Electrocatalyst with nitrogen-doped cobalt sulfide heterostructure and preparation method thereof

Abstract

The invention discloses an oxygen evolution reaction electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure and used for direct electrolysis of seawater for hydrogen production and energy storage and a preparation method of the oxygen evolution reaction electrocatalyst. During preparation, foamed nickel is used as a substrate, and a self-supporting cobalt hydroxide nanosheet is formed on the foamed nickel substrate; soaking the foamed nickel loaded with the cobalt hydroxide nanosheet in a sulfide solution to obtain a foamed nickel sheet loaded with cobalt sulfide; and placing the cobalt sulfide-loaded foamed nickel sheet in a plasma-assisted chemical vapor deposition system, and doping with nitrogen plasma to obtain the nitrogen-doped cobalt sulfide heterostructure electrocatalyst. The layered heterostructure in the electrocatalyst has a large specific surface area and high surface loading capacity, and doped nitrogen improves the conductivity of the material; in a seawater electrolysis oxygen evolution system, the overpotential is low, the current density is large, and the excellent oxygen evolution reaction catalytic activity is achieved; in addition, the catalyst has excellent stability and durability in a seawater electrolysis environment.

Description

Technical Field

[0001] The present invention relates to the field of hydrogen production and energy storage by electrolyzing seawater, and particularly to an oxygen evolution reaction electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure for directly electrolyzing seawater and a preparation method thereof. Background Art

[0002] Energy storage, as a core component of modern energy systems, plays a crucial role in balancing energy supply and demand, improving energy utilization efficiency, and enhancing the flexibility and reliability of energy systems. It plays a key role in solving the intermittency and instability problems of renewable energy generation, and also has an important role in power grid peak shaving and frequency modulation, distributed energy management, and as an emergency backup power supply. With the rapid development of renewable energy and the continuous deepening of the energy structure transformation, the demand for energy storage technologies has shown a significant growth trend.

[0003] The hydrogen production and energy storage technology by electrolyzing seawater produces hydrogen by electrolyzing seawater and stores it. Compared with other energy storage technologies, it exhibits many significant advantages: First, it can make full use of the widely distributed seawater resources and combine with green power such as offshore wind power and solar energy to produce green hydrogen; second, the whole process is clean and environmentally friendly, meeting the requirements of sustainable development; third, it has a large energy storage scale and a long duration, capable of meeting large-scale and long-term energy storage needs; fourth, it does not occupy precious land resources and is particularly suitable for building independent energy supply systems in remote areas.

[0004] In recent years, the hydrogen production and energy storage technology by electrolyzing seawater has attracted much attention from the academic and industrial circles due to its great potential. However, at present, this technology still faces some challenges: on the one hand, the kinetics of the anodic oxygen evolution reaction (OER) is slow, resulting in high energy consumption for electrolyzing seawater; on the other hand, the high concentration of chloride ions in seawater not only competes with hydroxide ions but also corrodes the electrode surface, causing catalyst shedding and poisoning, thereby reducing the catalyst performance and increasing the hydrogen production energy consumption. Developing efficient and durable OER catalysts is the key to the application of the hydrogen production and energy storage technology by electrolyzing seawater.

[0005] Currently, in the field of anode electrode catalysts for seawater electrolysis, layered double hydroxides (LDHs) and other non-precious metal catalyst materials with titanium (Ti) as the substrate and nickel foam (Ni Foam) as the substrate have been widely studied.

[0006] Regarding the layered metal hydroxide catalyst, Chinese Patent Document CN 114808014 A (Application No. 202210488353.5) discloses a multi-layer metal hydroxide electrocatalyst. A layer of cobalt hydroxide is deposited on nickel foam by cathodic electrochemical deposition, then a layer of iron hydroxide is deposited, and then another layer of cobalt hydroxide is deposited so that the cobalt hydroxide coats the iron hydroxide. Deposition is carried out alternately in sequence. After washing and natural drying, a multi-layer metal hydroxide electrocatalyst is obtained.

