Preparation method for surface protective coating of anode diffusion layer of PEM electrolytic cell for hydrogen production by electrolysis of water

Abstract

The invention belongs to the technical field of porous diffusion layer coatings in PEM water electrolysis hydrogen production, and particularly relates to a preparation method of a surface protective coating for an anode diffusion layer of an electrolytic cell for PEM water electrolysis hydrogen production. The surface of a substrate is coated with the prepared coating liquid, and sintering is carried out after drying and illumination to form a protective layer. The prepared coating liquid is brushed on the surface of an anode diffusion layer titanium substrate to form a protective layer, the contact resistance of the titanium substrate can be reduced, the overall conductivity of the material is improved, then the electrolytic performance of a PEM electrolytic bath is improved, the protective layer can enable the anode diffusion layer to have high corrosion resistance, and therefore the use cost of the anode diffusion layer is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of porous diffusion layer coatings in PEM water electrolysis hydrogen production, and in particular relates to a method for preparing a protective coating on the surface of an anode diffusion layer of an electrolytic cell for PEM water electrolysis hydrogen production. Background Art

[0002] PEM water electrolysis has the characteristics of balanced and outstanding performance indicators, and is suitable for various scenarios, including industrial hydrogen production, portable hydrogen production, and dynamic loads used as grid amplitude modulation. In the 21st century, with the increase in demand for clean energy and the tightening of global restrictions on greenhouse gas emissions, the demand for water electrolysis has increased significantly. With the continuous advancement of PEM water electrolysis technology and the reduction of costs, pressure-type PEM water electrolysis is expected to play a more important role in the hydrogen energy industry, especially in terms of coupling with renewable energy, and contribute to energy transformation and greenhouse gas emission reduction. At the same time, related companies and research institutions are also constantly working to overcome the technical difficulties encountered by PEM electrolyzers and improve their performance and market competitiveness.

[0003] The components of PEM electrolyzer include: bipolar plates, anode and cathode gas diffusion layers, anode and cathode catalyst layers and proton exchange membranes; although PEM electrolyzers have many advantages, there are still some technical problems in practical applications, mainly including: my country currently relies entirely on imports for gas diffusion layers, which are relatively costly and mainly concentrated on the anode side of the electrolyzer. The anode potential is higher than that of the cathode, and carbon materials are easily oxidized. The formation of oxides will increase the surface contact resistance. Therefore, it is necessary to prepare a coating on the surface of the anode gas diffusion layer to optimize the conductivity and corrosion resistance of the anode gas diffusion layer, which has become an urgent problem to be solved. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a protective coating on the surface of the anode diffusion layer of a PEM water electrolysis hydrogen production electrolyzer. By preparing the protective coating on the surface of the anode diffusion layer, the anode diffusion layer has excellent conductivity and high corrosion resistance, thereby reducing the cost of use.

[0005] In order to achieve the above object, the present invention provides a method for preparing a protective coating on the surface of an anode diffusion layer of a PEM electrolytic cell for producing hydrogen by electrolysis of water, wherein the anode diffusion layer uses a porous titanium material as a substrate, and the preparation method comprises the following steps:

[0006] Step 1, pretreatment of the titanium substrate: polishing, ultrasonic degreasing, alkali washing, and drying the titanium substrate in sequence;

[0007] Step 2, preparing an intermediate active layer: placing the titanium substrate pretreated in step 1 in a mixed acid solution, and sealing and preserving it for a certain period of time, so that an active layer grows in situ on the surface of the titanium substrate; the mixed acid solution is any one or a combination of hydrofluoric acid, sulfuric acid, and oxalic acid solution;

[0008] Step 3, preparing a coating solution: dissolving a platinum compound in a solvent, and then adding polyurethane acrylate, hydroxyethyl methacrylate, and isopropyl benzoate to mix; the platinum compound is any one or a combination of chloroplatinic acid, potassium chloroplatinate, and P salt; the solvent is any one or a combination of water, ethanol, methanol, isopropanol, and n-butanol;

[0009] Step 4, preparing a protective layer: coating the coating liquid prepared in step 3 on the surface of the titanium substrate with the intermediate active layer prepared in step 2, drying and irradiating with light, and then sintering.

