Preparation method of catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water

Abstract

A preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water belongs to the field of electrolyzing water, and comprises the following steps: 1) mixing a polymerizable monomer, a catalyst, a conductive agent, an initiator and a solvent to prepare uniform slurry; 2) coating the slurry on the surface of a gas diffusion layer or a film; and 3) acting on the surface of the coating slurry through light, heat or electric energy, so that the polymerizable monomer is polymerized to form an ionomer, and the ionomer, the catalyst and the gas diffusion layer or film form an integrated electrode. According to the invention, monomers are polymerized to form an ionomer, and a three-dimensional cross-linked network structure is constructed between a catalyst and a gas diffusion layer or a film, so that the integrated electrode is prepared. In the water electrolysis reaction, the method can effectively inhibit the catalyst on the surface of the electrode from falling off, and the service life of the electrode is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the field of electrolyzed water, and particularly to a preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzed water. Background Art

[0002] In recent years, the global energy transition has accelerated. As the most abundant element on earth, hydrogen energy has the characteristics of high energy density and only producing water when burning, which helps to address climate change, reduce greenhouse gas emissions, and achieve sustainable energy development. It is considered to be one of the most ideal energy sources in the future.

[0003] Hydrogen production by electrolyzing water plays an important role in the hydrogen production industry. Hydrogen production by electrolyzing water uses water as raw material, and the reaction products are only hydrogen and oxygen, without greenhouse gas or other pollutant emissions. The purity of hydrogen produced by electrolyzing water is extremely high (usually up to more than 99.9%). The electrolyzed water hydrogen production system can be coupled with a renewable energy power generation system to convert unstable renewable energy (such as wind power, solar energy, etc.) into storable and transportable hydrogen energy, solving the intermittency and volatility problems of renewable energy.

[0004] The electrode is the core component in the electrolyzed water hydrogen production system, and its performance directly determines the efficiency, energy consumption, and cost of the electrolyzed water system. During the electrolysis of water, bubbles generated on the electrode surface, temperature fluctuations, or pressure changes are likely to cause the peeling of active substances on the electrode surface, thereby leading to an increase in the reaction energy barrier and a decrease in the overall life of the electrolysis system. Considering the future industrial and commercial applications of electrolyzed water, improving the electrode stability is an important direction in the research and development of electrolyzed water systems under high current density electrolysis environments. Summary of the Invention

[0005] The purpose of the present invention is to solve the above problems in the prior art, and provide a preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzed water. Using a polymerizable monomer as the ionomer, a three-dimensional cross-linked network is constructed between the catalyst, gas diffusion layer, or membrane to form an integrated electrode, improving the stability of the electrode used in the electrolyzed water system and enhancing the electrode life.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzed water, comprising the following steps:

[0008] 1) Mix a polymerizable monomer, a catalyst, a conductive agent, an initiator, and a solvent to prepare a uniform slurry;

[0009] 2) Coat the slurry on the surface of a gas diffusion layer or a membrane;

[0010] 3) Applying light, heat or electrical energy to the surface of the coating slurry to polymerize the polymerizable monomer to form an ionomer, and forming an integrated electrode with the catalyst, gas diffusion layer or membrane.

[0011] The formed ionomer has ion-conducting properties and includes at least one of polyacrylic acid, polyaryl fluoroketone, polyethylene imine derivatives, polyurethane derivatives, polyvinyl alcohol and its derivatives, polybenzimidazole, polyimide, polystyrene, and perfluorosulfonic acid ion exchange resins.

[0012] The catalyst is at least one of an anode catalyst or a cathode catalyst of a water electrolysis system.

[0013] The anode catalyst includes an anode oxygen evolution catalyst such as a nickel-iron-based, nickel-cobalt-based or molybdenum-based metal compound; the cathode catalyst includes a cathode hydrogen evolution catalyst such as a nickel-molybdenum-based, cobalt-phosphorus-based or platinum-based metal compound.

[0014] The initiator may be selected from acetophenone, benzophenone, dibenzoyl peroxide, diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide, etc., and the solvent may be selected from water, ethanol, methanol, isopropanol, etc.

[0015] The material of the gas diffusion layer is selected from carbon paper, nickel foam, cobalt foam, nickel mesh, and cobalt mesh; the material of the membrane is selected from perfluorosulfonic acid ion exchange membrane, polyaromatic membrane, polyolefin membrane, polybenzimidazole membrane, and polyimide membrane.

[0016] The energy action mode is ultraviolet light irradiation, heating, laser irradiation or electron beam irradiation, and the energy action equipment can be selected from a baking lamp, an ultraviolet lamp, a laser generator, an electron beam irradiation equipment, etc.

[0017] A catalyst-ionomer-membrane cross-linked structure electrode for water electrolysis is prepared by the preparation method of the invention.

