Electrochemical cell catalyst layers

Abstract

An electrochemical cell comprises an anode, a cathode and a membrane that physically separates the anode from the cathode, wherein the cathode has a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate, forming an ionomer-support interface with a covalent bond between the substrate and the ionomer via a graft connection, wherein the substrate further comprises a plurality of terminated hydrophilic groups.

Description

Technical field

[0001] The present disclosure relates to materials and structures of catalyst layers in chemical and electrochemical cells, as well as to methods for their use and manufacture. background

[0002] Given the ever-increasing global interest in environmentally friendly technologies, electrochemical cells such as fuel cells and electrolyzers are leading candidates for various applications. However, many challenges must be overcome before electrochemical cells can be widely adopted. These challenges include material corrosion and degradation, catalyst costs and dissolution, and factors affecting cell effectiveness and efficiency, such as oxygen transport within the cell layers. Summary

[0003] In one or more embodiments, an electrochemical cell is disclosed. The cell can comprise an anode, a cathode, and a membrane that physically separates the anode from the cathode. The cathode can have a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate, forming an ionomer-support interface with a covalent bond between the substrate and the ionomer via a graft connection. The substrate can further comprise a plurality of terminated hydrophilic groups. The graft connection can be an aromatic compound. The covalent bond can be between a hydrophilic group of the substrate and an aryl group of the aromatic compound. The covalent bond can be a substrate-acetyl bond.The interface can also include a covalent bond between a reactive group of the graft compound and an ionomer carbon atom adjacent to a hydrophilic group of the ionomer. The graft compound can be benzoliodonium-based. The covalent bond can include oxygen atoms of an epoxy group. The substrate can be a carbon-based material. The graft compound can contain a benzoliodonium group.

[0004] In another embodiment, a cathode catalyst layer-ionomer-support interface is disclosed. The interface can comprise an ionomer with hydrophilic side chains and a hydrophobic backbone. The interface can also comprise an electrocatalyst support substrate. The ionomer can be covalently bonded to the support substrate via a graft connection such that at least some of the hydrophilic side chains are oriented towards the support substrate and the hydrophobic backbone is not oriented towards the support substrate. The graft connection can contain an epoxy group. The covalent bond can be a substrate-acetyl bond. The graft connection can be an aromatic compound, and the covalent bond can be located between a hydrophilic group of the substrate and an aryl group of the aromatic compound.The aromatic compound can be grafted onto the ionomer chain adjacent to the hydrophobic backbone. The aromatic compound can be based on diazonium or on lodonium.

[0005] In yet another embodiment, a method for forming an ionomer-electrocatalyst support interface is disclosed. The method can include forming a functionalized ionomer by reacting an ionomer with a compound having a reactive group adjacent to a leaving group. The method can also include grafting the functionalized ionomer onto an electrocatalyst support by stimulating the leaving group, causing the leaving group to detach from the reactive group, forming a radical. This radical then attacks a dangling bond on the electrocatalyst support and forms a covalent bond between the functionalized ionomer and the support. The method can further include passivating any remaining dangling bonds on the electrocatalyst support to terminate their ends.The formation can involve an addition reaction of a benzenediazonium or benzoliodonium group to the ionomer. The grafting can involve the formation of the covalent bond between a hydrophilic group of the substrate and an aryl group of the graft compound. The procedure can also involve activating the grafting reaction by a strain change. The leaving group can be N. + or I - Passivation can include electrochemical activation by applying a voltage to the substrate. Brief description of the drawings The Fig. Figure 1A shows a non-restrictive example of a fuel cell and its components in an exploded view; The Fig. Figure 1B shows a schematic representation of a membrane electrode assembly (MEA) and its operating principle; The Fig. Figure 2A shows a schematic view of a non-restrictive example of an electrolyzer stack; The Fig. Figure 2B is a schematic representation of the electrolysis principle; The Fig. Figure 3 shows a schematic view of a cathode catalyst layer (CCL) with different types of transport and water-ionomer interactions within the layer; The Fig. Figure 4 shows a conventional covering of the carbon substrate with ionomer, resulting in an exposed carbon surface and hydrophilic ionomer outer layers; The Fig. Figure 5 shows a non-restrictive embodiment of a CCL disclosed herein; The Fig. Figure 6 shows a schematic representation of a substrate-ionomer interface according to one or more embodiments; The Fig. Figure 7A shows a molecular dynamics (MD) simulation between a carbon substrate and hydrophilic groups of an ionomer; The Fig. Figure 7B shows an MD simulation between a carbon substrate and hydrophobic groups of an ionomer; The Fig. Figure 8 shows a non-restrictive example of a CCL with a lamellar structure and a hydrophobic outer layer; The Fig. Figure 9 shows an alternative substrate-ionomer interface according to one or more embodiments; The Fig. Figure 10 is a scheme of a functionalized ionomer with a compound that has a reactive and a cleaving group; The Fig. Figure 11 shows the steps of a non-restrictive example reaction mechanism involving a diazonium-functionalized ionomer according to one or more embodiments disclosed herein; In the Fig. 12A-C show different configurations of the reactive group within ionomer chains; The Fig. Figures 13A - 13G show the carbon-ionomer interface with covalent bonding, which is made possible by various chemical pathways disclosed herein; The Fig. Figure 14 shows a state-of-the-art substrate with a smooth surface profile; The Fig. Figure 15 is a schematic representation of a boundary layer adjacent to the first surface morphology of the substrate; The Fig. Figure 16 shows an unlimited example of the first surface morphology profile; The Fig. Figure 17 shows a perspective side view of a non-restrictive example of the mountainous first surface morphology; The Fig. Figures 18A - 18C show a top view of non-restrictive examples of the first surface morphology, which resembles a tire thread; The Fig. Figure 19A shows a schematic representation of a non-restrictive example of a support substrate with the first surface morphology and the second surface morphology disclosed herein; The Fig. Figure 19B shows a schematic representation of a non-restrictive example of a support substrate with the first surface morphology with adhering electrocatalyst particles and the second surface morphology disclosed herein; The Fig. Figure 20 shows a schematic top view of a non-restrictive example of a support substrate with a multi-electrocatalyst system according to one or more embodiments disclosed herein; The Fig. Figure 21A shows a schematic view of a support substrate with a non-porous and porous surface and a non-restrictive example of a multi-electrocatalyst system; The Fig. Figure 21B shows another non-restrictive example of the multi-electrocatalyst system on the support substrate; The Fig. Figure 22 shows a non-restrictive example of a CCL with a multi-electrolyte system according to one or more embodiments disclosed herein; The Fig. Figure 23A shows a non-restrictive example of a multi-electrolyte system and its interface; The Fig. Figure 23 shows a non-restrictive example of a multi-electrolyte system with a cap; and The Fig. Figure 24 shows a top view of a CCL with a multi-electrolyte system with a cap. Detailed description

[0006] Embodiments of the present disclosure are described herein. However, it is understood that the disclosed embodiments are merely examples and that other embodiments may take different and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or reduced in size to show details of certain components. Therefore, specific structural and functional details disclosed herein are not to be understood as limiting, but merely as a representative basis to show a person skilled in the art how the present embodiments may be used in different ways.As experts know, various features illustrated and described with reference to one of the figures can be combined with features illustrated in one or more other figures to create embodiments not expressly illustrated or described. The combinations of the illustrated features represent embodiments for typical applications. However, various combinations and modifications of the features, consistent with the teachings of this disclosure, may be desirable for specific applications or implementations.

[0007] Except as in the examples or where expressly stated otherwise, all numerical values ​​in this description indicating quantities of material or reaction and / or conditions of use are to be understood as being modified by the word "approximately" when describing the widest possible scope of application of the invention. Use within the specified numerical limits is generally preferred.Furthermore, unless expressly stated otherwise: percentages, “parts of” and ratios refer to weight; the description of a group or class of substances as suitable or preferred for a particular purpose in connection with the invention implies that mixtures of two or more members of the group or class are equally suitable or preferred; the chemical description of constituents refers to the constituents at the time of addition to a combination specified in the description and does not necessarily exclude chemical interactions between the constituents of a mixture once mixed.

[0008] The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation mentioned herein and applies mutatis mutandis to normal grammatical variations of the originally defined abbreviation. Unless explicitly stated otherwise, the measurement of a property is determined by the same technique to which reference was made before or after for that same property.

[0009] It should also be noted that, as used in the description and the attached claims, the singular forms "ein", "einer / eines", and "die" include plural references unless the context clearly indicates otherwise. For example, when a component is mentioned in the singular, it is intended to refer to a plurality of components.

[0010] The terms “essentially”, “generally”, or “approximately” used here mean that the quantity or value in question may be the specified specific value or another value close to it. Generally, the term “approximately”, when denoting a specific value, is intended to indicate a range within ±5% of that value. For example, the expression “approximately 100” denotes a range of 100 ±5, i.e., the range from 95 to 105. Generally, when using the term “approximately”, it can be assumed that similar results or effects in accordance with the invention can be achieved within a range of ±5% of the specified value. The term “essentially” may modify a value or relative feature disclosed or claimed in the present disclosure.In such cases, “essentially” can mean that the value or relative property it modifies is within ± 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the value or relative property.

[0011] It should also be noted that integer ranges explicitly include all integers in between. For example, the integer range 1–10 explicitly includes 1, 2, 3, 4, 5, 6, 7, 8, 9, and 10. Similarly, the range 1–100 includes the numbers 1, 2, 3, 4, ... 97, 98, 99, 100. Likewise, when specifying any range, intermediate numbers that are increments of the difference between the upper and lower bounds divided by 10 may be used as alternative upper or lower bounds. For example, if the range is 1.1 to 2.1, the following numbers may be chosen as either the lower or upper bounds: 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.0. Whenever a list of integers is given here, it should also be noted that the list of integers explicitly includes ranges of any two integers within the list.

