Alkaline water electrolysis membrane electrode and preparation method thereof and electrolytic cell

Abstract

The present invention provides an alkaline water electrolysis membrane electrode and a preparation method and an electrolytic cell thereof, wherein the preparation method comprises the following steps: performing surface modification treatment on a nickel-based alloy to form an oxide layer or a hydroxide layer on the surface of the nickel-based alloy to obtain a modified nickel-based alloy; mixing the modified nickel-based alloy with an auxiliary agent and a solvent for pulping to obtain a membrane electrode slurry; coating the membrane electrode slurry on a substrate and hot pressing to form a film to obtain a hot pressed membrane electrode; performing impurity element leaching treatment on the hot pressed membrane electrode to obtain a membrane electrode containing Raney nickel. The present invention solves the problem of easy sedimentation and stratification of the slurry when the Raney nickel catalyst is directly used for pulping by performing surface modification on the Raney nickel precursor and using it for pulping, which is convenient for large-scale coating, and reduces the amount of dispersant and thickener used during pulping, improves the problem of reduced electrochemical performance of the membrane electrode caused by adding auxiliary agents, and improves the quality of the membrane electrode.

Description

Technical Field

[0001] The present invention belongs to the technical field of alkaline water electrolysis hydrogen production, and in particular, relates to an alkaline water electrolysis membrane electrode and a preparation method thereof and an electrolytic cell. Background Art

[0002] At present, commercial water electrolysis is mainly based on alkaline water electrolysis. The HER reaction occurs on the cathode side during the alkaline water electrolysis process. In order to increase the HER electrochemical reaction rate, the mainstream approach is to use precious metals such as Pt, Pd, and Rh as cathode catalysts. However, in large electrolyzers, in order to save costs, cathode catalysts are more commonly nickel or nickel alloy materials, such as Raney nickel, nickel-cobalt alloy, nickel-molybdenum alloy, nickel-cobalt-molybdenum alloy, etc. However, due to the poor hydrophilicity of metal nickel catalysts and poor slurrying performance in polar solvents, slurry stratification is prone to occur during the actual preparation of cathode catalysts. In order to obtain a uniform slurry, more dispersants need to be added during slurrying, and adding excessive dispersants to the slurry will affect the electrolysis efficiency of the membrane electrode. Therefore, it is very important to improve the hydrophilicity of the catalyst.

[0003] The existing methods for improving catalysts are mostly to introduce substances that improve the activity of the catalyst into the catalyst material. For example, He W. et al. (Small, 19 (2023) 2205719) proposed a self-supporting microporous Ni(OH)x / Ni3S2 heterostructure electrocatalyst (Ni(OH)x / Ni3S2 / NF), which first vertically grew Ni3S2 / NF nanosheet arrays on nickel foam by a two-step hydrothermal method, and then electrochemically treated Ni3S2 / NF in 1M KOH to obtain Ni(OH)x / Ni3S2 / NF nanosheet arrays with super hydrophilic properties (contact angle of 0°) and excellent catalytic activity and stability in hydrogen evolution at high current density in alkaline media.

[0004] Chinese patent application 201910908633.5 provides a method for preparing a porous carbide hydrogen evolution electrode with a honeycomb microstructure, in which a porous carbide layer with a honeycomb microstructure is prepared on the surface of a base metal by cathode electrolytic carburization in a molten salt electrolyte containing molten carbonate. No conductive agent and binder need to be added when preparing the electrode. At the same time, the prepared electrode has good hydrophilicity, and the contact angle with water ranges from 10° to 50°, and exhibits good hydrogen evolution effect and stability in both acidic and alkaline environments.

[0005] However, the prior art does not significantly improve the performance of alkaline water electrolysis catalysts, and the electrolysis efficiency of existing alkaline water electrolysis membrane electrodes still needs to be further improved. Summary of the invention

[0006] The purpose of the present invention is to further improve the electrolysis efficiency of the existing alkaline water electrolysis membrane electrode.

