Construction method of foamed nickel hydrogen evolution electrode with aerophilic gradient hole array structure

Abstract

The invention discloses a construction method of a foamed nickel hydrogen evolution electrode with an aerophilic gradient hole array structure. The process of the foamed nickel hydrogen evolution electrode with the aerophilic gradient hole array structure comprises the following steps: 1, electrode pretreatment: firstly, constructing 4 * 4 equidistant gradient holes in the surface of foamed nickel, and then ultrasonically cleaning a foamed nickel electrode substrate by using absolute ethyl alcohol, hydrochloric acid and deionized water in sequence; 2, preparation of a hydrophobic coating solution: firstly taking a proper amount of n-hexane, putting the n-hexane into a beaker, then adding polydimethylsiloxane (PDMS) and a silicone rubber curing agent in proportion, then carrying out ultrasonic oscillation treatment until the solution is fully mixed, then adding hydrophobic gas-phase nano SiO2 particles into the mixed solution, and then carrying out ultrasonic oscillation until the hydrophobic gas-phase nano SiO2 particles are uniformly dispersed; 3, uniformly spraying the dispersed hydrophobic coating slurry into gradient holes of the foamed nickel; and 4, manufacturing a hydrogen evolution electrode by using the foamed nickel subjected to electrodeposition aerophile treatment of a two-electrode system.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical hydrogen evolution, and in particular to a process for preparing a nickel-based hydrogen evolution electrode for improving hydrogen evolution reaction efficiency. Background Art

[0002] In the process of global energy structure transformation to clean energy, water electrolysis hydrogen production technology has become one of the important ways to obtain hydrogen energy due to its advantages such as green environmental protection and strong sustainability. As a key step in the production of hydrogen by water electrolysis, the hydrogen evolution reaction, its reaction efficiency directly determines the cost and output of hydrogen production. At present, there are many problems that limit the improvement of hydrogen evolution efficiency in traditional hydrogen evolution electrodes. On the one hand, the low catalytic activity of the electrode requires a higher overpotential for the hydrogen evolution reaction, which undoubtedly increases the energy consumption in the hydrogen production process; on the other hand, during the hydrogen evolution process, the bubbles generated are easy to adhere to the electrode surface, hindering the full contact between the electrolyte and the electrode, covering the active sites of the electrode, thereby causing the hydrogen evolution reaction rate to decrease.

[0003] Nickel foam has attracted extensive attention in the field of hydrogen evolution electrode materials due to its unique three-dimensional porous structure, good conductivity and large specific surface area. However, the problem of bubble desorption is still significant in the hydrogen evolution process of nickel foam without special treatment. A large number of small bubbles gather on the electrode surface and are difficult to be discharged quickly, which seriously affects the continuous progress of the hydrogen evolution reaction. Therefore, it is urgent to develop a preparation method that can effectively solve the bubble desorption problem and improve the hydrogen evolution efficiency of nickel foam.

[0004] Technical solution:

[0005] 1. First, a gradient hole array structure with 4×4 equal spacing is constructed on the surface of nickel foam. Different from the traditional aperture, the design of gradient holes makes the pore size show a certain regular change. This gradient change helps to form a more reasonable material transmission channel for Laplace force, promote the diffusion of electrolyte and the discharge of bubbles. After the gradient hole array is constructed, the nickel foam electrode substrate is ultrasonically cleaned with anhydrous ethanol, hydrochloric acid, and deionized water in turn. Hydrochloric acid cleaning can remove metal oxides and impurities on the surface of nickel foam and restore its metal activity; anhydrous ethanol is used to remove organic matter such as oil; deionized water is used to wash away the residual cleaning solution. After cleaning, put it in a vacuum drying oven to dry to prevent impurities such as moisture from affecting subsequent experiments.

[0006] 2. Add an appropriate amount of n-hexane as a solvent to the beaker to provide a good carrier environment for the uniform dispersion of subsequent substances. Add polydimethylsiloxane (PDMS) and silicone rubber curing agent in precise proportions. PDMS has excellent hydrophobicity and flexibility, and can form a stable hydrophobic coating structure on the electrode surface; silicone rubber curing agent can cure PDMS. Through ultrasonic vibration, the two are fully mixed. Then, add hydrophobic gas-phase nano-SiO 2The nano-size effect of the particles can not only enhance the hydrophobicity of the coating, but also increase the contact area and adhesion between the coating and the nickel foam surface. Ultrasonic oscillation is performed again until the particles are evenly dispersed in the mixed solution to form a stable hydrophobic coating solution.

[0007] 3. Spray the dispersed hydrophobic coating slurry evenly inside the gradient hole array of nickel foam. The hydrophobic coating evenly covers the walls of the gradient holes, forming a hydrophobic and air-friendly area on the surface of the gradient holes, which can effectively guide the bubbles in the nickel foam pores into the gradient channels and improve the bubble transmission performance.

