A self-supporting oxygen evolution electrode and its preparation method and application

Abstract

The present invention discloses a self-supporting oxygen evolution electrode and its preparation method and application, which belongs to the field of alkaline water electrolysis hydrogen production; the electrode is obtained by combining a hydrothermal method and an electrodeposition method; the electrode grows manganese-doped basic cobalt carbonate nanowires vertically on the surface of nickel foam, and the nanowires are surrounded by multiple layered nickel-iron double metal hydroxide nanosheets to form a nanorod as a whole. The nanorods are uniform in size, 2 to 3 μm long, and 100 to 500 nm in diameter, growing vertically on the surface of nickel foam; the electrode has high catalytic activity and stability. After using nickel foam as a conductive substrate, it can still operate stably for a long time under a high electrolysis current and in a strong alkaline medium; the electrode is used to catalyze the oxygen evolution reaction of water electrolysis to produce hydrogen under alkaline conditions; the present invention can be applied to renewable fuel cells, photoelectrocatalysis, alkaline anion exchange membrane water electrolysis (AEMWE) and electrolysis hydrogen generator devices.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of a self-supporting "branch-leaf" composite array structure - nickel-iron double hydroxide nanosheets coated with manganese-doped basic cobalt carbonate nanowire oxygen evolution electrode, belonging to the field of alkaline water electrolysis hydrogen production. Background Art

[0002] Hydrogen production by water electrolysis has the advantages of high catalytic efficiency, high purity of hydrogen production, and environmental friendliness, and is considered one of the most promising hydrogen production technologies. Hydrogen production by alkaline water electrolysis has attracted widespread attention because it can use low-cost non-precious metal electrocatalysts to replace precious metals Ir and Ru, although its energy conversion efficiency (≈70%) needs further improvement. However, the large-scale application of water electrolysis is mainly hindered by the slow oxygen evolution reaction at the anode. Therefore, it is necessary to design and explore oxygen evolution electrodes with high catalytic activity and long life.

[0003] The core of the electrolysis process is the electrocatalyst required for the electrochemical reaction, which directly affects the electrolysis efficiency, electrolysis energy consumption, electrolysis cost, and electrolytic cell life. Recently, there has been a growing trend of research on non-precious metal oxygen evolution catalysts for use under alkaline conditions.

[0004] Patent CN106149025A describes a one-step electrosynthesis method for nickel-iron hydrotalcite nanosheets. Although the method is simple to prepare, there is no relevant data showing that the electrode prepared by this method can obtain excellent oxygen evolution performance, and the micromorphology of the electrode prepared by this method is difficult to control. Patent CN105618060A describes a non-metallic bifunctional oxygen catalyst of graphene / nickel-iron hydrotalcite. In actual application, the catalyst particles are difficult to arrange in order, so it is difficult to obtain a high dispersion, and the utilization rate of the catalyst is not high. Patent CN109837558A describes a hydroxyl iron-nickel-iron hydrotalcite oxygen evolution electrode combined with a hydrothermal method and an electrodeposition method, but the electrode prepared by this method only has a low current density (10mAcm -2 ) and the running time is short.

[0005] Numerous current research results show that self-supporting electrodes without any binder or resin have stronger applicability in alkaline media than traditional binary or even ternary transition metal oxides. Using nickel foam as a conductive substrate can achieve high electrolysis current (300-1000 mA cm -2 ), it can operate stably in strong alkaline media for a long time and is one of the most promising oxygen evolution electrodes.

[0006] At present, some literature reports that the doping of Co and Mn can reduce the energy barrier of the catalyst in the electrocatalytic process, thereby improving the oxygen evolution activity. The literature Nature Catalysis, 2022, 5, 109-118, reported a method of introducing Mn into Co3O4 to form Co2MnO4 catalyst for acidic water electrolysis hydrogen production and oxygen evolution electrode, and the stability is 60 times that of Co3O4, but the result was tested in acidic electrolysis water; the literature Chemical Engineering Journal, 2022, 433, 134446, reported a Mn-doped inverse spinel oxide (Mn 0.5 Co 0.5 Fe2O4) oxygen evolution catalyst was tested under alkaline conditions at a current density of 10 mA cm -2 , overpotential 308mV. This is because the method obtains a powder catalyst, and the binder used in the test process blocks some active sites, making the oxygen evolution performance relatively low. Summary of the Invention

[0007] Based on the above background technology, the present application adopts a hydrothermal reaction to assist the electrodeposition reaction, and obtains a highly dispersed and highly stable nickel-iron double hydroxide-coated manganese-doped basic cobalt carbonate nanowire array self-supporting oxygen evolution electrode through steps such as washing and vacuum drying. The prepared self-supporting oxygen evolution electrode can enable the electrolysis of water reaction to be carried out efficiently under a small external bias voltage. Compared with the preparation method of traditional catalysts, the hydrothermal method and the electrodeposition method have the advantages of simple process, low cost, and easy industrial production. They can effectively control the morphology of the synthesized catalyst under relatively mild conditions, and have good catalytic activity and stability.

