.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Patent Application No. 63 / 254,373, filed October 11, 2021, the entire disclosure of which is incorporated herein by reference. [Technical field]

[0002] The present invention relates generally to hydrogen production. More specifically, the present invention relates to electrochemical hydrogen production using ammonia. [Background technology]

[0003] Hydrogen is needed in large quantities in the petroleum and chemical industries. For example, large amounts of hydrogen are used to upgrade fossil fuels and produce methanol or hydrochloric acid. Petrochemical plants require hydrogen for hydrocracking, hydrodesulfurization, and hydrodealkylation. Hydrogenation processes to increase the saturation level of unsaturated fats and oils also require hydrogen. Hydrogen is also a reducing agent for metal ores. Hydrogen can be produced from electrolysis of water, steam reforming, laboratory-scale metal acid processes, thermochemical methods, or anaerobic corrosion. Many countries are moving towards a hydrogen economy and need to transport large amounts of hydrogen.

[0004] Ammonia has been identified as a suitable surrogate molecule for hydrogen transportation because it is relatively easy to contain and transmit, compared to either pressurized or liquefied hydrogen. However, ammonia itself is not easily utilized and must be converted to hydrogen. This conversion process unfortunately produces hydrogen mixed with nitrogen, and these two gases are difficult to separate easily, efficiently, or economically. To be useful in conventional systems and processes, the hydrogen must be separated from the nitrogen.

[0005] Clearly, there is an increasing need and importance to develop new technology platforms for producing hydrogen. This disclosure discusses the generation of hydrogen using ammonia via an efficient electrochemical route. Electrochemical reactors and methods for carrying out such reactions are discussed. Summary of the Invention

[0006] Contemplated herein is a method of producing hydrogen, the method including: (a) providing an electrochemical reactor having an anode, a cathode, and a membrane between the anode and the cathode; (b) introducing a first stream to the anode, the first stream comprising ammonia or products from ammonia decomposition; and (c) introducing a second stream to the cathode, the second stream comprising water, wherein hydrogen is electrochemically generated from the water without electrical input.

[0007] In one embodiment, the first stream and the second stream do not contact each other. In one embodiment, the products from the ammonia decomposition consist essentially of hydrogen and nitrogen. In one embodiment, the products from the ammonia decomposition are sent directly to the anode without separation or purification. In one embodiment, the ammonia decomposition occurs in situ at the anode. In one embodiment, the second stream comprises hydrogen.

[0008] In one embodiment, the anode and cathode are separated by a membrane and both are exposed to a reducing environment. In one embodiment, the anode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM. In one embodiment, the cathode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

[0009] In one embodiment, the film comprises gadolinium doped ceria, samarium doped ceria, a sintering aid, or a combination thereof. In one embodiment, the film comprises cobalt doped CGO (CoCGO). In one embodiment, the film consists essentially of CoCGO. In one embodiment, the reactor does not include wiring.

[0010] Also contemplated herein is a hydrogen production system comprising an ammonia source or ammonia decomposer, a combustor, and an electrochemical (EC) reactor comprising a mixed conducting membrane, the EC reactor configured to receive a first flow from the ammonia source or ammonia decomposer, the EC reactor configured not to receive or generate electricity. In one embodiment, the membrane conducts oxide ions and electrons, and the reactor does not comprise wiring. In one embodiment, the membrane is impermeable to the fluid flow.

[0011] In one embodiment, the first stream from the ammonia source or ammonia decomposer is not separated or purified. In one embodiment, the EC reactor comprises an anode and a cathode separated by a membrane, both of which are exposed to a reducing environment. In an embodiment, the combustor is configured to receive the anode exhaust and the oxidant from the EC reactor. In one embodiment, the cathode is configured to receive steam and to electrochemically generate hydrogen. In one embodiment, the ammonia source or ammonia decomposer is configured to receive the exhaust from the combustor.

[0012] Further aspects and embodiments are provided in the following drawings, detailed description, and claims.Unless otherwise specified, features described herein may be combined, and all such combinations are within the scope of the present disclosure. [Brief description of the drawings]

[0013] The following drawings are provided to illustrate certain embodiments described herein. The drawings are merely illustrative and are not intended to limit the scope of the claimed invention, nor are they intended to show every possible feature or embodiment of the claimed invention. The drawings are not necessarily drawn to scale, and in some instances, certain elements of the drawings may be enlarged relative to other elements of the drawings for illustrative purposes.