[0007] In order to achieve the above object, the first aspect of the present invention provides a method for preparing an alkaline water electrolysis membrane electrode, the method comprising the following steps:

[0008] Performing surface modification treatment on the nickel-based alloy to form an oxide layer or a hydroxide layer on the surface of the nickel-based alloy to obtain a modified nickel-based alloy;

[0009] The modified nickel-based alloy is mixed with an auxiliary agent and a solvent for slurrying to obtain a membrane electrode slurry, wherein the auxiliary agent includes a dispersant and a thickener, and the mass ratio of the modified nickel-based alloy to the dispersant and the thickener is 1: (0.001-0.0.05): (0.001-0.01);

[0010] The membrane electrode slurry is coated on a substrate and hot-pressed to form a film to obtain a hot-pressed membrane electrode;

[0011] The hot-pressed membrane electrode is subjected to a treatment for leaching impurities to obtain a membrane electrode containing Raney nickel.

[0012] Optionally, the surface modification treatment method includes passivation in an oxidizing atmosphere, flame oxidation, alkali washing or plasma treatment.

[0013] Optionally, the modified nickel-based alloy has one or more of the following characteristics:

[0014] (1) The contact angle of the modified nickel-based alloy is less than 90°;

[0015] (2) The double electric layer Zeta potential value of the modified nickel-based alloy is 40-60 mV.

[0016] Optionally, the nickel content in the nickel-based alloy is 30-70wt%;

[0017] The particle size of the nickel-based alloy is 0.005-10 μm;

[0018] The content of nickel in the Raney nickel is 90-99wt%.

[0019] Optionally, the substrate is selected from at least one of a polyphenylene sulfide membrane, a polyetheretherketone fiber membrane and a polysulfone fiber membrane; the hot pressing temperature is 50-500° C., and the hot pressing time is 1-60 min.

[0020] Optionally, the auxiliary agent further includes a binder, and the mass ratio of the modified nickel-based alloy to the binder is 1:(0.2-10);

[0021] The mass ratio of the modified nickel-based alloy to the solvent is 1:(0.2-5).

[0022] Preferably, the mass ratio of the modified nickel-based alloy to the dispersant is 1:(0.001-0.03); the mass ratio of the modified nickel-based alloy to the thickener is 1:(0.001-0.04).

[0023] Optionally, the dispersant is a phosphate dispersant or an acrylic dispersant, preferably at least one of sodium hexametaphosphate, potassium tripolyphosphate, acrylate, acrylic acid copolymer homopolymer and acrylic acid amine salt;

[0024] The binder is at least one of perfluorosulfonic acid resin, polytetrafluoroethylene resin, polyethersulfone and fluororesin;

[0025] The thickener is at least one of a cellulose ether thickener, a polyurethane thickener, and a modified polyurea thickener;

[0026] The solvent is at least one of water, ethanol, isopropanol, propylene glycol, butanol and butanediol; preferably at least one of water, ethanol and isopropanol.

[0027] Optionally, the nickel-based alloy is a nickel-aluminum alloy and / or a nickel-zinc alloy;

[0028] The impurity element leaching process comprises the following steps:

[0029] placing the hot-pressed membrane electrode in a composite alkali solution for leaching treatment to remove the impurity elements in the nickel-based alloy, thereby obtaining a membrane electrode after impurity element leaching;

[0030] The membrane electrode after the impurity elements are leached is placed in an acid solution for pickling treatment, and then the membrane electrode after pickling is washed with deionized water until it is neutral;

[0031] The leaching treatment conditions include: temperature of 0-100°C, time of 5-24h, stirring speed of 500-10000rpm;

[0032] The composite alkali solution contains a complexing agent and KOH or NaOH; the complexing agent is selected from one or more of sodium tartrate, sodium citrate, EDTA, sodium oxalate, Na2S and triethanolamine;

[0033] Based on the weight of the composite alkali solution, the content of KOH or NaOH in the composite alkali solution is 10-30wt%; the molar ratio of the complexing agent to the aluminum element or the zinc element in the nickel-based alloy is 1.1-3.1;

[0034] The conditions for the pickling treatment include: the concentration of the acid solution is 1-2 mol / L, the treatment time is 1-30 min; the acid solution is selected from one or more of dilute hydrochloric acid, sulfuric acid and nitric acid.

[0035] The second aspect of the present invention provides an alkaline water electrolysis membrane electrode prepared according to the first aspect of the present invention.

[0036] The third aspect of the present invention provides an electrolytic cell, wherein the cathode chamber of the electrolytic cell for accommodating the cathode is provided with the alkaline water electrolysis membrane electrode provided by the second aspect of the present invention.

