Microarrayed hydrogel electrodes and methods of making and using the same

Abstract

The application discloses a microarray hydrogel electrode and a preparation method and application thereof. The preparation method of the microarray hydrogel electrode comprises the following steps: preparing a hydrogel precursor solution, coating the hydrogel precursor solution on a microarray of a substrate, forming a hydrogel from the hydrogel precursor solution through a first treatment, and then performing first vacuum drying to obtain a shaped body; performing hydration and annealing treatment on the shaped body to obtain a hydrogel with a microarray; manufacturing the hydrogel with the microarray and a planar hydrogel into a working electrode, depositing metal platinum on the surface of the hydrogel with the microarray to obtain the microarray hydrogel electrode. The microarray hydrogel electrode has regular and ordered microarray microstructures, can effectively improve the bonding energy of bubbles and the electrode interface, can ensure the rapid mass transfer of electrons when the electrode is in contact with a solution, and makes the electrode material have an extremely high active surface area, so that the size of bubbles can be effectively controlled.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to microarrayed hydrogel electrodes, their preparation methods, and applications. Background Technology

[0002] Hydrogen energy is considered an important alternative to petroleum energy due to its high energy density and zero greenhouse gas emissions. Current hydrogen production technologies mainly include water electrolysis, fossil fuel-based hydrogen production, industrial by-product hydrogen production, and novel methods (thermochemical water splitting, solar water splitting, biomass hydrogen production, etc.). Among these, water electrolysis, with its mature technology and ability to continuously produce high-purity hydrogen, is considered one of the ideal ways to solve global energy and environmental problems.

[0003] The electrolysis of water to produce hydrogen mainly includes the hydrogen evolution reaction at the cathode (HER) and the oxygen evolution reaction at the anode (OER). The theoretical electrolysis voltage of water (E) 0 The actual operating voltage is 1.23V. However, during actual electrolysis, gaseous products cannot detach from the electrode surface in time, resulting in an actual battery operating voltage of only 1.8-2.0V. This is mainly because bubbles adhering to the electrode surface hinder the diffusion of electrolyte, thus creating a "bubble shielding" effect. This reduces the electrochemical active area, increases the ohmic drop, and ultimately reduces the reaction efficiency.

[0004] Conductive hydrogels, as a novel functional material, have attracted much attention in the field of manufacturing soft electronic devices. With the gradual development of research on conductive hydrogel materials, their increasingly refined properties, such as high stretchability, self-healing ability, transparency, and good conductivity, have gained favor in many fields. However, problems such as low mechanical strength, uneven crosslinking density distribution, and difficulty in microarraying pose higher requirements for the research and development of hydrogel materials. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem of "bubble shielding" effect easily generated on the electrode surface during the electrolysis of water to produce hydrogen in existing technologies, and to provide a microarray hydrogel electrode, its preparation method, and its application. The microarray hydrogel electrode of this invention has a regular and ordered microarray structure, which can effectively improve the binding energy between bubbles and the electrode interface. This ensures rapid electron transfer when it comes into contact with the solution, resulting in an electrode material with an extremely high active surface area, thereby effectively controlling the size of the bubbles.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a microarrayed hydrogel electrode, the method comprising the following steps:

[0007] A hydrogel precursor solution is prepared and coated onto a microarray of a substrate. The precursor solution is first treated to form a hydrogel, and then subjected to a first vacuum drying to obtain a shaped body. The shaped body is then subjected to hydration and annealing treatment to obtain a hydrogel with a microarray.

[0008] The microarray-containing hydrogel and planar hydrogel are used to fabricate working electrodes, and metallic platinum is deposited on the surface of the microarray-containing hydrogel to obtain a microarray-based hydrogel electrode.

[0009] The second aspect of the present invention provides a microarrayed hydrogel electrode prepared by the aforementioned preparation method.

