A transition metal-doped nickel oxyhydroxide catalyst and its preparation method and application

Abstract

The invention discloses a transition metal-doped nickel hydroxide catalyst and a preparation method and application thereof, belonging to the field of hydrogen production by seawater electrolysis. The method comprises: (1) constructing a three-electrode system, using a conductive substrate as a working electrode, a mixed metal salt solution as an electrolyte, performing electrodeposition by a constant voltage method, and taking out a conductive substrate loaded with a pre-catalyst; wherein the mixed metal salt solution comprises a first metal salt, a nickel salt, a second metal salt, an iron salt, and a third metal salt, and the third metal salt is at least one of a cobalt salt, a chromium salt, a manganese salt, and a molybdenum salt; (2) constructing a three-electrode system, using a conductive substrate loaded with a pre-catalyst as a working electrode, an alkaline solution as an electrolyte, and using a constant current method to in-situ convert the pre-catalyst into a transition metal-doped nickel hydroxide catalyst; the catalyst has high catalytic activity, high selectivity and high stability, can operate stably for a long time at a high current density, and has great application potential in seawater electrolysis hydrogen production systems.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrogen production by seawater electrolysis, and specifically relates to a transition metal-doped nickel oxyhydroxide catalyst and a preparation method and application thereof. Background Art

[0002] As a green energy source, hydrogen has high energy density and pollution-free combustion products, and is considered to be an ideal alternative energy source to traditional fossil fuels. The technology of direct electrolysis of seawater to produce hydrogen has always been regarded as a major challenge and difficulty in the field of scientific research. The composition of seawater is complex (about 92 chemical elements), the salinity is about 3.5wt.%, and the pH is between 7.5 and 8.4, of which 90% is sodium chloride. The concentration of chloride ions in seawater can reach 0.5M. First, the presence of a large number of chloride ions will cause a chlorine evolution reaction during the anode electrolysis reaction, competing with the oxygen evolution reaction. Chlorine dissolved in water will generate hypochlorous acid, which corrodes the electrode; secondly, the chloride ions in seawater will cause chemical corrosion of the metal catalyst substrate. Therefore, the main difficulty of hydrogen production by seawater electrolysis is concentrated on the design of the anode catalyst. At the same time, under the conditions of high current density for industrial applications, higher requirements will be placed on the selectivity and corrosion resistance of the anode catalyst oxygen evolution reaction.

[0003] In the prior art, researchers are committed to the development of catalysts for hydrogen production by electrolysis of seawater. For example, the Chinese patent document with publication number CN113046782A discloses a method for preparing a nickel foam-loaded cuprous oxide octahedron catalyst by an in-situ process, which has better interface contact and binder-free characteristics, can effectively improve electron conversion, and has good hydrogen evolution performance as a cathode catalyst in simulated seawater; the Chinese patent document with publication number CN116497387A discloses an anode water oxidation catalyst suitable for hydrogen production by electrolysis of seawater and a preparation method thereof, the inventive method first prepares a transition metal salt mixture and treats nickel foam, and uses the treated nickel foam as a growth substrate, and places the growth substrate and the transition metal salt mixture into a reactor for hydrothermal reaction to generate the required precursor catalyst; then, a specific voltage is applied to the precursor catalyst in an alkaline solution for rapid electro-oxidation reconstruction to form a NiFeOOH catalyst, and the NiFeOOH catalyst has high catalytic performance. However, when it is operated for a long time in a seawater electrolyte, its performance decays too fast, and it cannot guarantee long-term and efficient hydrogen production by electrolysis of water.

