Electrochemical cell catalyst layer

Abstract

An electrochemical cell comprising an anode, a cathode, and a membrane physically separating the anode from the cathode, the cathode having a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate forming an ionomer-support interface having a covalent bond formed between the substrate and the ionomer by a graft compound, the substrate also has a plurality of terminated hydrophilic groups.

Description

Technical Field

[0001] The present disclosure relates to materials and structures for catalyst layers in chemical and electrochemical cells and methods of use and manufacture thereof.

[0002] background

[0003] With the growing interest in green technologies around the world, electrochemical cells such as fuel cells and electrolyzers have become the first choice for a variety of applications. However, there are many challenges that need to be addressed before electrochemical cells can be widely used. Among these challenges are material corrosion and degradation, catalyst cost and dissolution, and factors that affect the effectiveness and efficiency of the cell, such as oxygen transport within the cell layers.

[0004] Overview

[0005] In one or more embodiments, an electrochemical cell is disclosed. The cell may include an anode, a cathode, and a membrane physically separating the anode from the cathode. The cathode may have a cathode catalyst layer, the cathode catalyst layer including an ionomer and an electrocatalyst support substrate forming an ionomer-support interface, the interface having covalent bonds formed between the substrate and the ionomer by a grafted compound. The substrate may also have a plurality of capped hydrophilic groups. The grafted compound may be an aromatic compound. The covalent bond may be between a hydrophilic group of the substrate and an aromatic group of the aromatic compound. The covalent bond may be a substrate-acetyl bond. The interface may also include a covalent bond between a reactive group of the grafted compound and an ionomer carbon atom adjacent to the hydrophilic group of the ionomer. The grafted compound may be an iodonium compound. The covalent bond may include an oxygen atom of an epoxy group. The substrate may include a carbon-based material. The grafted compound may include a benzyl iodonium group.

[0006] In another embodiment, a cathode catalyst layer ionomer-support interface is disclosed. The interface may include an ionomer having hydrophilic side chains and a hydrophobic main chain. The interface may also include an electrocatalyst support substrate. The ionomer may be covalently bonded to the support substrate by a grafting compound so that at least some of the hydrophilic side chains are oriented toward the support substrate and the hydrophobic main chain is oriented not toward the support substrate. The grafting compound may include an epoxy group. The covalent bond may be a substrate-acetyl bond. The grafting compound may be an aromatic compound, and the covalent bond may include a hydrophilic group of the substrate and an aromatic group of the aromatic compound. The aromatic compound may be grafted onto an ionomer chain adjacent to the hydrophobic main chain. The aromatic compound may be a diazonium or iodonium compound.

[0007] In yet another embodiment, a method for forming an ionomer-electrocatalyst support interface is disclosed. The method may include forming a functionalized ionomer by reacting the ionomer with a compound having a reactive group adjacent to a leaving group. The method may also include grafting the functionalized ionomer onto the electrocatalyst support by stimulating the leaving group so that the leaving group dissociates to form a free radical on the reactive group, causing the free radical to attack the dangling bonds on the electrocatalyst support and form a covalent bond between the functionalized ionomer and the support. The method may further include passivating the remaining dangling bonds on the electrocatalyst support to cap their ends. The formation may include an addition reaction of a benzene diazonium or benzene iodonium group with the ionomer. The grafting may include forming a covalent bond between a hydrophilic group of the substrate and an aromatic group of the grafted compound. The method may also include activating the grafting reaction by a voltage change. The leaving group may include N + or I - The passivation may comprise electrochemical activation by a voltage applied to the support. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1A A non-limiting example of a fuel cell and its components is shown in exploded view;

[0010] Figure 1B A schematic diagram of a membrane electrode assembly (MEA) and its working principle are shown;

[0011] Figure 2A A schematic diagram showing a non-limiting example of an electrolyzer stack is shown;

[0012] Figure 2B Schematic diagram of the electrolysis principle;

[0013] Figure 3 shows a schematic diagram of a cathode catalyst layer (CCL) with various types of transport and water-ionomer interactions within the layer;

[0014] Figure 4 shows a conventional covering of a carbon substrate with an ionomer, resulting in an exposed carbon surface and an ionomer hydrophilic outer layer;

[0015] Figure 5 shows non-limiting embodiments of the CCL disclosed herein;

[0016] Figure 6 shows a schematic diagram of a substrate-ionomer interface according to one or more embodiments;

[0017] Fig. 7A Molecular dynamics (MD) simulations between the carbon substrate and the hydrophilic groups of the ionomer are shown;

[0018] Figure 7BMD simulations between the carbon substrate and the hydrophobic groups of the ionomer are shown;

[0019] Figure 8 A non-limiting example of a CCL having a layered structure and a hydrophobic outer layer is shown;

[0020] Fig. 9 An alternative substrate-ionomer interface is shown according to one or more embodiments;

[0021] Fig.10 is a schematic diagram of a functionalized ionomer of a compound having a reactive group and a leaving group;

[0022] Fig.11 The steps of a non-limiting exemplary reaction mechanism including a diazonium functionalized ionomer according to one or more embodiments disclosed herein are shown;

[0023] Figure 12A-12C Various configurations of reactive groups within the ionomer chain are depicted;

[0024] Figure 13A-13G shows a carbon-ionomer interface with covalent bonds facilitated by various chemistries disclosed herein;

[0025] Fig.14 A prior art substrate having a smooth surface profile is shown;

[0026] Fig.15 is a schematic diagram of a boundary layer adjacent to a first surface morphology of a substrate;

[0027] Fig.16 A non-limiting example of a first surface topography profile is shown;

[0028] Fig.17 depicts a perspective side view of a non-limiting example of a mountain-like first surface morphology;

[0029] Figures 18A-18C A top view showing a non-limiting example of a tire tread-like first surface morphology;

[0030] Fig.19A Schematic diagram showing a non-limiting example of a carrier substrate having a first surface morphology and a second surface morphology disclosed herein;

[0031] Fig.19B Schematic diagram showing a non-limiting example of a support substrate having a first surface morphology and a second surface morphology with attached electrocatalyst particles as disclosed herein;

[0032] Fig. 20shows a top schematic diagram of a non-limiting exemplary support substrate having a multi-electrocatalyst system according to one or more embodiments disclosed herein;

[0033] Fig.21A Schematic diagrams showing non-limiting examples of support substrates and multiple electrocatalyst systems having non-porous and porous surfaces;

[0034] Fig. 21B Another non-limiting example of a multi-electrocatalyst system on a support substrate is shown;

[0035] Fig. 22 shows a non-limiting example of a CCL having a multi-electrolyte system according to one or more embodiments disclosed herein;

[0036] Fig.23A Non-limiting examples of multi-electrolyte systems and their interfaces are shown;

[0037] Fig. 23B A non-limiting example of a multi-electrolyte system having a cover is shown; and

[0038] Fig.24 Depicted is a top view of a CCL having a multi-electrolyte system with a cover.

[0039] Detailed Description

[0040] Various 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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" indicating a specific value is intended to indicate a range within + / - 5% of that value. As an example, the phrase "about 100" indicates 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 indicate 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.

[0045] It should also be understood that integer ranges explicitly include all intermediate integers. For example, integer ranges 1-10 explicitly include 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Similarly, ranges 1 to 100 include 1, 2, 3, 4 ... 97, 98, 99, 100. Similarly, when any range is required, the intermediate number as 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. Similarly, whenever a list integer is provided herein, it should also be understood that the list of integers explicitly includes the scope of any two integers in the list.

[0046] In the examples described herein, the concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow, 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 one refinement, the concentrations, temperatures, and reaction conditions (e.g., pressure, pH, flow, 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, 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.

[0047] For all empirical chemical formulas represented by multiple letters and numbers in the subscripts (e.g. CH 2 O), the value of the subscript may be rounded or truncated to two significant figures, plus or minus 50% of the indicated value. 2 O, then the formula is C (0.8-1.2) H (1.6-2.4) O (0.8-1.2) In one refinement, the value of the subscript may be plus or minus 30% of the value indicated by rounding or truncation to two significant figures. In yet another refinement, the value of the subscript may be plus or minus 20% of the value indicated by rounding or truncation to two significant figures. The terms "compound" and "composition" are used interchangeably.

[0048] 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".

[0049] It should also be understood that the 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 disclosure and is not intended to be limiting in any way.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] Chemical and electrochemical systems that utilize hydrogen as a fuel source are considered the energy systems of the future, whether in direct hydrogen combustion engines or fuel cells. These hydrogen production devices are becoming increasingly popular due to their ability to produce clean energy. The system may include fuel cells, electrolyzers or electrolyzers, and battery cells. A fuel cell or electrochemical cell converts a fuel (e.g., H) into hydrogen through a pair of electrochemical half reactions (redox reactions). 2The conversion of the chemical energy of hydrogen and an oxidant into electricity has become an increasingly popular technology for hydrogen fuel cell generation. Fuel cells are now a promising alternative transport technology that can operate without emitting toxic or greenhouse gases.

