Anti-hydrogen embrittlement composite coating for bipolar plate of PEM electrolyzer and preparation method thereof

Abstract

The invention discloses a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer and a preparation method thereof. The coating comprises a hydrogen solidifying bottom layer, a hydrogen barrier layer and a conductive outer layer for inhibiting hydrogen dissociation, which are sequentially formed on the surface of a bipolar plate substrate of a PEM electrolyzer by physical vapor deposition. The material of the hydrogen solidifying bottom layer is selected from La, Ce, Ni, Co, Mn, Al metals and their alloys, zirconium-based alloys, titanium-based alloys, magnesium-based alloys and their oxides; the material of the hydrogen barrier layer is selected from W, Be, W-Be alloy, nitride, carbide, oxide, and the hydrogen diffusion coefficient is less than 10 ‑14 mol / s / m / Pa 0.5 The conductive outer layer material for inhibiting hydrogen dissociation is selected from Ag, Au, Cu-Ag, and Cu-Au materials, and the hydrogen dissociation energy is greater than 0.1 eV. The present invention achieves a hydrogen barrier effect by combining three methods: inhibiting hydrogen decomposition, reducing hydrogen diffusion, and adsorption and fixation, thereby improving the stability and life of the cathode plate of the PEM electrolyzer.

Description

Technical Field

[0001] The invention belongs to the technical field of fuel cell materials, and in particular relates to a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer and a preparation method thereof. Background Art

[0002] Hydrogen has the advantages of light weight, high calorific value, and clean combustion products, and is considered to be an ideal energy carrier. However, since there are still many challenges in the preparation, storage, and application of hydrogen, the hydrogen fuel system is still in its early stages. The development of low-cost, efficient, clean, and convenient hydrogen production technologies and processes is a core issue in the development of the hydrogen energy industry. At present, the industry mainly converts natural gas and water into carbon monoxide and hydrogen through steam reforming, but the energy efficiency of the conversion process is low, and residual carbon oxides will be produced, resulting in high cost and low purity of hydrogen preparation. From the perspective of conversion, the purity of hydrogen prepared with water as raw material is high based on the high selectivity of the reaction, but it requires external energy such as applying voltage or photolysis of water to achieve this.

[0003] With the increasing maturity of photovoltaic power generation, wind power generation, hydropower generation and other technologies, the sources of electricity are becoming more and more extensive, and the cost is gradually decreasing. The use of water electrolysis to produce hydrogen is a green and ideal hydrogen production technology. Water electrolysis consists of two half reactions, one is the hydrogen evolution reaction (HER) occurring at the cathode, and the other is the oxygen evolution reaction (OER) occurring at the anode. The two electrodes generate hydrogen and oxygen respectively, and can also be assembled into fuel cells to achieve clean power generation.

[0004] PEM electrolyzers need to be resistant to potential corrosion in highly acidic and high-pressure, high-purity hydrogen environments. Titanium is usually used, but titanium is easily penetrated and absorbed by hydrogen under the action of hydrogen, resulting in an increase in the hydrogen content inside the material, which in turn causes hydrogen embrittlement. Figure 1 As shown in the figure, when hydrogen embrittlement occurs in a material, hydrogen spontaneously dissociates, H atoms spontaneously enrich and diffuse to the surface / near the initial crack, and the interstitial H atoms cause the material lattice to expand / form hydrides. When H is introduced to the interface, the surface energy and fracture energy are greatly reduced, thereby promoting the formation of fractures, resulting in reduced ductility and toughness of metal materials, and even material fracture and failure. Therefore, it is necessary to develop materials with good resistance to hydrogen embrittlement.