[0004] In addition, some studies on seawater electrolysis catalysts have prevented chlorine corrosion by loading carbon-based anti-corrosion coatings on the catalyst surface and preparing anti-chlorine groups such as sulfate and phosphate on the catalyst surface. However, they all have disadvantages. For example, loading anti-corrosion coatings on the surface will significantly increase the resistance of the catalyst, which is not conducive to the efficiency of water electrolysis reaction. At the same time, the working current density of existing seawater electrolysis anode catalysts is mostly lower than 500mA cm -2, the working hours are mostly less than 500 hours, and the working conditions that may be aggravated by the increase in chloride ion concentration after a long reaction time are not considered. It can be seen that breaking through the technical bottleneck of seawater electrolysis hydrogen production lies in the development of catalyst materials that are suitable for seawater environments and can work efficiently and stably under high current density conditions. Summary of the invention

[0005] The present invention provides a method for preparing a transition metal-doped nickel hydroxide catalyst. The process is simple and efficient. The prepared transition metal-doped nickel hydroxide catalyst has the characteristics of high catalytic activity, high selectivity and high stability, can operate stably for a long time under high current density conditions, and has great application potential in seawater direct electrolysis hydrogen production systems.

[0006] The specific technical solutions adopted are as follows:

[0007] A method for preparing a transition metal-doped nickel oxyhydroxide catalyst comprises the following steps:

[0008] (1) preparing a mixed metal salt solution, using a conductive substrate as a working electrode, a platinum electrode as a counter electrode, a saturated calomel electrode as a reference electrode, and the mixed metal salt solution as an electrolyte, performing electrodeposition by a constant voltage method or a constant current method, and taking out the conductive substrate loaded with the precatalyst;

[0009] (2) using the conductive substrate loaded with the precatalyst in step (1) as a working electrode, a platinum electrode as a counter electrode, a saturated calomel electrode as a reference electrode, and an alkaline solution as an electrolyte, and using a constant current method to in-situ convert the precatalyst to form a transition metal-doped nickel hydroxide catalyst;

[0010] The mixed metal salt solution comprises a first metal salt, a second metal salt and a third metal salt, wherein the first metal salt is a nickel salt, the second metal salt is an iron salt, and the third metal salt is at least one of a cobalt salt, a chromium salt, a manganese salt and a molybdenum salt.

[0011] The present invention firstly adopts an electrodeposition method to load transition metal-doped nickel iron oxide (hydroxide) on a substrate, and further adopts an anodic oxidation reaction to in-situ convert the transition metal-doped nickel iron oxide (hydroxide) into a transition metal-doped nickel hydroxide catalyst. Through the lattice mismatch formed by doping a third metal element (transition metal element), the nickel iron oxide (hydroxide) originally in a loose sheet shape is induced to be deformed into a dense cluster structure to protect the substrate. At the same time, transition metal oxides such as chromium, cobalt, manganese or molybdenum in an amorphous state are resistant to chloride ion corrosion in seawater, so that the transition metal-doped nickel hydroxide catalyst has high catalytic activity, high selectivity and stability in the application of direct seawater electrolysis to produce hydrogen.

[0012] Preferably, the first metal salt is nickel nitrate, the second metal salt is iron nitrate, and the third metal salt is one or two of cobalt nitrate, chromium nitrate, manganese nitrate, and molybdenum nitrate.

[0013] Optionally, in the mixed metal salt solution, the molar ratio of the first metal salt, the second metal salt and the third metal salt is 1-4:0.5-2:1, and the molar concentration of the first metal salt in the mixed metal salt solution is 15-20 mM.

[0014] The conductive substrate includes carbon paper, carbon cloth or nickel foam.

[0015] Preferably, in step (1), the conditions for electrodeposition using the constant voltage method are: voltage -1 to -0.9 V, temperature 20 to 30° C., and time 50 to 70 min; the conditions for electrodeposition using the constant current method are -5 to -10 mA, temperature 20 to 30° C., and time 50 to 70 min.

[0016] Optionally, the alkaline solution is deionized water, simulated seawater or natural seawater solution containing potassium hydroxide or sodium hydroxide, and the concentration of potassium hydroxide or sodium hydroxide is 0.1-3M.

[0017] Preferably, in step (2), the conditions for in-situ conversion of the precatalyst to form the transition metal-doped nickel hydroxide catalyst by constant current method are: current density 20 to 200 mA cm -2 , temperature 20-40℃, time 6-24h.