[0057] Figure 1A A non-limiting example of a fuel cell, namely a proton exchange membrane fuel cell (PEMFC), is depicted. The core component of the PEMFC 10 that facilitates the electrochemical reaction required to separate electrons is a membrane electrode assembly (MEA) 12. The MEA 12 includes subcomponents such as a catalyst-coated cathode 22 and an anode 24 electrode separated by a proton-conducting ionomer or ionomer membrane 26; Figure 1B In the MEA schematic of FIG. 1 , the catalyst is indicated as 28 . In addition to the MEA 12 , the PEMFC 10 typically includes other components, such as a current collector 14 , (one or more) gas diffusion layers 16 , a gasket 18 , and (one or more) bipolar plates 20 .

[0058] The anode undergoes a hydrogen oxidation reaction (1), while the cathode undergoes an oxygen reduction reaction (2):

[0059] (1)H 2 ->2H + +2e -s

[0060] (2) 4H + +O 2 +4e - ->H 2 O

[0061] Generally speaking, H 2 The protons decompose on the surface of the electrocatalyst in the anode to form protons and electrons in the hydrogen oxidation reaction (HOR). The electrons are transported to the external circuit via the support of the anode catalyst layer, while the protons are pulled to the cathode catalyst layer through the proton exchange membrane (PEM). Once in the catalyst layer, the protons move through the ion-conducting polymer or ionomer membrane network to the electrocatalyst surface, where they combine with electrons from the external circuit and O diffused through the pores of the cathode catalyst layer (CCL). 2 Combine to form water in the oxygen reduction reaction (ORR).

[0062] In addition to fuel cells, electrolyzers provide another type of electrochemical cell. Electrolyzers use electrical energy to perform chemical reactions. Electrolyzers split water into hydrogen and oxygen through an electrolysis process, providing a promising method for producing hydrogen from renewable resources. Electrolyzers are similar to fuel cells and include anode and cathode catalyst layers separated by an electrolyte membrane. The electrolyte membrane can be a polymer, an alkaline solution, or a solid ceramic material. The anode and cathode catalyst layers of the electrolyzer contain catalyst materials.

[0063] In addition to fuel cells, electrolyzers can be used in other applications including industrial, residential and military applications, as well as technologies focused on energy storage, such as grid stabilization from dynamic power sources including wind turbines, solar cells or local hydrogen production.

[0064] A typical single electrolytic cell consists of an electrolyte membrane, an anode layer, and a cathode layer separated from the anode layer by the electrolyte membrane. Figure 2A A non-limiting schematic diagram of an electrolyzer stack 40 is shown. The electrolyzer stack 40 includes individual electrolyzer cells 31, each of which includes a membrane 32, electrodes 34, 36, and a bipolar plate 44. The anode layer 34 and cathode layer 36 of the electrolyzer stack 40 contain catalyst materials, such as a Pt-based catalyst. At the anode layer 34, H 2 O is hydrolyzed to O 2 and H + (2H 2 O→O 2 +4H + +4e - ). At the cathode layer 36, H + Combines with electrons to form H 2 (4H + +4e - →2H 2 ).

[0065] Figure 2B The electrolysis principle and related reactions employed by a proton exchange membrane (PEM) electrolyzer 30 are depicted. The electrolyzer 30 includes a PEM 32, an anode 34, and a cathode 36. Each electrode includes a porous transport layer (PTL) and a catalyst layer. During the electrolysis process, water is decomposed into oxygen and hydrogen in an evolution reaction driven electrically by the anode and cathode. The reactant liquid water (H 2 O) passes through the anode 34PTL to the anode catalyst layer, where oxygen evolution reaction (OER) occurs. + ) moves through the PEM 32, while the electrons (e-) are conducted through an external circuit during the hydrogen evolution reaction (HER) at the cathode 36 catalyst layer. The anode OER requires a much higher overpotential than the cathode HER. Due to its slow nature of four-electron transfer, the anode OER determines the efficiency of water splitting.

[0066] In general, high rates for ORR and OER are desirable. To achieve high reaction rates at the cathode, oxygen, protons, and electrons need to be transported to the catalyst particles, while the generated water is transported out of the reaction zone. At low current densities, where water is primarily present in the form of vapor, transport is addressed by (a) electrons being transported through the catalyst 51, support 50, (b) protons being transported through the ionomer 52 dispersed in the cathode catalyst layer (CCL) 54, and (c) oxygen and water being transported through the porous network 56 of the CCL 54, as shown in FIG. Figure 3 As shown schematically in FIG.

[0067] However, at high current density, the vaporization capacity of CCL 54 exceeds the water generation rate. The transport mode changes from vapor transport to liquid transport. The liquid pressure gradient gradually increases. Depending on the wettability of the pore network 56, CCL 54 may be partially submerged by liquid water. This liquid water may block the secondary pores 58 in CCL 54, hindering oxygen transport, such as Figure 3 6. The blockage is shown as a wetted droplet 60. The wetted droplet 60 represents a water-ionomer interaction in a hydrophilic system where the droplet wets the ionomer surface and becomes fixed, fixed in place, immobile within the pore network, thereby preventing transport through the secondary pores and eventually causing flooding as more droplets accumulate within the network 56. The blocked oxygen transport in turn limits the cathode reaction rate, thereby limiting the power output of the overall electrochemical cell.

[0068] In addition, typical ionomers or ion-conducting polymers include a hydrophobic backbone terminated with hydrophilic side chains. Typically, ionomers have very complex structures, such as inverted micelles, with the backbone collapsed and the hydrophilic groups facing inward, forming interconnected water domains at relatively high water activity. The hydrophilic domains serve as pathways for the transport of protons and other substances. The hydrophobic backbone can provide structural rigidity.

[0069] In the thin films of CCL, the hydrophobic and hydrophilic groups can be randomly and irregularly oriented, resulting in a hydrophilic surface, which may be undesirable. Therefore, in the typical ionomer film network of CCL, the desired hydrophobic effect does not occur due to the following factors: (1) the ionomer does not completely coat the support, thereby exposing the hydrophilic part of the substrate, (2) the layers of the ionomer (especially the outermost layer) are free to orient and reorient themselves and expose the hydrophilic side chains, thereby creating an overall hydrophilic surface that leads to water flooding, or both. Figure 4 The diagrams illustrate these principles.

[0070] While ionomers are known to attach relatively strongly to catalyst nanoparticles, their adhesion to the support itself is generally weak, resulting in areas of exposed substrate, such as carbon, especially areas of high porosity or local curvature. Incomplete coverage is problematic, especially in high surface area carbons with low catalyst loadings, due to the low surface density of the catalyst and the lack of hydrophobicity of the carbon support that may be exposed.

[0071] from Figure 4 As can be seen in Figure 5, the substrate / catalyst substrate 50 / 51 is only partially surrounded by the ionomer. Portions 57 of the support substrate 50 are exposed. The ionomer 56, if present, is shown to have a hydrophilic backbone 59 and hydrophilic side chains 61. As such, the CCL has a relatively large portion with a hydrophilic outer surface that can attract water, accumulate water, and cause oxygen transport to be less than desirable levels. Figure 4 Areas prone to flooding are marked as 63.

[0072] Therefore, efficient oxygen transport through the CCL is required to prevent flooding of the catalyst layer, the CCL, the ionomer, the porous network within the ionomer, or a combination thereof as much as possible.

[0073] In one or more embodiments, an electrochemical cell system is disclosed. The system can be a fuel cell or an electrolyzer. The system includes the components described above with respect to fuel cells and electrolyzers. The system includes a cathode having a CCL. The CCL can include or contain a substrate, a catalyst, an ionomer. The system is structured to prevent flooding of the catalyst layer, the CCL, the ionomer, the porous network within the ionomer, or a combination thereof as much as possible. Thus, the system is structured to provide increased oxygen transport through the CCL.

[0074] Throughout this disclosure, the substrate can be carbon. The carbon substrate can have a variety of forms and variations, such as graphite, graphene, nitrogen-doped graphite, carbon black, conductive carbon black, activated carbon fibers, fullerenes, nanotubes, nanofibers, etc., or a combination thereof. The substrate can include amorphous and crystalline structures. The substrate can be a porous substrate with a plurality of pores (including macropores, mesopores and / or micropores). Therefore, the substrate can include an external non-porous surface and pores dispersed in the non-porous surface and having variable depths and diameters. Alternatively, the carrier can be a metal oxide or metal, such as cobalt oxide, aluminum oxide, titanium oxide, etc., or a combination thereof. The carrier material can have a variety of morphologies and desired properties, such as high surface area, conductivity, low grit content, etc., or a combination thereof.

[0075] The electrocatalyst may be a noble metal catalyst, such as Pt, Pd, or a combination thereof. The catalyst may include an alloy, such as a PtM alloy, wherein M is a transition metal, such as Co, Mn, Ti, Ni, Al, Fe, Cu, Ru, Mo, etc. The catalyst may include Ir, Ru, Ir-M, or Ru-M alloys, wherein M is one of the above elements, or an oxide of the above elements. In some embodiments, the catalyst may mainly include Ni, Cu, Co, an oxide thereof, or a combination thereof.

[0076] The ionomer may include one or more materials. Non-limiting examples of ionomers include Nafion TM Or sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, high oxygen permeability ionomer (HOPI), non-fluorinated aromatic polymer such as poly(aryl sulfone) or a combination thereof. Non-limiting examples of the hydrophobic backbone may include polytetrafluoroethylene (PTFE) and the hydrophilic polar side chains may include sulfonate.

