Hydrogen evolution electrode for alkaline electrolyzed water

Abstract

The hydrogen evolution electrode comprises a nickel net substrate, a transition layer located on the surface of the nickel net substrate and a porous catalyst layer located on the surface of the transition layer, and the contact face of the transition layer and the porous catalyst layer is of a micropore structure. Wherein the average thickness of the transition layer is 5-15 microns; and the average thickness of the porous catalyst layer is 0.1-10 [mu] m. The porous catalyst layer at the outermost layer can provide enough active sites for hydrogen evolution reaction, and the transition layer positioned between the nickel net substrate and the porous catalyst layer can reduce stress between metal materials, so that the combination effect of active substances and the nickel net substrate is improved, and the hydrogen evolution reaction efficiency is improved. And the pore structure gradually enlarged from the inner transition layer to the outer catalyst layer is beneficial to removal of hydrogen bubbles generated in the electrolysis process. The hydrogen evolution electrode with the designed structure has very high electrochemical hydrogen evolution performance, the structural stability of the electrode can still be kept after the electrode works for a long time, and the service life of the electrode is effectively prolonged.

Description

Technical Field

[0001] The utility model relates to a hydrogen evolution electrode, in particular to a hydrogen evolution electrode used for alkaline water electrolysis. Background Art

[0002] Hydrogen production by water electrolysis is a method of producing hydrogen through an electrochemical process. During the electrolysis process, hydrogen and oxygen are precipitated at the cathode and anode ends of the electrolyzer, respectively. Alkaline water electrolysis hydrogen production technology is currently the most mature, most successfully industrialized, lowest cost, and highest market share technology route. It uses strong alkaline aqueous solutions such as NaOH and KOH, asbestos, non-woven fabrics or other high molecular polymers as diaphragms, and produces hydrogen under the action of direct current. In theory, the voltage required for electrolysis of water in an electrolyzer is 1.23V. However, in actual situations, the required electrolysis voltage is much higher than 1.23V, and the voltage that exceeds the theoretical value is called overpotential. The overpotential is mainly caused by the following reasons: 1. Circuit resistance inside and outside the electrolyzer, 2. Electrochemical polarization, 3. Resistance caused by the anode and cathode separator in the electrolyzer, 4. Electrochemical polarization, 5. Bubble resistance, 6. Resistance generated by the catalyst layer.

[0003] The study found that for the cathode, which is the bottleneck of the electrolysis of water under alkaline conditions, the ability to produce hydrogen by electrolysis of water can be improved by increasing the intrinsic activity or specific surface area of ​​its catalyst, that is, reducing the overpotential during electrolysis. In the former, precious metals such as platinum, palladium, ruthenium and their alloys are used as catalysts for the cathode hydrogen evolution reaction, which can reduce the overpotential of the reaction, improve the efficiency of hydrogen evolution while reducing power consumption, but the high cost makes it difficult to apply on a large scale. In the latter, at present, the industry mostly uses thermal spraying of nickel, aluminum and its transition metal alloys onto nickel mesh, and then washes off the amphoteric metal aluminum therein to form a porous structure to increase its specific surface area as a hydrogen evolution electrode, thereby improving the electrochemical performance of the cathode side during the electrolysis of water. However, the hydrogen evolution electrode directly obtained by thermal spraying has poor adhesion between the surface active substance and the electrode, and its surface active substance will fall off and inactivate after working for a long time in the electrolytic cell. In addition, there are also reports on the preparation of hydrogen evolution electrodes by chemical deposition, coating thermal decomposition, organic template method and other methods, but not only is the production cost high, but the life of the obtained electrode is also poor. Summary of the invention

[0004] Purpose of the invention: The utility model aims to provide a hydrogen evolution electrode for alkaline water electrolysis which has excellent hydrogen evolution performance, good structural stability and can effectively prolong the service life of the electrode.

[0005] Technical solution: The hydrogen evolution electrode for alkaline water electrolysis described in the utility model comprises a nickel mesh substrate, a transition layer located on the surface of the nickel mesh substrate and a porous catalytic layer located on the surface of the transition layer, wherein the contact surface between the transition layer and the porous catalytic layer is a microporous structure.

[0006] Furthermore, the average pore size of the microporous structure is smaller than the average pore size of the porous catalytic layer, wherein the microporous structure is irregular holes with an average pore size of 0.1-2 μm, and the average pore size of the porous catalytic layer is 2-50 μm.

[0007] Furthermore, the average thickness of the transition layer is 5-15 μm; the average thickness of the porous catalytic layer is 0.1-10 μm.