[0018] The present invention also provides a transition metal-doped nickel oxyhydroxide catalyst prepared by the preparation method of the transition metal-doped nickel oxyhydroxide catalyst.

[0019] The present invention also provides the use of the transition metal-doped nickel hydroxide oxycatalyst in hydrogen production by seawater electrolysis.

[0020] The present invention also provides a method for producing hydrogen by electrolyzing seawater, using the transition metal-doped nickel hydroxide catalyst.

[0021] Furthermore, hydrogen is produced by electrolysis of seawater using a two-electrode system of an electrochemical workstation, the working electrode is the transition metal-doped nickel hydroxide catalyst, the platinum mesh is the counter electrode, and the electrolyte is natural seawater prepared with 2M KOH or a 0.5M NaCl solution or a 2M NaCl solution.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention first loads transition metal-doped nickel iron oxide (hydroxide) on a substrate by electrodeposition, and then uses this as an anode (working electrode). The transition metal-doped nickel iron oxide (hydroxide) is in situ converted into a transition metal-doped nickel hydroxide catalyst by an anodic oxidation reaction. The lattice mismatch formed by transition metal element doping induces the originally loose flaky nickel iron oxide (hydroxide) to be deformed into a dense cluster structure to protect the substrate. At the same time, transition metal oxides such as chromium, cobalt or manganese in an amorphous state are resistant to chloride ion corrosion in seawater, so that the transition metal-doped nickel hydroxide catalyst has high catalytic activity, high selectivity and stability in the application of direct seawater electrolysis to produce hydrogen.

[0024] (2) The present invention adopts a two-step electrochemical method to prepare transition metal-doped nickel hydroxide catalysts. The process is simple and easy, the raw materials are easy to obtain, and it is convenient for large-scale production. It has good application prospects in the direct electrolysis of seawater to produce hydrogen system.

[0025] (3) The transition metal-doped nickel hydroxide catalyst provided by the present invention was subjected to a high chloride ion concentration simulated alkaline seawater electrolyte (2.0 M KOH + 2.0 M NaCl) at 500 mA cm -2 The current density of the electrolyte was stable for 6000 h, and the electrolyte was used in alkaline seawater electrolyte (2.0 M KOH + 0.5 M NaCl) with a current density of 500 mA cm -2 The current density of the electrolyte was stable for 6500h, and the current density of the electrolyte was stable for 6500h. -2 The current density can be stably operated for more than 2800 hours. During the electrolysis process, the Faraday efficiency of the oxygen evolution reaction of the transition metal-doped nickel hydroxide catalyst reaches more than 99%. It has the characteristics of high catalytic activity, high selectivity and high stability, and can operate stably for a long time under high current density conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a scanning electron microscope image of the iron-cobalt-chromium doped nickel hydroxide catalyst prepared in Example 1.

[0027] Figure 2 1 is the X-ray diffraction spectrum of the NiFeCoCr precatalyst and the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1.

[0028] Figure 3 The voltage-current curve of the electrochemical oxidation process of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 was carried out by linear sweep voltammetry in 2.0M KOH+0.5M NaCl electrolyte.

[0029] Figure 4 The voltage-current curve of the electrochemical oxidation process of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 was carried out by linear sweep voltammetry in 2.0M KOH+2.0M NaCl electrolyte.

[0030] Figure 5 The voltage-current curve of the electrochemical oxidation process of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 was carried out by linear sweep voltammetry in 2.0 M KOH + natural seawater electrolyte.

[0031] Figure 6 This is a Faraday efficiency diagram of the oxygen evolution reaction in an alkaline anion exchange membrane electrolytic cell using the iron, cobalt, and chromium doped nickel hydroxide catalyst in Example 1 as the working electrode in an electrolyte consisting of 2.0 M KOH + 0.5 M NaCl.