[0077] The CCL may be partially, substantially completely, or completely free of water flooding, wetting droplets, water blockages, or combinations thereof. Partial may mean that at least about or more than about 50%, 60%, 70%, 80%, 90%, or 95% of the CCL area, porous network area is free of unwanted water flooding, wetting droplets, water blockages, or combinations thereof.

[0078] Figure 5 1 shows a non-limiting example of a CCL disclosed herein. The CCL 154 may include an ionomer 152 and a porous network 156 within the ionomer 152, such as Figure 5 The porous network 156 may include one or more 2 The channels or pores 162 for water transport. The channels or pores 162 can be interconnected. The channels or pores 162 can be regular, irregular, or have irregular, regular, or variable dimensions, such as length, width, or both, throughout their length. The channels or pores 162 can include macropores, mesopores, micropores, or combinations thereof.

[0079] In one or more embodiments, CCL 154 may include multiple layers. The first layer may be a substrate 150 and / or a substrate / catalyst matrix 150. The second layer may be an ionomer 152. The second layer may form a thin film, a layered structure, or both. The ionomer layer 152 may be closely and / or uniformly attached to the substrate 150. The film may be uniform and have uniform dimensions, such as thickness. The film may maintain uniform dimensions even when the surface has curvature, defects, protrusions, depressions, etc. The film may be closely attached to any surface structure of the substrate or substrate / catalyst matrix. The attachment of the film to the substrate or substrate / catalyst interface is uniform, complete, sufficient, or a combination thereof. The ionomer coating 152 may be uniform, uninterrupted, and in direct contact with the substrate 150 over at least a portion or the entire area of ​​the contact area between the substrate and the ionomer. The ionomer may transport protons to the CCL and its interior.

[0080] The ionomer-substrate interface 166 may be free of gaps, interruptions, such that the substrate is substantially completely covered by the ionomer. The interface may also be free of exposed carbon hydrophilic groups, which may result in unwanted water accumulation and subsequent flooding of the ionomer. The interface may be free of exposed substrate or substrate / catalyst matrix, including areas of high porosity, curvature, uneven surfaces, or combinations thereof.

[0081] The interface 166 and substrate 150, or substrate / catalyst matrix 150 / 151, may include one or more surface oxygen or hydroxide terminations or capping groups 170, such as Figure 6 Thus, the surface may include a partially oxidized surface. Figure 6 7 , the end cap 170 is firmly bound to water, which in turn is firmly bound to the hydrophilic group 161 of the ionomer 152. Covalent bonds are represented by solid lines, while dashed lines represent hydrogen bonds. Thus, there can be covalent bonds between the substrate and the end capping group 170, and there can be hydrogen bonds between the end capping group 170, the interfacial water, and the hydrophilic group 161. The end capping group 170 can be located at the edge site of the substrate. The binding mechanism can be through a hydrogen bonding network mediated by the interfacial water firmly bound to the partially oxidized surface and the hydrophilic side groups of the ionomer, as shown in FIG7 . Thus, the substrate can include a surface chemistry that is structured to bind the ionomer to the substrate along most or substantially the entire area of ​​the substrate-ionomer interface.

[0082] Fig. 7A Ab initio molecular dynamics (MD) simulations are shown for evaluating the dilute dispersion of Nafion TM Adsorption strength on partially oxidized non-graphitic carbon. Fig. 7A The structure of (showing sulfonate and OH terminated non-graphite carbon) is Figure 7BThe net attractive interaction between the structures of (showing a non-interacting interface between OH-terminated carbon and PTFE) is -0.3 eV / SO 3 (-29 kJ / mol). Fig. 7A and Figure 7B The diagram illustrates the beneficial sulfonate-carbon binding or hydrophilic group-substrate binding compared to the hydrophobic group-substrate binding.

[0083] In one non-limiting example, the substrate may include carbon and the capping groups may be located at carbon non-graphitic edge sites. Thus, the substrate may include an ionomer adsorbed on partially oxidized non-graphitic carbon.

[0084] The substrate can be functionalized. Functionalization can result in an increased hydrophilicity of the support (e.g., carbon support). Increased hydrophilicity can result in attraction of interfacial water, thereby facilitating the binding of the substrate to the ionomer hydrophilic groups. The degree of functionalization should be such that substrate corrosion is not increased and electrical transport is not restricted. Functionalization can result in a water contact angle of less than about 90°, 89°, 88°, 87°, 86°, 85°, 84°, 83°, 82°, 81°, 80°, 79°, 78°, 77°, 76°, or 75°.

[0086] Additionally or alternatively, the CCL, porous network, channels, pores may include hydrophobic surfaces. At least some of the surfaces may be hydrophobic. The surfaces may be permanently hydrophobic. The hydrophobicity may be permanent, stable, unchanging, lasting, durable, long-lasting, unchanging, continuous, or a combination thereof. The CCL, the porous network, or both may contain permanent hydrophobic surfaces throughout. The hydrophobic surfaces ensure that water droplets formed within the network do not attach to the porous network. The hydrophobic surfaces help ensure that excess water does not accumulate in the network in the form of wetting droplets. Instead, water may aggregate into non-wetting droplets, thereby not hindering oxygen transport in the ionomer porous network. Figure 5 A non-limiting example of a non-wetting droplet is shown. In turn, a hydrophobic surface can minimize or eliminate undesirable flooding, thereby facilitating more effective and efficient oxygen transport through the CCL.

[0087] The ionomers disclosed herein can provide hydrophobicity through their backbone, their orientation, position and / or fixation within the CCL. The hydrophobic backbone affects chemical stability and repels water. The ionomer can be oriented and fixed in such a position within the CCL that the hydrophobic backbone forms the outermost layer of a film, a network, a CCL or a combination thereof. In other words, the ionomer backbone and hydrophilic groups structured to transport protons to active catalyst sites are not randomly oriented across the CCL. Instead, the orientation of the hydrophobic backbone, hydrophilic side chains or groups, or both, is predetermined and locked or fixed so that the orientation does not change under operating or other conditions.

[0088] The ionomer membrane may have a biphasic layered structure. The biphasic layered structure may be annealed, cross-linked, or both. The ionomer may have a layered structure having alternating layers of hydrophobic backbone chains and hydrophilic side chains, such as Figure 8 The outermost layer 172 of the layered structure or film comprises a hydrophobic backbone 159. The outermost hydrophobic layer 172 is fixed so that the ionomer does not reorient and the hydrophilic groups 161 do not change position relative to the hydrophobic backbone 159.

[0089] Figure 8 Two hydrophobic backbone layers and two hydrophilic group layers are depicted, but different numbers of layers are contemplated. For example, as long as the outermost layer 172 is hydrophobic, it is contemplated to use 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more alternating layers.

[0090] Although the surface of the ionomer may be hydrophobic under equilibrium dry conditions, after prolonged exposure to moisture, the surface may become hydrophilic due to polymer chain rearrangement exposing hydrophilic polar side chains to surface moisture. To prevent this transition and maintain the resulting structure hydrophobic, the surface of the ionomer may be cross-linked. To prevent or reduce ionomer chain reorientation, and thereby maintain a hydrophobic surface structure, a cross-linkable additive may be incorporated into the ionomer to form an interpenetrating network structure.

[0091] Disclosed herein is a method for increasing the hydrophobicity of a CCL. The method may include one or more steps or stages. These steps or stages may be used alone or in combination to achieve the desired structure of the CCL, ionomer, and ionomer-substrate interface described above.

[0092] The method may include preparing CCL by ink dispersion. The method may include mixing powders of carbon support and catalyst with ionomer in a water-solvent dispersion. The method may then include doctor blade coating, drying, or both. The method is not dependent on, nor does it negatively affect, catalyst content or substrate loading.

[0093] The first step may include attaching the substrate or substrate-catalyst substrate-ionomer interface to each other. The method may include improving the bonding between the ionomer and the substrate. The method may include covering at least about 50%, 60%, 70%, 80%, 90%, 95%, 99% or 100% of the surface area of ​​the substrate with the ionomer so that the ionomer is uniformly, completely and fully attached to the substrate. The method may include removing any exposed hydrophilic portions of the substrate. The removal may include covering with an ionomer, a capping group, a hydrophilic group, a hydrophilic portion of the ionomer, or a combination thereof.

[0094] The method may include functionalizing or introducing functionalization to the substrate. The method may include introducing one or more capping groups onto the surface. The capping groups may be oxygen, hydroxide, or both. The method may include introducing capping groups at substrate edge sites (e.g., in non-graphitic regions of a carbon substrate). The method may include initiating a binding mechanism between the substrate and the hydrophilic groups of the ionomer. The method may include covalently bonding the substrate to the capping groups. The method may include bonding the capping groups to interfacial water via hydrogen bonds. The method may include bonding the interfacial water to the hydrophilic groups of the ionomer via hydrogen bonds. The method may include introducing a binding mechanism via a hydrogen bond network mediated by interfacial water firmly bonded to the partially oxidized surface and the hydrophilic side groups of the ionomer.