[0008] The present invention provides an electrode comprising: a nickel foam substrate and a catalytically active component; the catalytically active component is a nanorod structure vertically grown on the surface of the nickel foam substrate; the nanorod structure comprises a linear manganese-doped basic cobalt carbonate located inside, and multiple layers of nickel-iron double hydroxide wrapped around the surface of the linear manganese-doped basic cobalt carbonate; the nanorods are uniform in size, with a length of 2 to 3 μm and a diameter of 100 to 500 nm; the multiple layers of nickel-iron double hydroxide are similar to petals, wrapped around the surface of the linear manganese-doped basic cobalt carbonate, forming a flower shape.

[0009] The thickness of the nickel foam substrate is 1 mm, and the nickel content is greater than 99.9 wt %. The weight ratio of the nickel-iron double hydroxide nanosheets and the manganese-doped basic cobalt carbonate nanowires in the electrode is 1±0.005:4±0.005.

[0010] Furthermore, in the above technical solution, the nickel content in the nickel-iron double hydroxide is 5-10 wt%; the manganese content in the manganese-doped basic cobalt carbonate nanowires is 3-5 wt%.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a self-supporting oxygen evolution electrode is synthesized under relatively mild conditions by a hydrothermal reaction-assisted electrodeposition reaction to form a multi-layered nickel-iron double hydroxide-coated manganese-doped basic cobalt carbonate nanowire array based on a nickel foam substrate; the catalytically active component loading per unit area on the nickel foam substrate is 0.012-0.015 g cm -2 .

[0012] Furthermore, in the above technical solution, the obtained manganese-doped basic carbonate structured cobalt nanowires are loaded on the oxygen evolution electrode of the foam substrate, wherein the nanowires are 2 to 3 μm long and 50 to 200 nm in diameter, and are vertically grown in a nanowire array on the nickel foam.

[0013] Furthermore, in the above technical solution, the catalytic layer of the self-supporting multi-layered nickel-iron double hydroxide-coated manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode obtained by the combination of hydrothermal method and electrodeposition method has the final morphology characteristics of nanorods with a length of 2 to 3 μm and a diameter of 100 to 500 nm.

[0014] Furthermore, in the above technical solution, the preparation method includes the following steps:

[0015] Step (1) hydrothermal reaction: dissolving a cobalt salt precursor, a manganese salt precursor, a base and a ligand I, stirring to obtain a hydrothermal precursor solution, subjecting the hydrothermal precursor solution to a hydrothermal reaction with nickel foam, and washing and drying the obtained nickel foam after the hydrothermal reaction is completed to obtain an electrode precursor;

[0016] Step (2) Electrodeposition reaction: dissolving nickel salt precursor and iron salt precursor, ammonium oxalate, buffer and ligand II, stirring to obtain an electrodeposition solution; depositing the electrode precursor in the electrodeposition solution by constant current; washing and drying to obtain the self-supporting oxygen evolution electrode.

[0017] Furthermore, in the above technical solution, the molar ratio of the cobalt salt precursor to the manganese salt precursor in the hydrothermal precursor solution is 2:1-2; the base is one or more of urea, potassium hydroxide, and sodium hydroxide; the ligand I is ammonium fluoride; and the base concentration in the hydrothermal precursor solution is 0.056 to 0.139 mol L -1 ; The concentration of complexing agent I is 0.026~0.071mol L -1 ; The concentration of cobalt salt precursor is 0.05-0.06 mol L -1 ;

[0018] In the electrodeposition solution, the molar ratio of the nickel salt precursor to the iron salt precursor is 1:1-3; the buffer is one or more of boric acid, sodium borate, and sodium citrate; the ligand II is an ammonium salt, including but not limited to oxalic acid; the buffer concentration in the electrodeposition solution is 0.050 to 0.148 mol L -1 The concentration of complexing agent II is 0.0011~0.0037mol L -1 ; The concentration of the nickel salt precursor is 0.0004-0.0006moL L -1 .

