Vulcanized foamed nickel loaded cobalt manganese oxide heterostructure electrocatalyst as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electro-catalysis, and relates to a vulcanized foamed nickel loaded cobalt manganese oxide heterostructure electro-catalyst as well as a preparation method and application thereof. The preparation process comprises three steps of hydrothermal reaction, a manganese-based / cobalt-based oxide heterostructure is constructed and combined with a vulcanized foamed nickel substrate, and the electrode material for electro-catalytic water decomposition is prepared. According to the prepared electrocatalyst, the foamed nickel with the large specific surface area serves as a carrier, the intrinsic catalytic activity of the material is remarkably improved through the interface coupling effect of the composite material, and therefore the overall electrocatalytic performance is synergistically enhanced. An electrochemical test shows that the cobalt manganese oxide heterostructure electrocatalyst loaded by the sulfurized foamed nickel prepared by the invention shows obvious catalytic activity in electrocatalytic hydrogen evolution and oxygen evolution reaction, and has a good application prospect. The preparation method is simple and convenient to operate, mild in reaction condition, low in raw material cost and easy to realize large-scale preparation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalysis, and relates to a sulfided foam nickel loaded cobalt-manganese oxide heterostructure electrocatalyst as well as a preparation method and application thereof. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general background of the application and does not necessarily constitute an admission or a recognition that the information forms part of the prior art that is already known in any country in the world.

[0003] Hydrogen fuel is regarded as an ideal substitute for traditional fossil energy due to its advantages of renewability, cleanness, resource abundance and high heat value. High-purity hydrogen is prepared by efficient electrolysis of water using renewable energy, which is an ideal path to realize sustainable supply of hydrogen source for fuel cells. The water electrolysis process includes two half-reactions of anode oxygen evolution reaction (OER) and cathode hydrogen evolution reaction (HER), both of which have problems of high overpotential, slow kinetics and high energy barrier, which limit the energy conversion efficiency. Even if noble metal catalysts such as RuO2 (OER) and Pt (HER) are used, the above-mentioned bottlenecks are still difficult to avoid, so the development of high-efficiency electrocatalysts to significantly reduce the reaction overpotential is the core goal to improve the performance of HER and OER.

[0004] Therefore, a non-noble metal bifunctional catalyst system with low cost, high activity and long service life is the focus of current research. Studies have shown that transition metal oxides have become a research hotspot in the field of electrocatalysts in recent years due to their multifunctionality, excellent stability and low cost advantages. However, according to the inventors' research, due to the poor intrinsic conductivity and low active site exposure rate, it is still necessary to modify the transition metal oxides to support the efficient operation of the material under high current density conditions. SUMMARY

[0005] In order to solve the problems of the prior art, the application provides a sulfided foam nickel loaded cobalt-manganese oxide heterostructure electrocatalyst and a preparation method and application thereof. The electrocatalyst takes foam nickel with a large specific surface area as a carrier, and the interface coupling effect of the composite material significantly improves the intrinsic catalytic activity of the material, thereby synergistically enhancing the overall electrocatalytic performance. Electrochemical tests show that the sulfided foam nickel loaded cobalt-manganese oxide heterostructure electrocatalyst prepared by the application has obvious catalytic activity in OER and HER, and has good application prospect. The preparation method is simple in operation, mild in reaction condition, low in raw material cost, and easy to realize large-scale preparation.