[0018] The catalyst-ionomer-membrane cross-linked structure electrode for water electrolysis comprises a three-dimensional cross-linked network formed by polymerization of polymerizable monomers, the three-dimensional cross-linked network encapsulates the catalyst and the conductive agent and forms an integrated structure with the gas diffusion layer or the membrane, and the ionomer has ion conductivity.

[0019] The three-dimensional cross-linked network is a polyacrylic acid network, and the polyacrylic acid provides ion transmission channels through the dissociation of carboxylic acid groups.

[0020] The application of the catalyst-ionomer-membrane cross-linked structure electrode for water electrolysis is used to prepare a water electrolysis hydrogen production system, including an alkaline water electrolysis system, an anion exchange membrane water electrolysis system and a proton exchange membrane water electrolysis system.

[0021] Compared with the prior art, the beneficial effects achieved by the technical solution of the present invention are as follows:

[0022] 1. The present invention utilizes the polymerization reaction of polymerizable monomers under the action of energy such as light, heat, and electricity to construct a three-dimensional cross-linked network and form an integrated structure between the catalyst, gas diffusion layer or membrane. The electrode preparation method of the present invention is simple, rapid and efficient, and has the prospect of large-scale industrial production.

[0023] 2. The present invention uses nickel-iron-based and nickel-molybdenum-based non-precious metal catalysts as electrocatalysts for driving the electrolysis of water reaction, uses carbon nanotubes as conductive agents, and uses acrylic acid as polymerizable monomers. Under the action of ultraviolet light, acrylic acid polymerizes into polyacrylic acid, which coats the catalyst and conductive agent, and forms a tight cross-linked network structure with the surface of the gas diffusion layer. The electrode prepared by this method has a good catalyst-ionomer-gas diffusion layer contact interface, makes full use of the ion conduction characteristics of polyacrylic acid, constructs an efficient ion transport network, and improves the stability of the electrolytic water system.

[0024] 3. Taking the anion exchange membrane electrolytic water system assembled by the present invention as an example, the anode uses NiFe-LDH catalyst, the diaphragm uses anion exchange membrane, at a reaction area of 1×1 cm 2 current density, the cathode uses the catalyst-ionomer-membrane cross-linked structure electrode prepared by the present invention. Compared with the electrode with no cross-linked network structure used at the cathode (the voltage rapidly rises from 2.1 V to 2.5 V within 5 h), after the electrode prepared by the present invention is assembled into the electrolytic cell, the voltage rises from 2.1 V and stabilizes at 2.25 V for more than 175 h. Description of the Drawings

[0025] Figure 1 It is a physical picture of the catalyst-ionomer-membrane cross-linked structure electrode prepared in Example 1.

[0026] Figure 2 It is a SEM picture of the catalyst-ionomer-membrane cross-linked structure electrode prepared in Example 1; among them, Figure 2 a in it is a SEM picture with a scale of 5 μm, Figure 2 b in it is a SEM picture with a scale of 2 μm.

[0027] Figure 3 It is a SEM picture of the electrode with no cross-linked network structure prepared in Comparative Example 1; among them, Figure 3 a in it is a SEM picture with a scale of 5 μm, Figure 3 b in it is a SEM picture with a scale of 2 μm.

[0028] Figure 4 It is a performance picture of the 10 h electrolytic water system of Example 1 and Comparative Example 1.

[0029] Figure 5 Performance diagram of the long-term electrolyzed water system of Example 1. Detailed implementation mode

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] Taking the preparation of the cathode electrode of the anion exchange membrane electrolyzed water system of the present invention as an example, the implementation process and specific principle of this method are described.

[0032] In the anion exchange membrane electrolyzed water system, nickel foam is selected as the gas diffusion layer, nickel-molybdenum-based metal catalyst as the hydrogen evolution catalyst, carbon nanotubes as the conductive agent, acrylic acid as the polymerizable monomer, and ultraviolet lamp as the energy action device. A hydrogen evolution cathode electrode is prepared by the preparation method of the present invention, and an electrolytic cell is built on the basis of a small membrane electrode flow reactor to evaluate the stability of the prepared electrode.

[0033] The specific principle is as follows: Using acrylic acid monomer as the ionomer, it is mixed with the catalyst, conductive agent, initiator, and solvent to form a uniformly blended slurry. After the slurry is uniformly coated on the surface of the gas diffusion layer, it is irradiated with ultraviolet light. At this time, the acrylic acid monomer undergoes a polymerization reaction to form a polyacrylic acid ionomer network that uniformly coats the catalyst and forms a stable cross-linked network between the catalyst, conductive agent, and gas diffusion layer, effectively inhibiting the shedding of the catalyst during the electrolysis process.