[0037] Through the above technical scheme, the present invention solves the problem that the slurry is easy to settle and stratify when the Raney nickel catalyst is directly used for slurrying, is convenient for large-scale coating, and reduces the amount of dispersant and thickener, improves the problem of reduced electrochemical performance of the membrane electrode caused by the addition of additives, and is beneficial to improving the quality of the membrane electrode.

[0038] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0040] At present, the cathode of alkaline water electrolysis mostly uses Raney nickel as a catalyst. When preparing the cathode electrode, Raney nickel needs to be dispersed in a solvent mainly composed of water to form a slurry. However, Raney nickel has poor hydrophilicity, is magnetic and easy to agglomerate, has poor slurry performance in polar solvent slurry, and the slurry is easy to settle and stratify. In order to obtain a uniform slurry, more dispersants and thickeners need to be added during slurry preparation to maintain the uniformity and stability of the slurry. However, adding excessive dispersants and binders to the slurry will affect the electrolysis efficiency of the membrane electrode. Based on this, the present invention proposes an improved alkaline water electrolysis membrane electrode.

[0041] In order to achieve the above object, the first aspect of the present invention provides a method for preparing an alkaline water electrolysis membrane electrode, the method comprising the following steps:

[0042] Performing surface modification treatment on the nickel-based alloy to form an oxide layer or a hydroxide layer on the surface of the nickel-based alloy to obtain a modified nickel-based alloy;

[0043] The modified nickel-based alloy is mixed with an auxiliary agent and a solvent for slurrying to obtain a membrane electrode slurry, wherein the auxiliary agent includes a dispersant and a thickener, and the mass ratio of the modified nickel-based alloy to the dispersant and the thickener is 1: (0.001-0.05): (0.001-0.01);

[0044] The membrane electrode slurry is coated on a substrate and hot-pressed to form a film to obtain a hot-pressed membrane electrode;

[0045] The hot-pressed membrane electrode is subjected to a treatment for leaching impurities to obtain a membrane electrode containing Raney nickel.

[0046] The present invention performs surface modification on a Raney nickel precursor and uses it for pulping, thereby solving the problem that the slurry is prone to sedimentation and stratification when the Raney nickel catalyst is directly used for pulping. This not only facilitates large-scale coating, but also reduces the amount of dispersant and thickener used in pulping, improves the problem of reduced electrochemical performance of the membrane electrode caused by adding an auxiliary agent, and improves the quality of the membrane electrode.

[0047] Wherein, the surface modification treatment method includes passivation in an oxidizing atmosphere, flame oxidation, alkali washing or plasma treatment.

[0048] In the present invention, passivation in an oxidizing atmosphere refers to passivating the nickel-based alloy in air or oxygen at a passivation temperature of 25-50° C., so that an oxide layer is formed on the surface of the nickel-based alloy. In terms of cost saving, air passivation is preferred for passivation in an oxidizing atmosphere.

[0049] In a specific embodiment of the present invention, the method for air passivation of nickel-based alloy includes: taking nickel-aluminum alloy powder into a crucible, placing it in a ventilated place for 1 week, and stirring the powder from time to time until the nickel-aluminum alloy becomes a dry powder, and the passivation is completed.

[0050] In the present invention, alkali washing refers to immersing the nickel-based alloy in a low-concentration alkali solution to form a hydroxide layer on the surface of the nickel-based alloy.

[0051] In a specific embodiment of the present invention, the method for alkali washing of nickel-based alloy comprises: taking nickel-aluminum alloy powder and placing it in a 0.5-3M dilute alkali solution, soaking it at an alkali washing temperature of 15-40°C for 10-60 minutes, and using magnetic stirring or stirring paddle stirring while soaking, with a rotation speed of 800-1200rpm, preferably 1000rpm.

[0052] In the present invention, the plasma treatment method includes Ar plasma, O2 plasma, air plasma and NH3 plasma.

[0053] In a specific embodiment of the present invention, the method for plasma treatment of nickel-based alloy comprises: pressing nickel-aluminum alloy powder into sheets at a pressure of 20-50MPa, and then placing it in a low-temperature plasma surface treatment machine for treatment, wherein the plasma excitation frequency during treatment is 13.56MHz, the gas pressure is 20-200Pa, and the treatment temperature is 100-200°C. During treatment, the pressed sheet is swept 3-10 times to obtain a plasma-treated nickel-aluminum alloy.