[0012] In the examples presented here, concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be adjusted to plus or minus 50 percent of the stated values, rounded up or truncated to two significant figures. As a refinement, the concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be adjusted to plus or minus 30 percent of the stated values, rounded up or truncated to two significant figures. As a further refinement, the concentrations, temperature, and reaction conditions (e.g., pressure, pH, flow rates, etc.) can be adjusted to plus or minus 10 percent of the stated values, rounded up or truncated to two significant figures.

[0013] For all compounds expressed as empirical chemical formulas with multiple letters and numerical subscripts (e.g., CH₂O), the values ​​of the subscripts may be plus or minus 50 percent of the stated values, rounded or truncated to two significant figures. For example, CH₂O signifies a compound of the formula C(0.8-1.2)H(1.6-2.4)O(0.8-1.2). With further refinement, the values ​​of the subscripts may be plus or minus 30 percent of the stated values, rounded or truncated to two significant figures. With a further refinement, the values ​​of the subscripts may be plus or minus 20 percent of the stated values, rounded or truncated to two significant figures. The terms "compound" and "composition" are used interchangeably.

[0014] As used here, the term "and / or" means that either all or only one of the elements 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, i.e., "only A, but not B."

[0015] It should also be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may naturally vary. Furthermore, the terminology used herein is employed solely for the purpose of describing certain embodiments of the present invention and is not intended to be restrictive in any way.

[0016] The term "comprehensive" is synonymous with "including," "with," "containing," or "characterized by." These terms are broad and open and do not exclude additional, unlisted elements or procedural steps.

[0017] The phrase "consisting of" excludes any element, step, or component not specified in the claim. If this phrase appears in a clause of the main part of a claim, rather than immediately after the preamble, it limits only the element specified in that clause; other elements are not excluded from the claim as a whole.

[0018] The wording “essentially consisting of” limits the scope of a claim to the specified materials or steps and to those that do not substantially affect the fundamental and novel feature(s) of the claimed subject matter.

[0019] With regard to the terms “comprehensive”, “consisting of” and “essentially consisting of”, the following applies: If one of these three terms is used herein, the subject matter currently disclosed and claimed may include the use of one of the other two terms.

[0020] 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 "several" as a subset.

[0021] The description of a group or class of materials as suitable for a particular purpose in conjunction with one or more embodiments implies that mixtures of any two or more members of the group or class are suitable. The chemical description of the constituents refers to the constituents at the time of their addition to a combination specified in the description and does not necessarily exclude chemical interactions between the constituents of the mixture after mixing. The initial definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the originally defined abbreviation. Unless expressly stated otherwise, the measurement of a property is determined by the same technique to which reference was made previously or subsequently made for the same property.

[0022] Chemical and electrochemical systems that utilize hydrogen as a fuel source are considered the energy systems of the future, either in direct hydrogen combustion engines or in fuel cells. These hydrogen-producing devices are becoming increasingly popular due to their ability to generate clean energy. The systems can include fuel cells, electrolysis cells or electrolyzers, and battery cells. Fuel cells, or electrochemical cells, which convert the chemical energy of a fuel (e.g., H₂) and an oxidant into electricity through two electrochemical half-reactions (redox reactions), have become an increasingly popular technology for producing hydrogen as a fuel. Fuel cells are now a promising alternative transportation technology that operates without emissions of toxins or greenhouse gases.

[0023] A non-restrictive example of a fuel cell, a proton exchange membrane fuel cell (PEMFC), is found in the Fig. Figure 1A shows a key component of the PEMFC 10 that contributes to generating the electrochemical reaction required for electron separation. The membrane electrode assembly (MEA) 12 comprises subcomponents such as catalyst-coated cathodes 22 and anodes 24, separated by a proton-conducting ionomer or an ionomer membrane 26. The catalyst is shown in the schematic representation of the MEA in Figure 1A. Fig. 1B is designated as 28. In addition to the MEA 12, the PEMFC 10 typically includes other components such as current collectors 14, gas diffusion layer(s) 16, seals 18 and (one) bipolar plate(s) 20.

[0024] The anode carries out the hydrogen oxidation reaction (1), while the cathode carries out the oxygen reduction reaction (2): (H2 → 2H + + 2e-s 1) 4H + + O2 + 4e - → H2O (2)

[0025] Generally, H₂ is split at the surface of the electrocatalyst in the anode to form protons and electrons in a hydrogen oxidation reaction (HOR). The electrons are transported through the support of the anode catalyst layer into the external circuit, while the protons are drawn through the proton exchange membrane (PEM) into the cathode catalyst layer. Once in the catalyst layer, the protons move through the ion-conducting polymer or ionomer thin-film network to the surface of the electrocatalyst, where they combine with the electrons from the external circuit and the O₂ that has diffused through the pores of the cathode catalyst layer (CCL) to form water in the oxygen reduction reaction (ORR).

[0026] Besides fuel cells, electrolyzers represent another type of electrochemical cell. Electrolyzers use electrical energy to carry out chemical reactions. In an electrolysis process, electrolyzers split water into hydrogen and oxygen, which is a promising method for producing hydrogen from renewable resources. Like a fuel cell, an electrolyzer contains an anode and a cathode catalyst layer separated by an electrolyte membrane. The electrolyte membrane can consist of a polymer, an alkaline solution, or a solid ceramic material. A catalyst material is incorporated into the anode and cathode catalyst layers of the electrolyzer.

[0027] In addition to fuel cells, the electrolyzer can also be used in other applications, including industrial, private and military applications and technologies that focus on energy storage, such as stabilizing the power grid from dynamic power sources, including wind turbines, solar cells or local hydrogen production.

[0028] A typical single electrolyzer consists of an electrolyte membrane, an anode layer, and a cathode layer, which is separated from the anode layer by the electrolyte membrane. A non-restrictive schematic representation of an electrolyzer stack 40 is shown in the Fig. Figure 2A shows the electrolyzer stack 40, which comprises individual electrolyzer cells 31, each of which includes the membrane 32, electrodes 34, 36, and bipolar plates 44. A catalyst material, e.g., Pt-based catalysts, is contained in the anode and cathode layers 34, 36 of the electrolyzer stack 40. In the anode layers 34, H₂O is converted to O₂ and H₂. + hydrolyzed (2H2O → O2 + 4H + + 4e - ). At the cathode layers 36, H combines + with electrons to form H2 (4H + + 4e - → 2H2).

[0029] A representation of the electrolysis principle used by a proton exchange membrane (PEM) electrolyzer 30, with the corresponding reactions, is shown in the Fig. Figure 2B shows the electrolyzer 30 comprising the PEM 32, the anode 34, and the cathode 36. Each electrode contains a porous transport layer (PTL) and a catalyst layer. During electrolysis, water is split into oxygen and hydrogen in anodic and cathodic, electrically driven evolution reactions. The liquid water reactant (H₂O) passes through the anode PTL to the anode catalyst layer, where the oxygen evolution reaction (OER) takes place. The protons (H₂O) + The electrons (e-) migrate through the PEM 32, and during the hydrogen evolution reaction (HER) at the cathode catalyst layer 36, they are conducted through an external circuit. The anodic OER requires a much higher overpotential than the cathodic HER. It is the anodic OER that determines the efficiency of water splitting due to the sluggish nature of the four-electron transfer.

[0030] In general, a high ORR and OER rate is desirable. To achieve a high reaction rate at the cathode, oxygen, protons, and electrons must be transported to the catalyst particles while the generated water is transported away from the reaction zone. At low current densities, where water is predominantly present as vapor, transport is achieved by (a) electron transport through the catalyst support 50, (b) proton transport through the ionomer 52 dispersed in the cathode catalyst layer (CCL) 54, and (c) oxygen and water transport through the porous network 56 of the CCL 54, as shown in the Fig. 3 shown schematically.

[0031] At high current densities, however, the vaporization capacity of CCL 54 is exceeded by the water formation rate. The transport regime switches from vapor to liquid transport. A liquid pressure gradient builds up. Depending on the wettability of the pore network 56, the CCL 54 can be partially flooded with liquid water. The liquid water can then clog the secondary pores 58 in the CCL 54 and impede oxygen transport, as in the Fig. Figure 3 illustrates the blockage. The blockage is represented by wetting droplets 60. These droplets represent a water-ionomer interaction in a hydrophilic system, where the droplets wet the ionomer surface and become trapped within the pore network, i.e., they do not move. This blocks transport through the secondary pores and leads to flooding if further water droplets accumulate in the network 56. The hindered oxygen transport, in turn, limits the reaction rate of the cathode and thus the overall performance of the electrochemical cell.

[0032] Furthermore, a typical ionomer or ion-conducting polymer contains a hydrophobic backbone that terminates in hydrophilic side chains. Typically, the ionomer has a very complex structure, such as an inverted micelle, in which the backbone is collapsed and the hydrophilic groups point inwards, forming an interconnected water domain with relatively high water activities. The hydrophilic domains serve as pathways for proton and other transport. The hydrophobic backbone can provide structural stiffness.

[0033] In the thin films of CCL, the hydrophobic and hydrophilic groups can be randomly and arbitrarily oriented, leading to the formation of hydrophilic surfaces where such surfaces may be undesirable. In typical ionomer thin-film networks of CCL, a desired hydrophobic effect is therefore not achieved due to the following factors: (1) the ionomer does not completely coat the support, so that hydrophilic parts of the substrate are exposed, (2) the layers, especially the outermost layer of the ionomer, can freely orient and realign themselves, exposing the hydrophilic side chains and resulting in an overall hydrophilic surface that leads to flooding, or both. These principles are described in the Fig. 4 shown.

[0034] While ionomers are known to adhere relatively strongly to catalyst nanoparticles, adhesion to the support itself is typically weak, leading to areas of exposed substrate such as carbon, particularly in regions of high porosity or local curvature. This incomplete coverage is especially problematic for carbons with large surface areas and low catalyst loading, as the surface density of the catalyst is lower and the hydrophobicity of the potentially exposed carbon support is insufficient.