[0019] Furthermore, in the above technical solution, the drying in step (1) and step (2) is vacuum drying at a temperature of 50 to 100° C. and a time of 12 to 24 hours.

[0020] Furthermore, in the above technical solution, the hydrothermal reaction conditions are as follows: the temperature is controlled at 90-180°C, and the reaction time is controlled at 3-24h; the electrodeposition reaction conditions are as follows: the temperature is controlled at 20-50°C, and the current density is controlled at 10-20mA cm -2 The electrodeposition time is 40 to 60 minutes.

[0021] Furthermore, in the above technical solution, in step (1) and step (2), the stirring time is 30 to 60 minutes.

[0022] Furthermore, in the above technical solution, the self-supporting multi-layered nickel-iron double hydroxide-coated manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode obtained by combining the hydrothermal method and the electrodeposition method can be used to catalyze the oxygen evolution reaction in the process of hydrogen production by electrolysis of water under alkaline conditions.

[0023] The electrodes prepared by this method can be applied in renewable fuel cells, photoelectrocatalysis and alkaline anion exchange membrane (AEMWE) or alkaline medium water electrolysis.

[0024] The self-supporting electrode prepared by the method has good oxygen evolution performance and stability under alkaline conditions.

[0025] Beneficial effects

[0026] 1. Doping an appropriate amount of manganese into basic cobalt carbonate nanowires does not change the morphology of the nanowires, thereby improving the oxygen evolution performance. This is because manganese doping reduces the reaction energy barrier of the electrode during the electrocatalytic process, which is beneficial to the improvement of catalytic efficiency.

[0027] 2. Through electrodeposition reaction, nickel-iron double hydroxide nanosheets (two-dimensional) were successfully coated with manganese-doped basic cobalt carbonate nanowires (one-dimensional), ultimately obtaining a catalyst with a unique "branch-leaf" composite array structure. Among them, the manganese basic cobalt carbonate nanowires in the inner layer can effectively prevent the agglomeration of nickel-iron double hydroxide nanosheets, thereby facilitating electron transfer and providing a large number of edge and interface sites for water decomposition; while the outer layer of nickel-iron double hydroxide nanosheets intersect with each other to form rich and regular pores that coat the basic cobalt carbonate nanowires in the inner layer, which not only significantly increases the catalytic active sites, but also reduces the ion diffusion distance and transmission resistance. This special structural morphology of the electrode gives the electrode high catalytic activity and stability.

[0028] 3. Compared with powdered catalysts, the self-supporting nickel-iron double hydroxide-coated manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode obtained by the combined hydrothermal and electrodeposition methods has higher oxygen evolution catalytic activity, requires a smaller external bias voltage for electrolysis of water to produce hydrogen; the morphology is controllable; and compared with carbon-supported oxygen evolution electrocatalysts, it has better stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is an SEM image of the self-supporting multi-layered nickel-iron double hydroxide nanosheet-coated manganese-doped cobalt basic carbonate nanowire array oxygen evolution electrode obtained by the steps described in Example 1.

[0030] Figure 2 The self-supporting multi-layered nickel-iron double hydroxide coated manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode was obtained by the steps described in Example 1. The oxygen evolution performance was tested in a three-electrode system at room temperature with 1 mol L -1 The polarization curve was obtained by linear voltammetry scanning using KOH solution as the electrolyte.

[0031] Figure 3 The self-supporting multi-layered nickel-iron double hydroxide nanosheets coated with manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode obtained by the steps described in Example 1 were tested for oxygen evolution in a three-electrode system at room temperature. -1 KOH solution was used as electrolyte and the -2 Stability test was carried out under the following conditions.

[0032] Figure 4 This is the polarization curve of the self-supporting multi-layered nickel-iron double hydroxide nanosheets coated with manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode used as the AEMWE anode in the steps described in Example 1.

[0033] Figure 5The SEM image of the oxygen evolution electrode of the self-supporting multi-layered nickel-iron double hydroxide nanosheets coated with manganese-doped basic cobalt carbonate nanowire array was obtained by the steps described in Example 2.

[0034] Figure 6 The self-supporting multi-layered nickel-iron double hydroxide nanosheets coated with manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode was obtained by the steps described in Example 2. Oxygen evolution test was carried out in a three-electrode system at room temperature with 1 mol L -1 KOH solution was used as electrolyte and the -2 Stability test was carried out under the following conditions.