[0005] Nickel alloys have excellent resistance to hydrogen embrittlement and are widely used in equipment and devices in high hydrogen environments. However, in the high-temperature acidic corrosion environment and the coupling of electrochemical corrosion in PEM electrolytic cells, nickel alloy coatings are often corroded by acid and lost. The development of hydrogen embrittlement-resistant alloy coatings requires a deep understanding of the hydrogen embrittlement phenomenon and the characteristics of nickel alloy materials. In the prior art, patent document CN118345332A discloses a hydrogen embrittlement-resistant nickel alloy coating and its preparation process. The intermediate layer of the coating is at least one of a molybdenum alloy, a chromium alloy, a manganese alloy, a niobium alloy, a copper alloy, and an aluminum alloy, and the surface layer is a nickel alloy. It can be applied to the surface of various metal materials to reduce the occurrence of hydrogen embrittlement and effectively prevent hydrogen and corrosive media from corroding the metal surface. Patent document CN117568838A discloses a PEM electrolytic cell bipolar plate and a preparation method thereof. A pure carbon coating having conductivity, corrosion resistance and hydrogen embrittlement resistance is provided on the cathode surface of the bipolar plate substrate, which can prevent the corrosive medium from penetrating into the bipolar plate substrate, enhance the corrosion resistance of the substrate, and prevent the substrate from hydrogen embrittlement which leads to a decrease in mechanical properties. At the same time, it effectively reduces the contact resistance between the bipolar plate and the porous transmission layer and carbon paper. However, the existing technology still has the following problems: 1) The bipolar plate coating is mostly prepared by electroplating process, in which a layer of platinum is electroplated on the surface of the bipolar plate, which is costly and the coating thickness is usually less than 1μm, resulting in the inability to form a dense coverage of the substrate, and hydrogen embrittlement corrosion will still occur on the cathode surface of the bipolar plate; 2) Nickel alloy coatings have corrosion problems in acidic environments. Single material nickel has the characteristic of strong catalytic decomposition of hydrogen into atoms, and essentially fails to resist hydrogen atoms for the substrate; 3) Carbon coatings still have major corrosion problems under the cathode environment and potential, and the internal stress of carbon materials is easily stimulated in a high-pressure hydrogen environment, and the thermal expansion coefficient is greatly different from that of metal materials, and film collapse problems are easily caused after high and low temperature changes. Summary of the invention

[0006] In order to solve the following problems existing in the bipolar plates of PEM electrolyzers in the prior art: 1) there is great corrosion in a high-temperature acidic potential environment; 2) hydrogen embrittlement of the material in a high-pressure hydrogen environment; 3) large contact resistance between the cathode plate and the carbon paper or titanium felt; and 4) poor stability due to the thermal expansion coefficient of the substrate, which affects the service life, the main purpose of the present invention is to provide a hydrogen embrittlement-resistant composite coating for bipolar plates of PEM electrolyzers, which realizes the hydrogen barrier effect by designing a three-layer coating structure and combining the three methods of inhibiting hydrogen decomposition, reducing hydrogen diffusion and adsorption and fixation.

[0007] Another object of the present invention is to provide a method for preparing the hydrogen embrittlement resistant composite coating.

[0008] Another object of the present invention is to provide a bipolar plate for a PEM electrolyzer.

[0009] To achieve the above object, the present invention is implemented through the following technical solutions:

[0010] The present invention provides a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer, comprising a hydrogen-fixing bottom layer, a hydrogen-blocking layer and a hydrogen-dissociation-inhibiting conductive outer layer sequentially formed on the surface of a bipolar plate substrate of the PEM electrolyzer;

[0011] The material of the hydrogen solidifying bottom layer includes one or more of lanthanum (La), cerium (Ce), nickel (Ni), cobalt (Co), manganese (Mn), aluminum (Al) and their alloys and oxides, zirconium-based alloys and their oxides, titanium-based alloys and their oxides, and magnesium-based alloys and their oxides;

[0012] The material of the hydrogen barrier layer includes one or more of W, Be, W-Be alloy, metal nitride, metal carbide, and metal oxide, and the hydrogen diffusion coefficient is less than 10 -14 mol / s / m / Pa 0.5 ;

[0013] The material of the hydrogen dissociation inhibiting conductive outer layer includes one or more of Ag, Au, Cu-Ag alloy, and Cu-Au alloy, and the hydrogen dissociation energy thereof is greater than 0.1 eV.

[0014] Preferably, the zirconium-based alloy is selected from one or more of zirconium-vanadium alloy (ZrV2), zirconium-chromium alloy (ZrCr2), and zirconium-manganese alloy (ZrMn2);

[0015] and / or the titanium-based alloy is selected from titanium-nickel alloy (TiNi) and / or iron-titanium alloy (FeTi);

[0016] And / or the magnesium-based alloy is a magnesium-nickel alloy (Mg2Ni).