[0095] The first step may be performed before the ionomer is introduced into the substrate-catalyst mixture by doctor blade coating, drying, or both. The first step may be performed by one or more of the following actions. The first step may include functionalizing the substrate by washing the substrate powder in a strong base or an oxidizing agent. Non-limiting examples of bases may include aqueous NaOH or KOH solutions. Non-limiting examples of oxidizing agents may be weak acids under oxidizing conditions. The first step may include exposing the carbon support to ozone and / or ultraviolet light for about 5-15 minutes to functionalize the substrate. The first step may include exposing the support to O3 prior to the ionomer dispersion step. 2 The plasma is applied for about 5 to 15 minutes to functionalize the substrate. 2 The plasma works by functionalizing oxygen and hydroxide on the carbon substrate. The method can include adjusting the degree of functionalization to the above water contact angle using standard water contact angle measurements. Over-functionalization may undesirably increase carbon corrosion or reduce electrical transport.

[0096] In a second step, the method may include making the CCL hydrophobic or permanently hydrophobic. The method may include generating a permanent hydrophobic surface throughout the CCL pore network. The method may include promoting the reorientation of the ionomer backbone and side chains so that the side chains face the substrate and the backbone is pushed away from the substrate to form the outermost layer of the ionomer film. The method may include repositioning the side chains and backbone of the ionomer as described herein. The method may include annealing to achieve reorientation of the ionomer portion. The method may include driving the ionomer to assemble into a structure that maximizes the surface area of ​​the hydrophobic backbone.

[0097] The second step can be performed after coating the ionomer onto the substrate or substrate / catalyst matrix. The coating can produce alternating layers of side chains and backbone chains. The method can include annealing to form an outermost hydrophobic layer by pulling the backbone chains outward away from the substrate and orienting the side chains inward toward the substrate within the thin ionomer film.

[0098] Annealing can be carried out in a non-polar solvent vapor (e.g., hexane, benzene, toluene, chloroform, etc.), or in a mixed solvent vapor with a high partial pressure of non-polar solvent vapor and a low partial pressure of polar solvent (e.g., water). The method may include repelling the hydrophilic side chains through their interaction with the non-polar solvent. The method may include adjusting, maintaining, maintaining or introducing a relatively low humidity level to prevent the ionomer from completely dehydrating during the annealing process. The method may include adjusting the temperature to prevent condensation of solvent vapor, excessive dehydration of the ionomer, and allowing sufficient mobility of the hydrophobic backbone to achieve surface reconstruction.

[0099] The method may include a third step: cross-linking. The cross-linking may be surface specific cross-linking to lock the outer backbone of the ionomer in place, prevent subsequent rearrangement of the ionomer structure, maintain the hydrophobicity of the outermost layer of the CCL, or a combination thereof.

[0100] Crosslinking can be promoted by inducing bonding across the hydrophilic side chains or hydrophobic backbone of the ionomer. The method can include subjecting the treated membrane to UV radiation curing. The radiation dose and duration can be optimized so that crosslinking is limited to the surface of the ionomer coating. Excessive crosslinking of the ionomer bulk may adversely affect proton transport.

[0101] Alternatively, crosslinking can also be achieved by adding a crosslinkable additive to the ionomer. This method can include creating an interpenetrating network to limit large-scale reordering of the ionomer membrane. Non-limiting examples of crosslinkable additives can be polyvinylidene fluoride (PVDF) polymers and divinylbenzene molecules, which are crosslinked with Nafion TM It exhibits good miscibility and can be cross-linked by electron beam. The resulting PVDF / divinylbenzene network can reduce the reorientation of the ionomer chains, thereby maintaining the desired hydrophobic surface structure.

[0102] The method may further comprise exposing the solvent-vapor annealed carbon / catalyst / ionomer structure to perfluoroheptane (C 7 F 16 ) / Ar plasma mixture to stabilize the hydrophobic surface structure.

[0103] Alternatively or additionally, another interfacial chemical structure and interfacial physical and / or chemical bonds can improve oxygen transport within the CCL, facilitate uniform dispersion of the ionomer on the substrate, and / or improve the chemical stability of the CCL. Fig. 9 A non-limiting example of this interface can be seen in .

[0104] like Fig. 9 As shown, the interface 266 includes a substrate 250 and an ionomer 252, the ionomer 252 having at least one hydrophilic group 261 and a hydrophobic backbone 259. A non-limiting example of a hydrophilic group may be SO3 (H). A non-limiting example of a hydrophobic backbone may be Nafion TM Or HOPI hydrophobic backbone or chain portion. Interface 266 can include substrate 250 covalently bonded to ionomer 252. The interface additionally includes compound 280 having a reactive group labeled R. Compound 280 promotes, enables, mediates and / or provides covalent bonding between substrate 250 and ionomer 252.

[0105] The compound can be attached to the support 250 via the reactive group R and attached to the ionomer 252 via a carbon adjacent or immediately adjacent to a hydrophilic group, a hydrophobic group, a backbone, a side chain, a main chain, or another position along the ionomer chain by one or more of the following mechanisms. The compound can include one or more aromatic rings. The aromatic rings can include simple aromatic rings, such as benzene rings. The compound can be a simple aromatic ring compound. The compound can be a non-aromatic, free or aromatic ring. The compound can be an iodine compound. The compound can be a grafted compound.

[0106] The compound may be a compound or composition having a leaving group X derived from a reactive group R. After the leaving group X is detached from the compound, a covalent bond may be generated between the reactive group R and the substrate. The covalent bond may be a substrate-acetyl bond, a C-acetyl bond, a substrate-aryl bond, a C-aryl bond, a substrate-OC bond, a -COC bond, a substrate-O-Si- bond, -Si-OC, a substrate-NH-, a C-NH- bond, etc. The interface 266 may include a substrate 250 having a covalent bond bonded to an aryl group, an acetyl group, an amine group, an isocyanate group, an epoxy group, or other groups listed herein.

[0107] Thus, non-limiting examples of reactive groups include aryl (derived from simple aromatic ring compounds by removing a hydrogen atom from the ring), alkyl, epoxy, carboxyl, anhydride, peroxide, halogen, acid chloride, isocyanate, amide, amine, and the like, or combinations thereof.

[0108] Non-limiting exemplary compounds include diazonium, iodonium, silane, epoxide, carboxylic acid, anhydride, peroxide, halogen, acid chloride, isocyanate, amide, etc., or combinations thereof. Non-limiting examples of leaving groups include N + ≡N, N + , H + , O - 、-OH-CR 1 =O, Cl - ,I - wait.

[0109] The covalent bonding between the substrate and the ionomer enables strong adhesion between the ionomer and the substrate, thereby improving oxygen transport and the overall efficiency and performance of the catalyst and electrochemical cell. Therefore, the covalent bonds disclosed herein have advantages over traditional substrate-ionomer interfaces (which may be carbon non-bonded interfaces).

[0110] Additionally, interfaces having hydrogen bonding between ionomer side groups and substrate surfaces are described above. While hydrogen bonding is desirable at substrate non-bonding interfaces, in at least certain arrangements of electrochemical cells, it may be beneficial to introduce stronger bonds between the substrate and the ionomer.

[0111] A hydrogen bond is a relatively weak attraction between a partially positively charged hydrogen atom and a more electronegative atom or group. Hydrogen bonds are weaker than covalent bonds, which are connections between two atoms that result from the sharing of an electron pair. The positively charged nuclei of the two atoms are electrostatically attracted to the same electrons, and a bond is formed when the total energy of the bonding atoms is lower than the total energy of the two separate atoms. Since forming a bond lowers the total energy, a relatively high energy is required to break the bond. This means that the ionomer and substrate interface has a higher stability than that provided by hydrogen bonding.

[0112] In addition to improved chemical stability, covalently bonding the ionomer to the carrier substrate in the CCL has additional advantages. Functional ionomers directly bonded to the carrier substrate surface can also promote more uniform dispersion of the ionomer on the substrate. Uneven ionomer dispersion has been shown to result in increased resistance to mass transport. Poor ionomer dispersion can form exposed carrier substrate areas that lack convenient proton conduction pathways in the absence of the ionomer. Alternatively, poor dispersion can form areas where the ionomer layer is abnormally thick, thereby increasing oxygen transport resistance. In addition, uniform ionomer dispersion can improve durability to corrosion or make the material less susceptible to corrosion.

[0113] The substrate may further include one or more exposed, dangling, hydrophilic bonds and / or hydrogen terminated edges of the support, which may result in oxygen transport resistance, as described above. At least some of the dangling bonds 282 may be capped, passivated, or terminated, such as Fig. 9 Thus, the substrate may include capped, passivated, or terminated bonds 282. Removing exposed or hydrophilic bonds can prevent several adverse effects including flooding.

[0114] Passivating the exposed bonds of the substrate can have several advantages. Exposed bonds terminated with reactive molecules can lead to unwanted side reactions during the operation of the electrochemical device. Therefore, by passivating these bonds by terminating them with molecules that may not be removed during normal operation, the exposed bonds can be prevented from undergoing unwanted side reactions during the operation of the cell. In addition, the passivated bonds can reduce the likelihood of the material being oxidized in the presence of oxygen. Therefore, passivating unused exposed bonds can improve the corrosion resistance and efficiency of the electrochemical system.

[0115] The electrochemical system or CCL may include a substrate having fully or at least partially capped dangling bonds. Thus, the support may include capped hydrophilic bonds and covalent bonds formed between the substrate and the ionomer by the grafting compound.

