Copolymer-based encapsulation for durable catalyst particles

Abstract

The invention relates to a copolymer-based encapsulation for durable catalyst particles. An electrochemical cell includes first and second electrodes. The first electrode includes first catalyst particles that enhance activity in the electrochemical cell. The second electrode includes second catalyst particles that enhance activity in the electrochemical cell. One or both of the first and second catalyst particles are at least partially encapsulated in a silica encapsulation formed from a precursor of a silicon-based copolymer. The silica encapsulation maintains the activity of the first and / or second catalyst particles.

Description

Technical Field

[0001] The present disclosure relates to copolymer-based encapsulation of durable catalyst particles for electrochemical cells. The copolymer material used in the copolymer can be a silicon-based copolymer material. The catalyst particles can be catalyst nanoparticles. Background Art

[0002] With the growing global interest in green technologies, electrochemical cells such as fuel cells and electrolyzers have become interesting candidates for various applications. An electrochemical cell is a device that can generate electrical energy from a chemical reaction (e.g., a fuel cell) or use electrical energy to perform an electrochemical reaction (e.g., an electrolyzer).

[0003] Fuel cells have shown promise as an alternative power source for vehicles and other transportation applications. Fuel cells operate using renewable energy carriers such as hydrogen. Hydrogen fuel cells also do not produce toxic emissions or greenhouse gases when operated. A single fuel cell includes a membrane electrode assembly (MEA) and two flow field plates. A single fuel cell typically provides a voltage of 0.5V to 1.0V. Single fuel cells can be stacked together to form a fuel cell stack with higher voltage and power. One type of fuel cell is a proton exchange membrane fuel cell (PEMFC).

[0004] Electrolyzers decompose water into hydrogen and oxygen through an electrolysis process, providing a promising method for producing hydrogen from renewable resources. Similar to fuel cells, electrolyzers include anode and cathode catalyst layers separated by an electrolyte membrane. The electrolyte membrane can be an ion-conducting polymer, an alkaline solution, or a solid ceramic material. Catalyst materials are included in the anode catalyst layer and the cathode catalyst layer of the electrolyzer. One type of electrolyzer is a proton exchange membrane electrolyzer (PEMEC).

[0005] One of the main technical challenges to achieving long durability and low cost of electrochemical cells is catalyst degradation. Dissolution of catalyst materials can lead to a loss of electrochemically active surface area (ECSA). In PEMFCs, this loss of ECSA leads to a subsequent decrease in oxygen reduction reaction (ORR) activity. Migrating ions can activate other degradation modes in the ionomer and membrane of the electrochemical cell. Summary of the invention

[0006] In one embodiment, an electrochemical cell is disclosed. The electrochemical cell includes first and second electrodes. The first electrode includes first catalyst particles that enhance activity in the electrochemical cell. The second electrode includes second catalyst particles that enhance activity in the electrochemical cell. One or both of the first and second catalyst particles are at least partially encapsulated in a silica encapsulation formed from a precursor of a silicon-based copolymer. The silica encapsulation maintains the activity of the first and / or second catalyst particles.

[0007] In another embodiment, a packaged catalyst particle system for an electrochemical cell is disclosed. The packaged catalyst particle system includes catalyst particles configured to enhance activity in an electrochemical cell. The packaged catalyst particle system further includes an encapsulation precursor of a silicon-based copolymer that at least partially encapsulates the catalyst particles. The encapsulation precursor is configured to maintain the activity of the catalyst particles.

[0008] In another embodiment, a method of forming encapsulated catalyst particles for an electrochemical cell is disclosed. The method includes applying an encapsulation precursor of a silicon-based copolymer to the catalyst particles. The catalyst particles are configured to enhance activity in the electrochemical cell. The method further includes subjecting the encapsulation precursor to oxygen treatment to obtain encapsulated catalyst particles including silicon dioxide encapsulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A Depicted is a schematic side view of a fuel cell according to one embodiment.

[0010] Figure 1B Depicted is a schematic side view of an electrolytic cell according to one embodiment.

[0011] Figure 2 Schematic diagram of the steps for forming an encapsulated catalyst nanoparticle system from catalyst nanoparticles and a silicon-based copolymer.