[0035] Figure 7 The self-supporting manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode was obtained by the steps described in Comparative Example 1. The oxygen evolution test was carried out in a three-electrode system at room temperature. -1 The polarization curve was obtained by linear voltammetry scanning using KOH solution as the electrolyte.

[0036] Figure 8 The steps described in Comparative Example 2 were used to obtain multi-sheet layered nickel-iron double hydroxide nanosheets loaded on a foam nickel-based oxygen evolution electrode. The oxygen evolution reaction test was carried out in a three-electrode system at room temperature. -1 The polarization curve was obtained by linear voltammetry scanning using KOH solution as the electrolyte.

[0037] Figure 9 This is an SEM image of the self-supporting multi-layered nickel-iron double hydroxide-coated manganese-doped cobalt basic carbonate nanowire array oxygen evolution electrode obtained in the step of Comparative Example 3.

[0038] Figure 10 This is an SEM image of a self-supporting multi-layered nickel-iron double hydroxide-coated manganese-doped cobalt basic carbonate nanowire array oxygen evolution electrode prepared by a combination of hydrothermal and electrodeposition methods in comparative example 4. DETAILED DESCRIPTION

[0039] The following is a further description of the preparation method, characteristics and application of the self-supporting multi-layered nickel-iron double hydroxide nanosheets coated with manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode obtained by combining the hydrothermal method and the electrodeposition method: Example 1

[0040] (1) Hydrothermal reaction:

[0041] 1.18g (0.056mol L) -1 ) cobalt nitrate hexahydrate, 0.49 g (0.028 mol L -1 ) manganese acetate, 0.49g (0.113mol L -1) urea and ammonium fluoride 0.148g (0.056mol L -1 ) was dissolved in 72 mL of deionized water; after thorough stirring for 30 minutes, a clear and transparent precursor solution was obtained; the cleaned nickel foam was vertically placed into the precursor solution. A hydrothermal reaction was carried out at 120°C for 5 hours; the obtained electrode was washed and vacuum dried at 60°C for 12 hours;

[0042] (2) Electrodeposition reaction:

[0043] The substrate is a manganese-doped basic cobalt carbonate nanowire array loaded on nickel foam obtained by hydrothermal reaction;

[0044] 0.04g(0.0005mol L -1 ) nickel nitrate hexahydrate and 0.08g (0.0015mol L -1 ) ferrous chloride tetrahydrate, 1.55g (0.1mol L -1 ) boric acid, 0.09 g (0.0025 mol L -1 ) ammonium oxalate was dissolved in 250 mL of deionized water. The reaction temperature was 30 °C and the current density was 10 mA cm -2 The deposition time was 50 min, and a self-supporting multi-layered nickel-iron double hydroxide-coated manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode was obtained by combining the hydrothermal method and the electrodeposition method.

[0045] Depend on Figure 1 It can be seen that after hydrothermal reaction and electrodeposition reaction, the morphology of the nickel-iron double hydroxide-coated manganese-doped cobalt basic carbonate nanowire array oxygen evolution electrode, which was controlled and synthesized and grown on a nickel foam substrate under relatively mild conditions, is as follows: the outer layer is composed of multiple layered nickel-iron double hydroxide nanosheets, and the inner layer is composed of manganese-doped cobalt basic carbonate nanowires, which are uniform in size and well dispersed, with a nanorod length of 2 to 3 μm and a diameter of about 100 to 500 nm.

[0046] Three-electrode oxygen evolution test: The three-electrode system uses oxygen to saturate 1 mol L -1 KOH solution was used as electrolyte and LSV scanning was performed on the self-supporting electrode, as shown in Figure 2 As shown. The self-supporting electrode prepared by this method is 1 mol L -1 In KOH electrolyte solution, when the current density is 100 mA cm -2 When the overpotential is 308mV. Figure 3 100mA cm shown -2 The electrolysis potential remained basically unchanged in the constant current test, indicating that the self-supporting electrode prepared by this method has good oxygen evolution electrocatalytic performance and stability under alkaline conditions.