[0010] Preferably, in step 1, the polishing conditions of the titanium substrate are: the fluid temperature is 40° C., the pressure is 1 MPa; and the surface roughness Ra is ≤ 1 μm after polishing.

[0011] Preferably, in step 1, the ultrasonic degreasing process is: using a metal cleaning agent to perform cleaning at a temperature of 50° C. and a cleaning time of 30 minutes.

[0012] Preferably, in step 1, the specific process of alkaline washing is: placing the deoiled titanium substrate in a 5% sodium hydroxide solution for 3 hours, then washing it three times with pure water, and taking it out to dry after the impurity elements on the surface of the titanium substrate are completely removed.

[0013] Preferably, the components in the mixed acid solution are calculated by mass percentage: hydrofluoric acid accounts for 0-10%, sulfuric acid accounts for 0-20%, and oxalic acid accounts for 0-15%.

[0014] Preferably, in step 2, the main component of the intermediate active layer is a compound of titanium and one or more non-metallic elements of oxygen, fluorine, sulfur and carbon.

[0015] Preferably, in step 3, the mass fraction of the platinum compound added is 0.001% to 5% based on the platinum content, and the mass fractions of the polyurethane acrylate, hydroxyethyl methacrylate, and benzoin isopropyl ether added are 0.1% to 10%, 0.1% to 20%, and 0.1% to 10%, respectively.

[0016] Preferably, in step 4, the specific process flow for preparing the protective layer is:

[0017] 4.1) Drying the titanium substrate coated with the coating liquid at a temperature of 50°C to 250°C, then curing it under light for 1min to 10h, and then cleaning the uncured coating liquid in the hole;

[0018] 4.2) Sintering the titanium substrate treated in step 4.1) at 300°C to 650°C for 10 min to 10 h, taking it out and cooling it to room temperature for the next coating, repeating the above step 4.1) until the platinum content in the prepared protective layer reaches the requirement;

[0019] 4.3) When the coating liquid in step 4.2) is applied to the last coat, sintering is carried out at 300°C to 650°C for 1h to 24h, and then the desired protective layer is obtained by cooling to room temperature after taking out.

[0020] Preferably, the step 4.1) is cleaned with a 1% aqueous solution of tetramethylammonium hydroxide, and then cleaned with pure water and dried for later use.

[0021] The beneficial effects of the present invention are:

[0022] (1) The protective layer formed by brushing the coating liquid prepared in the present invention on the surface of the titanium substrate of the anode diffusion layer can reduce the contact resistance of the titanium substrate, increase the overall conductivity of the material, and thus improve the electrolytic performance of the PEM electrolyzer. The protective layer can make the anode diffusion layer have high corrosion resistance, and the precious metal conductive coating only exists on the surface of the porous titanium substrate in conductive contact, and there is no coating inside the pores. The gas-liquid transmission is good, and the electrode activity and stability are not affected, thereby reducing its use cost;

[0023] (2) The in-situ growth of an intermediate active layer on the surface of the titanium substrate can effectively prevent the oxidation of the titanium substrate in the air and enhance the bonding strength between the protective layer on the surface of the titanium substrate and the titanium substrate. The processing process is simple, the preparation speed is fast, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The present invention discloses a process flow for preparing the surface protective layer of the anode diffusion layer.

[0025] Figure 2 It is a performance comparison chart of the electrolytic cells of Examples 1-4 of the present invention and the comparative example. DETAILED DESCRIPTION

[0026] The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. The reagents used therein should be understood to be conventional commercial reagents or prepared according to the prior art unless otherwise specified; the operating methods used therein should be understood to be conventional operations in the art unless otherwise specified.

