Electrolytic cell bipolar plate with conductive coating and porous gas diffusion layer and method for making same

Abstract

A proton exchange membrane (PEM) electrolyzer component, selected from at least one of a bipolar plate or a porous transport layer, has an electrically conductive and oxidatively stable coating of a conductive metal nitride or a conductive metal oxide on at least one surface thereof. In some embodiments, the electrolyzer component comprises a bipolar plate. In some other embodiments, the electrolyzer component comprises a porous transport layer. In some particular embodiments, the porous transport layer comprises a porous titanium sheet.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Application No. 63 / 208,589, filed June 9, 2021, and entitled “ELECTROLYZER BIPOLAR PLATES AND POROUS GAS DIFFUSION LAYER HAVING AN OXIDATIVELY STABLE AND ELECTRICALLY CONDUCTIVE COATING AND METHOD OF MAKING THEREOF,” the entire contents of which are incorporated herein by reference.

[0002] The present disclosure is directed generally to electrolytic cells, and in particular to coatings for bipolar plates and anode gas diffusion layers / porous transport layers for electrolytic cells, and methods of making the same. [Background technology]

[0003] Proton exchange membrane (PEM) electrolysers can be used to convert water into separate hydrogen and oxygen streams. Such PEM electrolysers include a polymer electrolyte located between an anode electrode and a cathode electrode. Anode-side and cathode-side porous gas diffusion layers are located adjacent to the separate anode and cathode electrodes.

[0004] Currently, PEM electrolyzers operate in an oxidizing environment, which causes corrosion of various electrolyzer components. Oxidation increases the electrical resistance of the electrolyzer components and therefore reduces efficiency. What is needed are PEM electrolyzer components that are resistant to corrosion. Summary of the Invention [Means for solving the problem]

[0005] Provided herein is a proton exchange membrane (PEM) electrolyzer component comprising at least one of a bipolar plate or a porous transport layer, the electrolyzer component comprising an electrically conductive and oxidatively stable coating comprising a conductive metal nitride or a conductive metal oxide on at least one surface thereof. In some embodiments, the electrolyzer component comprises a bipolar plate. In some other embodiments, the electrolyzer component comprises a porous transport layer. In some particular embodiments, the porous transport layer comprises a porous titanium sheet.

[0006] In some embodiments, the electrically conductive and oxidatively stable coating comprises an electrically conductive metal nitride. In some aspects, the electrically conductive metal nitride comprises at least one of titanium nitride (TiN), tungsten nitride (WN), or tantalum nitride (TaN).

[0007] In some embodiments, the conductive and oxidatively stable coating comprises a conductive metal oxide. In some aspects, the conductive metal oxide has the formula TiO 2-x (where 0.1≦x≦0.9) 2-x wherein 0.1≦x≦0.9, is selected from the group consisting of zirconium oxide, rhenium oxide, iridium oxide, cobalt oxide, tungsten oxide, mixed metal oxides, and combinations thereof.

[0008] In some embodiments, the conductive and oxidatively stable coating comprises a conductive metal nitride and a conductive metal oxide.

[0009] In some embodiments, the conductive and oxidatively stable coating has a thickness of about 0.2 microns to about 2 microns.

[0010] Further provided herein is a PEM electrolyzer comprising an anode side flow plate, the anode side flow plate and the porous transport layer of the disclosure being located on the anode side of the electrolyzer, a cathode side flow plate, a PEM polymer electrolyte located between the anode side flow plate and the cathode side flow plate, an anode electrode located between the porous transport layer and the PEM polymer electrolyte, a cathode side gas diffusion layer located between the PEM polymer electrolyte and the cathode side flow plate, and a cathode electrode located between the cathode side gas diffusion layer and the PEM polymer electrolyte.

[0011] Further provided herein is a method comprising coating a proton exchange membrane (PEM) electrolyzer component comprising at least one of a bipolar plate or a porous transport layer on at least one surface thereof with an electrically conductive and oxidatively stable coating comprising a conductive metal nitride or a conductive metal oxide. In some embodiments, the electrolyzer component comprises a bipolar plate. In some other embodiments, the electrolyzer component comprises a porous transport layer. In some particular embodiments, the porous transport layer comprises a porous titanium sheet.

[0012] In some embodiments, the electrically conductive and oxidatively stable coating comprises an electrically conductive metal nitride. In some aspects, the electrically conductive metal nitride comprises at least one of titanium nitride (TiN), tungsten nitride (WN), or tantalum nitride (TaN).

[0013] In some embodiments, the conductive and oxidatively stable coating comprises a conductive metal oxide. In some aspects, the conductive metal oxide has the formula TiO 2-x (where 0.1≦x≦0.9) 2-xwherein 0.1≦x≦0.9, is selected from the group consisting of zirconium oxide, rhenium oxide, iridium oxide, cobalt oxide, tungsten oxide, mixed metal oxides, and combinations thereof.