[0116] A method for forming the above-mentioned covalent bonding interface is disclosed. The method may include one or more steps. The method may include functionalizing the ionomer by chemical treatment to introduce a compound, a grafting compound, a reactive group R or a combination thereof. Fig.10 A non-limiting example of a functionalized ionomer 252 is shown prior to bonding to a substrate 250. The functionalized ionomer includes a compound 280 having a reactive group R. The reactive group R has a leaving group X.

[0117] The method may also include detaching the leaving group X from the compound 280. The detachment may include electrical stimulation, heating, exposure to ultraviolet light, addition of a chemical reactant, generation, redirection of electrons, or a combination thereof. The stimulation may be provided by electrons present in the system or electrons donated to the system.

[0118] The method may include attaching the functionalized ionomer to the substrate using a grafting method. The method may include breaking the bond between the reactive group R and the leaving group X. Breaking may include generating free radicals. The method may include grafting using reactive groups. Grafting may include anionic grafting, cationic grafting, atom transfer radical polymerization or free radical polymerization. Non-limiting examples of methods for initiating grafting may include thermal treatment, photochemistry, acid treatment, reduction reaction, hydrolysis, electrochemical pulse or application of voltage. The method may utilize ultraviolet treatment, but may produce undesirable by-products and decomposition.

[0119] The method may include providing a voltage source, applying a voltage, or both, to enable deprotonation of a compound or a portion thereof (e.g., an acid). For example, a voltage may be applied with a carboxyl group to deprotonate an -OH group.

[0120] The process can utilize the "scissors" provided by the thermal / hydrolysis treatment. The process can include removing or severing anhydride bonds and creating C-acetyl bonds between the substrate and the ionomer.

[0121] The method may include free radical terminated olefin grafting. The method may utilize free radicals formed on the substrate surface. The method may then include reacting the olefin terminated ionomer with free radicals formed by benzoyl peroxide or other treatment to covalently bond the ionomer to the support.

[0122] After the bond between the reactive group R and the linking group X is broken, the leaving group X can form a separate, chemically stable compound. The reactive group R may then be in a highly reactive state, allowing the functionalized ionomer to be Fig. 9 The covalent bond shown is bonded to the substrate. The substrate may be bonded to the reactive group R via a dangling bond, such as a dangling bond terminated with an -OH group.

[0123] The method may include shielding, masking or otherwise covering any, all or at least some of the electrocatalyst particles to prevent grafting to the catalyst surface resulting in an undesirable loss of catalytically active surface area.

[0124] Fig.11 A schematic diagram of a non-limiting exemplary reaction mechanism including compounds disclosed herein is shown. An exemplary compound is a diazonium functionalized ionomer. The reactive group can be a diazonium salt. A non-limiting example includes benzene diazonium bonded to an ionomer, the ionomer portion being Fig.11 The diazonium salt has a positively charged N atom. This corresponds to high reactivity, where N + The atom can easily leave the rest of the molecule. The leaving group is represented by two N atoms attached to the benzene ring. Fig.11 It can be seen from the steps that initially, the functionalized ionomer includes a leaving group N + Compounds with reactive groups ≡ N. N in the leaving group + The ionomer is attacked by a free electron, causing the leaving group to detach and form a free radical on the aromatic ring of the compound. Subsequently, since the free radical makes the aromatic group highly reactive, the ionomer is attracted to the substrate and binds to it via a covalent bond. The reaction product is N 2 , it is very stable, inert, and can be easily removed from the electrochemical cell after the grafting process.

[0125] Fig.11 An ionomer having a reactive group adjacent to a hydrophilic sulfonate group on the ionomer is shown. Figures 12A-12C Other locations or configurations of the reactive group R within the ionomer chain are contemplated and depicted in FIG.

[0126] Alternative grafting chemistries may include silanes, forming -Si-OC bonds, with the final product being Fig.13A As shown; epoxide, forming -COC bond, the final product is as Fig. 13B, 13C As shown; carboxyl, the final product is as Fig.13D and 13E As shown; anhydride, the final product is as Fig.13F As shown, or olefins, the final product is as Figure 13G Although Figures 12A-12C While fluorinated polymers are depicted in 13A-13G, other chemistries for the ionomers may be substituted or combined, such as hydrocarbons, aromatics, and amides.

[0127] The method may further include passivating dangling bonds or exposed bonds. The method may utilize small molecules that are structured to terminate dangling bonds and are not removed during normal operation of the electrochemical cell. Non-limiting examples of passivation techniques include halide termination by immersion in a weak halide acid; aryl termination by further diazonium exposure; termination with a single atom catalyst such as Fe, Co, Ni or Cu, a radical scavenger such as Ce or its organometallic complex; carbon monoxide termination; plasma, vacuum, ultraviolet or annealing processes; or the above methods combined with a voltage applied to the substrate to electrochemically activate the passivation reaction.

[0128] In addition, alternatively or additionally, a catalyst support modified to enhance oxygen diffusion in nanopores is disclosed. The modified surface introduces increased pore roughness. Without limiting the present disclosure to a single theory, it is believed that the rough morphology of the surface of the support substrate pores disclosed herein can provide surface diffusion paths for gaseous species in a confined medium (e.g., the pores of an electrocatalyst support). Therefore, increasing the surface roughness of the support by chemical, thermal, electrochemical or other means can help alleviate the transport barriers common in high surface area carbon (HSAC) supports.

[0129] like Fig.14 As shown, a conventional CCL 54 includes nanoparticles / electrocatalysts 51 deposited on top of an electron-conducting support 50. The electrocatalyst 51 and / or support 50 may be dispersed in an ionomer 52 surrounding the catalyst / support substrate 50 / 51. Each component of the CCL plays a unique role. The electrocatalyst 51 may catalyze the reaction, the support 50 may provide mechanical and electrical stability to the electrocatalyst 51, and the ionomer 52 may transport reactant and product species to and from the electrocatalyst 51. Fig.14 It can be seen that the support surface is generally a smooth, wavy surface with no abrupt changes in morphology.

[0130] One challenge of CCL is to ensure the high level of mass transport required for reactions at high current densities. An ionomer-related attempt to address the transport level issue is to replace Nafion with HOPI. TMand other ionomers. This substitution reduces the equivalent weight, shortens the side chain length, and introduces a more rigid structure to the ionomer backbone. But the weakness of this substitution stems from the adsorption of the ionomer backbone, side chains and / or functional groups to the catalyst surface. Adsorption can hinder activity through steric effects. In other words, adsorption creates a metaphorical traffic jam in which reactants are blocked from reaching or leaving the electrocatalyst. Another attempt to address the transport challenge is to use HSACs characterized by high microporosity and mesoporosity. HSACs strive to eliminate contact between catalyst and ionomer. But the elimination of contact manifests itself as increased transport resistance.

[0131] Therefore, there is a need for a support substrate that is conducive to oxygen transport to the electrocatalyst, achieves a high level of mass transport at high current density, and simultaneously provides a good structural support for the electrocatalyst.

[0132] The catalyst supports disclosed herein can have a porosity formed by a plurality of pores. These pores can be key to mass transport of products and reactants of the electrochemical cell reactions described herein. The pores can be classified into three general groups: micropores, which have a diameter less than about 2 nanometers; mesopores, which have a diameter between about 2 and 50 nanometers; and macropores, which have a diameter greater than about 50 nanometers.

[0133] From the perspective of pore size distribution, the substrate can include at least some, most or major pores whose size is adjusted to fit the electrocatalyst particles but prevented from being penetrated by the ionomer. The catalyst support can have a maximum amount of mesopores, micropores, pores with a diameter less than about 10 nanometers, or a combination thereof. The amount or volume of the macropores in the support disclosed herein can be about, at least about, or at most about 30-70%, 40-60%, or 50-55% based on the total amount or total volume of the substrate pores. The amount or volume of mesopores and micropores can be about, at least about, or at most about 30-70%, 40-60%, or 50-55% based on the total amount or volume of the substrate pores in its combination. Other particle pore distributions are also considered.

[0134] The pore distribution can make the ionomer disperse evenly on the substrate, the supported electrocatalyst particles, and prevent the electrocatalyst from being blocked by the ionomer side chains, thereby optimizing proton transport. The pores can be wide enough and shallow enough to effectively transport oxygen to the electrocatalyst without causing transport losses due to excessive tortuosity. The width and depth of the pores should also be such that the electrocatalyst particles can be accommodated within the pores.

[0135] In pores with diameters greater than about 20 nanometers, the diffusion of molecular oxygen within the pores is primarily controlled by the interaction of oxygen with water. In pores with diameters of about 20, 15, or 10 nanometers or less, in addition to the interaction of oxygen with water, diffusion is also affected by the interaction of molecular oxygen with the pore walls. It was surprisingly found that roughening of the pore wall surface introduces and / or increases oxygen-wall interactions, adsorbing molecular oxygen to the wall surface where the electrocatalyst particles are located and forming a boundary layer adjacent to or in close proximity to the pore wall surface. Adsorption also increases the overall solubility of confined water, thereby increasing the overall permeability of the pore.

[0136] Fig.15 This principle is demonstrated in which a catalyst support 350 is shown having a rough surface 384. It can be seen that a greater volume of molecular oxygen 386 exists immediately below the boundary line B and adjacent to the rough surface 384 than above the boundary line. The area between the rough surface of the first surface morphology 384 and the boundary line B is the boundary layer 387. This occurs despite the fact that the area / volume below the boundary line B is smaller than the area / volume above the boundary line B.