[0047] AEMWE test: The loading was 0.4 mg cm -2 70wt.% Pt / C is coated on the alkaline anion membrane as the cathode of the AEMWE, and the anode is a previously prepared self-supporting multi-layered nickel-iron double hydroxide nanosheet coated with manganese-doped manganese-doped basic cobalt carbonate nanowire oxygen evolution electrode. The cathode and anode are separated by an alkaline anion exchange membrane and hot pressed to form a membrane electrode. Finally, the membrane electrode, flow field and end plates are assembled into an AEMWE electrolytic cell. The effective area of the membrane electrode is 2×2cm 2 , the test temperature is 70℃.

[0048] In this Example 1, a self-supporting multi-layered nickel-iron double hydroxide nanosheet coated with manganese-doped manganese-doped basic cobalt carbonate nanowire oxygen evolution electrode was prepared and used as the anode of AEMWE. The polarization curve is shown in FIG. Figure 4 As shown, under the following conditions close to industrial alkaline water electrolysis, the single cell performance is 0.5A cm -2 When the electrolysis voltage is 1.69 V, the industrial application prospect is good.

[0049] Example 2

[0050] (1) Hydrothermal reaction:

[0051] 1.18g (0.056mol L) -1 ) cobalt nitrate hexahydrate, 0.49 g (0.028 mol L -1 ) manganese acetate, 0.49g (0.113mol L -1 ) urea and ammonium fluoride 0.148g (0.056mol L -1 ) was dissolved in 72 mL of deionized water; after thorough stirring for 30 minutes, a clear and transparent precursor solution was obtained; the cleaned nickel foam was vertically placed into the precursor solution. A hydrothermal reaction was carried out at 120°C for 5 hours; the obtained electrode was washed and vacuum dried at 60°C for 12 hours;

[0052] (2) Electrodeposition reaction:

[0053] The substrate is a manganese-doped basic cobalt carbonate nanowire array loaded on nickel foam obtained by hydrothermal reaction;

[0054] 0.04g(0.0005mol L -1 ) nickel nitrate hexahydrate and 0.08g (0.0015mol L -1 ) ferrous chloride tetrahydrate, 1.55g (0.1mol L -1 ) boric acid, 0.09 g (0.0025 mol L -1 ) ammonium oxalate, the reaction temperature was 30 °C, and the current density was 10 mA cm -2The deposition time was 40 min, and a self-supporting multi-layered nickel-iron double hydroxide nanosheet-coated manganese-doped manganese-doped basic cobalt carbonate nanowire oxygen evolution electrode was obtained by combining the hydrothermal method and the electrodeposition method.

[0055] Depend on Figure 5 It can be seen that after hydrothermal reaction and electrodeposition reaction, the nickel-iron double hydroxide-coated manganese-doped cobalt basic carbonate nanowire array oxygen evolution electrode grown on a nickel foam substrate is controlled and synthesized under relatively mild conditions. The morphology characteristics are: the nanorods are 2 to 3 μm long and have a diameter of about 100 to 500 nm.

[0056] Three-electrode oxygen evolution test: The three-electrode system uses oxygen to saturate 1 mol L -1 KOH solution was used as electrolyte and LSV scanning was performed on the self-supporting electrode, as shown in Figure 6 As shown. The self-supporting electrode prepared by this method is 1 mol L -1 In KOH electrolyte solution, when the current density is 100 mA cm -2 When , the overpotential is 322 mV. This performance is lower than that of Example 1, indicating that the morphology and structure obtained in Example 1 are optimal, thus having better OER performance.

[0057] Comparative Example 1

[0058] As described in Example 1, only the hydrothermal reaction step was used, and 1.18 g (0.056 mol L -1 ) cobalt nitrate hexahydrate, 0.49 g (0.028 mol L -1 ) manganese acetate, 0.49g (0.113mol L -1 ) urea and ammonium fluoride 0.148g (0.056mol L -1 ) was dissolved in 72 mL of deionized water; after thorough stirring for 30 minutes, a clear and transparent precursor solution was obtained; the cleaned nickel foam was vertically placed into the precursor solution. A hydrothermal reaction was carried out at 120°C for 5 hours; the obtained electrode was washed and vacuum dried at 60°C for 12 hours;

[0059] The prepared self-supporting manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode was tested in a three-electrode system at room temperature with a half-cell test. -1 The polarization curve was obtained by linear voltammetry scanning using KOH solution as the electrolyte. The test conditions were the same as those in Example 1.