[0010] A third aspect of the present invention provides the application of the aforementioned microarrayed hydrogel electrode in an electrolytic cell.

[0011] A fourth aspect of the present invention provides an electrolytic cell, wherein the electrolytic cell uses the aforementioned microarrayed hydrogel electrode as the working electrode.

[0012] The beneficial technical effects achieved by the present invention through the above technical solution are as follows:

[0013] This invention utilizes hydration and annealing treatments to reduce the bonding force between the hydrogel with microarrays and the substrate, thereby obtaining a micron-scale, regular, and complete hydrogel microarray through physical transfer; thus, a microarrayed hydrogel electrode is obtained. The microarrayed hydrogel electrode of this invention possesses a regular and ordered microarray structure, which can effectively improve the binding energy between the bubble and the electrode interface. This ensures rapid electron mass transfer when it comes into contact with the solution, resulting in an electrode material with an extremely high active surface area, thereby effectively controlling the bubble size.

[0014] This invention, through exploration and optimization of process parameters, utilizes a template method to design and fabricate micron-scale hydrogel microarrays of different materials, sizes, and morphologies. Based on this, the catalytic performance of water electrolysis using microarrayed hydrogels of different materials, sizes, and morphologies was investigated. Furthermore, the construction of microarrayed hydrogel electrodes effectively promotes gas desorption from the electrode surface, thereby enhancing the electrode's catalytic activity. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the fabrication process of a microarray hydrogel electrode according to one embodiment of the present invention;

[0016] Figure 2 It is the micron-scale pyramid-shaped conductive hydrogel obtained in Example 1 of this invention;

[0017] Figure 3 It is the micron-sized tetragonal prism-shaped conductive hydrogel obtained in Example 2 of this invention;

[0018] Figure 4 This is the micron-scale pyramid-shaped conductive hydrogel obtained in Comparative Example 1 of this invention;

[0019] Figure 5 In this context, 'a' represents the contact angle of the microarrayed hydrogel electrode obtained in Embodiment 1 of the present invention.

[0020] Figure 5 In this context, b represents the contact angle of the un-microarrayed hydrogel electrode obtained in Comparative Example 2 of this invention.

[0021] Figure 6 The bubble evolution process on the surface of the microarrayed hydrogel electrode obtained in Example 1 of this invention;

[0022] Figure 6 The bubble evolution process on the surface of the un-microarrayed hydrogel electrode obtained in Comparative Example 2 of this invention;

[0023] Figure 7 These are the HER polarization curves of the pyramid-shaped microarray hydrogel electrodes of different sizes and spacings of the present invention.

[0024] Figure 8 It is the Tafel slope of the pyramid-shaped microarray hydrogel electrodes of different sizes and spacings in this invention. Detailed Implementation

[0025] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0026] The first aspect of this invention provides a method for preparing a microarrayed hydrogel electrode, the method comprising the following steps:

[0027] A hydrogel precursor solution is prepared and coated onto a microarray of a substrate. The precursor solution is first treated to form a hydrogel, and then subjected to a first vacuum drying to obtain a shaped body. The shaped body is then subjected to hydration and annealing treatment to obtain a hydrogel with a microarray.

[0028] The microarray-containing hydrogel and planar hydrogel are used to fabricate working electrodes, and metallic platinum is deposited on the surface of the microarray-containing hydrogel to obtain a microarray-based hydrogel electrode.

[0029] Specifically, adopting such as Figure 1The process flow shown is used to prepare microarray hydrogel electrodes. The preparation process of planar hydrogel is to directly coat it on the substrate without the need for a template for the microarray. The specific preparation process is the same as that of microarray hydrogel. Then, platinum is deposited on the surface of the microarray hydrogel.