[0006] In order to achieve the above-mentioned purpose, the application provides the following technical solutions: In a first aspect, the present application provides a preparation method of a sulfide foam nickel loaded cobalt-manganese oxide heterostructure electrocatalyst. The preparation process comprises three hydrothermal reactions. By constructing a manganese-based / cobalt-based oxide heterostructure and combining with a sulfide foam nickel substrate, an electrode material for electrocatalytic water splitting is prepared, and the specific process is as follows: First hydrothermal reaction: In a water solution composed of a sulfur source and urea, a thin layer of nickel(II) sulfide nanosheet is grown in situ on the surface of the foam nickel through a hydrothermal reaction; Second hydrothermal reaction: Then, the sulfided foam nickel is soaked in a solution composed of a cobalt salt, urea and ammonium fluoride, and a cobalt hydroxide is generated under hydrothermal conditions, thereby obtaining a cobalt hydroxide grown in situ on the sulfide foam nickel; Third hydrothermal reaction: Finally, the sulfide foam nickel with the grown cobalt hydroxide is reacted with potassium permanganate and polyvinylpyrrolidone through a hydrothermal reaction to synthesize a sulfide foam nickel loaded cobalt-manganese oxide Co3O4@MnO2 / Ni3S2 / NF; The foam nickel as an active substrate has an inherent rich pore structure, which significantly increases the specific surface area of the material and improves the electrical conductivity. The electronic coupling effect between the components of Co3O4@MnO2 / Ni3S2 optimizes the charge transport kinetics, the heterojunction interface engineering effectively adjusts the electronic structure of the catalyst, adjusts the adsorption / desorption energy of the intermediate product, and synergistically enhances the electrical conductivity of the material.

[0007] As a further technical solution, the conditions of the "first hydrothermal reaction" are 110-140°C, and the reaction time is 10-15h.

[0008] As a further technical solution, the concentration of the sulfur source is 8-40mmol / L, and preferably 15-20mmol / L.

[0009] As a further technical solution, the molar ratio of the sulfur source to urea is 0.6-2:2-4, and preferably 1:3.

[0010] As a further technical solution, the conditions of the "second hydrothermal reaction" are 110-130°C, and the reaction time is 10-14h.

[0011] As a further technical solution, the concentration of the cobalt element is 14-40mmol / L, and preferably 15-20mmol / L.

[0012] As a further technical solution, the molar ratio of the cobalt element to urea to ammonium fluoride is 0.5-1.5:2.5-7:1.8-5.5, and preferably 1:3-5:2-4.

[0013] As a further technical solution, the conditions of the "third hydrothermal reaction" are 150-170°C, and the reaction time is 2-6h.

[0014] As a further technical solution, the concentration of potassium permanganate is 12-35 mmol / L, preferably 17 mmol / L.

[0015] As a further technical solution, the addition amount of polyvinylpyrrolidone is 100-300 mg, preferably 150 mg.

[0016] As a further technical solution, the pretreatment process of the foamed nickel is: cutting 4-12 cm 2 The foamed nickel is sequentially ultrasonically treated with acetone, 0.5-3 mol / L hydrochloric acid solution and deionized water for 10-30 min, and vacuum dried at 30-60°C. Specifically, the concentration of the hydrochloric acid solution is preferably 1-2 mol / L. Specifically, the thickness of the foamed nickel is 1-2 mm.

[0017] On the other hand, the present application also provides a sulfided foamed nickel loaded cobalt-manganese oxide heterostructure electrocatalyst obtained by the above preparation method.

[0018] In a third aspect, the present application also provides a use of the above sulfided foamed nickel loaded cobalt-manganese oxide heterostructure electrocatalyst in the electrocatalytic decomposition of water to produce hydrogen.

[0019] The beneficial effects of the present application are: 1、The sulfided foamed nickel loaded cobalt-manganese oxide heterostructure electrocatalyst in the present application uses foamed nickel as the substrate and is prepared by a simple three-step hydrothermal reaction process. The prepared sulfided nickel(II) composite cobalt-manganese oxide heterostructure has a rich porous structure and high-density active sites, and can be used as a high-efficiency bifunctional electrocatalyst to simultaneously improve the OER and HER performance. The preparation method has a simple process, mild and controllable reaction conditions, and has significant potential for industrial application.

[0020] 2、The sulfided nickel(II) composite cobalt-manganese oxide heterostructure electrocatalyst prepared in the present application is in-situ grown on foamed nickel with a rich three-dimensional pore structure, avoiding the use of traditional adhesives, which not only reduces costs but also exposes more active sites. Moreover, the sulfidation of foamed nickel can directly form a nickel sulfide layer on its surface with intrinsic HER and OER catalytic activity, without the need to introduce additional nickel sources. This process realizes the roughening of the foamed nickel surface, providing more anchor points for the subsequent loading of active materials.