[0032] Figure 7 This is a Faraday efficiency diagram of the oxygen evolution reaction in an alkaline anion exchange membrane electrolytic cell using the iron, cobalt, and chromium doped nickel hydroxide catalyst in Example 1 as the working electrode in an electrolyte consisting of 2.0M KOH+2M NaCl.

[0033] Figure 8 This is a stability test graph of the iron, cobalt and chromium doped nickel hydroxide catalyst in Example 1 obtained by constant current method in 2.0M KOH+0.5M NaCl electrolyte.

[0034] Fig. 9 This is a stability test graph of the iron, cobalt and chromium doped nickel hydroxide catalyst in Example 1 obtained by constant current method in 2.0M KOH+2M NaCl electrolyte.

[0035] Fig.10 This is a stability test graph of the iron, cobalt, and chromium doped nickel hydroxide catalyst in Example 1 obtained by constant current method in 2.0M KOH+natural seawater electrolyte. DETAILED DESCRIPTION

[0036] The present invention is further illustrated below in conjunction with the examples and accompanying drawings. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0037] Example 1

[0038] This embodiment provides a method for preparing an iron-cobalt-chromium doped nickel oxyhydroxide catalyst, comprising the following steps:

[0039] (1) Under room temperature, 2.7 mmol of nickel nitrate, 0.9 mmol of iron nitrate, 0.9 mmol of cobalt nitrate and 0.9 mmol of chromium nitrate were added to a circular glass electrolytic cell, and deionized water was added to 150 mL and stirred to obtain a mixed metal salt solution; a three-electrode system was constructed, with 1 cm*1 cm nickel foam as the working electrode (anode), a platinum electrode as the counter electrode, a saturated calomel electrode as the reference electrode, and the mixed metal salt solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage circuit, and a constant voltage method was used for deposition. The constant voltage was set to -0.9 V, the temperature was 25° C., and the deposition time was 1 hour. The nickel foam loaded with the NiFeCoCr precatalyst was taken out;

[0040] (2) The nickel foam loaded with NiFeCoCr precatalyst was rinsed with deionized water, and a three-electrode system was constructed, with the nickel foam loaded with NiFeCoCr precatalyst as the working electrode (anode), the platinum electrode as the counter electrode, the saturated calomel electrode as the reference electrode, and a 2M KOH aqueous solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage loop, and the constant current was set to 100 mA cm -2 , temperature 25°C, time 12 hours, using a constant current method to in-situ convert the pre-catalyst to form an iron-cobalt-chromium-doped nickel-hydroxy oxide catalyst, the iron-cobalt-chromium-doped nickel-hydroxy oxide catalyst having a cobalt-based oxide and a chromium-based oxide passivation layer.

[0041] Example 2

[0042] This embodiment provides a method for preparing an iron-cobalt doped nickel oxyhydroxide catalyst, comprising the following steps:

[0043] (1) Under room temperature, 2.7 mmol of nickel nitrate, 0.9 mmol of iron nitrate and 0.9 mmol of cobalt nitrate were added to a circular glass electrolytic cell, and deionized water was added to 150 mL and stirred evenly to obtain a mixed metal salt solution; a three-electrode system was constructed, with 1 cm*1 cm nickel foam as the working electrode (anode), a platinum electrode as the counter electrode, a saturated calomel electrode as the reference electrode, and the mixed metal salt solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage circuit, and a constant voltage method was used for deposition. The constant voltage was set to -1 V, the temperature was 30°C, and the deposition time was 1 hour. The nickel foam loaded with the NiFeCo precatalyst was taken out;

[0044] (2) The nickel foam loaded with NiFeCo precatalyst was rinsed with deionized water, and a three-electrode system was constructed, with the nickel foam loaded with NiFeCo precatalyst as the working electrode (anode), the platinum electrode as the counter electrode, the saturated calomel electrode as the reference electrode, and a 2M KOH aqueous solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage loop, and the constant current was set to 200 mA cm -2 , temperature 30° C., time 24 hours, using a constant current method to in-situ convert the pre-catalyst to form an iron-cobalt-doped nickel hydroxide catalyst, wherein the iron-cobalt-doped nickel hydroxide catalyst has a cobalt-based oxide passivation layer.