[0014] In some embodiments, the conductive and oxidatively stable coating comprises a conductive metal nitride and a conductive metal oxide.

[0015] In some embodiments, the conductive and oxidatively stable coating has a thickness of about 0.2 microns to about 2 microns.

[0016] In some embodiments, the coating step is accomplished by sputtering, hi some other embodiments, the coating step is accomplished by pressing, a powder metallurgy process, or a tape casting method.

[0017] In some embodiments, the conductive and oxidatively stable coating is formed in situ. In one example, the component comprises a porous transport layer, the porous transport layer comprising a porous titanium sheet formed by powder metallurgy. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective cutaway view of a PEM electrolyzer of the present disclosure.

[0019] [Diagram 2] FIG. 2 shows a side view of a porous transport layer coated with a metal nitride or metal oxide coating.

[0020] [Diagram 3] 3-5 show side cross-sectional views of various apparatus that can be used to form metal nitride or metal oxide coatings. [Figure 4] 3-5 show side cross-sectional views of various apparatus that can be used to form metal nitride or metal oxide coatings. [Diagram 5] 3-5 show side cross-sectional views of various apparatus that can be used to form metal nitride or metal oxide coatings.

[0021] [Figure 6] FIG. 6 shows a graph of the electrochemical stability of a bipolar plate comprising a conductive and oxidatively stable coating of the present disclosure compared to a gold (Au) coating. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Detailed Description Provided herein is an electrolytic cell component coated with an electrically conductive and oxidatively stable coating. The coating comprises at least one of an electrically conductive metal nitride or an electrically conductive metal oxide. The coating provides slight electrical resistance while protecting the electrolytic cell component from oxidation, and thus exhibits higher electrochemical stability and electrical conductivity compared to electrolytic cell components lacking the coating of the present disclosure. As used herein, "electrochemical stability" refers to the resistance of an electrolytic cell component to corrosion when exposed to high voltage (e.g., about 2.5V). Thus, an electrolytic cell component with high electrochemical stability is highly resistant to corrosion when exposed to high voltage.

[0023] The electrolyzer components may comprise the bipolar plate or the porous transport layer of the electrolyzer. In one embodiment, an electrically conductive and oxidatively stable coating (also referred to as a protective layer) is provided on one or both bipolar plates (i.e., flow plates) and / or on the porous transport layer of a proton exchange membrane (PEM) electrolyzer. The porous transport layer may be a porous titanium sheet configured to function as an anode-side gas diffusion layer, as further described herein. An example of a bipolar plate suitable for this purpose is described in more detail in U.S. Application No. 17 / 402,821, the entire contents of which are incorporated herein by reference. An example of a porous transport layer is described in more detail in U.S. Application No. 17 / 384,033, the entire contents of which are incorporated herein by reference.

[0024] The electrically conductive and oxidatively stable coating comprises at least one electrically conductive metal oxide or at least one electrically conductive metal nitride coating. The coating may contain an oxide or nitride of a single metal or two or more metals. The coating may be applied to at least one surface of the electrolytic cell component, a portion of at least one surface of the electrolytic cell component, or the coating may be applied to the entire surface of the electrolytic cell component.

[0025] Examples of conductive metal oxides or conductive metal nitrides include one or more conductive metal nitrides such as TiN, WN, or TaN, and / or metal-rich titanium oxide (TiO 2-x , where 0.1≦x≦0.9, also referred to herein as “titanium suboxide”), Sn or Pb dioxide (including fluorine-doped tin oxide), manganese oxides (e.g., manganese dioxide, MnO2), metal-rich zirconium oxide (ZrO 2-x , where 0.1≦x≦0.9), and includes one or more conductive metal oxides, such as rhenium oxide, cobalt oxide, iridium oxide, or tungsten oxide, or mixed metal oxides, such as indium tin oxide, zinc aluminum oxide, lanthanum strontium manganate, etc.

[0026] In some aspects, the coating comprises a metal-rich zirconium oxide, ZrO 2-x When including, x can be greater than or equal to about 0.1, less than or equal to about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, or 0.9. In some additional aspects, x can be from about 0.1 to about 0.2, from about 0.1 to about 0.3, from about 0.1 to about 0.4, from about 0.1 to about 0.5, from about 0.1 to about 0.6, from about 0.1 to about 0.7, from about 0.1 to about 0.8, from about 0.2 to about 0.9, from about 0.3 to about 0.9, from about 0.4 to about 0.9, from about 0.5 to about 0.9, from about 0.6 to about 0.9, from about 0.7 to about 0.9, or from about 0.8 to about 0.9.