[0017] Preferably, the metal nitride is selected from one or more of TiAlN, WN, CrWN, CrN, and ZrN;

[0018] And / or the metal carbide is selected from one or more of TiC, TiN-TiC, and SiC;

[0019] And / or the metal oxide is selected from one or more of Y2O3, Al2O3, and Er2O3.

[0020] Preferably, the thickness of the hydrogen solid bottom layer is 100-120 nm;

[0021] And / or the thickness of the hydrogen barrier layer is 300-500 nm;

[0022] And / or the thickness of the hydrogen dissociation inhibiting conductive outer layer is 10-30 nm.

[0023] The present invention also provides a method for preparing the anti-hydrogen embrittlement composite coating, comprising the following steps:

[0024] (1) Preparation of a solid hydrogen base layer: Forming a highly bonded solid hydrogen base layer on the surface of the bipolar plate substrate of a PEM electrolyzer by physical vapor deposition or electroplating impact;

[0025] (2) preparing a hydrogen barrier layer: forming a hydrogen barrier layer on the surface of the solid hydrogen bottom layer by physical vapor deposition, and adjusting the growth orientation of the material in the hydrogen barrier layer by bias voltage to form a dense and intricate branch network for blocking the diffusion of hydrogen atoms;

[0026] (3) Preparing a conductive outer layer for inhibiting hydrogen dissociation: forming a dense conductive outer layer for inhibiting hydrogen dissociation on the surface of the hydrogen barrier layer by physical vapor deposition under high vacuum conditions.

[0027] Preferably, the method further comprises the step of ultrasonically cleaning the bipolar plate substrate of the PEM electrolyzer before preparing the hydrogen solidifying bottom layer.

[0028] Preferably, the physical vapor deposition includes one or more of magnetron sputtering, evaporation, and multi-arc ion plating.

[0029] Preferably, the process parameters of the physical vapor deposition include: a deposition current of 0.5 to 5 A, a deposition time of 10 to 30 min, a deposition bias of -300 to -700 V, a deposition temperature of 200 to 500 °C, and a vacuum degree of 1 to 5 Pa.

[0030] More preferably, in step (2), the physical vapor deposition adopts a multi-layer bias combination, and the process includes: under vacuum conditions, first controlling the deposition current to 5 A, the deposition temperature to 500 ° C, the deposition time to 30 min and the deposition bias to -300 V, and then controlling the deposition current to 2 A, the deposition temperature to 500 ° C, the deposition time to 30 min and the deposition bias to -500 V, and alternately depositing for 5 to 10 cycles.

[0031] The present invention also provides a PEM electrolyzer bipolar plate, which uses pure titanium or titanium alloy as the PEM electrolyzer bipolar plate substrate, and also includes the anti-hydrogen embrittlement composite coating, which is formed on the surface of the PEM electrolyzer bipolar plate substrate by physical vapor deposition.

[0032] Compared with the prior art, the present invention proposes a hydrogen embrittlement resistant composite coating for bipolar plates of PEM electrolyzers, which realizes the hydrogen barrier effect by designing a three-layer coating structure, combining the three methods of inhibiting hydrogen decomposition, reducing hydrogen diffusion and adsorption and fixation. The hydrogen dissociation inhibiting conductive outer layer is used to inhibit hydrogen dissociation and has a high conductivity to meet the cathode conductivity requirements in the PEM electrolyzer. The hydrogen barrier layer is used to reduce the diffusion of hydrogen atoms to the substrate. The hydrogen-fixing bottom layer is used to adsorb and fix hydrogen, adsorb the diffused hydrogen to reduce its diffusion to the upper end of the substrate, and realize the protection of the substrate. Specifically, the beneficial effects of the present invention are at least:

[0033] (1) The hydrogen embrittlement resistant composite coating of the present invention has good stability under the action of acidity and potential, and can effectively solve the problem of conductivity and corrosion resistance of the bipolar plate of the PEM electrolyzer.

[0034] (2) The anti-hydrogen embrittlement composite coating of the present invention combines three methods: inhibiting hydrogen decomposition, reducing hydrogen diffusion, and adsorbing and fixing hydrogen, thereby protecting the plate substrate in acidic and high-pressure and high-purity hydrogen environments, thereby improving the stability and service life of the PEM electrolyzer.