[0045] Example 3

[0046] This embodiment provides a method for preparing an iron-chromium doped nickel oxyhydroxide catalyst, comprising the following steps:

[0047] (1) Under room temperature, 2.7 mmol of nickel nitrate, 0.9 mmol of ferric nitrate and 0.9 mmol of chromium nitrate were added to a circular glass electrolytic cell, and deionized water was added to 150 mL and stirred to obtain a mixed metal salt solution; a three-electrode system was constructed, with 1 cm*1 cm nickel foam as the working electrode (anode), a platinum electrode as the counter electrode, a saturated calomel electrode as the reference electrode, and the mixed metal salt solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage loop, and a constant current method was used for deposition. The constant current was set to -7.5 mA, the temperature was 25° C., and the deposition time was 1 hour. The nickel foam loaded with the NiFeCr precatalyst was taken out;

[0048] (2) The nickel foam loaded with NiFeCr precatalyst was rinsed with deionized water, and a three-electrode system was constructed, with the nickel foam loaded with NiFeCr precatalyst as the working electrode (anode), the platinum electrode as the counter electrode, the saturated calomel electrode as the reference electrode, and a 2M KOH aqueous solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage loop, and the constant current was set to 100 mA cm -2 , temperature 25° C., time 12 hours, using a constant current method to in-situ convert the pre-catalyst to form an iron-chromium-doped nickel hydroxide catalyst, the iron-chromium-doped nickel hydroxide catalyst having a chromium-based oxide passivation layer.

[0049] Example 4

[0050] This embodiment provides a method for preparing an iron-manganese-doped nickel oxyhydroxide catalyst, comprising the following steps:

[0051] (1) Under room temperature, 3 mmol of nickel nitrate, 1.8 mmol of iron nitrate and 1.2 mmol of manganese nitrate were added to a circular glass electrolytic cell, and deionized water was added to 150 mL and stirred to obtain a mixed metal salt solution; a three-electrode system was constructed, with 1 cm*1 cm nickel foam as the working electrode (anode), a platinum electrode as the counter electrode, a saturated calomel electrode as the reference electrode, and the mixed metal salt solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage circuit, and a constant current method was used for deposition. The constant current was set to -10 mA, the temperature was 20°C, and the deposition time was 70 min. The nickel foam loaded with NiFeMn precatalyst was taken out;

[0052] (2) The nickel foam loaded with NiFeMn precatalyst was rinsed with deionized water, and a three-electrode system was constructed, with the nickel foam loaded with NiFeMn precatalyst as the working electrode (anode), the platinum electrode as the counter electrode, the saturated calomel electrode as the reference electrode, and a 2M KOH aqueous solution as the electrolyte. The three-electrode system was connected to an electrochemical workstation to form a complete current and voltage loop, and the constant current was set to 100 mA cm -2 , temperature 20° C., time 18 hours, using a constant current method to in-situ convert the precatalyst to form an iron-manganese-doped nickel hydroxide catalyst, the iron-manganese-doped nickel hydroxide catalyst having a manganese-based oxide passivation layer.

[0053] Sample analysis

[0054] The precatalyst prepared in Example 1 and the iron-cobalt-chromium doped nickel hydroxide oxide catalyst were characterized and tested.

[0055] Figure 1 This is a scanning electron microscope image of the iron-cobalt-chromium doped nickel hydroxide oxide catalyst prepared in Example 1. As can be seen from the figure, the iron-cobalt-chromium doped nickel hydroxide oxide catalyst consists of a block catalyst layer closely attached to the foam nickel substrate and a block catalyst attached to the block catalyst layer.