[0054] Wherein, the modified nickel-based alloy has one or more of the following characteristics:

[0055] (1) The contact angle of the modified nickel-based alloy is less than 90°;

[0056] (2) The double electric layer Zeta potential value of the modified nickel-based alloy is 40-60 mV.

[0057] Zeta potential refers to the potential of the shear surface and is an important indicator for characterizing the stability of a dispersed system. According to Stern's double layer theory, the double layer can be divided into two parts, namely the Stern layer and the diffusion layer. When the dispersed particles are under the action of an external electric field, the sliding surface when the stable layer and the diffusion layer move relative to each other is the shear surface. The potential at this point in the fluid far away from the interface is called Zeta potential or electrokinetic potential (ζ-potential).

[0058] By the above-mentioned surface modification method, a metal oxide layer or hydroxide layer is formed on the surface of the nickel-based alloy, and the hydrophilicity of the surface of the nickel-based alloy becomes stronger after modification. After the surface of the nickel-based alloy is modified, the double electric layer is characterized by Zeta potential, and the hydrophilicity is characterized by contact angle, wherein the contact angle of the modified nickel-based alloy is less than 90°, and the double electric layer Zeta potential value is 40-60mV. The Zeta potential value of the nickel-based alloy without surface modification is less than 10mV, and the contact angle is greater than 120°. After the surface modification treatment, the double electric layer Zeta potential value of the nickel-based alloy reaches 40-60mV, indicating that the solution stability is good; the contact angle of the nickel-based alloy after the surface modification treatment is less than 90°, indicating that the hydrophilicity of the nickel-based alloy is significantly enhanced relative to before the modification.

[0059] The nickel content of the nickel-based alloy is 30-70 wt % and the particle size of the nickel-based alloy is 0.005-10 μm. The use of the nickel-based alloy with the above particle size is conducive to preparing a uniform slurry without sedimentation and making the catalyst have better catalytic activity.

[0060] Wherein, the auxiliary agent also includes a binder, and the mass ratio of the modified nickel-based alloy to the binder is 1:(0.2-10);

[0061] The mass ratio of the modified nickel-based alloy to the solvent is 1:(0.2-5).

[0062] Preferably, the mass ratio of the modified nickel-based alloy to the dispersant is 1:(0.001-0.03); the mass ratio of the modified nickel-based alloy to the thickener is 1:(0.001-0.04).

[0063] The present invention improves the hydrophilicity of the nickel-based alloy by modifying the nickel-based alloy. Compared with directly using a Raney nickel catalyst for pulping, the amount of dispersant and thickener used when pulping with the modified nickel-based alloy is significantly reduced.

[0064] Wherein, the dispersant is a phosphate dispersant or an acrylic dispersant, preferably at least one of sodium hexametaphosphate, potassium tripolyphosphate, acrylate, acrylic acid copolymer homopolymer and acrylic acid amine salt;

[0065] The binder is at least one of perfluorosulfonic acid resin, polytetrafluoroethylene resin, polyethersulfone and fluororesin;

[0066] The thickener is at least one of a cellulose ether thickener, a polyurethane thickener, and a modified polyurea thickener;

[0067] The solvent is at least one of water, ethanol, isopropanol, propylene glycol, butanol and butanediol; preferably at least one of water, ethanol and isopropanol.

[0068] In the present invention, the solvent for pulping can be water or any organic solvent miscible with water. In a specific embodiment of the present invention, the solvent is preferably water, or a water-ethanol mixed solution, or a water-isopropanol mixed solution, or a water-ethanol-isopropanol mixed solution.

[0069] The substrate of the present invention is resistant to acid corrosion, strong alkali and heat. The substrate is selected from at least one of polyphenylene sulfide (PPS) diaphragm, polyetheretherketone fiber diaphragm and polysulfone fiber diaphragm.

[0070] Wherein, the hot pressing temperature is 50-500°C, and the hot pressing time is 1-60min.

[0071] Wherein, the nickel-based alloy is a nickel-aluminum alloy and / or a nickel-zinc alloy, preferably a nickel-aluminum alloy. By using the nickel-aluminum alloy or the nickel-zinc alloy as the precursor of Raney nickel, and utilizing the property that aluminum or zinc is soluble in concentrated alkali solution, the nickel-aluminum alloy or the nickel-zinc alloy can be treated with concentrated alkali solution to prepare porous Raney nickel.