[0014] [Figure 1]1 illustrates an electrochemical (EC) reactor or electrochemical gas generator according to one embodiment of the present disclosure. [Figure 2A] 1 illustrates a tubular electrochemical reactor according to an embodiment of the present disclosure. [Figure 2B] 1 illustrates a cross-section of a tubular electrochemical reactor according to one embodiment of the present disclosure. [Diagram 3] 1 illustrates a process for electrochemically producing hydrogen using ammonia according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] overview Ammonia is an abundant and common chemical that is shipped worldwide. Furthermore, ammonia (unlike hydrogen) does not need to be stored under high pressure or cryogenic temperatures, and ammonia has 10 times the energy density of lithium-ion batteries. Therefore, utilizing ammonia to produce hydrogen would be highly advantageous if it could be done efficiently and economically. The disclosure herein contemplates electrochemical systems and methods that are suitable for utilizing ammonia to produce hydrogen.

[0016] The following terms and phrases have the meanings indicated below unless otherwise provided herein. This disclosure may use other terms and phrases not expressly defined herein. Such other terms and phrases are intended to have the meanings they would have within the context of this disclosure to one of ordinary skill in the art. In some cases, a term or phrase may be defined in the singular or plural. In such cases, it is understood that any term in the singular may include its plural counterpart, and vice versa, unless expressly indicated to the contrary.

[0017] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly indicates otherwise. For example, reference to a "substituent" includes a single substituent, as well as two or more substituents, and so forth. As used herein, "for example," "for instance," "such as," or "including" is meant to introduce an example that further clarifies a more general subject matter. Unless expressly indicated otherwise, such examples are provided only as an aid to understanding the embodiments illustrated in the present disclosure and are not meant to be limiting in any way. These phrases are not intended to indicate any kind of preference for the disclosed embodiments.

[0018] As used herein, compositions and materials are used interchangeably unless otherwise specified. Each composition / material may have multiple elements, phases, and components. As used herein, heating refers to the active addition of energy to a composition or material.

[0019] As used herein, YSZ refers to yttria stabilized zirconia, SDC refers to samaria doped ceria, SSZ refers to scandia stabilized zirconia, and LSGM refers to lanthanum strontium gallium magnesite.

[0020] In this disclosure, a substantial amount of H2 means that the volumetric content of hydrogen is 5% or less, or 3% or less, or 2% or less, or 1% or less, or 0.5% or less, or 0.1% or less, or 0.05% or less.

[0021] As used herein, CGO refers to gadolinium-doped ceria, which is alternatively known as gadolinia-doped ceria, gadolinium-doped cerium oxide, cerium (IV) oxide, gadolinium-doped GDC or GCO (formula Gd:CeO2). Unless otherwise specified, CGO and GDC are used interchangeably. Syngas (i.e., synthesis gas) in this disclosure refers to a mixture consisting primarily of hydrogen, carbon monoxide, and carbon dioxide.

[0022] Mixed conducting membranes are capable of transporting both electrons and ions. Ionic conductivity includes ionic species such as oxygen ions (or oxide ions), protons, halide anions, chalcogenide anions, etc. In various embodiments, the mixed conducting membranes of the present disclosure include an electronically conducting phase and an ionically conducting phase.

[0023] In this disclosure, the axial cross-section of the tubular body is shown to be circular, which is illustrative only and not limiting, but may be any suitable shape known to those skilled in the art, such as a square, a square with rounded corners, a rectangle, a rectangle with rounded corners, a triangle, a hexagon, a pentagon, an ellipse, an irregular shape, etc.

[0024] As used herein, ceria refers to cerium oxide, also known as cerium oxide, cerium dioxide, or cerium dioxide, which is an oxide of the rare earth metal cerium. Doped ceria refers to ceria doped with other elements, such as samaria-doped ceria (SDC) or gadolinium-doped ceria (GDC or CGO). As used herein, chromite refers to chromium oxide, including all oxidation states of chromium oxide.

[0025] As used herein, an impermeable layer or material refers to one that is impermeable to fluid flow. For example, an impermeable layer or material has a permeability of less than 1 microdarcy, or less than 1 nanodarcy.