[0030] In this invention, the conductive hydrogel possesses excellent three-dimensional network porous structure, conductivity, and hydrophilicity / gas-repellent properties, making it suitable as an electrode material for electrochemical catalysis. Through in-depth research, the inventors discovered that the microarray conductive hydrogel, as a well-ordered micron-sized structure, can effectively improve the binding energy between bubbles and the electrode interface. This ensures rapid electron transfer when in contact with the solution, resulting in an electrode material with an extremely high active surface area, thereby effectively controlling the bubble size.

[0031] This invention focuses on the design and preparation of conductive hydrogels and their application in electrochemical hydrogen evolution and oxygen evolution catalytic reactions using microarray structures. This invention provides new research ideas and experimental methods for designing highly electrochemically active microarray conductive hydrogels.

[0032] This invention first reduces the bonding force between the hydrogel microarray and the substrate (e.g., silicon wafer) through hydration and annealing treatments, thereby obtaining a micron-sized, regular, and complete hydrogel microarray through physical transfer. The construction of the microarrayed hydrogel electrode can effectively promote gas desorption from the electrode surface, thereby enhancing the catalytic activity of the electrode.

[0033] In some embodiments of the present invention, the integrity of the micron-scale hydrogel microarray is greater than 90%.

[0034] In this invention, the integrity of the hydrogel microarray is calculated as follows: (Total number - Number of broken pieces) / Total number * 100%. Wherein, the total number refers to the number of all patterns in the microarray, and the number of broken pieces refers to the number of broken patterns in the microarray.

[0035] In some embodiments of the present invention, the deposition is an underpotential electrochemical deposition.

[0036] The deposition method of the present invention is a conventional deposition method. The present invention does not impose specific limitations on the deposition method, but magnetron sputtering is preferred.

[0037] In some embodiments of the present invention, the steps of hydration and annealing include: heating the molded body at 60-100°C for 4-6 hours, then cooling it to room temperature, adding water dropwise during the cooling process to complete one annealing process; repeating the annealing process until the hydrogel microarray detaches.

[0038] By repeating the hydration and annealing processes as described above several times until the hydrogel microarray detaches automatically, a regular and complete hydrogel microarray can be obtained. This invention reduces the adhesion between the hydrogel microarray and the silicon substrate through repeated hydration and annealing processes.

[0039] In some embodiments of the present invention, the first treatment step specifically includes: first performing vacuum treatment, then immersing in a saturated NaCl solution, changing the water every 4-6 hours.

[0040] The present invention can remove monomers (small molecule crosslinking agents, polyvinyl alcohol) that did not participate in the polymerization reaction and some oligomer impurities generated by the polymerization reaction through the first treatment.

[0041] In some preferred embodiments of the present invention, the vacuum treatment is performed at a temperature of 20-30°C for a duration of 4-8 hours.

[0042] In some preferred embodiments of the present invention, the soaking temperature is 15-35°C and the soaking time is 20-28 hours.

[0043] In some embodiments of the present invention, the preparation method of the hydrogel precursor liquid includes: preparing a polyvinyl alcohol hydrogel, adding a small molecule crosslinking agent solution, deionized water and a first solution to the polyvinyl alcohol hydrogel respectively to obtain a mixture; wherein, the first solution is an aniline solution or a pyrrole solution;

[0044] The mixture was mixed with ammonium persulfate solution under ice-water bath conditions, and after ultrasonic degassing, a conductive hydrogel precursor solution was obtained.

[0045] In this invention, the preparation method of the hydrogel precursor solution specifically includes the following steps:

[0046] Ammonium persulfate was ultrasonically dissolved in deionized water to prepare an ammonium persulfate solution, which was then placed in an ice-water bath at 0°C for later use.

[0047] Weigh out a specific amount of small molecule crosslinking agent and sonicate it to dissolve. Then, slowly add the prepared small molecule crosslinking solution, deionized water, and aniline solution (or pyrrole solution) dropwise to the polyvinyl alcohol hydrogel, stir until homogeneous, and place the mixture in a 0°C ice-water bath for later use.

