Conductive anti-corrosion magnesium titanium oxide material

Abstract

The present invention relates to a conductive and corrosion-resistant magnesium titanium oxide material. A fuel cell bipolar plate (BPP) includes a metal substrate having a body portion and a surface portion, which comprises a corrosion-resistant conductive material having oxygen vacancies with formula (I): wherein δ is any number from 0 to 3 representing oxygen vacancies, optionally including a fractional part, and the material has a conductivity of about 2 - 10 S / m at room temperature in the ambient environment.

Description

Technical Field

[0001] The present invention relates to a corrosion-resistant conductive magnesium titanium oxide material having oxygen vacancies. Background Art

[0002] For thousands of years, metals have been widely used materials. Various methods have been developed to protect metals and prevent them from corroding or disintegrating into oxides, hydroxides, sulfates, and other salts. In some industrial applications, metals are particularly prone to corrosion due to the aggressive working environment. Non-limiting examples can be metal components of fuel cells, such as bipolar plates (BPPs) or catalyst support materials for fuel cells. Additionally, certain components such as BPPs not only need to have sufficient chemical inertness to resist degradation in the highly corrosive environment of fuel cells but also need to be conductive to facilitate electron transfer in the oxygen reduction reaction of fuel cells. Finding materials that meet these two requirements has become a challenge. Summary of the Invention

[0003] According to one embodiment, a fuel cell BPP is disclosed. The BPP includes a metal substrate having a body portion and a surface portion that contains a corrosion-resistant conductive material having oxygen vacancies of formula (I):

[0004]

[0005] where δ is any number from 0 - 3, optionally including a fractional part, representing oxygen vacancies. The material may have a conductivity of about 2 - 10 S / m at room temperature in the ambient environment. The static corrosion current density of the bipolar plate may be less than about 1 μA cm at a pH of 2 and a temperature of about 0 - 80 °C. -2 . The Mg / Ti ratio of the material can be a number in the range of 0.3 - 0.6. The material may have an activation energy of about 0.13 eV in the temperature range of 25 °C - 80 °C. δ may include a fractional part. The material may be non-stoichiometric. The material may have a crystalline structure. The structure may contain at least one Ti atom having five bonds with oxygen atoms.

[0006] In an alternative embodiment, a proton exchange membrane fuel cell BPP is disclosed. The BPP may include a metal substrate having a body portion and a surface portion, one of which contains a corrosion-resistant conductive material having oxygen vacancies of formula (I):

[0007]

[0008] where δ is any number from 0 - 3, optionally including a fractional part and representing oxygen vacancies. The material may have about 33 mol% of MgO and 66 mol% of TiO with TiO 2The nominal chemical composition of the mixture. The Mg / Ti ratio can be a number in the range of 0.3 - 0.6. δ can include a fractional part. The static corrosion current density of the bipolar plate can be less than about 1 μA cm at a temperature of about 0 - 80 °C when the pH is 2 -2 The material can have an activation energy of about 0.13 eV in the temperature range of 25 °C - 80 °C. The body portion can comprise the material. The material can be non-stoichiometric.

[0009] In yet another embodiment, a fuel cell is disclosed. The fuel cell can include a BPP having a metal substrate with a body portion and a surface portion that comprises a corrosion-resistant conductive material having oxygen vacancies of formula (I):

[0010]

[0011] where δ is any number from 0 - 3 representing oxygen vacancies, optionally including a fractional part. The material can have a conductivity of about 2 - 10 S / m at room temperature in the ambient environment. The static corrosion current density of the bipolar plate can be less than about 1 μA cm at a temperature of about 0 - 80 °C when the pH is 2 -2 The Mg / Ti ratio of the material can be a number in the range of 0.3 - 0.6. The fuel cell can be an anion exchange membrane fuel cell (AEMFC). δ can include a fractional part. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Depicts a schematic composition of a proton exchange membrane fuel cell including a bipolar plate according to one or more embodiments;

[0013] Figure 2 Shows a perspective view of a non-limiting example of a bipolar plate having a body portion and a surface portion comprising a corrosion-resistant and conductive material according to one or more embodiments;

[0014] Figure 3 Shows a non-limiting example of a synthetic pellet sample of the disclosed material;

[0015] Figure 4A and 4B respectively show the MgTi indicating insulating behavior 2 O 5 structure and the MgTi indicating conductive behavior 2 O 4.92 density of states (DOS);

[0016] Figures 5A to 5E Shows (110)MgTi 2 O 5 、(110)MgTi2 O 5-δ ,(101)TiO 2 (anatase),(110)TiO 2 (rutile),and the chemical structures of (001)TiO;

[0017] Figure 6 shows MgTi 2 O 5-δ Arrhenius plot of the electrical conductivity from 25 °C to 80 °C;

[0018] Figure 7 shows the as-synthesized pristine MgTi 2 O 5-δ ,MgTi 2 O 5-δ and TiO 2 Ti2 p X-ray photoelectron spectroscopy (XPS) spectra;

[0019] Figure 8 is the as-synthesized MgTi 2 O 5-δ vs. MgTi 2 O 5 X-ray diffraction (XRD) pattern;

[0020] Figures 9A to 9C are the as-synthesized MgTi 2 O 5-δ ,MgTi 2 O 5-δ and MgTi 2 O 5-δ after annealing in air at 1000 °C;

[0021] Figure 10 shows the comparison plot of the corrosion current density of pristine MgTi 2 O 5-δ ,carbon paper, and polished stainless steel (SS) 316;

[0022] Figure 11A and 11B respectively show the schematic diagrams of MgTi 2 O 5-δ as a catalyst support material, where the catalyst is deposited in the form of islands or in a core-shell structure.

[0023] Figure 12A and 12B are the sputtered MgTi 2 O 5-δScanning electron microscope (SEM) cross-sectional image of Pt on a non-limiting example of a pellet;

[0024] Figures 13A to 13F Shows the interface formed by first-principles density functional theory (DFT) between MgTi 2 O 5-δ and the Pt surface before and after DFT relaxation; and

[0025] Figure 14 Shows a schematic of various Pt particles / facets attached to the MgTi 2 O 5-δ oxide support. DETAILED DESCRIPTION

[0026] Embodiments of the present disclosure are described below. However, it should be understood that the disclosed embodiments are merely examples and that other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Thus, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a representative basis for teaching one skilled in the art to use the embodiments in various ways. As will be understood by those of ordinary skill in the art, the various features shown and described with reference to any one figure may be combined with features shown in one or more other figures to produce embodiments not explicitly shown or described. Combinations of the shown features provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for a particular application or implementation.

[0027] All numerical quantities representing dimensions or material properties in this specification should be understood to be modified by the word "about" when describing the broadest scope of the present disclosure, unless expressly indicated otherwise.

[0028] The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation in this document and, as necessary, to normal grammatical variations of the originally defined abbreviation. Unless expressly stated to the contrary, measurements of properties are determined by the same techniques as those cited previously or subsequently for the same property.

[0029] The terms "substantially" or "about" may be used herein to describe the disclosed or claimed embodiments. The terms "substantially" or "about" may modify a value or relative property disclosed or claimed in the present disclosure. In such cases, "substantially" or "about" may mean that the value or relative property being modified is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the stated value or relative property.