[0035] As in the Fig. As can be seen in Figure 4, the substrate / catalyst matrix 50 / 51 is only partially surrounded by the ionomer. A portion 57 of the support substrate 50 is exposed. The ionomer 56, if present, is shown with the hydrophilic backbone 59 and the hydrophilic side chains 61. Due to the described conditions, the CCL has a relatively large portion with a hydrophilic outer surface, which can attract and accumulate water, leading to undesired oxygen transport. The area susceptible to flooding is shown in the Fig. 4 labeled with 63.

[0036] Therefore, it is necessary to enable effective oxygen transport via the CCL in order to prevent flooding of the catalyst layer, the CCL, the ionomer, the porous network within the ionomer, or a combination thereof, as far as possible.

[0037] In one or more embodiments, an electrochemical cell system is disclosed. The system can be a fuel cell or an electrolyzer. The system includes components described above with respect to fuel cells and electrolyzers. The system includes a cathode with a cathode catalytic cell layer (CCL). The CCL can contain or consist of a substrate, a catalyst, or an ionomer. The system is designed to prevent, as far as possible, flooding of the catalyst layer, the CCL, the ionomer, the porous network within the ionomer, or a combination thereof. The system is designed to allow increased oxygen transport across the CCL.

[0038] Within the scope of this disclosure, the substrate may consist of carbon. The carbon substrate may have a plurality of forms and variations, such as graphite, graphene, nitrogen-doped graphite, carbon black, electrically conductive carbon black, activated carbon fibers, fullerenes, nanotubes, nanofibers, and the like, or a combination thereof. The substrate may contain amorphous and crystalline formations. The substrate may be a porous substrate with a plurality of pores, including macropores, mesopores, and / or micropores. The substrate may thus have an outer, non-porous surface and pores of variable depth and diameter distributed within the non-porous surface. Alternatively, the support may consist of a metal oxide or metal such as cobalt oxide, aluminum oxide, titanium oxide, the like, or a combination thereof. The support material may have a variety of morphologies and desirable properties, such as…a large surface area, conductivity, low grain content, the like, or a combination thereof.

[0039] The electrocatalyst can be a noble metal catalyst such as Pt, Pd, or a combination thereof. The catalyst can contain an alloy such as a PtM alloy, where M is a transition metal such as Co, Mn, Ti, Ni, Al, Fe, Cu, Ru, Mo, etc. The catalyst can contain Ir, Ru, Ir-M, or a Ru-M alloy, where M is one of the aforementioned elements or an oxide of the aforementioned elements. In some embodiments, the catalyst can mainly consist of Ni, Cu, Co, their oxides, or a combination thereof.

[0040] The ionomer can contain one or more materials. Non-restrictive examples of the ionomer include Nafion™ or sulfonated tetrafluoroethylene-based fluoropolymer copolymer, a high oxygen permeability (HOPI) ionomer, non-fluorinated arene-based polymers such as poly(arylene sulfone), or a combination thereof. A non-restrictive example of the hydrophobic backbone can be polytetrafluoroethylene (PTFE), and the hydrophilic, polar side chains can contain sulfonates.

[0041] The CCL can be partially, substantially, or completely free of flooding, wetting droplets, water blockages, or a combination thereof. Partially can mean that at least approximately, or more than approximately, 50, 60, 70, 80, 90, or 95% of the CCL area, the porous network surface, is free of unwanted flooding, wetting droplets, water blockages, or a combination thereof.

[0042] A non-restrictive example of the CCL disclosed here is in Fig. 5 shown. The CCL 154 can comprise an ionomer 152 and a porous network 156 within the ionomer 152, as shown in Fig. Figure 5 shows that the porous network 156 can contain one or more channels or pores 162 for the transport of O2 and water. The channels or pores 162 can be interconnected. The channels or pores 162 can be regular or irregular, and have irregular, regular, or variable dimensions such as length, width, or both along their entire length. The channels or pores 162 can comprise macropores, mesopores, micropores, or a combination thereof.

[0043] In one or more embodiments, CCL 154 can comprise a number of layers. A first layer can be the substrate 150 and / or the substrate / catalyst matrix 150. The second layer can be the ionomer 152. The second layer can form a thin film, a lamellar structure, or both. The ionomer layer 152 can adhere tightly and / or uniformly to the substrate 150. The film can be uniform and have uniform dimensions, e.g., thickness. The film can maintain the uniform dimensions even if the surface has curvatures, irregularities, protrusions, depressions, or the like. The film can adhere tightly to any surface structure of the substrate or the substrate / catalyst matrix. The adhesion of the film to the substrate or the substrate / catalyst interface is uniform, complete, total, or a combination thereof.The ionomer coating 152 can be uniform, uninterrupted, and in direct contact with the substrate 150 over at least part or all of the contact area between the substrate and the ionomer. The ionomer enables proton transport to and within the CCL.

[0044] The ionomer-substrate interface 166 can be free of gaps and interruptions, so that the substrate is essentially completely covered by the ionomer. The interface is also free of exposed hydrophilic carbon groups that could potentially lead to undesirable water accumulation and subsequent flooding of the ionomer. The interface can be free of any exposed substrate or substrate / catalyst matrix, including areas of high porosity, curvature, uneven surface, or a combination thereof.

[0045] The interface 166 and the substrate 150 or the substrate / catalyst matrix 150 / 151 can have one or more surface oxygen or hydroxide terminations or termination groups 170, as shown in the Fig. 6 shown schematically. The surface can therefore have a partially oxidized surface. As in the Fig. As can be seen in Figure 6, the terminations 170 strongly bind water, which in turn binds the hydrophilic groups 161 of the ionomer 152. Covalent bonds are shown with solid lines, while dashed lines denote hydrogen bonds. Thus, covalent bonds can exist between the substrate and the end or termination groups 170, and hydrogen bonds can exist between the end groups 170, the interfacial water, and the hydrophilic groups 161. The end groups 170 can be located at substrate edges. The bonding mechanism can occur via a hydrogen bonding network mediated by interfacial water strongly bound to the partially oxidized surface and the hydrophilic side groups of the ionomer, as shown in Figure 6. Fig. Figure 7 shows that the substrate can thus have a surface chemistry structured such that the ionomer is bound to the substrate along most or substantially the entire area of ​​the substrate-ionomer interface.

[0046] The Fig. Figure 7A shows an ab initio molecular dynamics (MD) simulation used to evaluate the strength of adsorption of dilute, dispersed Nafion™ on partially oxidized non-graphitic carbon. The net attractive interaction between the structure in the Fig. 7A (showing the sulfonate- and OH-terminated non-graphitic carbon) in relation to the structure of the Fig. 7B (which shows a non-interacting interface between the OH-terminated carbon and PTFE) has a coefficient of -0.3 eV / SO3 (-29 kJ / mol). Fig. 7A and Fig. Figure 7B illustrates the advantageous sulfonate-carbon bond or the bond between hydrophilic group and substrate as opposed to the bond between hydrophobic group and substrate.

[0047] In a non-restrictive example, the substrate can contain carbon, and the end groups can be located at non-graphitic carbon edge sites. Thus, the substrate can contain ionomers adsorbed onto partially oxidized, non-graphitic carbon.

[0048] The substrate can be functionalized. Functionalization can lead to an increase in the hydrophilicity of the support, e.g., the carbon support. The increased hydrophilicity can lead to an attraction of interfacial water, which facilitates the binding of the substrate to the hydrophilic ionomer groups. The degree of functionalization should be chosen so that the corrosion of the substrate is not increased and electrical transport is not restricted. The functionalization can be such that the water contact angle can be less than approximately 90, 89, 88, 87, 86, 85, 84, 83, 82, 81, 80, 79, 78, 77, 76, or 75°.

[0049] Additionally or alternatively, the CCL, the porous network, the channels, and the pores can have hydrophobic surfaces. At least some of the surfaces can be hydrophobic. The surfaces can be permanently hydrophobic. The hydrophobicity can be permanent, stable, unchanging, durable, resilient, consistent, constant, continuous, or a combination thereof. The CCL, the porous network, or both can have a permanently hydrophobic surface throughout. The hydrophobic surfaces ensure that water droplets forming within the network do not adhere to the porous network. The hydrophobic surface helps prevent excess water from accumulating in the network as wetting droplets. Instead, the water can accumulate in non-wetting droplets that do not block oxygen transport within the porous network of the ionomer.A non-restrictive example of a non-wetting droplet is in the . Fig. Figure 5 shows that the hydrophobic surface minimizes or eliminates unwanted flooding, contributing to more effective and efficient oxygen transport through the CCL.

[0050] The ionomer described here can provide hydrophobicity through its backbone, orientation, placement, and / or fixation within the CCL. The hydrophobic backbone influences chemical stability and is water-repellent. The ionomer can be oriented and fixed within the CCL such that the hydrophobic backbone forms the outermost layer of the thin film, network, CCL, or a combination thereof. In other words, the ionomer backbone and the hydrophilic groups, which are structured to transport protons to the active catalyst sites, are not arbitrarily oriented through the CCL. Instead, the orientation of the hydrophobic backbone, the 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.

[0051] The ionomer film can have a biphasic lamellar structure. The biphasic lamellar structure can be annealed, cross-linked, or both. The ionomer can have a lamellar structure with alternating layers of the hydrophobic backbone and hydrophilic side chains, as in the Fig. Figure 8 is shown schematically. The outermost layer 172 of the lamellar structure or thin film contains the hydrophobic backbone 159. The outermost hydrophobic layer 172 is fixed in such a way that the ionomer does not reorient itself and the hydrophilic groups 161 do not change their position relative to the hydrophobic backbone 159.

[0052] In the Fig. Figure 8 shows two lamellae of the hydrophobic backbone and two lamellae of the hydrophilic groups, but a different number of lamellae is conceivable. For example, one, two, three, four, five, six, seven, eight, nine, ten or more alternating lamellae are conceivable, as long as the outermost layer 172 is hydrophobic.

