Method for preparing membrane electrode by electrochemical deposition and application thereof
阅读说明：本技术 一种电化学沉积制备膜电极的方法及其应用 (Method for preparing membrane electrode by electrochemical deposition and application thereof ) 是由 王丽华 仇智 汪前东 何敏 杨海军 宋延林 于 2021-04-28 设计创作，主要内容包括：本发明公开一种电化学沉积制备膜电极的方法,涉及膜电极制备方法领域。首先对商业Nafion膜或质子交换膜进行特定预处理,然后在膜上先涂一层石墨烯,再通过电化学沉积负载铂微纳米粒子,实现铂微纳米粒子在石墨烯上的高度分散,达到既保持催化剂活性又减少用量的效果。电化学沉积的溶液中可添加特殊物质—离子液体,由于其具有极强的吸附能力,可改变电极与溶液界面的电化学特性,提高电沉积电流效率和改善电结晶条件。本发明工艺简单、易操作,质子交换膜与催化剂界面明显改善,电沉积效率高,还能有效提高膜电极性能,克服了现有热压法设备复杂,所用催化剂量大,热压的过程中较容易使膜脱水变形等缺点。(The invention discloses a method for preparing a membrane electrode by electrochemical deposition, and relates to the field of membrane electrode preparation methods. Firstly, a commercial Nafion membrane or a proton exchange membrane is subjected to specific pretreatment, then a layer of graphene is coated on the membrane, and platinum micro-nano particles are loaded through electrochemical deposition, so that the high dispersion of the platinum micro-nano particles on the graphene is realized, and the effects of keeping the activity of a catalyst and reducing the dosage are achieved. The special substance-ionic liquid can be added into the solution for electrochemical deposition, and because of its strong adsorption capacity, it can change the electrochemical characteristics of electrode and solution interface, raise electrodeposition current efficiency and improve electric crystallization condition. The invention has simple process and easy operation, obviously improves the interface of the proton exchange membrane and the catalyst, has high electrodeposition efficiency, can effectively improve the performance of the membrane electrode, and overcomes the defects of complicated equipment, large amount of used catalyst, easy dehydration and deformation of the membrane in the hot pressing process and the like of the traditional hot pressing method.)
1. A method for preparing a membrane electrode by electrochemical deposition is characterized by comprising the following steps:
1) pretreating a commercial Nafion membrane or a proton exchange membrane to prepare a bottom membrane of the membrane electrode;
2) dissolving graphene slurry in a solvent, performing ultrasonic dispersion for 30-60 min, and coating the solution on the base membrane obtained in the step 1) to obtain a base membrane containing graphene;
3) dissolving a platinum precursor, inorganic acid and ionic liquid in deionized water to prepare electrodeposition liquid;
4) in an electrochemical deposition device, taking the bottom film containing graphene prepared in the step 2) as a cathode, taking a titanium-coated platinum screen plate as an anode, performing energization deposition for 30-90 min at a certain temperature and constant current density, cleaning the surface of the bottom film containing graphene after the energization deposition by using deionized water, and drying to prepare a membrane electrode;
5) preparing a solution from a Nafion solution and isopropanol according to a certain proportion, coating the solution on the surface of the membrane electrode obtained in the step 4), cleaning the membrane electrode with deionized water and drying the membrane electrode to obtain the membrane electrode.
2. The method as claimed in claim 1, wherein the commercial Nafion membrane in step 1) is Nafion115 or Nafion 117; the proton exchange membrane is one of polybenzimidazole, sulfonated polysulfone, sulfonated polyetherimide, sulfonated polyether ether ketone or sulfonated polyaryletherketone.
3. The method as claimed in claim 1, wherein the Nafion membrane pretreatment mode in the step 1) is as follows: sequentially passing a Nafion membrane through H with the mass concentration of 2-5%2O2Heat treating the aqueous solution at 60-80 ℃ for 30-60 min, washing with deionized water, heat treating 0.5-1 mol/L sulfuric acid solution at 60-80 ℃ for 30-60 min, washing with deionized water and heat treating the deionized water at 60-80 ℃ for 30-6 min0 min; the pretreatment mode of the proton exchange membrane is as follows: and soaking the membrane in 1-3 mol/L acid water solution for 2-7 days.
4. The method of claim 3, wherein the acid is one of sulfuric acid, hydrochloric acid, formic acid, methanesulfonic acid, or phosphoric acid.