[0030] A description of a group or class of materials suitable for a given purpose in connection with one or more embodiments means that a mixture of any two or more members of the group or class is suitable. A description of a component in chemical terms means the component as added to any combination listed in the specification and does not necessarily preclude chemical interaction between the components of the mixture once mixed. The first definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation in this document and, with necessary modifications, to normal grammatical variations of the initially defined abbreviation. Unless expressly stated to the contrary, measurements of properties are determined by the same techniques as those cited previously or subsequently for the same property.

[0031] Metals are a widely used class of materials in many industries, including automotive, construction, household appliances, tools, piping, railway tracks, coinage, etc. Metals have been used for thousands of years and remain the material of choice for certain applications due to their properties such as strength and resilience. However, for many applications in which metals are used, corrosion of the metals is a major source of fatigue and limited lifespan.

[0032] Corrosion is a natural process that converts refined metals into chemically more stable forms, such as the (one or more) oxides, (one or more) hydroxides, (one or more) sulfides, and / or other salts of the metal. The conversion is manifested as the gradual destruction of the metallic material, which is caused by the electrochemical oxidation of the metal reacting with oxidants such as oxygen or sulfates. Corrosion can be caused by exposing the metal substrate to moisture in the air, solutions with a relatively low pH, various chemicals such as acids, microorganisms, elevated temperatures, and / or other factors. Especially in acidic environments, corrosion begins at the interface between the bulk metallic material (e.g., steel) and the solution (e.g., ions dissolved in water or the water surface layer that react to degrade the bulk material).

[0033] Many efforts have been made to prevent or slow down the corrosion of metals. For example, various types of coatings have been developed. Examples of coatings include applied coatings such as paints, platings, enamels; reactive coatings that contain corrosion inhibitors such as chromates, phosphates, conductive polymers, surfactant-like chemicals designed to inhibit the electrochemical reaction between the environment and the metal substrate; anodized surfaces, or biofilm coatings. Other corrosion prevention methods include controlled permeability frameworks, cathodic protection, or anodic protection.

[0034] However, the most popular solution to the corrosion problem remains to reinforce vulnerable metal surfaces with coatings. Thus, most corrosion-resistant surfaces include one or more chemically inert coatings or protective layers, which can slow down and / or at least partially prevent corrosion from occurring. There remains a challenge to find materials with inherent corrosion resistance properties that are also environmentally friendly, economical, and have excellent performance characteristics.

[0035] In addition, some applications are highly vulnerable to corrosion due to their environmental factors. Non-limiting examples of such applications are proton exchange membrane fuel cells (PEMFCs). PEMFCs are an environmentally friendly alternative to internal combustion engines for various vehicles such as cars and buses. PEMFCs typically feature relatively high efficiency and power density. A very attractive feature of PEMFC engines is zero carbon emissions, provided that hydrogen fuel is obtained in an environmentally friendly manner. In addition to being a green engine, PEMFCs can also be used in other applications such as stationary and portable power supplies.

[0036] The operating environment of PEMFCs themselves causes corrosion for various reasons. For example, there is a low voltage between the start-up and shut-down of PEMFCs, PEMFCs have a strongly acidic environment, fluoride ions are released from the polymer membrane during the operation of PEMFCs, H 2 and O 2 both exist at the anode (which results in a high cathode potential that causes cathode corrosion), fuel crossover of hydrogen or oxygen from the anode to the cathode, or vice versa, and so on. Therefore, PEMFCs require durable components that can withstand the above conditions.

[0037] Figure 1 A non-limiting example of a PEMFC is depicted in. The core component of the PEMFC 10 that helps generate the electrochemical reactions required to separate electrons is the membrane electrode assembly (MEA) 12. The MEA 12 includes sub-components such as electrodes, catalysts, and polymer electrolyte membranes. In addition to the MEA 12, the PEMFC 10 typically also includes other components such as current collectors 14, gas diffusion layer(s) 16, gaskets 18, and bipolar plate(s) 20.

[0038] The bipolar plate or BPP 20 is implemented in a PEMFC stack to distribute gases, collect current, and separate the individual cells in the stack from each other. The BPP 20 also provides additional functions such as removing reaction products and water and thermal management within the PEMFC 10. The BPP 20 is also a relatively expensive component and is a common cause of degradation in the PEMFC system. For example, the BPP can constitute about 60 - 80% of the stack weight, about 50% of the stack volume, and about 25 - 45% of the stack cost. To keep the cost low, the BPP 20 is typically made of metal, such as steel, like stainless steel. Alternative materials such as aluminum or titanium can be used. Since metal plates are prone to corrosion within the PEMFC system, efforts have been made to prevent corrosion.

[0039] In addition, in the PEMFC 10, the BPP 20 also presents another material challenge because the BPP 20 also needs to be conductive to facilitate electron transfer for the oxygen reduction reaction. Thus, the BPP 20 material needs to be conductive but chemically inert to reactions with the ions present in the PEMFC 10 environment.

[0040] Typically, the BPP metal surface contains coatings such as graphitic-like coatings or protective oxide or nitride coatings to increase the corrosion resistance of the BPP 20. The surface of the BPP 20 can thus contain elements such as Fe, Cr, Ni, Mo, Mn, Si, P, C, S, F, or combinations thereof. Alternative coatings include Ti alloys, doped TiO x 、Cr 2 O 3 、TiO 2 、TiN, CrN, or ZrN. However, in an erosive corrosion environment such as in the PEMFC 10, where coatings are more likely to degrade faster than in other applications, there is still a need for a coating or material that is economically viable, corrosion-resistant, protective against acids such as HF at the PEMFC operating temperature of about 80 °C, conductive, and capable of forming a coherent interface (i.e., small interfacial contact resistance) with the metal substrate simultaneously.

[0041] The materials disclosed herein solve one or more of the above problems and / or provide the benefits described herein. It has surprisingly been found that the disclosed materials provide corrosion-resistant and conductive properties for substrates such as BPP metal substrates. The materials comprise multiple or a series of Mg-Ti compounds with different oxygen vacancy contents, or in other words, Mg-Ti compounds with multiple oxygen-deficient stoichiometries.

[0042] Non-limiting examples of the BPP 20 are shown in Figure 2Among them, BPP 20 represents a non-limiting example of a substrate having a solid body or body portion 22 and a surface portion 24. The body portion 22 can be formed of a metal such as steel, stainless steel, aluminum, copper, an alloy of two or more metals, etc., or a combination thereof. Alternatively, the body portion 22 can be formed of a composite material such as a carbon-carbon composite material or a carbon-polymer composite material. Or, the body portion 22 can be made of graphite or other carbon allotropes. In another embodiment, the body portion 22 can also comprise the disclosed materials.

[0043] The surface portion 24 can comprise a corrosion-resistant, chemically inert, electrically conductive and thermodynamically stable material disclosed herein. The entire region of the surface portion 24 can comprise the material. Alternatively, the surface portion 24 can comprise one or more sub-portions without the material. In one exemplary embodiment, the entire surface portion 24 can comprise the material so as to protect the entire BPP 20 from corrosion. In other applications such as non-BPP applications, only a small portion of the surface portion 24 can comprise the material, such as less than about ½, ¼, 1 / 8, 1 / 16, 1 / 32, etc. of the surface portion can comprise the material.

