WO2022108585A1

WO2022108585A1 - Components in electrochemical devices protected with max phase materials

Info

Publication number: WO2022108585A1
Application number: PCT/US2020/061189
Authority: WO
Inventors: Soo Kim; Alexander Eifert; Torsten TROSSMAN; Thomas Wagner; Charles Tuffile
Original assignee: Robert Bosch Gmbh
Priority date: 2020-11-19
Filing date: 2020-11-19
Publication date: 2022-05-27

Abstract

A component of an electrochemical device includes a substrate and a MAX phase material mixed with a nitride compound and/or an oxide compound. The MAX phase material is a MAX phase compound with a general formula of Mn+1AXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N. The MAX phase compound is Nb2SnC, Ti4AlN3, Ti3SnC2, Nb2PC, and Nb4A1C3, V2PC, Ti3SiC2, Zr2SnC, Zr2SC, Ti3AlC2, Ti2SnC, Ti2SC, Nb2AlC, or a combination thereof. The oxide compound is a titanium oxide (TiOx, 0.5 ≤ x ≤ 2), a niobium oxide (NbOx, 1 ≤ x ≤ 3), or a magnesium titanium oxide (MgTi2O5-x, 0 ≤ x ≤ 5).

Description

COMPONENTS IN ELECTROCHEMICAL DEVICES PROTECTED WITH MAX PHASE MATERIALS

TECHNICAL FIELD

[0001] The present disclosure relates to components in electrochemical devices protected with MAX phase materials. The electrochemical device may be fuel cells or electrolyzers. The component may be a bipolar plate of a fuel cell coated with the MAX phase material. The component may also be a catalyst layer including the MAX phase material.

BACKGROUND

[0002] Metals have been a widely used material for thousands of years. Various methods have been developed to preserve metals and prevent their corrosion or disintegration into oxides, hydroxides, sulfates, and other salts. Metals in some industrial applications are especially susceptible to corrosion due to aggressive operating environments. A non-limiting example may be metal components of a fuel cell (e.g. bipolar plates). For instance, bipolar plates are required to be not only sufficiency chemically inert to resist degradation in a highly corrosive environment of the fuel cell, but also electrically conducting to facilitate electron transfer for the oxygen reduction reaction of the fuel cell. Finding a material that meets both the requirements of anti-corrosion and electric conduction has been a challenge.

SUMMARY

[0003] According to one embodiment, a component of an electrochemical device is disclosed. The component may include a substrate and a MAX phase material mixed with a nitride compound and/or an oxide compound. The MAX phase material is a MAX phase compound with a general formula of Mn+iAXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N. The MAX phase compound may be Nb₂SnC, Ti₄AlN₃, Ti₃SnC₂, Nb₂PC, and Nb₄AlC₃, V₂PC, Ti₃SiC₂, Zr₂SnC, Zr₂SC, Ti₃AlC₂, Ti₂SnC, Ti₂SC, Nb₂AlC, or a combination thereof. The oxide compound may be a titanium oxide (TiOx, 0.5 < x < 2), a niobium oxide (NbOx, 1 < x < 3), or a magnesium titanium oxide (MgTLOs-x, 0 < x < 5). [0004] According to another embodiment, a component of an electrochemical device is disclosed. The component may include a substrate made of stainless steel and having at least one surface. The component may also include at least one surface coating layer on each of the at least one surface. The at least one surface coating layer may include a MAX phase material mixed with a nitride compound and/or an oxide compound. The MAX phase material is a MAX phase compound with a general formula of Mn+iAXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N. The MAX phase compound may be Nb₂SnC, D4AIN3, Ti₃SnC₂, Nb₂PC, and Nb₄AlC₃, V2PC, Ti₃SiC₂, ZnSnC, Zr₂SC, Ti₃AlC₂, Ti₂SnC, Ti2SC, Nb2AlC, or a combination thereof. The oxide compound may be a titanium oxide (TiOx, 0.5 < x < 2), a niobium oxide (NbOx, 1 < x < 3), or a magnesium titanium oxide (MgTi2Os-x, 0 < x < 5).

[0005] According to yet another embodiment, a catalyst layer of an electrochemical device is disclosed. The catalyst layer may include a substrate and a MAX phase material. The MAX phase material is a MAX phase compound with a general formula of Mn+iAXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N. The MAX phase compound may be Nb2SnC, Ti4AlN3, Ti3SnC2, Nb2PC, and Nb4AlC3, V2PC, Ti3SiC2, ZnSnC, ZnSC, Ti3AlC2, Ti2SnC, Ti2SC, Nb2AlC, or a combination thereof. The MAX phase material may be mixed with a nitride compound and/or an oxide compound. The oxide compound may be a titanium oxide (TiOx, 0.5 < x < 2), a niobium oxide (NbOx, 1 < x < 3), or a magnesium titanium oxide (MgTi2Os-x, 0 < x < 5). The substrate may be a catalyst support layer which supports a fuel cell catalyst. The catalyst support layer may include a carbon material and/or an oxide material. The oxide material may be TiCh, SnCh, or a combination thereof. The catalyst support layer may include metal elements other than Pt. The metal elements may be transition metals, such as Co, Ni, Fe and/or Ti. The metal elements may also be noble metals, such as Ru, Pd, Ag, and/or Au.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 depicts a schematic diagram of a computing platform that may be utilized to implement a data-driven materials screening method.

[0007] Figure 2 depicts a schematic phase diagram showing a reaction enthalpy (eV/atom) of a reaction between TiN and H3O as a function of a molar fraction of H3O in a reaction environment. [0008] Figure 3A is a schematic cross-sectional view of a fuel cell.

[0009] Figure 3B is a schematic perspective view of components of the fuel cell shown in Figure 3 A.

DETAILED DESCRIPTION

[0010] Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments can take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the embodiments. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures can be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for applications or implementations.

[0011] This present disclosure is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing embodiments of the present disclosure and is not intended to be limiting in any way.

[0012] As used in the specification and the appended claims, the singular form “a,” “an,” and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.

[0013] The description of a group or class of materials as suitable for a given purpose in connection with one or more embodiments implies that mixtures of any two or more of the members of the group or class are suitable. Description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description and does not necessarily preclude chemical interactions among constituents of the mixture once mixed.

[0014] Except where expressly indicated, all numerical quantities in this description indicating dimensions or material properties are to be understood as modified by the word "about" in describing the broadest scope of the present disclosure.

[0015] The first definition of an acronym or other abbreviation applies to all subsequent uses herein of the same abbreviation and applies mutatis mutandis to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurement of a property is determined by the same technique as previously or later referenced for the same property.