[0072] Wherein, the impurity element leaching treatment comprises the following steps:

[0073] placing the hot-pressed membrane electrode in a composite alkali solution for leaching treatment to remove the impurity elements in the nickel-based alloy, thereby obtaining a membrane electrode after impurity element leaching;

[0074] The membrane electrode after the impurity elements are leached out is placed in an acid solution for pickling treatment, and then the pickled membrane electrode is washed with deionized water until it is neutral.

[0075] The leaching treatment conditions include: temperature of 0-100°C, time of 5-24h, stirring speed of 500-10000rpm;

[0076] The composite alkali solution contains a complexing agent and KOH or NaOH; the complexing agent is selected from one or more of sodium tartrate, sodium citrate, EDTA, sodium oxalate, Na2S and triethanolamine;

[0077] Based on the weight of the composite alkali solution, the content of KOH or NaOH in the composite alkali solution is 10-30wt%; the molar ratio of the complexing agent to the aluminum element or the zinc element in the nickel-based alloy is 1.1-3.1.

[0078] The conditions for the pickling treatment include: the concentration of the acid solution is 1-2 mol / L, the treatment time is 1-30 min; the acid solution is selected from one or more of dilute hydrochloric acid, sulfuric acid and nitric acid.

[0079] In the present invention, the membrane electrode after hot pressing is immersed in a composite alkali solution to remove the impurity elements in the nickel-based alloy, such as aluminum or zinc and their compounds, to form a membrane electrode with Raney nickel as a catalyst, and then the membrane electrode after the impurity element leaching treatment is pickled to remove the oxide layer and residual aluminum or zinc compounds in the nickel-based alloy. In a preferred embodiment of the present invention, the nickel-based alloy is a nickel-aluminum alloy, and the composite alkali solution is preferably an alkali solution containing KOH and a complexing agent to prevent the formation of aluminum hydroxide precipitation to block the gaps of Raney nickel.

[0080] The content of Ni in the Raney nickel is 90-99 wt %. The distribution of aluminum or zinc in the Raney nickel membrane electrode finally obtained is observed, and the content of nickel is 90-99 wt %, which is consistent with the proportion of nickel and other elements in the Raney nickel powder.

[0081] The second aspect of the present invention provides an alkaline water electrolysis membrane electrode prepared according to the first aspect of the present invention.

[0082] The third aspect of the present invention provides an electrolytic cell, wherein the cathode chamber of the electrolytic cell for accommodating the cathode is provided with the alkaline water electrolysis membrane electrode provided by the second aspect of the present invention.

[0083] The present invention is further described in detail by way of examples below, but the present invention is not limited to the following examples. The raw materials used in the examples can be obtained through commercial channels unless otherwise specified.

[0084] Example 1

[0085] Example 1 Preparation of alkaline water electrolysis membrane electrode cathode, including the following steps:

[0086] (1) taking nickel-aluminum alloy particles with a particle size of 0.01-10 μm and placing them in air for oxidation to form a thin oxide layer on the surface of the particles, thereby obtaining a modified nickel-aluminum alloy;

[0087] (2) Using water as solvent, adding dispersant, binder, thickener and modified nickel-aluminum alloy, stirring and mixing, and then dispersing by ultrasonic; wherein the dispersant is acrylic acid amine salt, the binder is perfluorosulfonic acid resin, and the thickener is polyurethane thickener; the mass ratio of the modified nickel-aluminum alloy to the solvent, dispersant, binder and thickener is 1:0.5:0.004:1:0.006;

[0088] (3) coating the slurry prepared in step (2) on the substrate membrane and hot pressing to form a film; wherein the hot pressing temperature is 150° C. and the hot pressing time is 1 h, to obtain a hot pressed membrane electrode;

[0089] (4) soaking the hot-pressed membrane electrode in a composite alkali solution and stirring for 24 hours to perform leaching treatment of impurities, the leaching temperature is 25°C, and the stirring speed is 500 rpm; soaking the membrane electrode soaked in alkali solution in 1 mol / L dilute hydrochloric acid for 0.5 hours, and then washing the acid-washed membrane electrode with deionized water until neutral, thereby obtaining an alkaline electrolytic water membrane electrode cathode E1;

[0090] The composite alkali solution includes complexing agents triethylamine and KOH. Based on the mass of the composite alkali solution, the content of KOH is 30wt%; the molar ratio of triethylamine to aluminum element in the nickel-aluminum alloy is 2.1.