[0044] The surface portion 24, the body portion 22, or both may include one or more layers of the disclosed materials. The thickness of the material on the surface portion 24 can be adjusted according to the needs of a particular application. Non-limiting examples of the thickness of the material layer can be about 0.1 - 0.8 µm, 0.2 - 0.6 µm, or 0.3 - 0.5 µm. Alternatively, the material can be layered to form a relatively thick deposit greater than 1 µm on the surface portion 24, such as about or at least about 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, 4.0, 4.25, 4.5, 4.75, 5.0, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250 µm or about 1.25, 1.5, 1.75, 2.0, 2.25, 2.5, 2.75, 3.0, 3.25, 3.5, 3.75, 4.0, 4.25, 4.5, 4.75, 5.0, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 200, 250, 300, 350, 400, 450, or 500 nm. The material can form one or more layers or multiple layers on the body portion 22. The material can form 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more layers on the body portion 22. Each layer can have a thickness within the nanoscale or microscale described herein relative to the thickness of the surface portion 24.

[0045] The disclosed material is a Mg-Ti-O based material. The disclosed material has the formula (I):

[0046]

[0047] wherein

[0048] δ is any number from 0 to 3, optionally including a fractional part such as tenths and / or hundredths, and represents an oxygen vacancy. δ can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0. δ can be any number from 0 to 3, including tenths, hundredths, or both. δ can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.40, 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.50, 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.80, 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, 1.21, 1.22, 1.23, 1.24, 1.25, 1.26, 1.27, 1.28, 1.29, 1.30, 1.31, 1.32, 1.33, 1.34, 1.35, 1.36, 1.37, 1.38, 1.39, 1.40, 1.41, 1.42, 1.43, 1.44, 1.45, 1.46, 1.47, 1.48, 1.49, 1.50, 1.51, 1.52, 1.53, 1.54, 1.55, 1.56, 1.57, 1.58, 1.59, 1.60, 1.61, 1.62, 1.63, 1.64, 1.65, 1.66, 1.67, 1.68, 1.69, 1.70, 1.71, 1.72, 1.73, 1.74, 1.75, 1.76, 1.77, 1.78, 1.79, 1.80, 1.81, 1.82, 1.83, 1.84, 1.85, 1.86, 1.87, 1.88, 1.89, 1.90, 1.91, 1.92, 1.93, 1.94, 1.95, 1.96, 1.97, 1.98, 1.99, 2.0, 2.01, 2.02, 2.03, 2.04, 2.05, 2.06, 2.07, 2.08, 2.09, 2.1, 2.11, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21, 2.22, 2.23, 2.24, 2.25, 2.26, 2.27, 2.28, 2.29, 2.30, 2.31, 2.32, 2.33, 2.34, 2.35, 2.36, 2.37, 2.38, 2.39, 2.40, 2.41, 2.42, 2.43, 2.44, 2.45, 2.46, 2.47, 2.48, 2.49, 2.50, 2.51, 2.52, 2.53, 2.54, 2.55, 2.56, 2.57, 2.58, 2.59, 2.60, 2.61, 2.62, 2.63, 2.64, 2.65, 2.66, 2.67, 2.68, 2.69, 2.70, 2.71, 2.72, 2.73, 2.74, 2.75, 2.76, 2.77, 2.78, 2.79, 2.80, 2.81, 2.82, 2.83, 2.84, 2.85, 2.86, 2.87, 2.88, 2.89, 2.90, 2.91, 2.92, 2.93, 2.94, 2.95, 2.96, 2.97, 2.98, 2.99 or 3.00..

[0049] δ can be a range that includes any of the above numbers while excluding at least one of the numbers mentioned above. For example, δ can be equal to 0.1 - 3.0, excluding 1 and 2. In an alternative instance, δ can include one or more ranges of 0.1 - 0.9, 1.1 - 1.9, or 2.1 - 2.9. In yet another non - limiting instance, δ can include one or more ranges of 0.01 - 0.99, 1.10 - 1.99, or 2.10 - 2.99.

[0050] In one or more embodiments, the oxygen vacancies within the material contribute to the beneficial properties of the material. Accordingly, the oxygen vacancies are intentionally formed and retained, and processes that would eliminate the presence of oxygen vacancies can be avoided or excluded during material synthesis and / or use.

[0051] The characteristics of the oxygen vacancies in the material can lie in that: the number of oxygen atoms present in the material is less than the number expected in the lattice of the parent material. Oxygen vacancies are typically formed by removing oxygen from oxygen compounds, for example by annealing in a reducing atmosphere such as N 2 , Ar, etc. In another embodiment, the annealing can be carried out in a vacuum furnace. The oxygen vacancies can render the material non-stoichiometric or deviate from stoichiometry such that the elemental composition of the material may not be represented by a ratio of well-defined natural numbers. However, the material can be stoichiometric.

[0052] In some applications, oxygen vacancies may be considered as undesirable defects that affect the structural, electrical, optical, dissociation and reduction properties or other properties in a manner not suitable for various applications. On the contrary, due to the presence of oxygen vacancies, the materials disclosed herein have desirable properties. Although the base or parent compound and the material with oxygen vacancies can to some extent have common morphologies, structures or lattices, their properties can be significantly different. This is the case for the disclosed materials with oxygen-deficient stoichiometry. The material has a crystalline structure similar to the parent MgTi 2 O 5 phase. However, due to oxygen deficiency, even the crystalline structure is different. For example, the lattice of the disclosed material can contain additional bonds or lack bonds in the space where the paternal phase contains bonds. Examples of the structural differences between the parent and the disclosed materials can be seen in Figure 5. In Figure 5, the large dark gray circles represent Ti atoms, the large light gray circles represent Mg, the small black circles represent O atoms, and the small light gray circles represent H atoms.

[0053] As can be seen in Figure 5, the lattice of the parent MgTi 2 O 5 phase contains Ti atoms and Mg atoms, each Ti atom having exactly four bonds with oxygen atoms and each Mg atom having three or five bonds with oxygen atoms. On the contrary, the structural lattice of MgTi 2 O 5-δ contains at least one Ti atom having a bond with five oxygen atoms and / or at least one Mg having only four bonds with oxygen atoms.

[0054] Without limiting the present disclosure to a single theory, it is believed that due to the presence of oxygen vacancies, the disclosed materials have properties very different from those of the parent phase, such as conductivity, because the oxygen vacancies act as the main charge carriers for conduction in the material. Additional differences can be observed in their physical appearance. While the parent structure is white, the disclosed materials have a black-to-gray appearance with a dark blue tint, which indicates oxygen vacancies. In Figure 3Examples of the synthesized materials can be seen in, and color differences, which indicate oxygen vacancies, can be seen in FIGS. 9A-9C.

[0055] The disclosed materials have good electrical conductivity. The MgTi 2 O 5-δ materials can have a conductivity of about 1-15, 1.5-12, or 2-10 S / m at room temperature in the ambient environment. The MgTi 2 O 5-δ materials can have a conductivity of about, at least about, or up to about 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, or 15 S / m, or any conductivity in between at room temperature in the ambient environment.