[0016] The term “substantially” may be used herein to describe disclosed or claimed embodiments. The term “substantially” may modify any value or relative characteristic disclosed or claimed in the present disclosure. “Substantially” may signify that the value or relative characteristic it modifies is within ± 0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5% or 10% of the value or relative characteristic.

[0017] Reference is being made in detail to compositions, embodiments, and methods of embodiments known to the inventors. However, disclosed embodiments are merely exemplary of the present disclosure which may be embodied in various and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, rather merely as representative bases for teaching one skilled in the art to variously employ the present disclosure.

[0018] Corrosion may cause degradation to metal components of an electrochemical device, for example, metal components in a fuel cell or an electrolyzer. The metal component may be a bipolar plate or a catalyst layer of the electrochemical device. Corrosion is a process by which refined metal is converted to a more chemically stable form such as a metal oxide, hydroxide, sulfide and/or other salts. The more chemically stable form may be less desirable because it exhibits one or more less desirable properties or inhibits one or more desirable properties. The conversion may present a steady destruction of the metal material. The conversion may include the electrochemical oxidation of the metal with an oxidant such as oxygen or water. Corrosion may occur when a metal component is exposed to moisture in the air, to a solution with a relatively low pH or high pH, and/or various chemical substances such as acids and/or microbes. Elevated temperatures may also accelerate corrosion.

[0019] Fuel cells operate with a renewable energy carrier, such as hydrogen. A fuel cell catalyst material (e.g. platinum (Pt) catalyst material) is included in the catalyst layer of both the anode and the cathode of a fuel cell. Electrolyzers can undergo an electrolysis process to split water into hydrogen and oxygen. An electrolyzer catalyst material is included in the catalyst layer of both the anode and the cathode of an electrolyzer. The electrolyzer catalyst material may be ruthenium/ruthenium oxide (e.g. Ru/RuOx), iridium/iridium oxide (Ir/IrOx), or other binary or ternary metal/metal oxide made of Pt group metals (e.g. Pt, Ir, Os, Pd, Rh, or Ru), prestigious metals (e.g. Au or Ag), and/or transition metals (e.g. Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Hf, Ta, W, or Re).

[0020] Titanium nitride (TiN) is commonly used as a bipolar plate coating material for commercial-scale fuel cells (e.g. PEMFCs) and stack systems for certain applications, such as automotive and stationary applications. However, when a contact resistance at the interface between a bipolar plate coating material and the bipolar plate is high, a TiN-based bipolar plate coating material is subject to physical changes (e.g. phase or volume changes), which may further lead to defects and/or pin hole formations on the bipolar plate. Moreover, a TiN-based bipolar plate coating material may undergo chemical changes (e.g. dissolution or conversion to titanium oxides) during a fuel cell operation, which may lead to a high interfacial contact resistance and consequently impact the fuel cell performance. Therefore, a TiN-based bipolar plate coating material may not be an ideal protecting material for protecting bipolar plates from corrosion in a fuel cell environment.

[0021] MAX phase compounds are layered hexagonal carbides or nitrides with a general formula of Mn+iAXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is either C or N. To protect metal components, such as bipolar plates or catalyst layers, of an electrochemical device, from corrosion, what is needed are MAX phase materials that have resistant characteristics for these metal components. What is further needed are protective MAX phase materials capable of imparting anti-corrosive properties onto metal substrate in other chemically aggressive environments. [0022] As disclosed herein, first-principles density functional theory (DFT) algorithms, calculations and/or methodologies are used to model the chemical reactivity of MAX phase compounds against acidic species, such as H3O, HF, SO3, or HC1, which are commonly present in an acidic environment of an electrochemical device (e.g. a fuel cell or an electrolyzer), to identify MAX phase compounds that are comparably more effective than TiN as materials that protect metal components of the electrochemical device from acidic corrosion. Particularly, a data-driven materials screening method is employed for such identifications. These comparably superior MAX phase compounds may also be used in catalyst layers and/or catalyst supports in the electrochemical device. In one or more embodiments, the following MAX phase compounds are suitable for use to protect metal components of an electrochemical device susceptible to acidic corrosion: Nb4AlC3, Ti4AlN3, Nb₂SnC, Ti₃SnC₂, Zr₂SC, Ti₂SnC, Zr₂SnC, Nb₂PC, Nb₂AlC, Ti₃SiC₂, Ti₃AlC₂, Ti₂SC, V₂PC, and a combination thereof.

[0023] Figure 1 depicts a schematic diagram of a computing platform that may be utilized to implement a data-driven materials screening method. The computing platform 10 may include a processor 12, a memory 14, and a non-volatile storage 16. The processor 12 may include one or more devices selected from high-performance computing (HPC) systems including high-performance cores, microprocessors, micro-controllers, digital signal processors, microcomputers, central processing units, field programmable gate arrays, programmable logic devices, state machines, logic circuits, analog circuits, digital circuits, or any other devices that manipulate signals (analog or digital) based on computer-executable instructions residing in memory. The memory 14 may include a single memory device or a number of memory devices including random access memory (RAM), volatile memory, non-volatile memory, static random-access memory (SRAM), dynamic random-access memory (DRAM), flash memory, cache memory, or any other device capable of storing information. The non-volatile storage 16 may include one or more persistent data storage devices such as a hard drive, optical drive, tape drive, non-volatile solid-state device, cloud storage or any other device capable of persistently storing information.

[0024] The processor 12 may be configured to read into memory and execute computerexecutable instructions residing in a DFT software module 18 of the non-volatile storage 16 and embodying DFT slab model algorithms, calculations and/or methodologies of one or more embodiments. The DFT software module 18 may include operating systems and applications. The DFT software module 18 may be compiled or interpreted from computer programs created using a variety of programming languages and/or technologies, including, without limitation, and either alone or in combination, Java, C, C++, C#, Objective C, Fortran, Pascal, Java Script, Python, Perl, and PL/SQL.

[0025] Upon execution by the processor 12, the computer-executable instructions of the DFT software module 18 may cause the computing platform 10 to implement one or more of the DFT algorithms and/or methodologies disclosed herein. The non-volatile storage 16 may also include DFT data 20 supporting the functions, features, calculations, and processes of the one or more embodiments described herein.

[0026] The program code embodying the algorithms and/or methodologies described herein is capable of being individually or collectively distributed as a program product in a variety of different forms. The program code may be distributed using a computer readable storage medium having computer readable program instructions thereon for causing a processor to carry out aspects of one or more embodiments. The computer readable storage medium, which is inherently non-transitory, may include volatile and non-volatile, and removable and non-removable tangible media implemented in any method or technology for storage of information, such as computer-readable instructions, data structures, program modules, or other data. The computer readable storage media may further include RAM, ROM, erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other solid state memory technology, portable compact disc read-only memory (CD-ROM), or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and which can be read by a computer. Computer readable program instructions may be downloaded to a computer, another type of programmable data processing apparatus, or another device from a computer readable storage medium or to an external computer or external storage device via a network.

