Hydrogen removal catalytic layer and preparation method thereof, and PEM water electrolysis membrane electrode with hydrogen removal catalytic layer

Abstract

The present invention discloses a hydrogen removal catalytic layer, a preparation method thereof, and a PEM water electrolysis membrane electrode having the hydrogen removal catalytic layer. The hydrogen removal catalytic layer is obtained by mixing a chloroplatinic acid solution, a surfactant, and a Nafion resin solution, adding a reducing agent to form a catalyst slurry, adjusting the slurry to a suitable viscosity, and finally spraying or coating and drying to form a film. In the membrane electrode preparation of the present invention, the hydrogen removal catalytic layer is added to allow leaked hydrogen to react with oxygen, thereby reducing the hydrogen concentration in the anode oxygen. The preparation method of the hydrogen removal catalytic layer utilizes in-situ reduction of Pt ions within the Nafion membrane, effectively improving the uniformity of Pt distribution and enhancing hydrogen removal efficiency.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cells, and in particular relates to a hydrogen removal catalytic layer and a preparation method thereof, as well as a PEM water electrolysis membrane electrode having the hydrogen removal catalytic layer. Background Art

[0002] During the operation of the proton exchange membrane water electrolysis membrane electrode, the electrochemical reaction at the anode is that water is electrolyzed to generate oxygen and hydrogen ions. The hydrogen ions pass through the proton exchange membrane to the cathode, and the cathode hydrogen ions gain electrons to generate hydrogen. However, the proton exchange membrane is not completely dense, which will cause hydrogen and oxygen to cross-contaminate each other. As we all know, the explosion limit of hydrogen in air is 4% Vol, which is extremely dangerous.

[0003] The traditional hydrogen removal method uses an external hydrogen removal device, that is, adding a hydrogen removal device at the oxygen outlet of the electrolyzer of the water electrolysis device. However, when the oxygen humidity is high, the hydrogen content is high, and the flow rate is too fast, the hydrogen removal device cannot completely remove the hydrogen, and the external hydrogen removal device is not conducive to system simplification. Summary of the Invention

[0004] The present invention is proposed to overcome the shortcomings of the prior art, and its purpose is to provide a hydrogen removal catalytic layer and a preparation method thereof, as well as a PEM water electrolysis membrane electrode having the hydrogen removal catalytic layer.

[0005] The present invention is achieved through the following technical solutions:

[0006] A hydrogen removal catalytic layer is provided. The slurry constituting the hydrogen removal catalytic layer comprises chloroplatinic acid, a surfactant, a reducing agent, a Nafion resin and a viscosity regulator.

[0007] In the above technical solution, the surfactant is Nafion resin or PDDA, preferably Nafion resin. Since Nafion resin is charged, it can act as a surfactant to prevent Pt from agglomerating. The Pt distribution in the coated hydrogen removal layer is more uniform and the hydrogen removal effect is better. Therefore, the surfactant is preferably Nafion resin.

[0008] In the above technical solution, when the surfactant is Nafion resin, the mass ratio of the surfactant to the Pt ions of chloroplatinic acid is (0.5-10):1; when the surfactant is PDDA (MW=~5000), the mass ratio of the surfactant to the Pt ions of chloroplatinic acid is (5-50):1.

[0009] In the above technical solution, the reducing agent is any one or more combinations of ethanol, ethanol and alkali, sodium borohydride, water and hydrazine or ethylene glycol, preferably ethanol, that is, chloroplatinic acid is reduced by hydroxyl; the alkali is sodium hydroxide or potassium hydroxide.

[0010] In the above technical solution, when ethanol is used alone as a reducing agent, the mass ratio of ethanol to chloroplatinic acid is 1101-1500, preferably 1101-1200. There are enough hydroxyl groups and the reaction is fast enough, so there is no need to add alkali to adjust the pH of the solution. When ethanol is used as a reducing agent, the mass ratio of ethanol to chloroplatinic acid is preferably 1155.

[0011] In the above technical solution, when a combination of ethanol and alkali is used as a reducing agent, the mass ratio of ethanol to chloroplatinic acid is 400-1100, preferably 400-500. Alkali is added to adjust the pH of the solution to 8-9 to accelerate the reduction of chloroplatinic acid by alcohol, which can reduce the amount of alcohol added. However, the disadvantage is that the alcohol itself will be introduced as an impurity.