[0007] Compared with traditional powder catalysts, self-supporting nanoarray materials have lower interfacial resistance, larger active surfaces, and excellent stability, and have become advanced catalysts; especially in practical large-scale hydrogen production applications that require high current density, self-supporting catalysts have more advantages than powder catalysts. During the electrolysis process, under the strong impact of the bubbles generated on the electrode surface, the powdered nanomaterials are easily peeled off, resulting in a decrease in catalytic activity. In contrast, there is a strong adhesion between the active substance and the substrate of the self-supporting nanomaterials, ensuring good electronic conductivity and high mechanical stability, which is beneficial for long-term and cyclic use.

[0008] Constructing a 3D porous nanostructure with high porosity and roughness can endow the catalyst with a large surface area and abundant active sites, which is an effective strategy to improve mass transfer, OER activity, and catalytic efficiency. In addition, the Cl⁻ blocking layer on the catalyst surface, especially the protective layer with both catalytic activity and protective function, can effectively inhibit the competitive oxidation and corrosion of Cl⁻, thereby enhancing the catalytic activity, selectivity, and stability of the catalyst.

[0009] Cobalt sulfide, as an electrode material, has better mechanical and thermal stability and rich redox reactions, making its capacitance performance superior to other electrode materials. However, there are some problems in its practical application. For example, only the surface and near-surface parts participate in the redox reaction, and the internal compounds are not fully utilized, resulting in a low utilization rate of the electrode active substance.

[0010] Regarding the self-supporting cobalt sulfide nanomaterial, Chinese Patent Document CN 116676627 A (Application No. 202310696209.5) discloses a preparation method of a nickel foam self-supporting fluorine-doped cobalt sulfide nanoarray. First, an aqueous solution containing a cobalt source is added to a reaction device, the pH of the solution is adjusted, an alkali regulator is added to prepare an alkaline pre-reaction solution, nickel foam is put in, and the reaction is carried out by heating. After the reaction ends, the nickel foam is washed, and a purple cobalt source precursor is collected; then the precursor is placed in a tube furnace and fluorinated under the protection of an inert gas to obtain a gray fluorine-doped precursor; finally, a sulfurization aqueous solution is prepared in the reaction device, the fluorine-doped precursor is put into the reaction device and heated for a certain time, then naturally cooled, washed, and dried to obtain a black nickel foam self-supporting fluorine-doped cobalt sulfide nanoarray. Summary of the Invention

[0011] The technical problem to be solved by the present invention is to provide an electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure and a preparation method thereof, which has a uniform nanoarray structure and excellent oxygen evolution reaction catalytic activity and stability in alkaline seawater.

[0012] The technical solution for achieving the purpose of the present invention is a preparation method of an electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure, comprising the following steps: ① Using nickel foam as a substrate, cobalt hydroxide is electrodeposited on the nickel foam substrate in a three-electrode system to form self-supporting cobalt hydroxide nanosheets on the nickel foam substrate.

[0013] ② The nickel foam loaded with cobalt hydroxide nanosheets obtained in step ① is immersed in a sulfur-containing compound solution to obtain a nickel foam sheet loaded with cobalt sulfide; after taking it out, it is rinsed and dried.

[0014] ③ The nickel foam sheet loaded with cobalt sulfide obtained in step ② is placed in a plasma-assisted chemical vapor deposition system and doped with nitrogen plasma to obtain an electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure.

[0015] In the above step ①, in the three-electrode system, the nickel foam sheet is used as the working electrode, the platinum sheet electrode is used as the counter electrode, and Ag / AgCl is used as the reference electrode; the working electrode, the counter electrode and the reference electrode are placed in a Co salt solution, and the working electrode, the counter electrode and the reference electrode are respectively connected to an electrochemical workstation, and the voltage is set to be -1.0 ± 0.2 V relative to Ag / AgCl, and the deposition is carried out for 300 ± 60 seconds to form self-supporting cobalt hydroxide nanosheets on the nickel foam substrate.