[0027] Computer readable program instructions stored in the computer readable medium may be used to direct a computer, other types of programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions that implement the functions, acts, and/or operations specified in the flowcharts or diagrams. In certain alternative embodiments, the functions, acts, and/or operations specified in the flowcharts and diagrams may be re-ordered, processed serially, and/or processed concurrently consistent with one or more embodiments. Moreover, any of the flowcharts and/or diagrams may include more or fewer nodes or blocks than those illustrated consistent with one or more embodiments.

[0028] Referring to Figure 1, a data-driven materials screening method may be utilized to identify MAX phase compounds that are suitable for use to protect metal components (e.g. bipolar plates or catalyst layers) of an electrochemical device (e.g. a fuel cell or an electrolyzer) from acidic corrosion. The data-driven materials screening method may evaluate compounds in terms of their chemical reactivities against commonly present species in the acidic environment. Examples of these species include FEO, HF, SO₃, and HC1.

[0029] In one or more embodiments, the MAX phase compounds may be CnAlC, CnGaC, CnGeC, Hf₂InC, Hf₂PbC, Hf₂SC, Hf₂SnC, Hf₂TlC, Mo₂GaC, Nb₂AlC, Nb₂AsC, Nb₂CuC, Nb₂GaC, NbflnC, Nb₂PC, Nb₂SC, Nb₂SnC, Sc₂InC, Ta₂AlC, Ta₂GaC, Ti₂AlC, Ti₂CdC, Ti₂GaC, Ti₂GeC, Ti₂InC, Ti₂PbC, Ti₂SC, Ti₂SnC, Ti₂TlC, Ti₂ZnC, V₂A1C, V₂AsC, V₂GaC, V₂GeC, V₂PC, V₂ZnC, ZnAlC, Zr₂InC, Zr₂PbC, Zr₂SC, Zr₂SnC, ZnTIC, CnGaN, Hf₂SnN, Ti₂AlN, Ti₂GaN, Ti₂InN, Ti₂ZnN, V₂GaN, ZnlnN, ZnTIN, Ta₃AlC₂, Ti₃AlC₂, Ti₃GaC₂, Ti₃GeC₂, Ti₃InC₂, Ti₃SiC₂, Ti₃SnC₂, Ti₃ZnC₂, V₃A1C₂, Zr₃AlC₂, Nb₄AlC₃, Ta₄AlC₃, Ti₄GaC₃, Ti₄GeC₃, Ti₄SiC₃, V₄A1C₃, Ti₄AlN₃, and MO₄VA1C₄.

[0030] To better understand the chemical reactivity of a MAX phase compound against one of the acidic species, the data-driven materials screening method is first used to examine the chemical reactivity of TiN against each of the acidic species under similar conditions. The chemical reactivity of TiN against each of the acidic species may then be used as a reference to identify MAX phase compounds that are comparably more resistant against the acidic species than TiN.

[0031] Figure 2 depicts a schematic phase diagram showing a reaction enthalpy (eV/atom) of a reaction between TiN and H₃O as a function of a molar fraction of H₃O in a reaction environment. The molar faction of H₃O is in a range of 0 and 1. As shown in Figure 2, when the molar faction of H₃O is 0, there is no H₃O and 100% of TiN in the reaction environment. Conversely, when the molar faction of H₃O is 1, there is no TiN and 100% H₃O in the reaction environment. As the molar fraction of H3O increases from 0, a first stable decomposition reaction occurs at Point A, where the molar fraction of H3O is about 0.556 and the reaction enthalpy of the first stable decomposition reaction is about -0.054 eV/atom. The first stable decomposition reaction occurs when there is a dilute amount of H3O in the reaction environment. Reaction (1) is expressed below to illustrate the first stable decomposition reaction:

0.556 H3O + 0.444 TiN 0.444 H3N + 0.167 TiH₂ + 0.278 TiCh (1)

[0032] According to reaction (1), after reacting with the dilute amount of H3O, TiN is turned into H3N, TiH2, and TiCh.

[0033] Still referring to Figure 2, as the molar fraction of H3O keeps increasing, the most stable decomposition reaction may occur at Point B, where the molar fraction of H3O is about 0.667 and the reaction enthalpy of the most stable decomposition reaction is about -0.055 eV/atom. The most stable decomposition reaction occurs when there is an abundant amount of H3O in the reaction environment. Reaction (2) is included hereby to illustrate the most stable decomposition reaction:

0.667 H3O + 0.333 TiN 0.333 H3N + 0.333 TiCh + 0.5H₂ (2)

[0034] According to reaction (2), after reacting with the abundant amount of H3O, TiN is turned into H3N and TiO₂.

[0035] Apart from reacting with H3O, TiN may also react with other acidic species in the acidic fuel cell environment, such as HF, SO3, and HC1. The data-driven materials screening method may be further employed to study the chemical reactivities of TiN against HF, SO3, and HC1 under similar conditions, respectively. In each scenario, there may be a first stable decomposition reaction between the acidic species and TiN, which occurs when the concentration of the acidic species is dilute in the reaction environment. In each scenario, there may also be the most stable decomposition reaction between the acidic species and TiN, which occurs when the concentration of the acidic species is abundant in the reaction environment. It may be possible that the first stable decomposition reaction and the most stable decomposition reaction between the acidic species and TiN are identical. The reaction enthalpy of each reaction, if possible, may also be calculated using the data-driven materials screening method. [0036] Table 1 depicts information of a first stable decomposition reaction between TiN and H3O, HF, SO3, or HC1, respectively. Particularly, Table 1 provides a reaction equation of the first stable decomposition reaction and a reaction enthalpy of each reaction.

Table 1. Information of a first stable decomposition reaction between TiN and H3O, HF, SO3, or HC1, respectively.

[0037] Table 2 depicts information of the most stable decomposition reaction between TiN and H3O, HF, SO3, or HC1, respectively. Particularly, Table 2 provides a reaction equation of the most stable decomposition reaction and a reaction enthalpy of each reaction.

Table 2. Information of a most stable decomposition reaction between TiN and H3O, HF, SO3, or HC1, respectively.

[0038] Now, a process for screening the MAX phase compounds is described. Using the data- driven materials screening method, each MAX phase compound is evaluated in terms of its chemical reactivities against H3O, HF, SO3, or HC1, respectively, including the scenario where there is a dilute amount of the acidic species or an abundant amount of the acidic species in a reaction environment.