[0137] The carrier substrate may include a first surface morphology and at least a second surface morphology. The first surface morphology is a surface morphology of one or more pores, at least some pores, micropores, mesopores, or a combination thereof. The first surface morphology is a pore morphology. The first morphology 389 may include a rough surface structure, arrangement, framework, surface geometry, non-limiting examples of which are Fig.16 The first morphological surface may be uneven, irregular, have height variations or deviations, indentations, micro-asperities, protrusions, blocks, non-flat areas, raised surfaces, etc., or a combination thereof. Fig.16 As shown, the first form may have a profile showing one or more walls 390, peaks 391, and valleys 392. Walls 390 may be steep, gradually sloping, abrupt, regular, irregular. Walls 390 may form peaks 391 and valleys 392. Peaks 391 may form ridges, protrusions, bumps, bumps, indentations. Valleys 392 may form cavities, depressions, indentations, concavities.

[0138] Peaks 391 and valleys 392 may have the same or different sizes, shapes, configurations throughout the first surface morphology. For example, at least some of the peaks and valleys may differ in height, width at the top of the peak, width at the bottom of the peak, or both. At least some or all of the peaks and / or valleys may have the same size or shape.

[0139] The peaks 391 and valleys 392 may form a pattern. The peaks may form a continuous, interconnected series of linear peaks, such as Fig.17Or as shown in 18C. The pattern can be regular, irregular, repeated, continuous, discontinuous, uninterrupted. The pattern can resemble mountains, tire treads, scattered islands, etc. More than one pattern can be provided on the same first surface form. Fig.17 A non-limiting example of a mountain-shaped first surface morphology 389 is shown. Figures 18A-18C A regular tire tread-like first surface topography 389 is shown. Alternatively, the pattern of first surface topography may include an alligator-skin-like topography or a bone marrow-like topography.

[0140] A single catalyst support may have one or more rough surface morphology patterns. One or more supports of the same CCL or electrochemical cell may have the same first surface morphology. Alternatively, each or at least some of the catalyst supports may differ in their first surface morphology.

[0141] Peaks and valleys may alternate in a regular, irregular, or repetitive manner or pattern. Peaks and valleys may form waves. The wave or waviness is related to the spacing between peaks, which may be regular or irregular. The pattern of peaks and valleys may form an oscillation or a repeating pattern with the same repetition or periodic variation. The wavelength and frequency of the repeating pattern may be regular over the entire carrier region. Wavelength refers to the distance between two adjacent peaks. Frequency refers to the number of times a peak is repeated per set distance. A high frequency may be about 0.5 or more peaks per 1 nm. A low frequency may be less than 0.5 peaks per 1 nm. The wavelengths and frequencies in one or more patterns described herein may be the same or different over the entire carrier region. The wavelengths and frequencies may be consistent or inconsistent. The pattern may be a sinusoidal pattern. The pattern may include consistent, high-frequency, short spatial wavelength oscillations, at least some changes in longer wavelengths, or a combination thereof. The first surface morphology may include low-frequency micro-convex bodies, making the surface appear smooth overall, but rough at a smaller scale.

[0142] The carrier substrate may also include a second surface morphology that may be free of peaks, valleys, series of peaks, or combinations thereof. The second surface morphology may be relatively smooth, having a uniform and regular surface or consistency, without perceptible protrusions, lumps, or indentations. The second surface morphology may be substantially horizontal, having the same height over the entire carrier area.

[0143] Surface roughness may be defined as Ra. The Ra value of the first surface morphology may be greater than the Ra value of the second surface morphology. Fig.19AA non-limiting example of a first surface morphology 389 and a second surface morphology 395 is shown. The first surface morphology 389 is located in the first pore 396 of the catalyst support 350, while the second surface morphology 395 is located outside the first pore 396 and inside the second pore 396'. The Ra1 value of the first surface morphology 389 is greater than the Ra2 value of the second surface morphology 395. The first pore 396 can be a mesopore or a micropore. The second pore 396' can be a macropore or a mesopore with a diameter greater than about 10 nanometers.

[0144] The electrocatalyst particles 351 may be contained or accommodated on the first surface topography along, on, at, or between contour peaks, valleys, ranges, and / or walls. Fig.16 One non-limiting example of electrocatalyst attachment is shown. Fig.19B Another non-limiting example of a second surface morphology where an electrocatalyst is attached or adhered to a pore is shown. Fig.19B In the embodiment of the present invention, a plurality of electrocatalyst particles are attached to the inner wall of the pore 396. The inner wall has a first surface morphology 389 characterized by peaks 391 and valleys 392. The profile of the pore 396 includes a rough surface having Ra1. Fig.19B The specific placement of particles 351 within pores 396 shown is exemplary only. The electrocatalyst particles may be located at the top, middle, or bottom of the pores. The increase in roughness enables the particles to better attach to the pore walls compared to pores with lower roughness or the non-porous surface of the substrate having the second surface morphology (denoted as Ra2).

[0145] The electrocatalyst particles may be attached to the second surface morphology. This attachment may be weaker than the attachment to the first surface morphology characterized by greater roughness. Therefore, it may be desirable to contain the electrocatalyst particles or a majority of the electrocatalyst particles in the pores having the first surface morphology.

[0146] The first surface morphology can have a length that is the entire length of the pore. Alternatively, a portion of the pore can include the first surface morphology and at least one different portion can include the second surface morphology. The pore having the first surface morphology can have a diameter of about 2-10, 1.8-9, or 1.5-8 nm, a depth of about 0.5-15, 1-12, or 2-10 nm, or a combination thereof.

[0147] A method of forming a first surface morphology is disclosed herein. The method may include one or more steps. The method may include forming a roughness. The roughness may be predetermined, specially designed, or randomly formed. The method may include forming pores. Alternatively, the method may include roughening a substrate having pores. The pore size distribution may be designed by adjusting the degree of the related art by varying the duration and energy of the process.

[0148] The method may include using a shield or mask to protect one or more regions and / or pores of the substrate from roughening.Thus, the final substrate may include the first surface morphology or roughness and the second surface morphology or roughness described above.

[0149] The method may include physically ablating the rough surface from the carrier surface. Non-limiting techniques for achieving such ablation may include the use of heat, high energy ions, or mechanical grinding. Additionally or alternatively, the method may include adding carrier material to an existing carrier surface to increase height, form peaks, valleys, mountains, and overall roughness. Non-limiting material addition techniques may include atomic layer deposition, chemical vapor deposition, sputtering, or surface adsorption of organic molecules (e.g., hydrocarbons, graphene, graphite, etc., or combinations thereof).

[0150] The method may also (or alternatively) include electrochemically roughening the surface by pre-etching. The method may include applying a high voltage to the support and / or subjecting the support to an acidic environment. Using any of these techniques, a certain amount of carbon may be oxidized and detached. The method may include exposing the support surface to reactive ions, such as reactive ion etching (RIE) or to reactive vapors to produce a first surface morphology. The vapor may contain other small molecules that react with the surface, such as hydrocarbons or molecules with aromatic rings. Some molecules may be retained at the end of the treatment to prevent corrosion.

[0151] The method may include changing the support to have different levels of pore structure, including micropores, mesopores and macropores. This change in pore structure level can be achieved by changing process conditions such as ion etching, chemical reaction, and mechanical grinding, which can affect the ratio of microporosity to mesoporosity.

[0152] When the support is a carbon-based support, additional techniques may be used to minimize corrosion. The method may include passivating the substrate. Passivation may include exposing the support to a vapor or solution of a small molecule to cap dangling bonds in the surface. Small molecules may be selected to prevent corrosion. Examples of such molecules may include, but are not limited to, insoluble carbon or halides. Passivation may include heat, plasma, vacuum, ultraviolet light, or annealing processes to cap dangling bonds in the carbon surface. Passivation may be electrochemically activated. The method may include applying a voltage to induce bond formation between dangling bonds on the carbon surface and reactive molecules in the surrounding electrolyte. Non-limiting examples of reactive molecules may include diazonium salts.

[0153] Electrocatalysts play a vital role in electrochemical cells because they enable HOR, HER, ORR and OER reactions. Electrocatalysts are usually contained in the form of particles. In order to increase their stability and prevent their loss due to dissolution or detachment, the electrocatalyst can be attached to a support, such as described above. The most commonly used catalysts are noble metals, such as platinum (Pt), palladium (Pd) or combinations thereof and Pt alloys PtM, where M is a transition metal.

[0154] The durability of electrocatalysts in electrochemical processes is an interesting topic to ensure stable performance of electrochemical cells and devices. For example, the stability of Pt nanoparticles (NPs) in PEMFC is a major technical challenge for PEMFC commercialization. Pt dissolution is often observed when PEMFC operation cycles enter the oxide formation voltage (>0.9V).

[0155] Carbon-supported electrocatalysts are currently the most widely used electrocatalysts in PEMFCs and are also the main contributor to PEMFC cost. Despite the maturity and improved performance of PEMFCs, their lifetime and stability are greatly limited by catalyst corrosion and degradation processes occurring on the catalyst surface, resulting in mass loss, structural evolution and / or reduction of the catalytic electrochemically active surface area (ECSA). In addition, precious metals such as pure Pt are very expensive.

