Electrode composition

Abstract

The present disclosure relates to electrode compositions, particularly electrode compositions comprising hybrid electrode particles, that can be used in solid oxide electrochemical cells. The present disclosure also relates to processes for preparing the hybrid electrode particles. The present disclosure also relates to electrodes (including sintered electrodes) comprising the electrode compositions, and solid oxide electrochemical cells comprising the electrode compositions.

Description

[Technical field]

[0001] The present disclosure relates to electrode compositions, particularly electrode compositions comprising hybrid electrode particles, that can be used in solid oxide electrochemical cells. The present disclosure also relates to processes for preparing the hybrid electrode particles. The present disclosure also relates to electrodes (including sintered electrodes) comprising the electrode compositions, and solid oxide electrochemical cells comprising the electrode compositions. [Background technology]

[0002] Electrochemical cells, including solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs), offer many advantages over existing energy system technologies such as natural gas reforming for hydrogen production and coal-fired power plants for electricity. For example, solid oxide electrolysis cells (SOECs) have great potential to provide a practical route for on-demand production of high purity hydrogen, CO, or syngas by using water and recycled waste CO2 from industrial processes. Specifically, hydrogen, CO, and / or syngas are important feedstocks for the production of numerous chemicals required for the pharmaceutical, food, and plastics industries. In addition, hydrogen can be used in the energy sector either directly or, as mentioned above, for the further production of various high value-added fuels such as green ammonia, methanol, dimethyl ether, etc.

[0003] Despite promising pre-commercial demonstrations, several significant technical challenges need to be addressed to make this technology economically feasible. These challenges include reducing capital costs through lower-cost materials and cell designs, as well as improving electrode performance and lifetime, including identifying new and improved electrode materials, which are the primary drivers of electrochemical performance. Other issues currently present with current electrodes (e.g., conventional nickel-YSZ cathodes) include degradation in either fuel or oxidizing environments, high cell fabrication, and sensitivity to operating temperatures. Additionally, an external reducing gas is required in the feedstream to maintain current electrodes in a reducing state, thus increasing cost and complexity.

[0004] Thus, there is a need for alternative or improved electrode compositions for use in solid oxide electrochemical cells and methods for preparing electrode compositions for solid oxide electrochemical cells that are scalable for industrial applications.

[0005] It will be understood that any prior art publications mentioned in this specification are not an admission that any of these documents form part of the general knowledge in the art in Australia or any other country. Summary of the Invention

[0006] The present disclosure provides certain electrode compositions that are scalable for industrial applications, providing control, flexibility, and consistency in the manufacture of electrodes, including electrodes for use in solid oxide electrochemical cells (e.g., solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs)) for the production of various products, such as fuel gas (using SOECs) and electricity (using SOFCs). Advantageously, the electrode compositions can be used as either positive and / or negative electrodes. In one example, the electrode compositions described herein can be used to prepare symmetric solid oxide electrochemical cells. The present disclosure also relates to various electrodes, solid oxide electrolysis cells, solid oxide fuel cells, processes, systems, generators, sensors, and / or reactors that can utilize the electrode compositions.

[0007] In one aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including at least one metal phase and an oxide phase, the metal phase including a plurality of metal particles, the oxide phase including a plurality of ionic or mixed ionic conductive oxide particles on a surface of the metal particles, each hybrid electrode particle including a plurality of ionic or mixed ionic conductive oxide particles on a surface of the metal particles, and the particle size (in nm) of the ionic or mixed ionic conductive oxide particles on the surface of the metal particles is about 1-200.

[0008] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including at least one metal phase and an oxide phase, the metal phase including a plurality of metal particles, the oxide phase including a plurality of ionic or mixed ionic conductive oxide particles on a surface of the metal particles, the plurality of ionic or mixed ionic conductive oxide particles decorating the surface of the metal particles, and the particle size (in nm) of the ionic or mixed ionic conductive oxide particles on the surface of the metal particles is about 1-100.

[0009] In some embodiments, the metal phase comprises at least one metal particle selected from silver (Ag), iron (Fe), nickel (Ni), and cobalt (Co). In other embodiments, the metal phase comprises a combination of silver (Ag) particles and one or more of iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), and titanium (Ti). In some embodiments, the oxide phase comprises ion or mixed ion conducting oxide particles selected from metal (e.g., Gd, Sm, Pr, Ni) doped ceria, metal (e.g., Cu) doped ferrite, doped lanthanum strontium ferrite (e.g., LSCF, LSTF), and lanthanum strontium chromium manganese (LSCM).

[0010] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including silver particles having a surface including one or more metal-doped ceria particles.

[0011] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including a silver particle having a surface including one or more metal-doped ceria particles, the one or more metal-doped ceria particles being decorated on the surface of the silver particle.

[0012] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including silver particles having a surface including one or more metal-doped ceria particles, the particle size of the silver particles being larger than the particle size of the metal-doped ceria particles.

[0013] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including a silver particle having a surface including one or more metal-doped ceria particles, the one or more metal-doped ceria particles being decorated on the surface of the silver particle, and the particle size of the silver particle is larger than the particle size of the metal-doped ceria particles.

[0014] In another aspect, there is provided an electrode composition comprising a plurality of hybrid electrode particles, each hybrid electrode particle comprising a silver particle having a surface comprising one or more ionic or mixed ion conducting oxide particles, the one or more ionic or mixed ion conducting oxide particles being decorated on the surface of the silver particle, the ionic or mixed ion conducting oxide particles on the surface of the silver particle having a particle size (in nm) of about 1-100.

[0015] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including a silver particle having a surface including one or more metal-doped ceria particles, the hybrid electrode particles having a particle size in μm of about 0.05-5, and the metal-doped ceria particles on the surface of the silver particles having a particle size in nm of about 1-200.

[0016] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including a silver particle having a surface including one or more metal-doped ceria particles, the hybrid electrode particles having a particle size in μm of about 0.05-5, and the metal-doped ceria particles on the surface of the silver particles having a particle size in nm of about 1-100.

[0017] In another aspect, there is provided an electrode composition comprising a plurality of hybrid electrode particles, each hybrid electrode particle comprising a silver particle having a surface comprising one or more metal-doped ceria particles, the one or more metal-doped ceria particles being decorated on the surface of the silver particle, the hybrid electrode particles having a particle size (in μm) of about 0.05-5, and the metal-doped ceria particles on the surface of the silver particle having a particle size (in nm) of about 1-100.

[0018] In another aspect, an electrode composition is provided that includes a plurality of hybrid electrode particles, each hybrid electrode particle including silver particles having a surface including one or more metal-doped ceria particles, the particle size of the silver particles being larger than the particle size of the metal-doped ceria particles, the hybrid electrode particles having a particle size (in μm) of about 0.05-5, and the metal-doped ceria particles on the surface of the silver particles having a particle size (in nm) of about 1-100.

[0019] In another aspect, there is provided an electrode composition comprising a plurality of hybrid electrode particles, each hybrid electrode particle comprising a silver particle having a surface comprising one or more metal-doped ceria particles, the one or more metal-doped ceria particles being decorated on the surface of the silver particle, the particle size of the silver particles being larger than the particle size of the metal-doped ceria particles, the hybrid electrode particles having a particle size (in μm) of about 0.05-5, and the metal-doped ceria particles on the surface of the silver particles having a particle size (in nm) of about 1-100.

[0020] In another aspect, there is provided a modified sol-gel process for preparing hybrid electrode particles, wherein each hybrid electrode particle comprises at least one metal phase and one oxide phase, the metal phase comprises at least one metal particle, the oxide phase comprises a plurality of ionic or mixed ionic conductive oxide particles on a surface of the metal particle, the plurality of ionic or mixed ionic conductive oxide particles are decorated on the surface of the metal particle, the particle size (in nm) of the ionic or mixed ionic conductive oxide particles on the surface of the metal particle is about 1-100, and the process comprises: a) preparing a gel from an aqueous solution containing metal species, ionic or mixed ionic conductive oxide species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising the hybrid electrode particles.

[0021] In another aspect, there is provided a modified sol-gel process for preparing hybrid electrode particles, the process comprising: a) preparing a gel from an aqueous solution containing silver metal species, cerium metal species, a metal dopant species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising the hybrid electrode particles.

[0022] In another aspect, there is provided a modified sol-gel process for preparing hybrid electrode particles, the process comprising: a) preparing a gel from an aqueous solution containing a bimetallic metal species, a cerium metal species, a metal dopant species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising the hybrid electrode particles.

[0023] In another aspect, there is provided a modified sol-gel process for preparing hybrid electrode particles, the process comprising: a) preparing a gel from an aqueous solution containing a bimetallic metal species, a metal-doped ferrite, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising the hybrid electrode particles.

[0024] In another aspect, there is provided an electrode comprising the electrode composition described herein, or a sintered electrode material thereof.

[0025] In another aspect, there is provided a solid oxide electrochemical cell comprising a cathode, a solid oxide electrolyte, and an anode, wherein the cathode and / or the anode comprises an electrode composition described herein, or a sintered electrode material thereof.

[0026] In another aspect, there is provided a use of the electrode composition described herein in preparing an electrode or electrode material for a solid oxide electrochemical cell.

[0027] In another aspect, there is provided a method of manufacturing a solid oxide electrochemical cell, comprising the steps of: a) preparing one or more solid oxide electrolyte layers; b) applying an electrode composition to one or both sides of a solid oxide electrolyte layer to form a component of a solid oxide electrochemical cell, wherein the electrode composition applied to at least one side of the solid oxide electrolyte layer comprises an electrode composition described herein; and c) sintering the electrode composition applied onto a component of the solid oxide electrochemical cell to form an electrode or electrode material.

[0028] It will be understood that any one or more of the embodiments and examples described herein for the electrode composition or sintered electrode material thereof may also be applied to the electrodes, solid oxide electrolysis cells, solid oxide fuel cells, processes, systems, generators, sensors, and / or reactors described herein. Any embodiment herein is deemed to apply by analogy to any other embodiment unless otherwise stated. It will also be understood that other aspects, embodiments, and examples of the electrode composition or sintered electrode material thereof, electrodes, solid oxide electrolysis cells, solid oxide fuel cells, processes, systems, generators, sensors, and / or reactors are described herein.

[0029] It will also be understood that some features of the electrode compositions or sintered electrode materials thereof, electrodes, solid oxide electrolysis cells, solid oxide fuel cells, processes, systems, generators, sensors, and / or reactors identified in some aspects, embodiments, or examples described herein may not be required in every aspect, embodiment, or example described herein, and the specification is to be read in this context. It will also be understood that in the various aspects, embodiments, or examples, the order of method or process steps may not be critical and may be varied. [Brief description of the drawings]

[0030] Preferred embodiments of the present disclosure will now be further described and illustrated, by way of example only, with reference to the accompanying drawings, in which:

[0031] [Figure 1] Schematic of a hybrid electrode particle comprising a metal particle decorated with one or more mixed ion conducting phases / metal oxide phases. [Diagram 2] FIG. 1 is a schematic diagram of an electrode composition including a plurality of hybrid electrode particles provided as a layer on an electrolyte provided for an anode in a solid oxide electrolyte mode. [Diagram 3] FIG. 1 is a schematic diagram of an electrode composition including a plurality of hybrid electrode particles provided as a layer on an electrolyte provided for a cathode in a solid oxide electrolyte mode. [Figure 4] 1 is a scanning electron microscope image of a sintered electrode material comprising a silver metal phase and one or more metal-doped ceria particles or discrete portions interspersed within the silver metal phase. [Diagram 5] Energy Dispersive Spectroscopy (EDS) layer image of a sintered electrode material containing a silver metal phase and one or more metal doped ceria particles or discrete moieties interspersed within the silver metal phase. [Figure 6] Current-voltage curves of tubular solid oxide electrolysis cells using sintered materials containing silver metal phase and one or more metal-doped ceria particles or separate pieces interspersed within the silver metal phase, Ni-YSZ composite, or mixed CGO-AG as electrodes for steam electrolysis. [Figure 7] Current-voltage curves of a tubular symmetric solid oxide electrolysis cell using a sintered electrode material containing a silver metal phase for steam electrolysis and one or more mixed ionic and electronic conductor ferrite phases (LSCFs) or separate moieties, mixed Ag-LSCFs, interspersed within the silver metal phase. [Figure 8] Current-voltage curves of a tubular asymmetric solid oxide electrolysis cell using a sintered electrode material containing one or more metal phases for steam electrolysis and one or more metal-doped ceria particles or separate moieties interspersed within the metal phase, mixed Fe-Ag-GDC. [Figure 9]Electrode polarization resistance of a tubular symmetric solid oxide electrolysis cell using a sintered electrode material including a silver metal phase for steam electrolysis and one or more metal-doped ceria particles or separate pieces interspersed within the silver metal phase, mixed Ag-GDC. [Figure 10] Short-term performance of steam electrolysis using a tubular solid oxide electrolysis cell using as electrodes a sintered material containing a silver metal phase and one or more metal-doped ceria particles or discrete portions interspersed within the silver metal phase. [Figure 11] Schematic diagram of a tube cell setup using one or more electrodes comprising a sintered hybrid electrode material, according to some embodiments or examples described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The present disclosure describes various non-limiting embodiments below, which relate to the research conducted to confirm the electrode composition. Additional non-limiting embodiments of the electrode composition, electrodes, solid oxide electrochemical cells, solid oxide fuel cells, processes, systems, generators, sensors, and / or reactors are also described. Solid oxide fuel cells (SOFCs) can convert chemical energy in fuels (e.g., hydrogen, hydrocarbon fuels, ammonia, methane, etc.) into electricity with high efficiency, and solid oxide electrolysis cells (SOECs) can store electricity from "excess" renewable energy in the form of chemical fuels (e.g., CO, H2, syngas, and other hydrocarbon fuels) via electrolysis of molecules such as H2O, CO2, and N2. In other words, solid oxide electrolysis cells (SOECs) can be used to store excess energy in fuel form when renewable sources are higher than demand. The stored fuel can then be used for combined heat and power applications by solid oxide fuel cells (SOFCs). This means that a reversible solid oxide cell (RSOC) that can produce synthetic fuels from electricity or electricity from fuel when reversed may be desirable.

[0033] The electrode composition described herein comprises a plurality of hybrid electrode particles, which are further described below according to various non-limiting embodiments and examples. Surprisingly, it has been found that the electrode composition described herein provides one or more advantages, including advantages for the synthesis of various products, such as fuel gas. According to at least some embodiments or examples described herein, the electrode composition can be advantageously used as both the positive and negative electrodes of a solid oxide electrochemical cell. It has been found that such symmetrical solid oxide electrochemical cells can provide faster manufacturing times, thus providing a scalable and effective industrial process for preparing solid oxide electrochemical cells. Other uses and advantages associated with the electrode composition are also described herein.

[0034] term In the following description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration several embodiments It is understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present disclosure.

[0035] With respect to the definitions provided herein, unless otherwise stated or implied from the context, the defined terms and phrases include the meanings provided. Unless expressly stated otherwise or clear from the context, the following terms and phrases do not exclude the meaning that the term or phrase would have acquired by one of ordinary skill in the relevant art. The definitions are provided to help describe certain embodiments and are not intended to limit the claimed invention, since the scope of the invention is limited only by the claims. Further, unless otherwise required by context, singular terms shall include the plural and plural terms shall include the singular.

[0036] All publications discussed and / or referenced herein are incorporated herein in their entirety.

[0037] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is for the purpose of providing a context for the present disclosure and is not to be construed as an admission that any or all of such matters formed part of the prior art base or were common general knowledge in the art relevant to the present disclosure by virtue of existing prior to the priority date of each claim of this application.

[0038] Throughout this disclosure, unless expressly stated otherwise or unless the context requires otherwise, reference to a single step, composition of matter, group of steps, or group of compositions of matter is to be construed as including one and more than one (i.e., one or more) of that step, composition of matter, group of steps, or group of compositions of matter. Thus, as used herein, the singular forms "a," "an," and "the" include plural aspects unless the context clearly dictates otherwise. For example, reference to "a" includes the singular and two or more, reference to "an" includes the singular and two or more, reference to "the" includes the singular and two or more, etc.

[0039] Those skilled in the art will understand that the disclosure herein is susceptible to variations and modifications other than those specifically described. The present disclosure is to be understood to include all such variations and modifications. The present disclosure also includes all of the examples, steps, features, methods, compositions, coatings, processes, and coated substrates referred to or shown herein, individually or collectively, as well as any and all combinations or any two or more of such steps or features.

[0040] The term "and / or," e.g., "X and / or Y," is understood to mean either "X and Y" or "X or Y," and is interpreted as providing explicit support for both meanings or either meaning.

[0041] Unless otherwise indicated, the terms "first," "second," and the like are used herein merely as labels, and are not intended to impose any sequential, positional, or hierarchical requirements on the items to which they refer. Moreover, a reference to a "second" item does not require or exclude the presence of a lesser number item (e.g., a "first" item) and / or a greater number item (e.g., a "third" item).

[0042] As used herein, the phrase "at least one of" when used with a list of items means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. The items may be specific objects, things, or categories. In other words, "at least one of" means that any combination or many of the items from the list may be used, but not all items in the list may be required. For example, "at least one of item A, item B, and item C" may mean item A; item A and item B; item B; item A, item B, and item C; or item B and item C. In some cases, "at least one of item A, item B, and item C" may mean, for example, but not limited to, two of item A, one of item B, and ten of item C; four of item B and seven of item C; or some other suitable combination.

[0043] As used herein, the term "about," unless otherwise specified to the contrary, typically refers to + / - 10%, for example, + / - 5% of the specified value.

[0044] It should be understood that certain features that are, for clarity, described herein in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any subcombination.