[0027] like Figure 1 and Figure 2 As shown, the method for preparing the protective coating on the surface of the anode diffusion layer of the PEM electrolytic cell for producing hydrogen by electrolysis of water is provided in an embodiment of the present invention. The anode diffusion layer adopts a porous titanium material as a substrate. The preparation method comprises the following steps:

[0028] Step 1, titanium substrate pretreatment: polishing, ultrasonic degreasing, alkali washing, and air-drying the titanium substrate in sequence; wherein, the polishing conditions of the titanium substrate are: the fluid temperature is 40°C and the pressure is 1Mpa; the surface roughness Ra is ≤ 1μm after polishing; the ultrasonic degreasing process is: using a metal cleaning agent to clean at a temperature of 50°C and a cleaning time of 30min; the specific process of alkali washing is: placing the degreased titanium substrate in a 5% sodium hydroxide solution for 3h, and then washing it with pure water three times, and after the impurity elements on the surface of the titanium substrate are completely removed, take it out and dry it for use;

[0029] Step 2, preparing an intermediate active layer: placing the titanium substrate pretreated in step 1 in a mixed acid solution, and sealing and preserving it for a certain period of time, an active layer is grown in situ on the surface of the titanium substrate; the mixed acid solution is any one or a combination of hydrofluoric acid, sulfuric acid, and oxalic acid solutions; the components in the mixed acid solution are calculated by mass percentage, with hydrofluoric acid accounting for 0-10%, sulfuric acid accounting for 0-20%, and oxalic acid accounting for 0-15%; the main components of the intermediate active layer are compounds of titanium and single or multiple non-metallic elements of oxygen, fluorine, sulfur, and carbon; the growth time of the intermediate active layer is 5 minutes to 24 hours.

[0030] Step 3, preparing a coating solution: dissolving a platinum compound in a solvent, and then adding polyurethane acrylate, hydroxyethyl methacrylate, and isopropyl benzoate to mix well; the platinum compound is any one or a combination of chloroplatinic acid, potassium chloroplatinate, and P salt; the solvent is any one or a combination of water, ethanol, methanol, isopropanol, and n-butanol;

[0031] In the present invention, the mass fraction of the added platinum compound is 0.001% to 5% based on the platinum content, and the mass fractions of the added polyurethane acrylate, hydroxyethyl methacrylate, and benzoin isopropyl ether are 0.1% to 10%, 0.1% to 20%, and 0.1% to 10%, respectively.

[0032] Step 4, prepare a protective layer: use a wool brush to evenly apply the coating liquid prepared in step 3 to the surface of the porous titanium substrate where the intermediate active layer is prepared in step 2, then dry it at a temperature of 50°C to 250°C, and then expose it to a high-pressure mercury lamp ultraviolet light source for 1min to 10h for curing, and then clean the uncured coating liquid in the hole; use a 1% tetramethylammonium hydroxide aqueous solution to wash three times and then use pure water to wash three times to dry; place it in a sintering furnace, keep it at 300°C to 650°C for 10min to 10h for sintering, take it out and wait for it to cool to room temperature for the next brushing, repeat the above brushing process until the platinum content in the prepared protective layer reaches 0.04g-0.11g; when the coating liquid is brushed to the last time, keep it at 300°C to 650°C for 1h to 24h for sintering, take it out and cool it to room temperature to obtain the desired protective layer.

[0033] In the present invention, an intermediate active layer is in-situ grown on the surface of the titanium substrate, which can effectively prevent the oxidation of the titanium substrate in the air and enhance the bonding strength between the protective layer on the surface of the titanium substrate and the titanium substrate. The processing process is simple, the preparation speed is fast, and the cost is low.

[0034] Example 1

[0035] A method for preparing a protective coating on the surface of an anode diffusion layer of a PEM electrolytic cell for producing hydrogen by electrolysis of water, comprising the following steps:

[0036] Step 1, titanium substrate pretreatment: first polish the 100mm*100mm*1mm porous titanium substrate, keep the fluid temperature at 40°C and the polishing pressure at 1Mpa, until the roughness Ra≤1μm, then ultrasonically clean it at 50°C for 30min in a solution containing a metal cleaning agent, then soak it in a 5% sodium hydroxide solution for 3h, wash it three times with pure water, and then dry it for use;

[0037] Step 2, preparing the intermediate active layer: placing the titanium substrate pretreated in step 1 in an aqueous solution containing 10% hydrofluoric acid and 10% sulfuric acid, sealing and standing for 5 minutes, so that an active layer grows in situ on the surface of the titanium substrate, taking it out, washing it with pure water three times, and then drying it for later use;

