Preparation method and application of hydrogel composite electrode

Abstract

This invention discloses a method for preparing a hydrogel composite electrode and its application, belonging to the field of electrocatalyst materials technology. The method for preparing the hydrogel composite electrode of this invention includes the following steps: mixing polymer monomers in a solvent to obtain a monomer solution, or mixing polymer monomers and a polymer substrate in a solvent to obtain a monomer solution; adding an initiator and a crosslinking agent to the monomer solution to obtain a precursor liquid; loading the precursor liquid onto the electrode surface and performing a polymerization reaction to obtain the hydrogel composite electrode. Compared with traditional catalyst electrodes, the hydrogel composite electrode disclosed in this invention significantly increases hygroscopicity without changing the macroscopic dimensions and conductivity of the electrode material. This is beneficial for solving the key problem of mass transfer rate limiting in electrochemical reactions involving water vapor, and can significantly improve the electrode's activity and long-term stability, thus having great application value.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst materials technology, and in particular to a method for preparing and applying a hydrogel composite electrode. Background Technology

[0002] In the field of steam-involved electrocatalytic reactions, especially key processes such as water electrolysis (WE) and carbon dioxide reduction (CO2RR), the design of reaction conditions and the optimization of electrode materials constitute key research directions driving the development of this field. These reactions are not only crucial for achieving efficient steam electrocatalytic conversion, but also have profound significance for promoting the sustainable development of green energy. However, steam-involved catalytic reactions face a series of challenges in practical applications.

[0003] Specifically, the preparation of catalysts for these water vapor-involved catalytic reactions often requires the use of rare or precious metal materials, which greatly limits the economic feasibility of their large-scale application. Furthermore, even catalysts that perform well under laboratory conditions often struggle to maintain their catalytic activity for extended periods in actual reactions, highlighting the urgent need to address stability issues. In addition, low water vapor mass transfer efficiency is another key factor restricting the efficiency of these reactions. In water electrolysis, effective mass transfer of water molecules in water vapor is crucial for maintaining stable operation at high current densities over long periods. However, current technologies still have significant shortcomings in this regard, resulting in generally low current densities in water vapor-supplied electrolyzers during long-term operation and poor stability under high current density conditions.

[0004] Taking the WE reaction involving water vapor as an example, due to the low mass transfer efficiency of water molecules in water vapor, the current density of water vapor-supplyed electrolyzers is currently low (approximately 10-40 mA cm⁻¹) during long-term operation (>10 hours). -2 ), or at high current densities (>50 mA cm⁻¹) -2 The catalyst exhibits poor stability (<2h), among other issues. While existing technologies have made some progress in catalyst optimization (using noble metal catalysts, developing efficient non-noble metal catalysts, designing metal-organic framework catalysts, and controlling catalyst surface morphology) to address these problems, challenges remain, including insufficient long-term catalyst stability, limited gas diffusion, and difficulties in large-scale application, necessitating further improvements. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a hydrogel composite electrode and its application, thereby solving the aforementioned problems in the background art. Compared with traditional catalyst electrodes, the hydrogel composite electrode disclosed in this invention significantly increases hygroscopicity without changing the macroscopic size and conductivity of the electrode material. This is beneficial for solving the key problem of mass transfer rate limiting in electrochemical reactions involving water vapor, and can significantly improve the electrode's activity and long-term stability, thus having great application value.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] One of the technical solutions of this invention is to provide a method for preparing a hydrogel composite electrode, comprising the following steps:

[0008] Monomer solutions are prepared using either method A or method B;

[0009] Method A involves mixing polymer monomers in a solvent to obtain a monomer solution.

[0010] Method B involves mixing the polymer monomer and the polymer substrate in a solvent to obtain a monomer solution.

[0011] An initiator and a crosslinking agent are added to the monomer solution to obtain a precursor solution;

[0012] The precursor fluid is loaded onto the electrode surface and polymerized to obtain the hydrogel composite electrode.

[0013] Preferably, the polymer monomer is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide and / or acrylamide.

[0014] Preferably, the polymer base is polyvinyl alcohol and / or chitosan.

[0015] Preferably, in method B, the total concentration of the polymer monomer and polymer substrate in the precursor fluid is 0.5-3 mol / L, and the mass ratio of the polymer monomer to the polymer substrate is 2.5-5.

[0016] In Method A, the total concentration of the polymer monomer in the precursor fluid is 0.35-2.5 mol / L.

[0017] Preferably, the initiator is potassium persulfate, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone or azobisisobutyronitrile; and the crosslinking agent is N,N'-methylenebisacrylamide.