[0156] Alternative electrocatalysts such as Pt alloys can offer cost savings, but they face challenges such as lower durability and undesirable changes in catalytic activity due to alloy degradation. In other words, alloy electrocatalysts may not have substantially constant performance throughout the lifetime of the alloy electrocatalyst.

[0157] In general, there is a need for improved, more stable, lower cost electrocatalysts having overall stable performance for use in electrochemical cells.

[0158] In one or more embodiments, an electrochemical cell system is disclosed. The system can be a fuel cell or an electrolyzer and includes the above components. The system includes an electrocatalyst in the CCL, the anode catalyst layer, or both, which can be referred to as a "multi-catalyst."

[0159] Multi-catalyst may refer to a system of at least two types of electrocatalysts that differ from each other in chemical composition, structure, size, function, physical properties, chemical properties, location within the system, or a combination thereof.

[0160] For example, a multi-catalyst system can include a first electrocatalyst that is more stable but may cost more than a second electrocatalyst for the same amount of catalytic activity. Non-limiting examples of expensive but more durable first electrocatalysts may be pure Pt, Pd, or a combination thereof. Due to the durability of the first electrocatalyst, it can be placed, accommodated, or attached to a non-porous surface region of a substrate. The non-porous surface region may be a non-porous surface region or an outer surface region. Since the first electrocatalyst is firmly bonded to the non-porous surface region, its relative exposure position attached to the outer, non-porous, non-porous surface region may be optimal. The first electrolyte may have a higher catalytic activity than the second electrocatalyst at the same mass / mass unit.

[0161] In order to provide manufacturing cost savings, a second electrocatalyst may be introduced so that the loading of highly catalytically active pure precious metals can be reduced without sacrificing the overall catalytic activity of the electrocatalyst system, CCL, and / or battery. The second electrocatalyst may be lower in cost than the first electrocatalyst, but also less durable or more susceptible to degradation. A non-limiting example of a second electrocatalyst may be a PtM alloy, where M may be a transition metal. At the same mass / mass unit, the second electrolyte may have a lower catalytic activity than the first electrocatalyst.

[0162] Because the second electrocatalyst is more susceptible to degradation, its placement may be different from the first electrocatalyst. The second electrocatalyst may be placed in a relatively shielded or protected portion of the carrier substrate. These portions may include porous portions of the substrate. The porous portion may include a plurality of pores, including macropores, mesopores and / or micropores. The porous portion may include a porous surface area. The second electrocatalyst may be contained in at least a portion of the pores, in a cavity of the pores, each cavity being defined by a wall. The second electrocatalyst may be contained only in mesopores. The second electrocatalyst may be contained in mesopores and micropores. Based on the total number of pores in the carrier substrate area, the second electrocatalyst may be contained in at least about 30%, 40%, 50%, 60% or 70% of the pores.

[0163] The second electrocatalyst may be located on the pore wall, the pore bottom, the pore top, or a combination thereof, such as Fig.21A , 21B The surface of the pores can be modified as described above to increase adhesion.

[0164] It is contemplated that the first electrocatalyst may be located in at least some of the pores, such as macropores, in addition to being located on the outer surface region of the support substrate. It is also contemplated that at least some particles of the first electrocatalyst may be adjacent to or in close proximity to one of the pores, such as being located on the outer surface of the pore, such as Fig. 21BAlternatively, the first electrocatalyst may be primarily located at a distance from the pores that is greater than the macropore, mesopore and / or micropore diameter.

[0165] It is also contemplated that at least some of the pores may include a mixture or blend of the first and second electrocatalysts. The blend may include up to about 30% of the first electrocatalyst based on the total number of electrocatalyst particles in the pores.

[0166] The concentration of the first electrocatalyst particles along or within the outer surface region of the support substrate can be uniform or regular. Alternatively, the spacing or concentration can be irregular. A higher concentration of the first electrocatalyst can be in one or more pores that are adjacent or in close proximity.

[0167] In addition, the concentration of the second electrocatalyst may be greatest in the pores. However, at least some of the second electrocatalyst particles may be located on the outer surface of the pores, on one or more outer edges of the pores, on the outer or external surface of the pores, or a combination thereof, such as Fig. 21B shown.

[0168] Thus, the support substrate and / or the multiple catalyst system can have one or more regions having both the first and second electrocatalysts.The one or more regions can include pore edges, outer portions of pores, outer surface-pore interfaces, or combinations thereof.

[0169] Fig. 20 A non-limiting example of a multi-catalyst system 499 implemented on a carrier substrate 450 is shown. The multi-catalyst system includes a first electrocatalyst 497 located on a non-porous surface area of ​​the carrier substrate 450. The multi-catalyst system 499 includes a second electrocatalyst 498 located in a plurality of pores 496. The pores may contain an electrolyte. The electrolyte may be the same or different from the electrolyte contacting the non-porous outer surface. The pores may have a rough surface. The pores may have the same or different size, height, width, depth, roughness, shape, configuration.

[0170] The pores may have walls 473 that gradually slope from the outer surface toward the pores. The walls of the pores may have an angle of about 45 to 135 degrees relative to the outer surface. The pores may be large enough to accommodate one or more second electrocatalyst particles. One or more may be about 1-10, 2-8, or 3-5 particles. The second electrocatalyst particles may be accumulated, dispersed, uniformly dispersed, or randomly located within the pores.

[0171] Fig.21A An alternative view of a non-limiting example of a multi-catalyst system 499 is shown. The system includes a first electrocatalyst 497 located on a non-porous surface region 471 of a carrier substrate 450. The system also includes a second electrocatalyst 498 located or contained at a different depth in the pore cavity 496 shown. Fig.21A In a non-limiting example, the second electrocatalyst particles 498 have a diameter smaller than that of the first electrocatalyst particles 497 and are dispersed in a bottom portion of the pore cavity 496 .

[0172] In the context of a CCL, the pores are filled with an electrolyte, such as ionomer 452. The same or different ionomer may contact or surround the outer surface of the carrier substrate 450 and the inner volume of the pores 496, as will be discussed further below.

[0173] exist Fig. 21B In the non-limiting example of , the first electrocatalyst is located on the outer surface area of ​​the support substrate 450, but is also located on the top edge of the wall 473 that defines the pore 496. Therefore, the first electrocatalyst particle 497 is directly adjacent to the pore 496. Alternatively, the electrocatalyst particle 497 can be a particle of the second electrocatalyst 498. Fig. 21B In the non-limiting example of , the second electrocatalyst particles 498 have a larger diameter than the first electrocatalyst particles 497, and the pore shape protects the second electrocatalyst particles 498.

[0174] The ratio of the first electrocatalyst to the second electrocatalyst, or vice versa, can be about 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 2:3, 4:5, etc. The carrier substrate, CCL, battery, system can include about the same volume of the first and second electrocatalysts. Alternatively, the volume of the first or second electrocatalyst can be higher than the volume of the other electrocatalyst.

[0175] Furthermore, it is contemplated that more than two types of catalysts may be present in the system. For example, different types of alloy-based catalysts may be included in the porous cavities, on the non-porous surface, or both.

[0176] The support substrate with a multi-catalyst system can be prepared by one or more methods, such as atomic layer deposition, chemical vapor deposition, sputtering, or other techniques for depositing electrocatalysts on substrates. If the electrocatalysts are applied separately, a shield or mask can be used. When the first electrocatalyst is applied to the outer surface, a shield or mask can also be applied to one or more pores. When the second electrocatalyst is applied to the pore surface, another shield or mask can be applied to the outer surface of the substrate.

[0177] To further optimize the performance of electrochemical cells and improve oxygen transport within CCLs, multi-electrolytes can be introduced into the system.

[0178] A multi-electrolyte may include more than one type of electrolyte within a CCL. A multi-electrolyte may include a first electrolyte and a second electrolyte that may differ in chemical composition, internal structure, function, physical properties, chemical properties, placement within the system, or a combination thereof.

[0179] For example, the first electrolyte can be an electrolyte structured to have good proton transport or proton conductivity, but is less effective than the second electrolyte in preventing electrocatalyst degradation, has lower oxygen conductivity, or both. A non-limiting example of the first electrolyte can be Nafion TM Etc. The first electrolyte may be located outside the porous portion of the substrate support, in direct contact with an outer non-porous surface region of the substrate support, and / or closely attached to a non-porous surface region of the substrate support.

[0180] The second electrolyte can be structured to prevent electrocatalyst degradation, secondary metal leaching of the PtM alloy, transport, or a combination thereof. The second electrolyte can be structured to have a lower proton transport capability or proton conductivity, a higher oxygen transport capability or oxygen conductivity, or both than the first electrolyte. The second electrolyte may be located in at least some or all of the pore cavities within the porous structure of the substrate support. The second electrolyte can be an ionic liquid, HOPI, etc. The second electrolyte may have a greater carrier substrate affinity or adhesion than the first electrolyte. Therefore, the second electrolyte can be structured to remain located in the pores of the porous region during the entire service life of the battery by adhesion, capillary forces, or a combination thereof.