[0034] It should be noted that in the present invention, acrylic acid monomer is used, and the polymerized polyacrylic acid is a high molecular polymer containing a large number of carboxylic acid groups (-COOH). In the electrolyte, the carboxylic acid groups can be partially dissociated into carboxylate and protons ( ), which can migrate through the following two mechanisms: Grotthuss mechanism (hopping conduction): Protons hop between adjacent carboxylic acid groups through the hydrogen bond network; Vehicle mechanism (carrier diffusion): Protons combine with water molecules to form hydronium ions and migrate through diffusion. Since polyacrylic acid exists as an ionomer and forms a stable three-dimensional cross-linked network structure as a binding medium, depending on the dissociation ability of the carboxylic acid groups and the dynamic behavior of the polymer chains, polyacrylic acid can form an efficient ion transport channel in the electrolyte, improving the electrolysis reaction efficiency and electrode stability.

[0035] (1) Design of the slurry formula in the present invention:

[0036] The slurry formulation in the present invention comprises a catalyst, a conductive agent (such as carbon, metal, etc.), an ionomer monomer, an initiator, and a solvent. After fully mixing the catalyst, conductive agent, ionomer monomer, initiator, and solvent evenly in a container, the slurry in the present invention is obtained.

[0037] (2)Preparation method of the electrode in the present invention:

[0038] The prepared slurry is evenly coated on the surface of the gas diffusion layer. Subsequently, the gas diffusion layer is placed under an ultraviolet lamp for irradiation and baking until the solvent is completely evaporated. The ionomer monomer undergoes a polymerization reaction under ultraviolet light irradiation, coating the catalyst and conductive agent, and forming a tight three-dimensional cross-linked network structure with the surface of the gas diffusion layer, thereby preparing an integrated electrode.

[0039] (3)Selection of components of the membrane electrode flow reactor and construction method of the electrolytic cell in the present invention:

[0040] The integrated electrode prepared in the present invention is applicable to electrolytic cells of various specifications, including but not limited to commercial electrolytic cells, customized electrolytic cells, etc. Taking a commonly used membrane electrode flow reactor on the market as an example in the present invention, an electrolytic cell is assembled and the stability of the integrated electrode prepared in the present invention is evaluated.

[0041] In the present invention, a plate - cathode - diaphragm - anode - plate tightly attached membrane electrode flow reactor is assembled. The plates of this assembly can be made of materials such as titanium plates, stainless steel plates, nickel plates, etc.; the liquid flow channels can be selected as fully hollow channels or serpentine channels; the diaphragm can be selected as a cation exchange membrane, a proton exchange membrane, or an anion exchange membrane; the inlet and outlet ports can be selected as external thread tower connectors or quick - connect joints made of iron or plastic; a silica gel gasket is used as a buffer between the bipolar plates. Finally, holes are drilled around the two bipolar plates, and appropriate plastic or stainless steel bolts and nuts are selected and tightened to fix the membrane electrode flow reactor.

[0042] The construction method of the electrolytic cell in the present invention is as follows. First, a peristaltic pump is used to pump the electrolyte in the container into the anode and cathode flow channels of the membrane electrode flow reactor respectively, and then its discharged liquid is refluxed to the original electrolyte container to achieve the purpose of circulating flow. After that, the membrane electrode flow reactor is connected to an electrochemical workstation, and a certain voltage or current is applied to the membrane electrode flow reactor to drive the occurrence of the water electrolysis reaction in the reactor and maintain the reaction for a long time.

[0043] Example 1

[0044] (1)Preparation of the cathode catalyst:

[0045] First, add 2.4 mmol of Ni(NO3)2·6H2O and 0.6 mmol of (NH4)6Mo7O 24·4H2O, then add 30mL of deionized water and stir thoroughly until the drug is completely dissolved, then pour the solution into a hydrothermal reactor and react at 150°C for 8h. The obtained powder is washed and dried, and then the powder is annealed in a tube furnace in a H2 / Ar atmosphere at a temperature of 500°C for 2h to obtain the desired nickel-molybdenum-based catalyst.

[0046] (2) Configuration of electrolyte precursor slurry:

[0047] First, 8 mg of nickel-molybdenum-based catalyst, 2 mg of carbon nanotubes, 300 μL of ethanol, 30 μL of acrylic acid, and 0.4 mg of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide were added into a certain amount container, and the mixture was shaken thoroughly to be evenly mixed to obtain an electrolyte precursor slurry.

[0048] (3) Preparation of cathode electrode:

[0049] 200 μL of electrolyte precursor slurry was dropped on a square nickel foam with a side length of 1 cm and a thickness of 0.5 mm, and then transferred to a 10 W ultraviolet lamp for irradiation for 20 seconds. After the slurry layer solidified and formed a tight connection with the nickel foam, the electrode was obtained.