[0016] The Co salt is one of cobalt chloride, cobalt nitrate, cobalt acetate and cobalt sulfate.

[0017] In the above step ②, the sulfur-containing compound is one of sodium sulfide, polysulfide sodium, thiourea and thioacetamide, the concentration of the sulfur-containing compound solution is 0.1 mol / L - 10 mol / L, and the nickel foam loaded with cobalt hydroxide nanosheets is immersed in the sulfur-containing compound solution for 0.5 - 6 h.

[0018] In the above step ③, the nitrogen source is nitrogen, the nitrogen flow rate is 5 - 10 sccm, and the gas pressure is 1 - 50 Pa.

[0019] Further, in the above step ③, the plasma treatment temperature is 10 - 35 °C, the plasma power is 50 - 500 W, and the treatment time is 1 - 30 minutes.

[0020] In the above step ③, the plasma power is 100 - 300 W, and the treatment time is 5 - 15 minutes.

[0021] An electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure prepared by the preparation method described above.

[0022] The electrocatalyst includes a nickel foam substrate and a nitrogen-doped cobalt sulfide heterostructure.

[0023] The microstructure of the catalyst includes uniformly distributed nanoarrays, and a layer of particles is attached outside the nanoarrays.

[0024] The present invention has positive effects: (1) The electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure of the present invention has uniformly distributed nanoarrays, and the uniformly distributed nanoarrays are cobalt sulfide; and a layer of smaller-sized particles is attached outside the nanoarrays, and this layer of particles is nitrogen-doped cobalt sulfide, making the catalyst have a larger surface area and abundant active sites.

[0025] (2) The hierarchical heterostructure in the electrocatalyst of the present invention has a large specific surface area and a high surface loading, and the doped nitrogen improves the conductivity of the material; in the seawater electrolysis oxygen evolution system, the overpotential is lower and the current density is larger, having excellent oxygen evolution reaction catalytic activity.

[0026] (3) The electrocatalyst of the present invention has excellent stability and durability in the seawater electrolysis environment.

[0027] (4) The present invention realizes the construction of a nitrogen-doped cobalt sulfide heterostructure at room temperature by using low-temperature plasma technology, and the energy consumption of the preparation process is low. The present invention uses low-temperature plasma technology to introduce nitrogen atoms to change the electronic structure and charge distribution of the material and improve the performance of the catalyst.

[0028] The preparation method of the present invention is simple, controllable, and easy to realize industrial production, providing a new high-efficiency, stable and low-cost catalyst for seawater electrolysis technology. Description of the Drawings

[0029] Figure 1 SEM image of nickel foam loaded with cobalt sulfide prepared in Example 1.

[0030] Figure 2 SEM image of the electrocatalyst prepared in Example 1.

[0031] Figure 3 TEM image of the electrocatalyst prepared in Example 1.

[0032] Figure 4 EDX Mapping image of the electrocatalyst prepared in Example 1.

[0033] Figure 5 XPS energy spectrum analysis image of the electrocatalyst prepared in Example 1.

[0034] Figure 6 Linear sweep voltammogram curves of the electrocatalyst prepared in Example 1 and the comparative catalyst in seawater containing 1 M KOH.

[0035] Figure 7 Linear sweep voltammogram curve of the electrocatalyst prepared in Example 2 in seawater containing 1 M KOH.

[0036] Figure 8 Stability curve of the electrocatalyst prepared in Example 1 in seawater containing 1 M KOH. Detailed implementation manners

[0037] The following are some of the multiple possible embodiments of the present invention, aiming to provide a basic understanding of the present invention, and not aiming to identify the key or decisive elements of the present invention or limit the scope to be protected. It is easy to understand that according to the technical solution of the present invention, without changing the essence of the present invention, those of ordinary skill in the art can propose other interchangeable implementation manners. Therefore, the following detailed implementation manners are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as all of the present invention or as a limitation or restriction on the technical solution of the present invention.

[0038] The experimental methods used in the embodiments of the present invention are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the embodiments of the present invention can be obtained from commercial channels unless otherwise specified.