[0045] Throughout this specification, various aspects and components of the invention may be presented in a range format. The range format is included for convenience and should not be construed as unnecessarily limiting the scope of the invention. Thus, the description of a range should be considered to have specifically disclosed not only each numerical value within the range, but also all possible subranges, unless otherwise specifically indicated. For example, a description of a range such as 1-5 should be considered to have specifically disclosed subranges, such as 1-3, 1-4, 1-5, 2-4, 2-5, 3-5, etc., as well as each and every numerical value within the recited range, such as 1, 2, 3, 4, 5, 5.5, and 6, unless an integer is required or implied by context. This applies regardless of the breadth of the range disclosed. Where specific values ​​are required, these values ​​are provided in the specification.

[0046] Throughout this specification the word "comprise" or variations such as "comprises" or "comprising" will be understood to mean the inclusion of a stated element, item or step, or group of elements, items or steps, but not the exclusion of any other element, item or step, or group of elements, items or steps.

[0047] References to "substantially free" generally refer to the absence of that compound or component in a composition other than any trace amounts or impurities that may be present, which may be, for example, an amount by weight percent of the total composition of less than about 1%, 0.1%, 0.01%, 0.001%, or 0.0001%.

[0048] In this specification, "weight %" may be abbreviated as "weight % (wt%)".

[0049] electrode composition The present disclosure is directed to providing improved electrode compositions, including improved stability and performance. The present disclosure encompasses various research and development efforts directed to identifying electrode compositions for use in preparing electrodes, including those used for solid oxide electrochemical cells (e.g., solid oxide electrolysis cells (SOECs) and solid oxide fuel cells (SOFCs)). One or more advantages of the present disclosure according to at least some embodiments or examples described herein are that the electrode compositions can be used as either positive electrodes and / or negative electrodes. In one example, the electrode compositions can be used to prepare symmetric solid oxide cells, such as symmetric SOECs and symmetric SOFCs.

[0050] The SOECs described herein can be advantageously used to generate fuel gases such as: (1) hydrogen from steam electrolysis; (2) carbon monoxide from carbon dioxide electrolysis; (3) synthetic gas, also called "syngas," from electrolysis of a mixture of steam and CO; (4) ammonia production from electrolysis of a mixture of steam and nitrogen; and (5) synthetic methane production from electrolysis of a mixture of steam and CO. The generated fuel gases can be used in various chemical processes or energy production. The SOECs described herein can also be integrated with downstream fuel and chemical production processes that allow for the storage and export of renewable energy in the form of value-added chemicals and fuels. The SOECs can also use high temperatures (e.g., above 600° C.) to electrolyze steam / CO with high efficiency aided by a thermodynamically favorable steam / CO split, which can enable large-scale hydrogen / CO / syngas / ammonia / methane production. An advantage of one or more of the present disclosure, according to at least some embodiments or examples described herein, is that with commercial-scale production of SOECs, the technology is increasingly being viewed as a means to produce sustainable fuels using renewable energy.

[0051] It has been found that an electrode composition comprising a mixture of two or more phases can provide a large number of reactive sites both within and on the surface of the catalyst composition at the interface (i.e., phase boundary) between the two phases. Unexpectedly, the resulting microstructure of the electrode composition can provide one or more advantages according to at least some of the embodiments or examples described herein, including improved catalytic performance of SOECs. Other advantages provided by the electrode composition are also described herein.

[0052] The electrode composition may include a plurality of hybrid particles. The hybrid electrode particles include at least one metal phase and one metal oxide phase. In some embodiments, the metal phase may include a plurality of metal particles, and the oxide phase includes a plurality of ionic or mixed ionic conductive oxide particles on the surface of the metal particles. Each hybrid electrode particle may include one or more metal particles and one or more ionic or mixed ionic conductive oxide particles. The oxide particles may be doped with one or more additional metals. The metal particles have a surface that may include one or more oxide particles. Each hybrid electrode particle may include a metal particle having a surface that includes one or more ionic or mixed ionic conductive oxide particles. It will be understood that one or more ionic or mixed ionic conductive oxide particles are decorated on the surface of the metal particle. In other words, one or more advantages of at least some embodiments or examples as described herein may be provided by a plurality of ionic or mixed ionic conductive oxide particles decorated on the surface of a metal particle as voids between the ionic or mixed ionic conductive oxide particles, allowing the free spaces on the metal particles to form a connecting network on the metal particles to achieve advantageous electronic conductivity and reduce polarization losses in the resulting electrode structure.

[0053] The metal phase may include at least one metal particle selected from silver (Ag), iron (Fe), nickel (Ni), and cobalt (Co). In some embodiments, the metal phase may include a combination of silver (Ag) particles and one or more of iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), and titanium (Ti). In one example, the metal phase may include a combination of silver (Ag) particles and iron (Fe) particles. In another example, the metal phase may include silver (Ag) particles. The oxide phase may include ionic or mixed ionic conductive oxide particles selected from metal (e.g., Gd, Sm, Pr, Ni) doped ceria, metal (e.g., Cu, Ti, Co) doped ferrite, and lanthanum strontium chromium manganese (LSCM). The hybrid electrode particles may include silver particles and one or more ionic or mixed ionic conductive oxide particles. The silver particles have a surface that may include one or more metal oxide particles. The hybrid electrode particles may include silver particles and one or more ceria particles. The ceria particles may be doped with one or more metals. The silver particles have a surface that may include one or more metal-doped ceria particles. In one embodiment, an electrode composition is provided that includes a plurality of hybrid electrode particles.

[0054] Hybrid electrode particles In some embodiments, the electrode composition comprises a plurality of hybrid electrode particles. As used herein, the term "hybrid electrode particle" refers to a single particle that comprises at least two phases, for example, at least one metal phase (e.g., silver) and at least one metal oxide phase (e.g., ceria).

[0055] In one embodiment, the hybrid electrode particles may be of any shape, such as flakes, fibers, aggregates, granules, powders, spheres, crushed materials, and the like, as well as combinations thereof. The hybrid electrode particles may have any desired shape, including, but not limited to, cubes, rods, polyhedrons, spherical or hemispherical, circular or semicircular, angular, irregular shapes, and the like. In one embodiment, the hybrid electrode particles have an aspect ratio (i.e., the ratio of length to width, where length and width are measured perpendicular to one another and length refers to the longest linearly measured dimension) of 1.0 to 10.0, 1.0 to 5.0, or 1.0 to 2.0. In one embodiment, the hybrid electrode particles may have an aspect ratio of about 1.0 to 2.0, such as about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0.

[0056] In some embodiments, the particle size (in μm) of the hybrid electrode particles may be at least about 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.5, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, or 5. In some embodiments, the particle size (in μm) of the hybrid electrode particles may be less than about 5, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.7, 0.5, 0.2, 0.1, 0.09, 0.08, 0.07, 0.06, or 0.05. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the particle size (in μm) of the hybrid electrode particles may be about 0.05 to 5, 0.06 to 4, or 0.07 to 3.5. The particle size is taken to be the longest cross-sectional diameter across the hybrid electrode particle. For non-spherical hybrid electrode particles, particle size is taken to be the distance corresponding to the longest cross-sectional dimension across the particle.

[0057] The hybrid electrode particles may have a particle size distribution of 0-100% in the 0.05-5 μm range, or vice versa. For example, 80% of the particle sizes are in the 0.05-3 μm range and 20% of the particle sizes are in the 3-5 μm range. Other percentages having combinations of upper and / or lower particle sizes are also possible.

[0058] Particle size and / or particle size distribution can be measured by any standard method, such as laser diffraction, electron microscopy (e.g., TEM or SEM), X-ray diffraction (e.g., Scherrer equation), or dynamic light scattering. In one embodiment, particle size and / or particle size distribution can be measured using laser diffraction according to industry standard ISO 13320:2020.

[0059] metal particles The metal particles of the hybrid electrode particles may include at least one metal particle selected from silver (Ag), iron (Fe), nickel (Ni), and cobalt (Co). In some embodiments, the metal particles may include a combination of silver (Ag) particles and one or more of iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), and titanium (Ti). In other embodiments, the metal particles of the hybrid electrode particles may include a combination of silver (Ag) particles and iron (Fe) particles. It will be understood that the hybrid electrode particles include silver (Ag) particles that have high conductivity that can support the movement of electrons throughout the hybrid electrode particles and therefore throughout the electrode composition.

[0060] In one embodiment, the metal particles of each hybrid electrode particle may be of any form, such as flakes, fibers, aggregates, granules, powders, spheres, crushed materials, and the like, as well as combinations thereof. The metal particles of each hybrid electrode particle may have any desired shape, including, but not limited to, cubic, rod-like, polyhedral, spherical or hemispherical, circular or semicircular, angular, irregular, and the like. In one embodiment, the metal particles of each hybrid electrode particle may have an aspect ratio (i.e., the ratio of length to width, where length and width are measured perpendicular to one another and length refers to the longest linearly measured dimension) of 1.0 to 10.0, 1.0 to 5.0, or 1.0 to 2.0. In one embodiment, the metal particles of each hybrid electrode particle can have an aspect ratio of about 1.0 to 2.0, for example, about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0.

[0061] In some embodiments, the metal particles of each hybrid electrode particle have a particle size (in μm) of at least about 0.01, 0.05, 0.1, 0.2, 0.5, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, or 5. In some embodiments, the metal particles of each hybrid electrode particle have a particle size (in μm) of less than about 5, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.7, 0.5, 0.2, 0.1, 0.05, or 0.01. Combinations of any two or more of these upper and / or lower particle sizes are also possible. In some embodiments, the silver particles of each hybrid electrode particle have a particle size (in μm) of at least about 0.01, 0.05, 0.1, 0.2, 0.5, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, or 5. In some embodiments, the silver particles of each hybrid electrode particle have a particle size (in μm) of less than about 5, 4, 3.5, 3, 2.5, 2, 1.5, 1, 0.7, 0.5, 0.2, 0.1, 0.05, or 0.01. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the silver particles of each hybrid electrode particle have a particle size (in μm) of about 0.01-5, 0.05-5, 0.01-4, or 0.05-4. The particle size is taken to be the longest cross-sectional diameter across the metal particle. For non-spherical metal particles, the particle size is taken to be the distance corresponding to the longest cross-sectional dimension across the particle. The particle size of the metal particles of each hybrid electrode particle can be measured by electron microscopy (e.g., TEM or SEM) or X-ray diffraction (e.g., Scherrer analysis of one or more diffraction peaks).

[0062] In some embodiments, the total amount of metal particles in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is at least 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of metal particles in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10. Combinations of any two or more of these upper and / or lower amounts are also possible. In some embodiments, the total amount of silver in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is at least 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of silver in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of silver in the hybrid electrode particles can be between about 40% (w / w) and 75% (w / w). In some embodiments, the total amount of silver in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is about 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. The amount of metal and metal-doped ceria in the hybrid electrode particles can be determined using electron microscopy, including energy dispersive spectroscopy (EDS).

[0063] Ionic or mixed ionic conductive oxide particles The oxide phase may comprise ion or mixed ion conducting oxide particles selected from metal (e.g., Gd, Sm, Pr, Ni) doped ceria, metal (e.g., Cu) doped ferrite, doped lanthanum strontium ferrite (e.g., LSCF, LSTF), and doped lanthanum strontium chromate (e.g., LSCM).

[0064] By introducing a metal dopant into ceria, one or more oxygen vacancies are created. The high concentration and mobility of oxide ion vacancies results in metal-doped ceria particles with high mixed ionic and electronic conductivity. For example, a silver particle has a surface that may include one or more metal-doped ceria particles (also referred to as cerium (IV) oxide (CeO2)).

[0065] In one embodiment, the metal particles (e.g., silver) have a surface that includes multiple ion or mixed ion conductive oxide particles. The metal particles can act as a support / scaffold for the multiple ion or mixed ion conductive oxide particles. It will be understood that the hybrid electrode particles are single particles and not simply a mixture of separate metal particles and ion or mixed ion conductive oxide particles. It will be understood that each hybrid electrode particle includes a metal particle and multiple ion or mixed ion conductive oxide particles provided (i.e., decorated) on the surface of the metal particle. In other words, the multiple ion or mixed ion conductive oxide particles are interspersed, incorporated, or embedded on the surface of the metal particle and are not provided as independent particles in the composition. For example, one or more metal-doped ceria particles are decorated on the surface of a silver particle. In other words, one or more advantages of at least some embodiments or examples as described herein may be provided by a plurality of ionic or mixed ionic conductive oxide particles (e.g., metal-doped ceria particles) decorated on the surface of a metal particle (e.g., silver particle) as voids between the ionic or mixed ionic conductive oxide particles, allowing the free space on the metal particle to form a connection network on the metal particle to achieve advantageous electronic conductivity and reduce polarization loss in the resulting electrode structure. Referring to FIG. 1, an example of a hybrid electrode particle including a single metal (e.g., silver) particle is shown, and one or more ionic or mixed ionic conductive oxide particles (e.g., metal-doped ceria nanoparticles) are provided on the surface of the metal (e.g., silver) particle, thereby forming a hybrid particle. For example, the particle size of the metal (silver) particle may be larger than the particle size of the ionic or mixed ionic conductive oxide particle.

[0066] Without wishing to be bound by theory, it is believed that the junctions at the interface between the metal surface and the ionic or mixed ionic conducting oxide particles provide a plurality of reactive sites on each hybrid electrode particle. For example, the silver particles and metal-doped ceria particles on each hybrid electrode particle, when used as electrode compositions in, for example, an SOEC or SOFC, are capable of transporting electrons and / or oxygen species (O), respectively, to and from the reactive sites located on the surface of each hybrid electrode particle. 2- Due to the unique microstructure of the hybrid electrode particles, electrons and transport oxygen species (O) to and from the reactive sites located on the surface of each hybrid electrode particle can be facilitated. 2- ) is created. The location of one reactive site is provided as an example in Figures 2 and 3 (magnification) for an electrode composition comprising the hybrid electrode particles when used as the oxygen and fuel electrodes in a solid oxide electrolysis cell (SOEC).

[0067] In some embodiments, at least 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50% of the surface of the metal particle of each hybrid electrode particle may include ionic or mixed ionic conductive oxide particles. In some embodiments, less than 95, 90, 85, 80, 75, 70, 65, 60, 55, or 50% of the surface of the metal particle of each hybrid electrode particle may include ionic or mixed ionic conductive oxide particles. A plurality of ionic or mixed ionic conductive oxide (e.g., metal-doped ceria) particles may be irregularly spaced across the surface of the metal (e.g., silver) particle. It will be appreciated that the irregular voids across the surface of the metal particle create free space across the surface to form a connected network of metal particles that provides one or more advantages according to at least some embodiments or examples described herein. The amount of ionic or mixed ionic conductive oxide particles present on the surface of the metal particle may be determined using electron microscopy, including energy dispersive spectroscopy (EDS) in scanning transmission electron microscope images (STEM). An example of this is shown in Figure 5.

[0068] In one embodiment, the ionic or mixed ionic conductive oxide (e.g., metal-doped ceria) particles of each hybrid electrode particle may be in any form, such as flakes, fibers, aggregates, granules, powders, spheres, crushed materials, and the like, as well as combinations thereof. The ionic or mixed ionic conductive oxide (e.g., metal-doped ceria) particles of each hybrid electrode particle may have any desired shape, including, but not limited to, cubic, rod-like, polyhedral, spherical or hemispherical, circular or semicircular, angular, irregular, and the like. In one embodiment, the ionic or mixed ionic conductive oxide (e.g., metal-doped ceria) particles of each hybrid electrode particle may have an aspect ratio (i.e., the ratio of length to width, where length and width are measured perpendicular to one another and length refers to the longest linearly measured dimension) of 1.0 to 10.0, 1.0 to 5.0, or 1.0 to 2.0. In one embodiment, the ionic or mixed ionic conducting oxide (e.g., metal doped ceria) particles of each hybrid electrode particle may have an aspect ratio of about 1.0 to 2.0, for example, the metal doped ceria particles may provide an aspect ratio of about 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0.

[0069] In some embodiments, the ionic or mixed ionic conductive oxide particles of each hybrid electrode particle have a particle size (in μm) of at least about 1, 2, 5, 10, 25, 50, 75, 100, 125, 150, 175, or 200. In some embodiments, the ionic or mixed ionic conductive oxide particles of each hybrid electrode particle have a particle size (in μm) of less than about 200, 175, 150, 125, 100, 75, 50, 25, 10, 5, 2, or 1. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the ionic or mixed ionic conductive oxide particles of each hybrid electrode particle have a particle size (in nm) of about 1 to 200, 10 to 150, or 15 to 100. For example, the ionic or mixed ionic conductive oxide particles of each hybrid electrode particle have a particle size (in nm) of less than about 200, preferably less than about 100. In some embodiments, the metal-doped ceria particles of each hybrid electrode particle have a particle size (in nm) of at least about 1, 2, 5, 10, 25, 50, 75, 100, 125, 150, 175, or 200. In some embodiments, the metal-doped ceria particles of each hybrid electrode particle have a particle size (in nm) of less than about 200, 175, 150, 125, 100, 75, 50, 25, 10, 5, 2, or 1. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the metal-doped ceria particles of each hybrid electrode particle have a particle size (in nm) of about 1 to 200, 10 to 150, or 15 to 100. In a preferred embodiment, the ionic or mixed ionic conductive oxide particles of each hybrid electrode particle have a particle size (in nm) of less than about 100. The particle size is taken to be the longest cross-sectional diameter across the oxide particle. For non-spherical ionic or mixed ionic conductive oxide particles, the particle size is taken to be the distance corresponding to the longest cross-sectional dimension across the particle. The particle size of the ionic or mixed ionic conductive oxide particles of each hybrid electrode particle can be measured by electron microscopy (e.g., TEM or SEM) or X-ray diffraction (e.g., Scherrer analysis of one or more diffraction peaks).