[0048] Under 0℃ ice-water bath conditions, ammonium persulfate solution was slowly added dropwise to the mixture, and the mixture was quickly stirred until homogeneous. After removing air bubbles from the mixture by ultrasonication, a conductive hydrogel precursor solution was obtained.

[0049] In this invention, small molecule crosslinking agents include, but are not limited to, m-aminophenylboronic acid and phytic acid. These small molecule crosslinking agents can not only improve the strength of the hydrogel but also enhance its conductivity.

[0050] In some embodiments of the present invention, the method for preparing the polyvinyl alcohol hydrogel includes: mixing and swelling polyvinyl alcohol with water, then stirring and dissolving to obtain a polyvinyl alcohol solution; and then subjecting the polyvinyl alcohol solution to freeze-thaw cycles to obtain a polyvinyl alcohol hydrogel.

[0051] In some preferred embodiments of the present invention, the swelling temperature is 40-80°C, preferably 60°C, until the swelling is complete.

[0052] In some preferred embodiments of the present invention, the temperature for stirring and dissolving is 70-100°C, preferably 90°C, and the time is 1-3 hours, preferably 2 hours.

[0053] In some preferred embodiments of the present invention, the freeze-thaw cycle process includes: storing the polyvinyl alcohol solution at -10°C to -30°C for 14-18 hours, preferably at -20°C for 16 hours, taking it out, and thawing it at room temperature for 6-10 hours, preferably 8 hours, and repeating the storage and thawing process 3-5 times.

[0054] In some embodiments of the present invention, the conditions for ultrasonic degassing include: treatment at a temperature of 15-35°C and an ultrasonic temperature of 80-120W for 10-30 minutes.

[0055] In some embodiments of the present invention, the small molecule crosslinking agent is selected from m-aminophenylboronic acid or phytic acid.

[0056] In some preferred embodiments of the present invention, the volume ratio of the mixture to the ammonium persulfate solution is 1-3:1.

[0057] In some embodiments of the present invention, the temperature of the first vacuum drying is 60-80°C, preferably 70°C, and the time is 1-3 hours, preferably 2 hours.

[0058] In some embodiments of the present invention, the substrate has a micron-scale microarray.

[0059] The microarray substrate of the present invention is selected according to actual needs.

[0060] In some embodiments of the present invention, the micron-scale microarray is a pyramid-shaped microarray, a cubic microarray, a strip-shaped microarray, a prism-shaped microarray, or a cylindrical microarray.

[0061] In some preferred embodiments of the present invention, in the pyramid-shaped microarray, the base side length of each pyramid is 5-10 μm, the height is 3.5-7.5 μm, and the gap between any two adjacent pyramids is 5-50 μm, for example 5 μm, 10 μm, 20 μm, 30 μm, 40 μm or 50 μm.

[0062] In some embodiments of the present invention, the method for fabricating a substrate with a micron-scale microarray includes: fabricating a microarray in the shape of a pyramid, a square prism, a cylinder, a cuboid, etc., on a 4-inch silicon wafer using photoelectrochemical etching technology. After rough washing, the microarray silicon wafer substrate is plasma-cleaned for 10 minutes, and then ultrasonically cleaned sequentially in acetone, ethanol, and deionized water for 30 minutes each before drying for later use.

[0063] A second aspect of the present invention provides a microarrayed hydrogel electrode prepared by the aforementioned preparation method.

[0064] This invention first fabricates a hydrogel microarray on a microarray template, and then obtains a microarray with a good morphology after annealing and heat treatment. Based on this, the treated microarray hydrogel and planar hydrogel are cut into 1*2cm sizes to form working electrodes. After underpotential electrochemical deposition of metal Pt on the surface of the hydrogel using an electrochemical workstation, the microarray hydrogel electrode is obtained.

[0065] A third aspect of the present invention provides the application of the aforementioned microarrayed hydrogel electrode in an electrolytic cell.