[0038] Step 3, preparing a coating solution: adding 0.9 g of P salt, 1 g of polyurethane acrylate, 1 g of hydroxyethyl methacrylate, and 1 g of benzoin isopropyl ether in 1000 ml of pure water, and stirring all the ingredients evenly for use;

[0039] Step 4, prepare a protective layer: use a wool brush to evenly apply the coating prepared in step 3 to the surface of the porous titanium substrate where the intermediate active layer is prepared in step 2, then dry it at 50°C, and then expose it to a high-pressure mercury lamp ultraviolet light source for 10 hours for curing, then clean the uncured coating in the hole, wash it three times with a 1% tetramethylammonium hydroxide aqueous solution, and then wash it three times with pure water to dry, place it in a sintering furnace, keep it at 300°C for 10 hours for sintering, take it out and wait for it to cool to room temperature for the next coating; repeat the above-mentioned coating process until the platinum content in the prepared protective layer reaches 0.11g. When the coating is brushed to the last time, set 650°C in the sintering furnace for 1 hour for sintering, take it out and cool it to room temperature to obtain the desired protective layer.

[0040] Example 2

[0041] A method for preparing a protective coating on the surface of an anode diffusion layer of a PEM electrolytic cell for producing hydrogen by electrolysis of water, comprising the following steps:

[0042] Step 1, titanium substrate pretreatment: first polish the 100mm*100mm*1mm porous titanium substrate, keep the fluid temperature at 40°C and the polishing pressure at 1Mpa, until the roughness Ra≤1μm, then ultrasonically clean it at 50°C for 30min in a solution containing a metal cleaning agent, then soak it in a 5% sodium hydroxide solution for 3h, wash it three times with pure water, and then dry it for use;

[0043] Step 2, preparing the intermediate active layer: placing the titanium substrate pretreated in step 1 in an aqueous solution containing 5% hydrofluoric acid, 20% sulfuric acid and 9% oxalic acid, sealing and standing for 50 minutes, so that the intermediate active layer is in situ grown on the surface of the titanium substrate, taking it out, washing it with pure water three times and then drying it for use;

[0044] Step 3, prepare a coating solution of 5000 ml: ethanol: isopropanol: water = 1:3:1 mixed alcohol aqueous solution, add 0.05 g chloroplatinic acid, 166.4 g polyurethane acrylate, 416 g hydroxyethyl methacrylate, 416 g benzoin isopropyl ether based on the mass of platinum, stir all the ingredients evenly and set aside;

[0045] Step 4, prepare a protective layer: use a wool brush to evenly apply the coating prepared in step 3 to the surface of the porous titanium substrate where the intermediate active layer is prepared in step 2, then dry it at 250°C, and then expose it to a high-pressure mercury lamp ultraviolet light source for 1 minute for curing, then clean the uncured coating in the hole, wash it three times with a 1% tetramethylammonium hydroxide aqueous solution, and then wash it three times with pure water to dry, place it in a sintering furnace, keep it at 650°C for 10 minutes for sintering, take it out and wait for it to cool to room temperature for the next brushing; repeat the above brushing process until the platinum content in the prepared protective layer reaches 0.04g. When the coating is brushed to the last time, set 300°C in the sintering furnace for 24 hours for sintering, take it out and cool it to room temperature to obtain the desired protective layer.

[0046] Example 3

[0047] A method for preparing a protective coating on the surface of an anode diffusion layer of a PEM electrolytic cell for producing hydrogen by electrolysis of water, comprising the following steps:

[0048] Step 1, titanium substrate pretreatment: first polish the 100mm*100mm*1mm porous titanium substrate, keep the fluid temperature at 40°C and the polishing pressure at 1Mpa, until the roughness Ra≤1μm, then ultrasonically clean it at 50°C for 30min in a solution containing a metal cleaning agent, then soak it in a 5% sodium hydroxide solution for 3h, wash it three times with pure water, and then dry it for use;

[0049] Step 2, preparing the intermediate active layer: placing the titanium substrate pretreated in step 1 in an aqueous solution containing 5% sulfuric acid and 15% oxalic acid, sealing and standing for 24 minutes, so that the intermediate active layer is in situ grown on the surface of the titanium substrate, taking it out, washing it with pure water three times, and then drying it for later use;