[0070] In some embodiments, the total amount of ionic or mixed ionic conducting oxides in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is at least 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of ionic or mixed ionic conducting oxides in the hybrid electrode particles is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of ionic or mixed ionic conducting oxides in the hybrid electrode particles can be between about 20% (w / w) and 50% (w / w), or between about 25% and 45% (w / w). In some embodiments, the total amount of ceria in the hybrid electrode particles (% w / w based on the total weight of the hybrid electrode particles) is at least 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of ceria in the hybrid electrode particles is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of ceria in the hybrid electrode particles can be between about 20% (w / w) and 50% (w / w), or between about 25% and 45% (w / w).

[0071] In some embodiments, the total amount of metals in the hybrid electrode particles is between about 20% (w / w) and 80% (w / w) and the total amount of oxides in the hybrid electrode particles is between about 20% (w / w) and 50% (w / w). In some embodiments, the total amount of metals in the hybrid electrode particles is between about 55% (w / w) and 75% (w / w) and the total amount of oxides in the hybrid electrode particles is between about 25% (w / w) and 45% (w / w).

[0072] In some embodiments, the total amount of silver in the hybrid electrode particles is between about 20% (w / w) and 80% (w / w) and the total amount of ceria in the hybrid electrode particles is between about 20% (w / w) and 50% (w / w). In some embodiments, the total amount of silver in the hybrid electrode particles is between about 55% (w / w) and 75% (w / w) and the total amount of ceria in the hybrid electrode particles is between about 25% (w / w) and 45% (w / w).

[0073] In some embodiments, the % w / w ratio of metal to oxide in the hybrid electrode particles is at least 1:10, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, or 10:1. In some embodiments, the % w / w ratio of metal to oxide in the hybrid electrode particles is less than 10:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or 10:1. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the % w / w ratio of metal to oxide in the hybrid electrode particles can be from about 1:5 to about 5:1, or from about 1:2 to about 1:1. In some embodiments, the % w / w ratio of silver to ceria in the hybrid electrode particles is at least 1:10, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, or 10:1. In some embodiments, the % w / w ratio of silver to ceria in the hybrid electrode particles is less than 10:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or 10:1. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the % w / w ratio of silver to ceria in the hybrid electrode particles can be from about 1:5 to about 5:1, or from about 1:2 to about 1:1.

[0074] It will be understood that the multiple ion or mixed ion conducting oxide particles can be doped with one or more metal species. For example, ceria particles can be doped with gadolinium (Gd), samarium (Sm), praseodymium (Pr) or nickel (Ni). In another example, ferrite can be doped with titanium (Ti), cobalt (Co) and copper (Cu), or lanthanum strontium chromate can be doped with manganese (Mn), calcium (Ca), bismuth (Bi), copper (Cu), ruthenium (Ru). One or more ceria particles can be doped with one or more metal species. The metal dopant can be provided by one or more metals selected from rare earth metals and alkaline earth metals.

[0075] In some embodiments, the metal dopant for the oxide particles may be provided by one or more of samarium (Sm), gadolinium (Gd), lanthanum (La), zirconium (Zr), yttrium (Y), ytterbium (Yb), erbium (Er), praseodymium (Pr), nickel (Ni), or by one or more of gadolinium (Gd), samarium (Sm), and yttrium (Y). In one embodiment, the metal dopant is gadolinium (Gd). It will be appreciated that gadolinium, samarium, and cerium have similar ionic sizes, and therefore a large number of oxygen vacancies are created. It has been found that a high concentration and mobility of oxide ion vacancies advantageously provides ionic or mixed ionic conducting oxide (e.g., metal-doped ceria) particles with high ionic conductivity. However, it will be appreciated that other metal dopants may also provide good ionic conductivity.

[0076] The metal dopant and oxide are single phase. The ratio of metal dopant to oxide in the ionic or mixed ionic conductive oxide particles can be about 100:1 to 2:1, about 50:1 to 3:1, or about 20:1 to 4:1. The ratio of metal dopant to oxide in the ionic or mixed ionic conductive oxide particles can be at least about 2:1, 3:1, 4:1, 5:1, 10:1, 20:1, 50:1, or 100:1. The ratio of metal dopant to oxide in the ionic or mixed ionic conductive oxide particles can be less than about 100:1, 50:1, 20:1, 10:1, 5:1, 4:1, 3:1, or 2:1. In one example, the metal dopant and ceria are single phase. The ratio of metal dopant to ceria in the metal doped ceria particles can be about 100:1 to 2:1, about 50:1 to 3:1, or about 20:1 to 4:1. The ratio of metal dopant to ceria in the metal doped ceria particles can be at least about 2:1, 3:1, 4:1, 5:1, 10:1, 20:1, 50:1, or 100:1. The ratio of metal dopant to ceria in the metal doped ceria particles can be less than about 100:1, 50:1, 20:1, 10:1, 5:1, 4:1, 3:1, or 2:1.

[0077] The amount of metal dopant present in the ceria particles is expressed by the formula Ce 1-x M x O 2-δ where x is about 0.01-0.3, 0.02-0.25, or 0.05-0.2, M is one or more metal dopants as defined above, and δ is about 0.0-0.5, or 0.1-0.4. Combinations of any two of these upper and / or lower values ​​are also possible.

[0078] The amount of metal dopant in the oxide particles can vary. In some embodiments, the amount of metal dopant in the oxide particles (% w / w based on the total weight of the ionic or mixed ionic conductive oxide particles) is at least about 1, 2, 5, 10, 15, 20, 25, 30, 40, or 50. In some embodiments, the amount of metal dopant in the oxide particles (% w / w based on the total weight of the ionic or mixed ionic conductive oxide particles) is at least about 50, 40, 30, 25, 20, 15, 10, 5, 2, or 1. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the amount of metal dopant in the oxide particles can be about 1% (w / w) to 35% (w / w), about 2% (w / w) to 30% (w / w), or about 5% (w / w) to 25% (w / w). In some embodiments, the amount of metal dopant in the oxide particles (% w / w based on the total weight of the ionic or mixed ionic conductive oxide particles) is about 1, 2, 5, 10, 15, 20, 25, 30, 40, or 50. In some embodiments, the amount of metal dopant in the ceria particles (% w / w based on the total weight of the metal doped ceria particles) is at least about 1, 2, 5, 10, 15, 20, 25, 30, 40, or 50. In some embodiments, the amount of metal dopant in the ceria particles (% w / w based on the total weight of the metal doped ceria particles) is at least about 50, 40, 30, 25, 20, 15, 10, 5, 2, or 1. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the amount of metal dopant in the ceria particles can be about 1% (w / w) to 35% (w / w), about 2% (w / w) to 30% (w / w), or about 5% (w / w) to 25% (w / w). In some embodiments, the amount of metal dopant in the ceria particles (% w / w based on the total weight of the metal doped ceria particles) is about 1, 2, 5, 10, 15, 20, 25, 30, 40, or 50.

[0079] In addition to the hybrid electrode particles, the electrode composition may further include one or more additives. In one embodiment, the electrode composition may further include a conductive additive. For example, the conductive additive may include one or more metal additives, such as nickel powder, titanium powder, stainless steel powder, and mixtures thereof.

[0080] Sintered Electrode Materials The electrode composition may be provided as a sintered electrode material. As used herein, the term "sintered electrode material" refers to an electrode material produced by heating (e.g., igniting) an electrode composition including hybrid electrode particles such that metal particles of the hybrid electrode particles coalesce and adhere to one another to form a continuous or semi-continuous metal-metal phase within the electrode material of a solid oxide electrochemical cell.

[0081] The metal phase may include one or more metal moieties. In some embodiments, the metal phase is a porous scaffold. In one embodiment, the silver metal phase may include one or more silver metal moieties. In some embodiments, the silver metal phase is a porous scaffold. The porous nature facilitates the movement of ionic species throughout the electrode material. After sintering to form the metal phase (i.e., a scaffold including a porous silver metal phase), the ionic or mixed ion conducting oxide particles may remain as separate particles connected to the surface of the metal phase and / or may attach to other ionic or mixed ion conducting oxide particles to form one or more separate oxide phases (e.g., moieties) connected to the surface of the metal phase. In one embodiment, the sintered electrode material includes a silver metal phase as a porous scaffold and a plurality of separate oxide phases interspersed within the silver metal phase. The separate oxide phases may be in the form of metal-doped ceria particles.

[0082] The separate oxide (e.g., metal-doped ceria) phase (e.g., particles or moieties) may be interspersed within the metal (e.g., silver) phase. Without wishing to be bound by theory, the junctions at the interfaces between the metal phase surface and the separate oxide phase provide multiple reactive sites throughout the sintered electrode material. The metal (e.g., silver) scaffold and the separate oxide (metal-doped ceria) phases, when used as electrode compositions in, for example, SOECs or SOFCs, respectively, facilitate the transfer of electrons and / or oxygen species (O) to and from reactive sites located throughout the sintered electrode material. 2- For example, the unique microstructure of the sintered electrode can facilitate the transport of electrons and mobile oxygen species (O 2- ) is created. The location of one reactive site in the sintered electrode material is provided as an example in the schematic diagram of FIG. 3 when the sintered electrode composition is used as an oxygen electrode in a solid oxide electrolysis cell (SOEC). A scanning electron microscope image of the sintered electrode composition is also shown in FIG. 4, showing the sintered silver phase with metal doped ceria.

[0083] In some embodiments, the sintered electrode material is 3 The sintered electrode material may comprise at least about 1, 2, 5, 10, 20, 50, 70, 100, 150, 200, 250, 300, 400, 500, 700 or 1000 distinct oxide phases per cm 3 The sintered electrode material may contain less than about 1000, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 20, 10, 5, 2, or 1 distinct oxide phase per metal phase. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the sintered electrode material may contain less than about 1000, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 20, 10, 5, 2, or 1 distinct oxide phase per metal phase per cm. 3 In some embodiments, the sintered electrode material may include about 10-100, 50-500, or 100-300 distinct oxide phases per cm of metal phase. 3The sintered electrode material may comprise at least about 1, 2, 5, 10, 20, 50, 70, 100, 150, 200, 250, 300, 400, 500, 700 or 1000 distinct metal-doped ceria phases per cm of silver metal phase. 3 The sintered electrode material may contain less than about 1000, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 20, 10, 5, 2 or 1 separate metal-doped ceria phases per cm of silver metal phase. Combinations of any two or more of these upper and / or lower amounts are also possible, e.g., the sintered electrode material may contain less than about 1000, 700, 500, 400, 300, 250, 200, 150, 100, 70, 50, 20, 10, 5, 2 or 1 separate metal-doped ceria phases per cm of silver metal phase. 3 For example, the silver metal phase may contain about 10-100, 50-500, or 100-300 distinct metal-doped ceria phases per silver metal phase. It will be appreciated that the interspersion of distinct oxide (e.g., metal-doped ceria) phases within the metal (e.g., silver) phase can be determined by a range of instruments and methods, including spectroscopy and microscopy, e.g., scanning electron microscopy.

[0084] In contrast to conventional mixing and grinding approaches in which individual metal and oxide particles are present in the composition, sintering an electrode composition comprising hybrid electrode particles comprising metal particles decorated with distinct oxide particles results in an electrode material with improved dispersion of distinct oxide (e.g., metal-doped ceria) particles or phases interspersed throughout a porous metal (e.g., silver) scaffold, as evidenced by the resulting microstructure. Surprisingly, it has been found that this sintering process provides electrode materials with enhanced electrical and ionic conductivity and catalytic activity for use as electrodes in solid oxide cells, such as SOECs or SOFCs. It will be appreciated that pre-sintering of the hybrid electrode particles also provides a microstructure exhibiting metal (e.g., silver) particles decorated with oxide (e.g., ceria) particles, as opposed to a heterogeneous mixture of separate particles or metal particles coated with fine oxide particles such that the entire surface of the metal particles is covered with fine oxide particles.

[0085] In some embodiments, the discrete oxide particles / phases interspersed within the metal phase have a size (in nm) of at least about 1, 2, 5, 10, 25, 50, 75, 100, 125, 150, 175, 200, 400, 600, 800, or 1000. In some embodiments, the discrete oxide particles / phases interspersed within the metal phase have a size (in nm) of less than about 1000, 800, 600, 400, 200, 175, 150, 125, 100, 75, 50, 25, 10, 5, 2, or 1. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, the discrete oxide particles / phases interspersed within the metal phase have a size (in nm) of about 1-600, 2-400, 3-200, or 4-100. In some embodiments, the separate metal-doped ceria particles / phases interspersed within the silver metal phase have a size (in nm) of at least about 1, 2, 5, 10, 25, 50, 75, 100, 125, 150, 175, 200, 400, 600, 800, or 1000. In some embodiments, the separate metal-doped ceria particles / phases interspersed within the silver metal phase have a size (in nm) of less than about 1000, 800, 600, 400, 200, 175, 150, 125, 100, 75, 50, 25, 10, 5, 2, or 1. Combinations of any two or more of these upper and / or lower particle sizes are also possible, for example, distinct metal-doped ceria particles / phases interspersed within the silver metal phase have sizes (in nm) of about 1-600, 2-400, 3-200, or 4-100. The size of the oxide (e.g., metal-doped ceria) phases / particles interspersed within the metal (e.g., silver) phase can be measured by electron microscopy (e.g., TEM or SEM) or X-ray diffraction (e.g., Scherrer analysis of one or more diffraction peaks).

[0086] In some embodiments, the total amount of metal phase in the sintered electrode material (% w / w based on the total weight of the sintered electrode material) is at least 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of metal phase in the sintered electrode material (% w / w based on the total weight of the sintered electrode material) is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of metal phase in the sintered electrode material may be between about 20% (w / w) and 80% (w / w), or between about 55% and 75% (w / w). In some embodiments, the total amount of metal phase in the sintered electrode material (% w / w based on the total weight of the sintered electrode material) is about 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of silver metal phase in the sintered electrode material (% w / w based on the total weight of the sintered electrode material) is at least 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of silver metal phase in the sintered electrode material (% w / w based on the total weight of the sintered electrode material) is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, or 10. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of silver metal phase in the sintered electrode material can be about 20% (w / w) to 80% (w / w), or about 55% to 75% (w / w). In some embodiments, the total amount of silver metal phase in the sintered electrode material (% w / w based on the total weight of the sintered electrode material) is about 10, 15, 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80.

[0087] In some embodiments, the total amount of oxides interspersed within the metal phase (% w / w based on the total weight of the sintered electrode material) is at least 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of oxides interspersed within the metal phase (% w / w based on the total weight of the sintered electrode material) is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of oxides interspersed within the metal phase can be between about 20% (w / w) and 50% (w / w), or between about 25% and 45% (w / w). In some embodiments, the total amount of oxides interspersed within the metal phase (% w / w based on the total weight of the sintered electrode material) is about 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of metal phases in the sintered electrode material is about 20% (w / w) to 80% (w / w) and the total amount of oxides in the sintered electrode material is about 20% (w / w) to 60% (w / w). In some embodiments, the total amount of metal phases in the sintered electrode material is about 55% (w / w) to 75% (w / w) and the total amount of oxides in the sintered electrode material is about 25% (w / w) to 45% (w / w). In some embodiments, the total amount of ceria interspersed within the silver metal phase (% w / w based on the total weight of the sintered electrode material) is at least 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80. In some embodiments, the total amount of ceria interspersed within the silver metal phase (% w / w based on the total weight of the sintered electrode material) is less than about 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20. Combinations of any two or more of these upper and / or lower amounts are also possible, for example, the total amount of ceria interspersed within the silver metal phase can be between about 20% (w / w) and 80% (w / w), or between about 25% and 45% (w / w). In some embodiments, the total amount of ceria interspersed within the silver metal phase (% w / w based on the total weight of the sintered electrode material) is about 20, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, or 80.In some embodiments, the total amount of silver metal phase in the sintered electrode material is between about 20% (w / w) and 80% (w / w) and the total amount of ceria in the sintered electrode material is between about 20% (w / w) and 60% (w / w). In some embodiments, the total amount of silver metal phase in the sintered electrode material is between about 55% (w / w) and 75% (w / w) and the total amount of ceria in the sintered electrode material is between about 25% (w / w) and 45% (w / w).

[0088] The thickness of the sintered electrode material is determined by the amount of electrons and / or ionic species (e.g., O 2- ), porosity, and reactions of reactant species occurring within the electrode.

[0089] The sintered electrode material may have some degree of porosity. In some embodiments, the sintered electrode material may have a porosity (volume % based on the total volume of the sintered electrode material) of at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70. In some embodiments, the sintered electrode material may have a porosity (volume % based on the total volume of the sintered electrode material) of less than 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. Combinations of any two or more of these upper and / or lower porosity values ​​are also possible, for example, the sintered electrode material may have a porosity of about 10-60, about 20-50, about 25-45, or about 30-40 volume % based on the total volume of the sintered electrode material.

[0090] The porosity of the sintered electrode material can be determined by the density of the hybrid electrode particles in the electrode composition before sintering. The porosity can be determined by any suitable means, for example, by electron microscope image analysis of a cross-section of the sintered electrode material using a mercury porosimeter or by using image analysis tools such as ImageJ to display and measure the porosity in contrast.