[0018] Preferably, the amount of the initiator is 0.1-5% of the molar amount of the polymer monomer.

[0019] Preferably, the amount of crosslinking agent used is 0.1-5% of the molar amount of the polymer monomer.

[0020] Preferably, the electrode is a porous self-supporting electrode material.

[0021] More preferably, the porous self-supporting electrode material is carbon foam or metal foam.

[0022] Preferably, the precursor liquid is loaded onto the electrode surface by drop coating, spray coating, spin coating, or immersion.

[0023] Preferably, the loading amount of the precursor fluid on the electrode is 0.5-1.2 mL / cm². 3 .

[0024] Preferably, the polymerization reaction is thermal polymerization, catalytic polymerization, or photopolymerization; the thermal polymerization temperature is 65°C and the time is 2 hours; the catalytic polymerization temperature is 20-25°C and the time is 24 hours; the photopolymerization temperature is 20-25°C, the light wavelength is 254-365 nm, and the time is 10-30 minutes.

[0025] Preferably, after the polymerization reaction is completed, the process further includes purifying the electrode material in water to remove excess monomers, initiators, crosslinking agents, and other impurities; the purification is performed 2-5 times, with each soaking time being 2-20 hours.

[0026] More preferably, after the purification is completed, the process further includes freezing and vacuum drying steps; the freezing temperature is -40 to -20°C and the time is 1.5 to 12 hours; the vacuum degree of the vacuum drying is -0.08 to -0.1 mPa and the time is 1.5 to 12 hours.

[0027] More preferably, after the vacuum drying is completed, the process further includes immersing the electrode material in an electrolyte for static activation; the concentration of the electrolyte is 0.5-7.6 mol / L, and the type is potassium hydroxide or sulfuric acid, and the static activation time is 1-2 hours.

[0028] Immersing the electrode material in the electrolyte helps to enhance the hygroscopicity of the hydrogel composite electrode.

[0029] The second technical solution of the present invention provides a hydrogel composite electrode obtained according to the above preparation method.

[0030] The third technical solution of the present invention provides an application of the above-mentioned hydrogel composite electrode in electrocatalytic reactions involving water vapor.

[0031] The technical principle of this invention is as follows:

[0032] In the hydrogel composite electrode prepared by this invention, the hydrogel appears as a thin film (0.3-1.0 μm) on the electrode material. The large number of hydrophilic groups in the hydrogel gives the hydrogel composite electrode a strong water vapor capture ability. At the same time, the structural characteristics of the hydrogel film can improve the efficiency and stability of water vapor electrocatalytic reaction without affecting the performance of the porous electrode in the electrochemical reaction involving water vapor.

[0033] When the electrode material to be loaded is a porous self-supporting electrode material, the thickness of the hydrogel loading layer needs to be strictly limited to the range of 0.3-1.0 μm by adjusting the precursor fluid loading amount / reaction conditions. If the hydrogel loading layer is too thick, it can easily lead to swelling and pore blockage, affecting the active sites; if it is too thin, it will cause insufficient modification effect and inadequate stability. This invention, through optimized reaction conditions, achieves the technical effect of maximizing the advantage of the large specific surface area of ​​the porous electrode while ensuring that the hydrogel loading layer swells without blocking pores.

[0034] The beneficial technical effects of the present invention are as follows:

[0035] Compared with traditional catalyst electrodes, the hydrogel composite electrode disclosed in this invention has a significantly increased hygroscopicity without changing the macroscopic size and conductivity of the electrode material. This is beneficial for solving the key problem of mass transfer rate limiting in electrochemical reactions involving water vapor, and can significantly improve the activity and long-term stability of the electrode, thus having great application value.

[0036] The hydrogel composite electrode preparation method disclosed in this invention is simple and quick, and is suitable for porous self-supporting catalyst electrodes. It can maximize the advantage of the large specific surface area of ​​porous electrodes while ensuring that the hydrogel swells without clogging the pores. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the preparation process of the hydrogel composite electrode of the present invention.

[0039] Figure 2 This is a plan-field achromatic micro-objective image of the hydrogel composite electrode of Embodiment 1 of the present invention. Among them, (a) is hydrogel-S-NiFeLDH@NF, and (b) is hydrogel-NiMoN@NF.

[0040] Figure 3The images shown are scanning electron microscope (SEM) images of the hydrogel composite electrode of Example 1 of the present invention. (a) shows hydrogel-S-NiFeLDH@NF, and (b) shows hydrogel-NiMoN@NF.

[0041] Figure 4 The figures show the stability test results of the hydrogel composite electrode in the experimental group and the conventional electrode without hydrogel coating in the control group when used in a water vapor-involved electrolytic hydrogen production reaction.