[0066] A fourth aspect of the present invention provides an electrolytic cell, wherein the electrolytic cell uses the aforementioned microarrayed hydrogel electrode as the working electrode.

[0067] The electrolytic cell of this invention is mainly used for electrolyzing water to produce hydrogen and oxygen, and the microarray electrode is the working electrode for producing hydrogen.

[0068] The battery of this invention uses a microarrayed hydrogel electrode as the working electrode. The microarrayed conductive hydrogel, as a regular and ordered micron-structure, can effectively improve the binding energy between bubbles and the electrode interface. This ensures rapid electron transfer when the electrode comes into contact with the solution, resulting in an extremely high active surface area and effectively controlling the bubble size. Therefore, allowing gaseous products to quickly leave the electrode surface and expose more active sites is an effective strategy to enhance the water electrolysis reaction.

[0069] The present invention will be described in detail below through embodiments, but the scope of protection of the present invention is not limited to the following description.

[0070] Unless otherwise specified in the following examples and comparative examples, all conditions were performed under standard conditions or conditions recommended by the manufacturer. All reagents and instruments used were commercially available products.

[0071] Example 1

[0072] The method for fabricating a micron-scale pyramid-shaped microarray hydrogel electrode includes the following steps:

[0073] (1) Fabrication of microarray silicon wafer substrates: Pyramid-shaped microarrays with a linewidth of 5 μm, a height of 3.5 μm, and a gap of 5 μm were fabricated on 4-inch silicon wafers using photoelectrochemical etching technology. After rough cleaning, the microarray silicon wafer substrates were plasma cleaned for 10 min, and then ultrasonically cleaned for 30 min each with acetone, ethanol, and deionized water, and then dried.

[0074] (2) Preparation of conductive hydrogel precursor solution: A measured amount of PVA powder was dissolved in deionized water to prepare a PVA solution; the PVA solution was first fully swollen at 60℃, and then stirred continuously at 90℃ for 2 hours, followed by cooling to room temperature to obtain a polyvinyl alcohol solution for later use; the polyvinyl alcohol solution was stored at -20℃ for 16 hours, and then thawed at room temperature for 8 hours, completing 3-5 freeze-thaw cycles to obtain a polyvinyl alcohol hydrogel; 456.4 mg of ammonium persulfate was ultrasonically dissolved in 1 mL of deionized water to prepare solution A, and... Place the solution in a 0℃ ice-water bath for later use; weigh 18.3 mg of m-aminophenylboronic acid and add it to 835 μL of 6M HCl, sonicate to dissolve it, then slowly add the prepared m-aminophenylboronic acid solution, 225 μL of deionized water and 137.5 μL of aniline solution to 2 mL of 8% polyvinyl alcohol hydrogel, stir well to obtain solution B, and place it in a 0℃ ice-water bath for later use; under the 0℃ ice-water bath condition, slowly add solution A to solution B and stir quickly until well mixed, sonicate to remove air bubbles in the mixture to obtain the polyaniline hydrogel precursor solution.

[0075] (3) Preparation of hydrogel microarray: The hydrogel precursor solution (a mixed solution of A and B) obtained in step (2) was uniformly spread on the microarray of the silicon wafer substrate obtained in step (1) using a spin coater; the hydrogel precursor solution was allowed to stand at room temperature for 6 hours in a vacuum drying oven, and then polymerized to obtain the corresponding conductive hydrogel; after polymerization, the obtained hydrogel was soaked in a saturated NaCl solution for 24 hours, and the water was changed every 8 hours to remove monomers (small molecule crosslinking agent, polyvinyl alcohol) that did not participate in the polymerization reaction and some oligomer impurities generated by the polymerization reaction. Before demolding, the silicon wafer substrate loaded with hydrogel was placed in a vacuum drying oven at 70°C for 2 hours, and the bonding force between the hydrogel microarray and the silicon wafer substrate was reduced by continuous hydration and annealing treatment. The above method was repeated several times until the hydrogel microarray automatically detached, and a regular and complete micron-scale pyramid-shaped conductive hydrogel microarray was obtained, such as Figure 2 As shown.