[0050] Step 3, prepare a coating solution of 1000 ml: methanol: n-butanol: water = 0.2:4:0.8 mixed alcohol aqueous solution, add 0.9 g chloroplatinic acid, 83.2 g polyurethane acrylate, 0.832 g hydroxyethyl methacrylate, 0.832 g benzoin isopropyl ether in terms of platinum mass, stir all ingredients evenly and set aside;

[0051] Step 4, prepare a protective layer: use a wool brush to evenly apply the coating prepared in step 3 to the surface of the porous titanium substrate where the intermediate active layer is prepared in step 2, then dry it at 60°C, and then expose it to a high-pressure mercury lamp ultraviolet light source for 10 minutes for curing, then clean the uncured coating in the hole, wash it three times with a 1% tetramethylammonium hydroxide aqueous solution, and then wash it three times with pure water to dry, place it in a sintering furnace, keep it at 300°C for 60 minutes for sintering, take it out and wait for it to cool to room temperature for the next brushing; repeat the above brushing process until the platinum content in the prepared protective layer reaches 0.08g. When the coating is brushed to the last time, set 500°C in the sintering furnace for 1 hour for sintering, take it out and cool it to room temperature to obtain the desired protective layer.

[0052] Example 4

[0053] A method for preparing a protective coating on the surface of an anode diffusion layer of a PEM electrolytic cell for producing hydrogen by electrolysis of water, comprising the following steps:

[0054] Step 1, titanium substrate pretreatment: first polish the 100mm*100mm*1mm porous titanium substrate, keep the fluid temperature at 40°C and the polishing pressure at 1Mpa, until the roughness Ra≤1μm, then ultrasonically clean it at 50°C for 30min in a solution containing a metal cleaning agent, then soak it in a 5% sodium hydroxide solution for 3h, wash it three times with pure water, and then dry it for use;

[0055] Step 2, preparing the intermediate active layer: placing the titanium substrate pretreated in step 1 in an aqueous solution containing 3% oxalic acid and 7% hydrofluoric acid, sealing and standing for 5 minutes, so that the intermediate active layer is in situ grown on the surface of the titanium substrate, taking it out, washing it with pure water three times, and then drying it for use;

[0056] Step 3, prepare a coating liquid 2000 mL: add 0.8 potassium chloroplatinate, 24 g polyurethane acrylate, 192 g hydroxyethyl methacrylate, 48 g benzoin isopropyl ether to a mixed alcohol solution of ethanol: n-butanol: isopropanol = 3:5:2 based on the mass of platinum, stir all the ingredients evenly and set aside;

[0057] Step 4, prepare a protective layer: use a wool brush to evenly apply the coating prepared in step 3 to the surface of the porous titanium substrate where the intermediate active layer is prepared in step 2, then dry it at 80°C, and then expose it to a high-pressure mercury lamp ultraviolet light source for 3 hours for curing, then clean the uncured coating in the hole, wash it three times with a 1% tetramethylammonium hydroxide aqueous solution, and then wash it three times with pure water to dry, place it in a sintering furnace, keep it at 600°C for 10 minutes for sintering, take it out and wait for it to cool to room temperature for the next brushing; repeat the above brushing process until the platinum content in the prepared protective layer reaches 0.06g. When the coating is brushed to the last time, set 600°C in the sintering furnace for 1 hour for sintering, take it out and cool it to room temperature to obtain the desired protective layer.

[0058] Comparative Example

[0059] The comparative example is a porous titanium substrate without any treatment.

[0060] The contact resistance test was performed on the products of the above-mentioned embodiments 1 to 4 and the comparative example, and the results are shown in Table 1:

[0061] Table 1 Contact resistance test results of products of Examples 1 to 4 and Comparative Examples

[0062] Test subjects Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Contact resistance 0.32mΩ 0.95mΩ 0.45mΩ 0.76mΩ 3.98mΩ

[0063] The contact resistances of the titanium substrates with protective layers prepared in Examples 1-4 of the present invention and the titanium substrates of the comparative example are shown in Table 1. From the measured resistance data, it can be seen that the protective layer formed by brushing the coating liquid prepared in the present invention on the surface of the titanium substrate of the anode diffusion layer can reduce the contact resistance of the titanium substrate, and the level of the contact resistance is related to the platinum content in the protective layer. The higher the platinum content, the lower the contact resistance and the stronger its conductivity. The reduction in contact resistance increases the overall conductivity of the material, thereby improving the electrolytic performance of the PEM electrolytic cell, and the protective layer can make the titanium substrate have high corrosion resistance, thereby reducing its use cost.