[0091] The properties of the modified nickel-aluminum alloy prepared in this example are shown in Table 1, and the electrochemical properties of the alkaline water electrolysis membrane electrode cathode E1 are shown in Table 2.

[0092] Example 2

[0093] The method for preparing the cathode of the alkaline water electrolysis membrane electrode in Example 2 is the same as that in Example 1, except that:

[0094] In step (1), the method for surface modification of nickel-aluminum alloy is plasma treatment (O2 plasma), which specifically includes the following steps: pressing the nickel-aluminum alloy powder into a sheet at a pressure of 20-50MPa, and then placing it into a low-temperature plasma surface treatment machine, and performing plasma treatment with oxygen as the equipment gas; the plasma excitation frequency is 13.56MHz, the gas pressure is 20-200Pa, and the treatment temperature is 100-200°C. During the treatment, the pressed sheet is swept 3-10 times to form a thin oxide layer on the surface of the nickel-aluminum alloy to obtain a plasma-treated nickel-aluminum alloy.

[0095] The properties of the modified nickel-aluminum alloy prepared in this example are shown in Table 1, and the electrochemical properties of the alkaline water electrolysis membrane electrode cathode E2 are shown in Table 2.

[0096] Example 3

[0097] The method for preparing the cathode of the alkaline water electrolysis membrane electrode in Example 3 is the same as that in Example 1, except that:

[0098] In step (1), the method for modifying the surface of the nickel-aluminum alloy is to immerse the nickel-aluminum alloy powder in a NaOH solution with a concentration of 1M and a temperature of 15-40°C, and stir it at a stirring speed of 1000 rpm, and take it out after 60 minutes to form a hydroxide layer on the surface of the nickel-aluminum alloy.

[0099] The properties of the modified nickel-aluminum alloy prepared in this example are shown in Table 1, and the electrochemical properties of the alkaline water electrolysis membrane electrode cathode E3 are shown in Table 2.

[0100] Example 4

[0101] The method for preparing the cathode of the alkaline electrolytic water membrane electrode in Example 4 is the same as that in Example 1, except that:

[0102] In step (2), the solvent is a water-ethanol mixed solution with a mass ratio of 1:1, wherein the dispersant is potassium tripolyphosphate, the binder is a fluororesin binder, and the thickener is a modified polyurea thickener; the mass ratio of the modified nickel-aluminum alloy to the solvent, the dispersant, the binder, and the thickener is 1:0.5:0.005:1:0.01;

[0103] In step (4), the complexing agent in the composite alkali solution is sodium tartrate.

[0104] The properties of the modified nickel-aluminum alloy prepared in this example are shown in Table 1, and the electrochemical properties of the alkaline water electrolysis membrane electrode cathode E4 are shown in Table 2.

[0105] Comparative Example 1

[0106] Comparative Example 1 Preparation of alkaline water electrolysis membrane electrode cathode D1, including the following steps:

[0107] (1) Using water as solvent, adding dispersant, binder, thickener and nickel-aluminum alloy with a particle size of 0.01-10 μm, stirring and mixing, and then dispersing by ultrasound; wherein the dispersant is sodium hexametaphosphate, the binder is polyethersulfone, and the thickener is CMC; the mass ratio of nickel-aluminum alloy to solvent, dispersant, binder, and thickener is 1:0.5:0.03:1:0.07;

[0108] (2) coating the slurry prepared in step (1) on the substrate membrane and hot pressing to form a film; wherein the hot pressing temperature is 200° C. and the hot pressing time is 1 h, to obtain a hot pressed membrane electrode;

[0109] (3) soaking the hot-pressed membrane electrode in a composite alkali solution and stirring for 24 hours to perform leaching treatment of impurities, the leaching temperature is 25°C, and the stirring speed is 500 rpm; soaking the membrane electrode soaked in alkali solution in 1 mol / L dilute hydrochloric acid for 0.5 hours, and then washing the acid-washed membrane electrode with deionized water until it is neutral;

[0110] The composite alkali solution includes complexing agents triethylamine and KOH. Based on the mass of the composite alkali solution, the content of KOH is 30wt%, and the molar ratio of triethylamine to aluminum element in the nickel-aluminum alloy is 2.1.

[0111] The properties of the nickel-aluminum alloy of this comparative example are shown in Table 1, and the electrochemical performance of the cathode D1 of the alkaline water electrolysis membrane electrode is shown in Table 2.