[0035] (3) The materials used in the present invention are mostly non-precious metal materials, such as metal oxides, metal nitrides, metal carbides, or highly corrosion-resistant metals and their alloys that are relatively stable in acidic environments, which can meet the requirements of corrosion resistance under acidic high-temperature potentials and strong bonding performance between the coating and the titanium substrate. In addition, the thickness of the precious metal Au used in the outer layer is relatively low, which can greatly reduce the cost compared to the commercial electroplated 500nm platinum coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the process of hydrogen embrittlement of titanium material used in PEM electrolyzers in the prior art.

[0037] Figure 2 Schematic diagram of the structure of the hydrogen embrittlement resistant composite coating used for the bipolar plate of the PEM electrolyzer in the embodiment.

[0038] Figure 3 These are the offline hydrogen diffusion coefficient test results for titanium substrate, titanium substrate + electroplated 500nm platinum, and titanium substrate + anti-hydrogen embrittlement composite coating prepared in Example 1. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention is clearly and completely described below. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In the following embodiments, a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer is proposed, comprising a hydrogen solidifying bottom layer, a hydrogen barrier layer, and a conductive outer layer for inhibiting hydrogen dissociation, which are sequentially formed on the surface of a substrate of a bipolar plate of a PEM electrolyzer; wherein the material of the hydrogen solidifying bottom layer can be selected from La, Ce, Ni, Co, Mn, Al, and their alloys and oxides, zirconium-based alloys and their oxides, titanium-based alloys and their oxides, and magnesium-based alloys and their oxides; the material of the hydrogen barrier layer can be selected from W, Be, W-Be alloy, metal nitride, metal carbide, and metal oxide, and the hydrogen diffusion coefficient is less than 10 -14 mol / s / m / Pa0.5 The material of the conductive outer layer that inhibits hydrogen dissociation can be selected from Ag, Au, Cu-Ag alloy or Cu-Au alloy, and its hydrogen dissociation energy is greater than 0.1 eV.

[0041] In some embodiments, the zirconium-based alloy may be ZrV2, ZrCr2 or ZrMn2. In some embodiments, the titanium-based alloy may be TiNi or FeTi. In some embodiments, the magnesium-based alloy may be Mg2Ni. In some embodiments, the metal nitride may be TiAlN, WN, CrWN, CrN, ZrN. In some embodiments, the metal carbide may be TiC, TiN-TiC, SiC. In some embodiments, the metal oxide may be Y2O3, Al2O3, Er2O3.

[0042] In some embodiments, the thickness of the hydrogen solidifying bottom layer is 100-120 nm; in some embodiments, the thickness of the hydrogen blocking layer is 300-500 nm; in some embodiments, the thickness of the hydrogen dissociation inhibiting conductive outer layer is 10-30 nm.

[0043] The preparation method of the hydrogen embrittlement resistant composite coating in the following embodiment comprises the following steps:

[0044] (1) Forming a highly bonded hydrogen-solidified bottom layer on the surface of the bipolar plate substrate of the PEM electrolyzer by physical vapor deposition or electroplating impact;

[0045] (2) Forming a hydrogen barrier layer on the surface of the solid hydrogen bottom layer by physical vapor deposition, and adjusting the growth orientation of the material in the hydrogen barrier layer by bias voltage to form a dense and intricate branch network to block the diffusion of hydrogen atoms;

[0046] (3) Under high vacuum conditions, a dense conductive outer layer that inhibits hydrogen dissociation is formed on the surface of the hydrogen barrier layer by physical vapor deposition.

[0047] In some embodiments, the bipolar plate substrate of the PEM electrolyzer is ultrasonically cleaned before preparing the hydrogen solidifying bottom layer.

[0048] In some embodiments, physical vapor deposition may be performed by magnetron sputtering, evaporation, or multi-arc ion plating.

[0049] In some embodiments, the process parameters of physical vapor deposition include: a deposition current of 0.5 to 5 A, a deposition time of 10 to 30 min, a deposition bias of -300 to -700 V, a deposition temperature of 200 to 500 °C, and a vacuum degree of 1 to 5 Pa.