[0091] The sintered electrode material may have any suitable thickness depending on the sintering of the electrode composition including the hybrid electrode particles. The thickness of the sintered electrode material may be in any one of the ranges (in μm) of about 10-2000, about 15-1000, about 20-500, about 25-400, about 30-300, about 40-200, or about 50-150. The thickness of the sintered electrode material is at least about 10 μm, 30 μm, 50 μm, 70 μm, or 90 μm 150 μm, 200 μm, 300 μm, 500 μm, 750 μm, or 1000 μm. The thickness of the sintered electrode material may be less than about 2000 μm, 1500 μm, 1000 μm, 800 μm, 600 μm, 400 μm, or 200 μm. The thickness of the sintered electrode material may be in any one of the ranges (in μm) of about 1-100, about 5-80, about 5-70, about 10-50, or about 15-40. The thickness of the sintered electrode material is at least about 1 μm, 5 μm, 10 μm, 20 μm, 50 μm, 70 μm 80 μm, or 100 μm. The thickness of the sintered electrode material may be less than about 100 μm, 80 μm, 70 μm, 50 μm, 20 μm, 10 μm, 5 μm, or 1 μm.

[0092] Coating Formulation The electrode composition may be a coating formulation, such as a liquid formulation, to which the following examples and embodiments may be applied. The electrode composition, or sintered electrode material thereof, may be provided as a coating formulation for commercial and industrial applications. The coating formulation may be prepared to apply the electrode composition, or sintered electrode material thereof, onto the surface of a substrate, as described in any one of the examples or embodiments. The coating formulation may be prepared by dissolving or dispersing the electrode composition or sintered electrode material thereof according to any embodiment or example described herein in a suitable solvent, and then optionally mixing them together with one or more additives (e.g., binders), or dissolving the composition in a suitable solvent under suitable processing conditions. For example, the coating formulation may be a wet coating formulation comprising the electrode composition or sintered electrode material thereof, a solvent, and optionally a binder. One exemplary method is to first dissolve the binder in the solvent of the formulation, which may be done by using with heat and / or stirring. The electrode composition or sintered electrode material thereof may then be added, desirably at a gradual addition rate to avoid clumping. Heat and / or stirring may again be applied during addition of the electrode composition or sintered electrode material thereof.

[0093] The wet coating formulation may be applied to a substrate (e.g., a solid electrolyte) in different physical forms such as a solution, dispersion, suspension, mixture, aerosol, emulsion, paste, or combinations thereof, with a solution or dispersion or emulsion being preferred.

[0094] In some embodiments, the wet coating formulation may be a dip coating formulation, a printable ink formulation, or a brush printing formulation. The wet coating formulation may be a dip coating formulation. The wet coating formulation may be a printable ink formulation. The wet coating formulation may be a brush printing formulation. Any solvent may be used that can dissolve / suspend the electrode composition or its sintered electrode material and binder in the coating formulation. The solvent may be a single solvent or a mixture of solvents that can dissolve the binder and evaporate after dip coating while being dried under mild drying conditions, such as, for example, at about 50°C to about 250°C. The solvent may be an alcohol, an ester, a terpene, a ketone, an aliphatic, an aromatic, an ether, or water (including mixtures thereof). In one embodiment, the solvent may be an alcohol. Suitable alcohol solvents include monohydric alcohols, diol alcohols such as glycols, ether alcohols, and terpene alcohols. Examples include methanol, ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, hexanol, heptanol, cyclohexanol, butyl glycol, diols such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, ether alcohols such as butoxyethanol, propoxypropanol and butyl diglycol, and terpene alcohols such as terpineol (α-terpineol), β-terpineol, geranol, cineol, cedral, linalool, 4-terpinol, lavandol, citronellol, or nerol. In one example, ethanol may be a preferred solvent. In another example, a mixture of one or more solvents may be used, such as a mixture of ethanol and α-terpinol.

[0095] The coating formulation may include a solvent (% w / w)) in an amount of at least about 1, 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 based on the total weight of the formulation. The coating formulation may include a solvent (% w / w)) in an amount of less than about 50, 45, 40, 35, 30, 25, 20, 15, 10, 5, 2, or 1 based on the total weight of the formulation. Combinations of these amounts are also possible, for example, from about 25% (w / w) to about 45% (w / w). In some embodiments, the coating formulation includes a monohydric alcohol solvent (e.g., ethanol) in an amount of about 20% (w / w) to 40% (w / w) and a terpene alcohol solvent (e.g., α-terpinol) in an amount of about 1% (w / w) to about 10% (w / w) based on the total weight of the coating formulation.

[0096] Any suitable binder may be used to prepare the coating formulation. In one embodiment, the binder may be polyvinyl butyral, polyvinyl alcohol, polyacrylic acid ester, polymethyl methacrylate, or ethyl cellulose. The coating formulation may include an amount of binder (% w / w) of at least about 1, 2, 3, 4, 5, 6, 8, 10, 15, or 20 based on the total weight of the formulation. The coating formulation may include an amount of binder (% w / w) of less than about 20, 15, 10, 8, 6, 5, 4, 3, 2, or 1 based on the total weight of the formulation. Combinations of these amounts are also possible, for example, from about 1% (w / w) to about 5% (w / w).

[0097] In some embodiments or examples, the thickness of the coating formulation may range from about 1 to about 100 μm. The thickness (in μm) may be less than about 100, 80, 60, 40, 20, 15, 10, 8, 6, 4, 2, or 1. The thickness (in μm) may be at least about 1, 2, 4, 6, 8, 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, or 100. The thickness (in μm) of the coating formulation may be in a range provided by any two of these upper and / or lower limits. For example, the thickness of the coating formulation may be about 50 μm. The thickness of the coating formulation is determined by the amount of electrons and / or transfer ionic species (e.g., O, OH ... 2- ), porosity, and reactions of reactant species occurring within the electrode.

[0098] The coating formulation may have some degree of porosity. In some embodiments, the coating formulation may have a porosity (volume % based on the total volume of the coating formulation) of at least 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70. In some embodiments, the coating formulation may have a porosity (volume % based on the total volume of the sintered electrode material) of less than 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15, 10, or 5. Combinations of any two or more of these upper and / or lower porosity values ​​are also possible, for example, the coating formulation may have a porosity of about 10-60, about 20-50, about 25-45, or about 30-40 volume % based on the total volume of the sintered electrode material.

[0099] The porosity of the coating formulation can be determined by the density of the hybrid electrode particles in the electrode composition before sintering. The porosity can be determined by any suitable means, for example, by electron microscope image analysis of a cross-section of the coating formulation using a mercury porosimeter or by using an image analysis tool such as ImageJ to display and measure the porosity in contrast.

[0100] Process for preparing hybrid electrode particles The present inventors have also identified a modified sol-gel process that can be used to prepare hybrid electrode particles. By controlling the reaction conditions and reagents of the modified sol-gel process, the stoichiometry of silver and ceria in the hybrid electrode particles can be fine-tuned, resulting in electrode compositions, including electrode compositions with improved electrical, ionic, and / or catalytic properties.

[0101] The hybrid electrode particles can be prepared by a modified sol-gel process. As used herein, the term "modified sol-gel process" refers to the synthesis of a solid material from a solution-state precursor, which involves converting a monomer into a colloidal solution (i.e., a sol) that acts as a precursor to a network (or gel) of separate particles, which is then heated to obtain a solid material. One example of such a process is the Pechini process.

[0102] A modified sol-gel process for preparing hybrid electrode particles, each hybrid electrode particle comprising at least one metal phase and one oxide phase, the metal phase comprising a plurality of metal particles, the oxide phase comprising a plurality of ionic or mixed ionic conductive oxide particles on the surface of the metal particles, the plurality of ionic or mixed ionic conductive oxide particles being decorated on the surface of the metal particles, the particle size (in nm) of the ionic or mixed ionic conductive oxide particles on the surface of the metal particles being about 1-100, the process comprising: a) preparing a gel from an aqueous solution containing metal species, ionic or mixed ionic conductive oxide species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising hybrid electrode particles.

[0103] In another embodiment, a modified sol-gel process for preparing hybrid electrode particles comprises: a) preparing a gel from an aqueous solution containing silver metal species, cerium metal species, a metal dopant species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising the hybrid electrode particles.

[0104] In another embodiment, there is provided a modified sol-gel process for preparing hybrid electrode particles, the process comprising: a) preparing a gel from an aqueous solution containing a bimetallic metal species, a cerium metal species, a metal dopant species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising hybrid electrode particles.

[0105] In another embodiment, there is provided a modified sol-gel process for preparing hybrid electrode particles, the process comprising: a) preparing a gel from an aqueous solution containing a bimetallic metal species, a metal-doped ferrite, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising hybrid electrode particles.

[0106] metal type One or more of the metal species (e.g., cerium, silver, etc.) and metal dopant species may be provided as their salts or hydrates. In one embodiment, the metal species and metal dopant species are cationic (i.e., ionic salts or hydrates thereof). The metal species and metal dopant species should be soluble or miscible in aqueous solution, either alone or in the presence of a chelating agent. Thus, typical salts include hydroxides, alkoxides, acetates, chlorides, citrates, and nitrates, with nitrates being preferred.

[0107] The metal (e.g., silver) species may be provided as any suitable salt or hydrate thereof, independently selected from hydroxides, chlorides, alkoxides, acetates, citrates, nitrates, and oxides. In some embodiments, the silver metal species may be provided as silver nitrate (AgNO), silver chloride (AgCl), silver hydroxide (AgOH), or silver oxide (AgO), or hydrates thereof.

[0108] The metal (e.g., cerium) species may be provided as any suitable salt or hydrate thereof, independently selected from hydroxide, chloride, alkoxide, acetate, citrate, nitrate, and oxide salts. In some embodiments, the cerium metal species may be provided as cerium nitrate (Ce(NO3)3), cerium chloride (CeCl3), cerium hydroxide (Ce(OH)3), or cerium oxide (Ce2O3), or a hydrate thereof. Examples of suitable hydrates include hexahydrate salts, such as cerium nitrate hexahydrate (Ce(NO3)3·6H2O).

[0109] In one embodiment, the present inventors have unexpectedly found that a combination of silver nitrate (AgNO3) and cerium nitrate (Ce(NO3)3) can result in hybrid electrode particles with improved conductivity and catalytic activity. It will be appreciated that the improved conductivity and catalytic activity can be attributed to the resulting microstructure exhibiting silver particles decorated with nanocrystalline ceria particles. However, other salt forms, including cerium chloride (CeCl3), have also resulted in hybrid electrode particles with similar performance and / or microstructure.

[0110] In another embodiment, the present inventors have unexpectedly found that a combination of silver nitrate (AgNO3) and iron nitrate nonahydrate as metal species with doped cerium nitrate (Ce(NO3)3) as a mixed oxide phase can result in hybrid electrode particles with improved conductivity and catalytic activity. It will be appreciated that the improved conductivity and catalytic activity can be attributed to the resulting microstructure exhibiting bimetallic metal particles decorated with nanocrystalline ceria particles.

[0111] In another embodiment, the present inventors have unexpectedly found that a combination of silver nitrate (AgNO3) as the metal species with lanthanum nitrate hexahydrate, strontium nitrate, cobalt nitrate hexahydrate and iron nitrate nonahydrate as mixed oxide phases can result in hybrid electrode particles with improved conductivity and catalytic activity. It will be appreciated that the improved conductivity and catalytic activity can be attributed to the resulting microstructure exhibiting bimetallic metal particles decorated with lanthanum strontium doped ferrite phases.

[0112] The metal dopant species may be provided as any suitable salt or hydrate thereof. In some embodiments, the metal dopant species may be selected from rare earth metal salts or alkaline earth metal salts or hydrates thereof. In some embodiments, the metal dopant species may be provided by one or more metal salts or hydrates thereof selected from samarium (Sm), gadolinium (Gd), lanthanum (La), zirconium (Zr), yttrium (Y), ytterbium (Yb), erbium (Er), praseodymium (Pr) or neodymium (Nd) salts or hydrates thereof. The salt may be any one or more of a nitrate, chloride, hydroxide, or oxide. In some embodiments, the metal dopant species may be provided by one or more nitrates of samarium (Sm), gadolinium (Gd), lanthanum (La), zirconium (Zr), yttrium (Y), ytterbium (Yb), erbium (Er), praseodymium (Pr), or neodymium (Nd) salts, or hydrates thereof. In some embodiments, the metal dopant species may be provided by gadolinium (Gd), samarium (Sm), and yttrium (Y) nitrates, or hydrates thereof.

[0113] In one embodiment, the metal dopant species may be provided by gadolinium nitrate (Gd(NO3)3) or a hydrate thereof, such as gadolinium nitrate hexahydrate (Gd(NO3)3·6H2O). The inventors have determined that a good amount of metal doping within the ceria particles can occur using gadolinium nitrate due to the similar ionic size of gadolinium compared to cerium, allowing for efficient incorporation of gadolinium into the cerium network.

[0114] In some embodiments, the oxide species and metal dopant species may be provided in an aqueous solution at a concentration of at least about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M, respectively. In some embodiments, the oxide species and metal dopant species may be provided in an aqueous solution at a concentration of less than about 1.0, 0.5, 0.4, 0.3, 0.2 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 M, respectively. Combinations of any two or more of these upper and / or lower concentrations are also possible, for example, the oxide species and metal dopant species may be provided in the aqueous solution at a concentration of about 0.01-0.05, or 0.01-0.1 M, respectively. In some embodiments, the oxide species and metal dopant species may be provided in the aqueous solution at a concentration of about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M, respectively.

[0115] In some embodiments, the cerium metal species and the metal dopant species may be provided in an aqueous solution at a concentration of at least about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M, respectively. In some embodiments, the cerium metal species and the metal dopant species may be provided in an aqueous solution at a concentration of less than about 1.0, 0.5, 0.4, 0.3, 0.2 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 M, respectively. Combinations of any two or more of these upper and / or lower concentrations are also possible, for example, the cerium metal species and the metal dopant species may be provided in the aqueous solution at a concentration of about 0.01-0.05, or 0.01-0.1 M, respectively. In some embodiments, the cerium metal species and the metal dopant species may be provided in the aqueous solution at a concentration of about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M, respectively.

[0116] In some embodiments, the metal species may be provided in an aqueous solution at a concentration of at least about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M. The concentration may be selected based on the desired w / w% metal in the final hybrid electrode particles. In some embodiments, the metal species may be provided in an aqueous solution at a concentration of less than about 1.0, 0.5, 0.4, 0.3, 0.2 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 M. Combinations of any two or more of these upper and / or lower concentrations are also possible, for example, the metal species may be provided in an aqueous solution at a concentration of about 0.01 to 0.1 M.

[0117] In some embodiments, the silver metal species may be provided in an aqueous solution at a concentration of at least about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M. The concentration may be selected based on the desired w / w% silver in the final hybrid electrode particles. In some embodiments, the silver metal species may be provided in an aqueous solution at a concentration of less than about 1.0, 0.5, 0.4, 0.3, 0.2 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 M. Combinations of any two or more of these upper and / or lower concentrations are also possible, for example, the silver metal species may be provided in an aqueous solution at a concentration of about 0.01 to 0.1 M.

[0118] In some embodiments, the molar ratio of metal species to oxide species may be at least about 1:10, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, or 10:1. In some embodiments, the molar ratio of metal species to oxide species may be less than about 10:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or 1:10. Combinations of any two or more of these upper and / or lower ratios are also possible, for example, the molar ratio of metal species to oxide species may be from about 1:5 to about 5:1, or from about 1:2 to about 1:1.

[0119] In some embodiments, the molar ratio of silver metal species to cerium metal species may be at least about 1:10, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, or 10:1. In some embodiments, the molar ratio of silver metal species to cerium metal species may be less than about 10:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, or 1:10. Combinations of any two or more of these upper and / or lower ratios are also possible, for example, the molar ratio of silver metal species to cerium metal species may be from about 1:5 to about 5:1, or from about 1:2 to about 1:1.

[0120] The inventors have found that the ratio of metal species to oxide species is important to control the amount of ion or mixed ion conducting oxide present in the hybrid electrode particles. Specifically, according to at least some embodiments or examples, it is advantageous to retain at least a portion of the surface of the metal particle free of oxide particles to allow interaction with the metal surface on adjacent hybrid electrode particles, thus providing other portions of electronic conduction that provide a large number of oxide particles. The inventors have unexpectedly determined that a ratio of metal to oxide species of about 2:1 to 1:1 can provide both an enhanced level of oxide decoration while retaining sufficient area of ​​the metal particle surface free for interaction with the metal surface on adjacent particles.

[0121] The inventors have found that the ratio of silver to metal species is important to control the amount of ceria present in the hybrid electrode particles. Specifically, according to at least some embodiments or examples, it is advantageous to retain at least a portion of the surface of the silver particles free of ceria to allow for interaction with the silver surfaces on adjacent hybrid electrode particles, thus providing other portions of electronic conduction that provide multiple ceria particles. The inventors have unexpectedly determined that a ratio of silver to metal species of about 2:1 to 1:1 can provide both an improved level of ceria decoration while retaining sufficient area of ​​the silver particle surface free for interaction with the silver surfaces on adjacent particles. For example, electrodes prepared with 70 wt. % silver and 30 wt. % mixed ionically conductive phase exhibited higher performance, as shown in at least one of the examples provided herein.

[0122] In some embodiments, the molar ratio of metal dopant species to oxide species is at least about 1:100, 1:80, 1:50, 1:20, 1:10, 1:5, or 1:1. In some embodiments, the molar ratio of metal dopant species to oxide species is less than about 1:1, 1:5, 1:10, 1:20, 1:50, 1:80, or 1:100. Combinations of any two or more of these upper and / or lower ratios are also possible, for example, the molar ratio of metal dopant species to oxide species may be from about 1:50 to 1:1. In some embodiments, the molar ratio of metal dopant species to oxide species is about 1:100, 1:80, 1:50, 1:20, 1:10, 1:5, or 1:1.