[0042] Figure 5 This is a comparison chart showing the performance of the hydrogel composite electrode in the experimental group of this invention in the electrolytic hydrogen production reaction involving water vapor, and the data of water vapor electrolyzers in existing literature.

[0043] Figure 6 This is a schematic diagram of the steam electrolysis cell in this invention. Detailed Implementation

[0044] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0045] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0046] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0047] The terms “comprising,” “including,” “having,” “containing,” etc., used in this invention are all open-ended terms, meaning that they include but are not limited to.

[0048] In recent years, hydrogels, as highly hydrophilic polymers with unique physical and chemical properties, have attracted much attention. They are three-dimensional network materials containing a large amount of water, exhibiting reversible water absorption, good biocompatibility, flexibility, and abundant positively charged carbon atoms. These properties give hydrogels unique advantages in various applications such as biology, photoelectrochemistry, oxygen evolution reactions, and atmospheric water harvesting. Therefore, introducing hydrogels onto the surface of electrode catalysts to design a hydrogel-based electrode material for water vapor electrocatalytic reactions has significant research value.

[0049] Unless otherwise specified, "room temperature" in this invention refers to 10-30°C.

[0050] All raw materials used in the following embodiments of the present invention are commercially available products.

[0051] The methods for preparing the conventional anode electrode and the conventional cathode electrode without hydrogel used in the following embodiments of the present invention are as follows:

[0052] (1) The porous self-supporting electrode material, nickel foam (porosity of about 94.4% and pore size of about 60 ppi), was placed in 2M HCl, ethanol and acetone respectively and sonicated for 15 min each to remove the oxide layer. Then it was washed with deionized water and dried at room temperature overnight.

[0053] (2) To obtain the S-NiFeLDH@NF anode electrode, 0.5906 g of ferric nitrate nonahydrate and 0.0844 g of sodium thiosulfate pentahydrate were first dissolved in 15 mL of deionized water. Then, the washed nickel foam obtained in (1) was immersed in the solution and shaken at 180 rpm for 5 minutes. The sample was then immediately removed from the solution, washed several times with deionized water, and dried in a nitrogen (N2) atmosphere to obtain a conventional anode electrode (denoted as S-NiFeLDH@NF) without hydrogel.

[0054] (3) To obtain the NiMoN@NF cathode, 0.04 M ferric nitrate hexahydrate and 0.01 M ammonium molybdate tetrahydrate were dissolved in 25 mL of deionized water. The solution was then transferred together with the nickel foam obtained in (1) to a 100 mL autoclave. The autoclave was placed in an oven and subjected to a hydrothermal reaction at 150 °C for 6 hours. After the reaction was completed, the generated electrode was collected, washed sequentially with deionized water, ethanol, and deionized water, and then vacuum dried overnight at 60 °C. After drying, the sample was immersed in 20 mL of a solution (containing 0.1 M ferric nitrate hexahydrate, 0.0125 M ammonium molybdate tetrahydrate, and 0.15 M urea) and bathed in a water bath at 90 °C for 2 hours. Subsequently, the sample underwent the same cleaning and drying steps as described above. Finally, the sample was subjected to thermal nitriding treatment at 400°C for 2 hours in a tube furnace with a mixture of 150 standard cubic centimeters of ammonia gas (volume concentration of 80%) to obtain a conventional cathode electrode without hydrogel (denoted as NiMoN@NF).

[0055] Figure 1 This is a schematic diagram of the preparation process of the hydrogel composite electrode of the present invention.

[0056] Example 1

[0057] A method for preparing a hydrogel composite electrode without a polymer substrate, the specific steps of which are as follows:

[0058] (1) Weigh 7.23 mmol of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide into a beaker, add 5.7 mL of deionized water to remove dissolved oxygen, and sonicate until [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonylpropyl)ammonium hydroxide dissolves and is uniformly dispersed in the solution to obtain a monomer solution.

[0059] (2) Weigh 1.85 mmol of potassium persulfate into a beaker, add 9.5 mL of deionized water, heat to 40 °C and sonicate to dissolve, then cool to room temperature to obtain an initiator solution.

[0060] (3) Add 646 μL of the initiator solution from step (2) and 0.006 mmol of N,N'-methylenebisacrylamide crosslinking agent to the solution from step (1) and mix. Sonicate at room temperature for 10 min until the mixture is homogeneous to obtain the precursor fluid.

[0061] (4) Take two 550 μL portions of the precursor fluid obtained in step (3) and drop them evenly onto the conventional anode electrode and the conventional cathode electrode without hydrogel, respectively, and place them in a vacuum defoaming tank to remove excess air bubbles to ensure uniform loading.