[0012] Figure 3A is a schematic diagram of an encapsulated catalyst nanoparticle system having a relatively high carbon thickness on the surface of the platinum catalyst nanoparticles after a relatively short oxygen treatment according to one embodiment.

[0013] Figure 3B is a schematic diagram of an encapsulated catalyst nanoparticle system having a relatively low carbon thickness on the surface of the platinum catalyst nanoparticles after a relatively long oxygen treatment according to one embodiment. DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. These drawings are not necessarily to scale; certain features may be magnified or minimized to show the details of a particular component. Therefore, the specific structural and functional details disclosed herein should not be interpreted as restrictive, but merely as a representative basis for teaching those skilled in the art to use the embodiments in different ways. As will be understood by those of ordinary skill in the art, the various features illustrated and described with reference to any of the figures may be combined with the features illustrated in one or more other figures to produce an embodiment that is not explicitly illustrated or described. The combination of features shown provides representative embodiments for typical applications. However, various combinations and modifications of features consistent with the teachings of the present disclosure may be required for specific applications or implementations.

[0015] Except in the examples or otherwise explicitly stated, all numerical values ​​in this specification indicating the amount of material or reaction and / or use conditions should be understood as being modified by the word "about" when describing the broadest scope of the invention. It is usually preferred to practice within the specified numerical limits. In addition, unless explicitly stated to the contrary: percentages, "parts" and ratio values ​​are all by weight; describing a group or class of materials as suitable or preferred for a given purpose related to the present invention means that mixtures of any two or more members of the group or class are also suitable or preferred; descriptions of ingredients in chemical terms refer to ingredients when added to any combination specified in the description, and do not necessarily exclude chemical interactions between ingredients of the mixture after mixing.

[0016] The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation; and, unless expressly stated to the contrary, measurements of properties are determined by the same techniques as previously or later cited for the same property.

[0017] It must also be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a singular component is intended to include plural components.

[0018] As used herein, the terms "substantially", "roughly" or "approximately" mean that the amount or value in question can be a specified specific value or some other value in the vicinity thereof. Typically, the term "approximately" representing a specific value is intended to represent a range within ±5% of that value. As an example, the phrase "about 100" represents a range of 100 ± 5, i.e., a range from 95 to 105. Typically, when the term "approximately" is used, it can be expected that similar results or effects according to the present invention can be obtained within a range of ±5% of the value shown. The term "substantially" can modify the value or related features disclosed or claimed in the present disclosure. In this case, "substantially" can represent that the value or related characteristics it modifies are within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative feature.

[0019] It should also be understood that integer ranges explicitly include all intermediate integers. For example, the integer range 1-10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Similarly, the range 1 to 100 includes 1, 2, 3, 4 ... 97, 98, 99, 100. Similarly, when any range is required, the intermediate number that is the difference between the upper and lower limits divided by the increment of 10 can be taken as an alternative upper or lower limit. For example, if the range is 1.1 to 2.1, the following numbers 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 and 2.0 can be selected as the lower or upper limit.

[0020] In the examples described herein, the concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rate, etc.) may be implemented with the values ​​provided in the examples rounded or truncated to plus or minus 50% of the values ​​indicated by two significant figures. In a refinement, the concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rate, etc.) may be implemented with the values ​​provided in the examples rounded or truncated to plus or minus 30% of the values ​​indicated by two significant figures. In another refinement, the concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow rate, etc.) may be implemented with the values ​​provided in the examples rounded or truncated to plus or minus 10% of the values ​​indicated by two significant figures.

[0021] As used herein, the term "and / or" means that all or only one element of the group may be present. For example, "A and / or B" means "only A, or only B, or both A and B". In the case of "only A", the term also covers the possibility that B is not present, that is, "only A, but not B".

[0022] It should also be understood that the present invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may of course vary. Furthermore, the terminology used herein is only for the purpose of describing specific embodiments of the present invention and is not intended to be limiting in any way.

[0023] The term "comprising" is synonymous with "including," "having," "containing," or "characterized by." These terms are inclusive and open-ended and do not exclude additional, unrecited elements or method steps.

[0024] The phrase "consisting of" excludes any element, step, or ingredient not specified in a claim. When the phrase appears in the body of a claim rather than immediately following the preamble, it limits only the elements set forth in that clause; other elements are not excluded from the claim as a whole.