[0039] Table 3 depicts information of a first stable decomposition reaction between a dilute amount of H3O and each of the MAX phase compounds, respectively. Particularly, Table 3 provides a reaction equation of the first stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the chemical reactivity of each MAX phase compound against H3O, Table 3 provides a molar fraction between H3O and each MAX phase compound. Table 3 further provides a penalty point (e.g. PPI) regarding the molar fraction, where PPI of 1.00 is assigned to the reference reaction between TiN and the dilute amount of H3O. In addition, Table 3 provides another penalty point (e.g. PP2) regarding the reaction enthalpy of each reaction, where PP2 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the dilute amount of H3O.

Table 3. Information of a first stable decomposition reaction between a dilute amount of H3O and each MAX phase compound, respectively.

[0040] Table 4 depicts information of the most stable decomposition reaction between an abundant amount of H3O and each of the MAX phase compounds, respectively. Particularly, Table 4 provides a reaction equation of the most stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each element against H3O, Table 4 provides a molar fraction between H3O and each MAX phase compound. Table 4 further provides a penalty point (e.g. PP3) regarding the molar fraction, where PP3 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of H3O. In addition, Table 4 provides another penalty point (e.g. PP4) regarding the reaction enthalpy of each reaction, where PP4 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the abundant amount of H3O.

Table 4. Information of the most stable decomposition reaction between an abundant amount of H3O and each MAX phase compound, respectively.

[0041] Table 5 depicts information of a first stable decomposition reaction between a dilute amount of HF and each of the MAX phase compounds, respectively. Particularly, Table 5 provides a reaction equation of the first stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each MAX phase compound against HF, Table 5 provides a molar fraction between HF and each MAX phase compound. Table 5 further provides a penalty point (e.g. PP5) regarding the molar fraction, where PP5 of 1.00 is assigned to the reference reaction between TiN and the dilute amount of HF. In addition, Table 5 provides another penalty point (e.g. PP6) regarding the reaction enthalpy of each reaction, where PP6 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the dilute amount of HF.

Table 5. Information of a first stable decomposition reaction between a dilute amount of HF and each MAX phase compound, respectively.

[0042] Table 6 depicts information of the most stable decomposition reaction between an abundant amount of HF and each of the MAX phase compound, respectively. Particularly, Table 6 provides a reaction equation of the most stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each element against HF, Table 6 provides a molar fraction between HF and each MAX phase compound. Table 6 further provides a penalty point (e.g. PP7) regarding the molar fraction, where PP7 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of HF. In addition, Table 6 provides another penalty point (e.g. PP8) regarding the reaction enthalpy of each reaction, where PP8 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the abundant amount of HF. Table 6. Information of the most stable decomposition reaction between an abundant amount of HF and each MAX phase compound, respectively.

[0043] Table 7 depicts information of a first stable decomposition reaction between a dilute amount of SO3 and each of the MAX phase compound, respectively. Particularly, Table 7 provides a reaction equation of the first stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each MAX phase compound against SO3, Table 7 provides a molar fraction between H3O⁺ and each MAX phase compound. Table 7 further provides a penalty point (e.g. PP9) regarding the molar fraction, where PP9 of 1.00 is assigned to the reference reaction between TiN and the dilute amount of SO3. In addition, Table 7 provides another penalty point (e.g. PP10) regarding the reaction enthalpy of each reaction, where PP10 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the dilute amount of SO3.

Table 7. Information of a first stable decomposition reaction between a dilute amount of SO3 and each MAX phase compound, respectively.

[0044] Table 8 depicts information of the most stable decomposition reaction between an abundant amount of SCh and each of the MAX phase compounds, respectively. Particularly, Table 8 provides a reaction equation of the most stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each element against SCh, Table 8 provides a molar fraction between SCh and each MAX phase compound. Table 8 further provides a penalty point (e.g. PPI 1) regarding the molar fraction, where PPI 1 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of SO3. In addition, Table 8 provides another penalty point (e.g. PP12) regarding the reaction enthalpy of each reaction, where PP12 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the abundant amount of SO3.

Table 8. Information of the most stable decomposition reaction between an abundant amount of SO3 and each MAX phase compound, respectively.

[0045] Table 9 depicts information of a first stable decomposition reaction between a dilute amount of HC1 and each of the MAX phase compounds, respectively. Particularly, Table 9 provides a reaction equation of the first stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each MAX phase compound against HC1, Table 9 provides a molar fraction between HC1 and each MAX phase compound. Table 9 further provides a penalty point (e.g. PPI 3) regarding the molar fraction, where PPI 3 of 1.00 is assigned to the reference reaction between TiN and the dilute amount of HC1. In addition, Table 9 provides another penalty point (e.g. PP14) regarding the reaction enthalpy of each reaction, where PP14 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the dilute amount of HC1.

Table 9. Information of a first stable decomposition reaction between a dilute amount of HC1 and each MAX phase compound, respectively.

[0046] Table 10 depicts information of the most stable decomposition reaction between an abundant amount of HC1 and each of the MAX phase compounds, respectively. Particularly, Table 10 provides a reaction equation of the most stable decomposition reaction and a reaction enthalpy of each reaction. To easily compare the reactivity of each element against HC1, Table 10 provides a molar fraction between HC1 and each MAX phase compound. Table 10 further provides a penalty point (e.g. PPI 5) regarding the molar fraction, where PPI 5 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of HC1. In addition, Table 10 provides another penalty point (e.g. PP16) regarding the reaction enthalpy of each reaction, where PPI 6 of 1.00 is assigned to the reaction enthalpy of the reaction between TiN and the abundant amount of HC1.

Table 10. Information of the most stable decomposition reaction between an abundant amount of HC1 and each MAX phase compound, respectively.

[0047] Based on the information provided from Tables 3 and 10, a sum of the penalty points (EPP) is calculated for each MAX phase compound, i.e. EPP, ^and provided in Table 11. The sum of the penalty points for TiN is 16.00 (i.e. ΣPPTIN = 16.00). Table 11 further provides the molecular weight (MW) of each MAX phase compound, a sum of penalty points of each MAX phase compound per MW (ΣPP per MW), and a percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP per MW. ΣPP™ per MW is around 0.259. To calculate the percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP per MW, ΣPPTIN per MW is divided by the ΣPP per MW of each MAX phase compound. For example, since the ΣPP per MW for CnAlC is around 0.225, the percentage of improvement of CnAlC when compared to TiN thus equals 0.259/0.225, which is around 115.1%.