[0039] (Example 1) The preparation method of the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure in this embodiment includes the following steps: ① Prepare self-supporting cobalt hydroxide nanosheets.

[0040] The self-supporting cobalt hydroxide nanosheets in this embodiment are obtained by electro-depositing cobalt hydroxide on a nickel foam substrate in a three-electrode system. The specific operation is as follows: Clean the nickel foam sheet to remove the surface oxides and organic substances and dry it. Use the nickel foam sheet as the working electrode, the platinum sheet electrode as the counter electrode, and Ag / AgCl as the reference electrode; place the working electrode, the counter electrode, and the reference electrode in a CoCl 2 solution with a concentration of 8 - 12 mM (10 mM in this embodiment), then connect the working electrode, the counter electrode, and the reference electrode to an electrochemical workstation respectively, set the voltage to -1.0 ± 0.2 V (relative to Ag / AgCl, -1.0 V in this embodiment), and deposit for 300 ± 60 seconds (300 seconds in this embodiment), and self-supporting cobalt hydroxide nanosheets are formed on the nickel foam substrate.

[0041] The cobalt salt is selected from but not limited to cobalt chloride, cobalt sulfate, cobalt acetate, cobalt nitrate, etc. Cobalt chloride is selected in this embodiment.

[0042] ② The nickel foam sheet loaded with cobalt hydroxide nanosheets obtained in step ① is statically immersed in a sulfur-containing compound solution with a concentration of 0.1 - 10.0 mol / L (sodium sulfide with a concentration of 2.0 mol / L in this embodiment) for 0.5 - 6 h (soaked for 3 h in this embodiment) to obtain a nickel foam sheet loaded with cobalt sulfide. Take it out, rinse it successively with deionized water and ethanol, and then dry it in vacuum.

[0043] The sulfur-containing compound is selected from one of sodium sulfide, polysulfide, thiourea, and thioacetamide. Sodium sulfide is selected in this embodiment. ③ The nickel foam sheet loaded with cobalt sulfide obtained in step ② is placed in a plasma-assisted chemical vapor deposition system, and nitrogen plasma is used for doping to obtain an electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure.

[0044] The gas used in the plasma-assisted chemical vapor deposition system is nitrogen, the nitrogen flow rate is 5 sccm, the power of the plasma generator is controlled at 150 W, the plasma treatment ambient temperature is 10 - 35 °C (20 °C in this embodiment), the treatment time is 1 minute, and the gas pressure is 20 Pa.

[0045] The scanning electron microscope (SEM) and transmission electron microscope (TEM) are used to observe the microstructure of the catalyst. Figure 1 SEM image of nickel foam supported cobalt sulfide prepared in step ②, Figure 2 SEM image of the electrocatalyst prepared in this embodiment, Figure 3 TEM image of the electrocatalyst prepared in this embodiment. The EDX Mapping results are shown in Figure 4 and the XPS energy spectrum analysis diagram is shown in Figure 5 .

[0046] From Figure 1 , Figure 2 and Figure 3 it can be seen that the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure in this embodiment has a uniformly distributed nanoarray, and the uniformly distributed nanoarray is cobalt sulfide; and there is a layer of smaller particles attached outside the nanoarray, and this layer of smaller particles is nitrogen-doped cobalt sulfide, making the catalyst have a larger surface area and rich active sites.

[0047] The EDX Mapping results show that the main constituent elements of the material loaded on the nickel foam are Co, N, and S.

[0048] The XPS results also show that the main constituent elements of the material loaded on the nickel foam are Co, N, and S. Among them, Co exists in Co 2+ and Co 3+Sulfur mainly exists in the form of sulfides and sulfates (sulfides are partially oxidized when exposed to air); nitrogen exists in the form of nitrides and nitrates (nitrides are partially oxidized when exposed to air). It shows that the main component of the material is cobalt sulfide. After plasma treatment, nitrogen has been doped into cobalt sulfide, forming nitrogen-doped cobalt sulfide.