[0027] In some aspects, the coating comprises a metal-rich titanium oxide, TiO 2-x When including, x can be greater than or equal to about 0.1, less than or equal to about 0.2, about 0.3, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, or 0.9. In some additional aspects, x can be from about 0.1 to about 0.2, from about 0.1 to about 0.3, from about 0.1 to about 0.4, from about 0.1 to about 0.5, from about 0.1 to about 0.6, from about 0.1 to about 0.7, from about 0.1 to about 0.8, from about 0.2 to about 0.9, from about 0.3 to about 0.9, from about 0.4 to about 0.9, from about 0.5 to about 0.9, from about 0.6 to about 0.9, from about 0.7 to about 0.9, or from about 0.8 to about 0.9.

[0028] The conductive metal oxide or conductive metal nitride coating may further include a dopant. The dopant may improve the electrical conductivity of the coating. The dopant may include dopants known in the art to increase electrical conductivity, such as niobium. The dopant may be present in an amount of about 1% to about 2% by weight of the coating, for example, the dopant may be present in an amount of about 1.0%, about 1.1%, about 1.2%, about 1.3%, about 1.4%, about 1.5%, about 1.6%, about 1.7%, about 1.8%, about 1.9%, or about 2.0% by weight of the coating.

[0029] The coating may contain at least one of the conductive metal nitrides described above, at least one of the conductive metal oxides described above, or a mixture of two or more conductive metal nitrides, a mixture of two or more conductive metal oxides, or a mixture of at least one conductive metal nitride and at least one conductive metal oxide. When the coating includes a conductive metal nitride and a conductive metal oxide, the coating may be a mixture or combination of a conductive metal nitride and a conductive metal oxide, or the coating may comprise at least two coating layers, each coating layer including one of a conductive metal nitride and a conductive metal oxide.

[0030] When the coating contains at least one metal nitride and at least one metal oxide, the at least one metal nitride may be present in an amount of about 10% to about 90% by weight of the coating. For example, the at least one metal nitride may be present in an amount of about 10% to about 20%, about 10% to about 30%, about 10% to about 40%, about 10% to about 50%, about 10% to about 60%, about 10% to about 70%, about 10% to about 80%, about 20% to about 90%, about 30% to about 90%, about 40% to about 90%, about 50% to about 90%, about 60% to about 90%, about 70% to about 90%, or about 80% to about 90% by weight of the coating.

[0031] When the coating contains at least one metal nitride and at least one metal oxide, the at least one metal oxide may be present in an amount of about 10% to about 90% by weight of the coating. For example, the at least one metal oxide may be present in an amount of about 10% to about 20%, about 10% to about 30%, about 10% to about 40%, about 10% to about 50%, about 10% to about 60%, about 10% to about 70%, about 10% to about 80%, about 20% to about 90%, about 30% to about 90%, about 40% to about 90%, about 50% to about 90%, about 60% to about 90%, about 70% to about 90%, or about 80% to about 90% by weight of the coating.

[0032] The coating may have a thickness of about 0.2 to about 2 microns, e.g., about 0.2 microns to about 0.4 microns, about 0.2 microns to about 0.6 microns, about 0.2 microns to about 0.8 microns, about 0.2 microns to about 1 micron, about 0.2 microns to about 1.2 microns, about 0.2 microns to about 1.4 microns, about 0.2 microns to about 1.6 microns, about 0.2 microns to about 1.8 microns, about 0.4 microns to about 2 microns, about 0.6 microns to about 2 microns, about 0.8 microns to about 2 microns, about 1 micron to about 2 microns, about 1.2 microns to about 2 microns, about 1.4 microns to about 2 microns, about 1.6 microns to about 2 microns, or about 1.8 microns to about 2 microns. In some particular embodiments, the coating may have a thickness of less than about 0.2 microns. Thicker coatings tend to have higher electrical resistance, and therefore thinner coating thicknesses are preferred.

[0033] The coated electrolytic cell components may have a lower interfacial resistance compared to electrolytic cells lacking the coating of the present disclosure. As used herein, interfacial resistance refers to the electrical resistance between the coating and the electrolytic cell components, and between the coated electrolytic cell components and the membrane (e.g., polymer exchange membrane). Stated differently, interfacial resistance refers to the electrical resistance across the coating, and includes any voltage loss from electricity transferring to or from the coating.

[0034] The interfacial resistance of the coated electrolytic cell components is about 0.1 to about 5 milliohm cm 2 For example, the interfacial resistance of the coated electrolytic cell components may be from about 0.1 to about 0.5 milliohm cm 2 , about 0.1 to about 1 milliohm cm 2 , about 0.1 to about 1.5 milliohm cm 2 , about 0.1 to about 2 milliohms cm 2 , about 0.1 to about 2.5 milliohm cm 2 , about 0.1 to about 3 milliohms cm 2 , about 0.1 to about 3.5 milliohm cm 2, about 0.1 to about 4 milliohms cm 2 , about 0.1 to about 4.5 milliohm cm 2 , 0.5 to about 5 milliohms cm 2 , about 1 to about 5 milliohms cm 2 , about 1.5 to about 5 milliohms cm 2 , about 2 to about 5 milliohms cm 2 , about 2.5 to about 5 milliohms cm 2 , about 3 to about 5 milliohms cm 2 , about 3.5 to about 5 milliohms cm 2 , about 4 to about 5 milliohms cm 2 , or about 4.5 to about 5 milliohms cm 2 The interface resistance may preferably be less than 2 milliohms cm 2 It is.