[0025] The phrase "consisting essentially of" limits the scope of a claim to the specified materials or steps, plus those materials or steps that do not materially affect the basic and novel characteristic(s) of the claimed subject matter.

[0026] With respect to the terms "comprising," "consisting of," and "consisting essentially of," where one of these three terms is used herein, the presently disclosed and claimed subject matter may include the use of either of the other two terms.

[0027] The term "one or more" means "at least one," and the term "at least one" means "one or more." The terms "one or more" and "at least one" include "plurality" as a subset.

[0028] Description of a group or class of materials as suitable for a given purpose in connection with one or more embodiments means that mixtures of any two or more members of the group or class are suitable. Descriptions of ingredients in chemical terms refer to the ingredients when added to any combination specified in the specification, and do not necessarily exclude chemical interactions between the ingredients of the mixture once mixed. The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein, and mutatis mutandis applies to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurements of properties are determined by the same techniques as previously or later cited for the same property.

[0029] Electrochemical cells provide an attractive solution for clean energy generation. A non-limiting example of an electrochemical cell is a proton exchange membrane fuel cell (PEMFC). PEMFCs running on hydrogen have many potential benefits (e.g., high efficiency, fast start-up, and high power density). Significant progress has been made in improving PEMFC technology by optimizing internal cell design, reducing catalyst loading, and increasing power density. Nevertheless, the durability of PEMFC components (e.g., catalysts) remains a challenge that needs to be overcome to achieve large-scale deployment of PEMFC technology.

[0030] While platinum nanoparticles and their alloys can be used to catalyze the slow oxygen reduction reaction (ORR) at the PEMFC cathode, the highly acidic environment accelerates the dissolution of the platinum nanoparticles during potential cycling and startup and shutdown scenarios. The dissolution of the platinum nanoparticles results in a loss of electrochemically active surface area (ECSA), which leads to reduced ORR activity. In addition, the generated platinum ions can be dispersed in the ionomer and membrane and redeposited at the interface between the electrode and the membrane or within the membrane, which can increase the potential for hydrogen peroxide generation and can accelerate the degradation of polymer species in PEMFCs. These scenarios become even more important given the need to reduce platinum cathode loading due to cost considerations.

[0031] A proposal to improve catalyst stability in PEMFCs includes encapsulating the catalyst material with an encapsulation. The encapsulation may be a covering layer deposited on the surface of catalyst particles (e.g., nanoparticles) formed of the catalyst material. The covering layer may have an ultra-thin thickness and / or may be formed of a semi-permeable material. The covering layer may be configured to resist the loss of catalyst material while allowing reactive species to reach the catalyst surface.

[0032] Silicon dioxide (SiO x ) is a candidate material for encapsulation. One consideration for the performance of silica encapsulation materials is the composition. Changing the siloxane precursor composition or the composite structure of the silica encapsulation will change its physical and chemical properties, which can subsequently affect the performance of the silica encapsulated platinum electrode.

[0033] A proposal uses carbon-modified silica on flat platinum (Pt) plates to study the effect of encapsulation composition on gas species transport and platinum (Pt) electrochemical performance. The proposal found that proton and O2 permeability showed opposite trends with catalyst encapsulation. H + These longer curing times promote the inclusion of continuous SiO x The formation of a dense, uniform catalyst packing network is well suited to promote H + In contrast, using this scheme, the oxygen permeability is greatest for catalyst packages exposed to shorter curing times, characterized by lower density that can facilitate O2 diffusion through larger free volume areas.

[0034] In view of the above, there is a need for a catalyst package that can precisely control the composition and / or thickness of the package material. There is a further need for a package material that is suitable for different types of electrochemical cells (e.g., electrochemical cells and electrolyzers). One or more embodiments provide such a packaged catalyst particle system.