[0049] (Example 2) The preparation method of the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure in this example is the same as that in Example 1 for the rest, except that: In step ①, the working electrode, counter electrode, and reference electrode are placed in an 8 mM CoCl 2 solution. The working electrode, counter electrode, and reference electrode are respectively connected to an electrochemical workstation. The voltage is set to -0.8 V relative to Ag / AgCl, and deposition is carried out for 360 seconds to form self-supporting cobalt hydroxide nanosheets on the nickel foam substrate.

[0050] In step ②, the nickel foam sheet loaded with cobalt hydroxide nanosheets is statically soaked in a 4.0 mol / L sodium sulfide solution for 1 h.

[0051] In step ③, the gas used in the plasma-assisted chemical vapor deposition system is nitrogen, the nitrogen flow rate is 10 sccm, the power of the plasma generator is controlled at 150 W, the plasma treatment ambient temperature is 25 °C, the treatment time is 3 minutes, and the gas pressure is 20 Pa.

[0052] (Example 3) The preparation method of the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure in this example is the same as that in Example 1 for the rest, except that: In step ①, the working electrode, counter electrode, and reference electrode are placed in a 12 mM cobalt nitrate solution. The working electrode, counter electrode, and reference electrode are respectively connected to an electrochemical workstation. The voltage is set to -1.2 V relative to Ag / AgCl, and deposition is carried out for 240 seconds to form self-supporting cobalt hydroxide nanosheets on the nickel foam substrate.

[0053] In step ②, the nickel foam sheet loaded with cobalt hydroxide nanosheets is statically soaked in a 1.0 mol / L sodium sulfide solution for 6 h.

[0054] In step ③, the gas used in the plasma-assisted chemical vapor deposition system is nitrogen, the nitrogen flow rate is 8 sccm, the power of the plasma generator is controlled at 250 W, the plasma treatment ambient temperature is 20 °C, the treatment time is 5 minutes, and the gas pressure is 40 Pa.

[0055] (Example 4) The preparation method of the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure in this example is the same as that in Example 1, except that: In step ①, the cobalt salt solution is 10 mM cobalt acetate.

[0056] In step ②, the nickel foam sheet loaded with cobalt hydroxide nanosheets is statically immersed in a 2.0 mol / L thiourea solution for 6 h.

[0057] In step ③, the gas used in the plasma-assisted chemical vapor deposition system is nitrogen, the nitrogen flow rate is 5 sccm, the power of the plasma generator is controlled at 150 W, the temperature of the plasma treatment environment is 20 °C, the treatment time is 10 minutes, and the gas pressure is 5 Pa.

[0058] (Example 5) The preparation method of the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure in this example is the same as that in Example 1, except that: In step ①, the cobalt salt solution is 10 mM cobalt sulfate.

[0059] In step ②, the nickel foam sheet loaded with cobalt hydroxide nanosheets is statically immersed in a 2.0 mol / L thioacetamide solution for 3 h.

[0060] In step ③, the gas used in the plasma-assisted chemical vapor deposition system is nitrogen, the nitrogen flow rate is 5 sccm, the power of the plasma generator is controlled at 150 W, the temperature of the plasma treatment environment is 20 °C, the treatment time is 5 minutes, and the gas pressure is 5 Pa.

[0061] (Application Example 1) Using a three-electrode system, a platinum plate electrode as the counter electrode, Hg / HgO as the reference electrode, and the working electrode is a nickel foam sheet loaded with the test catalyst. In filtered seawater containing 1 M KOH, at a scan rate of 10 mV s -1 linear sweep tests were performed on nickel foam, cobalt sulfide, the nitrogen-doped cobalt sulfide catalyst prepared in this example of the present invention, and commercial IrO 2 catalyst, and the results are shown in Figure 6 and Figure 7 .

[0062] Figure 6 is a comparative diagram of linear sweep voltammograms of the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure prepared in Example 1, nickel foam, cobalt sulfide, and commercial IrO 2 catalyst in seawater containing 1 M KOH.