[0056] The conductivity can be represented by the band gap (E g ) (also known as the energy gap). The band gap refers to the energy difference between the top of the valence band and the bottom of the conduction band. Substances with a large band gap are usually insulators, while those with a smaller band gap are called semiconductors. Conductors either have no band gap or have a 0 band gap (i.e., metallic), or have a very small band gap such as (<1 eV) (i.e., semimetallic).

[0057] First-principles DFT calculations were performed to examine the conductive behavior of MgTi 2 O 5-δ . The calculations were performed in the Vienna Ab-initio Simulation Package (VASP) using the projected augmented wave potentials and the Perdew-Burke-Ernzerhof (PBE) formulation of the generalized gradient approximation (GGA). A plane-wave basis set cutoff energy of 520 eV was used.

[0058] For the atomic simulations, an orthorhombic Cmcm MgTi 2 O 5 (space group number 63) supercell with 12 formula units was used, where the k-point mesh was 3 x 3 x 3. From Figure 4A the density of states (DOS) simulations, it was found that the DFT band gap of bulk MgTi 2 O 5 is greater than 2 eV, which indicates that the parent structure MgTi 2 O 5 is an insulator. The Fermi level (E F ) was set to x = 0. At the Fermi level (EF ) Below are the occupied states; and above the Fermi level are the unoccupied states.

[0059] Conversely, as Figure 4B shown, the presence of oxygen vacancies in the bulk MgTi 2 O 5 structure changes the electrical conductivity of the material. Compared with the parent structure, the Fermi level (E 2 O 4.92 ) of the exemplary sample MgTi F ) of the disclosed material has shifted. E F is occupied (i.e., metallic), indicating that MgTi 2 O 5-δ exhibits its conductive behavior, which is further confirmed by the experiments discussed below.

[0060] DFT calculations are also used to evaluate the corrosion resistance behavior of the disclosed materials. The DFT slab models are tested with hydrogen adsorption and dissociation reactions. The hydrogen dissociation reaction is tested on the (110)MgTi 2 O 5 , (110)MgTi 2 O 5-δ , (101)TiO 2 (anatase), (110)TiO 2 (rutile) and (001)TiO 2 structures shown in Figure 5. The maximum hydrogen coverage of each slab model is tested. Table 1 below shows the hydrogen adsorption energy (Δ E ads,H ) and the maximum hydrogen coverage ([[]] θ H,cov ) in each slab model.

[0061] Table 1 – Calculated hydrogen adsorption energy (Δ E ads,H ) and maximum hydrogen coverage ([[]] θ H,cov )

[0062] <![CDATA[MgTi 2 O 5 > <![CDATA[MgTi 2 O 5-δ > <![CDATA[TiO 2 (anatase)]]> <![CDATA[TiO 2 (rutile)]]> TiO <![CDATA[Δ E ads,H [eV / H]]]> 0.876 1.159 1.010 0.960 1.045 <![CDATA θ H,cov [%]]]> 71.4 30.8 100 100 100

[0063] As shown in Table 1, compared with other tested chemical classes, (110)MgTi 2 O 5-δ has the maximum hydrogen adsorption energy. This finding is directly related to the highest chemical resistance to H adsorption of (110)MgTi 2 O 5-δ in the tested group of chemical classes. Additionally, (110)MgTi 2 O 5-δ shows the minimum hydrogen coverage (i.e., the least hydrogen dissociation).

[0064] The disclosed MgTi 2 O 5-δ materials can have a nominal chemical composition of about 25 - 40, 28 - 35, or 30 - 33 mole % of MgO and 75 - 60, 72 - 65, or 70 - 66 mole % of TiO + TiO 2 mixture. The molar ratio of Mg to Ti, Mg / Ti, can be about 0.2 - 0.8, 0.3 - 0.60, or 0.4 - 0.5.

[0065] In one or more embodiments, a method for preparing MgTi 2 O 5-δ materials is disclosed. The synthesis can include preparing dry powders of MgO, TiO, and / or TiO 2 . The method can include forming a mixture of MgO, TiO, and / or TiO 2 . The method can include mixing a first powder, MgO, and a second powder premix of TiO / TiO 2 or TiO. The method can include drying one or more compounds to be included in the mixture. The drying can be carried out in a vacuum or ultra - high vacuum, N 2 , Ar, or Ar / H 2 environment. Ultra - high vacuum refers to a condition where the pressure is below about 10 −7 Pa or 100 nPa (10 −9 mbar, ~10 −9 Torr).

[0066] The mixture can be compressed into any shape or configuration, for example, in a mold. A non - limiting example can be a compressed pellet. The compressed mixture can be heated by sintering for a certain amount of time. Sintering is a process of compacting and forming a solid mass of a material by heat and / or pressure without melting the material to its liquefaction point or the melting point of the material.

[0067] The certain amount of time can be the time required for the powder particles to fuse together and form a solid mass and / or for the appearance of the compressed material to change from light gray to blue - black. Sintering can be carried out at a temperature below the melting point of the powder mixture. In a vacuum, N 2 , Ar, or Ar / H 2 environment, the temperature can be in the range of about 400 to 2000 °C, 800 to 1800 °C, or 1200 to 1500 °C.

[0068] The amount of oxygen vacancies can be tailored according to the needs of a particular application. The amount of oxygen vacancies can be introduced, controlled, or altered by controlling, regulating, or controlling the sintering temperature. The amount of oxygen vacancies can be controlled by the TiO / TiO 2 ratio in the powder mixture. The TiO / TiO2 The ratio can be about 0:100, 1:99, 10:90, 20:80, 30:70, 40:80, 50:50, 60:40, 70:30, 80:20, 90:10, 99:1 or 100:0.

[0069] Surprisingly, it has been found that, contrary to sintering, annealing destroys the oxygen vacancies in the disclosed materials. Since oxygen vacancies are desired in the disclosed materials, annealing should be avoided, which is a process of minimizing crystal defects by heat treatment and includes heating the material above its recrystallization temperature, holding the appropriate temperature for a certain amount of time and then cooling in air.

[0070] MgTi on the metal bipolar plate 2 O 5-δ The coating can be achieved by different deposition techniques. Non-limiting examples can include spraying a solvent-containing MgTi on the BPP 2 O 5-δ , followed by a drying process. Alternatively, the method can include physical or chemical vapor deposition. As another alternative, atomic layer deposition (ALD) can be performed on a metal substrate. Depending on the choice of precursor, oxidative or reductive environment, humidity and substrate, the degree of oxygen vacancies in MgTi 2 O 5-δ may vary, resulting in different conductivities and corrosion resistance behaviors. For example, under more oxidative conditions, the surface portion of MgTi 2 O 5-δ can be more insulating, and vice versa.

[0071] The disclosed materials can be used in applications that require both corrosion resistance and good conductivity. For example, the disclosed materials can be used as a BPP coating, for the BPP body portion, for the BPP surface portion, or a combination thereof. Alternatively, the disclosed materials can be used as an anti-corrosion coating in automotive components, aerospace components, oil and gas plants or large-scale manufacturing. In an alternative embodiment, the disclosed materials can be used as a catalyst support material, for example for PEMFC applications or other catalytic applications, as further discussed below. Examples

[0072] Group A

[0073] To verify the results derived from DFT, the disclosed materials were synthesized and tested according to the methods described below.