[0035] The electrolytic cell components may also include a transport layer. A porous titanium layer (e.g., a sheet) may be used as the anode side gas diffusion layer (i.e., transport layer) 114. In one embodiment, the porous titanium layer (e.g., a sheet) used as the anode side gas diffusion layer 114 is formed by a powder process. In some embodiments, the powder process may include tape casting, physical vapor deposition, or powder compaction. After sintering the titanium sheet, it is coated on both sides (e.g., on the anode electrode side and the flow plate side) with a conductive metal nitride or conductive metal oxide coating to provide good conductivity and corrosion resistance.

[0036] The porous titanium layer may have a porosity of about 30% to about 50%. Methods for determining the porosity of a material are generally known in the art. In some embodiments, the titanium layer may have a porosity of about 30% to about 35%, about 30% to about 40%, about 30% to about 45%, about 35% to about 40%, about 35% to about 45%, about 35% to about 50%, about 40% to about 45%, about 40% to about 50%, or about 45% to about 50%.

[0037] FIG. 1 is a perspective cutaway view of a PEM electrolyzer cell described in an article by Greig Chisholm et al. entitled "3D printed flow plates for the electrolysis of water: An economic and adaptable approach to device manufacture" published in Energy Environ. Sci., 2014, 7, 3026-3032. The PEM electrolyzer 100 comprises a PEM electrolyzer cell that may include an anode side flow plate 102 and a cathode side flow plate 104 with fluid flow channels 106 and respective openings 108, 109, 110, a PEM polymer electrolyte 112 located between the flow plates 102 and 104, an anode side gas diffusion layer 114 located between the electrolyte 112 and the anode side flow plate 102, an anode electrode 116 located between the anode side gas diffusion layer 114 and the electrolyte 112, a cathode side gas diffusion layer 118 located between the electrolyte 112 and the cathode side flow plate 104, and a cathode electrode 120 located between the cathode side gas diffusion layer 118 and the electrolyte 112.

[0038] The anode side flow plate 102 may include a water inlet opening 108, an oxygen outlet opening 109, and a water flow channel (e.g., a serpentine path groove) 106 connecting the water inlet opening 108 and the oxygen outlet opening 109 on the side of the flow plate 102 facing the anode side gas diffusion layer 114. The anode side gas diffusion layer 114 may include a porous titanium layer. The cathode side gas diffusion layer 118 may include a porous carbon layer. The anode electrode 116 may include any suitable anode catalyst, such as an iridium layer. The cathode electrode 120 may include any suitable cathode catalyst, such as a platinum layer or platinum on a carbon layer. Other precious metal catalyst layers may also be used for the anode and / or cathode electrodes. The electrolyte 112 is an electrolyte of the formula CHF 13 O5S .Any suitable proton exchange (eg, hydrogen ion transport) polymer membrane may be included, such as a Nafion® membrane, which is composed of a sulfonated tetrafluoroethylene-based fluoropolymer copolymer having C2F4.

[0039] In operation, water is provided into the water flow channels 106 through the water inlet openings 108. The water flows through the water flow channels 106 and through the anode side gas diffusion layer 114 to the anode electrode 116. The water is electrochemically separated into oxygen and hydrogen at the anode electrode 116 in response to application of an external current or voltage between the anode electrode 116 and the cathode electrode 120. The oxygen diffuses back through the anode side gas diffusion layer 114 to the anode side flow plate 102 and exits the electrolytic cell 100 through the oxygen outlet openings 109. The hydrogen ions diffuse through the electrolyte 112 to the cathode electrode 120 and then exit the electrolytic cell 100 through the cathode side gas diffusion layer 118 and the hydrogen outlet openings 110 in the cathode side flow plate 104.

[0040] FIG. 2 shows an enlarged side view of a porous transport layer 114 coated with a metal nitride or metal oxide coating 130 .

[0041] Further provided herein is a method comprising coating a proton exchange membrane electrolyzer component. The electrolyzer component may be any electrolyzer component described herein, preferably comprising at least one of a bipolar plate or a porous transport layer with an electrically conductive and oxidatively stable coating. The electrically conductive and oxidatively stable coating may be any coating of the present disclosure, preferably comprising an electrically conductive metal nitride or an electrically conductive metal oxide on at least one surface of the electrolyzer component. The method may further comprise incorporating the coated electrolyzer component into a PEM electrolyzer.