[0056] Figure 2The X-ray diffraction spectra of the NiFeCoCr precatalyst and the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1. It can be seen from the figure that the diffraction peak of the NiFeCoCr precatalyst corresponds to the phase card of nickel-iron layered double hydroxide numbered JCPDS#40-0215, and the diffraction peak of the iron-cobalt-chromium doped nickel hydroxide catalyst corresponds to the phase card of nickel hydroxide numbered JCPDS#06-0141, which proves that after the constant current electrochemical oxidation process, the nickel-based oxide (hydroxide) in the precatalyst is converted into nickel hydroxide with higher electrochemical activity, while no obvious diffraction peaks of iron-cobalt-chromium and its oxide are observed and the amorphous phase is obvious, which proves that iron-cobalt-chromium is doped in the catalyst in the form of amorphous oxide.

[0057] Figure 3 The voltage-current curve of the electrochemical oxidation process of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 by linear sweep voltammetry in 2.0M KOH+0.5M NaCl electrolyte can be seen from the figure. Its oxygen evolution reaction activity is better than that of the pure nickel-iron layered double metal hydroxide catalyst prepared in the literature (X. Lu, C. Zhao, Electrodeposition of hierarchically structured three-dimensional nickel–irone electrodes for efficient oxygen evolution at high current densities, Nature Communications, 6 (2015) 6616.), indicating that the catalyst has excellent electrocatalytic activity in alkaline simulated seawater electrolyte with conventional chloride ion concentration.

[0058] Figure 4 The voltage-current curve of the electrochemical oxidation process of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 by linear sweep voltammetry in 2.0M KOH+2.0M NaCl electrolyte can be seen from the figure that its oxygen evolution reaction activity is better than that of the pure nickel-iron layered double metal hydroxide catalyst, indicating that the catalyst has excellent electrocatalytic activity in ultra-high chloride ion concentration and highly corrosive alkaline simulated seawater electrolyte.

[0059] Figure 5 The voltage-current curve of the electrochemical oxidation process of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 by linear sweep voltammetry in 2.0M KOH+natural seawater electrolyte can be seen from the figure. Its oxygen evolution reaction activity is better than that of the pure nickel-iron layered double metal hydroxide catalyst, indicating that the catalyst has excellent electrocatalytic activity in alkaline natural seawater electrolyte.

[0060] Figure 6 The Faraday efficiency diagram of the oxygen evolution reaction in the alkaline anion exchange membrane electrolytic cell with the Fe-Co-Cr doped nickel hydroxide catalyst as the working electrode in Example 1 in the electrolyte composed of 2.0M KOH+0.5M NaCl is shown in the figure. It can be seen that the catalyst has a Faraday efficiency of 100mA cm in the electrolyte composed of 2.0M KOH+0.5M NaCl. -2 , 250mA cm -2 and 500mA cm -2 The Faradaic efficiency of the oxygen evolution reaction at a current density of 2.544 W / m was higher than 96%, demonstrating that the catalyst has excellent selectivity for oxygen evolution reaction in alkaline simulated seawater electrolyte with conventional chloride ion concentration.

[0061] Figure 7 The Faraday efficiency diagram of the oxygen evolution reaction in the alkaline anion exchange membrane electrolytic cell with the Fe-Co-Cr doped nickel hydroxide catalyst as the working electrode in Example 1 in the electrolyte composed of 2.0 M KOH + 2.0 M NaCl is shown in the figure. It can be seen that the catalyst has a Faraday efficiency of 100 mA cm in the electrolyte composed of 2.0 M KOH + 2.0 M NaCl. -2 , 250mA cm -2 and 500mA cm -2 The Faradaic efficiency of the oxygen evolution reaction at a current density of 2.54 Å was higher than 96%, demonstrating that the catalyst has excellent selectivity for oxygen evolution reaction in alkaline simulated seawater electrolyte with ultra-high chloride ion concentration.

[0062] Figure 8 This is a stability test chart of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 obtained by constant current method in 2.0M KOH+0.5M NaCl electrolyte. The current value used in the test is 500mA cm -2 The test results show that the catalyst can -2 The catalyst has worked stably for more than 6500 hours at a high current density and the test is still ongoing, which shows that the catalyst has excellent stability in alkaline simulated seawater electrolyte with conventional chloride ion concentration.