[0053] While the ionomer surface may be hydrophobic under dry equilibrium conditions, prolonged exposure to moisture can cause it to become hydrophilic. This occurs as the polymer chains rearrange, exposing hydrophilic, polar side chains to surface moisture. To prevent this transformation and maintain the hydrophobic structure, the ionomer surface can be crosslinked. To prevent or reduce the reorientation of the ionomer chains and thus preserve the hydrophobic surface structure, a crosslinkable additive can be incorporated into the ionomer, forming a pervasive network structure.

[0054] A method for increasing the hydrophobicity of CCLs is disclosed herein. The method may comprise one or more steps or stages. The steps or stages may be used individually or in combination to achieve the desired structure of the CCL, the ionomer, or the ionomer-substrate interface, as described above.

[0055] The process can involve the preparation of a CCL by ink dispersion. The process can involve mixing a powder of the carbon support and catalyst with the ionomer in a water-solvent dispersion. Subsequently, the process can include coating with a blade, drying, or both. The process is independent of, and does not negatively affect, the catalyst content or substrate loading.

[0056] The first step may involve making the substrate or the substrate-catalyst matrix-ionomer interface adhesive. The process may include improving the bond between an ionomer and the substrate. The process may involve covering at least approximately 50, 60, 70, 80, 90, 95, 99, or 100% of the substrate surface with the ionomer, ensuring uniform, complete, and full adhesion to the substrate. The process may involve removing all exposed hydrophilic parts of the substrate. This removal may involve covering them with the ionomer, with end groups, with hydrophilic groups, with hydrophilic parts of the ionomer, or with a combination thereof.

[0057] The process can involve functionalizing or introducing a functionalization into the substrate. The process can involve introducing one or more terminal groups onto the surface. The terminal groups can be oxygen, hydrogen oxide, or both. The process can involve introducing the terminal groups at substrate edge sites (for example, in non-graphitic regions of a carbon substrate). The process can involve initiating a bonding mechanism between the substrate and the hydrophilic groups of the ionomer. The process can involve covalent bonding of the substrate to the terminal groups. The process can involve binding the terminal groups to the interfacial water via hydrogen bonds. The process can involve binding the interfacial water to the hydrophilic groups of the ionomer via hydrogen bonds.The process can involve the introduction of a bonding mechanism via a hydrogen bonding network mediated by interfacial water strongly bound to the partially oxidized surface and hydrophilic side groups of the ionomer.

[0058] The first step can be performed before an ionomer is incorporated into the substrate-catalyst mixture [by] blade coating, drying, or both. The first step can be performed by one or more of the following measures. The first step can include substrate functionalization by washing the substrate powder in a strong base or an oxidizing agent. A non-restrictive example of a base could be an aqueous NaOH or KOH solution. A non-restrictive example of an oxidizing agent could be a mild acid under oxidizing conditions. The first step can include substrate functionalization by exposing the carbon support to ozone and / or UV light for approximately 5–15 minutes. The first step can include substrate functionalization by exposing the support to an O₂ plasma for approximately 5–15 minutes prior to the ionomer dispersion step.O2 plasma works by functionalizing oxygen and hydroxide on the carbon substrate. The process can include adjusting the degree of functionalization to the water contact angle described above using a standard water contact angle measurement. Excessive functionalization can undesirably increase carbon corrosion or decrease electrical conductivity.

[0059] In the second step, the process can involve rendering the CCL hydrophobic or permanently hydrophobic. The process can include generating a permanently hydrophobic surface across the entire CCL pore network. The process can include promoting the realignment 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 process can involve realigning the side chains and backbone of the ionomer as described here. The process can include annealing to achieve realignment of the ionomer components. The process can involve causing the ionomer to assemble into a structure that maximizes the surface area of ​​the hydrophobic backbone.

[0060] The second step can involve coating the substrate or the substrate / catalyst matrix with ionomer. During coating, alternating layers of side chains and backbone can be formed. The process can include annealing to create the outermost hydrophobic layer by pulling the backbone outwards, away from the substrate, and aligning the side chains inwards, towards the substrate, within the thin ionomer film.

[0061] Tempering can be carried out in a nonpolar solvent vapor such as hexane, benzene, toluene, chloroform, or similar solvents, or in a mixed solvent vapor with a high partial pressure of the nonpolar solvent vapor and a low partial pressure of the polar solvent such as water. The process may involve repelling the hydrophilic side chains through their interaction with the nonpolar solvent. The process may include setting, maintaining, sustaining, or introducing a relatively low humidity level to prevent complete dehydration of the ionomer during the tempering process. The process may also include temperature control to prevent condensation of the solvent vapor and excessive dehydration of the ionomer, while maintaining sufficient mobility of the hydrophobic backbone to allow surface restructuring.

[0062] The process can include a third crosslinking step. This crosslinking can be surface-specific, to fix the outer backbone of the ionomer and thus prevent subsequent restructuring of the ionomer structure and maintain the hydrophobicity of the outermost layer of the CCL, or a combination thereof.

[0063] Crosslinking can be facilitated by inducing a bond between the hydrophilic side chains of the ionomer or the hydrophobic backbone. The process can include curing the processed film by UV radiation. The irradiation dose and duration can be optimized so that crosslinking remains confined to the surface of the ionomer coating. Excessive crosslinking throughout the bulk of the ionomer could adversely affect proton transport.

[0064] Alternatively, crosslinking can be achieved by adding a crosslinkable additive to the ionomer. The process can involve the creation of an interpenetrating network to restrict extensive reorganization of the ionomer film. A non-restrictive example of a crosslinkable additive is polyvinylidene fluoride (PVDF) polymers and divinylbenzene molecules, which mix well with Nafion™ and can be crosslinked by electron beams. The resulting PVDF / divinylbenzene network can reduce ionomer chain reorientation, thus maintaining the desired hydrophobic surface structure.

[0065] The process can also include stabilizing the hydrophobic surface structure by transforming the solvent vapor-tempered carbon / catalyst / ionomer structure of a perfluoroheptane (C7F₆). 16 ) / Ar plasma mixture is exposed.

[0066] Alternatively or additionally, another CCL-ionomer-support interface is disclosed. The chemical structure of the interface and the physical and / or chemical bonds of the interface can improve oxygen transport within the CCL, contribute to a homogeneous distribution of the ionomer on the substrate, and / or improve the chemical stability of the CCL. A non-restrictive example of the interface is shown in the Fig. 9 can be seen.

[0067] As the Fig. As shown in Figure 9, interface 266 comprises substrate 250 and ionomer 252, wherein ionomer 252 has at least one hydrophilic group 261 and a hydrophobic scaffold 259. A non-restrictive example of the hydrophilic group can be SO3(H). A non-restrictive example of the hydrophobic scaffold can be a hydrophobic Nafion™ or HOPI scaffold or chain segments. Interface 266 can comprise substrate 250, which is covalently bonded to ionomer 252. The interface additionally includes compound 280 with a reactive group designated R. Compound 280 facilitates, enables, mediates, and / or establishes the covalent bond between substrate 250 and ionomer 252.

[0068] The compound can bind to the support 250 via the reactive group R through one or more mechanisms described below, and to the ionomer 252 via a carbon atom adjacent to or in close proximity to the hydrophilic group, the hydrophobic group, the backbone, the side chain, the main chain, or any other point along the ionomer chain. The compound can contain one or more aromatic rings. The aromatic rings can be simple aromatic rings such as benzene rings. The compound can be a simple aromatic ring compound. The compound can consist of non-aromatic, free, or aromatic rings. The compound can be iodine-based. The compounds can be graft compounds.

[0069] The compound can be a compound or composition with a leaving group X originating from the reactive group R. After the leaving group X is detached from the compound, a covalent bond can be formed between the reactive group R and the substrate. The covalent bond can 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, a -Si-OC bond, a substrate-NH bond, a C-NH bond, or similar. The interface 266 can encompass the substrate 250 with a covalent bond to an aryl group, acetyl group, amine group, isocyanate group, epoxy group, or any other group mentioned here.

[0070] A non-restrictive example of reactive groups is therefore an aryl derived from a simple aromatic ring compound in which a hydrogen atom has been removed from the ring, alkyl, epoxide, carboxyl, anhydride, peroxide, halogen, acyl chloride, isocyanate, amide, amine or the like or a combination thereof.

[0071] Non-restrictive example compounds are diazonium, iodonium, silane, epoxide, carboxylic acid, anhydride, peroxide, halogen, acyl chloride, isocyanate, amide, the like, or combinations thereof. Non-restrictive examples of leaving groups are N + ≡N, N + , H + , O - , -OH-CR1=O, Cl - , I - or the like.

[0072] The covalent bond 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 an electrochemical cell. The covalent bonds described here thus offer an advantage over conventional substrate-ionomer interfaces, which may consist of a carbon interface without bonds.

[0073] Furthermore, an interface with hydrogen bonds between side groups on the ionomer and the substrate surface was described above. While hydrogen bonding is desirable with respect to an unbonded substrate interface, it may be advantageous to introduce a stronger bond between the substrate and the ionomer, at least in some arrangements of electrochemical cells.

[0074] A hydrogen bond is a relatively weak attraction between a hydrogen atom, which carries a partial positive charge, and a more electronegative atom or group. A hydrogen bond is weaker than a covalent bond because a covalent bond is a connection formed by the sharing of an electron pair between two atoms. The positively charged nuclei of the two atoms are electrostatically attracted to the same electrons, and the bond forms when the total energy of the bonded atoms is lower than that of two separate atoms. Because the formation of the bond lowers the total energy, a relatively high amount of energy is required to break the bond. This results in significantly higher stability of the ionomer-substrate interface compared to the stability achieved by hydrogen bonds.