[0021] 3、The formation of the high-conductivity Co3O4@MnO2 / Ni3S2 heterostructure on the surface of foamed nickel in the present application benefits from effective size and morphology control. The synergistic effect of Ni3S2, Co3O4 and MnO2 components at the heterojunction interface significantly enhances the efficiency of electron transfer and mass transfer, thereby improving the intrinsic activity of the material and exhibiting obvious catalytic potential.

[0022] 4. The present invention uses a cobalt-manganese oxide heterostructure electrocatalyst supported by sulfided nickel foam for OER and HER. In a 1 mol / L potassium hydroxide alkaline solution, only 125 mV (vs. reversible hydrogen electrode) is required to achieve a characteristic current density of 10 mA cm in the HER test. -2 In the OER test, the current density was 10 mA cm -2 The overpotential is 248 mV (relative to the reversible hydrogen electrode). BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1 This is the XRD spectrum of the Co3O4@MnO2 / Ni3S2 / NF composite nanomaterial prepared in Example 1 of the present invention; Figure 2 SEM images of the Co3O4@MnO2 / Ni3S2 / NF composite nanomaterial prepared in Example 1 of the present invention; wherein, Figure a shows a SEM image of a scanning electron microscope at 30 μm; Figure b shows a SEM image of a scanning electron microscope at 5 μm; and Figure c shows a SEM image of a scanning electron microscope at 500 nm; Figure 3 (a) TEM image, (b) TEM image and (c) HRTEM image of the Co3O4@MnO2 / Ni3S2 / NF composite nanomaterial prepared in Example 1 of the present invention; Figure 4 (a) Low-magnification SEM image and (b) high-magnification SEM image of the Co3O4@MnO2 / Ni3S2 / NF composite nanomaterial prepared in Example 2 of the present invention; Figure 5 (a) Low-magnification SEM image and (b) high-magnification SEM image of the Co3O4@MnO2 / Ni3S2 / NF composite nanomaterial prepared in Example 3 of the present invention; Figure 6 (a) Linear sweep voltammetry (LSV) curve and (b) Tafel slope plot of the sample prepared in the present invention when subjected to HER test in 1 mol / L potassium hydroxide solution; Figure 7 This is a chronoamperometry diagram of the HER test of the Co3O4@MnO2 / Ni3S2 / NF composite material prepared in Example 1 of the present invention.

[0025] Figure 8(a) Linear sweep voltammetry (LSV) and (b) Tafel slope plot of the sample prepared in the present application when subjected to OER test in 1 mol / L potassium hydroxide solution; Figure 9 Chronoamperogram of the Co3O4@MnO2 / Ni3S2 / NF composite material prepared in Example 1 of the present application when subjected to OER test. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed description is exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0027] It is also important to note that the terms used herein are not intended to limit the exemplary embodiments to the specific embodiments which are described in detail. Rather, it is contemplated that the terms are intended to also include any equivalents or alternatives of the specific embodiments described herein. As used herein, unless the context clearly dictates otherwise, the use of the singular form includes the plural. Furthermore, it is to be understood that the use of the term "including", "comprising", or "having" contains the term "consisting of" and the like, unless the context clearly dictates otherwise.

[0028] The hydrothermal reaction and the hydrothermal condition of the present application is a method of heating the reaction system to generate high pressure in a closed system using water as a solvent.