5. The method according to claim 1, wherein the graphene slurry in the step 2) is an aqueous conductive graphene slurry; the concentration of the graphene slurry is 0.08-0.16 g/mL; the solvent is an ethanol water solution or an isopropanol water solution, and the concentration of the solvent is 2.5-5 mg/mL; the coating mode is air gun spraying or spin coating by a spin coater;
preferably, a Nafion solution with the mass concentration of 5-10% is added into the solution, wherein the mass ratio of the Nafion solution to the graphene slurry is 0.15-0.5.
6. The method according to claim 1, wherein the platinum precursor in step 3) is chloroplatinic acid or tetraammineplatinum dichloride; the inorganic salt is hydrochloric acid or sodium dihydrogen phosphate and ammonium dihydrogen phosphate; the ionic liquid is imidazolyl ionic liquid;
preferably, the ionic liquid is one or a mixture of more of 1-ethyl-3-methyl-imidazole tetrafluoroborate, brominated 1-ethyl-3-methyl imidazole salt, 1-ethyl-3-methyl imidazole hexafluorophosphate or 1-butyl-3-methyl imidazole chloride salt.
7. The method according to claim 1, wherein the mass ratio of the inorganic salt to the platinum precursor in the electrodeposition solution of step 3) is 5 to 40; the content of the ionic liquid in the electrodeposition liquid is 10-50 mg/L, preferably 30-50 mg/L.
8. The method according to claim 1, wherein the temperature in step 4) is 30 to 70 ℃ and the current is 0.5 to 2.5A/dm2。
9. The method according to claim 1, wherein the mass concentration of the Nafion solution in the step 5) is 15-20%, and the volume ratio of the Nafion solution to the isopropanol is 0.5-2; the coating mode is air gun spraying or spin coating by a spin coater.
10. Use of a membrane electrode prepared according to any one of the methods of claims 1 to 9 in electrolysis of water or hydrogen fuel cells.
Technical Field
The invention relates to the field of membrane electrode preparation, in particular to a method for preparing a membrane electrode by electrochemical deposition and application thereof.
Background
In recent years, the demand for energy has been increasing, and the demand for moving from fossil fuels to renewable energy sources, such as wind energy, solar energy, biomass energy, hydroelectric power generation, and geothermal energy, has been pressing. On the way to the low-carbon energy society, hydrogen plays an important role as a secondary energy carrier. In future sustainable energy systems, it is possible that electrolysis of water will become the mainstream way of electricity-gas coupling power supply, transportation, heating and chemical sectors.
Membrane Electrode Assembly (MEA) is a key component for the electrolysis of water and the reaction, energy conversion and mass transport in fuel cells, and includes Gas Diffusion Layer (GDL), Catalyst Layer (CL) and PEM (proton exchange membrane). The existing method for preparing the membrane electrode can be summarized into two modes, wherein the first mode is the preparation of a carrier-free catalyst layer, namely, a catalyst is deposited on the surface of a proton exchange membrane in a chemical or physical deposition mode; the second is the preparation of the carrier catalyst layer, namely, the carrier catalyst is synthesized firstly and then is coated on the proton exchange membrane. The first membrane electrode preparation mode is more favored at present, and specific methods thereof include a hot pressing method, a chemical immersion reduction method, a transfer method, an electrochemical deposition method and the like, wherein the hot pressing method is the most widely used membrane electrode preparation method at present and is the earliest preparation method. The hot pressing method is that the cathode and anode catalyst layers are attached to two sides of the proton exchange membrane and then placed on the supporting surface of a hot press for hot pressing, or catalyst particles and a certain amount of carrier PTFE are mixed to prepare a catalyst film layer, and then the catalyst film layer and the proton exchange membrane are hot pressed to obtain the membrane electrode. The method has complicated equipment and large amount of used catalyst, and the membrane is easy to dehydrate and deform in the hot pressing process to influence the performance of the membrane.
The electrochemical deposition method is a membrane electrode preparation method with simple process and easy operation. In the previous researches, platinum is deposited on a diffusion layer carbon paper containing conductive carbon black or a carbon black carrier bonded by polytetrafluoroethylene, and then the carbon black carrier is directly assembled or hot-pressed with a proton exchange membrane.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a preparation method which is simple in process, easy to operate, high in electrodeposition efficiency and capable of obviously improving the interface between a proton exchange membrane and a catalyst and effectively improving the performance of a membrane electrode.