[0123] In some embodiments, the molar ratio of the metal dopant species to the cerium metal species is at least about 1:100, 1:80, 1:50, 1:20, 1:10, 1:5, or 1:1. In some embodiments, the molar ratio of the metal dopant species to the cerium metal species is less than about 1:1, 1:5, 1:10, 1:20, 1:50, 1:80, or 1:100. Combinations of any two or more of these upper and / or lower ratios are also possible, for example, the molar ratio of the metal dopant species to the cerium metal species may be from about 1:50 to 1:1. In some embodiments, the molar ratio of the metal dopant species to the cerium metal species is about 1:100, 1:80, 1:50, 1:20, 1:10, 1:5, or 1:1.

[0124] Chelating Agents The chelating agent may be any suitable compound that can coordinate to the silver metal species, the cerium metal species, and / or the metal dopant species while providing one or more functional groups that can crosslink with the plasticizer (e.g., via esterification) to create a gel comprising the silver metal species, the cerium metal species, and the metal dopant species. In one embodiment, the same chelating agent is used to separately chelate each of the silver metal species, the cerium metal species, and the metal dopant species. Alternatively, different chelating agents may be used, which may be selected based on their chelating affinity for one or more metal species.

[0125] In some embodiments, the chelating agent is selected from carboxylic acids, amines, amino acids, aminopolycarboxylic acids, diesters, β-diketones, β-ketoesters, and any combination thereof. Suitable carboxylic acids include di-, tri-, or tetracarboxylic acids (e.g., compounds containing 2, 3, or 4 carboxylic acid groups), including, for example, citric acid, lactic acid, glycolic acid, malonic acid, tartaric acid, succinic acid, glutaric acid, or malic acid, and any combination thereof. Suitable amino acids include glycine, methionine, lysine, or glycine, and any combination thereof. Suitable aminopolycarboxylic acids include ethylenediaminetetraacetic acid (EDTA), iminodiacetic acid (IDA), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), or 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), and any combination thereof. In one embodiment, the chelating agent is selected from citric acid, glycine, or EDTA, and any combination thereof. In particular, citric acid and EDTA have been found to be particularly effective chelating agents for forming hybrid electrode particles.

[0126] In some embodiments, the molar ratio of chelating agent to metal species (e.g., silver metal species, cerium metal species, and metal dopant species) present in the aqueous solution is at least about 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, or 5:1. In some embodiments, the molar ratio of chelating agent to metal species in the aqueous solution is less than about 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, or 1:5. Combinations of any two or more of these upper and / or lower ratios are also possible, for example, the molar ratio of chelating agent to metal species present in the aqueous solution can be from about 1:5 to about 5:1, or from about 1:2 to about 2:1. The inventors have found that a ratio of chelating agent to metal species present in the aqueous solution of about 1:1 to 1:5, e.g., 1:2, can provide additional advantages such as forming a stable aqueous chelation solution with the metal species, which can result in a stable solution with minimal or no precipitation being observed.

[0127] Plasticizer To form a gel in step a), the chelating agent is chelated to the metal species and then crosslinked with the plasticizer to form a covalently linked network tail structure in the form of a gel, for example, via esterification. One or more advantages are associated with forming a gel as described herein, including stabilizing and immobilizing the metal species to prevent dissociation, allowing the synthesis of homogeneous doped metal oxides (e.g., gadolinium-doped ceria). Thus, the plasticizer can be any suitable compound capable of crosslinking the chelate in aqueous solution. Crosslinking can occur via any suitable reaction between the functional groups on the chelating agent and the plasticizer, for example, esterification (e.g., polyalcohols and carboxylic acids) or amidation (amines and carboxylic acids).

[0128] In one embodiment, the plasticizer may be a polyol (i.e., a polyalcohol). The plasticizer may be a glycol. Suitable glycols include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, and triethylene glycol, and combinations thereof. In one embodiment, the plasticizer is selected from ethylene glycol, diethylene glycol, and triethylene glycol, and mixtures thereof. According to some embodiments or examples, the inventors have found that glycol plasticizers readily form gels with carboxylic acid chelators (e.g., citric acid) via esterification to form stable gels containing one or more metal species as described herein, as highlighted by the following examples (Image taken from Dimesso L. (2018) Pechini Processes: An Alternate Approach of the Sol-Gel Method, Preparation, Properties, and Applications. In: Klein L., Aparicio M., Jitianu A. (eds) Handbook of Sol-Gel Science and Technology. Springer, Cham. https: / / doi.org / 10.1007 / 978-3-319-32101-1_123). [ka]

[0129] In some embodiments, the molar ratio of plasticizer to metal species (e.g., silver metal species, cerium metal species, and metal dopant species) present in the aqueous solution is at least about 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, or 8:1. In some embodiments, the molar ratio of plasticizer to metal species in the aqueous solution is less than about 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, or 1:5. Combinations of any two or more of these upper and / or lower ratios are also possible, for example, the molar ratio of plasticizer to metal species in the aqueous solution can be from about 1:1 to about 6:1, from about 1:1 to about 4:1. In some embodiments, the molar ratio of plasticizer to metal species present in the aqueous solution is at least about 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, or 8:1. The inventors have found that a ratio of plasticizer to metal species present in the aqueous solution of about 1:1 to 5:1, such as about 2:1 to 4:1, provides an aqueous solution rich in plasticizer that readily crosslinks with the chelating agent to form a stable gel that includes the metal species.

[0130] In some embodiments, the molar ratio of plasticizer to metal species in the aqueous solution is at least about 1:1, 2:1, 3:1, 4:1, or 5:1, e.g., at least about 2:1 (e.g., two plasticizer compounds per chelate).

[0131] Aqueous solutions and gels containing metal species Depending on the degree of cross-linking between the plasticizer and the chelating agent present in the aqueous solution, the aqueous solution in step a) may be viscous but flowable prior to forming a gel. The aqueous solution used to prepare the gel in step a) may be prepared using any suitable aqueous medium, for example, water (e.g., deionized water).

[0132] The pH of the aqueous solution may be adjusted to promote chelation of one or more metal species, control polymerization of the chelating agent and plasticizer, and / or prevent precipitation of one or more metal species. The pH may be controlled by adding any suitable base or acid. For example, a suitable base may be added to the aqueous solution to increase the pH of the aqueous solution to a more basic (i.e., less acidic) pH. Suitable bases may include urea, ammonium hydroxide, or ammonium hydroxide. A suitable acid may be added to the aqueous solution to decrease the pH of the aqueous solution to a more acidic (i.e., less basic) pH. Suitable acids may include nitric acid.

[0133] The pH of the aqueous solution may be adjusted by the addition of a suitable acid or base to achieve a pH of at least about pH 3, 3.5, 4, 4.5, 5, 5.5, 6, or 7. The pH of the aqueous solution may be adjusted by the addition of a suitable acid or base to achieve a pH of less than about pH 7, 6.5, 6, 5.5, 5, 4.5, 4, 3.5, or 3. Combinations of any two or more of these upper and / or lower pH limits are also possible, for example, between about pH 3 and about pH 7.

[0134] A gel may be formed spontaneously from an aqueous solution containing silver metal species, cerium metal species, metal dopant species, a plasticizer, and a chelating agent. For example, polyesterification of excess carboxylic acid groups of the chelating agent by a polyol plasticizer may occur spontaneously in the aqueous solution.

[0135] In some embodiments, the aqueous solution of step a) may be aged at a suitable temperature for a period of time to promote cross-linking between the plasticizer and the chelating agent, for example, to aid in polyesterification to form a gel. In some embodiments, the aqueous solution is aged for a period of at least about 6, 8, 10, 12, 18, 24, 36, or 48 hours to form a gel. The aqueous solution may be aged for a period of less than about 48, 36, 24, 18, 12, 10, 8, or 6 hours to form a gel. Combinations of any two or more of these upper and / or lower aging times are also possible, for example, the aqueous solution is aged for a period of about 12 to 36 hours before forming a gel that provides a uniform structure and phase consistency. In some embodiments, the aqueous solution is aged for a period of about 6, 8, 10, 12, 18, 24, 36, or 48 hours to form a gel. In one embodiment, the aqueous solution may be aged for a period of about 24 to 36 hours before heating in step b).

[0136] In some embodiments, the aqueous solution may be aged to form a gel at a temperature of at least about 60, 65, 70, 75, 80, 85, 90, or 95° C. In some embodiments, the aqueous solution may be aged to form a gel at a temperature less than about 95, 90, 85, 80, 75, 70, 65, or 60° C. Combinations of any two or more of these upper and / or lower aging temperatures are also possible.

[0137] It will be appreciated that combinations of any two or more of the above aging temperature times are also possible, for example, the aqueous solution may be aged at a temperature of about 65°C to 90°C for a period of about 12 hours to 36 hours to form a gel.

[0138] The aging of the aqueous solution in step a) may be a two-step aging process. In one embodiment, the aqueous solution is aged at a first temperature for a period of time effective to promote crosslinking between the plasticizer and the chelating agent (e.g., to aid in polyesterification and / or to remove any residual aqueous solution), and then cooled to a second temperature and aged for a period of time effective to form a gel. For example, the process may include (i) aging the aqueous solution at a first temperature for a period of time effective to promote crosslinking between the plasticizer and the chelating agent (e.g., to aid in polyesterification and / or to remove any residual aqueous solution), and then (ii) cooling to a second temperature and aging at the cooled second temperature for a period of time effective to form a gel.

[0139] For step (i), the aqueous solution may be aged at a temperature of at least about 60, 65, 70, 75, 80, 85, 90, or 95°C. The temperature for aging in step (i) may be lower than about 95, 90, 85, 80, 75, 70, 65, or 60 to form a gel. Combinations of any two or more of these upper and / or lower aging temperatures are also possible, for example, 65°C to 90°C, or about 70°C to 85°C. For step (i), the aqueous solution may be aged for a period of at least about 6, 8, 10, 12, 18, 24, 36, or 48 hours. The aging in step (i) may be for a period of less than about 48, 36, 24, 18, 12, 10, 8, or 6 hours. Combinations of any two or more of these upper and / or lower aging times are also possible, for example, about 12 hours to 36 hours, for example, 24 hours. It will be appreciated that combinations of any two or more of the above aging temperature times are also possible, for example, in step (i), the aqueous solution may be aged at a temperature of about 65°C to 95°C for a period of about 12 hours to 36 hours.

[0140] For step (ii), the aqueous solution may be cooled to a temperature lower than the temperature of aging in step (i). For example, in step (ii), the aqueous solution may be cooled to a temperature of at least about 5, 10, 15, 20, 25, 30, 35, 40, 50, or 60° C. In step (ii), the aqueous solution may be cooled to a temperature lower than about 60, 50, 40, 35, 30, 25, 20, 15, 10, or 5° C. Combinations of any two or more of these upper and / or lower aging temperatures are also possible, for example, about 5° C. to 40° C., or about 10° C. to 30° C., for example, room temperature. In step (ii), the aqueous solution may be aged at the cooled temperature for a period of at least about 2, 4, 6, 8, 10, 12, 18, 24, 36, or 48 hours. The aging in step (i) may be for a period of less than about 48, 36, 24, 18, 12, 10, 8, 6, or 4 hours. Combinations of any two or more of these upper and / or lower aging times are also possible, for example, from about 2 hours to 12 hours, or from about 4 hours to 8 hours. It will be appreciated that combinations of any two or more of the above aging temperature times are also possible, for example, in step (ii), the aqueous solution may be aged at a temperature of about 10° C. to 30° C. for a period of about 4 hours to 8 hours.

[0141] In some embodiments, after step a) but prior to step b), the gel may be aged at a suitable temperature for a period of time prior to heating in step b) to further promote cross-linking between the plasticizer and the chelating agent, e.g., to aid in polyesterification, and / or to remove any residual aqueous solution. It will be understood that this aging step is distinct from heating (e.g., pyrolysis) of the gel in step b) to obtain a powder composition comprising hybrid electrode particles. One or more benefits of aging the gel may further include stabilizing and / or promoting cross-linking between the plasticizer and the chelating agent, and providing a uniform microstructure and / or phase consistency.

[0142] In one embodiment, the aging of the gel prior to step b) is performed at a lower temperature than the heating of the gel in step b) to obtain a powder composition comprising hybrid electrode particles (i.e., an electrode composition as described herein). In some embodiments, the gel formed in step a) is aged for a period of at least about 6, 8, 10, 12, 18, 24, 36, or 48 hours before heating in step b). The gel formed in step a) may be aged for a period of less than about 48, 36, 24, 18, 12, 10, 8, or 6 hours before heating in step b). Combinations of any two or more of these upper and / or lower aging times are also possible, for example, the gel formed in step a) is aged for a period of about 12 hours to 48 hours, or about 24 hours to 48 hours before heating in step b). In some embodiments, the gel formed in step a) is aged for a period of about 6, 8, 10, 12, 18, 24, 36, or 48 hours before heating in step b). In one embodiment, the gel formed in step a) may be aged for a period of about 24 to 48 hours prior to heating in step b).

[0143] In some embodiments, the gel formed in step a) may be aged at a temperature of at least about 60, 65, 70, 75, 80, 85, 90, or 95° C. before heating in step b). In some embodiments, the gel formed in step a) may be aged at a temperature lower than about 95, 90, 85, 80, 75, 70, 65, or 60° C. before heating in step b). Combinations of any two or more of these upper and / or lower aging temperatures are also possible, for example, the gel formed in step a) is aged at a temperature of about 65° C. to 90° C., or about 70° C. to 85° C. before heating in step b). In some embodiments, the gel formed in step a) may be aged at a temperature of about 60, 65, 70, 75, 80, 85, 90, or 95° C. before heating in step b). It will be appreciated that combinations of any two or more of the above aging temperature times are also possible, for example the gel formed in step a) may be aged at a temperature of about 60°C to 90°C for a period of about 12 hours to 36 hours prior to heating in step b).

[0144] The aging described above can be carried out using any conventional oven, such as a laboratory drying oven or a convection oven. In one embodiment, the aging is carried out by drying (e.g., in a laboratory drying oven or a convection oven).

[0145] In one embodiment, step a) comprises preparing an aqueous solution comprising the oxide species and the metal dopant species, followed by adding a chelating agent, a plasticizer and then the metal species to the aqueous solution.

[0146] In one embodiment, step a) comprises preparing an aqueous solution comprising cerium metal species and metal dopant species, followed by adding a chelating agent, a plasticizer, and then adding silver metal species to the aqueous solution.

[0147] In a further embodiment, the aqueous solution containing the oxide species, metal dopant species, chelating agent and plasticizer is aged prior to the addition of the metal species. In a further embodiment, the aqueous solution containing the cerium metal species, metal dopant species, chelating agent and plasticizer is aged prior to the addition of the silver metal species. This aging step may be carried out at any temperature and for a period of time as described above for the gel, for example, the aqueous solution is aged at a temperature of about 65° C.-90° C., or about 70° C.-85° C. for 12 hours-36 hours prior to the addition of the silver metal species. This forms an intermediate gel / viscous aqueous solution prior to the addition of the metal species (e.g., silver). Alternatively, the metal species is added to the aqueous solution prior to the optional aging step.

[0148] The metal species may be added as an aqueous solution to the aqueous solution containing the oxide species, the metal dopant species, the chelating agent, and the plasticizer. The silver metal species may be added as an aqueous solution to the aqueous solution containing the cerium metal species, the metal dopant species, the chelating agent, and the plasticizer. The aqueous solution containing the metal species may be added dropwise to the aqueous solution containing the oxide species, the metal dopant species, the chelating agent, and the plasticizer. The aqueous solution containing the silver metal species may be added dropwise to the aqueous solution containing the cerium metal species, the metal dopant species, the chelating agent, and the plasticizer. In some embodiments, the metal species may be provided in an aqueous solution at a concentration of at least about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M. In some embodiments, the metal species may be provided in an aqueous solution at a concentration of less than about 1.0, 0.5, 0.4, 0.3, 0.2 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 M. Combinations of any two or more of these upper and / or lower concentrations are also possible, for example, the metal species may be provided in an aqueous solution at a concentration of about 0.01-0.1 M. In some embodiments, the silver metal species may be provided in an aqueous solution at a concentration of at least about 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, or 1.0 M. In some embodiments, the silver metal species may be provided in an aqueous solution at a concentration of less than about 1.0, 0.5, 0.4, 0.3, 0.2 0.1, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01 M. Combinations of any two or more of these upper and / or lower concentrations are also possible, for example, the silver metal species may be provided in an aqueous solution at a concentration of about 0.01-0.1 M.

[0149] The aqueous solution containing the metal species may be added to the aqueous solution containing the oxide species, the metal dopant species, the chelating agent and the plasticizer at a temperature of at least 50, 60, 70, 80, 90 or 100° C., for example, from about 60° C. to 90° C. or from 70° C. to 85° C. The aqueous solution containing the metal species may be added to the aqueous solution containing the oxide species, the metal dopant species, the chelating agent and the plasticizer while stirring at a speed of at least 100, 200, 300, 400 or 500 rpm, for example, from about 300 to 500 rpm.

[0150] The aqueous solution containing silver metal species may be added to the aqueous solution containing cerium metal species, metal dopant species, chelating agent and plasticizer at a temperature of at least 50, 60, 70, 80, 90 or 100° C., for example, from about 60° C. to 90° C. or from 70° C. to 85° C. The aqueous solution containing silver metal species may be added to the aqueous solution containing cerium metal species, metal dopant species, chelating agent and plasticizer while stirring at a speed of at least 100, 200, 300, 400 or 500 rpm, for example, from about 300 to 500 rpm.

[0151] Heating the gel to obtain hybrid electrode particles The gel is heated in step b) to obtain a powder composition comprising the hybrid electrode particles (i.e., an electrode composition as described herein). This heating step essentially pyrolyzes the gel (i.e., the precursor material comprising the chelated metal species immobilized as a gel) to burn off and remove (e.g., pyrolyze) the organic components of the gel to obtain a powder composition comprising the hybrid electrode particles.