[0029] In view of the fact that there is no electrocatalyst with excellent OER and HER performance at present, the application provides a sulfidized foam nickel loaded cobalt-manganese oxide heterostructure electrocatalyst and a preparation method and application thereof. In order to inhibit the agglomeration phenomenon in the material preparation process and enhance the electrical conductivity, the application adopts high specific surface area foam nickel as a carrier to in-situ grow the catalyst. The strategy can simultaneously improve the electronic transmission rate and mechanical strength of the material, thereby promoting the electrocatalytic reaction process. By pre-sulfidizing the foam nickel carrier, the catalyst loading can be further increased and the electrical conductivity can be improved; however, the sulfidization conditions need to be optimized to avoid mechanical performance degradation. Therefore, there are still great challenges in developing a low-cost water electrolysis catalyst with high intrinsic activity, simple preparation process and mild reaction conditions. In a typical embodiment of the application, a preparation method of a sulfidized foam nickel loaded cobalt-manganese oxide heterostructure electrocatalyst is provided, which comprises the following steps: in a first hydrothermal reaction, a thin layer of sulfidized nickel(II) nanosheet is in-situ grown on the surface of the foam nickel by a hydrothermal reaction of a sulfur source and urea; in a second hydrothermal reaction, the sulfidized foam nickel is soaked in a solution composed of a cobalt salt, urea and ammonium fluoride to generate cobalt hydroxide under hydrothermal conditions, so as to obtain cobalt hydroxide in-situ grown on the sulfidized foam nickel; and in a third hydrothermal reaction, the sulfidized foam nickel with the grown cobalt hydroxide is used to synthesize sulfidized foam nickel loaded cobalt-manganese oxide Co3O4@MnO2 / Ni3S2 / NF by a hydrothermal reaction of the sulfidized foam nickel, potassium permanganate and polyvinylpyrrolidone.

[0030] The cobalt salt in the application refers to a compound with cobalt ions as cations, such as cobalt chloride, cobalt sulfate and cobalt nitrate.

[0031] The sulfur source in the application refers to a compound capable of sulfidizing a metal into a metal sulfide, such as thioacetamide and thiourea.

[0032] In some embodiments, the conditions of the "first hydrothermal reaction" are 110-140°C and the reaction time is 10-15h, so as to ensure complete sulfidization and prevent the mechanical performance of the foam nickel from being damaged by high temperature.

[0033] In some embodiments, the concentration of the sulfur source is 8-40mmol / L, preferably 15-20mmol / L.

[0034] In some embodiments, the molar ratio of the sulfur source to urea is 0.6-2:2-4, preferably 1:3.

[0035] In some embodiments, the conditions of the "second hydrothermal reaction" are 110-130°C and the reaction time is 10-14h. The reaction conditions can ensure that the material is successfully precipitated and grown on the sulfidized foam nickel.

[0036] In some embodiments, the concentration of cobalt element is 14-40mmol / L, preferably 15-20mmol / L.

[0037] In some embodiments, the molar ratio of cobalt element, urea and ammonium fluoride is 0.5-1.5: 2.5-7: 1.8-5.5, preferably 1: 3-5: 2-4, under which the cobalt hydroxide generated has uniform morphology and reasonable size.

[0038] In some embodiments, the conditions of the “third hydrothermal reaction” are 150-170°C, and the reaction is performed for 2-6h. Potassium permanganate can be successfully converted into manganese dioxide under high temperature environment.

[0039] In some embodiments, the concentration of potassium permanganate is 12-35mmol / L, preferably 17mmol / L.

[0040] In some embodiments, the amount of polyvinylpyrrolidone added is 100-300mg, preferably 150mg. The addition of polyvinylpyrrolidone helps the dispersion of the product.

[0041] The foam nickel is pretreated before use. In some embodiments, the pretreatment process of the foam nickel is: cutting 4-12cm 2 The foam nickel is sequentially ultrasonically treated in acetone, 0.5-3mol / L hydrochloric acid solution and deionized water for 10-30min, and vacuum dried at 30-60°C. Specifically, the concentration of the hydrochloric acid solution is preferably 1-2mol / L. Specifically, the thickness of the foam nickel is 1-2mm.