[0076] (4) Cut the microarray conductive hydrogel and planar hydrogel obtained in step (3) into 1*2cm sizes to make working electrodes. Use an electrochemical workstation to perform underpotential electrochemical deposition of metal Pt on the surface of the microarray conductive hydrogel to obtain the microarray hydrogel electrode.

[0077] Example 2

[0078] The method for fabricating a micron-sized tetragonal prism-shaped polypyrrole microarray hydrogel electrode includes the following steps:

[0079] (1) Fabrication of the microarray silicon wafer substrate: A quadrangular prism-shaped microarray with a side length of 5μm, a height of 5μm, and a gap of 5μm was fabricated on a 4-inch silicon wafer using photoelectrochemical etching technology. After rough washing, the microarray silicon wafer substrate was plasma cleaned for 10 minutes, and then ultrasonically cleaned in acetone, ethanol, and deionized water for 30 minutes each before drying for later use.

[0080] (2) Preparation of conductive hydrogel precursor solution: Weigh a certain amount of PVA powder and dissolve it in deionized water to prepare a PVA solution; fully swell the PVA solution at 60℃, stir continuously at 90℃ for 2 hours, and then cool to room temperature to obtain a polyvinyl alcohol solution for later use; store the polyvinyl alcohol solution at -20℃ for 16 hours, thaw it at room temperature for 8 hours, and complete 3-5 freeze-thaw cycles to obtain polyvinyl alcohol hydrogel; weigh 184 mg of ammonium persulfate and dissolve it in 1 mL of water using ultrasonication. Solution A was prepared in deionized water and placed in an ice-water bath at 0°C for later use. Solution B was prepared by slowly adding 184 μL of phytic acid solution, 148 μL of pyrrole monomer (Py / PA molar ratio of approximately 6) and 1 mL of isopropanol mixture to 2 mL of 8 wt% polyvinyl alcohol gel. After stirring and sonicating, the mixture was placed in an ice-water bath at 0°C for later use. Under the condition of ice-water bath at 0°C, solution A was slowly added to solution B and stirred rapidly until homogeneous. After removing air bubbles from the mixture by sonication, the hydrogel precursor solution was obtained.

[0081] (3) Preparation of hydrogel microarray: The hydrogel precursor solution (a mixed solution of A and B) obtained in step (2) was uniformly spread on the microarray of the silicon wafer substrate obtained in step (1) using a spin coater; the hydrogel precursor solution was allowed to stand at room temperature for 6 hours in a vacuum drying oven, and then polymerized to obtain the corresponding conductive hydrogel. After polymerization, the obtained hydrogel was soaked in a saturated NaCl solution for 24 hours, and the water was changed every 8 hours to remove monomers (small molecule crosslinking agent, polyvinyl alcohol) that did not participate in the polymerization reaction and some oligomer impurities generated by the polymerization reaction. Before demolding, the silicon wafer substrate loaded with hydrogel was placed in a vacuum drying oven at 60°C for 2 hours, and the bonding force between the hydrogel microarray and the silicon wafer substrate was reduced by continuous hydration and annealing. The above method was repeated several times until the hydrogel microarray automatically detached, and a regular and complete micron-sized tetragonal prism-shaped conductive hydrogel microarray was obtained, such as Figure 3 As shown.

[0082] (4) Cut the microarray conductive hydrogel and planar hydrogel obtained in step (3) into 1*2cm sizes to make working electrodes. Use an electrochemical workstation to perform underpotential electrochemical deposition of metal Pt on the surface of the microarray conductive hydrogel to obtain the microarray hydrogel electrode.