[0074] Using dry MgO, TiO and TiO 2The powder mixture is used to synthesize the disclosed material by the following method. The MgO powder is dried in an Ar environment at 120 °C for 2 hours. Then the dried powder is mixed with TiO / TiO 2 powder to form a mixture. The mixture is pressed into pellets with a measured diameter of about 12 mm and a thickness of about 2 mm under a uniaxial load of 3000 psi. The freshly pressed pellets are light gray. Then the compacted pellets are loaded into an Al 2 O 3 crucible and heated to carry out reactive sintering (e.g., at 1450 °C) for 10 hours in a vacuum environment (10 -3 Torr). After sintering, the pellets look black with a blue tint. The method is used to prepare five batches of pellets, each batch containing three to four pellets.

[0075] Five sintered pellets (one from each batch) are sputtered with Au on both sides of the surface. Then, the pellets are assembled in an EL-Cell® ECC cell. A constant current is applied, and the voltage value is recorded after about 10 minutes until the voltage reading stabilizes. This step is repeated several times at different currents. The resistance and DC conductivity are calculated by fitting the linear slope of the V-I data.

[0076] Figure 6 An Arrhenius plot of the conductivity from 25 °C to 80 °C is shown. The average conductivity and error bars are calculated from seven different samples made from different batches. The disclosed crystalline MgTi 2 O 5-δ material shows a conductivity of about 2 - 10 S / m at room temperature in the ambient environment. The measured conductivity is higher than that of semiconductors such as Ge and Si, and slightly lower than that of carbon, iron, and gold. The activation energy of the material is about 0.13 eV in the temperature range from 25 °C to 80 °C.

[0077] X-ray photoelectron spectroscopy (XPS) and optical microscopy are used to evaluate the physical properties of the disclosed material in several pellets from two different batches. For observation purposes, some of the pellets are annealed. These pellets are compared with TiO 2 reference pellets. XPS studies of these pellets are carried out using a PHI XPS system equipped with an Al X-ray source (incident photon energy 1486.7 eV). The aperture size is set to a diameter of about 1.1 mm. The binding energy of the obtained XPS spectra is calibrated relative to the C 1s peak of adventitious carbon at 284.8 eV.

[0078] Figure 7 Pellets containing the disclosed material in its original state, pellets containing the disclosed material annealed in air, and TiO 2Refer to the Ti 2p XPS spectra of the reference pellets. The data collected indicate that the Ti in the pellets containing the disclosed material in its pristine state is mainly in the Ti4+ state, similar to that in the pellets containing the disclosed material annealed in air and TiO 2 Ti in the reference pellets. The observations and XRD analysis also indicate that the disclosed material has a crystal structure similar but not identical to that of MgTi 2 O 5 as visible in Figure 8 .

[0079] Optically evaluate the sintered pellets. The surface of the sintered pellets is visible in Fig. 9A, showing synthesized pellets characterized by black and blue hues on the pellet surface. Three of the sintered pellets were annealed in air at 600 °C for 10 h. As can be observed in Fig. 9B, the surface of the annealed pellets is partially altered at the edges of the pellets, and some surface regions of these pellets turn white while some surfaces remain black. The annealed pellets were further exposed to an additional annealing in air at 1000 °C for 10 h. As Figure 9C visible, after the second round of annealing, the entire surface of these pellets turns white. Optical images of the pellets shown in Figs. 9A - C were collected using a Keyence VHX microscope at magnifications from 100x to 1000x.

[0080] The conductivity of the as - synthesized pellets was evaluated to be approximately 1.7 - 8 S / m, while the annealed pellets shown in Fig. 9B were found to have a lower conductivity than the as - synthesized pellets, which was 0.36 S / m. The annealed pellets shown in Figure 9C were evaluated as insulating. The results indicate that the color and its conductivity are related to oxygen vacancies in the material. Without limiting the present disclosure to a single theory, it is believed that annealing in air eliminates oxygen vacancies, which subsequently results in a color change and a loss of conductivity. Figs. 9A - C imply that oxygen vacancies are the main charge carriers for conduction in the disclosed material. When oxygen vacancies are eliminated by an annealing process at 1000 °C in air or otherwise, the material transforms into an insulator.

[0081] Further test the corrosion resistance of the as - synthesized pellets. The corrosion current measurements were carried out in a three - electrode liquid cell setup. The counter electrode was a Pt mesh of approximately 16 cm 2 . The reference electrode was a standard Ag / AgCl electrode in a KCl solution. The pellet was used as the working electrode with an effective area of approximately 0.5 cm 2 . For each measurement, one pellet was measured at a time. A total of three pellets were measured. For the static corrosion current measurement, sulfuric acid with pH = 2 was used as the electrolyte at 60 °C. The static corrosion current was recorded at a 1.0 V bias relative to the Ag / AgCl reference electrode.

[0082] The results of the corrosion current measurements are shown in Figure 10 . The corrosion current density of the as-synthesized pristine disclosed material is shown at the bottom, carbon paper at the top, and polished stainless steel (SS) 316 in the middle. The pristine MgTi 2 O 5-δ material was evaluated to have a corrosion current density that is about two orders of magnitude better / lower than that of polished SS316 and carbon paper. In other words, the corrosion current measured in MgTi 2 O 5-δ indicates that MgTi 2 O 5-δ produces a stable corrosion current that is 100 times smaller than that of SS316. Overall, the crystalline MgTi 2 O 5-δ material exhibits good corrosion resistance in an acidic environment.

[0083] The MgTi 2 O 5-δ material may have a corrosion resistance (static corrosion current density) of less than about 0.5 - 5, 1 - 3, or 1.5 - 2.5 μA cm -2 at a temperature of about 0 - 80 °C, 10 - 60 °C, or 20 - 40 °C at pH 2. The MgTi 2 O 5-δ material may have a corrosion resistance of less than about 5.0, 4.0, 3.0, 2.5, 2.0, 1.8, 1.6, 1.4, 1.2, 1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1 μA cm -2 at a temperature of about 0 - 80 °C, 10 - 60 °C, or 20 - 40 °C at pH 2.

[0084] The chemical tolerance or inertness of the pellets was also tested. Chemical inertness relates to the reactivity of the material with compounds such as H 3 O + , F - and SO 4 - present in an acidic fuel cell environment. One pristine pellet was crushed into a powder, which was tested in aqua regia (a mixture of concentrated HNO 3 and HCl in a ratio of 3:1) heated to 100 - 150 °C. The powder did not dissolve, indicating good chemical stability.

[0085] In one or more non-limiting embodiments, the disclosed materials can be used as catalyst supports in a PEMFC. In a PEMFC, the anode and cathode each can contain a catalyst that facilitates the reaction of oxygen and hydrogen. The anode catalyst oxidizes the fuel to hydrogen protons and electrons at the anode, while the cathode catalyst catalyzes the oxygen reduction reaction to form water. Since the chemistry at the cathode is more complex, a higher catalyst loading is typically required at the cathode than at the anode to increase the reaction rate.

[0086] A suitable catalyst must be stable enough to withstand the corrosive environment at the cathode and must have sufficient chemical activity to be able to reduce O 2 . The catalyst must also have sufficient selectivity to produce the desired product while minimizing the production of unwanted intermediates. Once the reaction is complete, the catalyst layer should also be able to facilitate the release of the product water from the catalyst surface to free up catalytic sites.