[0026] In this disclosure, sintering refers to the process of forming a solid mass of a material by heat or pressure, or a combination thereof, without melting the material to the extent that it becomes liquefied. For example, material particles are heated to coalesce into a solid or porous mass, and atoms within the material particles diffuse across the boundaries of the particles, fusing the particles together to form one solid piece.

[0027] The term "in situ" in this disclosure refers to a treatment (e.g., heating or decomposition) process that occurs in the same place or within the same device. For example, ammonia decomposition that occurs in an anode electrochemical reactor is considered in situ.

[0028] Electrochemistry is a branch of physical chemistry concerned with the relationship between electrical potential as a measurable and quantitative phenomenon and an identifiable chemical change, either resulting from a particular chemical change or vice versa. These reactions involve electrons moving between electrodes through an electronically conducting phase (typically, but not necessarily, an external electric circuit) separated by an ionically conducting and electronically insulating membrane (or ionic species in solution). When a chemical reaction is driven by a potential difference, as in electrolysis, or when the electrical potential results from a chemical reaction, as in batteries or fuel cells, it is called an electrochemical reaction. Unlike chemical reactions, in electrochemical reactions, electrons (and the resulting ions) are not transferred directly between molecules, but are instead transferred through the aforementioned electronic and ionic conducting circuits, respectively. This phenomenon distinguishes electrochemical reactions from chemical reactions.

[0029] In connection with the electrochemical reactor and method of use, various components of the reactor, such as electrodes and membranes, are described, along with the materials of construction of the components. The following description details various aspects and embodiments of the invention disclosed herein. No particular embodiment is intended to define the scope of the invention. Rather, the embodiments provide non-limiting examples of various compositions and methods that fall within the scope of the claimed invention. This description should be read from the perspective of a person skilled in the art. Thus, it does not necessarily include information that is known to a person skilled in the art.

[0030] Wiring in electrochemical devices (e.g., fuel cells) is often either metal or ceramic placed between individual cells or repeating units. Its purpose is to connect each cell or repeating unit so that electricity can be distributed or combined. Wiring is also referred to as bipolar plates in electrochemical devices. As used herein, wiring that is an impermeable layer refers to one that is a layer that is impermeable to fluid flow.

[0031] Electrochemical Reactors Contrary to conventional practice, an electrochemical reactor comprising a mixed conducting membrane has been found that is capable of producing hydrogen electrochemically from water without electrical input. The electrochemical reaction involves the exchange of oxide ions through the membrane to oxidize the fuel (e.g., carbon). The mixed conducting membrane also conducts electrons to complete the electrochemical reaction. Thus, the reactor does not comprise wiring or bipolar plates. Furthermore, the reactor does not generate electrical power and is not a fuel cell. In various embodiments, the electrodes do not have current collectors attached to them. In various embodiments, the reactor does not contain any current collectors. Obviously, such a reactor is fundamentally different from any electrolysis device or any fuel cell.

[0032] FIG. 1 illustrates an electrochemical reactor or electrochemical (EC) gas generator 100 according to one embodiment of the present disclosure. The electrochemical reactor (or EC gas generator) device 100 comprises a first electrode 101, a membrane 103, and a second electrode 102. The first electrode 101 (also referred to as the anode) is configured to receive a fuel 104. The stream 104 does not contain oxygen. In this disclosure, the absence of oxygen means that there is no oxygen present at the first electrode 101, or at least not enough oxygen present to prevent a reaction. The second electrode 102 (also referred to as the cathode) is configured to receive water (e.g., steam), as indicated by 105.

[0033] In one embodiment, the device 100 is configured to receive a stream 104 containing a fuel (e.g., ammonia or ammonia decomposition products) and generate N2 and H2O (106) at the first electrode (101). In various embodiments, the fuel includes H2, CO, syngas, ammonia, or a combination thereof. In one embodiment, the device 100 is also configured to receive water or steam (105) and generate hydrogen (107) at the second electrode (102). In some cases, the second electrode receives a mixture of steam and hydrogen. Water is considered an oxidant in this scenario because it provides the oxide ions (transported through the membrane) necessary to oxidize the fuel (e.g., H2) at the opposite electrode. Thus, the first electrode 101 is undergoing an oxidation reaction in a reducing environment, and the second electrode 102 is undergoing a reduction reaction in a reducing environment. In various embodiments, 103 represents an oxide ion conducting membrane. In one embodiment, the oxide ion conducting membrane 103 also conducts electrons. The membrane is therefore mixed conducting.