[0075] The covalent bonding of the ionomer to the support substrate in CCL offers further advantages in addition to increased chemical stability. A functional ionomer directly bonded to the surface of the support substrate can also promote a more homogeneous distribution of the ionomer on the substrate. Inhomogeneous ionomer dispersion has been shown to lead to increased mass transport resistance. Poor ionomer dispersion can result in areas of exposed support substrate where proton conduction is not possible in the absence of the ionomer. Alternatively, poor dispersion can create areas with an abnormally thick ionomer layer, which increases oxygen transport resistance. Furthermore, homogeneous ionomer dispersion can increase corrosion resistance or make the material less susceptible to corrosion.

[0076] The substrate may also have one or more exposed, dangling, hydrophilic bonds and / or hydrogen-terminated edges of the support, which, as described above, may contribute to oxygen transport resistance. At least some of the dangling bonds 282 may be capped, passivated, or terminated, as shown in the Fig. Figure 9 shows that the substrate can therefore contain capped, passivated, or terminated bonds. 282 Removing the exposed or hydrophilic bonds can prevent several undesirable effects, including flooding.

[0077] Passivating exposed bonds in a substrate can offer several advantages. Exposed bonds terminated by reactive molecules can lead to undesirable side reactions during electrochemical operation. Therefore, passivating these bonds with molecules that cannot be removed during normal operation can prevent unwanted side reactions. Furthermore, passivated bonds can reduce the material's oxidation potential in the presence of oxygen. Thus, passivating unused, exposed bonds can increase the corrosion resistance and efficiency of the electrochemical system.

[0078] The electrochemical system or CCL can contain a substrate in which all or at least some of the dangling bonds are terminated. The support can thus contain closed hydrophilic bonds and covalent bonds between the substrate and the ionomer via a graft connection.

[0079] A method for forming the covalently bonded interface described above is disclosed. The method may comprise one or more steps. The method may include the functionalization of the ionomer by chemical processing to introduce the compound, the graft compound, the reactive group R, or a combination thereof. A non-limiting example of the functionalized ionomer 252 prior to bonding with the substrate 250 is shown in the Fig. Figure 10 shows the functionalized ionomer containing compound 280 with a reactive group R. The reactive group R has a leaving group X.

[0080] The method can further include the removal of leaving group X from compound 280. Removal can involve electrical stimulation, heating, irradiation with UV light, addition of chemical reactants, generation, deflection of an electron, or a combination thereof. Stimulation can be achieved by an electron already present in the system or supplied to the system.

[0081] The process can involve attaching the functionalized ionomer to the substrate via a grafting procedure. The process can involve breaking the bond between the reactive group R and the leaving group X. This breakage can involve the generation of a free radical. The process can involve using the reactive group for grafting. The grafting can be anionic grafting, cationic grafting, radical polymerization with atom transfer, or polymerization by free radicals. A non-restrictive example of a process that triggers grafting can include heat treatment, photochemistry, acid processing, reduction reactions, hydrolysis, electrochemical pulses, or applied voltage. The process can also be carried out using UV radiation, but this can lead to undesired byproducts and decomposition.

[0082] The process can involve providing a voltage source, applying a voltage, or both to enable the deprotonation of the compound or a part of it, such as an acid. The voltage can, for example, be used with the carboxyl group to deprotonate the -OH group.

[0083] The process can utilize a "scissors" provided by thermal / hydrolytic treatment. The process can involve the removal or cutting away of the anhydride bond and the creation of a C-acetyl bond between the substrate and the ionomer.

[0084] The process can involve radical-terminal alkene grafting. The process can include the formation of a radical on the substrate surface. Subsequently, the process can involve the reaction of the terminal alkene ionomer with a radical generated by benzoyl peroxide or other treatment to covalently bind the ionomer to the support.

[0085] After the bond between the reactive group R and the bonding group X breaks, the leaving group X can form a separate, chemically stable compound. The reactive group R can then be in a highly reactive state, so that the functionalized ionomer can form a covalent bond, as in the Fig. Figure 9 shows how the substrate can bind. The substrate can be bound to the reactive group R via a dangling bond, which is terminated, for example, with an -OH group.

[0086] The method may involve shielding, masking, or otherwise covering any, all, or at least some electrocatalyst particles to prevent grafting onto the catalyst surface, which would result in an undesirable loss of catalytically active surface area.

[0087] A schematic representation of a non-restrictive exemplary reaction mechanism including the compound disclosed herein is set forth in the Fig. Figure 11 shows the example compound being a diazonium-functionalized ionomer. The reactive group can be a salt of a diazonium. A non-restrictive example is a benzenediazonium bonded to the ionomer, parts of which are in the Fig. 11 are designated with Z. Diazonium salts have a positively charged nitrogen atom. This corresponds to high reactivity, in which the nitrogen reacts +The leaving group is represented by two nitrogen atoms bonded to the benzene ring. As can be seen from the steps in the Fig. As can be seen in Figure 11, the functionalized ionomer initially contains the compound with a reactive group with the leaving group N. + ≡N. The N + The leaving group is attacked by a free electron, leading to its detachment and the formation of a radical at the aromatic ring of the compound. Since the free radical has made the aromatic group highly reactive, the ionomer is subsequently attracted to the substrate, with which it forms a covalent bond. The product of the reaction is N₂, which is very stable and inert and can be easily removed from the electrochemical cell after the grafting process.

[0088] The Fig. Figure 11 shows the ionomer in which the reactive group is adjacent to a hydrophilic sulfonate group on the ionomer. Other arrangements or configurations of the reactive group R within the ionomer chains are conceivable and are described in the Fig. 12A-C is shown.

[0089] Alternative grafting chemistries include silane, which forms -Si-OC bonds; the end product is in the Fig. 13A shown; epoxides forming -COC bonds, the end product is in the Fig. 13B, Fig. 13C shown; carboxyl, the end product is in the Fig. 13D and Fig. 13E shown; anhydride, the end product is in the Fig. 13F shown, or alkene, the end product is in the Fig. 13G shown, belong. Although in the Fig. Where 12A-C and 13A-G are represented as fluorinated polymers, other chemical compounds for ionomers are possible as replacements or in combination, e.g. hydrocarbons, arenes and amides.

[0090] The process may further include the passivation of dangling or exposed bonds. Small molecules structured to terminate the dangling bonds and not be removed during normal electrochemical cell operation may be used. Non-restrictive examples of passivation techniques include halide termination by immersion in a weak halide acid; aryl termination by further diazonium exposure; termination with single-atom catalysts such as Fe, Co, Ni, or Cu, radical scavengers such as Ce, or an organometallic complex thereof; carbon monoxide termination; a plasma, vacuum, ultraviolet, or annealing process; or the above methods in combination with a voltage applied to the substrate for electrochemical activation of the passivation reaction.

[0091] Furthermore, an alternative or additional catalyst support is disclosed which is modified to improve oxygen diffusion in nanopores. The modified surface leads to increased pore roughness. Without limiting the disclosure to a single theory, it is assumed that the roughened morphology of the support substrate pore surface disclosed here can provide a surface diffusion pathway for gaseous species in confined media such as the pores of an electrocatalyst support. Thus, increasing the surface roughness of the support by chemical, thermal, electrochemical, or other means can help to reduce transport barriers typically observed in high-surface-area carbon (HSAC) supports.

[0092] As in the Fig. As shown in Figure 14, a conventional CCL 54 comprises a nanoparticle / electrocatalyst 51 deposited on an electronically conductive support 50. The electrocatalyst 51 and / or the support 50 may be dispersed in an ionomer 52 surrounding the catalyst / support matrix 50 / 51. Each component of the CCL plays a distinct role. The electrocatalyst 51 can catalyze the reactions, the support 50 can provide mechanical and electrical stability to the electrocatalyst 51, and the ionomer 52 can transport the reactants and products to and from the electrocatalyst 51. As shown in Figure 14, the CCL 54 comprises a nanoparticle / electrocatalyst 51 deposited on an electronically conductive support 50. The electrocatalyst 51 and / or the support 50 may be dispersed in an ionomer 52 surrounding the catalyst / support matrix 50 / 51. Each component of the CCL plays a specific role. The electrocatalyst 51 can catalyze the reactions, the support 50 can provide mechanical and electrical stability to the electrocatalyst 51, and the ionomer 52 can transport the reactants and products to and from the electrocatalyst 51. Fig. As can be seen in Figure 14, the surface of the support is typically a smooth, corrugated surface without abrupt changes in its morphology.

[0093] One challenge with CCLs is ensuring the high mass transport required for reactions at high current densities. One attempt to address these transport levels, related to ionomers, involved substituting Nafion™ and other ionomers with HOPls. Such substitution reduces the equivalent weight, shortens the side chain length, and introduces stiffer structures into the ionomer backbone. However, the weakness of this substitution lies in the adsorption of the ionomer backbone, side chains, and / or functional groups to the catalyst surface. This adsorption can hinder activity through steric effects. In other words, adsorption creates a metaphorical traffic jam, preventing reactants from entering or leaving the electrocatalyst.Another attempt to solve the transport challenge is the use of HSACs, which are characterized by a high degree of micro- and mesoporosity. HSACs attempt to eliminate the contact between the catalyst and the ionomer. However, eliminating this contact leads to higher transport resistances.

[0094] Therefore, there is a need for a support substrate that facilitates oxygen transport to the electrocatalyst, enables high mass transport at high current densities, and at the same time provides good structural support for the electrocatalyst.

[0095] The catalyst support disclosed herein can exhibit a porosity formed by a plurality of pores. These pores can be crucial for the mass transport of products and reactants in the electrochemical cell reactions described herein. The pores can be classified into three general groups: micropores with a diameter of less than approximately 2 nm, mesopores with a diameter between approximately 2 and 50 nm, and macropores with a diameter greater than approximately 50 nm.