In order to achieve the above object, the present invention provides a method for preparing a membrane electrode by electrochemical deposition, comprising the following steps:
(1) pretreating a commercial Nafion membrane or a proton exchange membrane to prepare a bottom membrane of the membrane electrode;
(2) dissolving graphene slurry in a solvent, performing ultrasonic dispersion for 30-60 min, and coating the solution on the base membrane obtained in the step 1) to obtain a base membrane containing graphene;
(3) dissolving a platinum precursor, inorganic acid and ionic liquid in deionized water to prepare electrodeposition liquid;
(4) in an electrochemical deposition device, taking the bottom film containing graphene prepared in the step 2) as a cathode, taking a titanium-coated platinum screen plate as an anode, performing energization deposition for 30-90 min at a certain temperature and constant current density, cleaning the surface of the bottom film containing graphene after the energization deposition by using deionized water, and drying to prepare a membrane electrode;
(5) preparing a solution from a Nafion solution and isopropanol according to a certain proportion, coating the solution on the surface of the membrane electrode obtained in the step 4), cleaning the membrane electrode with deionized water and drying the membrane electrode to obtain the membrane electrode.
According to the invention, the step 1) commercial Nafion membrane is Nafion115 or Nafion 117.
According to the invention, the proton exchange membrane in the step 1) is one of polybenzimidazole, sulfonated polysulfone, sulfonated polyetherimide, sulfonated polyether ether ketone or sulfonated polyaryletherketone.
According to the invention, the pretreatment mode of the Nafion membrane in the step 1) is as follows: sequentially passing a Nafion membrane through H with the mass concentration of 2-5%2O2The water solution is subjected to heat treatment at 60-80 ℃ for 30-60 min, washed by deionized water, 0.5-1 mol/L sulfuric acid solution is subjected to heat treatment at 60-80 ℃ for 30-60 min, washed by deionized water and subjected to heat treatment at 60-80 ℃ for 30-60 min by deionized water.
According to the invention, the pretreatment mode of the proton exchange membrane in the step 1) is as follows: and soaking the membrane in 1-3 mol/L acid water solution for 2-7 days.
According to the invention, the acid is one of sulphuric acid, hydrochloric acid, formic acid, methanesulphonic acid or phosphoric acid.
According to the invention, the graphene slurry in the step 2) is aqueous conductive graphene slurry.
According to the invention, the concentration of the graphene slurry in the step 2) is 0.08-0.16 g/mL.
According to the invention, the solvent in the step 2) is an ethanol water solution or an isopropanol water solution, and the concentration of the ethanol water solution or the isopropanol water solution is 2.5-5 mg/mL;
preferably, a Nafion solution with the mass concentration of 5-10% can be added into the solution, wherein the mass ratio of the Nafion solution to the graphene slurry is 0.15-0.5.
According to the invention, the coating mode in the step 2) is air gun spraying or spin coating by a spin coater.
According to the invention, the platinum precursor in the step 3) is chloroplatinic acid or tetraammineplatinum dichloride, the inorganic salt is hydrochloric acid or sodium dihydrogen phosphate and ammonium dihydrogen phosphate, and the ionic liquid is imidazolyl ionic liquid;
preferably, the ionic liquid is one or a mixture of more of 1-ethyl-3-methyl-imidazole tetrafluoroborate, brominated 1-ethyl-3-methyl imidazole salt, 1-ethyl-3-methyl imidazole hexafluorophosphate or 1-butyl-3-methyl imidazole chloride salt.
According to the invention, the mass ratio of the inorganic salt to the platinum precursor in the electrodeposition liquid in the step 3) is 5-40.
According to the invention, the content of the ionic liquid in the electrodeposition liquid in the step 3) is 10-50 mg/L, and preferably 30-50 mg/L.
According to the invention, the temperature in the step 4) is 30-70 ℃, and the current is 0.5-2.5A/dm2。
According to the invention, the mass concentration of the Nafion solution in the step 5) is 15-20%, and the volume ratio of the Nafion solution to the isopropanol is 0.5-2.
According to the invention, the coating mode in the step 5) is air gun spraying or spin coating by a spin coater.
It is another object of the present invention to provide a membrane electrode for use in an electrolytic water or hydrogen fuel cell.
The technical scheme of the invention has the following beneficial effects:
(1) the method is different from the traditional membrane electrode preparation (firstly preparing the Pt/C catalyst and then fixing the Pt/C catalyst on the proton exchange membrane), adopts a layer-by-layer assembly mode, namely firstly fixing the graphene slurry on the proton exchange membrane, and then depositing a layer of platinum micro-nano particles on the surface layer of the graphene by adopting an electrochemical deposition method, can effectively reduce the interface internal resistance between the catalyst and the proton exchange membrane, and provides a new idea for the preparation of the membrane electrode.