[0087] A variety of noble metals have been used as catalysts. The most commonly used catalyst is platinum (Pt) because it has excellent catalytic activity and moderate stability to withstand its harsh operating conditions. In fact, Pt is one of the few elements that can withstand the acidic (pH < 2) operating environment of a fuel cell.

[0088] Typically, to increase the stability of the catalysts and prevent them from physically separating from the system, the catalyst materials are usually immobilized on a catalyst support material, which is usually a solid material with a high surface area. The catalyst support itself needs to be inert to prevent influencing the catalytic reaction. The most common catalyst supports for PEMFCs include graphite, carbon nanofibers, carbon nanotubes, nanospheres, nanoellipsoids, nanorods, etc., or combinations thereof.

[0089] However, under fuel cell operating conditions, especially during startup / shutdown processes, oxidation of these support materials can occur, which in turn can lead to degradation of the catalysts, which may limit the lifetime of the PEMFC. For carbon-based supports, this phenomenon is called carbon corrosion. Therefore, various metal oxides as possible alternative catalyst supports have been studied as opposed to carbon because they have a tendency to improve catalyst stability and resistance to further oxidation.

[0090] Any catalyst support material needs to meet certain criteria - being stable under PEMFC operating conditions, which are typically acidic (i.e., low pH, pH of 1 - 4), and withstanding the different voltages applied to the fuel cell (usually 0 V to ~1.2 V relative to SHE).

[0091] Among the different metal oxides used as catalyst support materials in PEMFC electrodes, TiO 2 and SnO2 has been disclosed as a leading candidate. This is due to the stability of TiO 2 and SnO 2 in aqueous electrochemical systems: stable oxides are formed, where the pH can vary from 1 - 4 (i.e., acidic), and voltages of 0 - 1.23 V can also affect the local environment during PEMFC operation. Recently, Sn-doped TiO 2 has also been tested as a catalyst support material for Pt catalysts, and the following has been reported: 1) doping TiO 2 with up to 10% Sn results in an increase in mass activity; 2) much less Pt is required for catalyst supports doped with 23 - 40% Sn in TiO 2 ; 3) Sn-doped TiO 2 is stable at 80 °C in acidic conditions when doped with <28% Sn in TiO 2 .

[0092] In one or more embodiments, the materials of formula (I) disclosed herein can be used as metal oxide supports for PEMFC catalysts in fuel cell applications on the cathode, anode, or both. The catalyst can be a noble metal or a noble-metal-free catalyst. Non-limiting examples of the catalyst can be Pt, Pd, Au, Ir, Rh, Ru, or combinations thereof. The catalyst can be a redox reaction (ORR) catalyst.

[0093] The catalyst can be deposited on the MgTi 2 O 5-δ metal oxide material, either forming one or more catalyst islands on the catalyst support as shown in Figure 11A , or in a core-shell configuration as shown in Figure 11B , where MgTi 2 O 5-δ forms the core and the catalyst forms the shell. In Figure 11A and 11B , 50 represents the catalyst support and 52 represents the catalyst. The specific configuration can be customized according to the expected performance, cost, and lifetime of the PEMFC device and / or stack system. Scanning electron microscope (SEM) cross-sectional images of MgTi 2 O 5-δ used as the catalyst support material and Pt used as the catalyst are shown in Figure 12A and 12B . The catalyst support material can have a flat or uneven surface. The catalyst support material can be used as a substrate for the catalyst material. The catalyst support material can physically and / or chemically bind the catalyst.

[0094] As demonstrated herein, comprising MgTi 2O 5-δ The catalyst support material is chemically stable in an acidic environment and has high electrochemical stability against corrosion and oxidation environments during fuel cell operating conditions.

[0095] DFT calculations were performed to construct the interface between the Pt metal catalyst and MgTi 2 O 5-δ The DFT calculations were carried out in the Vienna Ab-initio Simulation Package (VASP) using the projector augmented wave potential and the Perdew–Burke–Ernzerhof (PBE) formulation of the generalized gradient approximation (GGA). A plane wave basis set cutoff energy of 520 eV was used. DFT calculations were used to verify that Pt and MgTi 2 O 5-δ can form a stable interface, which enables MgTi 2 O 5-δ to be used as an oxide support material for PEMFC catalysts.

[0096] Table 2 below shows the interfacial energies of the Pt catalyst and MgTi 2 O 5-δ specifically, the energetically stable Pt surface facets (111), (100), and (110) were examined on (110)MgTi 2 O 5-δ Table 2 illustrates that the calculated DFT interfacial energy (without considering the facets) between (110)MgTi 2 O 5-δ and the Pt catalyst is predicted to be negative. The negative DFT interfacial energy indicates that the two chemical systems will form a stable interface. Table 2 further shows the DFT interfacial energies of Pt on TiO 2 and SnO 2 for comparison. As can be seen in Table 2, the interfacial energies of MgTi 2 O 5-δ and SnO 2 / TiO 2 are comparable. For the DFT calculations, Δ E 界面 = E 0,总 –( E 0,Pt,表面 + E 0,MOx ), where the internal energy ( E 0 ) can be obtained from the DFT calculations.

[0097] Table 2 – Calculated DFT interfacial energies (Δ E 界面 ) between the Pt catalyst and various oxide support materials

[0098] DFT interface between the Pt surface and the oxide support material <![CDATA[Δ E 界面 [J / m 2 > Figure <![CDATA[(111) Pt || (110) MgTi 2 O 5-δ > -1.83 13B, 13E <![CDATA[(100) Pt || (110) MgTi 2 O 5-δ > -2.01 13A, 13D <![CDATA[(110) Pt || (110) MgTi 2 O 5-δ > -1.35 13C, 13F <![CDATA[(111) Pt || (101) TiO 2 (anatase)]]> -1.48 - <![CDATA[(111) Pt || (110) SnO 2 (rutile)]]> -1.93 -

[0099] Figure 13A -F shows the interfaces constructed between various Pt surface facets and (110)MgTi before and after DFT relaxation calculations. Specifically, 2 O 5-δ between. Specifically, Figure 13A -C shows the interface constructed before DFT relaxation, Figure 13D -F shows the interface after DFT relaxation. It can be clearly seen from Figure 13D -F that after DFT relaxation, Pt (100) and Pt (111) on MgTi 2 O 5-δ look very similar to each other.

[0100] Table 1 further shows that (100)Pt can bind most strongly on (110)MgTi 2 O 5-δ while (110)Pt can bind less strongly on (110)MgTi 2 O 5-δ . Although the (111) facet appears to be the most energetically favorable surface facet in Pt nanoparticles, (110) and (100) were also observed at the corners and edges of the Pt particles. Depending on the synthesis temperature, time, pH, precursor materials, and routes, the size and shape of the Pt nanoparticles can be controlled, as shown in Figure 14 . Table 2 shows that all Pt facets bind on MgTi 2 O 5-δ ; the (100) and (111) facets can bind more strongly than the (110). Therefore, regardless of the size and shape of the Pt catalyst particles, DFT calculations indicate that a stable interface will form between the Pt catalyst and MgTi 2 O 5-δ .