Claims

1. A method for preparing a protective coating on the surface of an anode diffusion layer of a PEM electrolytic cell for producing hydrogen by electrolysis of water, wherein the anode diffusion layer uses a porous titanium material as a matrix, characterized in that: The preparation method comprises the following steps: Step 1, pretreatment of the titanium substrate: polishing, ultrasonic degreasing, alkali washing, and drying the titanium substrate in sequence; Step 2, preparing an intermediate active layer: placing the titanium substrate pretreated in step 1 in a mixed acid solution, and sealing and preserving it for a certain period of time, so that an active layer grows in situ on the surface of the titanium substrate; the mixed acid solution is any one or a combination of hydrofluoric acid, sulfuric acid, and oxalic acid solution; Step 3, preparing a coating solution: dissolving a platinum compound in a solvent, and then adding polyurethane acrylate, hydroxyethyl methacrylate, and isopropyl benzoate to mix; the platinum compound is any one or a combination of chloroplatinic acid, potassium chloroplatinate, and P salt; the solvent is any one or a combination of water, ethanol, methanol, isopropanol, and n-butanol; Step 4, preparing a protective layer: coating the coating liquid prepared in step 3 on the surface of the titanium substrate with the intermediate active layer prepared in step 2, drying and irradiating with light, and then sintering.

2. The preparation method according to claim 1, characterized in that: In step 1, the polishing conditions of the titanium substrate are as follows: the fluid temperature is 40° C. and the pressure is 1 MPa; and the surface roughness Ra is ≤ 1 μm after polishing.

3. The preparation method according to claim 1, characterized in that: In step 1, the ultrasonic degreasing process is: using a metal cleaning agent to perform cleaning at a temperature of 50° C. and a cleaning time of 30 minutes.

4. The preparation method according to claim 1, characterized in that: In step 1, the specific process of alkaline washing is: the degreased titanium substrate is placed in a 5% sodium hydroxide solution and soaked for 3 hours, and then washed three times with pure water. After the impurity elements on the surface of the titanium substrate are completely removed, it is taken out and dried for later use.

5. The preparation method according to claim 1, characterized in that: In the mixed acid solution, the components are calculated by mass percentage, with hydrofluoric acid accounting for 0-10%, sulfuric acid accounting for 0-20%, and oxalic acid accounting for 0-15%.

6. The preparation method according to claim 1, characterized in that: In step 2, the main components of the intermediate active layer are compounds of titanium and single or multiple non-metallic elements such as oxygen, fluorine, sulfur and carbon.

7. The preparation method according to claim 1, characterized in that: In step 3, the mass fraction of the platinum compound added is 0.001% to 5% based on the platinum content, and the mass fractions of the polyurethane acrylate, hydroxyethyl methacrylate, and benzoin isopropyl ether added are 0.1% to 10%, 0.1% to 20%, and 0.1% to 10%, respectively.

8. The preparation method according to claim 1, characterized in that: In step 4, the specific process flow for preparing the protective layer is: 4.1) Drying the titanium substrate coated with the coating liquid at a temperature of 50°C to 250°C, then curing it under light for 1min to 10h, and then cleaning the uncured coating liquid in the hole; 4.2) Sintering the titanium substrate treated in step 4.1) at 300°C to 650°C for 10 min to 10 h, taking it out and cooling it to room temperature for the next coating, repeating the above step 4.1) until the platinum content in the prepared protective layer reaches the requirement; 4.3) When the coating liquid in step 4.2) is applied to the last coat, sintering is carried out at 300°C to 650°C for 1h to 24h, and then the desired protective layer is obtained by cooling to room temperature after taking out.

9. The preparation method according to claim 8, characterized in that: In the step 4.1), a 1% tetramethylammonium hydroxide aqueous solution is used for cleaning, and then the cleaning is performed with pure water and air-dried for later use.

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