A self-supporting catalyst, a preparation method and application thereof

Abstract

The application discloses a self-supporting catalyst and a preparation method and application thereof, and the self-supporting catalyst comprises a foamed nickel substrate and Cu2S particles loaded on the foamed nickel substrate, wherein the Cu2S particles are in a micron flower ball shape; the preparation method comprises the following steps: using a foamed nickel as a working electrode and a reaction substrate by means of an electrochemical three-electrode system, and according to the redox potential of copper, reduction of copper ions and sulfurization of copper are sequentially carried out by means of a constant potential method and a cyclic voltammetry method respectively, so that the self-supporting catalyst is obtained. The self-supporting material Cu2S@NF exhibits excellent catalytic activity and stability in HER and OER as a bifunctional electrocatalyst, has great advantages compared with other non-noble metal electrocatalysts, and has a good application prospect in water electrolysis.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of catalysts, in particular, to a self-supporting catalyst, and more particularly, to a self-supporting catalyst, a preparation method and application thereof. BACKGROUND

[0002] The development of modern economy promotes the increasing demand for energy, and thus the problems of fossil energy depletion and environmental pollution are increasingly serious. Developing sustainable clean energy is an important means to alleviate the energy crisis and environmental problems caused by the large-scale use of primary energy such as coal, oil and natural gas. Hydrogen has the characteristics of high energy density (120-140 MJ / kg), low production cost and no pollution, and is one of the most promising clean energies. It is also an ideal way to obtain energy in the future. However, the development of technologies for obtaining hydrogen fuel faces many difficulties.

[0003] Electrocatalytic overall water splitting is a green and efficient method for large-scale production of hydrogen. The system consists of two half-reactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The overpotential driving HER is usually less than 100 mV, while OER requires a higher overpotential (> 300 mV). Currently, Pt metal and Ir / RuO x are the benchmark electrocatalysts for HER and OER, respectively. However, the practical application of benchmark electrocatalysts in electrolytic cells has the problem of mismatched working conditions, and traditional noble metal electrocatalytic materials also have the disadvantages of high cost, low reserves and non-renewable. In order to solve the above problems, it is crucial to develop a bifunctional electrocatalyst with low proportion of noble metals or non-noble metals for HER and OER in the same electrolyte.

[0004] Transition metal sulfides have the advantages of good electronic conductivity, low cost, adjustable composition and high electrocatalytic activity, and have great development potential in the fields of fuel cells, solar cells, biosensors and supercapacitors. In addition, they are abundant in resources and low in price, mainly in the form of ore in nature. Common transition metal sulfide ores include pyrite, sphalerite and chalcocite, accounting for about 1.5% of sulfur in the earth's crust. However, the electrocatalytic performance of common transition metal sulfides is not ideal, mainly because their specific surface area is not large enough and the active sites are not rich enough. Therefore, research and development of transition metal sulfide electrocatalytic materials with special structures are a hot research field. SUMMARY

[0005] In order to overcome the problems in the prior art, the present application discloses a self-supporting catalyst and a preparation method and application thereof, specifically, Cu2S is selected as the research object, and a two-step electrochemical synthesis method is adopted to in-situ grow micro-flower ball Cu2S particles on a foam nickel substrate, the three-dimensional open nano structure of the foam nickel is used to improve the number of active sites and the utilization rate of active substances, a Cu2S@NF self-supporting electrode is obtained, and is used for electrocatalytic overall water splitting. The present application solves the problems of high price and low reserves of traditional electrocatalysts, and only acts on a single reaction, and a low-cost bifunctional electrocatalyst with high catalytic efficiency is obtained.

[0006] One of the purposes of the present application is to provide a self-supporting catalyst, comprising a foam nickel substrate and Cu2S particles loaded on the foam nickel substrate, wherein the Cu2S particles are in the form of micro-flower balls.

[0007] In the present application, the foam nickel is used as a substrate for in-situ loading of cuprous sulfide by electrochemistry to improve the number of active sites and the utilization rate of active substances due to its excellent electrical conductivity and unique three-dimensional open nano structure. At the same time, the inherent processing performance of the foam nickel is used to reduce the use of additives such as adhesives to avoid their influence on the catalytic activity of the material.

[0008] In a preferred embodiment, the average particle size of the Cu2S particles is 5±3 μm, preferably 5±2 μm.

[0009] The self-supporting catalyst Cu2S@NF is in the form of a micro-scale combined array structure.

[0010] The advantages of the Cu2S@NF self-supporting electrode of the present application are as follows: 1. The preparation method is simple, and does not require special experimental conditions such as high temperature and high pressure, and the electrochemical preparation method has low cost and simple experimental conditions; 2. Since the foam nickel itself has electrical conductivity, and the Cu2S material is in-situ grown on the foam nickel to obtain a self-supporting electrode, no additional additives or conductive agents are needed in actual use, which effectively reduces the influence of the use of additives on the electrocatalytic activity of the material; 3. The Cu2S@NF self-supporting electrode prepared by the present application has a low overpotential in electrocatalytic HER, OER and overall water splitting, and has a great advantage in catalytic performance compared with other transition metal-based electrocatalytic materials.

[0011] The second purpose of the present application is to provide a preparation method of a self-supporting catalyst, preferably for the preparation of the self-supporting catalyst of the first purpose of the present application, comprising: using an electrochemical three-electrode system, taking foam nickel as a working electrode and a reaction substrate, and according to the redox potential of copper, sequentially performing reduction of copper ions and sulfuration of copper by constant potential method and cyclic voltammetry respectively to obtain the self-supporting catalyst.