[0012] In the above technical solution, when ethanol alone or a combination of ethanol and alkali is used as the reducing agent, the chloroplatinic acid aqueous solution, the surfactant and the reducing agent need to be mixed and then heated and refluxed.

[0013] In the above technical solution, when the reducing agent is sodium borohydride, the mass ratio of sodium borohydride to chloroplatinic acid is (0.5-25):1.

[0014] In the above technical solution, when the reducing agent is hydrazine hydrate, the mass ratio of hydrazine hydrate to chloroplatinic acid is (80-200):1.

[0015] In the above technical solution, when the reducing agent is ethylene glycol, the mass ratio of ethylene glycol to chloroplatinic acid is (150-400):1.

[0016] In the above technical solution, the viscosity modifier is any one of isopropyl alcohol, methanol, ethanol, ethylene glycol, isopropyl alcohol, n-propyl alcohol, propylene glycol, glycerol, isobutyl alcohol, n-butyl alcohol, sec-butyl alcohol, n-heptyl alcohol, or ethyl acetate, preferably ethanol. Ethanol can serve as both a reducing agent and a viscosity modifier, minimizing the introduction of impurities into the slurry. The viscosity range is adjusted based on the coating equipment. Once the viscosity range is determined, the amount of viscosity modifier added can be determined based on the choice of viscosity modifier. Therefore, there is no fixed ratio between the viscosity modifier and chloroplatinic acid or dry resin.

[0017] In the above technical solution, the mass ratio between the Nafion resin and the Pt ions of chloroplatinic acid is (30-200):1. When the ratio is too high, the hydrogen removal layer will be too thick, which will have a negative impact on the performance of the electrolytic cell; when the ratio is too low, the Pt ions will be easily oxidized at high potential. Taking both into account, the optimal range is (30-200):1.

[0018] A method for preparing a hydrogen removal catalytic layer comprises the following steps:

[0019] (i) mixing an aqueous solution of chloroplatinic acid, a surfactant, and a reducing agent, and heating under reflux to obtain an initial slurry;

[0020] (ii) drying part of the solvent in the initial slurry to increase the solid content by 50 times, leaving only a portion of the solvent as a viscosity modifier;

[0021] (iii) adding a Nafion resin solution as a main structure and a viscosity modifier to the initial slurry obtained by drying a portion of the solvent and mixing them to obtain a support slurry;

[0022] (iv) Assembling the support slurry on the proton exchange membrane to obtain the hydrogen removal catalytic layer.

[0023] In the above technical solution, the support slurry is assembled by coating, direct coating or spraying;

[0024] When the coating method is adopted, the support slurry is first coated on the substrate and then transferred to the proton exchange membrane; during the transfer, the dehydrogenation catalytic layer and the proton membrane are transferred first and then the catalytic layer is transferred, or the dehydrogenation catalytic layer and the catalytic layer are transferred first and then the proton exchange membrane and the dehydrogenation catalytic layer are transferred; the substrate is a conventional material with a smooth surface and good thermal stability, chemical stability, and mechanical stability;

[0025] When direct coating is used, the support slurry is first applied to the proton exchange membrane, and then hot-pressed; the hot-pressing temperature is 110°C to 170°C, and the time is 3 minutes;

[0026] When the spraying method is adopted, the support slurry is directly sprayed onto the proton exchange membrane.

[0027] A PEM water electrolysis membrane electrode with a hydrogen removal catalytic layer includes a hydrogen removal catalytic layer, which is arranged between a proton exchange membrane and an anode catalytic layer, or between a proton exchange membrane and a cathode catalytic layer, or is directly coated in the middle of the proton exchange membrane.

[0028] In the above technical solution, no matter what assembly method is used for the supporting slurry, the PEM water electrolysis membrane electrode needs to dry the prepared combination of the hydrogen removal catalyst layer and the proton exchange membrane in an oven at a temperature of 90°C to 180°C, preferably 110°C to 180°C for more than 30 minutes before assembly to improve the peeling force between the hydrogen removal layer and the proton exchange membrane. That is, no matter what transfer order is used, the hydrogen removal catalyst layer and the proton exchange membrane need to be dried after transfer.