[0050] Comparative Example 1

[0051] Compared with Example 1, the difference is that in this comparative example, polyacrylic acid is directly added as an ionomer without ultraviolet light irradiation, thereby obtaining an electrode without forming a cross-linked network structure.

[0052] like Figures 1 - 3 As shown, it can be found through scanning electron microscopy that, under the action of ultraviolet light, acrylic acid in Example 1 polymerizes to form a cross-linked network to coat the catalyst particles, thereby constructing a good catalyst-ionomer contact interface. In contrast, no cross-linked network structure was observed in the electrode formed by directly adding polyacrylic acid as an ionomer without ultraviolet light irradiation.

[0053] The assembly of the membrane electrode reactor and the electrode stability test in the present invention are as follows.

[0054] The electrode performance in the present invention is evaluated by loading it into an electrolytic cell for water electrolysis reaction, and a control test is performed by a controlled variable method. The specific method is as follows: a control test is performed in a small membrane electrode flow reactor with a reaction area of ​​1×1 cm. 1M KOH is circulated between the cathode and the anode as an electrolyte; NiFe-LDH is used as an oxygen evolution catalyst at the anode; an anion exchange membrane is used as the diaphragm; the cathode uses the hydrogen evolution electrode prepared in Example 1 of the present invention, and the control group uses the hydrogen evolution electrode prepared in Comparative Example 1. The assembled membrane electrode reactor is connected to an electrochemical workstation, a current of 1A is applied, and the trend of voltage change over time is observed.

[0055] As Figures 4 - 5 shown, for the electrolyzed water system composed of the hydrogen evolution electrode without the ionomer cross-linked structure in Comparative Example 1, the voltage rapidly increased from 2.1 V to 2.5 V within 3 h, and the voltage showed a sharp decay, meaning that the stability performance was very unsatisfactory. For the electrolyzed water system composed of the hydrogen evolution electrode with the ionomer cross-linked structure in Example 1, the stability was greatly improved, and the voltage only increased from 2.1 V to about 2.25 V and stably operated for more than 175 h.

Claims

1. A preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water, characterized in that, Comprising the following steps: 1) Mixing polymerizable monomers, a catalyst, a conductive agent, an initiator, and a solvent to prepare a homogeneous slurry; 2) Coating the slurry on the surface of a gas diffusion layer or a membrane; 3) Acting on the surface of the coated slurry with light, heat, or electrical energy to polymerize the polymerizable monomers to form an ionomer, and form an integrated electrode with the catalyst, the gas diffusion layer, or the membrane.

2. The preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 1, characterized in that: The formed ionomer comprises at least one of polyacrylic acid, polyaryl fluoroketone, polyethyleneimine derivatives, polyurethane derivatives, polyvinyl alcohol and its derivatives, polybenzimidazole, polyimide, polystyrene, perfluorosulfonic acid-based ion exchange resins.

3. The preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 1, characterized in that: The catalyst is at least one of an anode catalyst or a cathode catalyst for an electrolytic water system.

4. The preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 3, characterized in that: The anode catalyst comprises at least one of nickel-iron-based, nickel-cobalt-based, or molybdenum-based metal compounds; the cathode catalyst comprises at least one of nickel-molybdenum-based, cobalt-phosphorus-based, or platinum-based metal compounds.

5. The preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 1, characterized in that: The material of the gas diffusion layer is selected from carbon paper, nickel foam, cobalt foam, nickel mesh, cobalt mesh; the material of the membrane is selected from perfluorosulfonic acid-based ion exchange membranes, polyaromatic membranes, polyolefin membranes, polybenzimidazole membranes, polyimide membranes.

6. The preparation method of a catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 1, characterized in that: The mode of energy action is ultraviolet light irradiation, heating, laser irradiation, or electron beam irradiation.

7. A catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water, characterized in that: Prepared by the preparation method according to any one of claims 1 to 6.

8. The catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 7, wherein: Comprising a three-dimensional cross-linked network formed by polymerization of polymerizable monomers, the three-dimensional cross-linked network coating the catalyst and the conductive agent and forming an integrated structure with the gas diffusion layer or the membrane, and the ionomer having ion conduction ability.

9. The catalyst-ionomer-membrane cross-linked structure electrode for electrolyzing water according to claim 8, characterized in that: The three-dimensional cross-linked network is a polyacrylic acid network, and the polyacrylic acid provides an ion transport channel through the dissociation of carboxyl groups.

10. Use of the catalyst-ionomer-membrane crosslinked structure electrode for electrolyzing water according to claim 7, characterized in that: For preparing an electrolytic water hydrogen production system, including an alkaline electrolytic water system, an anion exchange membrane electrolytic water system, and a proton exchange membrane electrolytic water system.

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