[0101] The conductive and corrosion-resistant behaviors of the disclosed materials as catalyst supports were further investigated. Table 3 below shows the DFT binding energies (Δ 2 O and H 3 O) of H on Pt supported by various metal oxide supports. The relative binding energies (Δ E b ) are also provided, where the binding energy on pure Pt (111) is used as the reference value (i.e., zero energy). The H E rel,b ) of Pt supported on MgTi 2 O 5-δ and H 2 O and H 3The calculated binding energy of O on Pt supported on SnO 2 and TiO 2 lies between that on Pt supported on SnO 2 O 5-δ and TiO 2 . This indicates that Pt on MgTi 2 O

[0102] Table 3 – DFT binding energies (Δ 2 H 3 O and H E b ) of H

[0103] DFT interface between the Pt surface and the oxide support material <![CDATA[Δ E b,H2O [eV]]]> <![CDATA[Δ E relb,H2O [eV]]]> <![CDATA[Δ E b,H3O [eV]]]> <![CDATA[Δ E relb,H3O [eV]]]> <![CDATA[(111) Pt || (110) MgTi 2 O 5-δ > -0.311 -0.157 -0.634 -0.227 <![CDATA[(100) Pt || (110) MgTi 2 O 5-δ > -0.217 -0.063 -0.588 -0.181 <![CDATA[(110) Pt || (110) MgTi 2 O 5-δ > -0.309 -0.155 -0.497 -0.090 <![CDATA[(111) Pt || (101) TiO 2 (anatase)]]> -0.080 +0.074 -0.349 +0.058 <![CDATA[(111) Pt || (110) SnO 2 (rutile)]]> -0.492 -0.338 -0.837 -0.430 Pure (111) Pt -0.154 - -0.407 -

[0104] As can be seen from Table 3, for Pt on MgTi 2 O 5-δ , the relative binding energy of H 2 O is in the range of -0.063 to -0.157 eV. For the case of H 3 O, the binding energy varies from -0.090 eV to -0.027 eV. For both cases, the binding energies are lower than those of Pt supported on TiO 2 and higher than those of Pt supported on SnO 2 . Therefore, as described above, Pt on MgTi 2 O 5-x can have a higher "stability" towards reactants than Pt supported on SnO 2 and a higher "reactivity" than Pt supported on TiO 2 . Additionally, the corrosion-resistant behavior and enhanced electrical conductivity of the MgTi Figure 6 and 10 MgTi 2 O 5-δ materials, discussed above and cited in 2 and 2 respectively, provide additional advantages for MgTi 2 O 5-δ materials as catalyst supports compared to the current state-of-the-art TiO

[0105] MgTi 2 O 5-δCatalyst support materials can be prepared by various methods, including but not limited to solution-based methods, solid-state methods, heat treatment, and / or electrochemical methods. The catalyst support materials can be undoped and / or partially doped with nitrogen, carbon, fluorine, etc. or other elements to further enhance conductivity. Non-limiting examples of other elements can include other d 0 metals such as Zr 4+ , Hf 4+ , V 5+ and / or Cr 6+ , and / or d 10 metals such as Zn 2+ , Ga 3+ and / or Pb 4+ , and Al 3+ (no d electrons), where d 0 and d 10 metals and Al 3+ are generally more difficult to oxidize.

[0106] Non-limiting examples of preparation methods can include dissolving metal-containing precursor chemicals such as M(NO 3 ), MCl x , M(OH) x and MO x in a solvent to form an initial mixture, where M = Mg and Ti. The solvent can be water or an organic solvent. The pH of the solution can be adjusted, maintained, or controlled by the presence of oxidation or reduction chemicals. The initial mixture can be heat-treated at about 100 - 2000 °C, 200 - 1500 °C, or 300 - 1000 °C for different aging times of about 1, 2, 3, 4, 8, 12, 16, 24, 36, 48, 60, or 72 hours to form the catalyst support material. During the heat treatment, the gas environment can be controlled by N 2 , Ar, H 2 , O 2 , air, and / or vacuum. Subsequently, catalyst materials such as Pt can be deposited on the catalyst support material using solid-state, solution-based methods, and / or various deposition techniques.

[0107] Oxide precursor materials of various sizes such as MgO, TiO, TiO 2 , Mg(OH) 2 etc. can be mixed and synthesized by solid-state methods such as ball milling processes and then subjected to secondary heat treatment.

[0108] The MgTi 2 O 5-δThe catalyst support can be prepared into high-surface-area particles by a hydrothermal method and then a subsequent annealing process in an oxygen-free atmosphere. The MgTi 2 O 5-δ Non-limiting examples of the BET of the catalyst support can be about 100 - 1500, 150 - 850, or 200 - 550 m 2 / g. The MgTi 2 O 5-δ Non-limiting examples of the BET of the catalyst support can be about, at least about, or up to about 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, or 1500 m 2 / g or any range therebetween. In contrast, the Vulcan XC-72 material typically has a BET specific surface area of 250 m 2 / g; high-surface-area carbon can have a BET specific surface area of up to about 1500 m 2 / g: such as Ketjenblack EC 600JD, ultra-high-surface-area carbon (USAC), etc.

[0109] The MgTi 2 O 5-δ Another non-limiting example of the BET specific surface area of the catalyst support can be less than 100 m 2 / g, such as 0.1 - 99, 1 - 50, or 5 - 25 m 2 / g. The MgTi 2 O 5-δ The BET specific surface area of the catalyst support can be about, at least about, or up to about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 99 m 2 / g or any range therebetween.

[0110] Alternatively, the MgTi2 O 5-δ The catalyst support material can be prepared by chemical reactions at relatively high temperatures of about 400 - 2000 °C, 800 - 1800 °C, or 1200 - 1500 °C in a vacuum, N 2 , Ar, or Ar / H 2 environment and then mechanical grinding. The preparation atmosphere should be kept oxygen - free so that no oxygen is supplied during the reaction and it is actively removed from the reaction environment. MgTi 2 O 5-δ The catalyst support can be prepared by a colloidal synthesis route and then a subsequent annealing step in different atmospheres. The catalyst support can be prepared by combustion synthesis or flame synthesis methods and then a subsequent annealing step in an oxygen - free environment.

[0111] The disclosed materials can be used for catalysis in a variety of applications, including PEMFC, anion - exchange membrane fuel cells (AEMFC) at the cathode or anode, proton - exchange membrane electrolyzers, chemical synthesis, air purification, including purifying exhaust gases from internal combustion engines, photocatalysis for water - splitting cells, or photocatalysis of redox mediators for water purification.

[0112] The MgTi 2 O 5-δ The catalyst support material can be further mixed with carbon and / or another type of conductive polymer to increase conductivity. Carbon includes, but is not limited to, amorphous carbon, Denka black, Ketjen black, acetylene black, carbon nanotubes, carbon fibers, graphene, graphite, graphyne, graphene oxide, reduced graphene oxide, etc. The ratio of the mixture can be about 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, or 2:1. Alternatively, carbon and / or another type of additional support material can form one or more additional sub - layers, which serve as the support for the disclosed materials.