[0050] In some embodiments, physical vapor deposition uses a multi-layer bias combination to prepare a hydrogen barrier layer, and the process includes: under vacuum conditions, first controlling the deposition current to 5 A, the deposition temperature to 500 ° C, the deposition time to 30 min, and the deposition bias to -300 V, and then controlling the deposition current to 2 A, the deposition temperature to 500 ° C, the deposition time to 30 min, and the deposition bias to -500 V, and alternating the deposition for 5 to 10 cycles. Example 1

[0051] In this embodiment, a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer is prepared, and the steps are as follows:

[0052] (1) Select pure titanium with uniform thickness as the plate substrate and perform ultrasonic cleaning in ethanol and water to remove grease and debris on the surface.

[0053] (2) Fix pure titanium to the electrode clamp and immerse it in an acidic solution of Mg(NO3)2+Ni2SO4, where the molar ratio of Mg:Ni is 2:1, the immersion time is 4 hours, the positive electrode is a graphite rod, the negative electrode is a pure titanium substrate, the deposition current is controlled to be 0.5A, the deposition time is 30 minutes, and after the deposition is completed, it is dried to obtain Mg-NiO x The solid hydrogen bottom layer (adsorption layer) has a thickness of 100nm.

[0054] (3) Fix the material obtained in step (2) on a rack, move it into a closed reaction chamber and evacuate it. When the vacuum is evacuated to 1 Pa, turn on the heater and heat it to 500°C. Keep it warm for a period of time. Then, introduce reaction gases Ar, O2 and N2 into the chamber through the gas path and the air hole to control the Ti-Al alloy target. The vacuum degree is controlled to be 5 Pa through the exhaust system. First, the deposition current is controlled to be 5A at a deposition temperature of 500°C, the deposition time is 30min, and the deposition bias is -300V. Then, the deposition current is controlled to be 2A at a deposition temperature of 500°C, the deposition time is 30min, and the deposition bias is -500V. Alternate deposition is performed for 5 cycles. The penetration path is reduced by a multi-layer bias combination. The layer is gradually cooled to room temperature to obtain a TiAlN hydrogen barrier layer (hydrogen barrier layer) with a thickness of 300nm.

[0055] (4) The material obtained in step (3) is fixed on a rack, moved into a closed reaction chamber and evacuated. When the vacuum is evacuated to 1 Pa, the heater is turned on to heat to 500°C and kept warm for a period of time. Then, the reaction gas Ar is introduced into the chamber through the gas path and the air hole. The Au target material is controlled, the deposition current is controlled to 0.5 A, and the deposition time is 10 min to obtain a conductive outer layer (surface layer) that inhibits hydrogen dissociation, with a thickness of 20 nm.

[0056] The structure of the anti-hydrogen embrittlement composite coating prepared in this embodiment is as follows: Figure 2 shown.

[0057] The performance of pure titanium substrate, pure titanium substrate + electroplated 500 nm platinum coating and pure titanium substrate + anti-hydrogen embrittlement composite coating in this embodiment were tested. The results are as follows Figure 3 As shown. A hydrogen diffusion electrochemical test method is used, specifically: the electrochemical hydrogen permeation test introduces hydrogen into the metal through an applied potential, or exposes the metal sample to an environment containing hydrogen, simulating the penetration process of hydrogen in the metal. Over time, hydrogen atoms will gradually diffuse into the metal lattice and form hydrogen atom clusters or hydrides inside the metal. When hydrogen diffuses and aggregates in the metal, electron flow will occur, forming the so-called hydrogen permeation current. By recording the changes in these currents, mainly the time when the current density rises and the current density range, the diffusion rate, degree of diffusion and aggregation of hydrogen in the metal are analyzed. The test reference is as follows, based on the PEM electrolytic cell environment: the cathode is an acidic pH3+70℃ environment, the anode is an alkaline environment, and the test samples are pure titanium substrate, pure titanium substrate + electroplated 500 nm platinum coating and pure titanium substrate + anti-hydrogen embrittlement composite coating in this embodiment.