[0063] Figure 7 is the electrocatalyst with a nitrogen-doped cobalt sulfide heterostructure prepared in Example 2, nickel foam, cobalt sulfide, and commercial IrO2 Comparison diagram of linear sweep voltammograms of the catalyst in seawater containing 1 M KOH.

[0064] From the test results, it can be seen that the catalyst of the present invention has a lower overpotential and a higher current density in the oxygen evolution electrolysis system of seawater, and has relatively excellent catalytic activity for the oxygen evolution reaction.

[0065] (Application Example 2, Stability Experiment) Using a three-electrode system, the nickel foam sheet loaded with the electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure prepared in Example 1 was used as the working electrode, the platinum sheet electrode as the counter electrode, and Hg / HgO as the reference electrode. In filtered seawater containing 1 M KOH, at a current density of 100 mA / cm -2 , the catalyst of Example 1 was subjected to electrolysis testing, and the results are shown in Figure 8 .

[0066] From the test results, it can be seen that the catalyst of the present invention has a durability of up to 140 h during the electrolysis of seawater containing 1 M KOH, showing excellent stability.

[0067] The catalysts of other embodiments also have excellent stability according to the above method.

Claims

1. A method for preparing an oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater, characterized in that The following steps are involved: ① Using nickel foam as a substrate, cobalt hydroxide is electrodeposited on the nickel foam substrate in a three-electrode system to form self-supporting cobalt hydroxide nanosheets on the nickel foam substrate; ② Soaking the nickel foam loaded with cobalt hydroxide nanosheets obtained in step ① in a sulfur-containing compound solution to obtain a nickel foam loaded with cobalt sulfide; taking it out, rinsing and drying it; ③ The cobalt sulfide-loaded nickel foam sheet obtained in step ② is placed in a plasma-assisted chemical vapor deposition system, and is doped with nitrogen plasma to obtain an electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure.

2. The method for preparing the oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 1, characterized in that: In step ①, in a three-electrode system, a nickel foam sheet is used as a working electrode, a platinum sheet electrode is used as a counter electrode, and Ag / AgCl is used as a reference electrode; the working electrode, the counter electrode, and the reference electrode are placed in a Co salt solution, and the working electrode, the counter electrode, and the reference electrode are respectively connected to an electrochemical workstation, and the voltage is set to -1.0 ± 0.2 V relative to Ag / AgCl. The deposition is performed for 300 ± 60 seconds, and self-supporting cobalt hydroxide nanosheets are formed on the nickel foam substrate.

3. The method for preparing the oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 2, characterized in that: The Co salt is one of cobalt chloride, cobalt nitrate, cobalt acetate and cobalt sulfate.

4. The method for preparing the oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 1, characterized in that: In step ②, the sulfur-containing compound is one of sodium sulfide, sodium polysulfide, thiourea and thioacetamide, the concentration of the sulfur-containing compound solution is 0.1 mol / L-10 mol / L, and the nickel foam loaded with cobalt hydroxide nanosheets is immersed in the sulfur-containing compound solution for 0.5-6h.

5. The method for preparing the oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 1, characterized in that: In step ③, the nitrogen source is nitrogen gas, the nitrogen gas flow rate is 5-10 sccm, and the gas pressure is 1-50 Pa.

6. The method for preparing the oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 5, characterized in that: In step ③, the plasma treatment temperature is 10-35°C, the plasma power is 50-500W, and the treatment time is 1-30 minutes.

7. The method for preparing the oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 6, characterized in that: In step ③, the plasma power is 100-300W, and the processing time is 5-15 minutes.

8. An oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater prepared by the preparation method according to any one of claims 1 to 7.

9. The oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 8, characterized in that: It includes a nickel foam substrate and a nitrogen-doped cobalt sulfide heterostructure.

10. The oxygen evolution electrocatalyst having a nitrogen-doped cobalt sulfide heterostructure for direct electrolysis of seawater according to claim 8, characterized in that: The microstructure of the catalyst includes a uniformly distributed nanoarray, with a layer of particles attached to the outside of the nanoarray.

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