[0048] Table 11 also provides the density of each MAX phase compound, a sum of penalty points of each MAX phase compound per volume (ΣPP per volume), and a percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP per volume. ΣPP™ per volume equals (^PPUN per MW)* (the density of TiN), i.e. 0.259*5.340, which is around 1.381. To calculate the percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP per volume, ΣPPUN per volume is divided by the ΣPP per volume of each MAX phase compound. For example, since the ΣPP per volume for CnAlC is around 1.200, the percentage of improvement of CnAlC when compared to TiN thus equals 1.381/1.200, which is around 115.1%.

Table 11. A summary of the percentage of improvement of each MAX phase compound when compared to that of TiN.

[0049] Table 12 provides a list of top candidates of MAX phase compounds based on the data provided in Table 11. Specifically, Table 12 provides a total percentage of improvement of each top candidate when compared to TiN, which represents a sum of the percentage of improvement of each top candidate when compared to TiN based on the ΣPP per MW plus the percentage of improvement of each top candidate when compared to TiN based on the ΣPP per volume.

[0050] Table 12 also provides a percentage difference of improvement of each top candidate when compared to TiN. As shown in Table 11, the total percentage of improvement for TiN is 200.00%. As such, the percentage difference of improvement of each top candidate when compared to TiN equals a total percentage of improvement of each top candidate minus the total percentage of improvement for TiN (i.e. 200.00%). For example, since the total percentage of improvement of Nb2SnC is around 744.73% (i.e. 449.43% + 295.30%), the percentage difference of improvement of Nb2SnC when compared to TiN thus equals 744.73% - 200.00%, which is 544.73%. As shown in Table 12, the top candidates of MAX phase compounds all exhibit a percentage difference of improvement greater than 100%. This indicates that these MAX phase compounds may be comparably more effective than TiN as materials that protect fuel cell metal components from acidic corrosions in a fuel cell environment. Further, the top candidates of MAX phase compounds are selected based on other factors. For example, the top candidates do not include metal elements, such as Ta, Ga, In, Hf, Ge, or Tl, that are less practical (e.g. more expensive) than Co; and the top candidates do not include toxic metal elements, such as As or Pb.

Table 12. A list of top candidates of MAX phase compounds based on the data provided in Table 11.

[0051] Having discussed the chemical reactivities of the MAX phase compounds against the acidic species, including H₃O, HF, SO₃, or HC1, the data-driven materials screening method may also be used to evaluate the interfacial stabilities of these MAX phase compounds when applied to protect a metal substrate (e.g. stainless steel). The interfacial stabilities of the compounds may be examined by simulating reactions with surface oxides commonly present in the metal substrate. Examples of the surface oxides may be Cr₂O₃, NiO, or Fe₂O₃.

[0052] When TiN is applied to protect a metal substrate substantially made of Ti, TiN may be transformed into a Ti-rich nitride material, such as Ti2N. The reaction may be expressed, for example, as:

0.5 TiN + 0.5 Ti -^ 0.5 Ti₂N (3) [0053] When TiN is applied to protect a metal substrate that has surface oxides Cr₂O₃, TiN may be transformed into an oxide, and Cr₂O₃ may consume N to become CrNx. The reaction may be expressed, for example, as:

0.6 TiN + 0.4 Cr₂O₃ 0.6 TiCh + 0.2 Cr₂N + 0.4 CrN (4)

[0054] According to reaction (4), such a nitride-to-oxide and an oxide-to-nitride phase transformation may, however, lead to a significant volume change and morphology destruction at the interface between TiN and the metal substrate. Consequently, void spaces or local defects may be formed in the metal substrate, inducing degradations to the metal substrate. Additionally, since TiCh is an insulator, which may cause a high interfacial contact resistance of the metal substrate. Therefore, TiN may not be ideal to be used as a protective material to protect metal components (e.g. those generally made of stainless steel) of an electrochemical device (e.g. a fuel cell or an electrolyzer).

[0055] Table 13 depicts information of the most stable decomposition reaction between each of the MAX phase compounds listed in Table 12 and an abundant amount of Cr₂O₃. Particularly, Table 13 provides a reaction equation, if possible, of the most stable decomposition reaction and a reaction enthalpy of each reaction. Table 13 also provides a molar fraction between the abundant amount of Cr₂O₃ and each of the MAX phase compounds. Further, Table 13 provides a penalty point (e.g. PP17) regarding the molar fraction, where PP17 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of Cr₂O₃. PP17 is calculated by dividing the molar fraction between the abundant amount of Cr₂O₃ and TiN by the molar fraction between the abundant amount of Cr₂O₃ and each MAX phase compound. For example, since the molar fraction between the abundant amount of Cr₂O₃ and Nb₂SnC is 1.67, PP17 thus equals 0.67/1.67, which is around 0.40.

[0056] Table 13 further provides a reaction enthalpy (eV/atom) of the reaction between the abundant amount of Cr₂O₃ and each of the MAX phase compounds. Table 13 also provides another penalty point (e.g. PP18) regarding the reaction enthalpy of the reaction, where PP18 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of Cr₂O₃ (i.e. -0.074 eV/atom). PPI 8 is calculated by dividing the reaction enthalpy between the abundant amount of Cr₂O₃ and each MAX phase compound by that between the abundant amount of Cr₂O₃ and TiN. For example, since the reaction enthalpy between the abundant amount of Cr₂O₃ and Nb₂SnC is -0.068, PP18 thus equals -0.068/-0.074, which is about 0.92.

Table 13. Information of the most stable decomposition reaction between each of the MAX phase compounds listed in Table 12 and an abundant amount of CnCh.

[0057] Table 14 depicts information of the most stable decomposition reaction between each of the MAX phase compounds listed in Table 12 and an abundant amount of NiO. Particularly, Table 14 provides a reaction equation, if possible, of the most stable decomposition reaction and a reaction enthalpy of each reaction. Table 14 also provides a molar fraction between the abundant amount of NiO and each of the MAX phase compounds. Further, Table 14 provides a penalty point (e.g. PP19) regarding the molar fraction, where PP19 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of NiO. PPI 9 is calculated by dividing the molar fraction between the abundant amount of NiO and TiN by the molar fraction between the abundant amount of NiO and each MAX phase compound. For example, since the molar fraction between the abundant amount of NiO and NbiSnC is 4.99, PP19 thus equals 2.00/4.99, which is around 0.40.

[0058] Table 14 further provides a reaction enthalpy (eV/atom) of the reaction between the abundant amount of NiO and each of the MAX phase compound. Table 14 also provides another penalty point (e.g. PP20) regarding the reaction enthalpy of the reaction, where PP20 of 1.00 is assigned to the reference reaction between TiN and the abundant amount ofNiO (i.e. -0.529 eV/atom). PP20 is calculated by dividing the reaction enthalpy between the abundant amount of NiO and each MAX phase compound by that between the abundant amount ofNiO and TiN. For example, since the reaction enthalpy between the abundant amount of NiO and Nb₂SnC is -0.815, PP20 thus equals - 0.815/-0.529, which is about 1.54.