[0096] From the perspective of pore size distribution, the substrate can contain at least some, the majority, or predominantly pores dimensioned to accommodate electrocatalyst particles while preventing infiltration by the ionomer. The catalyst support can consist primarily of mesopores, micropores, pores with a diameter of less than approximately 10 nm, or a combination thereof. The mass or volume of the macropores in the support disclosed herein can be approximately, at least, or at most approximately 30–70, 40–60, or 50–55% of the total mass or volume of the substrate pores. The mass or volume of the mesopores and micropores in combination can be approximately, at least, or at most approximately 30–70, 40–60, or 50–55% of the total mass or volume of the substrate pores. Other particle pore distributions are conceivable.

[0097] The pore distribution can enable homogeneous dispersion of the ionomer on the substrate, facilitate electrocatalyst particle transport, prevent blockage of the electrocatalyst by the ionomer side chains, and thus optimize proton transport. The pores can be wide and shallow enough to allow efficient oxygen transport to the electrocatalyst without transport losses due to excessive tortuosity. The pore width and depth should also be dimensioned to accommodate the electrocatalyst particles within the pores.

[0098] In pores with a diameter greater than 20 nm, the diffusion of molecular oxygen within the pore is dominated by the interactions of oxygen with water. In pores with diameters of approximately 20, 15, or 10 nm or less, diffusion is influenced not only by the interactions between oxygen and water but also by the interactions of molecular oxygen with the pore walls. Surprisingly, it has been found that roughening the pore wall surfaces introduces and / or enhances these oxygen-wall interactions, causing molecular oxygen to be adsorbed onto the surface of the walls where the electrocatalyst particles are located, forming a boundary layer adjacent to or near the pore wall surfaces. This adsorption also increases the overall solubility of the trapped water, thereby increasing the overall permeability of the pores.

[0099] The principle is explained in the Fig. Figure 15 demonstrates a catalyst support 350 with a roughened surface 384. As can be seen, below a boundary line B, in the immediate vicinity of the roughened surface 384, a larger volume of molecular oxygen 386 is present than above the boundary line. The area between the roughened surface of the first surface morphology 384 and the boundary line B is the boundary layer 387. This phenomenon occurs even though the area / volume below the boundary line B is smaller than the area / volume above the boundary line B.

[0100] The support substrate can have a first surface morphology and at least one second surface morphology. The first surface morphology is a surface morphology of one or more pores, at least some of the pores, micropores, mesopores, or a combination thereof. The first surface morphology is a pore morphology. The first morphology 389 can have a roughened surface architecture, arrangement, structure, and geometry; an unlimited example of this is in the Fig. 16. The surface of the first morphology may be uneven, irregular, with variations or deviations in height, depressions, unevenness, protrusions, lumps, uneven areas, a distorted surface, or the like, or a combination thereof. As the Fig. As shown in Figure 16, the first morphology can exhibit a profile showing one or more walls 390, peaks 391, and valleys 392. The walls 390 can be steep, gradually sloping, abrupt, regular, or irregular. The walls 390 can form elevations 391 and valleys 392. The peaks 391 can form ridges, projections, elevations, clumps, or depressions. The valleys 392 can form cavities, concavities, bulges, or concave surfaces.

[0101] The elevations 391 and the valleys 392 may have the same or different dimensions, shapes, and configurations in the overall first surface morphology. For example, at least some of the peaks and valleys may differ in height, peak width at the apex, at the base, or both. At least some or all of the peaks and / or valleys may have the same dimensions or the same shape.

[0102] Peaks 391 and valleys 392 can form a pattern. The peaks can form a continuous, interconnected series of peaks in a line, as in the Fig. 17 or Fig. 18C is shown. The pattern can be regular, irregular, repeating, continuous, interrupted, or uninterrupted. The pattern may resemble a mountain range, a tire track, scattered islands, or the like. More than one pattern may be present on the same first surface morphology. A non-restrictive example of a mountain-like first surface morphology 389 is shown in the Fig. 17 is shown. A regular, tire-thread-like first surface morphology 389 is in the Fig. 18A - 18C shown. Other patterns of the first surface morphology may include an alligator skin-like morphology or a bone marrow-like morphology.

[0103] A single catalyst support can exhibit one or more patterns of roughened surface morphology. One or more supports of the same CCL or electrochemical cell can exhibit the same initial surface morphology. Alternatively, each or at least some catalyst supports can differ in their initial surface morphology.

[0104] The peaks and troughs can alternate in a regular, irregular, repeating, or patterned manner. The elevations and depressions can form waves. The waves or waviness refer to the peak-to-peak spacing, which can be regular or irregular. The pattern of peaks and troughs can form oscillations or a repeating pattern with the same, repetitive, or periodic variation. The wavelength and frequency of the repeating pattern can be uniform across the entire surface. Wavelength refers to the distance between two adjacent peaks. Frequency refers to the number of repeating peaks at a given distance. A high frequency might be approximately 0.5 or more peaks per 1 nm. A low frequency might be fewer than 0.5 peaks per 1 nm.The wavelength and frequency in one or more of the patterns described here can be the same or different across the entire substrate. The wavelength and frequency can be uniform or non-uniform. The pattern can be sinusoidal. The pattern can consist of uniform, high-frequency oscillations with short spatial wavelengths, at least some variations with longer wavelengths, or a combination thereof. The surface morphology may contain low-frequency irregularities that make the surface appear smooth overall, but are rough on a smaller scale.

[0105] The support substrate may also exhibit a secondary surface morphology, which may be free of peaks, valleys, rows of peaks, or a combination thereof. This secondary surface morphology may be relatively smooth, exhibiting a uniform and regular surface or consistency, and be free of perceptible protrusions, lumps, or depressions. The secondary surface morphology may be essentially flat, meaning it may be of the same height across the entire support area.

[0106] Surface roughness can be defined as Ra. The first surface morphology can have a higher Ra value than the second surface morphology. A non-restrictive example for the first surface morphology 389 and the second surface morphology 395 is given in the Fig. Figure 19A shows the first surface morphology 389 located in a first pore 396 of a catalyst support 350, in contrast to the second surface morphology 395, which is located outside the first pore 396 and inside a second pore 396'. The first surface morphology 389 has an Ra1 value that 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 approximately 10 nm.

[0107] The electrocatalyst particles 351 can be contained or accommodated on the first surface morphology, along, on, at, between the profile peaks, valleys, regions, and / or walls. A non-restrictive example of the placement of the electrocatalyst is shown in the Fig. Figure 16 illustrates another, non-restrictive example of the attachment or adhesion of the electrocatalyst to the second surface morphology of a pore. Fig. 19B shown. Fig. 19B A plurality of electrocatalyst particles are attached to the inner walls of pore 396. The inner walls exhibit a first surface morphology 389 with peaks 391 and valleys 392. The profile of pore 396 has a roughened surface with Ra1. The in the Fig. The specific arrangement of particles 351 within pore 396 shown in Figure 19B is only exemplary. The electrocatalyst particles can be arranged at the upper, middle, or lower end of the pores. The increased roughness allows for better adhesion of the particles to the pore walls than in a pore with lower roughness or on the non-porous surface of the substrate with the second surface morphology, designated Ra2.

[0108] The electrocatalyst particles can bind to the second surface morphology. This adhesion may be weaker than the adhesion to the first surface morphology, which exhibits greater roughness. Therefore, it may be desirable to place the electrocatalyst particles, or a large proportion of them, in the pores with the first surface morphology.

[0109] The first surface morphology can extend over the entire length of the pore. Alternatively, a portion of the pore can exhibit the first surface morphology, while at least one other portion can exhibit the second surface morphology. The pores with the first surface morphology can have a diameter of approximately 2–10, 1.8–9, or 1.5–8 nm, a depth of approximately 0.5–15, 1–12, or 2–10 nm, or a combination thereof.

[0110] A method for generating the initial surface morphology is disclosed herein. The method may comprise one or more steps. The method may include the generation of roughness. The roughness may be predetermined, specifically designed, or randomly generated. The method may include the formation of pores. Alternatively, the method may also include roughening a substrate with pores. The pore size distribution can be produced by adjusting the degree of the relevant technique by modifying the duration and energy of the process.

[0111] The process may involve the use of a shield or mask to protect one or more areas and / or pores of the substrate from roughening. As a result, the final substrate may exhibit the first surface morphology or roughness and the second surface morphology or roughness, as described above.

[0112] The process may involve the physical removal of the roughened surface from the substrate surface. Non-restrictive techniques for achieving such removal may include the use of heat, high-energy ions, or mechanical milling. Additionally or alternatively, the process may involve adding a substrate material to the existing substrate surface to increase its height, create peaks, valleys, and areas, and generally produce roughness. Non-restrictive material delivery techniques may include atomic layer deposition, chemical vapor deposition, sputtering, or surface adsorption of organic molecules such as hydrocarbons, graphene, graphite, or the like, or a combination thereof.

[0113] The process may also, or alternatively, include electrochemical roughening of the surface by pre-corrosion. The process may involve applying a high voltage to the support and / or exposing the support to an acidic environment. When one of these techniques is applied, a selection of carbons can be oxidized and detached. The process may involve exposing the support surface to reactive ions, such as reactive ion etching (RIE) or reactive vapor, to create the initial surface morphology. The vapor may contain other small molecules that react with the surface, such as hydrocarbons or molecules with aromatic rings. Some of these molecules may remain after processing to prevent corrosion.

[0114] The process can involve modifying the substrate so that it exhibits a different hierarchy of pore structures, including micropores, mesopores, and macropores. This change in the pore structure hierarchy can be achieved by modifying process conditions such as ion etching, chemical treatments, and mechanical milling, which can influence the ratio of micro- to mesoporosity.

[0115] If the support is carbon-based, additional techniques can be employed to minimize corrosion. The process may include passivation of the substrate. Passivation can involve exposing the support to a vapor or a solution of small molecules that break the dangling bonds on the surface. The small molecules can be selected to prevent corrosion. Examples of such molecules include insoluble carbon or halides. Passivation can involve thermal, plasma, vacuum, ultraviolet, or annealing processes to terminate the dangling bonds on the carbon surface. Passivation can also be electrochemically activated. This process may involve applying a voltage to induce bond formation between the dangling bonds on the carbon surface and reactive molecules in the surrounding electrolyte.Diazonium salts can be a non-restrictive example of reactive molecules.