[0152] Depending on whether the gel is aged and the aqueous solution is removed prior to heating in step b), the gel may be a viscous liquid or a stiff gel, it will be understood that both physical states are still considered a gel for purposes of this disclosure.

[0153] The gel of step b) may be heated to a suitable temperature effective to pyrolyze the organic components of the gel to obtain a powder composition of hybrid electrode particles. In some embodiments, the gel is heated in step b) at a temperature of at least about 300, 350, 400, 450, 500, 550, 600, 650, or 700° C. The gel may be heated in step b) at a temperature lower than about 700, 650, 600, 550, 500, 450, 400, 350, or 300° C. Combinations of any two or more of these upper and / or lower temperature limits are also possible, for example, the gel is heated in step b) at a temperature between about 300° C. and about 450° C. In one embodiment, the gel is heated in step b) at a temperature of about 300, 350, 400, 450, or 500° C., for example, about 450° C. Any suitable heating rate may be used, for example, at least or about 100, 120, 140, 150, 170, 180, 200, or 250° C. / hour. In some embodiments, the gel is heated in step b) for a period of at least about 10, 15, 30, 45 minutes, 1, 2, 3, 4, 5, 6, 12, 24, 36, or 48 hours. In some embodiments, the gel is heated in step b) for a period of less than about 48, 36, 24, 12, 6, 5, 4, 3, 2, 1 hour, 45, 30, 15, or 10 minutes. The gel may be heated for a period in the range provided by any two of these upper and / or lower limits, for example, from about 1 hour to about 24 hours, for example, from about 1 hour to about 10 hours, for example, from about 2 hours to about 4 hours. Any combination of one or more of the above mentioned temperatures and times are possible, for example the gel may be heated in step b) at a temperature of about 300° C. to 600° C. for a period of about 2 hours to 4 hours.

[0154] Heating (e.g., pyrolysis) may be performed using a suitable oven or hot plate. Alternatively, heating may be performed using spray pyrolysis or spray drying of the gel. It will be appreciated that if spray pyrolysis of the gel is desired, it is not necessary to age the gel to remove the aqueous solution prior to any pyrolysis, as the gel needs to remain flowable for spray pyrolysis / drying.

[0155] In some embodiments, the gel prepared in step a) may be deposited (e.g., by spin coating, dip coating, etc.) on a suitable substrate, followed by heat treatment to decompose the organic components and form a powder composition layer comprising the hybrid electrode particles on the substrate.

[0156] The powder composition may be an amorphous, semi-crystalline, or crystalline powder composition. For example, the hybrid electrode particles may be amorphous, semi-crystalline, or crystalline. In one embodiment, the powder composition is an amorphous powder composition comprising hybrid electrode particles.

[0157] In some embodiments, powder compositions comprising the hybrid electrode particles, i.e., the electrode compositions described herein, can be further processed into dry powder formulations comprising one or more solvents or into wet coating formulations, which can be dip coating formulations or printable ink formulations as described herein.

[0158] Sintered powder composition or blend thereof The powder composition comprising the hybrid electrode particles or its coating formulation may be sintered to form the sintered electrode material described herein. In one embodiment, sintering comprises heating the powder composition comprising the hybrid electrode particles or the coating formulation to a temperature effective to cause the metal particles of the hybrid electrode particles to coalesce and adhere to each other to form a continuous or semi-continuous metal phase. After sintering to form the metal phase (i.e., a scaffold comprising a porous silver metal phase), the metal-doped oxide particles (e.g., metal-doped ceria particles) may remain as separate particles connected to the surface of the metal phase (e.g., silver) and / or may attach to other metal-doped oxide particles (e.g., metal-doped ceria particles) to form one or more separate metal-doped oxide phases (e.g., moieties) connected to the surface of the metal phase (e.g., silver). The sintered electrode material comprises a metal phase (e.g., silver) as a porous scaffold and a plurality of separate metal-doped oxide phases (e.g., metal-doped ceria particles) interspersed within the metal phase (e.g., silver).

[0159] In one embodiment, the sintering is at a temperature (in °C) of about 100 to about 900. In one embodiment, the sintering is at a temperature (in °C) of at least about 100, 200, 300, 400, 500, 700, or 900. In one embodiment, the sintering is at a temperature (in °C) of less than about 900, 700, 500, 400, 300, 200, or 100. The sintering temperature can be in a range provided by any two of these upper and / or lower limits, for example, from about 400 °C to about 900 °C.

[0160] In one embodiment, the sintering is at a heating rate (in °C / hour) of about 50-300, about 100-200, or about 150-180. The sintering can be at a heating rate (in °C / hour) of at least about 50, 70, 100, 120, 150, 180, 200, 250, or 300. The sintering can be at a heating rate (in °C / hour) of less than about 300, 250, 200, 180, 150, 120, 100, 70, or 50. The sintering heating rate can be in a range provided by any two of these upper and / or lower limits. The sintering can be carried out using any suitable equipment, such as a sintering furnace, or a high temperature furnace or oven.

[0161] In one embodiment, the process further includes manufacturing an electrode. For example, an electrode can be manufactured using the powder composition or sintered electrode material thereof. The electrode can be used in a solid oxide electrolysis cell or a solid oxide fuel cell.

[0162] In one embodiment, the process further includes preparing a solid oxide electrochemical cell including an electrode comprising the powder composition or sintered electrode material thereof. The solid oxide electrochemical cell may include a positive electrode and a negative electrode each comprising the powder composition or sintered electrode material thereof. For example, the powder composition or sintered electrode material thereof may be used as both a positive electrode and a negative electrode, for example, to form a symmetrical and reversible solid oxide electrochemical cell. This allows for faster manufacturing of the solid oxide electrochemical cell, since both the positive electrode and the negative electrode can be heat treated (e.g., sintered) simultaneously when preparing the solid oxide electrochemical cell. The heat treatment may also be at a lower temperature than conventional processes used to prepare conventional electrodes for solid oxide electrochemical cells. A method of manufacturing a solid oxide electrochemical cell is described below.

[0163] Electrodes and solid oxide electrochemical cells The present disclosure also provides an electrode comprising an electrode composition comprising the hybrid electrode particles described herein or a sintered electrode material thereof, which can be used as an electrode in a solid oxide electrochemical cell.

[0164] The present disclosure also provides an electrode comprising the electrode composition described herein or a sintered electrode material thereof, which can be used as an electrode in a solid oxide electrochemical cell. The general components of a solid oxide electrochemical cell are well known and understood in the art of the present disclosure. A solid oxide electrochemical cell comprises: A positive electrode and A negative electrode; a solid electrolyte in solid communication with the positive electrode and the negative electrode; and an electrical circuit connecting the positive and negative electrodes.

[0165] The positive electrode may also be referred to as the anode, and the negative electrode may also be referred to as the cathode. These electrodes function as either the cathode or the anode, depending on whether the solid oxide electrochemical cell is operating in a regenerative mode (e.g., in the case of a solid oxide electrolysis cell (SOEC)) or in an energy production mode (e.g., in the case of a solid oxide fuel cell (SOFC)).

[0166] In one embodiment, the solid oxide electrochemical cell can be a solid oxide electrolysis cell (SOEC). The basic operation of a solid oxide electrolysis cell is described as follows: Input streams (e.g., CO2 and HO) flow into the cell via an inlet and into the anode (e.g., fuel electrode or cathode). When a voltage is applied, the input streams (e.g., CO2 and HO) are reduced in the anode (e.g., syngas: CO and H2) to mobile oxygen species, e.g., oxygen ions (O 2- ) flows toward the solid oxide electrolyte. The oxygen ions migrate through the solid oxide electrolyte to the positive electrode (e.g., oxygen electrode or anode), where they are oxidized to molecular oxygen (O2) and electrons (e - These electrons flow in an electrical circuit from the positive electrode (i.e., anode) back to the negative electrode (i.e., cathode), which uses the electrons to reduce oxygen atoms and start the process all over again.

[0167] It has been found that the SOEC, as described herein, can generate fuel gas directly without the need for any additional reducing gas, such as H2 or CO, in the feed stream. State of the art / conventional materials require an additional supply of reducing gas during start-up and shutdown to prevent oxidation of the cathode, e.g., nickel to nickel oxide, which results in performance degradation. Advantageously, as described herein, no additional reducing gas is required to maintain the metallic nature of the hybrid electrode, since the electrode composition or sintered electrode material is efficient and stable in both oxidizing and reducing environments. Additionally, the hybrid electrodes described herein require less electrical energy per unit volume of hydrogen or carbon monoxide, or a mixture of both (syngas), compared to conventional Ni-YSZ electrodes.

[0168] In an alternative embodiment, the solid oxide electrochemical cell can be a solid oxide fuel cell (SOFC). A SOFC is an SOEC that works in reverse, producing electricity directly by oxidizing a fuel. The basic operation of a solid oxide fuel cell is described as follows: Air flows into the cell via an inlet. As air flows through the negative electrode (e.g., oxygen electrode or cathode), oxygen atoms are reduced in the cathode to produce oxygen ions (O 2- ), which flows toward the solid oxide electrolyte. The oxygen ions migrate through the solid oxide electrolyte into the positive electrode (e.g., fuel electrode or anode), where they then react with a fuel source (e.g., hydrogen gas). The reaction of the oxygen ions with hydrogen gas at the positive electrode produces HO and electrons (e - These electrons flow into an electronic circuit from the positive electrode (i.e., the anode) and back to the negative electrode (i.e., the cathode). The electronic circuit uses the flow of electrons to power the device, and the negative electrode uses the electrons to reduce oxygen atoms and start the process all over again.

[0169] One or more advantages of the present disclosure according to at least some embodiments or examples described herein is that the same electrode composition or sintered electrode material thereof can be used for both the positive and negative electrodes in a solid oxide electrochemical cell, for example, reducing the time and cost of SOEC / SOFC manufacturing. It will be understood that typically, different materials are used to manufacture the negative electrodes (e.g., nickel-YSZ composites) and positive electrodes (e.g., LSM-YSZ composites) for state-of-the-art solid oxide electrolysis cells. Thus, the temperatures used for heat treatment during the manufacturing process are different when two different materials are used, and a two-step process is required in which the negative electrodes are typically manufactured using a heat treatment at 1500°C, followed by the positive electrodes, typically at 900°C to 1100°C. In contrast, one advantage of using the same material for both the positive and negative electrodes is that the electrodes can be manufactured in a single step.

[0170] Advantageously, as described above, the same electrode composition or sintered electrode material thereof can be used for both the positive and negative electrodes, which is one of the major limitations of existing SOE technology. In addition, the electrode composition or sintered electrode material thereof described herein has been unexpectedly found to be less susceptible to degradation issues due to its stability in both fuel and oxidizing environments, and therefore can be used in multiple heterogeneous applications.

[0171] It will be appreciated that this approach can also reduce the operating temperature of the solid oxide cell for a desired conversion rate and reduce the overall volume and cost of solid oxide cell manufacture. Also, due to the advantageous symmetric cell configuration, the manufacturing / capital costs and time of the solid oxide cell can be significantly reduced.

[0172] In some embodiments, the solid oxide electrochemical cell is a tubular solid oxide electrochemical cell. Some additional advantages of the present disclosure according to at least some embodiments or examples described herein are that the tubular cell structure may provide increased durability, extended life, and improved performance while allowing integration with intermittent renewable energy sources compared to planar cell structures. For example, during use, the tubular cell structure of the SOEC can advantageously provide improved heat dissipation (e.g., the electrolyzer can be brought up to temperature in less than 30 minutes) and can be effectively used in temporary power management schemes to convert excess electricity production, for example, to hydrogen.

[0173] In some embodiments, the electrode composition or sintered electrode material thereof can be used as a positive electrode and / or a negative electrode in a solid oxide electrochemical cell. In one embodiment, the electrode composition or sintered electrode material thereof can be used as both a positive electrode and a negative electrode in a solid oxide electrochemical cell.

[0174] Accordingly, the present disclosure also provides a solid oxide electrochemical cell comprising a cathode, a solid oxide electrolyte, and an anode, wherein the cathode and / or the anode comprise an electrode composition described herein, or a sintered electrode material thereof described herein.

[0175] electrode composition In some embodiments, the positive or negative electrode comprises the electrode composition described herein or a sintered electrode material thereof. For example, the positive and negative electrodes are the same electrode material. It will be understood that such an arrangement is referred to as a symmetric solid oxide electrochemical cell. The sintered electrode material may be produced by heating (e.g., calcining) an electrode composition including the hybrid electrode particles such that the metal particles (e.g., silver) of the hybrid electrode particles coalesce and adhere to each other to form a continuous or semi-continuous metal-metal phase (e.g., silver) within the electrode material.

[0176] The metal phase may include at least one metal particle selected from silver (Ag), iron (Fe), nickel (Ni), and cobalt (Co). In some embodiments, the metal phase may include a combination of silver (Ag) particles and one or more of iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), and titanium (Ti). The silver metal phase may include one or more silver metal moieties. In some embodiments, the metal phase is a porous scaffold. In some embodiments, the silver metal phase is a porous scaffold. In some embodiments, the sintered electrode material includes a metal phase as a porous scaffold and a plurality of separate metal-doped oxide phases interspersed within the metal phase. The separate metal-doped oxide phases may be in the form of metal-doped oxide particles described herein. The separate metal-doped oxide phases (e.g., particles or moieties) may be interspersed within the metal phase. In one embodiment, the sintered electrode material includes a silver metal phase as a porous scaffold and a plurality of separate metal-doped ceria phases interspersed within the silver metal phase. The separate metal-doped ceria phases may be in the form of metal-doped ceria particles as described herein. The separate metal-doped ceria phases (e.g., particles or moieties) may be interspersed within the silver metal phase. The sintered electrode material of the cathode and / or anode may be a sintered electrode material as described herein with respect to the electrode composition. The electrode composition or the sintered electrode material may be a coating on an electrode support.

[0177] positive electrode The positive electrode may also be referred to as the anode. When used in a SOEC, the anode may also be referred to as the oxygen electrode. When used in a SOFC, the anode may also be referred to as the fuel electrode. In some embodiments, the electrode composition or sintered electrode material thereof may be used as the positive electrode. Alternatively, according to some embodiments or examples, when the electrode composition or sintered electrode material thereof is used as the negative electrode, any conventional electrode material used in solid oxide electrochemical cells may be used as the positive electrode. The positive electrode may be porous to provide a uniform flow of oxygen throughout the electrode. The positive electrode may also be a porous material that contains oxide ions (O 2-The material may be any suitable material capable of conducting a current through the solid oxide electrolyte.

[0178] In some embodiments, when the negative electrode comprises the electrode composition or a sintered electrode material thereof, the positive electrode may be selected from lanthanum strontium manganite (LSM), lanthanum strontium cobalt ferrite (LSCF), strontium samarium cobalt oxide (SSC), lanthanum strontium iron oxide (LSF), lanthanum strontium cobalt oxide (LSCO), barium strontium cobalt iron oxide (BSCF), or combinations thereof, and may also be selected from yttria stabilized zirconia (YSZ), scandia stabilized zirconia (SSZ), gadolinia doped ceria (GDC), samaria doped ceria (SDC), samaria-neodymium doped ceria (SNDC), erbia stabilized bismuth oxide (ESB), yttria stabilized bismuth oxide (YSB), strontium or magnesium doped lanthanum gallate (LSGM) composites thereof. In one embodiment, the positive electrode comprises an electrode composition described herein or a sintered electrode material thereof.

[0179] negative electrode The negative electrode may also be referred to as the cathode. When used in a SOEC, the cathode may also be referred to as the fuel electrode. When used in a SOFC, the cathode may also be referred to as the oxygen electrode. In some embodiments, the electrode composition or sintered electrode material thereof may be used as the negative electrode. Alternatively, according to some embodiments or examples, when the electrode composition or sintered electrode material is used as the positive electrode, any conventional electrode material used in solid oxide electrochemical cells may be used as the negative electrode. The negative electrode may be a porous layer that allows fuel / reactant gases to flow through the electrode, and in some embodiments, is both electrically and ionically conductive.

[0180] In some embodiments, when the positive electrode comprises the electrode composition or its sintered electrode material, the negative electrode may comprise a combination of ceramic and metal (cermet) prepared by standard ceramic processing techniques. Non-limiting examples of cermets that may be used as the negative electrode include nickel-yttria stabilized zirconia (Ni-YSZ), nickel-gadolinium doped ceria (Ni-GDC), nickel-yttria doped ceria zirconia (Ni-YDCZ), and copper-ceria-yttria doped zirconia (Cu-CeO2-YSZ). Other suitable negative electrode materials Lanthanum strontium manganese chromium oxide (LSCM), lanthanum strontium ferrite (LSF), lanthanum strontium titanate (LST) and vanadate (LSV). In one embodiment, the negative electrode comprises the electrode composition described herein or its sintered electrode material.

[0181] Solid Oxide Electrolyte The solid oxide electrolyte may be selected from any conventionally known electrolyte capable of diffusing oxygen ions between the cathode and anode of a solid oxide electrochemical cell. Examples of suitable solid oxide electrolytes include, but are not limited to, yttria-stabilized zirconia (YSZ), scandia-stabilized zirconia (SSZ), gadolinia-doped ceria (GDC), samaria-doped ceria (SDC), samaria-neodymium-doped ceria (SNDC), erbia-stabilized bismuth oxide (ESB), yttria-stabilized bismuth oxide (YSB), strontium- or magnesium-doped lanthanum gallate (LSGM), and combinations thereof. In one embodiment, the solid oxide electrolyte is yttria-stabilized zirconia (YSZ). The solid oxide electrolyte may also be provided as one or more layers, each layer being independently selected from the solid oxide electrolytes described above.