[0042] The coating step may be accomplished by any suitable method known in the art, such as physical vapor deposition (e.g., sputtering), powder metallurgy, pressing, screen printing, or tape casting, etc. In a preferred embodiment, the coating is formed via screen printing or tape casting.

[0043] In a preferred embodiment, the coating may be formed prior to the step of sintering the electrolytic cell components, i.e., in situ. By forming the coating in situ, the interfacial resistance of the electrolytic cell components is significantly reduced compared to coatings formed after sintering. In situ coatings may be formed by powder metallurgy, pressing, screen printing, or tape casting.

[0044] FIG. 3 shows a side cross-sectional view of an exemplary sputtering apparatus as described in https: / / en.wikipedia.org / wiki / Sputter_deposition (incorporated herein by reference in its entirety). Sputtering apparatus and methods of sputter deposition are generally known to those skilled in the art. Sputtering is performed by introducing a controlled gas into a vacuum chamber, electrically exciting a cathode, and establishing a self-sustaining plasma. The exposed surface of the cathode is a slab of material to be coated onto a substrate. Atoms of the controlled gas become ionized and accelerate into the cathode, dislodging atoms in the cathode material, which are then deposited onto the substrate. Sputtering can be reactive sputtering, conducted from one or more metal targets in a nitrogen or oxygen-containing plasma to form a metal nitride and / or metal oxide coating, or non-reactive sputtering, conducted from one or more metal nitride and / or metal oxide targets in an inert gas (e.g., argon) plasma.

[0045] FIG. 4 shows a side cross-sectional view of an exemplary powder compaction (e.g., powder metallurgy) apparatus as described at https: / / thelibraryofmanufacturing.com / pressing_sintering.html (hereby incorporated by reference in its entirety). Powder compaction apparatus and methods of powder compaction are generally known in the art. Metal oxide or metal nitride powder may be placed on top of and / or under the titanium layer in the die cavity and then compressed to form a coated titanium sheet compact. The pressing step is generally performed at room temperature, resulting in a green compact. The pressing force is generally about 10,000 psi to about 120,000 psi. The green compact is then sintered by any sintering method known to those skilled in the art. This process allows for the creation of a metal nitride or metal oxide protective coating in situ during the manufacture of the PEM electrolyzer components.

[0046] The coating may be accomplished via tape casting. FIG. 5 shows a side cross-sectional view of an exemplary tape casting apparatus. Tape casting apparatus and methods of tape casting are generally known to those skilled in the art. In the exemplary tape casting apparatus 500 shown in FIG. 5, a sliding material 502, such as a mixture (e.g., slurry) of metal powder, solvent, binder, and optionally one or more additional components, such as plasticizers and / or surfactants, is provided into a dispensing chamber 504 from a storage vessel, such as a fluid holding tank. The metal powder may include elemental metal powder (i.e., titanium) and / or metal hydride (e.g., TiH2) powder. In some examples, titanium hydride powder may be used to lower production costs due to lower raw material costs and less energy usage during sintering due to its exothermic reaction when undergoing Ti conversion at about 600-800°C. Thus, in one embodiment, the titanium-containing powder comprises a mixture of elemental titanium and titanium hydride powders, where the titanium hydride is subsequently thermally converted to elemental titanium in an exothermic reaction, such as during sintering and / or during a separate annealing step.

[0047] A slide material 502 is dispensed from a dispensing chamber 504 onto a moving tape carrier web 506. The tape carrier web 506 may comprise a belt of metal (e.g., steel), glass, polymer, etc., that moves past a doctor blade 508. The slide material 502 moving on the tape carrier web 506 under the doctor blade 508 is flattened by the doctor blade 508 into a green titanium-containing tape 510. Various formulations of powder size, specific content, and solids ratio of the green titanium-containing tape 510 can be produced with slight variations in the slide material (i.e., slurry) 502 formulation.

[0048] The tape carrier web 506 may then move the green titanium-containing tape 510 through a drying chamber 512. The drying chamber 512 may include a heated air inlet 514 and a saturated air outlet 516. The heated air (or another heat source) dries the green titanium-containing tape 510, and the evaporated solvent from the tape 510 is removed with the air through the saturated air outlet 516. The dried green titanium-containing tape 510 may then be cut in a cutting station 518 into titanium green sheets 510S having the shape of the anode-side gas diffusion layer.

[0049] The dried green titanium-containing tape 510, which has been cut into titanium green sheets 510S, is then sintered at a desired temperature in a sintering chamber 520 to form the anode-side gas diffusion layer 114. Preferably, the titanium green sheets 510S are sintered at 1,000-1,100 degrees Celsius in an oxygen-free or low-oxygen atmosphere. The atmosphere may include an inert atmosphere of any suitable inert gas, such as a noble gas, such as argon. The atmosphere may include an oxygen partial pressure of less than 0.1 atmosphere, such as 0.0001-0.01 atmosphere.