[0029] The beneficial effects of the present invention are:

[0030] The present invention provides a hydrogen removal catalytic layer and a preparation method thereof, as well as a PEM water electrolysis membrane electrode having the hydrogen removal catalytic layer. During the preparation of the membrane electrode, the hydrogen removal catalytic layer is added to allow leaked hydrogen to react with oxygen, thereby reducing the hydrogen concentration in the anode oxygen. The preparation method of the hydrogen removal catalytic layer uses in-situ reduction of Pt ions in a Nafion membrane, effectively improving the uniformity of Pt distribution and improving hydrogen removal efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a data comparison chart of hydrogen in oxygen for the electrodes of Example 1 of the present invention and Comparative Example 1 at different electrolyzer operating pressures. DETAILED DESCRIPTION

[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.

[0033] Example 1

[0034] A method for preparing a PEM water electrolysis membrane electrode having a hydrogen removal catalytic layer comprises the following steps:

[0035] (i) 1 g of a 5 wt% aqueous solution of chloroplatinic acid and 57.8 g of ethanol were added to a Nafion resin solution as a surfactant, with the mass ratio of the dry Nafion resin solution to the Pt ions in the chloroplatinic acid being 1:1. The mixture was refluxed at 88°C and then dried at 80°C to concentrate the solution and remove some of the solvent, thereby increasing the solid content by 50 times.

[0036] (ii) adding Nafion resin solution as the main structure and 1 g of isopropyl alcohol and ball milling for 4 h to prepare a support slurry;

[0037] The mass ratio of the total amount of the Nafion resin solution added as the main structure and the dry resin of the Nafion resin solution added as the surfactant to the Pt ions of chloroplatinic acid is 50:1;

[0038] (iii) coating the support slurry on the substrate to form a film, thereby obtaining a hydrogen removal catalytic layer;

[0039] (iii) After the hydrogen removal catalytic layer and the proton membrane are transferred, the prepared hydrogen removal membrane is dried in an oven at 165° C. for 30 min;

[0040] (iv) The cathode and anode catalyst layers were then transferred (transfer temperature 165°C, transfer time 3 min) to obtain a PEM water electrolysis membrane electrode with a hydrogen removal catalyst layer.

[0041] Example 2

[0042] A method for preparing a PEM water electrolysis membrane electrode having a hydrogen removal catalytic layer comprises the following steps:

[0043] (i) 1 ml of a 5 wt % aqueous solution of chloroplatinic acid and 30 ml of ethanol were mixed, and a Nafion resin solution as a surfactant was added thereto. The mixture was mixed again, with the mass ratio of the Nafion resin solution as a surfactant to the Pt ions of the chloroplatinic acid being 0.5:1. The mixture was refluxed at 82°C for 1 to 2 hours, and the pH of the solution was adjusted to 8 to 9 with a NaOH solution during reflux.

[0044] (ii) adding Nafion resin solution as the main structure and 0.8 g of isopropyl alcohol and ball milling for 4 h to prepare a support slurry;

[0045] Ensure that the mass ratio of the total amount of Nafion resin solution added as the main structure and the dry resin of Nafion resin solution as the surfactant to the Pt ion of chloroplatinic acid is 50:1

[0046] (iii) coating the support slurry on a substrate to form a film, thereby obtaining a hydrogen removal catalytic layer, and subsequently transferring or directly coating the slurry on a proton exchange membrane to obtain a hydrogen removal membrane;

[0047] (iv) The hydrogen removal membrane prepared in step (iii) was cleaned with 8 wt % sulfuric acid solution at 80° C. for 30 min, then rinsed with 18 MΩ ultrapure water at 80° C. for 30 min, and then dried at 165° C. for 30 min.

[0048] (iv) The anode and cathode catalyst layers were transferred by transfer printing (transfer temperature 165°C, transfer time 3 min) to complete the preparation of the PEM water electrolysis membrane electrode with a hydrogen removal catalyst layer.

[0049] Comparative Example 1

[0050] (i) 0.1 g of 50 nm Pt particles were added to a 20% by mass Nafion resin solution, such that the mass ratio of dry resin to Pt particles was 50:1. 2 g of isopropyl alcohol, 1 g of ethanol, and 3 g of ultrapure water were then added and ball-milled for 4 h to obtain a dehydrogenation slurry.

[0051] (ii) spraying the hydrogen scavenging slurry onto a substrate to obtain a hydrogen scavenging layer, and transferring the hydrogen scavenging layer onto a proton exchange membrane;

[0052] (iii) After the hydrogen removal layer and the proton membrane are transferred, the prepared hydrogen removal membrane is baked in an oven at 165° C. for 30 min.