[0083] Comparative Example 1

[0084] The micron-scale pyramidal microarray hydrogel electrode was prepared according to the method in Example 1, except that in step (2), the hydrogel microarray was directly peeled off without hydration and annealing treatment, resulting in the following: Figure 4 The hydrogel microarray shown is obtained by following the same steps as in Example 1 to obtain a microarrayed hydrogel electrode.

[0085] Comparative Example 2

[0086] Planar hydrogels were cut into 1*2cm pieces to form working electrodes. Underpotential electrochemical deposition of metallic Pt was performed on the surface of the planar hydrogels using an electrochemical workstation to obtain un-microarrayed hydrogel electrodes.

[0087] Test case

[0088] The water electrolysis performance of the hydrogel electrodes obtained in Examples 1-2 and Comparative Examples 1-2 was tested:

[0089] (1) HER electrochemical testing:

[0090] The electrochemical test used a three-electrode system, with the working electrode being a 1*2cm electrode. 2 The hydrogel electrodes obtained in Examples 1-2 and Comparative Examples 1-2 above used a saturated calomel electrode as the reference electrode and a carbon rod as the counter electrode. The electrolyte was a 0.5 mol / L sulfuric acid solution. The electrodes were activated using cyclic voltammetry at a potential between 0 and 1 V at a scan rate of 100 mV / s until they stabilized. Electrocatalytic activity was tested using linear scanning, scanning from 0 V to -1 V at a scan rate of 1 mV / s. The electrochemical impedance spectroscopy of the electrode material was measured using AC impedance spectroscopy at a potential set to -0.3 V, from a high frequency of 100 kHz to a low frequency of 0.1 Hz.

[0091] (2) OER electrochemical test

[0092] Electrochemical measurements were performed using a three-electrode system: a platinum electrode as the counter electrode and a saturated calomel electrode as the reference electrode. The electrolyte was a 1 mol / L KOH solution. Before testing, the electrodes were activated by scanning the cyclic voltammetry (CV) curve at a scan rate of 100 mV / s. The cyclic voltammetry and linear sweep voltammetry ranges were 1.0–2.0 V, with a scan rate of 5 mV / s. The AC impedance measurement range was 0.1–10 V. 5The frequency is Hz, and the potential is 1.23V (relative to the reversible hydrogen electrode).

[0093] The contact angle of the microarrayed hydrogel electrode obtained in Example 1 is as follows: Figure 5 As shown in a; the contact angle of the un-microarrayed hydrogel electrode obtained in Comparative Example 2 is shown in figure a. Figure 5 As shown in b; the bubble evolution process on the surface of the microarrayed hydrogel electrode obtained in Example 1 is as follows. Figure 6 As shown in the figure; the bubble evolution process on the surface of the un-microarrayed hydrogel electrode obtained in Comparative Example 2 is as follows. Figure 6 As shown in eh.

[0094] The results obtained from the microarrayed hydrogel electrodes in Examples 1-2 and Comparative Examples 1-2 show that, due to the strong adhesion between the hydrogel microarray and the silicon substrate, a regular and complete hydrogel microarray cannot be obtained by directly peeling it off without annealing. Therefore, annealing can effectively reduce the adhesion between the hydrogel and the silicon substrate, thereby resulting in a regular and complete morphology for the hydrogel microarray peeled off after annealing.

[0095] Figure 7 and Figure 8 The figures show the HER polarization curves and Tafel slopes of pyramidal microarray hydrogel electrodes with different sizes and spacings. As can be seen from the figures, smaller linewidths and gaps in the hydrogel microarrays prepared by the method of this invention are not necessarily better. Taking this embodiment as an example, when the linewidth and gap of the pyramidal microarray are 5 μm and 5 μm respectively, it exhibits the greatest catalytic activity and is more conducive to bubble separation.