[0060] Three-electrode test: The three-electrode system uses oxygen to saturate 1 mol L -1 KOH solution is used as electrolyte, self-supporting battery

[0061] Perform LSV scan, such as Figure 7As shown. The self-supporting electrode prepared by this method is 1 mol L -1 100 mA cm in KOH electrolyte solution -2 At the electrolysis current density of , the overpotential is 350 mV.

[0062] Comparative Example 2

[0063] The electrodeposition reaction was carried out according to the steps described in Example 1, with the cleaned nickel foam as the base; 0.04g (0.0005mol L -1 ) nickel nitrate hexahydrate and 0.08g (0.0015mol L -1 ) ferrous chloride tetrahydrate, 1.55g (0.1mol L -1 ) boric acid, 0.09 g (0.0025 mol L -1 ) ammonium oxalate, the reaction temperature was 30 °C, and the current density was 10 mA cm -2 The deposition time was 40 min, and a self-supporting multi-layered nickel-iron double hydroxide nanosheet oxygen evolution electrode was obtained by electrodeposition.

[0064] The obtained nickel-iron double hydroxide nanosheets were loaded on the nickel foam substrate oxygen evolution electrode; at room temperature, a half-cell test was carried out in a three-electrode system with 1 mol L -1 The polarization curve was obtained by linear voltammetry scanning using KOH solution as the electrolyte. The test conditions were the same as those in Example 1.

[0065] Three-electrode system test: The three-electrode system uses oxygen to saturate 1 mol L -1 KOH solution was used as electrolyte and the electrode was subjected to LSV scanning. Figure 8 The self-supporting oxygen evolution electrode prepared by this method is 1 mol L -1 100 mA cm in KOH electrolyte solution -2 At a current density of , the overpotential is 342 mV.

[0066] Comparative Example 3

[0067] (1) Hydrothermal reaction:

[0068] 1.18g (0.056mol L) -1 ) cobalt nitrate hexahydrate, 0.49 g (0.028 mol L -1 ) manganese acetate, 0.49g (0.113mol L -1 ) urea and ammonium fluoride 0.148g (0.056mol L -1) was dissolved in 72 mL of deionized water; after thorough stirring for 30 minutes, a clear and transparent precursor solution was obtained; the cleaned nickel foam was vertically placed into the precursor solution. A hydrothermal reaction was carried out at 120°C for 5 hours; the obtained electrode was washed and vacuum dried at 60°C for 12 hours;

[0069] (2) Electrodeposition reaction:

[0070] The substrate is a manganese-doped basic cobalt carbonate nanowire array loaded on nickel foam obtained by hydrothermal reaction;

[0071] 0.04g(0.0005mol L -1 ) nickel nitrate hexahydrate and 0.08g (0.0015mol L -1 ) ferrous chloride tetrahydrate, 1.55g (0.1mol L -1 ) boric acid, 0.09 g (0.0025 mol L -1 ) ammonium oxalate, the reaction temperature was 30 °C, and the current density was 5 mA cm -2 The deposition time was 40 min, and a self-supporting multi-layered nickel-iron double hydroxide nanosheet-coated manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode was obtained by combining the hydrothermal method and the electrodeposition method.

[0072] Depend on Figure 9 It can be seen that after two reactions, the morphology of the self-supporting oxygen evolution electrode obtained under this condition is: the nickel-iron double hydroxide nanosheets are only partially coated on the upper end of the manganese-doped cobalt basic carbonate nanowire array.

[0073] Comparative Example 4

[0074] (1) Hydrothermal reaction:

[0075] 1.18g (0.056mol L) -1 ) cobalt nitrate hexahydrate, 0.49 g (0.028 mol L -1 ) manganese acetate, 0.49g (0.113mol L -1 ) urea and ammonium fluoride 0.148g (0.056mol L -1 ) was dissolved in 72 mL of deionized water; after thorough stirring for 30 minutes, a clear and transparent precursor solution was obtained; the cleaned nickel foam was vertically placed into the precursor solution. A hydrothermal reaction was carried out at 120°C for 5 hours; the obtained electrode was washed and vacuum dried at 60°C for 12 hours;

[0076] (2) Electrodeposition reaction:

[0077] The substrate is a manganese-doped basic cobalt carbonate nanowire array loaded on nickel foam obtained by hydrothermal reaction;

[0078] 0.04g(0.0005mol L -1 ) nickel nitrate hexahydrate and 0.08g (0.0015mol L -1 ) ferrous chloride tetrahydrate, 1.55g (0.1mol L -1 ) boric acid, 0.09 g (0.0025 mol L -1 ) ammonium oxalate, the reaction temperature was 30 °C, and the current density was 10 mA cm -2 , the deposition time is 20min, and a self-supporting multi-layered nickel-iron double hydroxide nanosheet coated with manganese-doped basic cobalt carbonate nanowire array oxygen evolution electrode is obtained by combining hydrothermal method and electrodeposition method. Figure 10 It can be seen that after two reactions, the morphology of the self-supporting oxygen evolution electrode obtained under this condition is: nickel-iron double hydroxide nanosheets are partially coated on the manganese-doped cobalt basic carbonate nanowire array, but the coating is uneven.