(2) According to the invention, the graphene and the platinum micro-nano particles are sequentially deposited on the surface layer of the proton exchange membrane, so that the platinum micro-nano particles are highly dispersed on the graphene, and the effects of keeping the activity of the catalyst and reducing the dosage are achieved.
(3) The invention takes a trace amount of ionic liquid as an additive of the metal electrodeposition solution, and the ionic liquid has physicochemical properties of higher chemical and thermal stability, higher ionic conductivity, stronger adsorption capacity and the like. Because of its strong adsorption capacity, it can change the electrochemical characteristics of electrode and solution interface, raise electrodeposition current efficiency and improve electric crystallization condition.
Drawings
FIG. 1 is a schematic structural diagram corresponding to each step of the membrane electrode preparation method of the present invention;
fig. 2 is a surface electron microscope image of the membrane electrode prepared in example 1 of the present invention.
Detailed Description
Embodiments of the present invention will be described in more detail below.
Example 1
(1) A5 cm × 5cm Nafion115 membrane was placed in 5% H2O2Heat treating in water solution at 80 deg.C for 30min, repeatedly washing the membrane with deionized water, soaking the membrane in 80 deg.C deionized water, and heat treating for 30 min; then carrying out heat treatment for 30min at 80 ℃ in 0.5mol/L dilute sulfuric acid aqueous solution; repeatedly washing the membrane with deionized water, soaking the membrane in 80 deg.C deionized water for heat treatment for 30min, and naturally cooling;
(2) weighing 0.125g of ethanol, dissolving in 50mL of deionized water, and preparing a dilute ethanol aqueous solution; weighing 5g of graphene slurry (solid content is 3-18%, particle size is 7-12 microns, the number of graphene layers is less than 10), dissolving 1g of Nafion solution with mass concentration of 5% in the dilute ethanol aqueous solution, performing ultrasonic dispersion for 40min, and spraying the mixed solution onto the Nafion115 membrane prepared in the step (1) by using an air gun to prepare a base membrane containing graphene;
(3) weighing 1g of chloroplatinic acid, 6g of hydrochloric acid and 20mg of ionic liquid (1-ethyl-3-methylimidazolium hexafluorophosphate) and dissolving in 400mL of deionized water to prepare an electrodeposition solution; and (3) taking a titanium platinum-coated screen plate as an anode, taking the graphene-containing basement membrane prepared in the equal-area step (2) as a cathode, placing the cathode in an electrochemical deposition device, controlling the temperature of a constant-temperature water bath at 65 ℃, stirring, supplying power by a direct-current stabilized power supply, controlling the constant current, and controlling the stable current to be 1.5A/dm2Electrifying for electrodeposition for 60min, and after the electrodeposition is finished, cleaning the surface of the membrane by deionized water and drying to obtain a membrane electrode;
(4) mixing a 15% Nafion solution and isopropanol in a volume ratio of 1: 2 preparing a solution, spraying the solution on the surface of the membrane electrode prepared in the step (3), washing the surface of the membrane with deionized water, and drying to obtain the membrane electrode.
Example 2
(1) A5 cm × 5cm Nafion117 membrane was placed in 5% H2O2Heat treating in water solution at 80 deg.C for 30min, repeatedly washing the membrane with deionized water, soaking the membrane in 80 deg.C deionized water, and heat treating for 30 min; then to 0.5mol/L of dilute sulfuric acidHeat treating in water solution at 80 deg.C for 30 min; repeatedly washing the membrane with deionized water, soaking the membrane in 80 deg.C deionized water, heat treating for 30min, and naturally cooling.
(2) Weighing 0.125g of ethanol, dissolving the ethanol in 50mL of deionized water to prepare a dilute ethanol aqueous solution, weighing 8g of graphene slurry (with solid content of 3-18%, particle size of 7-12 microns and graphene layer number of less than 10 layers) and 4g of Nafion solution with mass concentration of 5%, dissolving the graphene slurry in the dilute ethanol aqueous solution, performing ultrasonic dispersion for 60min, and spin-coating the mixed solution on the Nafion117 film prepared in the step (1) by using a spin coater to prepare the base film containing graphene.