[0008] 4. A two-electrode system is used for electrodeposition. The working electrode is a nickel foam electrode substrate treated with a hydrophobic coating, and the counter electrode is graphite. The electrodeposition solution is prepared by sequentially adding cobalt sulfate heptahydrate, dilute nitric acid, sodium hypophosphite monohydrate, ammonium sulfate, and nickel chloride hexahydrate into deionized water and dissolving them fully through ultrasonic vibration. During the electrodeposition process, metal salts such as cobalt sulfate heptahydrate and nickel chloride hexahydrate will deposit on the electrode surface to form a catalytically active metal layer, accelerating the hydrogen evolution reaction. Dilute nitric acid is used to adjust the pH of the electrodeposition solution, affecting the deposition behavior and speed of metal ions, and thus optimizing the structure of the deposited layer. Sodium hypophosphite monohydrate and ammonium sulfate participate in the reaction, which helps to improve the microstructure and performance of the electrodeposited layer and enhance the catalytic activity and stability of the electrode.

[0009] Synergistic advantages - the mechanism of action of gradient pores and aerophilic coatings:

[0010] In the present invention, there is a synergistic effect between the ordered gradient pores and the aerophilic coating. During the hydrogen evolution reaction, the gradient pores are conducive to guiding the transmission of bubbles. Bubbles nucleate and grow in the smaller pores of the nickel foam, and the generated bubbles are guided to the constructed gradient pores to gather into large bubbles. The large bubbles are quickly transmitted in the gradient pores with aerophilic properties to produce a piston effect, and the smaller bubbles are guided to the gradient pores due to the piston effect to circulate back and forth. This synergistic effect greatly improves the discharge efficiency of the bubbles, reduces the residence time of the bubbles on the electrode surface, reduces the coverage of the bubbles on the active sites, and enables the electrolyte to contact the electrode more fully, thereby significantly improving the efficiency of the hydrogen evolution reaction.

[0011] Beneficial effects:

[0012] Compared with the prior art, the present invention has significant advantages. The construction of ordered gradient pores optimizes the material transmission path and enhances the bubble discharge capability; the hydrophobic and aerophilic coating improves the bubble transmission performance, and the synergistic effect of the two improves the hydrogen evolution efficiency of the electrode. The catalytic layer formed by electrodeposition further enhances the catalytic activity of the electrode. Therefore, the hydrogen evolution electrode prepared by the present invention has a low overpotential, a high hydrogen evolution current density and good stability, and has broad application prospects and important scientific value in the field of hydrogen production by water electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the working principle of nickel foam hydrogen evolution electrode with a gas-philic gradient pore array structure in an alkaline environment.

[0014] Figure 2 HER polarization curve of the gradient pore hydrophobic gas-philic hydrogen evolution electrode compared with the ordinary hydrogen evolution electrode. Figure 3 Polarization curve of the gradient pore hydrophobic gas-philic hydrogen evolution electrode after continuous operation for 25 hours at industrial current density.

[0015] There are implementation methods

[0016] The present invention is further described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto.

[0017] Implementation Case 1

[0018] A nickel foam hydrogen evolution electrode with an aerophilic gradient pore array structure was constructed using this method.

[0019] Step 1: Select a 1cm long and 1cm wide nickel foam, and use a special pore-making device to construct 4×4 equally spaced gradient holes on its surface. The hole spacing is set to 2mm, and the pore diameter gradually increases from 0.3mm to 0.7mm along the length of the nickel foam. Immerse the nickel foam with holes in a 1mol / L hydrochloric acid solution for ultrasonic vibration for 10 minutes, then ultrasonically clean it with anhydrous ethanol and deionized water for 10 minutes in turn, put it into a vacuum drying oven after cleaning, and dry it at 50°C for 1 hour.

[0020] Step 2: Add 44 mL of n-hexane, 4 g of polydimethylsiloxane (PDMS) and 0.4 g of silicone rubber curing agent to a 100 mL beaker, and mix thoroughly by ultrasonic oscillation for 30 minutes. Then add 1.6 g of hydrophobic gas-phase nano-SiO 2 The particles were ultrasonically shaken for 60 minutes until they were uniformly dispersed.

[0021] Step 3: Evenly apply the dispersed coating slurry to the inner wall of the gradient hole of the nickel foam, and dry it in a vacuum drying oven for 1 hour to initially solidify the coating.