[0116] Electrocatalysts play a crucial role in electrochemical cells, as they enable the HOR, HER, ORR, and OER reactions. Electrocatalysts are typically present in particle form. To increase their stability and prevent loss through dissolution or detachment, the electrocatalysts can be bound to a support, as described above. The most commonly used catalysts are noble metals such as platinum (Pt), palladium (Pd), or combinations thereof, as well as Pt alloys (PtM), where M is a transition metal.

[0117] The durability of electrocatalysts in electrochemical processes is a topic of great interest to ensure the stable performance of electrochemical cells and devices. For example, the stability of Pt nanoparticles (NPs) in PEMFCs is a major technological challenge for the commercialization of PEMFCs. Pt dissolution is typically observed when PEMFC operation is cycled up to the oxide formation voltage (>0.9 V).

[0118] A carbon-based electrocatalyst is currently the most commonly used electrocatalyst in PEMFCs and contributes significantly to their cost. Despite its maturity and improved performance, the lifetime and stability of PEMFCs are severely limited by corrosion and degradation processes on the catalyst surface, leading to mass loss, structural evolution, and / or a reduction in the catalytically electrochemically active surface area (ECSA). Furthermore, precious metals such as pure platinum are very expensive.

[0119] Alternative electrocatalysts such as platinum alloys can offer cost savings, but they face challenges such as reduced durability and undesirable changes in catalytic activity as the alloy degrades. In other words, alloy electrocatalysts may not have substantially constant performance over their lifetime.

[0120] Overall, there is a need for an improved, more stable, less expensive electrocatalyst with overall stable performance for use in electrochemical cells.

[0121] In one or more embodiments, an electrochemical cell system is disclosed. The system can be a fuel cell or an electrolyzer and includes the components described above. The system includes an electrocatalyst in the CCL, the anode catalyst layer, or in both, which can be referred to as a "multi-catalyst".

[0122] The term multicatalyst can refer to a system of at least two types of electrocatalysts that differ from each other in chemical composition, structure, dimensions, function, physical properties, chemical properties, placement within the system, or a combination thereof.

[0123] For example, the multi-catalyst system may include a first electrocatalyst that is more stable but, for the same catalytic activity, more expensive than the second electrocatalyst. A non-restrictive example of an expensive but more durable first electrocatalyst could be pure Pt, Pd, or a combination thereof. Due to its durability, the first electrocatalyst may be placed, housed, or attached to a non-porous surface region of the substrate. This non-porous surface region may be a pore-free surface region or an outer surface region. Since the first electrocatalyst strongly bonds to the non-porous surface region, a relatively exposed location for its attachment on the outer, pore-free, non-porous surface region may be optimal. The first electrolyte may exhibit higher catalytic activity than the second electrocatalyst per unit mass.

[0124] To achieve savings in manufacturing costs, a second electrocatalyst can be introduced, thus reducing the loading of highly catalytically active pure precious metal without compromising the overall catalytic activity of the electrocatalyst system, the CCL, and / or the cell. The second electrocatalyst may be less expensive but also less durable or more susceptible to degradation than the first. A non-restrictive example of a second electrocatalyst could be a PtM alloy, where M can be a transition metal. The second electrolyte may exhibit lower catalytic activity than the first electrocatalyst per unit mass.

[0125] Since the second electrocatalyst is more susceptible to degradation, its placement can differ from that of the first electrocatalyst. The second electrocatalyst can be placed in relatively shielded or protected areas of the support substrate. These areas can include the porous sections of the substrate. The porous sections can contain multiple pores, including macropores, mesopores, and / or micropores. The porous sections can include a porous surface region. The second electrocatalyst can be placed in at least one section of the pores within the cavities of the pores, each cavity being defined by a wall. The second electrocatalyst can be placed only in mesopores. The second electrocatalyst can be placed in both mesopores and micropores.The second electrocatalyst can be accommodated in at least approximately 30, 40, 50, 60 or 70% of the pores, based on the total number of pores in the support substrate area.

[0126] The second electrocatalyst can be located on the walls of the pores, at the bottom of the pores, at the top of the pores, or a combination thereof, as in the Fig. 21A, Fig. Figure 21B shows that the surface of the pores can be modified as described above to increase adhesion.

[0127] It is conceivable that the first electrocatalyst is located in at least some of the pores, e.g., in macropores, in addition to being situated on the outer surface region of the support substrate. It is also conceivable that at least some particles of the first electrocatalyst are arranged adjacent to or directly adjacent to one of the pores, for example, on an outer surface of the pores, as in the Fig. Figure 21B shows the first electrocatalyst. Alternatively, the first electrocatalyst can be arranged predominantly at a distance from the pores, where the distance is greater than a macropore, mesopore and / or micropore diameter.

[0128] It is also conceivable that at least some of the pores contain a mixture of the first and second electrocatalysts. This mixture can contain up to approximately 30% of the first electrocatalyst, based on the total number of electrocatalyst particles in the pore.

[0129] The concentration of the first electrocatalyst particles along or within the area of ​​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 may be found near or in close proximity to one or more pores.

[0130] Furthermore, the concentration of the second electrocatalyst can be highest in the pores. However, at least some of the particles of the second electrocatalyst can 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, as shown in the Fig. 21B shown.

[0131] The support substrate and / or the multi-catalyst system can thus have one or more regions containing both the first and the second electrocatalyst. These one or more regions can include the pore edges, the external parts of the pores, the outer surface-pore interface, or a combination thereof.

[0132] The Fig. Figure 20 shows a non-restrictive example of a multi-catalyst system 499 implemented on a support substrate 450. The multi-catalyst system comprises a first electrocatalyst 497 located on the non-porous surface region of the support substrate 450. The multi-catalyst system 499 comprises 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 in contact with the non-porous outer surface. The pores may have a roughened surface. The pores may have the same or different dimensions, height, width, depth, roughness, shape, and configuration.

[0133] The pores may have walls that slope gradually from the outer surface to the pores. The pores may have walls at an angle of approximately 45–135 degrees with respect to the outer surface. The pores may be large enough to accommodate one or more particles of the second electrocatalyst. The one or more particles may be approximately 1–10, 2–8, or 3–5 particles. The particles of the second electrocatalyst may be accumulated, dispersed, uniformly dispersed, or randomly arranged within the pores.

[0134] The Fig. Figure 21A shows an alternative view of a non-restrictive example of a multi-catalyst system 499. The system comprises a first electrocatalyst 497 located on the non-porous surface region 471 of the support substrate 450. The system also includes a second electrocatalyst 498 arranged or housed at different depths within the depicted pore cavity 496. In the non-restrictive example of Fig. 21A the second electrocatalyst particles 498 have a smaller diameter than the particles of the first electrocatalyst 497 and are distributed towards the lower regions of the pore cavity 496.

[0135] In the context of the CCL, the pores are filled with an electrolyte such as the ionomer 452. The same or a different ionomer can be in contact with or surround the outer surface of the support substrate 450 and the inner volume of the pores 496, as will be explained below.

[0136] In a non-restrictive example of Fig. In 21B, the first electrocatalyst is located on the outer surface region of the support substrate 450, but also on the upper edge of a wall 473 that defines a pore 496. The first electrocatalyst particle 497 is thus located directly next to the pore 496. The electrocatalyst particle 497 can alternatively also be a particle of the second electrocatalyst 498. In the non-restrictive example of Fig. In 21B, the second electrocatalyst particle 498 has a larger diameter than the first electrocatalyst particle 497, and the pore shape keeps the second electrocatalyst particle 498 shielded.

[0137] The ratio of the first to the second electrocatalyst, or vice versa, can be approximately 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 2:3, 4:5, or similar. The support substrate, the CCL, the cell, and the system can contain approximately the same volume of the first and second electrocatalysts. Alternatively, the volume of either the first or the second electrocatalyst can be larger than the volume of the other electrocatalyst.

[0138] Furthermore, it is conceivable that more than two types of catalysts are present in the system. For example, different types of alloy-based catalysts may be contained in the porous cavities, on the non-porous surface, or both.

[0139] The support substrate with the multi-catalyst system can be fabricated by one or more methods such as atomic layer deposition, chemical vapor deposition, sputtering, or other techniques for depositing an electrocatalyst onto the substrate. A shield or mask can be used if the electrocatalysts are applied separately. A shield or mask can also be applied over one or more pores if the first electrocatalyst is applied to the outer surface. Another shield or mask can be applied over the outer surface of the substrate if the second electrocatalyst is applied to the pore surfaces.

[0140] To further optimize the performance of the electrochemical cells and improve oxygen transport within the CCL, a multi-electrolyte can be introduced into the system.

[0141] A multi-electrolyte system can contain more than one type of electrolyte within the CCL (Cold Cell Liquid). It can include a primary electrolyte and a secondary electrolyte, which may differ in their chemical composition, internal structure, function, physical properties, chemical properties, placement within the system, or a combination thereof.

[0142] For example, the first electrolyte may be structured to exhibit good proton transport or proton conductivity, but be less effective at preventing electrocatalyst degradation than the second electrolyte, have lower oxygen conductivity, or both. A non-restrictive example of the first electrolyte could be Nafion™ or a similar material. The first electrolyte may be located outside the porous portions of the substrate support, in direct contact with the outer, non-porous surface area of ​​the substrate support, and / or closely adhere to the non-porous surface area of ​​the substrate support.

[0143] The second electrolyte can be structured to prevent electrocatalyst degradation, secondary metal leaching from PtM alloys, transport, or a combination thereof. The second electrolyte can be structured to have a lower proton transport capacity or proton conductivity, a higher oxygen transport capacity or oxygen conductivity, or both, than the first electrolyte. The second electrolyte can be located in at least some or all of the pore spaces within the porous structure of the substrate support. The second electrolyte can be an ionic liquid, HOPI, or similar. The second electrolyte can exhibit a greater affinity or adhesion to the support substrate than the first electrolyte.The second electrolyte can be structured in such a way that it remains in the pores of the porous area throughout the cell's lifetime through adhesion, capillary forces, or a combination thereof.