[0058] like Figure 3 As shown in the figure, under the same conditions, the pure titanium substrate + anti-hydrogen embrittlement composite coating did not diffuse hydrogen through the plate, resulting in an increase in current density. The penetration time (t b )>24h, pure titanium substrate, pure titanium substrate + electroplated 500 nm platinum coating b The electroplated 500 nm platinum coating has a certain improvement over the pure substrate, but it cannot essentially prevent hydrogen diffusion. The hydrogen embrittlement-resistant composite coating prepared in this example has a good effect under the same conditions. b >24h, there is absolutely no hydrogen diffusion, which directly and effectively proves the protection of the anti-hydrogen embrittlement composite coating on the substrate. Example 2

[0059] In this embodiment, a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer is prepared, and the steps are as follows:

[0060] (1) Select titanium alloy with uniform thickness as the plate substrate and perform ultrasonic cleaning in ethanol and water to remove grease and debris on the surface.

[0061] (2) The titanium alloy was fixed to the electrode clamp and immersed in an acidic solution of Ni2SO4 for 4 h. The positive electrode was a Fe rod and the negative electrode was a titanium alloy substrate. The deposition current was controlled to be 2.5 A and the deposition time was 10 min. After the deposition was completed, it was dried to obtain Ni-FeO x Solid hydrogen bottom layer, thickness is 120 nm.

[0062] (3) Fix the material obtained in step (2) on a rack, move it into a closed reaction chamber and evacuate it. When the vacuum is evacuated to 1 Pa, turn on the heater to heat it to 500 °C and keep it warm for a period of time. Then, introduce reaction gases Ar, O2 and N2 into the chamber through the gas path and the air hole to control the Fe-Cr-Ni alloy target. The vacuum degree is controlled to be 5 Pa through the exhaust system. First, the deposition current is controlled to be 2 A at a deposition temperature of 500 °C, the deposition time is 30 min, and the deposition bias is -500 V. Then, the deposition current is controlled to be 5 A at a deposition temperature of 500 °C, the deposition time is 30 min, and the deposition bias is -120 V. Alternate deposition is performed for 9 cycles. The penetration path is reduced by a multi-layer bias combination. The mixture is gradually cooled to room temperature to obtain FeO x -CrO x Hydrogen barrier layer, thickness is 500nm.

[0063] (4) The material obtained in step (3) is fixed on a rack, moved into a closed reaction chamber and evacuated. When the vacuum is evacuated to 1 Pa, the heater is turned on to heat to 500 °C and kept warm for a period of time. Then, the reaction gas Ar is introduced into the chamber through the gas path and the air hole. The Cu-Ag target is controlled, the deposition current is controlled to 1.5 A, and the deposition time is 10 min. A conductive outer layer that inhibits hydrogen dissociation is obtained, with a thickness of 30 nm. Example 3

[0064] In this embodiment, a hydrogen embrittlement resistant composite coating for a bipolar plate of a PEM electrolyzer is prepared, and the steps are as follows:

[0065] (1) Select titanium alloy with uniform thickness as the plate substrate and perform ultrasonic cleaning in ethanol and water to remove grease and debris on the surface.

[0066] (2) Fix the titanium alloy on the rack, move it into the closed reaction chamber and evacuate it. When the vacuum is evacuated to 0.1 Pa, turn on the heater and heat it to 200 °C and keep it warm for a while. Then, introduce the reaction gases Ar and O2 into the chamber through the gas path and the air hole. Control the Ce-Co alloy target (the proportion of Co is 5%), the deposition current is 1.0 A, the deposition time is 10 min, the deposition bias is -700 V, and after the deposition is completed, dry it to obtain Co-CeO x Solid hydrogen bottom layer, thickness is 100nm.

[0067] (3) Fix the material obtained in step (2) on a rack, move it into a closed reaction chamber and evacuate it. When the vacuum is evacuated to 1 Pa, turn on the heater and heat it to 500 °C and keep it warm for a period of time. Then, introduce reaction gases Ar, O2 and N2 into the chamber through the gas path and the air hole to control the metal Al target material, and control the vacuum degree to 5 Pa through the exhaust system. First, control the deposition current to 2 A at a deposition temperature of 500 °C, the deposition time to 30 min, and the deposition bias to -500 V. Then, control the deposition current to 5 A at a deposition temperature of 500 °C, the deposition time to 30 min, and the deposition bias to -120 V. Alternate deposition is performed for 7 cycles. The penetration path is reduced by a multi-layer bias combination. The chamber is gradually cooled to room temperature to obtain an Al2O3 hydrogen barrier layer (hydrogen barrier layer) with a thickness of 300 nm.