[0112] Comparative Example 2

[0113] Comparative Example 2: Using Raney nickel as a catalyst to prepare an alkaline water electrolysis membrane electrode cathode D2, comprising the following steps:

[0114] (1) Using water as solvent, adding a dispersant, a binder, a thickener and Raney nickel with a particle size of 0.01-10 μm, stirring and mixing, and then dispersing by ultrasound; wherein the dispersant is acrylate, the binder is polyethersulfone, and the thickener is carboxymethyl cellulose; the mass ratio of Raney nickel to solvent, dispersant, binder and thickener is 1:0.5:0.05:1:0.05;

[0115] (2) coating the slurry prepared in step (2) on the substrate membrane and hot pressing to form a membrane; wherein the hot pressing temperature is 200° C. and the hot pressing time is 1 h, to obtain a membrane electrode.

[0116] The electrochemical performance of the cathode D2 of the alkaline water electrolysis membrane electrode in this comparative example is shown in Table 2.

[0117] (I) Nickel-aluminum alloy performance test

[0118] Test method:

[0119] Zeta potential absolute value: Use a Zeta potential tester for testing, and the test method is electrophoretic light scattering. Prepare the nickel-aluminum alloy into a 0.05-0.1 mg / L slurry dilution, and the diluent is water, ethanol, or isopropanol. Put the dilution into the sample pool for testing, and test each sample 3 times to take the average value.

[0120] Contact angle: Take a 3cm×3cm membrane electrode, place the nickel-aluminum alloy on the contact angle test bench, drop 1ml of water, measure the contact angle, measure 3 times, and take the average value as the final contact angle.

[0121] The absolute values ​​of the Zeta potential and the contact angles of the nickel-aluminum alloys obtained after surface modification in Examples 1-4 and the nickel-aluminum alloys without surface modification in Comparative Example 1 are shown in Table 1.

[0122] Table 1

[0123] Zeta potential absolute value (mV) Contact angle (°) Example 1 50 82 Example 2 45 79 Example 3 60 83 Example 4 55 85 Comparative Example 1 10 135

[0124] As shown in Table 1, by surface modification of nickel-aluminum alloy, the double electric layer Zeta potential value of the modified nickel-aluminum alloy increased from 10mV to 40-60mV, and the contact angle decreased from 135° to 90°.

[0125] The following shows that the hydrophilicity of the modified nickel-aluminum alloy is enhanced. Moreover, the amount of dispersant and thickener used in slurrying with the surface-modified nickel-aluminum alloy is reduced by more than 50%, and the slurry is uniform and not easy to settle, which is convenient for large-scale production and coating.

[0126] (II) Membrane electrode performance test

[0127] The membrane electrodes prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to stack tests.

[0128] Battery stack test method: 400cm 2 The membrane electrodes of different sizes are fixed on the battery stack fixture of the two electrodes, and the cathode and anode of the fixture are connected to a constant current power supply to form a circuit. After the circuit is connected, the constant current power supply provides 160A current for electrolysis, and the electrolysis voltage and resistance are measured.

[0129] The battery stack test results are shown in Table 2.

[0130] Table 2

[0131] Ohm resistance (mΩ) Decomposition voltage(V) Example 1 0.83 1.77 Example 2 0.75 1.75 Example 3 1.02 1.78 Example 4 0.95 1.76 Comparative Example 1 8.50 1.82 Comparative Example 2 7.80 1.83

[0132] According to the data in Table 2, the alkaline water electrolysis membrane electrode prepared by the present invention is used for the battery test. Compared with the membrane electrode using Raney nickel as a catalyst in Comparative Example 2, the ohmic resistance of the membrane electrode prepared by the present invention can be reduced by 50-80%, and the decomposition voltage is reduced by 5-20mV@4000A / m 2 The energy-saving effect is obvious, energy consumption is reduced, the problem of reduced electrochemical performance of membrane electrodes caused by adding additives is improved, and the quality of membrane electrodes is significantly improved.

[0133] When preparing the alkaline water electrolysis membrane electrode cathode of Comparative Example 1, since the nickel-aluminum alloy has not been surface modified, the slurry is uneven when it is prepared, resulting in uneven components of the slurry when it is coated on the substrate to form a membrane electrode, and the resulting membrane electrode has poor electrochemical performance.