[0034] In one embodiment, the first electrode 101 and the second electrode 102 comprise Ni-YSZ or NiO-YSZ. In various embodiments, the electrodes 101 and 102 comprise Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof. Alternatively, the hydrocarbon-containing gas is reformed prior to contacting the membrane 103 / electrode 101. The reformer is configured to perform steam reforming, dry reforming, or a combination thereof. The reformed gas is suitable as the feed stream 104.

[0035] In various embodiments, the device does not contain a current collector. In one embodiment, the device does not include wiring. There is no need for electricity and such a device is not an electrolyzer. This is a major advantage of the EC reactor of the present disclosure. The membrane 103 is configured to conduct electrons and is therefore mixed conducting, i.e., both electronically and ionically conducting. In one embodiment, the membrane 103 conducts oxide ions and electrons. In one embodiment, the electrodes 101, 102 and the membrane 103 are tubular (see, for example, Figures 2A and 2B). In one embodiment, the electrodes 101, 102 and the membrane 103 are planar. In these embodiments, the electrochemical reactions at the anode and cathode are spontaneous without the need to apply a potential / electricity to the reactor.

[0036] In one embodiment, an electrochemical reactor (or EC gas generator) is a device comprising a first electrode, a second electrode, and a membrane between the electrodes, the first electrode and the second electrode comprising a metal phase that does not contain platinum group metals during use of the device, and the membrane is oxide ion conductive. In one embodiment, the first electrode is configured to receive a fuel. In one embodiment, the fuel comprises ammonia, or hydrogen, or carbon monoxide, or a combination thereof. In one embodiment, the second electrode is configured to receive water and hydrogen and is configured to reduce water to hydrogen. In various embodiments, such reduction is performed electrochemically without electrical input.

[0037] In one embodiment, the membrane comprises an electronically conductive phase containing doped lanthanum chromite or an electronically conductive metal or a combination thereof, and the membrane comprises an ionically conductive phase containing a material selected from the group consisting of gadolinium doped ceria (CGO), samarium doped ceria (SDC), yttria stabilized zirconia (YSZ), lanthanum strontium gallium magnesite (LSGM), scandia stabilized zirconia (SSZ), Sc and Ce doped zirconia, and combinations thereof. In one embodiment, the doped lanthanum chromite comprises strontium doped lanthanum chromite, iron doped lanthanum chromite, strontium and iron doped lanthanum chromite, lanthanum calcium chromite, or combinations thereof, and the conductive metal comprises Ni, Cu, Ag, Au, Pt, Rh, or combinations thereof.

[0038] In one embodiment, the film comprises gadolinium doped ceria, samarium doped ceria, a sintering aid, or a combination thereof. In various embodiments, the sintering aid comprises a divalent or trivalent transition metal ion, or a combination thereof. In one embodiment, the metal ion is an oxide. In one embodiment, the transition metal comprises Co, Mn, Fe, Cu, or a combination thereof. In one embodiment, the film comprises CGO. In one embodiment, the film comprises cobalt doped CGO (CoCGO). In one embodiment, the film consists essentially of CGO. In one embodiment, the film consists of CGO. In one embodiment, the film consists essentially of CoCGO. In one embodiment, the film consists of CoCGO. In one embodiment, the reactor does not include wiring.

[0039] FIG. 2A illustrates a tubular electrochemical (EC) reactor or EC gas generator 200 (not to scale) according to one embodiment of the present disclosure. The tubular generator 200 comprises an inner tubular structure 202, an outer tubular structure 204, and a membrane 206 disposed between the inner tubular structure 202 and the outer tubular structure 204, respectively. The tubular generator 200 further comprises a void space 208 for fluid passage. FIG. 2B illustrates a cross section of the tubular generator 200 (not to scale) according to one embodiment of the present disclosure. The tubular generator 200 comprises a first inner tubular structure 202, a second outer tubular structure 204, and a membrane 206 between the inner tubular structure 202 and the outer tubular structure 204. The tubular generator 200 further comprises a void space 208 for fluid passage.