Table 14. Information of the most stable decomposition reaction between each of the MAX phase compounds listed in Table 12 and an abundant amount ofNiO.

[0059] Table 15 depicts information of the most stable decomposition reaction between each of the MAX phase compounds listed in Table 12 and an abundant amount of Fe₂O₃. Particularly, Table 15 provides a reaction equation, if possible, of the most stable decomposition reaction and a reaction enthalpy of each reaction. Table 15 also provides a molar fraction between the abundant amount of Fe₂O₃ and each of the MAX phase compounds. Further, Table 15 provides a penalty point (e.g. PP21) regarding the molar fraction, where PP21 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of Fe₂O₃. PP21 is calculated by dividing the molar fraction between the abundant amount of Fe₂O₃ and TiN by the molar fraction between the abundant amount of Fe₂O₃ and each MAX phase compound. For example, since the molar fraction between the abundant amount of Fe₂O₃ and Nb2SnC is 1.667, PP21 thus equals 0.835/1.667, which is around 0.50.

[0060] Table 15 further provides a reaction enthalpy (eV/atom) of the reaction between the abundant amount of Fe₂O₃ and each MAX phase compound. Table 15 also provides another penalty point (e.g. PP22) regarding the reaction enthalpy of the reaction, where PP22 of 1.00 is assigned to the reference reaction between TiN and the abundant amount of Fe₂O₃ (i.e. -0.212 eV/atom). PP22 is calculated by dividing the reaction enthalpy between the abundant amount of Fez Ch and each MAX phase compound by that between the abundant amount of Fe₂O₃ and TiN. For example, since the reaction enthalpy between the abundant amount of Fe₂O₃ and Nb₂SnC is -0.347, PP22 thus equals - 0.347/-0.212, which is about 1.64.

Table 15. Information of the most stable decomposition reaction between each of the MAX phase compounds listed in Table 12 and an abundant amount of Fe₂O₃.

[0061] Based on the information provided from Tables 13 to 15, a sum of the penalty points QT>P’ = PP17 + PP18 + PP19 + PP20 + PP21 + PP22) is calculated for each MAX phase compound and provided in Table 16. The sum of penalty points for TiN is 6.00 (i.e. ^PP™’ = 6.00).

[0062] Table 16 further provides the molecular weight (MW) of each MAX phase compound, a sum of penalty points of each MAX phase compound per MW (ΣPP’ per MW), and a percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP’ per MW. ΣPPTIN’ per MW is around 0.097. To calculate the percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP’ per MW, ^PPUN’ per MW is divided by the ΣPP’ per MW of each MAX phase compound. For example, since the ΣPP’ per MW for Nb2SnC is around 0.017, the percentage of improvement of Nb2SnC when compared to TiN thus equals 0.097/0.017, which is around 568.6%.

[0063] Table 16 also provides the density of each MAX phase compound, a sum of penalty points of each MAX phase compound per volume (ΣPP’ per volume), and a percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP’ per volume. ΣPPTIN’ per volume equals ( ΣPPUN’ per MW)*(the density of TiN), i.e. 0.097*5.34, which is around 0.518. To calculate the percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP’ per volume, ^PPUN’ per volume is divided by the ΣPP’ per volume of each MAX phase compound. For example, since the ΣPP’ per volume for Nb₂SnC is around 0.139, the percentage of improvement of Nb2SnC when compared to TiN thus equals 0.518/0.139, which is around 373.6%.

[0064] In addition, Table 16 provides a total percentage of improvement of each MAX phase compound when compared to TiN, which represents a sum of the percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP’ per MW plus the percentage of improvement of each MAX phase compound when compared to TiN based on the ΣPP’ per volume.

[0065] Further, Table 16 provides a percentage difference of improvement of each MAX phase compound when compared to TiN. As shown in Table 16, the total percentage of improvement for TiN is 200.0%. As such, the percentage difference of improvement of each MAX phase compound when compared to TiN equals a total percentage of improvement of each MAX phase compound minus the total percentage of improvement of TiN (i.e. 200.0%). For example, since the total percentage of improvement of Nb₂SnC is around 942.3% (i.e. 568.6% + 373.6%), the percentage difference of improvement of Nb2SnC when compared to TiN thus equals 942.3% - 200.00%, which is 742.3%. As shown in Table 16, these MAX phase compounds all exhibit a percentage difference of improvement greater than 100%. This indicates that these MAX phase compounds may be comparably more effective than TiN in terms of interfacial stabilities when applied to a metal substrate (e.g. stainless steel).

Table 16. A summary of improvement of each MAX phase compound in terms of interfacial stability when compared to that of TiN.

[0066] In view of Tables 12 and 16, Nb₂SnC appears to be the best MAX phase compound which not only exhibits good resistance against the acidic species (such as H3O, HF, SO3, or HC1) in an acidic environment of an electrochemical device but also exhibits good interfacial stability when applied to a metal substrate (e.g. stainless steel). Apart from Nb₂SnC, MAX phase compounds, such as Ti₄AlN₃, Ti₃SnC₂, Nb₂PC, Nb₄AlC₃, V₂PC, Ti₃SiC₂, Zr₂SnC, Zr₂SC, Ti₃AlC₂, Ti₂SnC, Ti₂SC, or Nb₂AlC, may also be suitable to be used as protective materials for metal substrates, especially metal components generally made of stainless steel in an electrochemical device.

[0067] Therefore, to increase the anti-corrosive resistance of a metal substrate against these acidic species, at least one surface coating layer of a protective coating material may be applied to at least one surface of the metal substrate. The metal substrate may be made of stainless steel. The metal substrate may also be made of Ti-based or Al-based alloys. The protective coating material may be a MAX phase material. The MAX phase material is a MAX phase compound, which may include, but not limited to, Nb₂SnC, Ti₄AlN₃, Ti₃SnC₂, NbzPC, and Nb₄AlC₃, V₂PC, Ti₃SiC₂, Zr₂SnC, Zr₂SC, Ti3AlC₂, Ti₂SnC, Ti₂SC, Nb₂AlC, or a combination thereof. Upon disposition of a MAX phase coating material onto the at least one surface of the metal substrate, the MAX phase coating material may form stable interfaces with oxides species (e.g. CT₂O₃, Fe₂C>3, or NiO) that are commonly present at the surface of the metal substrate. Further, the protective coating material may be mixed with other conductive and anti-corrosive compounds, including, but not limited to, nitrides (e g. chromium nitride (CrNx, 0.5 < x < 2), aluminum nitride (AIN), or titanium nitride (TiNx, 0.3 < x < 2)), carbides, and/or oxides (e g. titanium oxide (TiOx, 0.5 < x < 2), niobium oxide (NbOx, 1 < x < 3), or magnesium titanium oxide (MgTi₂O5-x, 0 < x < 5)), to enhance the conductivity and/or anti-corrosion resistance of the metal substrate.