[0035] Figure 1AA schematic side view of a fuel cell 10 according to one embodiment is depicted. The catalyst package of one or more embodiments may be applied to the fuel cell 10. The fuel cell 10 may be stacked to form a fuel cell stack. The fuel cell 10 includes a polymer electrolyte membrane (PEM) 12, an anode 14, a cathode 16, and first and second gas diffusion layers (GDLs) 18 and 20. The PEM 12 is located between the anode 14 and the cathode 16. The anode 14 is located between the first GDL 18 and the PEM 12, and the cathode 16 is located between the second GDL 20 and the PEM 12. The PEM 12, the anode 14, the cathode 16, and the first and second GDLs 18 and 20 constitute a membrane electrode assembly (MEA) 22. The first side 24 and the second side 26 of the MEA 22 are defined by flow fields 28 and 30, respectively. The flow field 28 supplies H2 to the MEA 22, as shown by arrow 32. The flow field 30 supplies O2 to the MEA 22, as shown by arrow 34. One or more catalyst materials are used in the anode 14 and the cathode 16. Non-limiting examples of catalyst materials include platinum, palladium, ruthenium, alloys thereof, and combinations thereof.

[0036] Figure 1B A schematic side view of an electrolyzer 60 according to one embodiment is depicted. The electrolyzer undergoes an electrolysis process to decompose water into hydrogen and oxygen. The electrolyzer 60 includes an anode catalyst layer 62 and a cathode catalyst layer 64 separated by an electrolyte membrane 66. Catalyst materials are included in the anode catalyst layer 62 and the cathode catalyst layer 64. The electrolyte membrane 66 can be a polymer, an alkaline solution, or a solid ceramic material. A porous transport layer 68 contacts the surface of the anode catalyst layer 62 opposite the electrolyte membrane. A gas diffusion medium 70 contacts the surface of the cathode catalyst layer 64 opposite the electrolyte membrane 66. An oxygen evolution reaction (OER) occurs at the anode catalyst layer 62, and a hydrogen evolution reaction (HER) occurs at the cathode catalyst layer 64, where H + Ions flow from the anode catalyst layer 62 to the cathode catalyst layer 64 through the electrolyte membrane 66 .

[0037] Although Figure 1A and 1B PEMFCs and electrolyzers are described separately, but one or more embodiments of catalyst packaging may be applied to any type of electrochemical cell or system (eg, an alkaline anion exchange membrane fuel cell or a carbon dioxide electrochemical conversion device).

[0038] In one or more embodiments, a catalyst package for an electrochemical system (e.g., a fuel cell and an electrolyzer) is disclosed. The package can be based on a silicon-carbon copolymer. The sequence, chain length, and / or ratio of silicon monomers and carbon monomers in the silicon-carbon copolymer can be customized to achieve packaging for different applications. The application process and packaging materials can be applied to any metal nanoparticles suitable as catalyst materials in electrodes of electrochemical cells (e.g., fuel cells or electrolyzers).

[0039] Catalyst encapsulation may have one or more benefits. Catalyst encapsulation may achieve high reactivity, long durability and stability by resisting dissolution, minimizing catalyst poisoning with ionomers or carbon monoxide and / or by blocking undesirable reactions. In one or more embodiments, a silicon-based copolymer may be used as a precursor to apply a carbon-doped silicon dioxide film to the surface of the catalyst particles. According to one method, various silicon-carbon-based copolymers are suitable for being dissolved in an organic solvent and mixed with supported catalyst nanoparticles, and then treated with oxygen (e.g., by ultraviolet (UV) treatment or plasma treatment) to produce a permanent silicon dioxide encapsulation with engineered chemical properties. This control of composition and treatment time may be utilized to achieve enhanced permeability of reactants to the catalyst surface.

[0040] The monomer units of the silicon-based copolymer can be arranged in different patterns (e.g., linear, branched, comb-like and / or brush-like patterns). The copolymer structure can be a block copolymer, a random copolymer or an alternating copolymer. In a block copolymer, different blocks of monomers can have different chemical and / or physical properties, which determine the properties of the silicon-based copolymer material. The silicon-based copolymer material can be applied to a catalyst material (e.g., catalyst particles) to form a coating that at least partially or completely surrounds the catalyst material. The catalyst particles can be catalyst nanoparticles. After the silicon-based copolymer material is applied to the catalyst material, the silicon-based copolymer material can be cured (e.g., treated with oxygen) to produce a permeable and durable silicon dioxide (e.g., carbon-doped silicon dioxide) coating, which is configured to enhance catalyst durability and resist catalyst dissolution.