[0062] (5) The two electrodes obtained in step (4) are placed in a blower drying oven for thermal polymerization at a temperature of 65°C for 2 hours.

[0063] (6) The two electrode materials obtained in step (5) were washed three times in deionized water, each time for 2 hours, to remove excess monomers and initiators and other impurities. Then, the two hydrogel composite electrodes were placed in a freeze dryer and frozen at -20°C for 2 hours. Then, they were vacuum dried at 25°C and vacuum degree of -0.08 to -0.1 mPa for 1.5 hours. After that, they were soaked in 30 wt% potassium hydroxide solution for 1 hour to obtain PDMAPS hydrogel composite electrodes (referred to as hydrogel-S-NiFeLDH@NF and hydrogel-NiMoN@NF, respectively).

[0064] Example 2

[0065] A method for preparing a hydrogel composite electrode containing a polymer substrate, the specific steps of which are as follows:

[0066] (1) Weigh chitosan into a beaker and prepare 20 mL of 2wt% aqueous solution.

[0067] (2) Weigh 3.58 mmol of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide and 14 mmol of acrylamide and add them to the solution in step (1), and mix them evenly by sonication.

[0068] (3) Weigh 0.6 mmol of azobisisobutyronitrile initiator and add it to the solution obtained in step (2). Then add 0.006 mmol of N,N'-methylenebisacrylamide crosslinking agent, mix it evenly by ultrasonication, and then use a pipette to transfer 50 μL of tetramethylethylenediamine catalyst into the solution system to obtain the precursor fluid.

[0069] (4) Take two 550 μL portions of the precursor liquid from step (3) and spray them evenly onto the surface of a conventional anode electrode and a conventional cathode electrode without hydrogel, respectively, and then place them at room temperature for polymerization reaction for 24 h.

[0070] (5) The two electrode materials obtained in step (4) are washed twice in deionized water for 2 hours each time to remove excess monomers and initiators and other impurities. Then, the two hydrogel composite electrodes are placed in a freeze dryer and frozen at -40°C for 12 hours. Then, they are vacuum dried at 25°C and vacuum degree of -0.08 to -0.1 mPa for 1.5 hours. After that, they are soaked in 1M H2SO4 electrolyte for 12 hours to obtain hydrogel composite electrodes (cathode and anode).

[0071] Example 3

[0072] A method for preparing a hydrogel composite electrode without a polymer substrate, the specific steps of which are as follows:

[0073] (1) Weigh 16.8 mmol of acrylamide into a beaker, add 5.7 mL of deionized water to remove dissolved oxygen, and sonicate until the acrylamide is completely dissolved into a transparent and homogeneous liquid to obtain a monomer solution.

[0074] (2) Add 0.672 mmol of photoinitiator 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone and 0.006 mmol of N,N'-methylenebisacrylamide crosslinking agent to the solution in step (1) and mix. Sonicate at room temperature for 10 min until the mixture is homogeneous to obtain the precursor fluid.

[0075] (3) Take two portions of the precursor solution from step (2), immerse the conventional anode electrode and the conventional cathode electrode without hydrogel in the precursor solution for 5 minutes, and then irradiate them under a 365nm ultraviolet lamp for 10 minutes.

[0076] (4) The two electrodes obtained in step (3) are placed in a forced-air drying oven for thermal polymerization at a temperature of 65°C for 2 hours.

[0077] (5) The two electrode materials obtained in step (4) are washed twice in deionized water for 2 hours each time to remove excess monomers and initiators and other impurities. Then, the two hydrogel composite electrodes are placed in a freeze dryer and frozen at -30°C for 3 hours. Then, they are vacuum dried at 25°C and vacuum degree of -0.08 to -0.1 mPa for 12 hours. After that, they are soaked in 1 mol / L potassium hydroxide solution for 1 hour to obtain hydrogel composite electrodes (cathode and anode).