[0042] In some embodiments, the specific steps are as follows: (1) Growing nickel(II) sulfide nanosheets in situ on the surface of pretreated foam nickel by hydrothermal reaction: dissolving sulfur source and urea in deionized water, and magnetically stirring for 20-40min until the solid is completely dissolved; transferring the mixed solution and pretreated foam nickel into a Teflon-lined stainless steel autoclave, and reacting at 110-140°C for 10-15h; after the reaction is completed, the product is cooled, washed and dried to obtain foam nickel wrapped with nickel(II) sulfide nanosheets (Ni3S2 / NF); the amounts of the sulfur source, urea and deionized water are 45-150mg, 120-240mg and 50-70mL, respectively; (2) Synthesizing the cobalt hydroxide nanoneedle precursor in-situ grown on the sulfidized nickel foam by hydrothermal reaction of the Ni3S2 / NF prepared in step (1): dissolving the cobalt nitrate hexahydrate, urea and ammonium fluoride in deionized water, stirring for 20-40 min, transferring the Ni3S2 / NF and the mixed solution into a reaction kettle, heating the reaction kettle to 110-130°C, after 10-14 h of reaction, cooling, washing and drying the reaction product to obtain the cobalt hydroxide nanoneedle precursor in-situ grown on the sulfidized nickel foam, denoted as Co(OH)2 / Ni3S2 / NF; the amounts of the cobalt nitrate hexahydrate, urea, ammonium fluoride and deionized water are 140-400 mg, 150-400 mg, 70-200 mg and 50-70 mL respectively.

[0043] (3) Synthesizing the cobalt-manganese oxide Co3O4@MnO2 / Ni3S2 / NF supported on the sulfidized nickel foam by hydrothermal reaction of the Co(OH)2 / Ni3S2 / NF composite material prepared in step (2): dissolving the potassium permanganate and polyvinylpyrrolidone in deionized water, stirring for 20-40 min, transferring the Co(OH)2 / Ni3S2 / NF and the mixed solution into a reaction kettle, heating the reaction kettle to 150-170°C, after 2-6 h of reaction, cooling, washing and drying the reaction product to obtain the cobalt-manganese oxide nanostructure supported on the sulfidized nickel foam, denoted as Co3O4@MnO2 / Ni3S2 / NF; the amounts of the potassium permanganate, polyvinylpyrrolidone and deionized water are 120-320 mg, 100-300 mg and 50-70 mL respectively.

[0044] Specifically, the reaction product treatment method of the reaction kettle in the steps (1)-(3) is as follows: after the reaction kettle is cooled, the reaction product is repeatedly cleaned with anhydrous ethanol and deionized water in sequence, and vacuum dried at 30-50°C.

[0045] In another embodiment of the present application, a sulfidized nickel foam supported cobalt-manganese oxide heterostructure electrocatalyst is provided, which is obtained by the above preparation method.

[0046] In a third aspect, the above sulfidized nickel foam supported cobalt-manganese oxide heterostructure electrocatalyst is applied to the electrocatalytic decomposition of water to produce hydrogen.

[0047] In order to enable those skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples and comparative examples.

[0048] Example 1 The present embodiment provides a preparation method of a sulfidized nickel foam supported cobalt-manganese oxide heterostructure electrocatalyst, which specifically comprises the following steps: (1) Pretreating the nickel foam: cutting a nickel foam with a size of 2x3 cm2 The nickel foam (thickness of 1 mm) was ultrasonically cleaned with acetone, 1 mol / L hydrochloric acid and deionized water for 10 min, 10 min and 20 min respectively to remove oil and oxides on the surface of the nickel foam. The treated nickel foam was vacuum dried at 40 °C for later use.

[0049] (2) 60 mL of deionized water was measured and placed in a beaker. 75 mg of thioacetamide and 180 mg of urea were added in sequence. The mixture was stirred under magnetic stirring for 30 min until the solid was completely dissolved. The molar ratio of thioacetamide to urea was 1:3. The mixed solution and the pretreated nickel foam were transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted at 120°C for 12 h. After the reaction was completed, the autoclave was cooled and the reaction product was repeatedly washed with anhydrous ethanol and deionized water in sequence. The product was vacuum dried at 40°C to obtain nickel foam coated with nickel (II) sulfide nanosheets.