[0040] In one embodiment, the electrodes and membrane are tubular, the first electrode is outermost and the second electrode is innermost, and the second electrode is configured to receive water and hydrogen. In one embodiment, the electrodes and membrane are tubular, the first electrode is innermost and the second electrode is outermost, and the second electrode is configured to receive water and hydrogen. In one embodiment, the electrodes and membrane are tubular.

[0041] The EC reactor as discussed above is suitable for producing hydrogen from ammonia. The products from ammonia decomposition, including hydrogen and nitrogen, are sent as a feed stream directly to the anode of the EC reactor. In one embodiment, the reactor comprises porous electrodes including a metallic phase and a ceramic phase, the metallic phase being electronically conductive and the ceramic phase being ionically conductive. In various embodiments, the electrodes do not have current collectors attached to them. In various embodiments, the reactor does not contain any current collectors. Clearly, such a reactor is fundamentally different from any electrolysis device or fuel cell.

[0042] The electrochemical reactions occurring in the reactor include electrochemical half-cell reactions, the half-cell reactions being

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[0043] In various embodiments, the half-cell reaction occurs at a three-phase boundary, which is the intersection of the electronically and ionically conductive phases with the pores.

[0044] In various embodiments, the ammonia decomposition products include hydrogen and nitrogen, with hydrogen being a suitable fuel for the anode of the EC reactor. In various embodiments, the ammonia decomposition products consist essentially of hydrogen and nitrogen. In various embodiments, the ammonia decomposition products consist of hydrogen and nitrogen. An advantage of the present method and system is that the presence of nitrogen in the anode feed stream does not affect the performance of the EC reactor or the production of hydrogen on the cathode side. Another advantage of the present method and system is that since no electricity is required, the production of hydrogen from ammonia can be carried out in remote areas where electricity is not available.

[0045] In various embodiments, the ion-conducting membrane conducts oxide ions. In various embodiments, the ion-conducting membrane comprises a solid oxide. In various embodiments, the ion-conducting membrane is impermeable to fluid flow. In various embodiments, the ion-conducting membrane also conducts electrons and the reactor does not include wiring.

[0046] Hydrogen production using ammonia As illustrated in FIG. 3, a hydrogen production system 300 utilizing ammonia is shown. The system 300 includes an EC reactor 331, an ammonia decomposer 321, and a combustor 311. The EC reactor includes an anode 301, a cathode 302, and a membrane 303 between the anode and the cathode. In various embodiments, the membrane 303 is mixed conducting. An ammonia stream 322 is sent to the ammonia decomposer 321, and a product stream 323 from the ammonia decomposer is sent to the anode 301 of the EC reactor 331. The ammonia decomposition products consist of nitrogen and hydrogen, suitable for use in the anode without the need to separate the nitrogen from the hydrogen. This is a unique advantage of using the EC reactor of the present disclosure. In various cases, further ammonia decomposition takes place in situ at the anode 301, since the nickel of the anode is a catalyst for ammonia decomposition. An exhaust stream 324 from the anode 301 is sent to the combustor 311. The combustor 311 also receives an oxidant stream 312 (e.g., air or oxygen). At least a portion of the exhaust stream 324 from the combustor 311 is sent to an ammonia decomposer 321 to facilitate the decomposition of ammonia. For example, the ammonia decomposer is configured as a heat exchanger such that stream 324 provides heat to decompose the ammonia and exits as stream 325. In various embodiments, the ammonia decomposer 321 includes a catalyst (e.g., nickel). The cathode of 302 of the EC reactor 331 is configured to receive water / steam 304 and generate hydrogen (stream 305). The hydrogen is produced electrochemically by reducing water at the cathode. In some cases, stream 304 also includes hydrogen.

[0047] Alternatively, the ammonia decomposer 321 is not required. The ammonia stream 322 is sent directly to the anode 301 where ammonia decomposition occurs in situ and the EC reactor can utilize the ammonia to electrochemically reduce water to hydrogen at the cathode. This is a unique advantage of using the EC reactor of the present disclosure because (1) ammonia decomposition occurs in situ at the anode due to the presence of nickel in the anode, and (2) nitrogen does not affect the reactor performance, allowing electrochemical reduction of water to hydrogen at the cathode as hydrogen is electrochemically oxidized at the anode via oxide ions transported through the membrane. In a sense, the EC reactor of the present disclosure is also an efficient separator such that nitrogen on the fuel side (anode) does not mix with hydrogen on the product side (cathode). It is simple and inexpensive to separate hydrogen in the cathode exhaust from water.