[0050] In one embodiment, the dried green titanium-containing tape 510 may be provided from the drying chamber 512 into a cutting station 518, and the cut tape (i.e., titanium green sheet 510S) is then provided from the cutting station 518 into a sintering chamber 520 for sintering using the same tape carrier web 506. Optionally, an additional chamber, such as a debinding chamber, may be located between the drying chamber 512 and the sintering chamber 520 if a debinding step, performed at a temperature between the drying temperature and the sintering temperature, is desired.

[0051] The sintering chamber 520 may comprise a resistively heated or gas heated continuous furnace (e.g., a belt furnace). In such an embodiment, the dried green titanium-containing tape 510 (i.e., the titanium green sheet 510S) moves through the drying chamber 512, the cutting station 518, and the continuous furnace on the same tape carrier web 506. In another embodiment, the sintering chamber 520 may comprise a rapid thermal annealing ("RTA") machine (also referred to as a rapid thermal processing ("RTP") machine) in which the cut and dried green titanium-containing tape 510 (i.e., the titanium green sheet 510S) is heated by a flash lamp or a laser beam. In this embodiment, the green titanium-containing tape 510 moves through the drying chamber 512, the cutting station 518, and the RTA machine on the same tape carrier web 506. Thus, the steps of flattening the sliding material 502, drying the tape, cutting the tape, and sintering the cut tape may occur continuously on the same moving tape carrier web 506.

[0052] The sintering chamber 520 may comprise an upstream portion 520A and a downstream portion 520B located downstream of the upstream portion 520A with respect to the moving direction of the tape carrier web 506. An optional partition 520P may be provided between the upstream and downstream portions of the sintering chamber 520. The upstream portion 520A may be maintained in an oxygen-free or low-oxygen atmosphere, such as a noble gas (e.g., argon) atmosphere. The downstream portion 520B may be maintained in a nitrogen-containing atmosphere (e.g., a low-pressure or vacuum atmosphere with a nitrogen-containing gas partial pressure), such as a nitrogen gas or ammonia-containing atmosphere. The titanium green sheet 510S may be reaction-sintered in the downstream portion 520B to form a titanium nitride or titanium oxide layer on its surface. This coating improves the performance of the titanium gas diffusion layer 114.

[0053] In alternative embodiments, the sliding material 502 may be provided onto the tape carrier web 506 from the side and / or bottom instead of from the top as shown in Figure 6. If the sliding material 502 is provided from the side, the apparatus 500 may be referred to as a slot die coater apparatus. If the sliding material 502 is provided from the bottom, the apparatus 500 may be referred to as an edge coater or microgravure coater. EXAMPLES

[0054] Example 1 Oxidation current performance of coated electrolyzer components Plates as described in the present disclosure were provided and coated with either a gold (Au) coating or a titanium suboxide coating. The plates were incorporated into an electrochemical cell, with the coated plates acting as electrodes. The electrodes were exposed to highly oxidizing positive potentials against a platinum counter electrode. The gold-coated plate was exposed to a potential of 2 V, and the titanium-coated plate was exposed to potentials of 2 V and 2.4 V. Electrochemical activity was determined by measuring current flow, which is shown in FIG. 6 as a normalized figure of merit (FOM), which is proportional to current flow. A low FOM indicates a small current flow, whereas a high FOM indicates a large current flow. A large current flow indicates a high level of oxidation of the coating and substrate, which reduces electrochemical stability.

[0055] As can be seen in FIG. 6, the plate with the titanium suboxide coating had a lower FOM compared to the plate with the gold coating. This indicates that the current flow through the plate with the titanium suboxide coating had a smaller current flow, i.e., less oxidation of the coating and substrate. Furthermore, increasing the voltage of the plate with the titanium suboxide coating further reduced the current flow. Thus, the titanium suboxide coated plate had a higher electrochemical stability compared to the gold coated plate. ILLUSTRATIVE EMBODIMENTS

[0056] Embodiment 1: A proton exchange membrane (PEM) electrolyzer component comprising at least one of a bipolar plate or a porous transport layer, the electrolyzer component comprising an electrically conductive and oxidatively stable coating comprising a conductive metal nitride or a conductive metal oxide on at least one surface of the electrolyzer component.

[0057] Embodiment 2: The component of embodiment 1, wherein the coating comprises a conductive metal nitride.

[0058] Embodiment 3: The component of embodiment 2, wherein the conductive metal nitride comprises at least one of TiN, WN, or TaN.

[0059] Embodiment 4: The component of any one of embodiments 1-3, wherein the coating comprises a conductive metal oxide.