[0050] (3) Measure 60 mL of deionized water in a beaker, add 291 mg of cobalt nitrate hexahydrate, 240 mg of urea and 111 mg of ammonium fluoride in sequence, and stir magnetically for 30 min until the solid is completely dissolved. The molar ratio of cobalt nitrate hexahydrate, urea and ammonium fluoride is 1:4:3. The mixed solution and the nickel foam loaded with nickel sulfide (II) nanosheets are transferred to a 100 mL Teflon-lined stainless steel autoclave and reacted at 120 ° C for 10 h. After the reaction is completed, the reactor is cooled and the reaction product is repeatedly washed with anhydrous ethanol and deionized water in sequence. It is vacuum dried at 40 ° C to obtain the cobalt hydroxide nanoneedle precursor Co(OH)2 / Ni3S2 / NF grown in situ on nickel sulfide foam.

[0051] (4) 60 mL of deionized water was measured and placed in a beaker. 158 mg of potassium permanganate and 150 mg of polyvinylpyrrolidone were added in sequence. The mixture was stirred magnetically for 30 min until the solid was completely dissolved. The Co(OH)2 / Ni3S2 / NF and the mixed solution were transferred to a 100 mL Teflon-lined stainless steel autoclave. The autoclave was heated to 160°C and reacted for 3 h. After the autoclave was cooled, the reaction product was repeatedly washed with anhydrous ethanol and deionized water, and vacuum dried at 40°C to obtain a sulfide nickel foam-supported cobalt manganese oxide nanostructure, which was designated as Co3O4@MnO2 / Ni3S2 / NF.

[0052] The structure of Co3O4@MnO2 / Ni3S2 / NF prepared in Example 1 was characterized by X-ray diffraction (XRD). Figure 1 As shown, the XRD analysis results confirmed the presence of three-phase substances of Co3O4, MnO2 and Ni3S2 in the composite material prepared in Example 1, which provided more reaction active centers, confirming the successful synthesis of Co3O4@MnO2 / Ni3S2 heterostructure material.

[0053] The morphology of the composite material was further observed by scanning electron microscopy (SEM), as shown in FIG. a of Figure 2 FIG. a of Figure 2 FIG. b and c of

[0054] As shown in the low-magnification TEM image of FIG. a of Figure 3 The image clearly shows the needle-like structure of the catalyst on the Co3O4@MnO2 / Ni3S2 / NF, which is consistent with the SEM morphology described above. Figure 3 FIG. b further shows that the surface of the nanoneedle is densely grown with nanoparticles. This secondary structure helps to expand the electrochemically active area of the electrode and provides more catalytically active sites. Figure 3 The HRTEM image of FIG. c reveals the interface relationship between Co3O4 and MnO2. The 0.27 nm lattice spacing corresponds to the (220) crystal plane of Co3O4, while the 0.48 nm lattice fringe belongs to the (200) crystal plane of MnO2. The above results show that Co3O4 and MnO2 form a close heterostructure.

[0055] Example 2 The present example provides a preparation method of a sulfided nickel foam supported cobalt-manganese oxide heterostructure electrocatalyst, specifically comprising the following steps: In the present example, the amount of thioacetamide in step (2) of Example 1 is changed to 100 mg, and the amount of cobalt nitrate hexahydrate in step (4) is changed to 400 mg. The other steps and the amounts of reactants are exactly the same as in Example 1.

[0056] As shown in the SEM image of FIG. a of Figure 4 The morphology of the material prepared in Example 2 is observed, and the composite material on the nickel foam is a regularly arranged nanoneedle with nanoparticles uniformly grown on the surface, and the edges are clear.

[0057] Example 3 The present example provides a preparation method of a sulfided nickel foam supported cobalt-manganese oxide heterostructure electrocatalyst, specifically comprising the following steps: In the present example, the amount of potassium permanganate in step (4) of Example 1 is changed to 316 mg, and the reaction temperature of the reaction kettle is changed to 150°C. The other steps and the amounts of reactants are exactly the same as in Example 1.