[0068] (4) The material obtained in step (3) is fixed on a rack, moved into a closed reaction chamber and evacuated. When the vacuum is evacuated to 1 Pa, the heater is turned on to heat to 500 °C and kept warm for a period of time. Then, the reaction gas Ar is introduced into the chamber through the gas path and the air hole. The Ag target is controlled, the deposition current is controlled to 0.5 A, and the deposition time is 10 min to obtain a conductive outer layer that inhibits hydrogen dissociation, with a thickness of 10 nm.

[0069] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A hydrogen embrittlement resistant composite coating for bipolar plates of PEM electrolyzers, characterized in that: The anti-hydrogen embrittlement composite coating comprises a hydrogen-solidifying bottom layer, a hydrogen-blocking layer and a hydrogen-dissociation-inhibiting conductive outer layer sequentially formed on the surface of the bipolar plate substrate of the PEM electrolyzer; wherein: The hydrogen-solidifying bottom layer is Mg-NiO x Hydrogen-fixing bottom layer; The hydrogen barrier layer is a TiAlN hydrogen barrier layer; The material of the hydrogen dissociation inhibiting conductive outer layer is Au, and the hydrogen dissociation energy is greater than 0.1 eV.

2. The anti-hydrogen embrittlement composite coating according to claim 1, characterized in that: The thickness of the hydrogen solid bottom layer is 100-120 nm; And / or the thickness of the hydrogen barrier layer is 300-500 nm; And / or the thickness of the hydrogen dissociation inhibiting conductive outer layer is 10-30 nm.

3. The method for preparing the hydrogen embrittlement resistant composite coating according to claim 1 or 2, characterized in that: The following steps are involved: (1) Preparation of a solid hydrogen base layer: forming a solid hydrogen base layer on the surface of the bipolar plate substrate of a PEM electrolyzer by physical vapor deposition or electroplating impact; (2) preparing a hydrogen barrier layer: forming a hydrogen barrier layer on the surface of the solid hydrogen bottom layer by physical vapor deposition, and adjusting the growth orientation of the material in the hydrogen barrier layer by bias voltage to form a dense and intricate branch network for blocking the diffusion of hydrogen atoms; (3) Preparing a conductive outer layer for inhibiting hydrogen dissociation: forming a conductive outer layer for inhibiting hydrogen dissociation on the surface of the hydrogen barrier layer by physical vapor deposition under high vacuum conditions.

4. The method for preparing the hydrogen embrittlement resistant composite coating according to claim 3, characterized in that: The method also includes the step of ultrasonically cleaning the bipolar plate substrate of the PEM electrolyzer before preparing the hydrogen solidifying bottom layer.

5. The method for preparing the hydrogen embrittlement resistant composite coating according to claim 3, characterized in that: The physical vapor deposition is selected from one or more of magnetron sputtering, evaporation, and multi-arc ion plating.

6. The method for preparing the hydrogen embrittlement resistant composite coating according to claim 3, characterized in that: The process parameters of the physical vapor deposition include: deposition current of 0.5~5 A, deposition time of 10~30 min, deposition bias of -300~-700 V, deposition temperature of 200~500 °C, and vacuum degree of 1~5 Pa.

7. The method for preparing the hydrogen embrittlement resistant composite coating according to claim 6, characterized in that: In step (2), the physical vapor deposition adopts a multi-layer bias combination, and the process includes: under vacuum conditions, first controlling the deposition current to 5 A, the deposition temperature to 500 ° C, the deposition time to 30 min and the deposition bias to -300 V, and then controlling the deposition current to 2 A, the deposition temperature to 500 ° C, the deposition time to 30 min and the deposition bias to -500 V, and alternately depositing for 5 to 10 cycles.

8. A bipolar plate for a PEM electrolyzer, characterized in that: Pure titanium or titanium alloy is used as the bipolar plate substrate of the PEM electrolyzer, and also includes the anti-hydrogen embrittlement composite coating according to claim 1 or 2, which is formed on the surface of the bipolar plate substrate of the PEM electrolyzer by physical vapor deposition.

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