[0008] Furthermore, the nickel mesh is a plain or twill nickel mesh with a mesh size of 40-60 and a wire diameter of 50-500 μm.

[0009] Furthermore, the transition layer is a binary alloy layer composed of nickel and amphoteric metal; the amphoteric metal is aluminum or zinc; and the mass ratio of the nickel to the amphoteric metal is 50-95:5-50.

[0010] Furthermore, the porous catalytic layer is an alloy coating formed of nickel and zinc.

[0011] Furthermore, the alloy coating also includes a transition metal; the transition element is one of cobalt, iron, copper, manganese, molybdenum or silver; the mass ratio of nickel, zinc and transition metal is 20-60:20-80:0-40.

[0012] In the utility model, the hydrogen evolution electrode includes transition layers with different nickel contents and a porous catalytic layer from the inside to the outside. The uniform pore structure can increase the specific surface area, thereby increasing the active sites of the hydrogen evolution reaction.

[0013] Beneficial effects: Compared with the prior art, the utility model has the following advantages: the contact surface between the transition layer and the porous catalytic layer of the utility model can not only effectively improve the bonding effect between the porous catalytic layer and the nickel mesh, so that the electrode can still maintain its structural stability after long-term work, but also the pore structure gradually increasing from the inner transition layer to the outer catalytic layer is conducive to the escape of hydrogen bubbles generated during electrolysis, and the outermost porous catalytic layer can provide sufficient active sites for the hydrogen evolution reaction, which significantly improves the performance of the existing alkaline water electrolysis hydrogen evolution electrode and effectively prolongs the service life of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the cross section of the hydrogen evolution electrode in Example 1 of the utility model, wherein 1 is a nickel mesh substrate; 2 is a transition layer; 3 is a porous catalytic layer; 4 is a microporous structure;

[0015] Figure 2 This is a SEM image of the nickel-zinc alloy transition layer (NiZn) in Example 1 of the present utility model;

[0016] Figure 3This is a SEM image of the porous nickel-cobalt-zinc hydrogen evolution electrode (NiCoZn / NiZn) in Example 1 of the utility model;

[0017] Figure 4 This is a SEM image of the nickel-aluminum alloy transition layer (NiAl) in Example 2 of the present utility model;

[0018] Figure 5 This is a SEM image of the porous nickel-cobalt-zinc hydrogen evolution electrode (NiZn / NiAl) in Example 2 of the utility model;

[0019] Figure 6 The voltage test diagrams of Examples 1 to 2 and Comparative Example 1 of the present utility model are shown below;

[0020] Figure 7 This is a SEM image of the hydrogen evolution electrode described in Example 1 of the utility model after a 96-hour durability test;

[0021] Figure 8 This is a SEM image of the hydrogen evolution electrode described in Comparative Example 1 of the utility model after a 96-hour durability test;

[0022] Fig. 9 This is a SEM image of the transition layer after a portion of the catalytic layer of the hydrogen evolution electrode described in Example 1 of the utility model is detached by repeated bending;

[0023] Fig.10 for Fig. 9 A partial enlarged view of . DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0025] Example 1: Figure 1 As shown, the hydrogen evolution electrode for alkaline water electrolysis provided by the utility model comprises a nickel mesh substrate 1, a transition layer 2 located on the surface of the nickel mesh substrate and a porous catalytic layer 3 located on the surface of the transition layer, wherein the contact surface between the transition layer 2 and the porous catalytic layer 3 is a microporous structure 4; wherein the microporous structure 4 is an irregular hole, the average pore size of the hole is 0.7 μm, and the average pore size of the porous catalytic layer is 4.8 μm; the average thickness of the transition layer is 4.2 μm; the average thickness of the porous catalytic layer is 9.1 μm; and the nickel mesh is a twill nickel mesh with a mesh size of 50 and a wire diameter of 300 μm.

[0026] The transition layer 2 is an alloy having 70% nickel and 30% zinc formed by electroplating process, as shown in the SEM image. Figure 2 As shown, the surface is relatively rough, which can provide sufficient sites for further electroplating of the catalytic layer.

[0027] The porous catalytic layer 3 is a ternary alloy coating containing 40% nickel, 40% zinc and 20% cobalt formed on the surface of the over-plating layer 2. The alloy structure is improved by heat treatment under an inert gas, and the amphoteric metal zinc in the ternary alloy is removed by alkali washing. The SEM image of its surface morphology is shown in FIG. Figure 3 As shown, it can be seen that due to the dissolution of the amphoteric metal zinc in the alkali solution, the remaining nickel-cobalt alloy becomes a uniform porous structure, effectively increasing its surface area.