[0058] The morphology of the material prepared in Example 3 is observed by SEM, as shown in FIG. a of Figure 5As shown in the SEM electron microscope image, the morphology of the composite material on the nickel foam is intersecting nanoneedles with nanoparticles aggregated on the surface.

[0059] Comparative Example 1 This comparative example provides a method for preparing a nickel (II) sulfide nanosheet-wrapped foam nickel electrocatalyst, which specifically comprises the following steps: The reaction steps and the amounts of reactants used were exactly the same as those in steps (1) to (2) in Example 1, excluding steps (3) to (4) in Example 1, to obtain a nickel foam electrocatalyst wrapped with nickel (II) sulfide nanosheets, denoted as Ni3S2 / NF.

[0060] Comparative Example 2 This comparative example provides a method for preparing a cobalt hydroxide nanoneedle electrocatalyst grown in situ on sulfided nickel foam, which specifically comprises the following steps: The reaction steps and the amounts of reactants used are exactly the same as those in steps (1) to (3) in Example 1, excluding step (4) of Example 1. The obtained cobalt hydroxide nanoneedles in situ grown on sulfide nickel foam are denoted as Co(OH)2 / Ni3S2 / NF.

[0061] Comparative Example 3 This comparative example provides a method for preparing a cobalt-manganese oxide electrocatalyst grown in situ on nickel foam, which specifically comprises the following steps: The reaction steps and the amounts of reactants used are exactly the same as those of steps (1), (3) and (4) in Example 1, excluding step (2) of Example 1. The obtained cobalt manganese oxide in situ grown on nickel foam is denoted as Co3O4@MnO2 / NF.

[0062] Application Examples The OER and HER performance of Example 1 and Comparative Examples 1-3 were tested using an electrocatalytic testing system. A standard three-electrode system was used, with Example 1 and Comparative Examples 1-3 prepared according to the present invention serving as the working electrode, a mercury / mercuric oxide electrode serving as the reference electrode, a carbon rod serving as the counter electrode for OER and HER testing, and a 1 mol / L potassium hydroxide solution serving as the electrolyte. Prior to the HER test, the electrolyte was pre-purged with nitrogen for 30 minutes; prior to the OER test, the electrolyte was pre-purged with oxygen for 30 minutes. The OER and HER activities of Example 1 and Comparative Examples 1-3 prepared according to the present invention were tested using LSV, with a scan rate of 5 mV / s.

[0063] The OER performance of each material was tested in 1 mol / L potassium hydroxide solution using Example 1 and Comparative Examples 1-3 as working electrodes. The results of the LSV test were Figure 6 (a) shows that the Co3O4@MnO2 / Ni3S2 / NF composite material prepared in Example 1 has a current density of 10 mA cm -2overpotential of 248 mV (vs. reversible hydrogen electrode), lower than Comparative Examples 1-3, proving that the Co3O4@MnO2 / Ni3S2 / NF composite material has the optimal OER performance compared with other prepared catalysts. Comparing the Tafel slopes of various materials, as shown in Figs. Figure 6 (b), the Tafel slope of Co3O4@MnO2 / Ni3S2 / NF (57.7 mV dec -1 ) is lower, indicating that the kinetics of Co3O4@MnO2 / Ni3S2 / NF is good compared with other comparative examples.

[0064] Considering that catalytic stability is another key indicator for evaluating the practicality of a catalyst, the present application conducted a constant potential stability test on Example 1 in 1 mol / L potassium hydroxide electrolyte. The OER was continuously carried out at a constant voltage of 1.6 V (vs. reversible hydrogen electrode) for 72 h, and the current density was stably maintained at about 100 mA cm -2 ( Figure 7 ), and the attenuation amplitude was minimal, fully proving the excellent OER stability of the material.