[0041] Silicon-based copolymer materials can be composed of one or more chains containing two or more chemical substances in different arrangements. Silicon-based copolymer materials can be linear diblock copolymers, including a first block, which is composed of a first monomer of a first quantity bonded in a first polymer chain, and a second block, which is composed of a second monomer of a second quantity bonded in a second polymer chain, wherein the first and second blocks are bonded to each other to form a linear diblock copolymer. The first and second monomers may have chemical differences to produce local ordering and / or segregation of linear block copolymers. Certain chemical substances in silicon-based copolymer materials may migrate to a free surface or interface due to thermodynamic forces. These chemical substances are selected as coatings and used for functionalization. In one or more embodiments, a silicon-based copolymer material is selected as a catalyst encapsulation to encapsulate catalyst nanoparticles. Silicon-based copolymer materials may include silicon-based and carbon-based monomers to promote microphase separation, because there is a relatively large degree of incompatibility between silicon-based and carbon-based monomers.

[0042] The copolymer material based on silicon can be a low molecular weight copolymer. The molecular weight copolymer can be in the range of any of the following values ​​or any two of the following values: 5,000, 6,000, 7,000, 8,000, 9,000, 10,000, 11,000, 12,000, 13,000, 14,000, 15,000, 16,000, 17,000, 18,000, 19,000 and 20,000 daltons. The low molecular weight copolymer can be applied to the catalyst nanoparticles using spin coating techniques. For example, the copolymer material based on silicon can be dissolved in an organic solvent (e.g., toluene, heptane, or a combination thereof). After the copolymer based on silicon is dissolved in an organic solvent, the catalyst nanoparticles are added to the organic solvent and mixed. In one or more embodiments, the mixture is dispersed. Spin coating or ultrasonic treatment can be used to achieve dispersion.

[0043] One or more annealing methods can be used to adjust the structure of the catalyst particles (e.g., catalyst nanoparticles) and the encapsulation system. For example, the polymer chains in the silicon-based copolymer can be reoriented and arranged to a relaxed state around the catalyst nanoparticles. This type of annealing method can be performed using solvent vapor annealing or thermal annealing. During the annealing step, since the silicon-based monomers in the silicon-based copolymer have relatively low surface energy, they tend to migrate to the surface area. The annealing time can be adjusted to limit the degree of phase separation between the first chemical substance (e.g., one or more silicon-based monomers) and the second chemical substance (e.g., one or more carbon-based monomers).

[0044] According to one or more embodiments, the catalyst particles (e.g., catalyst nanoparticles) and the adjusted structure of the encapsulation system are cured. Non-limiting examples of the curing step include UV exposure or oxygen plasma exposure. The curing step can be used to remove carbon-based substances from the system (e.g., by ashing) while converting silicon-based monomers into durable silicon dioxide. Carbon doping can be achieved by adjusting the exposure level, controlling the silicon dioxide structure and / or density.

[0045] Figure 2 is a schematic diagram of steps 100 of forming an encapsulated catalyst nanoparticle system 102 from catalyst nanoparticles 104 and a silicon-based copolymer 106. Figure 2 As shown, the silicon-based copolymer 106 includes silicon-based monomer units 108 (ie, Figure 2 Sil) and carbon-based monomer units 110 (ie, as depicted Figure 2 depicted in CH).

[0046] The number n of bonded silicon-based monomer units 108 and carbon-based monomer units 110 may be independently selected from any of the following values ​​or a range of any two of the following values: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, and 200. The arrangement of the silicon-based monomer units 108 and the carbon-based monomer units 110 within the brackets may be repeated m times. The number m can be any of the following values ​​or a range of any two of the following values: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195 and 200.

[0047] The silicon-based monomer unit 108 may include monomer units including one or more siloxane groups, one or more carbosiloxane groups, one or more silane groups, one or more carbosilane groups, and combinations thereof. The following formulas (1), (2), and (3) describe examples of polysiloxane, polycarbosiloxane, and polycarbosilane groups, respectively. The value of n may be any of the following values ​​or within the range of any two of the following values: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195, and 200.