[0060] Embodiment 5: The conductive metal oxide is represented by the formula TiO 2-x (wherein 0.1≦x≦0.9) 2-x 5. The component of embodiment 4, wherein the component is selected from the group consisting of zirconium oxide, rhenium oxide, iridium oxide, cobalt oxide, tungsten oxide, mixed metal oxides, and combinations thereof, enriched with a metal having the formula: where 0.1≦x≦0.9.

[0061] Embodiment 6: The component of embodiment 1, wherein the coating comprises a conductive metal oxide and a conductive metal nitride.

[0062] Embodiment 7: The component of any of embodiments 1-6, wherein the conductive and oxidatively stable coating has a thickness of about 0.2 microns to about 2 microns.

[0063] Embodiment 8: A component according to any of embodiments 1-7, wherein the component comprises a bipolar plate.

[0064] Embodiment 9: The component of any of embodiments 1-7, wherein the component comprises a porous transport layer, the porous transport layer comprising a porous titanium sheet.

[0065] Embodiment 10: A PEM electrolyser comprising: an anode side flow plate, the anode side flow plate and the porous transport layer of embodiment 9 being located on the anode side of the electrolytic cell; A cathode side flow plate; a PEM polymer electrolyte located between the anode flow plate and the cathode flow plate; an anode electrode located between the porous transport layer and the PEM polymer electrolyte; a cathode side gas diffusion layer located between the PEM polymer electrolyte and the cathode side flow plate; a cathode electrode located between the cathode-side gas diffusion layer and the PEM polymer electrolyte; A PEM electrolyser comprising:

[0066] Embodiment 11: A method comprising coating a proton exchange membrane (PEM) electrolyzer component comprising at least one of a bipolar plate or a porous transport layer on at least one surface thereof with an electrically conductive and oxidatively stable coating comprising a conductive metal nitride or a conductive metal oxide.

[0067] Embodiment 12: The method of embodiment 11, wherein the conductive and oxidatively stable coating comprises a conductive metal nitride.

[0068] Embodiment 13: The method of embodiment 12, wherein the conductive metal nitride comprises at least one of TiN, WN, or TaN.

[0069]

[0023] Embodiment 14: The method of embodiment 11, wherein the coating comprises a conductive metal oxide.

[0070] Embodiment 15: The conductive metal oxide is represented by the formula TiO 2-x (wherein 0.1≦x≦0.9) 2-x 15. The method of embodiment 14, wherein the oxide is selected from the group consisting of zirconium oxide, rhenium oxide, iridium oxide, cobalt oxide, tungsten oxide, mixed metal oxides, and combinations thereof, enriched with a metal having the formula: where 0.1≦x≦0.9.

[0071] Embodiment 16: The method of embodiment 11, wherein the coating comprises a conductive metal nitride and a conductive metal nitride.

[0072] Embodiment 17: The method of any of embodiments 11-16, wherein the conductive and oxidatively stable coating has a thickness of about 0.2 microns to about 2 microns.

[0073] Embodiment 18: The method of any of embodiments 11-17, wherein the electrolytic cell component comprises a bipolar plate.

[0074] Embodiment 19: The method of any of embodiments 11-17, wherein the electrolytic cell component comprises a porous transport layer, the porous transport layer comprising a porous titanium sheet.

[0075] Embodiment 20: The method of embodiment 19, further comprising incorporating a porous transport layer into a PEM electrolytic cell.

[0076] Embodiment 21: The method of any of embodiments 11-20, wherein the coating step is accomplished by sputtering.

[0077] Embodiment 22: The method of any of embodiments 11-21, wherein the coating step is accomplished by pressing, a powder metallurgy process, or a tape casting method.

[0078] Embodiment 23: The method of any of embodiments 11-22, wherein the conductive and oxidatively stable coating is formed in situ.

[0079] Embodiment 24: The component comprises a porous transport layer; the porous transport layer comprises a porous titanium sheet formed by powder metallurgy; 24. The method of embodiment 23.

[0080] Concentrations, amounts, and other numerical data may be expressed or presented herein in a range format. It is to be understood that such range formats are used merely for convenience and brevity, and should be interpreted flexibly to include not only the numerical values ​​explicitly recited as range limits, but also all individual numerical values ​​or subranges encompassed within the range, as if each numerical value and subrange were explicitly recited. By way of illustration, the numerical range "about 2 to about 50" should be interpreted not only to include the explicitly recited values ​​of 2 to 50, but also to include all individual values ​​and subranges within the indicated range. Thus, included within the numerical ranges are individual values ​​such as 2, 2.4, 3, 3.7, 4, 5.5, 10, 10.1, 14, 15, 15.98, 20, 20.13, 23, 25.06, 30, 35.1, 38.0, 40, 44, 44.6, 45, 48, etc., and subranges such as 1-3, 2-4, 5-10, 5-20, 5-25, 5-30, 5-35, 5-40, 5-50, 2-10, 2-20, 2-30, 2-40, 2-50, etc. This same principle also applies to ranges reciting only one numerical value, either as a minimum or maximum value. Moreover, such an interpretation should be applied regardless of the category of the range or the characteristic being described.