[0068] A MAX phase compound may be prepared via a solid-state method, a solution precipitation-based method, or a sol-gel process. Specifically, for nitride-based MAX phase compounds, solid-state precursors of A_xB_yOz (A and B are metal elements) may be treated with N₂, NH3, or both, at temperatures varying from about 250 to 2,000 °C to yield a ternary nitride compound, AxByNz. For carbide-based MAX phase compounds, metal elements or metal hydrides may be mixed with carbon powders. The resulting powders may be pelletized and heat-treated at temperatures varying from about 400 to 2,000 °C to yield a ternary carbide compound A_xB_yCz. For the solution precipitation-based method, two different metallic complexes (e.g. metal chlorides, metal nitrates, or metal sulfates) may be dissolved in a solvent (e.g. water, acetonitrile, acetone, ethanol, or isopropyl alcohol), followed by adding another chemical molecule, such as ethanolamine, to the reaction mixture to yield a precipitate. The resulting reaction mixture may be filtered and dried and heated in a reducing environment (e.g. under N2 orNFE) to afford a ternary MAX phase compound. For the sol-gel process, metal alkoxides may be used as a precursor to prepare a MAX phase compounds.

[0069] To deposit a protective coating layer of a MAX phase material to the at least one surface of the metal substrate, several techniques may be employed. For example, physical vapor deposition (PVD) is one of the most widely used techniques for the deposition of MAX phase thin films onto a substrate, including a metal substrate. Depending on the composition of a MAX phase compound, different variations of PVD, including magnetron sputtering, high-power impulse magnetron sputtering (HiPIMS), or pulsed laser deposition, may be used. Temperatures varying from about 400 °C to 1,100 °C may be required for the deposition. In addition, chemical vapor deposition techniques (CVD), such as atomic layer deposition, plasma-enhanced CVD or laser CVD, may also be used to deposit MAX phase thin films onto the substrate. Further, electrospun precursor fibers containing target metals may be thermally treated, where the addition of organic molecules, such as methylated polyuria, may help control the morphology of the defined fibers. Viscous solutions including the target metals may be dried into a glass or glassy film, and a processing step, such as spray coating, spinning, printing, or templating, can be used to deposit the precursor onto the substrate.

[0070] An interfacial contact resistance between a protective coating layer and a metal substrate may be less than 50 Ohm cm², and in other embodiments, less than 0.01 Ohm cm² during a normal operation of an electrochemical device. An electrical conductivity value of the protective coating layer may be at least 0.1 S cm'¹, and in other embodiments, greater than 100 S cm'¹. Each protective coating layer may have a thickness of 5 nm to 1 mm, typically in a range of 50 nm and 500 pm, depending on a target conductivity. [0071] Next, exemplary embodiments will be discussed in a fuel cell system. It is noted that the protection methods applied to the fuel cell system as described herein may also be applicable to metal components in other electrochemical devices, such as metal components in an electrolyzer system.

[0072] Figure 3A is a schematic cross-sectional view of a fuel cell. Figure 3B is a schematic perspective view of components of the fuel cell shown in Figure 3 A. Figure 3 A also generally depicts the reactants and products of the operation of the fuel cell. The fuel cell 30 may be a proton-exchange membrane (PEM) fuel cell. As shown in Figure 3 A, the fuel cell 30 includes a PEM 32, a first catalyst layer 34 and a second catalyst layer 36. The PEM 32 is situated between the first and second catalyst layers, 34 and 36. The fuel cell 30 further includes a first gas diffusion layer (GDL) 38 surrounds the first catalyst layer 34, and a second GDL 40 surrounds the second catalyst layer 36. The fuel cell 30 also includes a first bipolar plate 42 and a second bipolar plate 44. The first and second bipolar plates, 42 and 44, are positioned at opposite ends of the fuel cell 30 and surround the first and second GDLs, 38 and 40, respectively. The first and second bipolar plates, 42 and 44, are typically formed of a metal substrate, such as steel or stainless steel, and have at least one surface.

[0073] The first and second bipolar plates, 42 and 44, may provide structural support and conductivity, and may assist in supplying fuel and oxidants (air) in the fuel cell 30. The first and second bipolar plates, 42 and 44, may also assist in removal of reaction products or byproducts from the fuel cell 30. As shown in Figure 3B, the first bipolar plate 42 includes a flow passage 46. The second bipolar plate 44 also includes a flow passage (not shown). The flow passages are configured to assist in supplying fuel and/or removing by-products in the fuel cell 13.

[0074] Referring to Figure 3A, to protect a fuel cell metal component (e.g. a bipolar plate) from acidic corrosion in a fuel cell environment, at least one surface coating layer of a protecting coating material may be applied to at least one surface of the component. The component may be made of stainless steel. The component may also be made of Ti-based or Al-based alloys. The protective coating material may be a MAX phase material. The MAX phase material is a MAX phase compound, which may include, but not limited to, Nb2SnC, Ti4AlN3, Ti3SnC2, Nb2PC, and Nb4AlC3, V2PC, Ti3SiC2, ZnSnC, ZnSC, TEAIC2, Ti2SnC, Ti2SC, Nb2AlC, or a combination thereof. The protective coating material may also be mixed with other conductive and anti -corrosive compounds, including, but not limited to, nitrides (e.g. chromium nitride (CrNx, 0.5 < x < 2), aluminum nitride (AIN), or titanium nitride (TiNx, 0.3 < x < 2)), carbides, and/or oxides (e.g. titanium oxide (TiOx, 0.5 < x < 2), niobium oxide (NbOx, 1 < x < 3), or magnesium titanium oxide (MgTi2Os-x, 0 < x < 5)), to enhance the conductivity and/or anti -corrosion resistance of the component.

[0075] In some other embodiments, when more than one surface coating layer of the protecting coating material are applied to one surface of the component, each surface coating layer may include a different coating material to achieve a total targeting resistance capability. For example, one of the surface coating layers has a first MAX phase material including a first MAX phase compound, and another one of the surface coating layers has a second MAX phase material including a second MAX phase compound different from the first MAX phase compound.