Claims

1. A method for preparing a self-supporting oxygen evolution electrode, characterized in that: The electrode comprises a nickel foam substrate and a catalytically active component; the catalytically active component is a nanorod structure vertically grown on the surface of the nickel foam substrate; the nanorod structure comprises a linear manganese-doped basic cobalt carbonate located inside and a multi-layered nickel-iron double hydroxide wrapped around the surface of the linear manganese-doped basic cobalt carbonate; the nanorods are uniform in size, with a length of 2 to 3 μm and a diameter of 100 to 500 nm; The preparation method comprises the following steps: Step (1) hydrothermal reaction: dissolving a cobalt salt precursor, a manganese salt precursor, a base and a ligand I, stirring to obtain a hydrothermal precursor solution, subjecting the hydrothermal precursor solution to a hydrothermal reaction with nickel foam, and washing and drying the obtained nickel foam after the hydrothermal reaction to obtain an electrode precursor; Step (2) Electrodeposition reaction: dissolving a nickel salt precursor and an iron salt precursor, ammonium oxalate, a buffer and a ligand II, and stirring to obtain an electrodeposition solution; depositing an electrode precursor in the electrodeposition solution at a constant current; washing and drying to obtain the self-supporting oxygen evolution electrode; The hydrothermal reaction conditions are as follows: the hydrothermal reaction temperature is controlled at 90-180°C, and the reaction time is controlled at 3-24h; The reaction conditions of the electrodeposition are as follows: the temperature is controlled at 20-50°C, the current density is 10-20 mA cm -2 The electrodeposition time is 40 to 60 minutes.

2. The preparation method according to claim 1, characterized in that: In the electrode, the weight ratio of nickel-iron double hydroxide to manganese-doped basic cobalt carbonate is 1±0.005:4±0.

005.

3. The preparation method according to claim 1, characterized in that: The nickel content in the nickel-iron double hydroxide is 5-10 wt%; the manganese content in the manganese-doped basic cobalt carbonate is 3-5 wt%; and the loading amount of the catalytic active component per unit area on the nickel foam substrate is 0.012-0.015 g cm -2 .

4. The preparation method according to claim 1, characterized in that: In the hydrothermal precursor solution, the molar ratio of the cobalt salt precursor to the manganese salt precursor is 2:1-2; the base is one or more of urea, potassium hydroxide, and sodium hydroxide; the coordination agent I is ammonium fluoride; and the base concentration in the hydrothermal precursor solution is 0.056 to 0.139 mol L -1 ; The concentration of complexing agent I is 0.026~0.071mol L -1 ; The concentration of cobalt salt precursor is 0.05-0.06molL -1 ; In the electroplating solution, the molar ratio of the nickel salt precursor to the iron salt precursor is 1:1-3; the buffer is one or more of boric acid, sodium borate, and sodium citrate; the ligand II is an ammonium salt, and the ammonium salt includes oxalic acid; the buffer concentration in the electroplating solution is 0.050 to 0.148 mol L -1 ; The concentration of complexing agent II is 0.0011~0.0037mol L -1 ; The concentration of the nickel salt precursor is 0.0004-0.0006moL L -1 .

5. The preparation method according to claim 1, characterized in that: The drying in step (1) and step (2) is vacuum drying at a temperature of 50 to 100° C. for 12 to 24 hours.

6. The preparation method according to any one of claims 1 to 5, characterized in that: In the steps (1) and (2), the stirring time is 30 to 60 minutes.

7. The electrode prepared by the method according to any one of claims 1 to 5 is used for oxygen evolution reaction in the process of hydrogen production by electrolysis of water under alkaline conditions.

8. The electrode obtained by the preparation method according to any one of claims 1 to 5 is used in fuel cells, photoelectrocatalysis, alkaline anion exchange membranes or alkaline medium water electrolysis processes.

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