[0096] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a microarrayed hydrogel electrode, characterized in that, The preparation method includes the following steps: A hydrogel precursor solution is prepared and coated onto a microarray of a substrate. The precursor solution is first treated to form a hydrogel, and then subjected to a first vacuum drying to obtain a shaped body. The shaped body is then subjected to hydration and annealing treatment to obtain a hydrogel with a microarray. The hydrogel with microarray and the planar hydrogel are used to make working electrodes, and metallic platinum is deposited on the surface of the hydrogel with microarray to obtain a microarray hydrogel electrode. The hydration and annealing process includes: heating the molded body at 60-100°C for 4-6 hours, then cooling it to room temperature, adding water dropwise during the cooling process to complete one annealing process; repeating the annealing process until the hydrogel microarray detaches. The method for preparing the hydrogel precursor solution includes: preparing a polyvinyl alcohol hydrogel by adding a small molecule crosslinking agent solution, deionized water, and a first solution to the polyvinyl alcohol hydrogel to obtain a mixture; wherein the first solution is an aniline solution or a pyrrole solution. Under ice-water bath conditions, the mixture was mixed with ammonium persulfate solution, and after ultrasonic degassing, a conductive hydrogel precursor solution was obtained. The method for preparing the polyvinyl alcohol hydrogel includes: mixing polyvinyl alcohol with water to swell, then stirring to dissolve it to obtain a polyvinyl alcohol solution; and then subjecting the polyvinyl alcohol solution to freeze-thaw cycles to obtain a polyvinyl alcohol hydrogel.

2. The preparation method according to claim 1, wherein, The deposition was an underpotential electrochemical deposition.

3. The preparation method according to claim 1 or 2, wherein, The first treatment steps specifically include: first performing vacuum treatment, then immersing in a saturated NaCl solution, changing the water every 4-6 hours.

4. The preparation method according to claim 3, wherein, The vacuum drying temperature is 20-30℃, and the time is 4-8 hours.

5. The preparation method according to claim 3, wherein, The soaking temperature is 15-35℃, and the soaking time is 20-28h.

6. The preparation method according to claim 1, wherein, The swelling temperature is 40-80℃.

7. The preparation method according to claim 1, wherein, The stirring and dissolving process takes place at a temperature of 70-100℃ for 1-3 hours.

8. The preparation method according to claim 1, wherein, The freeze-thaw cycle process includes: storing the polyvinyl alcohol solution at -10°C to -30°C for 14-18 hours, taking it out, and thawing it at room temperature for 6-10 hours; repeating the storage and thawing process 3-5 times.

9. The preparation method according to claim 1, wherein, The conditions for ultrasonic degassing include: treatment at a temperature of 15-35℃ and an ultrasonic power of 80-120W for 10-30 minutes.

10. The preparation method according to claim 1, wherein, The small molecule crosslinking agent is selected from m-aminophenylboronic acid or phytic acid.

11. The preparation method according to claim 1, wherein, The volume ratio of the mixture to the ammonium persulfate solution is 1-3:

1.

12. The preparation method according to claim 1 or 2, wherein, The temperature of the first vacuum drying is 60-80℃, and the time is 1-3 hours.

13. The preparation method according to claim 1 or 2, wherein, The microarray substrate has a micron-scale microarray.

14. The preparation method according to claim 13, wherein, The micron-scale microarray can be a pyramid-shaped microarray, a cube-shaped microarray, a strip-shaped microarray, a prism-shaped microarray, or a cylindrical microarray.

15. The preparation method according to claim 13, wherein, In the pyramid-shaped microarray, the base of each pyramid has a side length of 5-10 μm and a height of 3.5-7.5 μm, and the gap between any two adjacent pyramids is 5-50 μm.

16. The microarrayed hydrogel electrode prepared by the preparation method according to any one of claims 1-15.

17. The application of the microarrayed hydrogel electrode of claim 16 in an electrolytic cell.

18. An electrolytic cell, characterized in that, The electrolytic cell uses the microarrayed hydrogel electrode as described in claim 16 as the working electrode.

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