[0022] Step 4: Prepare the electrodeposition solution, add 5.6g of cobalt sulfate heptahydrate, 3mL of dilute nitric acid, 10.6g of sodium hypophosphite monohydrate, 16g of ammonium sulfate, and 4.75g of nickel chloride hexahydrate into 200mL of deionized water in sequence, and ultrasonically vibrate until completely dissolved. Use a two-electrode system for electrodeposition, with the working electrode being nickel foam treated with a hydrophobic coating and the counter electrode being a graphite rod. At a current density of 1.5mA / cm 2 The electrodeposition was carried out for 400 seconds under the conditions of .

[0023] The performance was tested using an electrochemical workstation, with the electrode prepared by the present invention as the working electrode, the Hg / HgO electrode as the reference electrode, and the graphite rod as the counter electrode. All potentials were converted to relative to the reversible hydrogen electrode. Linear sweep voltammetry test, the voltage sweep range was 0.0 to -1.6V, and the sweep rate was 5mV / s; before the test, nitrogen was passed into the reactor until saturated, and cyclic voltammetry was swept to clean the electrode surface. Nitrogen was not stopped during the test. The test results showed that when the hydrogen evolution current density reached 10mA / cm -2 When the hydrogen evolution overpotential is 25mV, when the hydrogen evolution current density reaches 500mA / cm -2 (industrial current density range), when the hydrogen evolution overpotential is 500 mV, it is found from the bubble discharge that the bubbles can quickly rise and be discharged along the gradient pores, and the air pump effect is obvious, which effectively proves that the electrode of the present invention has strong bubble desorption ability and excellent mass transfer ability.

[0024] Implementation Case 2

[0025] The electrode preparation steps are the same as those in Example 1. In this example, the goal is to measure the stability of a hydrogen evolution electrode with ordered gas-philic gradient channels prepared by using nickel foam as an electrode substrate at an industrial current density.

[0026] The performance was tested using an electrochemical workstation, and the stability test was performed using a constant current method, with the test lasting 25 hours at an industrial current of -0.5A. The test environment and working conditions were the same as those in Example 1, and the test results showed that the potential fluctuation was minimal during the 25-hour stability test. In the process of observing the bubble discharge, the obvious gradient channel guiding the bubble discharge and the air pump effect were also seen, which further verified the effectiveness of the preparation method of the present invention and the excellent performance of the prepared hydrogen evolution electrode in bubble desorption.

[0027] Based on the implementation cases 1 and 2, it can be concluded that the method for constructing a hydrogen evolution electrode with an aerophilic gradient pore array structure of nickel foam proposed in the present invention has good repeatability and stability. The prepared hydrogen evolution electrode performs well in the hydrogen evolution reaction and is expected to be applied in the actual water electrolysis hydrogen production industry to promote the development of clean energy.

Claims

1. A method for constructing a nickel foam hydrogen evolution electrode having an aerophilic gradient pore array structure, comprising the following steps:

1. Electrode pretreatment: First, construct gradient holes with equal spacing in a 4×4 array on the surface of the nickel foam, then use anhydrous ethanol, hydrochloric acid, and deionized water to ultrasonically clean the nickel foam electrode substrate in turn, and then put it into a vacuum drying oven for drying; 2. Preparation of hydrophobic coating solution: Take an appropriate amount of n-hexane and place it in a beaker, add polydimethylsiloxane (PDMS) and silicone rubber curing agent in proportion, ultrasonically vibrate to mix them thoroughly, then add hydrophobic gas-phase nano-SiO2 particles and ultrasonically vibrate until they are evenly dispersed; 3. Coating: Spray the dispersed coating slurry evenly on the walls of the small holes of the nickel foam; 4. Electrodeposition: Electrodeposition is performed using a two-electrode system. The working electrode is an electrode substrate treated with a hydrophobic coating, the counter electrode is graphite, and the electrodeposition solution is prepared by sequentially adding cobalt sulfate heptahydrate, dilute nitric acid, sodium hypophosphite monohydrate, ammonium sulfate, and nickel chloride hexahydrate into deionized water and dissolving them by ultrasonic vibration.

2. The method for preparing a hydrogen evolution electrode constructed with ordered gas-philic gradient channels of nickel foam according to claim 1, characterized in that: The 4×4 equally spaced gradient holes have a hole spacing of 2 mm, and the hole diameter changes in a gradient within a range of 0.3-0.7 mm along a specific direction.

3. The method for constructing a nickel foam hydrogen evolution electrode having an aerophilic gradient pore array structure according to claim 1, characterized in that: The ratio of the silicone rubber curing agent to n-hexane is 10:1, and the ratio of the hydrophobic gas-phase nano-SiO2 particles to the n-hexane solution is 30:

1.

4. The method for constructing a nickel foam hydrogen evolution electrode having an aerophilic gradient pore array structure according to claim 1, characterized in that: The current density of electrodeposition is -1.5A / cm 2 , the electrodeposition time is 400s.

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