[0048]

[0049]

[0050] The carbon-based monomer units 110 may include monomer units including one or more styrene groups, one or more vinyl groups, one or more propylene groups, or combinations thereof. Other carbon-based groups may include hydrocarbon functional groups such as alkanes, alkenes, alkynes, and aromatics.

[0051] In one or more embodiments, the metal nanoparticles formed from the catalyst material are coated with a silicon-based copolymer comprising one or more silicon-based monomer units and one or more carbon-based units. The catalyst material can be pure Pt, a Pt-M alloy (wherein M is another metal from the periodic table), other platinum group member (PGM) metals (e.g., Ru, Rh, Pd, Os, and / or Ir), a PGM-M alloy (wherein M is another metal from the periodic table), a Pt-PGM-M alloy (wherein M is another metal from the periodic table), or a combination thereof.

[0052] After the coating step, the coated nanoparticles are subjected to oxygen treatment to form encapsulated catalyst nanoparticles. The oxygen treatment can be applied by ultraviolet light and / or plasma treatment. The treatment step can form a thin film around the catalyst nanoparticles. The thickness of the film can be within the range of any of the following values ​​or two of the following values: 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 nanometers.

[0053] The final structure and composition (e.g., density) of the encapsulation coating can be controlled by the duration of the oxygen treatment. Relatively long treatment times (e.g., curing times) can ashed the carbon content in the encapsulation coating or film and produce a dense silica film that is configured to promote proton diffusion but prevent O2 transmission. Relatively short treatment times (e.g., curing times) can maintain a higher carbon concentration in an encapsulation coating or film with a loosely connected silica network. In one or more embodiments, the loosely connected silica network is permeable to O2, but provides undesirable proton desired properties. Polymer chemistry, molecular weight, annealing time, and / or post-processing time are degrees of freedom for adjusting the performance characteristics of the encapsulation coating or film. For encapsulation coatings formed from silicon-based copolymer materials, the method can be applied to catalyst nanoparticles connected to a conductive carrier to maintain electrochemical activity.

[0054] Figure 3A is a schematic diagram of an encapsulated catalyst nanoparticle system 130 having a relatively high carbon thickness 150 on a surface 152 of a platinum catalyst nanoparticle 154 after a relatively short oxygen treatment according to one embodiment. The relatively short exposure duration can result in a less dense film having a relatively high amount of carbon. Figure 3B is a schematic diagram of an encapsulated catalyst nanoparticle system 140 having a relatively low carbon thickness 160 on a surface 162 of a platinum catalyst nanoparticle 154 after a relatively long oxygen treatment according to one embodiment. A relatively long exposure duration can result in a denser film having a relatively low amount of carbon.

[0055] like Figure 3A and 3B As shown, silica is formed as outer surface portions 156 and 166 of the encapsulated catalyst nanoparticle systems 130 and 140, respectively. The density of the silica of the outer surface portion 156 or the outer surface 166 can be any value or any two values ​​below, with a standard density of 2.65 g / cm 3 The percentage of silica is represented by: 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% and 80%. The outer surface portion of the silica is configured to be adsorbed with an adsorbent such as carbon monoxide (CO) and / or sulfonyl (SO3 - ) Resists catalyst poisoning. Silica encapsulation resists undesirable reactions at the catalyst surface by acting as a physical barrier.

[0056] Silica encapsulation may have one or more of the following benefits: (a) chemical stability in acidic environments, (b) inactivity as an electrocatalyst due to inherent electronic insulation, and / or (c) good permeability to many species relevant to electrochemical cell applications. The success of using silica may depend on the encapsulation thickness. In one or more embodiments, the thickness is thick enough to impart desirable selective transport properties, but not so thick as to produce large concentration overpotential losses.

[0057] Although exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms included in the claims. The words used in the specification are descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of various embodiments can be combined to form other embodiments of the present invention that may not be explicitly described or shown. Although various embodiments may have been described as providing advantages or being superior to other embodiments or prior art embodiments relative to one or more desired characteristics, it is recognized by those of ordinary skill in the art that one or more features or characteristics can be compromised to achieve the desired overall system properties, depending on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, applicability, weight, manufacturability, ease of assembly, etc. Therefore, to the extent that any embodiment is less desirable relative to other embodiments or prior art embodiments in terms of one or more characteristics, these embodiments do not exceed the scope of the present disclosure and may be desirable for a particular application.