[0076] In addition, an interfacial contact resistance between a protective coating layer and the fuel cell metal component may be less than 50 Ohm cm², and in other embodiments, less than 0.01 Ohm cm² during an operation of the fuel cell. An electrical conductivity value of a protective coating layer may be at least 0.1 S cm'¹, and in some embodiments, greater than 100 S cm'¹. Each protective coating layer may have a thickness of 5 nm to 1 mm, typically in a range of 50 nm and 500 pm, depending on a target conductivity.

[0077] Still referring to Figure 3A, each of the first and second catalyst layers may include a catalyst support layer which supports a fuel cell catalyst (e.g. Pt or Pt-M alloys, M being a metal element different from Pt). The catalyst support layer includes a catalyst support material. To protect the catalyst layer from acidic corrosion in a fuel cell environment, a MAX phase material may be used as a catalyst support material. The MAX phase material is a MAX phase compound, which may include, but not limited to, Nb2SnC, Ti4AlN3, Ti3SnC2, Nb2PC, and Nb4AlC3, V2PC, Ti3SiC2, ZnSnC, ZnSC, Ti3AlC2, Ti2SnC, Ti2SC, Nb2AlC, or a combination thereof. The MAX phase material may exhibit catalytic activity depending on its composition. The MAX phase material may also be mixed with other conductive and anti-corrosive compounds, including, but not limited to nitrides (e.g. chromium nitride (CrNx, 0.5 < x < 2), aluminum nitride (AIN), or titanium nitride (TiNx, 0.3 < x < 2)), carbides, and/or oxides (e.g. titanium oxide (TiOx, 0.5 < x < 2), niobium oxide (NbOx, 1 < x < 3), or magnesium titanium oxide (MgTi2Os-x, 0 < x < 5)), to enhance the conductivity and/or anti -corrosion resistance of the catalyst layers. [0078] In one or more embodiments, the catalyst support layer may include a carbon material and/or an oxide material. The oxide material may be TiCh, SnCh, or a combination thereof. In some other embodiments, the catalyst support material may be mixed with a catalyst-containing precursor in a solution. The catalyst-containing precursor may be an H-Pt-Cl complex. The solution may be heat treated to form a catalyst/MAX phase catalyst support material, such as a Pt/MAX phase material. The catalyst support material may further contain other metal elements other than Pt. The other metal elements may be transition metals or noble metals. The transition metals may include, but not limited to, Co, Ni, Fe and/or Ti. The noble metals may include Ru, Pd, Ag and/or Au.

[0079] 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 specification are words of description rather than limitation, and it is understood that various changes can be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments can be combined to form further embodiments of the present disclosure that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics can be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes can include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, to the extent any embodiments are described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics, these embodiments are not outside the scope of the disclosure and can be desirable for particular applications.

Claims

WHAT IS CLAIMED IS:

1. A component of an electrochemical device comprising: a substrate; and a MAX phase material mixed with a nitride compound and/or an oxide compound, the MAX phase material being a MAX phase compound with a general formula of Mn+i AXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N.

2. The component of claim 1, wherein the MAX phase compound is Nb2SnC, Ti₄AlN₃, Ti₃SnC₂, Nb₂PC, and Nb₄AlC₃, V₂PC, Ti₃SiC₂, Zr₂SnC, Zr₂SC, Ti₃AlC₂, Ti₂SnC, Ti₂SC, Nb₂AlC, or a combination thereof.

3. The component of claim 1, wherein the oxide compound is a titanium oxide (TiOx, 0.5 < x < 2), a niobium oxide (NbOx, 1 < x < 3), or a magnesium titanium oxide (MgTLOs-x, 0 < x < 5).

4. A component of an electrochemical device comprising: a substrate made of stainless steel and having at least one surface; and at least one surface coating layer on each of the at least one surface, the at least one surface coating layer including a MAX phase material mixed with a nitride compound and/or an oxide compound, the MAX phase material being a MAX phase compound with a general formula of Mn+iAXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N.

5. The component of claim 4, wherein the MAX phase compound is Nb₄AlC₃, Ti₄AlN₃, V₄A1C₃, Nb₂SnC, Ti₃SnC₂, Zr₂SC, Ti₂SnC, Zr₂SnC, Nb₂PC, Nb₂AlC, Ti₃SiC₂, Ti₃AlC₂, Ti₂SC, V₂PC, or a combination thereof.

6. The component of claim 4, wherein the oxide compound is a titanium oxide (TiOx, 0.5 < x < 2), a niobium oxide (NbOx, 1 < x < 3), or a magnesium titanium oxide (MgTi2Os-x, 0 < x < 5).

7. The component of claim 4, wherein an interfacial contact resistance between the at least one surface coating layer and the substrate is less than 50 Ohm cm².

8. The component of claim 4, wherein an electrical conductivity of the at least one surface coating layer is at least 0.1 S cm'¹.

9. The component of claim 4, wherein each of the at least one surface coating layer has a thickness of 5 nm to 1 mm.

10. The component of claim 4, wherein one of the at least one surface coating layer has a first MAX phase material including a first MAX phase compound, and another one of the at least one surface coating layer has a second MAX phase material including a second MAX phase compound different from the first MAX phase compound.

11. A catalyst layer of an electrochemical device comprising: a substrate; and a MAX phase material, the MAX phase material being a MAX phase compound with a general formula of Mn+iAXn, where n = 1 to 4, M is an early transition metal, A is an A-group element (e.g. IIIA, IVA, group 13, or group 14 element), and X is C or N.

12. The catalyst layer of claim 11, wherein the MAX phase compound is Nb2SnC, Ti₄AlN₃, Ti₃SnC₂, Nb₂PC, and Nb₄AlC₃, V2PC, Ti₃SiC₂, ZnSnC, Zr₂SC, Ti₃AlC₂, Ti₂SnC, Ti₂SC, Nb2AlC, or a combination thereof.

13. The catalyst layer of claim 11, wherein the MAX phase material is mixed with a nitride compound and/or an oxide compound.

14. The catalyst layer of claim 13, wherein the oxide compound is a titanium oxide (TiOx, 0.5 < x < 2), a niobium oxide (NbOx, 1 < x < 3), or a magnesium titanium oxide (MgTi2Os-x, 0 < x < 5).

15. The catalyst layer of claim 11, wherein the substrate is a catalyst support layer which supports a fuel cell catalyst.

16. The catalyst layer of claim 15, wherein the catalyst support layer includes a carbon material and/or an oxide material.

17. The catalyst layer of claim 16, wherein the oxide material is TiCh, SnCh, or a combination thereof.

18. The catalyst layer of claim 15, wherein the catalyst support layer includes metal elements other than Pt.

19. The catalyst layer of claim 18, wherein the metal elements are Co, Ni, Fe and/or Ti.

20. The catalyst layer of claim 19, wherein the metal elements are Ru, Pd, Ag, and/or Au.