[0081] As used herein, the term "about" is used to provide flexibility to the endpoints of a numerical range by assuming that a given value may be "slightly above" or "slightly below" the endpoint. For example, the endpoints may be within 10%, 8%, 5%, 3%, 2%, or 1% of the recited value. Furthermore, for convenience and brevity, it is understood that the numerical range "about 50 mg / mL to about 80 mg / mL" also provides support for the range "50 mg / mL to 80 mg / mL."

[0082] While the foregoing refers to certain preferred embodiments, it will be understood that the invention is not so limited. It will occur to those skilled in the art that various modifications may be made to the disclosed embodiments, and that such modifications are intended to be within the scope of the invention. All publications, patent applications, and patents cited herein are incorporated herein by reference in their entirety.

Claims

**Claim 1**: A method comprising: coating at least one surface of a proton exchange membrane (PEM) electrolyzer component comprising at least one of a bipolar plate or a porous transport layer with a conductive and oxidation-stable coating comprising a conductive metal nitride, a conductive metal oxide, or a combination thereof; comprising: said coating being performed by pressing or tape casting, said conductive and oxidation-stable coating being formed prior to sintering of said PEM electrolyzer component; said conductive metal oxide being selected from the group consisting of titanium oxides rich in metals having the formula TiO₂₋ₓ (where 0.1 ≤ x ≤ 0.9), tin or lead dioxides, manganese oxides, zirconium oxides rich in metals having the formula ZrO₂₋ₓ (where 0.1 ≤ x ≤ 0.9), rhenium oxide, iridium oxide, cobalt oxide, tungsten oxide, mixed metal oxides, and combinations thereof. **Claim 2** The method according to claim 1, wherein said conductive metal nitride comprises at least one of TiN, WN, or TaN. **Claim 3** The method according to claim 1, wherein said conductive and oxidation-stable coating has a thickness of from about 0.2 microns to about 2 microns. **Claim 4** The method according to claim 1, wherein said electrolyzer component comprises said bipolar plate. **Claim 5** The method according to claim 1, wherein said electrolyzer component comprises said porous transport layer, and said porous transport layer comprises a porous titanium sheet. **Claim 6** The method according to claim 5, further comprising incorporating said porous transport layer into a PEM electrolyzer. **Claim 7** A proton exchange membrane (PEM) electrolyzer component comprising at least one of a bipolar plate or a porous transport layer, wherein the PEM electrolyzer component is fabricated by the method according to claim 1, and the electrolyzer component comprises a conductive and oxidation-stable coating on at least one surface of the electrolyzer component, the conductive and oxidation-stable coating consisting of a conductive metal nitride, a conductive metal oxide, or a combination thereof, and the conductive metal oxide is titanium oxide rich in a metal having the formula TiO₂₋ₓ (where 0.1 ≤ x ≤ 0.9), tin or lead dioxide, manganese oxide, zirconium oxide rich in a metal having the formula ZrO₂₋ₓ (where 0.1 ≤ x ≤ 0.9), rhenium oxide, iridium oxide, cobalt oxide, tungsten oxide, a mixed metal oxide, and a combination thereof, a component selected from the group consisting of.

8. The component according to claim 7, wherein the conductive metal nitride comprises at least one of TiN, WN, or TaN.

9. The component according to claim 7, wherein the conductive and oxidation-stable coating has a thickness of about 0.2 microns to about 2 microns.

10. The component according to claim 7, wherein the conductive and oxidation-stable coating further comprises a dopant.

11. The component according to claim 10, wherein the dopant comprises niobium.

12. The component according to claim 11, wherein the dopant is present in the coating in an amount of about 1% to about 2% per weight ratio of the coating.

13. The component according to claim 7, wherein the PEM electrolyzer component has an interfacial resistance of about 0.1 milliohm·cm² to about 5 milliohm·cm².

14. The component according to claim 7, wherein the PEM electrolyzer component has a porosity of about 30% to about 50%.

15. A PEM electrolyzer, An anode-side flow plate, wherein the anode-side flow plate and the porous transport layer according to claim 7 are located on the anode side of the electrolyzer, an anode-side flow plate, and A cathode-side flow plate, A PEM polymer electrolyte located between the anode-side flow plate and the cathode-side flow plate, An anode electrode located between the porous transport layer and the PEM polymer electrolyte, A cathode-side gas diffusion layer positioned between the PEM polymer electrolyte and the cathode-side flow plate, and a cathode electrode positioned between the cathode-side gas diffusion layer and the PEM polymer electrolyte are provided in a PEM electrolytic cell.

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