Claims

1. An electrochemical cell comprising: First and second electrodes, the first electrode comprising first catalyst particles that enhance activity in the electrochemical cell, the second electrode comprising second catalyst particles that enhance activity in the electrochemical cell, one or both of the first and second catalyst particles being at least partially encapsulated in a silica encapsulation formed from a precursor of a silicon-based copolymer, the silica encapsulation maintaining the activity of the first and / or second catalyst particles.

2. The electrochemical cell of claim 1, wherein the silicon-based copolymer is a silicon-carbon copolymer.

3. The electrochemical cell of claim 2, wherein the silicon-based copolymer has a low molecular weight of 5,000 to 20,000 Daltons.

4. The electrochemical cell of claim 2, wherein the silicon-based copolymer comprises a silicon-based monomer and a carbon-based monomer.

5. The electrochemical cell of claim 4, wherein the silicon-based monomer comprises a monomer unit comprising one or more siloxane groups, one or more carbosiloxane groups, one or more silane groups, one or more carbosilane groups, or a combination thereof.

6. The electrochemical cell of claim 4, wherein the carbon-based monomer comprises a monomer unit comprising one or more styrene groups, one or more vinyl groups, one or more propylene groups, or a combination thereof.

7. An electrochemical cell according to claim 1, wherein the first and second catalyst particles are formed of first and second catalyst materials, and the first and second catalyst materials are independently selected from pure Pt, Pt-M alloys (wherein M is another metal from the periodic table), other platinum group member (PGM) metals (e.g., Ru, Rh, Pd, Os and / or Ir), PGM-M alloys (wherein M is another metal from the periodic table), Pt-PGM-M alloys (wherein M is another metal from the periodic table), or combinations thereof.

8. The electrochemical cell of claim 1, wherein the silica encapsulation comprises a silica network of SiO2.

9. The electrochemical cell of claim 1, wherein the silicon dioxide package comprises a carbon film having silicon dioxide formed on an outer surface portion of the silicon dioxide package.

10. The electrochemical cell of claim 9, wherein the silicon dioxide has a carbon content of 0.265 g / cm 3 Up to 2.12g / cm 3 density.

11. The electrochemical cell of claim 1 , wherein one or both of the first and second catalyst particles are completely encapsulated in the silica encapsulation.

12. The electrochemical cell of claim 1, wherein the first and second catalyst particles are first and second catalyst nanoparticles.

13. A system of encapsulated catalyst particles for an electrochemical cell, comprising: catalyst particles configured to enhance activity in said electrochemical cell; and An encapsulation precursor of a silicon-based copolymer at least partially encapsulates the catalyst particles, the encapsulation precursor being configured to maintain activity of the catalyst particles.

14. The encapsulated catalyst particle system of claim 13, wherein the silicon-based copolymer is a silicon-carbon copolymer.

15. The encapsulated catalyst particle system of claim 14, wherein the silicon-based copolymer comprises a silicon-based monomer and a carbon-based monomer.

16. The encapsulated catalyst particle system of claim 14, wherein the catalyst particles are formed of a catalyst material selected from pure Pt, a Pt-M alloy (wherein M is another metal from the periodic table), other platinum group member (PGM) metals (e.g., Ru, Rh, Pd, Os and / or Ir), a PGM-M alloy (wherein M is another metal from the periodic table), a Pt-PGM-M alloy (wherein M is another metal from the periodic table), or a combination thereof.

17. A method of forming encapsulated catalyst particles for an electrochemical cell, the method comprising: applying an encapsulation precursor of a silicon-based copolymer to catalyst particles, the catalyst particles being configured to enhance activity in the electrochemical cell; and The encapsulated precursor is subjected to oxygen treatment to obtain encapsulated catalyst particles including a silica encapsulation.

18. The method of claim 17, wherein the applying step comprises dissolving the silicon-based copolymer in an organic solvent and adding the catalyst particles to the organic solvent.

19. The method of claim 17, further comprising annealing the encapsulation precursor prior to the subjecting step.

20. The method of claim 17, wherein the subjecting step is performed under ultraviolet (UV) exposure or oxygen plasma exposure.

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