[0182] Additional components The solid oxide electrochemical cell may include one or more additional components, including current collectors (e.g., silver paste, platinum paste, silver mesh, silver wire, and platinum mesh), power sources, and / or interconnects. It will be understood that other additional components may be present as would be understood by one of ordinary skill in the art.

[0183] Purpose In one embodiment, the solid oxide electrochemical cell is a solid oxide electrolysis cell (SOEC) configured for the synthesis of one or more of oxygen, hydrogen, carbon monoxide, or syngas.

[0184] In one embodiment, the solid oxide electrochemical cell is a solid oxide fuel cell (SOFC) for converting chemical energy from one of many of the following: hydrogen, ammonia, hydrocarbons (e.g., methane), natural gas, alcohol (e.g., methanol or ethanol), syngas, solid carbon, and biomass SOFCs into electrical energy and / or thermal energy.

[0185] The present disclosure also provides the use of an electrode composition described herein, or a sintered electrode material thereof, in preparing an electrode or electrode material for a solid oxide electrochemical cell described herein.

[0186] In some embodiments, an electrode comprising the electrode composition described herein or a sintered electrode material thereof, or a solid oxide electrochemical cell described herein, may have a low electrode polarization resistance. In some embodiments, the electrode polarization resistance (Ohms-cm at an applied potential of 1.2 volts) may be 2 ) may be less than about 0.5, 0.4, 0.3, 0.2, 0.1, 0.05, or 0.01. Electrode polarization resistance (Ohms-cm at an applied potential of 1.2 volts 2 ) may be greater than about 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5. Combinations of these values ​​are also possible, for example, about 0.01-0.5, 0.05-0.4, or 0.1-0.3. The electrode polarization resistance may be less than about 0.2. The electrode polarization resistance may be measured using ASTM G59-97.

[0187] In some embodiments, electrodes comprising the electrode compositions described herein or sintered electrode materials thereof, for example when used as positive and negative electrodes in a symmetric cell, facilitate the electrolysis of steam and / or carbon dioxide to produce hydrogen and / or carbon monoxide. In other embodiments, electrodes comprising the electrode compositions described herein or sintered electrode materials thereof can be applied in solid oxide electrolysis systems for ammonia synthesis and one-step methane synthesis.

[0188] Electrochemical cells (e.g., solid oxide electrochemical cells) fabricated using electrodes including the electrode compositions described herein or sintered electrode materials thereof can exhibit enhanced performance and / or improved stability, according to at least some examples or embodiments described herein.

[0189] In some embodiments, electrochemical cells fabricated using electrodes comprising the electrode compositions described herein or sintered electrode materials thereof can maintain performance for at least 100, 200, 300, 400, or 500 redox cycles, highlighting enhanced performance and / or improved stability of the electrochemical cell.

[0190] In some embodiments, electrochemical cells fabricated using electrodes including the hybrid electrode particles described herein can have at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40% higher performance than electrochemical cells fabricated using electrodes fabricated by mixing separate ceria and metallic silver particles. Combinations of these values ​​are also possible, for example, to form a range of 5% to 40% higher performance.

[0191] In some embodiments, electrochemical cells fabricated using electrodes comprising the hybrid electrode particles described herein can have at least 5%, 10%, 15%, 20%, 25%, 30%, 35%, or 40% lower electrode polarization resistance compared to electrochemical cells fabricated using electrodes fabricated by mixing separate ceria and metallic silver particles. Combinations of these values ​​are also possible, for example, to form a range of 25% to 40% lower electrode polarization resistance. Lower electrode polarization provides improved kinetics and performance.

[0192] Method for making an electrochemical cell The present disclosure also provides methods of making an electrochemical cell comprising an electrode composition comprising the hybrid electrode particles described herein, or at least one electrode comprising the sintered electrode material described herein.

[0193] In one embodiment, there is provided a method of manufacturing a solid oxide electrochemical cell, comprising the steps of: a) preparing one or more solid oxide electrolyte layers; b) applying an electrode composition to one or both sides of a solid oxide electrolyte layer to form a component of a solid oxide electrochemical cell, wherein the electrode composition applied to at least one side of the solid oxide electrolyte layer comprises an electrode composition described herein; and c) sintering the electrode composition applied onto a component of the solid oxide electrochemical cell to form an electrode or electrode material.

[0194] In one embodiment, step b) includes applying an electrode composition to both sides of the solid oxide electrolyte layer. Any suitable process can be used to apply the electrode composition to the solid oxide electrolyte layer, for example, by dip-coating the solid oxide electrolyte layer in a wet coating formulation including the electrode composition to coat both sides of the layer with the electrode composition to form a positive electrode and a negative electrode on the solid oxide electrolyte layer, respectively.

[0195] Sintering of the solid oxide electrochemical cell components including the electrode composition may be carried out as described herein in connection with sintering of the electrode composition.

[0196] In another embodiment, there is provided a method of manufacturing a solid oxide electrochemical cell, comprising the steps of: a) preparing one or more solid oxide electrolyte layers; and b) applying a sintered electrode material to one or both sides of the solid oxide electrolyte layer to form a component of a solid oxide electrochemical cell, wherein the sintered electrode material applied to at least one side of the solid oxide electrolyte layer comprises a sintered electrode material described herein.

[0197] In one embodiment, the solid oxide electrochemical cell is a symmetric cell comprising a positive electrode and a negative electrode on opposite sides of a solid oxide electrolyte layer, each electrode comprising or consisting of an electrode composition described herein, or a sintered electrode material thereof.

[0198] Any one of the following numbered paragraphs, or any combination of these paragraphs, may provide further embodiments of the disclosure.

[0199] 1. An electrode composition comprising a plurality of hybrid electrode particles, each hybrid electrode particle comprising silver particles having a surface comprising one or more metal-doped ceria particles.

[0200] 2. The electrode composition of any one or more embodiments described herein, wherein the one or more metal-doped ceria particles are decorated on the surface of the silver particles.

[0201] 3. The electrode composition of any one or more of the embodiments described herein, wherein the particle size of the silver particles is larger than the particle size of the metal-doped ceria particles.

[0202] 4. The electrode composition of any one or more of the embodiments described herein, wherein the hybrid electrode particles have a particle size (in μm) of about 0.1 to 5.

[0203] 5. The electrode composition of any one or more of the embodiments described herein, wherein the silver particles of each hybrid electrode particle have a particle size (in μm) of about 0.1 to 3.

[0204] 6. The electrode composition of any one or more embodiments described herein, wherein the metal-doped ceria particles on the surface of the silver particles have a particle size (in nm) of about 1 to 200.

[0205] 7. The electrode composition of any one or more of the embodiments described herein, wherein the metal dopant for the ceria particles is provided by one or more metals selected from rare earth metals and alkaline earth metals.

[0206] 8. The electrode composition of any one or more embodiments described herein, wherein the metal dopant for the ceria particles is provided by one or more metals selected from samarium (Sm), gadolinium (Gd), lanthanum (La), zirconium (Zr), yttrium (Y), ytterbium (Yb), erbium (Er), praseodymium (Pr), or neodymium (Nd).

[0207] 9. The electrode composition of any one or more of the embodiments described herein, wherein the metal dopants for the ceria particles are provided by one or more metals selected from gadolinium (Gd), samarium (Sm), and yttrium (Y).

[0208] 10. The electrode composition of any one or more of the embodiments described herein, wherein the amount of metal dopant in the ceria particles (w / w% based on the total weight of the metal-doped ceria particles) is about 1-35.

[0209] 11. Metal-doped ceria particles are formed of the formula Ce 1-x M x O 2-δwherein x is about 0.01 to 0.3, M is one or more dopants as defined above, and δ is about 0.0 to 0.5.

[0210] 12. The electrode composition of any one or more embodiments described herein, wherein the composition is provided as a coating formulation comprising hybrid electrode particles as a powder present in one or more solvents.

[0211] 13. The electrode composition according to any one or more embodiments described herein, wherein the coating formulation is a dip-coating formulation comprising a powder, one or more organic solvents, and optionally one or more binders.

[0212] 14. The electrode composition according to any one or more embodiments described herein, wherein the coating formulation is a printable ink formulation comprising a powder, one or more organic solvents, and optionally one or more binders.

[0213] 15. The electrode composition of any one or more of the embodiments described herein, wherein the electrode composition is provided as a sintered electrode material.

[0214] 16. The electrode composition of any one or more of the embodiments described herein, wherein the sintered electrode material comprises a silver metal phase as a porous scaffold and a plurality of distinct metal-doped ceria phases interspersed within the silver metal phase.

[0215] 17. The electrode composition of any one or more of the embodiments described herein, wherein the separate metal-doped cerium oxide phase is in the form of metal-doped cerium oxide particles.

[0216] 18. Sintered electrode material is 1 cm 3 The electrode composition of any one or more embodiments described herein, comprising about 10-100 distinct metal-doped ceria phases per silver metal phase.

[0217] 19. The electrode composition of any one or more embodiments described herein, wherein the sintered electrode material has a porosity (in volume percent) of about 10-60, based on the total volume of the sintered electrode material.

[0218] 20. The electrode composition of any one or more of the embodiments described herein, wherein the thickness (in μm) of the sintered electrode material is 1-100.

[0219] 21. A modified sol-gel process for preparing hybrid electrode particles, comprising: a) preparing a gel from an aqueous solution containing silver metal species, cerium metal species, a metal dopant species, a plasticizer, and a chelating agent; b) heating the gel to obtain a powder composition comprising hybrid electrode particles.

[0220] 22. The modified sol-gel process as described in any one or more embodiments described herein, wherein step a) comprises preparing an aqueous solution containing cerium metal species and metal dopant species, followed by adding a chelating agent, a plasticizer to the aqueous solution, and then adding silver metal species.

[0221] 23. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the aqueous solution containing the cerium metal species, the metal dopant species, the chelating agent, and the plasticizer is aged prior to the addition of the silver metal species.

[0222] 24. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein after step a) but before step b), the process comprises aging the gel at a suitable temperature for a period of time against any remaining aqueous solution before heating in step b).

[0223] 25. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the aqueous solution and / or gel is aged at a temperature of about 60° C. to 90° C. for a period of about 12 hours to 36 hours.

[0224] 26. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein one or more of the cerium metal species, the metal dopant species, and the silver metal species are provided as a salt or hydrate thereof independently selected from hydroxides, chlorides, nitrates, and oxide salts.

[0225] 27. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein one or more of the cerium metal species, the metal dopant species, and the silver metal species are provided as a nitrate salt or a hydrate thereof.

[0226] 28. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the cerium metal species and the metal dopant species are each provided in an aqueous solution at a concentration of about 0.01-0.1 M.

[0227] 29. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the silver metal species is provided in an aqueous solution at a concentration of about 0.01-0.1 M.

[0228] 30. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the molar ratio of silver metal species to cerium metal species is about 1:5 to 5:1.

[0229] 31. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the molar ratio of the metal dopant species to the cerium metal species is from about 1:50 to 1:1.

[0230] 32. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the plasticizer is a glycol, preferably selected from ethylene glycol, diethylene glycol, and triethylene glycol.

[0231] 33. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the chelating agent is selected from a carboxylic acid (e.g., citric acid), an amine, an amino acid, an aminopolycarboxylic acid (e.g., EDTA), a diester, a β-diketone, a β-ketoester, and any combination thereof.

[0232] 34. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the molar ratio of chelating agent to silver metal species is about 1:5 to 5:1.

[0233] 35. The modified sol-gel process as described in any one or more embodiments described herein, wherein the gel is heated in step b) at a temperature of about 300° C. to 600° C.

[0234] 36. The modified sol-gel process as described in any one or more embodiments described herein, wherein step b) comprises flame spray pyrolysis or spray drying of the gel obtained from step a) to obtain a powder composition of hybrid electrode particles.

[0235] 37. The modified sol-gel process as described in any one or more embodiments described herein, wherein the powder composition comprising the hybrid electrode particles is further processed into a dry powder formulation or a wet coating formulation comprising one or more solvents.

[0236] 38. The modified sol-gel process as described in any one or more embodiments described herein, wherein the coating formulation is a dip coating formulation comprising one or more solvents.

[0237] 39. The modified sol-gel process as described in any one or more embodiments described herein, wherein the coating formulation is a printable ink formulation comprising a powder, one or more organic solvents, and one or more stabilizers.

[0238] 40. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the powder composition or a blend thereof is sintered into a sintered electrode material.

[0239] 41. The modified sol-gel process as described in any one or more embodiments described herein, wherein the sintering is at a temperature of about 500°C to 900°C.

[0240] 42. The modified sol-gel process as described in any one or more embodiments described herein, wherein the sintered electrode material comprises a silver metal phase as a porous scaffold and a plurality of distinct metal-doped ceria phases interspersed within the silver metal phase.

[0241] 43. The modified sol-gel process as described in any one or more of the embodiments described herein, wherein the electrode is manufactured using the powder composition or a sintered electrode material thereof.

[0242] 44. The modified sol-gel process as described in any one or more embodiments described herein, wherein a solid oxide electrochemical cell is prepared comprising an electrode comprising the powder composition or a sintered electrode material thereof.

[0243] 45. The modified sol-gel process as described in any one or more embodiments described herein, wherein the solid oxide electrochemical cell comprises a positive electrode and a negative electrode each comprising the powder composition or a sintered electrode material thereof.

[0244] 46. ​​An electrode comprising the electrode composition according to any one or more embodiments described herein, or a sintered electrode material thereof.

[0245] 47. A solid oxide electrochemical cell comprising a cathode, a solid oxide electrolyte, and an anode, wherein the cathode and / or the anode comprise an electrode composition according to any one or more embodiments described herein, or a sintered electrode material thereof.

[0246] 48. The electrode or solid oxide electrochemical cell of any one or more of the embodiments described herein, wherein the sintered electrode material of the electrode composition comprises a silver metal phase as a porous scaffold and a plurality of distinct metal-doped ceria phases interspersed within the silver metal phase.

[0247] 49. The electrode or solid oxide electrochemical cell of any one or more embodiments described herein, wherein the separate metal-doped cerium oxide phase is in the form of metal-doped cerium oxide particles.

[0248] 50. The electrode or solid oxide electrochemical cell of any one or more embodiments described herein, wherein the metal-doped cerium oxide particles have a particle size (in μm) of about 1 to 200.

[0249] 51. An electrode or solid oxide electrochemical cell according to any one or more of the embodiments described herein, wherein the electrode composition or the sintered electrode material thereof is coated on an electrode support.

[0250] 52. The electrode or solid oxide electrochemical cell of any one or more embodiments described herein, wherein the sintered electrode material has a porosity (in volume %) of about 10 to 60, based on the total volume of the sintered electrode material.

[0251] 53. Sintered electrode material is 1 cm 3 50-500 distinct metal-doped ceria phases per silver metal phase.

[0252] 54. The solid oxide electrochemical cell of any one or more of the embodiments described herein, wherein the solid oxide electrolyte is selected from yttria stabilized zirconia (YSZ), scandia stabilized zirconia (SSZ), gadolinia doped ceria (GDC), samaria doped ceria (SDC), samaria-neodymium doped ceria (SNDC), erbia stabilized bismuth oxide (ESB), yttria stabilized bismuth oxide (YSB), strontium or magnesium doped lanthanum gallate (LSGM), and combinations thereof.

[0253] 55. The solid oxide electrochemical cell of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a solid oxide electrolysis cell (SOEC), a solid oxide fuel cell (SOFC), or a reversible solid oxide electrochemical cell.

[0254] 56. The solid oxide electrochemical cell of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a solid oxide electrolysis cell (SOEC) configured for synthesis of one or more of oxygen, hydrogen, carbon monoxide, or syngas.

[0255] 57. The solid oxide electrochemical cell of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a solid oxide fuel cell (SOFC) for converting chemical energy from one or more of hydrogen, ammonia, hydrocarbons, alcohols, syngas, solid carbon, and biomass SOFCs into electrical energy and / or thermal energy.

[0256] 58. The solid oxide electrochemical cell according to any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a symmetric solid oxide electrochemical cell having a positive electrode and a negative electrode, each electrode comprising an electrode composition or a sintered electrode material thereof.

[0257] 59. Use of the electrode composition, or a sintered electrode material thereof, according to any one or more embodiments described herein in preparing an electrode or electrode material for a solid oxide electrochemical cell.

[0258] 60. The use of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a solid oxide electrolysis cell (SOEC), a solid oxide fuel cell (SOFC), or a reversible solid oxide electrochemical cell.

[0259] 61. The use of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a solid oxide electrolysis cell (SOEC) configured for the synthesis of one or more of oxygen, hydrogen, carbon monoxide, or syngas.

[0260] 62. The use of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a solid oxide fuel cell (SOFC) selected from hydrogen, ammonia, hydrocarbon, alcohol, syngas, solid carbon, and biomass SOFCs.

[0261] 63. The use of any one or more of the embodiments described herein, wherein the solid oxide electrochemical cell is a symmetric solid oxide electrochemical cell having a positive electrode and a negative electrode, each electrode comprising the electrode composition or a sintered electrode material thereof.

[0262] 64. A method for producing a solid oxide electrochemical cell, comprising: a) preparing one or more solid oxide electrolyte layers; b) applying an electrode composition to one or both sides of a solid oxide electrolyte layer to form a component of a solid oxide electrochemical cell, wherein the electrode composition applied to at least one side of the solid oxide electrolyte layer comprises an electrode composition according to any one or more embodiments described herein; c) sintering the electrode composition applied onto a component of the solid oxide electrochemical cell to form an electrode or electrode material.

[0263] 65. The method of claim 64, wherein step b) comprises applying an electrode composition according to any one or more of the embodiments described herein to both sides of a solid oxide electrolyte layer.