[0028] Embodiment 2: The hydrogen evolution electrode for alkaline water electrolysis provided by the utility model comprises a nickel mesh substrate 1, a transition layer 2 located on the surface of the nickel mesh substrate and a porous catalytic layer 3 located on the surface of the transition layer, wherein the contact surface between the transition layer 2 and the porous catalytic layer 3 is a microporous structure 4; wherein the average pore size of the microporous structure is 1.6 μm, and the average pore size of the porous catalytic layer is 2.3 μm; the average thickness of the transition layer is 12.6 μm; the average thickness of the porous catalytic layer is 5.5 μm; the nickel mesh is a plain nickel mesh with a mesh size of 400 μm and a wire diameter of 400 μm.

[0029] The transition layer 2 is an alloy having 60% nickel and 40% aluminum formed by a thermal spraying process, as shown in the SEM image. Figure 4 As shown, its surface is relatively rough, which can provide sufficient sites for further electroplating of the catalytic layer.

[0030] The porous catalytic layer 3 is a binary alloy coating containing 60% nickel and 40% zinc formed on the surface of the over-plating layer 2, which is obtained by improving its alloy structure through heat treatment under inert gas and finally removing the amphoteric metal zinc in the binary alloy by alkali washing. The SEM image of its surface morphology is shown in FIG. Figure 5 As shown, due to the dissolution of the amphoteric metal zinc in the alkali solution, the remaining nickel becomes a porous structure, effectively increasing its surface area.

[0031] Comparative Example 1: Compared with Example 1, there is no microporous structure 4 on the contact surface between the transition layer 2 and the porous catalytic layer 3.

[0032] Figure 6 The three electrodes of Example 1 (NiCoZn / NiZn), Comparative Example 1 (NiCoZn), and Example 2 (NiZn / NiAl) were placed in a 30% sodium hydroxide solution at 80°C at 300 mA / cm 2 , the voltage change of the 96-hour endurance test shows that the NiCoZn / NiZn electrode has the best electrochemical performance, and the morphology remains basically stable after the 96-hour endurance test. Figure 7As shown in the figure, the electrode of Example 1 did not crack or fall off. The performance of NiZn / NiAl is slightly worse because the catalytic effect of the porous binary alloy NiZn on its surface is not as good as that of the ternary alloy NiCoZn. The performance of the NiCoZn electrode without a transition layer dropped significantly after about 50 hours. Figure 8 It can be seen from the SEM characterization results that after 96h durability test, the electrode surface active material of Comparative Example 1 showed obvious cracks and the morphology changed significantly.

[0033] Fig. 9 This is a SEM image of the transition layer after the hydrogen evolution electrode in Example 1 was repeatedly bent to remove part of the catalytic layer. Fig.10 for Fig. 9 A local enlarged view shows that the morphology of the transition layer has undergone a certain change after the electrode is prepared. The lamellar NiZn alloy on its surface has become a relatively uniform porous structure after heat treatment and alkaline washing. However, since there are fewer amphoteric metals in it and the surface is covered by the catalytic layer during alkaline washing, its pore size is smaller than that of the porous catalytic layer on the outermost layer of the electrode.

Claims

1. A hydrogen evolution electrode for alkaline water electrolysis, characterized in that: It comprises a nickel mesh substrate, a transition layer located on the surface of the nickel mesh substrate and a porous catalytic layer located on the surface of the transition layer, wherein the contact surface between the transition layer and the porous catalytic layer is a microporous structure.

2. The hydrogen evolution electrode according to claim 1, characterized in that The average pore size of the microporous structure is smaller than the average pore size of the porous catalytic layer.

3. The hydrogen evolution electrode according to claim 2, characterized in that The microporous structure is irregular holes, and the average pore size of the holes is 0.1-2 μm.

4. The hydrogen evolution electrode according to claim 2, characterized in that The average pore size of the porous catalytic layer is 2-50 μm.

5. The hydrogen evolution electrode according to claim 1, characterized in that The average thickness of the transition layer is 5-15 μm.

6. The hydrogen evolution electrode according to claim 1, characterized in that The average thickness of the porous catalytic layer is 0.1-10 μm.

7. The hydrogen evolution electrode according to claim 1, characterized in that The nickel mesh is a plain or twill nickel mesh with 40-60 meshes and a wire diameter of 50-500 μm.

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