[0078] Effect verification

[0079] The performance of the hydrogel composite electrodes in each embodiment and comparative example was tested using an electrochemical workstation. The specific testing method was as follows: electrodes containing / without hydrogel were sequentially loaded into a steam electrolysis cell (a conventional commercial MEA membrane electrode reactor, purchased from Shanghai Chuxi Industrial Co., Ltd., structural schematic diagram shown below). Figure 6 The positions of the anode and cathode (as shown in the figure) are as follows: In the experimental group, the anode was hydrogel-S-NiFeLDH@NF and the cathode was hydrogel-NiMoN@NF; in the control group, the anode was S-NiFeLDH@NF and the cathode was NiMoN@NF. Stainless steel current collectors were used as gas transport layers on the outermost sides of the steam electrolyzer, with a 3mm gasket placed in the middle for sealing the gas. A groove in the middle of the gasket was used to place the anode and cathode catalysts. The catalysts were brought into close contact with the ion exchange membrane by external force. The effective electrolysis area was 1.5 × 1.5 square centimeters. Before the experiment, saturated steam was introduced for a period of time while simultaneously measuring the open-circuit potential of the electrolyzer. After the open-circuit potential stabilized, the chronopotential method (CP) was run. The current density for the experimental group was set to 150 mA / cm². -2The current density of the control group was set to 50 mA cm⁻¹ -2 The test results are as follows: Figure 4-5 As shown.

[0080] Figure 2 This is a plan-field achromatic micro-objective image of the hydrogel composite electrode of Embodiment 1 of the present invention. Among them, (a) is hydrogel-S-NiFeLDH@NF, and (b) is hydrogel-NiMoN@NF.

[0081] Figure 3 The images shown are scanning electron microscope (SEM) images of the hydrogel composite electrode of Example 1 of the present invention. (a) shows hydrogel-S-NiFeLDH@NF, and (b) shows hydrogel-NiMoN@NF.

[0082] Figure 4 The figures show the stability test results of the hydrogel composite electrode in the experimental group and the conventional electrode without hydrogel coating in the control group when used in a water vapor-involved electrolytic hydrogen production reaction.

[0083] Figure 5 This is a comparison chart showing the performance of the hydrogel composite electrode in the experimental group of this invention in the electrolytic hydrogen production reaction involving water vapor, and the data of water vapor electrolyzers in existing literature.

[0084] Note: Figure 5 The specific sources of references 1-9 are shown below.

[0085] Reference 1 is available at: https: / / doi.org / 10.1039 / d1ee02265b

[0086] Reference 2 is available at: https: / / doi.org / 10.1039 / c7se00373k

[0087] Reference 3 is: https: / / doi.org / 10.1021 / acssuschemeng.8b01998

[0088] Reference 4 is available at: https: / / doi.org / 10.1002 / cssc.202002281

[0089] Reference 5 is: https: / / doi.org / 10.1149 / 1945-7111 / ab9b09

[0090] Reference 6 is: https: / / doi.org / 10.1016 / j.pnucene.2007.11.029

[0091] Reference 7 is: https: / / doi.org / 10.1002 / anie.201900109

[0092] Reference 8 is located at: https: / / doi.org / 10.1093 / nsr / nwaa254

[0093] Reference 9 is located at: https: / / doi.org / 10.1039 / c5lc00259a

[0094] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. The application of a hydrogel composite electrode in electrocatalytic reactions involving water vapor, characterized in that, The preparation method of the hydrogel composite electrode includes the following steps: Monomer solutions are prepared using either method A or method B; Method A involves mixing polymer monomers in a solvent to obtain a monomer solution. Method B involves mixing the polymer monomer and the polymer substrate in a solvent to obtain a monomer solution. An initiator and a crosslinking agent are added to the monomer solution to obtain a precursor solution; The precursor liquid was loaded onto the electrode surface and polymerized to obtain the hydrogel composite electrode. The polymer monomer is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide; The polymer base is polyvinyl alcohol and / or chitosan.

2. The application according to claim 1, characterized in that, In Method B, the total concentration of the polymer monomer and polymer matrix in the precursor fluid is 0.5-3 mol / L, and the mass ratio of the polymer monomer to the polymer matrix is ​​2.5-5. In Method A, the total concentration of the polymer monomer in the precursor fluid is 0.35-2.5 mol / L.

3. The application according to claim 1, characterized in that, The initiator is potassium persulfate, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylacetone or azobisisobutyronitrile; and / or, the crosslinking agent is N,N'-methylenebisacrylamide.

4. The application according to claim 1, characterized in that, The amount of the initiator is 0.1-5% of the molar amount of the polymer monomer; and / or, the amount of the crosslinking agent is 0.1-5% of the molar amount of the polymer monomer.

5. The application according to claim 1, characterized in that, The electrode is a porous, self-supporting electrode material; and / or, the loading of the precursor fluid on the electrode is 0.5-1.2 mL / cm². 3 .

6. The application according to claim 1, characterized in that, The polymerization reaction is thermal polymerization, catalytic polymerization, or photopolymerization; the thermal polymerization temperature is 65℃ and the time is 2 h; the catalytic polymerization temperature is 20-25℃ and the time is 24 h; the photopolymerization temperature is 20-25℃, the light wavelength is 254-365nm, and the time is 10-30 min.

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