[0063] Fig. 9 This is a stability test chart of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 obtained by constant current method in 2.0M KOH+2.0M NaCl electrolyte. The current value used in the test is 500mA cm -2 The test results show that the catalyst can -2The catalyst has worked stably for more than 6000 hours at a high current density, and the test is still ongoing, demonstrating that the catalyst has excellent stability in alkaline simulated seawater electrolyte with ultra-high chloride ion concentration.

[0064] Fig.10 This is a stability test chart of the iron-cobalt-chromium doped nickel hydroxide catalyst in Example 1 in 2.0M KOH+natural seawater electrolyte, obtained by constant current method. The current value used in the test is 500mA cm -2 The test results show that the catalyst can -2 The catalyst has worked stably for more than 2800 hours at a high current density and the test is still ongoing, demonstrating the excellent stability of the catalyst in alkaline natural seawater electrolyte.

[0065] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a transition metal-doped nickel oxyhydroxide catalyst, characterized in that: The following steps are involved: (1) preparing a mixed metal salt solution, using a conductive substrate as a working electrode, a platinum electrode as a counter electrode, a saturated calomel electrode as a reference electrode, and the mixed metal salt solution as an electrolyte, performing electrodeposition by a constant voltage method or a constant current method, and taking out a conductive substrate loaded with a pre-catalyst; (2) using the conductive substrate loaded with the pre-catalyst in step (1) as the working electrode, the platinum electrode as the counter electrode, the saturated calomel electrode as the reference electrode, and the alkaline solution as the electrolyte, the pre-catalyst is in situ converted into a transition metal-doped nickel hydroxide catalyst by a constant current method; The mixed metal salt solution comprises a first metal salt, a second metal salt and a third metal salt, wherein the first metal salt is a nickel salt, the second metal salt is an iron salt, and the third metal salt is a cobalt salt and a chromium salt; In the mixed metal salt solution, the molar ratio of the first metal salt, the second metal salt and the third metal salt is 1 to 4:0.5 to 2:1; In step (2), the conditions for in-situ conversion of the precatalyst to form the transition metal-doped nickel hydroxide catalyst by constant current method are: current density 20 to 200 mA cm -2 , temperature 20-40℃, time 6-24 h.

2. The method for preparing a transition metal-doped nickel oxyhydroxide catalyst according to claim 1, characterized in that: The first metal salt is nickel nitrate, the second metal salt is iron nitrate, and the third metal salt is cobalt nitrate and chromium nitrate.

3. The method for preparing the transition metal-doped nickel oxyhydroxide catalyst according to claim 1, characterized in that: In the mixed metal salt solution, the molar concentration of the first metal salt is 15-20 mM.

4. The method for preparing a transition metal-doped nickel oxyhydroxide catalyst according to claim 1, characterized in that: The conductive substrate includes carbon paper, carbon cloth or nickel foam.

5. The method for preparing the transition metal-doped nickel oxyhydroxide catalyst according to claim 1, characterized in that: In step (1), the conditions for electrodeposition using the constant voltage method are: voltage -1 to -0.9 V, temperature 20 to 30°C, and time 50 to 70 min; the conditions for electrodeposition using the constant current method are -5 to -10 mA, temperature 20 to 30°C, and time 50 to 70 min.

6. The method for preparing a transition metal-doped nickel oxyhydroxide catalyst according to claim 1, characterized in that: The concentration of potassium hydroxide or sodium hydroxide in the alkaline solution is 0.1-3 M.

7. A transition metal-doped nickel oxyhydroxide catalyst prepared according to the method for preparing a transition metal-doped nickel oxyhydroxide catalyst according to any one of claims 1 to 6.

8. Use of the transition metal-doped nickel oxyhydroxide catalyst according to claim 7 in hydrogen production by seawater electrolysis.

9. A method for producing hydrogen by electrolysis of seawater, characterized in that: The transition metal-doped nickel oxyhydroxide catalyst according to claim 7 is used.

Images