[0264] 66. The method of any one or more embodiments described herein, wherein the solid oxide electrochemical cell is a symmetric cell comprising a positive electrode and a negative electrode on opposite sides of a solid oxide electrolyte layer, each electrode comprising or consisting of an electrode composition described in any one or more embodiments described herein. EXAMPLES

[0265] The present disclosure is further illustrated by the following examples. It should be understood that the following descriptions are merely for the purpose of illustrating certain embodiments, and are not intended to be limiting on the above description.

[0266] Example 1: Preparation of hybrid electrode particles Cerium nitrate hexahydrate and gadolinium nitrate hexahydrate were dissolved in deionized water to form an aqueous solution having a concentration of cerium nitrate and gadolinium nitrate, respectively, of 0.01-0.1M, e.g., 0.02M. A chelating agent (e.g., citric acid or EDTA) was then added to the aqueous solution in a molar ratio of citric acid to nitrate of about 1:1-1:5. The aqueous solution containing cerium nitrate, gadolinium nitrate, and the chelating agent (e.g., citric acid and EDTA) was then mixed with a plasticizer (e.g., triethylene glycol) in a ratio of about 2:1-4:1 (e.g., triethylene glycol-rich) based on the species present in the aqueous solution. The aqueous solution was then aged in a laboratory drying oven (with natural convection) to a temperature of 70-85°C for 24 hours.

[0267] Similarly, aqueous solutions of lanthanum nitrate hexahydrate (0.100 M), strontium nitrate (0.067 M), cobalt nitrate hexahydrate (0.035 M) and iron nitrate nonahydrate (0.140 M) were prepared and thoroughly mixed using a magnetic stirrer, followed by the addition of citric acid monohydrate (chelating agent) to the solution such that the molar ratio of nitrate:citric acid was 1:1. Next, triethylene glycol (plasticizer) was added to the solution such that the molar ratio of (nitrate + acid):triethylene glycol was 2:1. This liquid mixture was thoroughly stirred for 15 minutes to ensure dissolution of all chemicals, and then aged for 24 hours in a laboratory drying oven with natural convection at temperatures between 70 and 85 °C.

[0268] Similarly, in another example as bimetallic metal species and mixed oxide phases, an aqueous solution of silver nitrate (0.327 M) and iron nitrate nonahydrate (0.127 M) was thoroughly mixed and then added dropwise to an aqueous solution containing cerium nitrate, gadolinium nitrate, a chelating agent, and a plasticizer, all other steps remaining exactly the same.

[0269] In a separate beaker, an aqueous solution of silver nitrate was prepared at a concentration of about 0.01-0.1 M. The silver nitrate solution was added slowly (dropwise) to the above aqueous solution containing metal nitrates, chelating agents, and plasticizers and stirred on a hot plate at 70-85°C with constant stirring at 300-500 rpm with a laboratory stirrer (e.g., Fisher Scientific). The mixed aqueous solution (still liquid, viscous but flowable) was further aged in a drying oven for 24 hours at a temperature of 70-85°C, cooled to room temperature, and aged for an additional 4-8 hours to form a gel.

[0270] The gel mixture was then fired on a hot pyroglass surface maintained at 450° C. to burn off the organics and obtain a powder composition containing hybrid electrode particles with the desired microstructure (e.g., pyrolysis).

[0271] Example 2: Preparation of solid oxide electrolysis (SOEC) tube cell Solid Oxide Electrolyte Tube Ceramic 8 mol% yttria stabilized zirconia (YSZ) tubes were fabricated by cold isostatic pressing of 8YSZ powder at 170 MPa, followed by sintering at 1500° C. for 4 hours. The length and outer diameter of the tube were about 340 mm and about 11 mm, respectively. The thickness of the electrolyte tube was measured to be about 0.45 mm.

[0272] Fuel electrode (negative electrode) coating The ink for the fuel electrode was prepared by mixing the powder composition (i.e., the electrode composition described herein) with a terpineol-based ink vehicle (FCM materials, USA) in a ratio of 65:35 wt.%. The resulting slurry was ball-milled using zirconia balls for approximately 2 hours.

[0273] A dip-coating solution was also prepared using the powder composition of the hybrid electrode particles as follows. [Table 1]

[0274] The formulations were then applied to solid oxide electrolyte tubes via dip coating or brush coating and sintered at 600-850 °C using a heating and cooling rate of 120 °C / h for 4 h. The thickness of the sintered fuel electrodes containing sintered hybrid electrode particles (i.e., the sintered electrode material described herein) was 25 cm2 of active area. 2 It was measured to be about 40 μm thick at 350 nm.

[0275] For the tube cells using prior art electrodes, electrode ink was prepared with commercially available Ni-YSZ powder (FCM materials, USA) using a similar procedure as described above. Heat treatment of the prior art electrodes was carried out at 1400 °C for 2 h and then cooled to 25 °C according to standard state-of-the-art conditions. The heating and cooling rates were 3 °C / min. The electrodes were approximately 40 μm thick with an effective cell area of ​​25 cm. 2 It was.

[0276] Oxygen electrode (positive electrode) For both the prior art electrodes and the sintered hybrid electrodes, the sintered hybrid electrode was used as the air electrode. The electrode ink was prepared by mixing as a synthetic powder with a terpineol-based ink vehicle (Fuel Cell Materials Inc.) in a 65:35 weight ratio, followed by ball milling the mixture for 2 hours. The sintering profile included heating at 3°C / min to 825°C, followed by a dwell at 825°C for 2 hours, then cooling at 3°C / min to 25°C. Each electrode was approximately 40 μm thick with an active cell area of ​​25 cm. 2 It was.

[0277] Example 3: Testing of a Solid Oxide Electrolysis (SOEC) Tube Cell All cell tests and electrochemical measurements were performed using an in-house fabricated symmetric tube cell. The inlet gas supply (steam or steam / CO2 mixture or pure CO2) was delivered to the fuel chamber (within the tube, in contact with the fuel electrode (cathode)) at a constant flow rate of 30-50 ml / min. The oxygen electrode (anode) was exposed to the atmosphere with a room air flow of 50 ml / min. A schematic diagram of the setup is shown in Figure 11.

[0278] The mass flow meter was calibrated using a separate certified flow meter. The temperature at the center of the cathode was monitored using a single K-type thermocouple, hereafter designated as the operating temperature. VI curves (where reported) were obtained using a power supply (Keithley) and a digital multimeter (HP) to measure the voltage on the electrode. With the exception of steam electrolysis, only single point measurements at 1.2V or 1.5V were made (there are no VI curves due to experimental measurement limitations).

[0279] Example 4: Synthesis of Syngas An inlet gas supply of a mixture of steam and CO2 was provided to the fuel chamber as described in Example 3. The amount of syngas (i.e., a 1:1 volume % mixture of hydrogen and CO) produced using an SOEC tube cell including a fuel electrode made from a sintered hybrid electrode (i.e., a sintered electrode material) is significantly higher than prior art electrodes, as provided below. [Table 2]

[0280] Example 5: Steam electrolysis An inlet gas supply of steam was provided to the fuel chamber as described in Example 3. The amount of hydrogen produced using an SOEC tube cell including a fuel electrode made from a sintered hybrid electrode (i.e., a sintered electrode material) is significantly higher than prior art electrodes, as provided below. [Table 3]

[0281] Example 6: Synthesis of CO An inlet gas supply of dry CO2 was provided to the fuel chamber as described in Example 3. The amount of CO produced using an SOEC tube cell including a fuel electrode made from a sintered hybrid electrode (i.e., a sintered electrode material) is significantly higher than prior art electrodes, as provided below. [Table 4]

[0282] Example 7: Comparison with electrodes containing separate mixtures of Ag and GDC The performance of a symmetric solid oxide electrolysis cell (SOEC) prepared using an electrode prepared using sintered hybrid particles (i.e., sintered electrode material) was compared to an electrode prepared using separate silver and gadolinium doped ceria particles (mixed CGO-Ag). The symmetric SOEC was prepared using the protocol outlined in Example 2.

[0283] FIG. 6 shows the current-voltage (VI) curves of symmetric SOECs containing electrodes prepared using sintered materials including silver metal phase for steam electrolysis and one or more metal-doped ceria particles or separate moieties interspersed within the silver metal phase, Ni-YSZ composite, or mixed CGO-AG after loading at 1.5 V for 2 hours. The increase in current for SOECs containing electrodes fabricated using hybrid electrode particles can be attributed to the reduction in electrode polarization resistance. Without wishing to be bound by theory, it is believed that due to the unique microstructure of the hybrid electrode particles, electrons and transfer oxygen species (O) to and from the reactive sites located on the surface of each hybrid electrode particle are efficiently transported. 2- ) resulting in higher performance and enhanced performance (e.g., reduced electrode polarization resistance) compared to blends of separate silver and gadolinium doped ceria particles or conventional Ni-YSZ composites.

[0284] Similar improvements in performance have been seen with other electrode configurations, such as electrodes composed of hybrid electrode particles of Ag and one or more doped ferrite and bimetallic phases with one or more metal doped ceria, as shown in Figures 8 and 9. The electrode polarization resistance of these cells was <0.3 Ω cm compared to blends of separate metals and mixed ion conducting phases. 2 It was measured (Figure 10).

[0285] Example 8: Stability of electrode compositions in steam electrolysis The performance stability of a symmetric solid oxide electrolysis cell (SOEC) prepared using an electrode containing sintered hybrid particles was evaluated during steam electrolysis. Figure 7 shows that after 150 h of steam electrolysis, the SOEC showed a current density of 0.5–0.55 A / cm -2 , which highlights the improved performance stability of the hybrid electrode composition.

Claims

1. An electrode composition comprising a plurality of hybrid electrode particles, wherein each hybrid electrode particle comprises at least one metal phase and one oxide phase, the metal phase comprises a plurality of metal particles, the oxide phase comprises a plurality of ions or mixed ion-conducting oxide particles on the surface of the metal particles, the plurality of ions or mixed ion-conducting oxide particles are used to decorate the surface of the metal particles, and the particle size (in nm units) of the ions or mixed ion-conducting oxide particles on the surface of the metal particles is approximately 1 to 100.

2. The electrode composition according to claim 1, wherein the metal phase comprises at least one metal particle selected from silver (Ag), iron (Fe), nickel (Ni), and cobalt (Co).

3. The electrode composition according to claim 1, wherein the metal phase comprises a combination of silver (Ag) particles and one or more of iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), and titanium (Ti).

4. The electrode composition according to claim 1, wherein the metal phase contains silver (Ag) particles.

5. The electrode composition according to claim 1, wherein the oxide phase comprises ions or mixed ion-conducting oxide particles selected from metal-doped ceria, metal-doped ferrite, titanium-doped lanthanum strontium ferrite, and lanthanum strontium chromium manganese (LSCM).

6. The electrode composition according to claim 1, wherein the size of the metal particles is larger than the size of the ions or mixed ion-conducting oxide particles.

7. The electrode composition according to claim 1, wherein the hybrid electrode particles have a particle size (in μm units) of about 0.05 to 5.

8. The electrode composition according to claim 1, wherein the metal particles of each hybrid electrode particle have a particle size (in μm units) of about 0.1 to 5.

9. The electrode composition according to claim 1, wherein the composition is provided as a coating formulation containing the hybrid electrode particles as a powder present in one or more solvents.

10. The electrode composition according to claim 1, wherein the electrode composition is provided as a sintered electrode material comprising a metal phase as a porous scaffold and a plurality of separate oxide phases scattered within the metal phase.

11. The electrode composition according to claim 10, wherein the separate oxide phase is in the form of ions or mixed ion-conducting oxide particles.

12. The sintered electrode material is 1 cm ３ The electrode composition according to claim 10, comprising approximately 10 to 100 separate oxide phases per metal phase.

13. The electrode composition according to claim 10, wherein the sintered electrode material has a porosity of about 10 to 60 (in volume percent) based on the total volume of the sintered electrode material, and the thickness of the sintered electrode material (in μm) is 1 to 100.

14. A modified sol-gel process for preparing hybrid electrode particles, wherein each hybrid electrode particle comprises at least one metal phase and one oxide phase, the metal phase comprising a plurality of metal particles, the oxide phase comprising a plurality of ions or mixed ion-conducting oxide particles on the surface of the metal particles, the plurality of ions or mixed ion-conducting oxide particles decorating the surface of the metal particles, the particle size (in nm) of the ions or mixed ion-conducting oxide particles on the surface of the metal particles being about 1 to 100, and the process is, a) Preparing a gel from an aqueous solution containing a metal species, an ion or mixed ion-conducting oxide species, a plasticizer, and a chelating agent, b) A modified sol-gel process comprising heating the gel to obtain a powder composition containing the hybrid electrode particles.

15. The modified sol-gel process according to claim 14, wherein step a) comprises preparing an aqueous solution containing the ions or mixed ion-conducting oxide species, then adding the chelating agent and plasticizer to the aqueous solution, and then adding a metal species.

16. The modified sol-gel process according to claim 15, wherein the aqueous solution containing the ions or mixed ion-conducting oxide species, a chelating agent, and a plasticizer is aged before the addition of the metal species.

17. The modified sol-gel process according to claim 14, wherein, after step a) but before step b), the process comprises aging the gel in any residual aqueous solution at a temperature of about 60°C to 90°C for a period of about 12 to 36 hours, before heating in step b).

18. The modified sol-gel process according to claim 14, wherein the metal species comprises at least one metal particle selected from silver (Ag), iron (Fe), nickel (Ni), and cobalt (Co).

19. The modified sol-gel process according to claim 14, wherein the metallic phase comprises a combination of silver (Ag) particles and one or more of iron (Fe), nickel (Ni), cobalt (Co), copper (Cu), and titanium (Ti).

20. The modified sol-gel process according to claim 14, wherein the oxide phase comprises ions or mixed ion-conducting oxide particles selected from metal-doped ceria, metal-doped ferrite, titanium-doped lanthanum strontium ferrite, and lanthanum strontium chromium manganese (LSCM).

21. The modified sol-gel process according to claim 14, wherein the molar ratio of the metal species to the ions or mixed ion-conducting oxide species is about 1:5 to 5:

1.

22. The modified sol-gel process according to claim 14, wherein the gel is heated to a temperature of about 300°C to 600°C in step b).

23. The modified sol-gel process according to claim 14, wherein step b) comprises performing flame spray thermal decomposition or spray drying of the gel obtained from step a) to obtain the powder composition of hybrid electrode particles.

24. The modified sol-gel process according to claim 14, wherein the powder composition containing the hybrid electrode particles is further processed into a dry powder formulation or a wet coating formulation containing one or more solvents.

25. The modified sol-gel process according to claim 14, wherein the powder composition or a compound thereof is sintered into a sintered electrode material comprising a metal phase as a porous scaffold and a plurality of separate ions or mixed ion-conducting oxide phases scattered within the metal phase.

26. The modified sol-gel process according to claim 25, wherein the sintering is performed at a temperature of approximately 500°C to 900°C.

27. The modified sol-gel process according to claim 14, wherein a solid oxide electrochemical cell is prepared, comprising an electrode containing the powder composition or a sintered electrode material thereof, and the solid oxide electrochemical cell comprises a positive electrode and a negative electrode, each containing the powder composition or the sintered electrode material thereof.

28. A solid oxide electrochemical cell comprising a cathode, a solid oxide electrolyte, and an anode, wherein the cathode and / or the anode comprises the electrode composition described in claim 1, or a sintered electrode material thereof.

29. The solid oxide electrochemical cell according to claim 28, wherein the sintered electrode material of the electrode composition comprises a metal phase as a porous scaffold and a plurality of separate ions or mixed ion conductive oxide phases scattered within the silver metal phase.

30. The solid oxide electrochemical cell according to claim 29, wherein the electrode composition or the sintered electrode material thereof is coated onto an electrode support.

31. The solid oxide electrochemical cell according to claim 29, wherein the sintered electrode material has a porosity of about 10 to 60 (in volume percent) based on the total volume of the sintered electrode material.

32. The sintered electrode material is 1 cm ３ The solid oxide electrochemical cell according to claim 29, comprising approximately 50 to 500 distinct or mixed ion-conducting oxide phases per metal phase.

33. The solid oxide electrochemical cell is a solid oxide electrolytic cell (SOEC), a solid oxide fuel cell (SOFC), or a reversible solid oxide electrochemical cell, wherein the solid oxide electrochemical cell is a solid oxide electrolytic cell (SOEC) configured for the synthesis of one or more of oxygen, hydrogen, carbon monoxide, or synthesis gas, and the solid oxide electrochemical cell is a solid oxide fuel cell (SOFC) for converting chemical energy from one or more of hydrogen, ammonia, hydrocarbons, alcohols, synthesis gas, solid carbon, and biomass SOFCs into electrical energy and / or thermal energy. The solid oxide electrochemical cell according to claim 28.

34. The solid oxide electrochemical cell according to claim 28, wherein the solid oxide electrochemical cell is a symmetric solid oxide electrochemical cell having a positive electrode and a negative electrode, and each electrode comprises the electrode composition or a sintered electrode material thereof.

35. The use of the electrode composition according to claim 1, or the sintered electrode material thereof, when preparing an electrode or electrode material for a solid oxide electrochemical cell.

36. A method for producing a solid oxide electrochemical cell, a) Prepare one or more solid oxide electrolyte layers, b) Forming a component of a solid oxide electrochemical cell by applying an electrode composition to one or both sides of the solid oxide electrolyte layer, wherein the electrode composition applied to at least one side of the solid oxide electrolyte layer includes the electrode composition described in claim 1. c) A method comprising sintering the electrode composition applied to the components of the solid oxide electrochemical cell to form an electrode or electrode material.

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