[0048] Contemplated herein is a method of producing hydrogen, the method including: (a) providing an electrochemical reactor having an anode, a cathode, and a membrane between the anode and the cathode; (b) introducing a first stream to the anode, the first stream comprising ammonia or products from ammonia decomposition; and (c) introducing a second stream to the cathode, the second stream comprising water, the water being electrochemically generated from the water, the first stream and the second stream not contacting each other.

[0049] In one embodiment, the products from the ammonia decomposition consist of hydrogen and nitrogen. In one embodiment, the products from the ammonia decomposition are sent directly to the anode without separation or purification. In one embodiment, at least a portion of the anode exhaust gas is combusted to provide heat for the ammonia or products from the ammonia decomposition. In one embodiment, the ammonia decomposition occurs in situ at the anode. In one embodiment, the ammonia decomposition occurs in a heat exchanger.

[0050] In one embodiment, the second stream comprises hydrogen. In one embodiment, the anode and cathode are separated by a membrane and both are exposed to a reducing environment. In one embodiment, the anode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and the cathode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

[0051] In one embodiment, the membrane comprises an electronically conductive phase containing doped lanthanum chromite or a metal or a combination thereof, and the membrane comprises an ionically conductive phase containing a material selected from the group consisting of gadolinium or samarium doped ceria, yttria stabilized zirconia (YSZ), strontium gallate magnesite (LSGM), scandia stabilized zirconia (SSZ), Sc and Ce doped zirconia, and combinations thereof. In one embodiment, the doped lanthanum chromite comprises strontium doped lanthanum chromite, iron doped lanthanum chromite, strontium and iron doped lanthanum chromite, lanthanum calcium chromite, or combinations thereof, and the conductive metal comprises Ni, Cu, Ag, Au, Pt, Rh, Co, or combinations thereof.

[0052] In one embodiment, the film comprises gadolinium doped ceria, samarium doped ceria, a sintering aid, or a combination thereof. In various embodiments, the sintering aid comprises a divalent or trivalent transition metal ion, or a combination thereof. In one embodiment, the metal ion is an oxide. In one embodiment, the transition metal comprises Co, Mn, Fe, Cu, or a combination thereof. In one embodiment, the film comprises CGO. In one embodiment, the film comprises cobalt doped CGO (CoCGO). In one embodiment, the film consists essentially of CGO. In one embodiment, the film consists of CGO. In one embodiment, the film consists essentially of CoCGO. In one embodiment, the film consists of CoCGO. In one embodiment, the reactor does not include wiring.

[0053] Further contemplated herein is a hydrogen production system comprising an ammonia source or an ammonia decomposer, a combustor, and an electrochemical (EC) reactor comprising a mixed conducting membrane, wherein the EC reactor is configured to receive a first stream from the ammonia source or the ammonia decomposer, and wherein the first stream from the ammonia source or the ammonia decomposer is not separated or purified.

[0054] In one embodiment, the EC reactor comprises an anode and a cathode separated by a membrane, both of which are exposed to a reducing environment. In one embodiment, the membrane conducts electrons and the reactor does not comprise wiring. In one embodiment, the membrane is impermeable to fluid flow.

[0055] In one embodiment, the membrane comprises an electronically conductive phase containing doped lanthanum chromite or a metal or a combination thereof, and the membrane comprises an ionically conductive phase containing a material selected from the group consisting of gadolinium or samarium doped ceria, yttria stabilized zirconia (YSZ), strontium gallate magnesite (LSGM), scandia stabilized zirconia (SSZ), Sc and Ce doped zirconia, and combinations thereof. In one embodiment, the doped lanthanum chromite comprises strontium doped lanthanum chromite, iron doped lanthanum chromite, strontium and iron doped lanthanum chromite, lanthanum calcium chromite, or combinations thereof, and the conductive metal comprises Ni, Cu, Ag, Au, Pt, Rh, Co, or combinations thereof.