[0065] Figure 8 The LSV curves of HER of the four materials in the a graph of Fig. 1 show that the Co3O4@MnO2 / Ni3S2 / NF composite material prepared in Example 1 has an overpotential of 125 mV (vs. reversible hydrogen electrode) at a current density of 10 mA cm -2 , lower than Comparative Examples 1-3, proving that the Co3O4@MnO2 / Ni3S2 / NF composite nanomaterial has good HER performance. Comparing the Tafel slopes of various materials, as shown in Figs. Figure 8 (b), the Tafel slope of Co3O4@MnO2 / Ni3S2 / NF is 90.2 mV dec -1 , lower than Comparative Examples 1-3, indicating that Co3O4@MnO2 / Ni3S2 / NF has faster kinetic characteristics.

[0066] In order to further study the HER stability of the above Example 1 in 1 mol / L potassium hydroxide electrolyte, a long-term stability test was carried out at a fixed overpotential of-0.3 V. As shown in Fig. Figure 9 , the Example 1 electrode can be stably maintained at a high current density of 100 mA cm -2 for 57 h, without obvious fluctuations, fully confirming its excellent durability.

[0067] The above test results show that the sulfided nickel foam loaded cobalt manganese oxide heterostructure electrocatalyst prepared by the present application has excellent OER and HER performance, and has a broad application prospect.

[0068] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for preparing a sulfide nickel foam supported cobalt manganese oxide heterostructure electrocatalyst, characterized in that: The following steps are involved: A hydrothermal reaction is performed in which a sulfur source and urea are hydrothermally reacted to in situ grow a thin layer of nickel (II) sulfide nanosheets on the surface of nickel foam. Secondary hydrothermal reaction: The sulfided nickel foam is then immersed in a solution consisting of cobalt salt, urea, and ammonium fluoride to generate cobalt hydroxide under hydrothermal conditions, thereby obtaining cobalt hydroxide grown in situ on the sulfided nickel foam; Three hydrothermal reactions: Finally, the sulfide nickel foam on which cobalt hydroxide was grown was hydrothermally reacted with potassium permanganate and polyvinyl pyrrolidone to synthesize sulfide nickel foam-supported cobalt manganese oxide Co3O4@MnO2 / Ni3S2 / NF.

2. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The conditions for the "primary hydrothermal reaction" are: 110-140°C, reaction time 10-15h; the conditions for the "tertiary hydrothermal reaction" are: 150-170°C, reaction time 2-6h.

3. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The concentration of the sulfur source is 8 to 40 mmol / L, preferably 15 to 20 mmol / L. The molar ratio of the sulfur source to urea is 0.6-2:2-4, preferably 1:

3.

4. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The conditions of the "secondary hydrothermal reaction" are: 110-130°C, reaction time 10-14h.

5. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The concentration of cobalt element is 14-40 mmol / L, preferably 15-20 mmol / L.

6. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The molar ratio of cobalt element, urea and ammonium fluoride is 0.5-1.5: 2.5-7: 1.8-5.5, preferably 1: 3-5: 2-4.

7. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The concentration of potassium permanganate is 12-35 mmol / L, preferably 17 mmol / L; The added amount of polyvinyl pyrrolidone is 100-300 mg, preferably 150 mg.

8. The method for preparing the sulfurized nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 1, wherein: The pretreatment process of nickel foam is as follows: cut 4~12cm 2 The nickel foam is sequentially ultrasonicated with acetone, a 0.5-3 mol / L hydrochloric acid solution, and deionized water for 10-30 minutes each, and then vacuum dried at 30-60°C. Specifically, the concentration of the hydrochloric acid solution is preferably 1-2 mol / L. Specifically, the nickel foam has a thickness of 1-2 mm.

9. A sulfide nickel foam supported cobalt manganese oxide heterostructure electrocatalyst, characterized in that: Obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the sulfide nickel foam supported cobalt manganese oxide heterostructure electrocatalyst according to claim 9 in electrocatalytic water decomposition to produce hydrogen.

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