[0181] The first and second electrolytes may be miscible. The first and second electrolytes may include a mixture of the first and second electrolytes, wherein the ratio of the first electrolyte to the second electrolyte or the second electrolyte to the first electrolyte is about 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 2:3, 4:5, etc. The mixture or blend may be present in at least some portion of the CCL, such as around or directly adjacent to the pores, at the first electrolyte-second electrolyte interface, or both. The concentration of either electrolyte at the interface may gradually increase toward the main volume of the same electrolyte.

[0182] Thus, the CCL may include at least a first electrocatalyst at a first concentration c1 and a first electrocatalyst at a second concentration. The first concentration c1 is the concentration of the first electrolyte at the outer surface of the substrate support, within the CCL space without substrate pores, or both. The second concentration c2 is the concentration of the first electrolyte adjacent to the second electrolyte, the pore cavity, the pore top surface, or a combination thereof. The second concentration c2 may be lower than the first concentration c1.

[0183] The CCL may include at least a first concentration c3 of a second electrocatalyst and a second concentration c4 of a second electrocatalyst. The first concentration c3 is the concentration of the first electrolyte at the first electrolyte-second electrolyte interface, in the top portion of the pore cavity, at the outer outer edge of the pore, or a combination thereof. The second concentration c4 is the concentration of the first electrolyte within the pore, in the middle portion of the pore cavity, at the bottom portion of the pore cavity, at the wall of the cavity, or a combination thereof. The second concentration c4 may be greater than the first concentration c3.

[0184] Alternatively, to prevent mixing of electrolytes at the interface, the pores may be capped with a material. It is also contemplated that the entire support may be capped. The cap may be a layer, a coating, or both. The cap is structured to physically separate the first electrolyte from the second electrolyte. The material may be permeable to protons, O 2 and water to prevent any unnecessary transport obstruction or blockage. The material may be impermeable to the first electrolyte, the second electrolyte, or both. Non-limiting exemplary materials may include carbon-based coatings, graphene, or both.

[0185] The CCL, battery or system may contain a first electrolyte having a larger volume than the second electrolyte due to the fact that the second electrolyte may be retained in the pore cavities.

[0186] exist Fig. 22 In a non-limiting example, a portion of CCL 454 includes a first electrolyte surrounding a carrier substrate. The first electrolyte 481 may have a first proton conductivity and a first rate at which the electrocatalyst is prevented from dissolving. CCL 454 also includes a second electrolyte 483 located within the cavity of pore 496. The second electrolyte 483 may have a second proton conductivity and a second rate at which the electrocatalyst is prevented from dissolving. The first proton conductivity is greater than the second proton conductivity. The first rate at which the electrocatalyst is prevented from dissolving is less than the second rate at which the electrocatalyst is prevented from dissolving. The first and second electrolytes form a first electrolyte-second electrolyte interface 485 having one or more of the above-described characteristics.

[0187] Fig. 22 Non-limiting examples of electrocatalyst placement are also depicted. The electrocatalyst may be located on the outer surface region of the substrate support 450, in the pore cavities 496 of the porous region, or both. The pores and electrocatalyst particles may have one or more characteristics described in the specification.

[0188] exist Fig.23A In an alternative depiction of a multi-electrolyte system of FIG. 4 , a substrate support 450 is depicted as having pores 496. The pore cavities are filled with a second electrolyte 483. A first electrolyte 481 is shown surrounding the substrate support 450 and the pores 496. The first and second electrolytes form a first electrolyte-second electrolyte interface 485.

[0189] Fig.23A The first electrolyte-second electrolyte interface is shown in FIG. 4 and is labeled 485. The first concentration c1 and the second concentration c2 of the first electrolyte and the first concentration c3 and the second concentration c4 of the second electrolyte are labeled.

[0190] In an alternative embodiment, electrolyte concentration fluctuations or differences within the CCL are eliminated or minimized by introducing a cap 475 over the aperture 496. As explained above, the cap can prevent contact between the first and second electrolytes.

[0191] Fig.24 An alternative form of cover 475' is shown. Fig.24 As can be seen in FIG. 4 , the cover 475' extends across the entire area of ​​the substrate support, so that the first electrolyte 481 contacts the cover 475' instead of contacting the substrate support 450. The cover 475' can prevent the formation of a first electrolyte-second electrolyte interface. The cover or coating can be selectively applied to one or more portions of the carrier substrate and does not cover the entire area of ​​the carrier substrate, but rather covers a substantial area of ​​the porous region and the non-porous region.

[0192] In at least some embodiments, it is contemplated that only some of the total porosity of the support substrate may include the second electrolyte. The pores that include the second electrolyte will be the pores that contain the electrocatalyst particles. At least some of the pores may not contain electrocatalyst particles and may contain the first electrolyte.

[0193] It is also contemplated that more than two electrolytes may be introduced into the system. For example, some pores may be filled with a third electrolyte that has beneficial properties tailored for a particular type of electrocatalyst.

[0194] Disclosed herein is a method of forming a multi-electrolyte system. The method may include first filling a pore cavity with the second electrolyte described above. The method may include completely filling the pores so that the entire volume of the pores is filled with electrolyte. Subsequently, a first electrolyte may be applied to the non-porous surface area and above the filled pores to form a first electrolyte-second electrolyte interface.

[0195] The method may include selectively applying a second electrolyte to a first portion of the pores of the support substrate. The method may also include leaving some of the pores free of the second electrolyte. The method may include applying the second electrolyte to the pores containing the electrocatalyst particles. The method may include using a mask to cover the pores and / or areas that remain free of the second electrolyte.

[0196] Alternatively, a cap or coating as described herein may be selectively applied to the pores and / or non-porous regions containing the second electrolyte prior to applying the first electrolyte into the volume of the CCL. Alternatively still, the method may include applying a cap or coating over a portion or the entire surface area of ​​a carrier substrate including porous and non-porous regions.

[0197] The following applications are related to this application: U.S. patent application serial number __________________ (RBPA 0389, 0399, 0403 and 0404PUS), filed on June 16, 2022, the entire contents of which are incorporated herein by reference.

[0198] 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 words rather than restrictions, 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 preferred in terms of one or more desired characteristics relative to other embodiments or prior art implementations, 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, which depends 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, maintainability, weight, manufacturability, ease of assembly, etc. Therefore, in terms of one or more characteristics, to the extent that any embodiment is described as less desirable than other embodiments or prior art embodiments, these embodiments are not outside the scope of the present disclosure and may be desirable for specific applications.

Claims

1. An electrochemical cell comprising: anode; cathode; as well as a membrane that physically separates the anode from the cathode, The cathode has a cathode catalyst layer including an ionomer and an electrocatalyst support substrate forming an ionomer-support interface having covalent bonds formed between the substrate and the ionomer via a grafting compound, the substrate also having a plurality of capped hydrophilic groups. 2 . The battery according to claim 1 , wherein the grafted compound is an aromatic compound, and wherein the covalent bond is between the hydrophilic group of the substrate and the aromatic group of the aromatic compound. The battery of claim 1 , wherein the covalent bond is a substrate-acetyl bond. 4 . The battery of claim 1 , the interface further comprising covalent bonds between reactive groups of the grafted compound and carbon atoms of the ionomer adjacent to hydrophilic groups of the ionomer. The battery according to claim 1 , wherein the grafted compound is an iodonium-based compound. The battery of claim 1 , wherein the covalent bond comprises an oxygen atom of an epoxy group. The battery of claim 1 , wherein the substrate comprises a carbon-based material.

8. The battery of claim 1, wherein the grafted compound comprises a phenyliodonium group.

9. A cathode catalyst layer ionomer-support interface comprising: Ionomers with hydrophilic side chains and a hydrophobic backbone; as well as Electrocatalyst support substrate, The ionomer is covalently bonded to the support substrate via a grafting compound such that at least some of the hydrophilic side chains are oriented toward the support substrate and the hydrophobic backbone chains are oriented away from the support substrate.

10. The interface of claim 9, wherein the grafting compound comprises epoxy groups.

11. The interface of claim 9, wherein the covalent bond is a substrate-acetyl bond.

12. The interface of claim 9, wherein the grafted compound is an aromatic compound, and wherein the covalent bonds include hydrophilic groups of the substrate and aromatic groups of the aromatic compound.

13. The interface of claim 9, wherein the grafting compound is grafted onto ionomer chains adjacent to the hydrophobic backbone.

14. The interface of claim 9, wherein the grafted compound is a diazonium or iodonium compound.

15. A method of forming an ionomer-electrocatalyst support interface, comprising: forming a functionalized ionomer by reacting the ionomer with a compound having a reactive group adjacent to a leaving group; grafting the functionalized ionomer onto the electrocatalyst support by stimulating the leaving group so that the leaving group dissociates to form a free radical on the reactive group, causing the free radical to attack a dangling bond on the electrocatalyst support and form a covalent bond between the functionalized ionomer and the support; and The remaining dangling bonds on the electrocatalyst support are passivated to cap their ends.

16. The method of claim 15, wherein the forming comprises an addition reaction of a benzenediazonium or benzeneiodonium group to an ionomer.

17. The method of claim 15, wherein the grafting comprises forming a covalent bond between a hydrophilic group of the substrate and an aromatic group of the grafting compound.

18. The method of claim 15, further comprising activating the grafting reaction by a voltage change.

19. The method of claim 15, wherein the leaving group comprises N + or I - .

20. The method of claim 15, wherein the passivating comprises electrochemically activating by applying a voltage to the support.

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