[0144] The first and second electrolytes may be miscible. They may contain a mixture of the first and second electrolytes in a ratio of approximately 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 2:3, 4:5, or similar. The mixture may be present in at least some parts of the CCL, for example, in the vicinity of or immediately near the pores, at the interface between the first and second electrolytes, or in both. The concentration of one of the two electrolytes at the interface may gradually increase towards the main volume of that electrolyte.

[0145] The CCL can therefore contain at least one first concentration c1 of the first electrocatalyst and one second concentration of the first electrocatalyst. The first concentration c1 is a concentration of the first electrolyte at the outer surface of the substrate support, within the CCL space free of substrate pores, or both. The second concentration c2 is a concentration of the first electrolyte near the second electrolyte, the pore cavity, the pore top, or a combination thereof. The second concentration c2 can be lower than the first concentration c1.

[0146] The CCL can contain at least one first concentration c3 of the second electrocatalyst and one second concentration c4 of the second electrocatalyst. The first concentration c3 is the concentration of the first electrolyte at the interface between the first and second electrolytes, in the upper part of the pore cavity, at the external outer edges of the pore, or a combination thereof. The second concentration c4 is the concentration of the first electrolyte within the pore, in the middle part of the pore cavity, in the lower part of the pore cavity, at the walls of the cavity, or a combination thereof. The second concentration c4 can be higher than the first concentration c3.

[0147] Alternatively, to prevent the electrolytes from mixing at the interface, the pores can be covered or capped with a material. It is also conceivable to cover the entire substrate. The cap or cover can be a layer, a coating, or both. The cap is structured to physically separate the first electrolyte from the second. The material can be permeable to protons, O₂, and water to prevent unwanted transport obstacles or blockages. The material can be impermeable to the first electrolyte, the second electrolyte, or both. A non-restrictive example material could be a carbon-based coating, graphene, or both.

[0148] The CCL, cell, or system may contain a larger volume of the first electrolyte than that of the second electrolyte. This is because the second electrolyte may be reserved for the pore cavities.

[0149] In a non-restrictive example from the Fig. 22 A portion of a CCL 454 contains a first electrolyte surrounding the support substrate. The first electrolyte 481 may exhibit a first proton conductivity and a first rate of electrocatalyst dissolution prevention. The CCL 454 also contains a second electrolyte 483 located within the cavities of the pores 496. The second electrolyte 483 may exhibit a second proton conductivity and a second rate of electrocatalyst dissolution prevention. The first proton conductivity is greater than the second proton conductivity. The first rate of electrocatalyst dissolution prevention is lower than the second rate of electrocatalyst dissolution prevention. The first and second electrolytes form an interface 485, which exhibits one or more of the properties described above.

[0150] The Fig. Figure 22 also shows non-restrictive examples of the placement of the electrocatalyst. The electrocatalyst can be located on the outer surface region of the substrate support 450, in the pore cavities 496 of the porous region, or in both. The pores and the electrocatalyst particles can have one or more of the properties described in the specification.

[0151] In an alternative representation of the multi-electrolyte system of Fig. Figure 23A shows the substrate support 450 with a pore 496. The pore cavity is filled with a second electrolyte 483. The first electrolyte 481 is shown to surround the substrate support 450 and the pore 496. The first and second electrolytes form an interface 485 between them.

[0152] The interface between the first electrolyte and the second electrolyte is in Fig. Figure 23A is shown and labelled 485. The first and second concentrations c1, c2 of the first electrolyte and the first and second concentrations c3, c4 of the second electrolyte are given.

[0153] In an alternative embodiment, electrolyte concentration fluctuations or differences within the CCL are eliminated or minimized by introducing a cap 475 over the pores 496. The cap can prevent contact between the first and second electrolytes, as explained above.

[0154] An alternative form of the cap 475' is in the Fig. 24 shown. As in the Fig.As can be seen in Figure 24, the cap 475' extends over the entire surface of the substrate support, so that the first electrolyte 481 is in contact with the cap 475' and not with the substrate support 450. The cap 475' can prevent the formation of an interface between the first and second electrolytes. The cap or coating can be selectively applied to one or more parts of the support substrate, covering not the entire surface of the support substrate, but substantially large areas of both the porous and non-porous regions.

[0155] In at least some embodiments, it is conceivable that only some of the pores of the total porosity of the support substrate contain the second electrolyte. The pores containing the second electrolyte would be those containing electrocatalyst particles. At least some of the pores can be free of electrocatalyst particles and contain a first electrolyte.

[0156] It is also conceivable that more than two electrolytes are introduced into the system. For example, some of the pores could be filled with a third electrolyte that has advantageous properties tailored to a specific type of electrocatalyst.

[0157] A method for forming the multi-electrolyte system is disclosed herein. The method may first include filling the pore cavities with the second electrolyte described above. The method may involve completely filling the pores so that the entire volume of the pores is filled with the electrolyte. Subsequently, a first electrolyte may be applied to the non-porous surface area and over the filled pores to form an interface between the first electrolyte and the second electrolyte.

[0158] The method may involve selectively applying the second electrolyte to a first portion of the pores of the support substrate. The method may also involve leaving some of the pores free of the second electrolyte. The method may involve applying the second electrolyte to the pores containing electrocatalyst particles. The method may include the use of a mask to cover pores and / or areas that are to remain free of the second electrolyte.

[0159] Alternatively, prior to the application of the first electrolyte within the volume of the CCL, a cap or coating as described herein can be selectively applied over the pores and / or non-porous areas containing the second electrolyte. Alternatively, the method can also involve applying a cap or coating over part or all of the surface of the support substrate, including the porous and non-porous areas.

[0160] The following applications are related to the present application: US Patent Application Serial No. (RBPA 0389, 0399, 0403 and 0404 PUS), filed on June 16, 2022, which are incorporated herein by reference in their entirety.

[0161] While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The words used in the description are descriptive rather than limiting, and it is understood that various modifications may be made without departing from the spirit and scope of the disclosure. As previously described, the features of different embodiments can be combined to form further embodiments of the invention that may not be expressly described or illustrated.While various embodiments might be described as advantageous or preferred over other embodiments or implementations of the prior art with respect to one or more desired properties, those skilled in the art recognize that one or more features or properties may be compromised to achieve desired overall system properties, which depend on the specific application and implementation. These properties may include, but are not limited to, cost, strength, durability, life-cycle costs, marketability, appearance, packaging, size, ease of maintenance, weight, manufacturability, ease of assembly, etc.Insofar as embodiments are described as less desirable than other embodiments or implementations of the prior art with respect to one or more features, these embodiments are not outside the scope of the disclosure and may be desirable for certain applications.

Claims

[1] Electrochemical cell comprising: an anode; a cathode and a membrane that physically separates the anode from the cathode, wherein the cathode comprises a cathode catalyst layer comprising an ionomer and an electrocatalyst support substrate forming an ionomer-support interface with a covalent bond between the substrate and the ionomer via a graft bond, the substrate further comprising a plurality of terminated hydrophilic groups. [2] The cell of claim 1, wherein the graft compound is an aromatic compound and wherein the covalent bond is between a hydrophilic group of the substrate and an aryl group of the aromatic compound. [3] The cell of claim 1, wherein the covalent bond is a substrate-acetyl bond. [4] The cell of claim 1, wherein the interface further comprises a covalent bond between a reactive group of the graft compound and an ionomer carbon atom adjacent to a hydrophilic group of the ionomer. [5] Cell according to claim 1, wherein the graft compound is based on iodonium. [6] The cell of claim 1, wherein the covalent bond contains oxygen atoms of an epoxy group. [7] The cell of claim 1, wherein the substrate comprises a carbon-based material. [8] The cell of claim 1, wherein the graft compound contains a benzoliodonium group. [9] Cathode catalyst layer-ionomer-support interface comprising: an ionomer with hydrophilic side chains and a hydrophobic backbone and an electrocatalyst support substrate, wherein the ionomer is covalently bonded to the carrier substrate via a graft bond such that at least some of the hydrophilic side chains are oriented towards the carrier substrate and the hydrophobic backbone is not oriented towards the carrier substrate. [10] The interface of claim 9, wherein the graft compound contains an epoxy group. [11] The interface of claim 9, wherein the covalent bond is a substrate-acetyl bond. [12] The interface of claim 9, wherein the graft compound is an aromatic compound and wherein the covalent bond includes a hydrophilic group of the substrate and an aryl group of the aromatic compound. [13] The interface of claim 9, wherein the graft compound is grafted onto the ionomer chain adjacent to the hydrophobic backbone. [14] Interface according to claim 9, wherein the graft compound is based on diazonium or iodonium. [15] A process for forming an ionomer-electrocatalyst support interface, comprising: Forming a functionalized ionomer by reacting an ionomer with a compound having a reactive group adjacent to a leaving group; Grafting the functionalized ionomer onto an electrocatalyst support by stimulating the leaving group so that the leaving group detaches to form a radical at the reactive group, resulting in that the radical attacks a dangling linkage on the electrocatalyst support and forms a covalent bond between the functionalized ionomer and the support; and Passivating remaining dangling bonds on the electrocatalyst support to terminate their ends. [16] The method of claim 15, wherein said forming comprises an addition reaction of a benzenediazonium or benzeniodonium group to the ionomer. [17] The method of claim 15, wherein the grafting comprises forming the covalent bond between a hydrophilic group of the substrate and an aryl group of the grafting compound. [18] The method of claim 15, further comprising activating the grafting reaction by a voltage change. [19] The process according to claim 15, wherein the leaving group N + or I - includes. [20] The method of claim 15, wherein the passivation comprises electrochemical activation by means of a voltage applied to the carrier.

Images