[0056] In one embodiment, the film comprises gadolinium doped ceria, samarium doped ceria, a sintering aid, or a combination thereof. In various embodiments, the sintering aid comprises a divalent or trivalent transition metal ion, or a combination thereof. In one embodiment, the metal ion is an oxide. In one embodiment, the transition metal comprises Co, Mn, Fe, Cu, or a combination thereof. In one embodiment, the film comprises CGO. In one embodiment, the film comprises cobalt doped CGO (CoCGO). In one embodiment, the film consists essentially of CGO. In one embodiment, the film consists essentially of CoCGO. In one embodiment, the film consists of CoCGO.

[0057] In one embodiment, the combustor is configured to receive the anode exhaust and the oxidant from the EC reactor. In one embodiment, the cathode is configured to receive the steam and generate hydrogen. In one embodiment, the ammonia source or ammonia cracker is configured to receive the exhaust from the combustor. In one embodiment, the exhaust from the combustor provides heat to the ammonia or products from the ammonia cracker.

[0058] It should be understood that the present disclosure describes exemplary embodiments for implementing different features, structures, or functions of the present invention. Exemplary embodiments of components, arrangements, and configurations are described to simplify the present disclosure. However, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the present invention. The embodiments presented herein may be combined unless otherwise specified. Such combinations do not depart from the scope of the present disclosure.

[0059] Moreover, certain terms are used throughout the description and claims to refer to particular components or steps. As one skilled in the art will appreciate, various entities may refer to the same component or process step by different names, and thus the naming conventions for the elements described herein are not intended to limit the scope of the invention. Moreover, the terminology and naming conventions used herein are not intended to distinguish between components, features, and / or steps that differ in name but not function.

[0060] While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description are not intended to limit the disclosure to the particular forms disclosed, but on the contrary, are intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure.

Claims

1. 1. A method for producing hydrogen, the method comprising: (a) providing an electrochemical reactor having an anode, a cathode, and a mixed conducting membrane between the anode and the cathode, the membrane comprising cobalt-doped CGO (CoCGO); (b) introducing a first stream to the anode, the first stream comprising ammonia or a direct product from ammonia decomposition without separation or purification; and (c) introducing a second stream to the cathode, the second stream comprising water, and hydrogen being electrochemically generated from the water without electrical input or output.

2. The method of claim 1 , wherein the first stream and the second stream do not contact each other.

3. The method of claim 1 , wherein ammonia decomposition occurs in situ at the anode.

4. The method of claim 1 , wherein the anode and the cathode are separated by the membrane and are both exposed to a reducing environment.

5. 10. The method of claim 1, wherein the anode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and the cathode comprises Ni or NiO and a material selected from the group consisting of YSZ, CGO, SDC, SSZ, LSGM, and combinations thereof.

6. A hydrogen generation system comprising: (1) an ammonia source or an ammonia decomposer; (2) a combustor; and (3) an electrochemical (EC) reactor comprising an anode, a cathode, and a mixed conducting membrane between the anode and the cathode, the membrane comprising cobalt-doped CGO (CoCGO), wherein the EC reactor is configured to receive a first flow from the ammonia source or the ammonia decomposer, and wherein the EC reactor is configured not to receive or generate electricity.

7. 7. The system of claim 6, wherein the first stream from the ammonia source or ammonia decomposer is not separated or purified.

8. 7. The system of claim 6, wherein the EC reactor comprises an anode and a cathode separated by the membrane, the anode and the cathode both being exposed to a reducing environment.

9. The system of claim 8 , wherein the combustor is configured to receive an anode exhaust and an oxidant from the EC reactor.

10. The system of claim 8 , wherein the cathode is configured to receive steam and to electrochemically generate hydrogen.

11. The system of claim 6 , wherein the ammonia source or ammonia decomposer is configured to receive exhaust from the combustor.

12. 7. The system of claim 6, wherein the membrane conducts oxide ions and electrons and the reactor does not include wiring.

13. 10. The method of claim 1 , wherein the products from the ammonia decomposition consist essentially of hydrogen and nitrogen.

14. The method of claim 1 , wherein the second stream comprises hydrogen.

15. The method of claim 1 , wherein the reactor is free of wiring.

16. The method of claim 1 , wherein the mixed conducting membrane conducts both electrons and ions.

17. The method of claim 1, wherein the film consists essentially of CoCGO.

18. The system described in claim 6, wherein the membrane consists essentially of CoCGO.

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