[0113] The MgTi 2 O 5-x The catalyst support material can be mixed with one or more types of catalyst support materials such as oxides, carbides, or intermetallic compounds. Example oxide materials can include SnO 2 , MoO 3 , Nb 2 O 5 , Ta 2 O 5 , TiO 2 , WO 3 , SnMo 4 O 6 and / or TiNb3 O 6 、GeO 2 、MoO 2 、NbO 2 、SnO、Ti 3 O 5 、SnWO 4 、WO 2 、Nb 2 SnO 6 、Sn 2 WO 5 、SnGeO 3 、Ta 2 SnO 6 、TiSn 2 O 4 、Ti 6 O or a mixture thereof. Exemplary carbides can include Nb 6 C 5 、Mo 2 C、Ta 2 C、Ti 8 C 5 、WC、TaC、Nb 2 SnC、Ti 2 GeC、Ti 3 SnC 2 、Ti 3 GeC 2 、MoC or a mixture thereof. Non-limiting examples of binary or ternary intermetallic compounds can be MoW, NbSn 2 、Nb 3 Sn、Sn 2 Mo、TaSn 2 、Ta 3 Sn、TaW 3 、TiMo、TiMo 3 、Ti 2 Mo、Ti 3 Mo、TiNb、Ti 2 Sn、Ti 2 Sn 3 、Ti 3 Sn、Ti 6 Sn 5 、NbMo 2 W、TaMo 2 W、TiMo 2 W、Ti 2 NbSn、GeMo 3 、Ge 2 Mo、NbGe 2 、Nb 5 Ge 3 、SnGe、TaGe2 , Ta 3 Ge, Ta 5 Ge 3 , TiGe 2 , Ti 5 Ge 3 , Ti 6 Ge 5 or a mixture thereof. Depending on the secondary heat treatment conditions such as temperature, the presence of an oxidizing / reducing agent, the amount (and its composition) of the oxide in the surface film and the bulk region of the intermetallic compound can be further controlled. Examples

[0114] Group B

[0115] To verify the results of the DFT calculations, the disclosed materials were used to form pellets by the method described in Group A of the above examples. Subsequently, a catalyst material containing Pt was sputtered onto the pellets, and the catalyst carrier with the catalyst was exposed to annealing at 600 °C for 10 hours. Figure 12A An example of one of the pellets containing the sputtered catalyst before the annealing process is shown. Figure 12B One of the pellets after the annealing process is shown. The dashed line indicates the interface between Pt and MgTi Figure 12A in both 2 O 5-δ and B. Figure 12A and 12B are scanning electron microscope (SEM) cross-sectional images. Figure 12B It shows that the Pt catalyst binds very well to the surface of the MgTi 2 O 5-δ support. No phase separation was observed. Experiments show that Pt makes good contact with the MgTi 2 O 5-δ material. Even after heat treatment at 600 °C for 10 hours, the surface of the Pt and MgTi 2 O 5-δ materials still maintain close contact, indicating good contact.

[0116] The processes, methods, or algorithms disclosed herein can be transferred to and implemented by a processing device, controller, or computer, which can include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms can be stored in many forms as data and instructions executable by a controller or computer, including but not limited to information permanently stored on a non-writable storage medium such as a ROM device and information changeably stored on a writable storage medium such as a floppy disk, magnetic tape, CD, RAM device, and other magnetic and optical media. The processes, methods, or algorithms can also be implemented in a software-executable object. Alternatively, appropriate hardware components such as an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a state machine, a controller, or other hardware components or devices, or a combination of hardware, software, and firmware components can be used to implement the processes, methods, or algorithms, in whole or in part.

[0117] The following applications are related to the present application: U.S. Patent Application Serial No. 16 / 675,564, filed on November 6, 2019, which is hereby incorporated by reference in its entirety.

[0118] Although the exemplary embodiments have been described above, it is not intended that these embodiments describe all possible forms encompassed by the claims. The language used in the specification is descriptive rather than restrictive, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As previously mentioned, the features of the various embodiments can be combined to form other embodiments that may not be explicitly described or shown. Although the various embodiments may have been described as providing advantages or being preferred to other embodiments or prior art implementations in one or more desired characteristics, one of ordinary skill in the art recognizes that one or more features or characteristics may be compromised to achieve the desired overall system attributes, depending on the particular application and implementation. These attributes can include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, usability, weight, manufacturability, ease of assembly, etc. Thus, to the extent that any embodiment is described as less desirable than other embodiments or prior art implementations in one or more features, such embodiments are not outside the scope of the present disclosure and may be desirable for a particular application.

Claims

1. A fuel cell bipolar plate, which comprises: a metal substrate having a body portion, and a surface portion comprising a corrosion-resistant conductive non-stoichiometric material having oxygen vacancies of formula (I): MgTi 2 O 5-δ (I), wherein δ is any number from 0 to 3 representing oxygen vacancies, including the fractional part, the non-stoichiometric material has a conductivity of 2 - 10 S / m at room temperature in the surrounding environment.

2. The bipolar plate according to claim 1, wherein the static corrosion current density of the bipolar plate is less than 1 μAcm at a temperature of 0-80 °C when the pH is 2 -2 .

3. The bipolar plate according to claim 1, wherein the Mg / Ti ratio of the non-stoichiometric material is a number in the range of 0.3 - 0.

6.

4. The bipolar plate according to claim 1, wherein the non-stoichiometric material has an activation energy of 0.13 eV in the temperature range of 25°C - 80°C.

5. The bipolar plate according to claim 1, wherein the non-stoichiometric material has a crystalline structure.

6. The bipolar plate according to claim 5, wherein the crystalline structure comprises at least one Ti atom having five bonds with oxygen atoms.

7. A proton exchange membrane fuel cell bipolar plate, which comprises: a metal substrate having a body portion and a surface portion, one of the body portion and the surface portion comprising a corrosion-resistant conductive non-stoichiometric material having oxygen vacancies of formula (I): MgTi 2 O 5-δ (I), wherein δ is any number from 0 to 3 representing oxygen vacancies, including the fractional part, The non-stoichiometric material has a nominal chemical composition of a mixture of 33 mole % MgO and 66 mole % TiO with TiO 2 of the mixture.

8. The bipolar plate according to claim 7, wherein the Mg / Ti ratio is a number in the range of 0.3 - 0.

6.

9. The bipolar plate according to claim 7, wherein the static corrosion current density of the bipolar plate is less than 1 μAcm at a temperature of 0-80 °C when the pH is 2 -2 .

10. The bipolar plate according to claim 7, wherein the non-stoichiometric material has an activation energy of 0.13 eV in the temperature range of 25°C - 80°C.

11. The bipolar plate according to claim 7, wherein the body portion comprises the non-stoichiometric material.

12. A fuel cell, which comprises: a bipolar plate having a metal substrate including a body portion and a surface portion, the surface portion comprising a corrosion-resistant conductive non-stoichiometric material having oxygen vacancies of formula (I): MgTi 2 O 5-δ (I) wherein δ is any number from 0 to 3 representing oxygen vacancies, including the fractional part, the non-stoichiometric material has a conductivity of 2 - 10 S / m at room temperature in the surrounding environment.

13. The fuel cell according to claim 12, wherein the static corrosion current density of the bipolar plate is less than 1 μA / cm² at a temperature of 0 - 80 °C when the pH is 2 -2 .

14. The fuel cell according to claim 12, wherein the Mg / Ti ratio of the non-stoichiometric material is a number in the range of 0.3 - 0.

6.

15. The fuel cell according to claim 12, wherein the fuel cell is an anion exchange membrane fuel cell.

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