(3) Weighing 0.8g of tetraammineplatinum dichloride, 24g of sodium dihydrogen phosphate, 12g of ammonium dihydrogen phosphate and 12mg of ionic liquid (1-ethyl-3-methyl-imidazole tetrafluoroborate) and dissolving in 400mL of deionized water to prepare an electrodeposition solution; and (3) placing the titanium-coated platinum screen plate serving as an anode and the graphene-containing bottom membrane prepared in the equal-area step (2) serving as a cathode in an electrochemical deposition device, controlling the temperature in a constant-temperature water bath kettle at 30 ℃, supplying power to a direct-current stabilized power supply, and controlling the constant current with the stable current of 1.0A/dm2Electrifying for electrodeposition for 90 min, and after the electrodeposition is finished, cleaning the surface of the membrane by deionized water and drying to obtain a membrane electrode;
(4) mixing a 20% Nafion solution and isopropanol in a volume ratio of 1: 2 preparing a solution, spraying the solution on the surface of the membrane electrode prepared in the step (3), washing the surface of the membrane with deionized water, and drying to obtain the membrane electrode.
Example 3
(1) Soaking a polybenzimidazole membrane with the size of 5cm multiplied by 5cm in a sulfuric acid aqueous solution of 3mol/L for 7 days, repeatedly washing the polybenzimidazole membrane by deionized water, and naturally cooling the membrane.
(2) Weighing 0.25g of ethanol, dissolving the ethanol in 50mL of deionized water to prepare a dilute ethanol aqueous solution, weighing 4g of graphene slurry (solid content is 3-18%, particle size is 7-12 microns, the number of graphene layers is less than 10 layers), dissolving the graphene slurry in the dilute ethanol aqueous solution, performing ultrasonic dispersion for 60min, and spraying the mixed solution onto the proton exchange membrane prepared in the step (1) by using an air gun to prepare a base membrane containing graphene;
(3) dissolving 1g of chloroplatinic acid, 5g of hydrochloric acid and 16mg of ionic liquid (1-ethyl-3-methyl-imidazole tetrafluoroborate) in 400mL of deionized water to prepare an electrodeposition solution; and (3) placing the titanium-coated platinum screen plate serving as an anode and the graphene-containing bottom membrane prepared in the equal-area step (2) serving as a cathode in an electrochemical deposition device, controlling the temperature in a constant-temperature water bath kettle at 70 ℃, stirring, supplying power by a direct-current stabilized power supply, and controlling the constant current with the stable current of 2.5A/dm2Electrifying for electrodeposition for 30min, and after the electrodeposition is finished, cleaning the surface of the membrane by deionized water and drying to obtain a membrane electrode;
(4) mixing a 20% Nafion solution and isopropanol in a volume ratio of 1: 1 preparing a solution, spraying the solution on the surface of the membrane electrode prepared in the step (3), washing the surface of the membrane with deionized water, and drying to obtain the membrane electrode.
Example 4
(1) Soaking sulfonated polyether ether ketone with the size of 5cm multiplied by 5cm in 1mol/L hydrochloric acid water solution for 2 days, repeatedly washing with deionized water, and naturally cooling the membrane.
(2) Weighing 0.2g of isopropanol, dissolving the isopropanol in 50mL of deionized water to prepare an isopropanol aqueous solution, weighing 4g of graphene slurry (solid content is 3-18%, particle size is 7-12 mu m, number of graphene layers is less than 10 layers), dissolving 2g of Nafion solution with mass concentration of 5% in the diluted isopropanol aqueous solution, performing ultrasonic dispersion for 30min, and spraying the mixed solution onto the proton exchange membrane prepared in the step (1) by using an air gun to prepare a base membrane containing graphene;
(3) dissolving 1g of chloroplatinic acid, 5g of hydrochloric acid and 20mg of ionic liquid (1-ethyl-3-methyl-imidazole tetrafluoroborate) in 400mL of deionized water to prepare an electrodeposition solution; and (3) placing the titanium-coated platinum screen plate serving as an anode and the graphene-containing bottom membrane prepared in the equal-area step (2) serving as a cathode in an electrochemical deposition device, controlling the temperature in a constant-temperature water bath kettle at 50 ℃, stirring, supplying power by a direct-current stabilized power supply, and controlling the constant current with the stable current of 0.5A/dm2Electrifying for electrodeposition for 60min, and after the electrodeposition is finished, cleaning the surface of the membrane by deionized water and drying to obtain a membrane electrode;
(4) mixing a 20% Nafion solution and isopropanol in a volume ratio of 1: 1 preparing a solution, spraying the solution on the surface of the membrane electrode prepared in the step (3), washing the surface of the membrane with deionized water, and drying to obtain the membrane electrode.