[0134] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0135] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0136] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing an alkaline water electrolysis membrane electrode, characterized in that: The method comprises the following steps: Performing surface modification treatment on the nickel-based alloy to form an oxide layer or a hydroxide layer on the surface of the nickel-based alloy to obtain a modified nickel-based alloy; The modified nickel-based alloy is mixed with an auxiliary agent and a solvent for slurrying to obtain a membrane electrode slurry, wherein the auxiliary agent includes a dispersant and a thickener, and the mass ratio of the modified nickel-based alloy to the dispersant and the thickener is 1: (0.001-0.05): (0.001-0.01); Applying the membrane electrode slurry onto a substrate and hot pressing it to form a film to obtain a hot pressed membrane electrode; performing a leaching treatment of impurity elements on the hot-pressed membrane electrode to obtain a membrane electrode containing Raney nickel; The nickel-based alloy is a nickel-aluminum alloy and / or a nickel-zinc alloy; The impurity element leaching process comprises the following steps: placing the hot-pressed membrane electrode in a composite alkali solution for leaching treatment to remove the impurity elements in the nickel-based alloy, thereby obtaining a membrane electrode after impurity element leaching; The membrane electrode after the impurity elements are leached is placed in an acid solution for pickling treatment, and then the membrane electrode after pickling is washed with deionized water until it is neutral; The composite alkali solution contains a complexing agent and KOH or NaOH; the complexing agent is selected from one or more of sodium tartrate, sodium citrate, EDTA, sodium oxalate, Na2S and triethanolamine.

2. The method according to claim 1, wherein: The surface modification treatment method includes passivation in an oxidizing atmosphere, flame oxidation, alkali washing or plasma treatment.

3. The method according to claim 1, wherein: The modified nickel-based alloy has one or more of the following characteristics: (1) The contact angle of the modified nickel-based alloy is less than 90°; (2) The double electric layer Zeta potential value of the modified nickel-based alloy is 40-60 mV.

4. The method according to claim 1, wherein: The content of nickel in the nickel-based alloy is 30-70wt%; The particle size of the nickel-based alloy is 0.005-10 μm; The content of nickel in the Raney nickel is 90-99wt%.

5. The method according to claim 1, wherein: The substrate is selected from at least one of a polyphenylene sulfide diaphragm, a polyetheretherketone fiber diaphragm and a polysulfone fiber diaphragm; The hot pressing temperature is 50-500° C., and the hot pressing time is 1-60 min.

6. The method according to claim 1, wherein: The auxiliary agent also includes a binder, and the mass ratio of the modified nickel-based alloy to the binder is 1: (0.2-10); The mass ratio of the modified nickel-based alloy to the solvent is 1:(0.2-5).

7. The method according to claim 1, wherein: The mass ratio of the modified nickel-based alloy to the dispersant is 1:(0.001-0.03); The mass ratio of the modified nickel-based alloy to the thickener is 1:(0.001-0.04).

8. The method according to claim 6, wherein: The dispersant is a phosphate dispersant or an acrylic dispersant; The binder is at least one of perfluorosulfonic acid resin, polytetrafluoroethylene resin, polyethersulfone and fluororesin; The thickener is at least one of a cellulose ether thickener, a polyurethane thickener, and a modified polyurea thickener; The solvent is at least one of water, ethanol, isopropanol, propylene glycol, butanol and butylene glycol.

9. The method according to claim 8, wherein: The dispersant is at least one of sodium hexametaphosphate, potassium tripolyphosphate, acrylate, acrylic acid copolymer homopolymer and acrylic acid amine salt; The solvent is at least one of water, ethanol and isopropanol.

10. The method according to claim 1, wherein: The leaching treatment conditions include: temperature of 0-100°C, time of 5-24h, stirring speed of 500-10000rpm; Based on the weight of the composite alkali solution, the content of KOH or NaOH in the composite alkali solution is 10-30wt%; the molar ratio of the complexing agent to the aluminum element or the zinc element in the nickel-based alloy is 1.1-3.1; The conditions for the pickling treatment include: the concentration of the acid solution is 1-2 mol / L, the treatment time is 1-30 min; the acid solution is selected from one or more of dilute hydrochloric acid, sulfuric acid and nitric acid.

11. An alkaline water electrolysis membrane electrode prepared by the method according to any one of claims 1 to 10.

12. An electrolytic cell, characterized in that: The alkaline water electrolysis membrane electrode according to claim 11 is arranged in the cathode chamber of the electrolytic cell for accommodating the cathode.