[0053] (iv) The cathode and anode catalytic layers were then transferred (165°C, 3 min) to obtain a PEM water electrolysis membrane electrode with a hydrogen removal catalytic layer.

[0054] During the operation of the PEM electrolyzer, the anode consumes water to produce oxygen, and the cathode produces hydrogen. The hydrogen and oxygen at the cathode and cathode interact with each other, which will increase the hydrogen concentration in the anode oxygen. If the volume fraction of hydrogen gas in the air exceeds 4%, an explosion will occur.

[0055] The PEM water electrolysis membrane electrode with a hydrogen removal catalytic layer produces an electrochemical reaction between hydrogen and oxygen, effectively reducing the concentration of hydrogen in oxygen in the anode gas. Therefore, the concentration of hydrogen in oxygen under different electrolyzer operating loads is an effective means to evaluate the performance of the hydrogen removal membrane electrode. The prepared membrane electrode is assembled into the electrolyzer, and the anode tail gas is completely dried during operation and then connected to a gas chromatograph for analysis. Figure 1 As shown, under the same conditions (80° C., 30 bar), the hydrogen removal effect of the self-assembled membrane electrode in Example 1 is better than that in Comparative Example 1.

[0056] Principle of the present invention:

[0057] Chloroplatinic acid solution, surfactant and Nafion resin solution are mixed and stirred. The surfactant is preferably Nafion resin solution, and the reducing agent is preferably ethanol. The Nafion resin solution itself is charged and can act as a surfactant to prevent Pt from agglomerating. The Pt distribution of the coated hydrogen removal layer is more uniform, and the hydrogen removal effect is good. At the same time, the Nafion resin solution is added as the main structure of the hydrogen removal layer. Because the proton exchange membrane is also made of Nafion, the hydrogen removal layer and the proton exchange membrane can be more firmly combined during hot pressing. Ethanol can be used as a reducing agent to reduce chloroplatinic acid into Pt particles, and also as a solvent and viscosity regulator for the coating slurry, reducing the raw material composition of the slurry and avoiding the introduction of excessive impurities.

[0058] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a hydrogen removal catalytic layer, characterized in that: The following steps are involved: (i) mixing an aqueous solution of chloroplatinic acid, a surfactant, and a reducing agent, and heating under reflux to obtain an initial slurry; (ii) drying part of the solvent in the initial slurry to increase the solid content by 50 times; (iii) adding a Nafion resin solution as a main structure and a viscosity modifier to the initial slurry obtained by drying a portion of the solvent and mixing them to obtain a support slurry; (iv) assembling the support slurry on a proton exchange membrane to obtain a hydrogen removal catalytic layer; The reducing agent is ethanol; The viscosity modifier is ethanol; The surfactant is Nafion resin or PDDA; When the surfactant is Nafion resin, the mass ratio of the surfactant to the Pt ions of chloroplatinic acid is 0.5 to 10:1; when the surfactant is PDDA, the mass ratio of the surfactant to the Pt ions of chloroplatinic acid is 5 to 50:

1.

2. The method for preparing a hydrogen removal catalytic layer according to claim 1, wherein: The mass ratio of the reducing agent ethanol to chloroplatinic acid is 1101-1500.

3. The method for preparing a hydrogen removal catalytic layer according to claim 1, wherein: The support slurry is assembled by coating, direct coating or spraying; When the coating method is adopted, the support slurry is first coated on the substrate and then transferred to the proton exchange membrane; during the transfer, the dehydrogenation catalytic layer and the proton membrane are transferred first and then the catalytic layer is transferred, or the dehydrogenation catalytic layer and the catalytic layer are transferred first and then the proton exchange membrane and the dehydrogenation catalytic layer are transferred; When direct coating is used, the support slurry is first applied to the proton exchange membrane and then hot-pressed; When the spraying method is adopted, the support slurry is directly sprayed onto the proton exchange membrane.

4. A PEM water electrolysis membrane electrode having a hydrogen removal catalytic layer, characterized in that: The invention comprises a hydrogen removal catalytic layer prepared by the method according to any one of claims 1 to 3, wherein the hydrogen removal catalytic layer is arranged between the proton exchange membrane and the anode catalytic layer, or between the proton exchange membrane and the cathode catalytic layer.

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