[0012] In the application, an electrochemical three-electrode system is used, with foamed nickel as the working electrode and reaction substrate, and according to the redox potential of copper, a two-step electrochemical synthesis method (constant potential-cyclic voltammetry method) is used to reduce and sulfide copper ions respectively, so as to realize in-situ deposition of micro-flower ball Cu2S on foamed nickel.

[0013] Specifically, the preparation of the self-supporting catalyst Cu2S@NF in the application is as follows: foamed nickel is used as the working electrode, copper ions are first reduced and deposited on the foamed nickel by the electrochemical constant potential method to construct a Cu@NF skeleton, and then the in-situ sulfidation of copper particles is realized by the cyclic voltammetry method to obtain the self-supporting catalyst.

[0014] In a preferred embodiment, the preparation method comprises:

[0015] Step 1, Cu 2+ Determination of reduction potential: the working electrode foamed nickel, the reference electrode and the counter electrode are immersed in an electrolyte solution containing copper ions by using an electrochemical three-electrode system, and the cyclic voltammetry method is used to scan in the negative voltage range to determine the reduction peak of Cu 2+ is a;

[0016] Step 2, electrochemical preparation of Cu@NF: in the electrochemical system of step 1, the constant potential method is used to perform constant potential treatment at (a±0.2), preferably (a±0.1), to obtain Cu@NF;

[0017] In step 2, electrochemical deposition is performed, and yellow substances are observed to be deposited on the surface of the foamed nickel to obtain Cu@NF;

[0018] Step 3, electrochemical preparation of Cu2S@NF: the Cu@NF obtained in step 2 is used as the working electrode and immersed in an electrolyte solution containing sulfur-containing inorganic substances, and the cyclic voltammetry method is used to scan to obtain the sulfidation potential of Cu as b; the cyclic voltammetry scanning is performed in the potential range of (b±0.5), preferably (b±0.3), to realize the sulfidation treatment of Cu and obtain the self-supporting catalyst Cu2S@NF.

[0019] The surface morphology and catalytic activity of the self-supporting catalyst can be optimized by adjusting the electrochemical parameters to realize efficient catalysis of hydrogen evolution reaction and oxygen evolution reaction in alkaline solution at the same time and exhibit good catalytic stability. The preparation process designed in the application is simple, economical and efficient, the material has excellent catalytic performance, has good application prospect, and can be applied in an electrochemical overall water splitting system.

[0020] In a preferred embodiment, the size of the foamed nickel is (0.5-1.5)×(1-5) cm 2, thickness of (0.25-1.5) mm, preferably size of 1 x 3 cm 2 , thickness of 0.5 mm.

[0021] In a preferred embodiment, the pretreatment of the nickel foam (NF) is performed prior to step 1.

[0022] In a further preferred embodiment, the pretreatment comprises: ultrasonic cleaning the nickel foam in an acid solution, an alcohol solvent (e.g. ethanol) and distilled water, respectively.

[0023] In a still further preferred embodiment, the acid solution is 0.1 M hydrochloric acid; and / or, the distilled water is double distilled water; and / or, the ultrasonic cleaning time is 1-10 min, preferably 3-8 min.

[0024] In a preferred embodiment, in step 1, the electrolyte solution is a neutral solution, preferably a neutral salt solution, such as potassium chloride solution; preferably, the molar concentration of the neutral salt solution is 0.1 M.

[0025] In a further preferred embodiment, in step 1, the copper ions (Cu 2+ ) in the electrolyte solution are derived from a water-soluble copper salt, such as copper chloride; preferably, the molar concentration of the water-soluble copper salt in the electrolyte solution is 5-30 mM, such as 5 mM, 10 mM, 15 mM, 20 mM, 25 mM and 30 mM.

[0026] In a preferred embodiment, in step 1, the reference electrode is selected from one of Ag / AgCl electrode, saturated calomel electrode, Hg / HgO electrode.

[0027] In a preferred embodiment, in step 1, the counter electrode is selected from one of Pt wire, graphite rod.

[0028] In a preferred embodiment, in step 2, the time for potentiostatic treatment is 1800-9000 s, preferably 3600-7200 s, more preferably 5400 s.

[0029] For example, in step 2, the time for potentiostatic treatment is 1800 s, 2700 s, 3600 s, 4500 s, 5400 s, 6300 s, 7200 s, 8100 s or 9000 s.

[0030] In a preferred embodiment, in step 2, the voltage applied is -0.2 V.

[0031] In a preferred embodiment, in step 3, the sulfur-containing inorganic compound is selected from at least one of NaHS, Na2S.

[0032] In a preferred embodiment, in step 3, the electrolyte solution is an alkaline aqueous solution with a molar concentration of 0.1 M.

[0033] In a further preferred embodiment, in step 3, the electrolyte solution is an aqueous sodium hydroxide solution.

[0034] In a preferred embodiment, in step 3, the molar concentration of the sulfur-containing inorganic substance in the electrolyte solution is 1-15 mM, preferably 3-8 mM, for example 1 mM, 2 mM, 3 mM, 5 mM, 7 mM, 9 mM, 12 mM or 15 mM.

[0035] In a preferred embodiment, in step 3, cyclic voltammetry is performed at a potential range of -1.0 to -0.5 V.

[0036] In a preferred embodiment, in step 3, during the sulfidation treatment, cyclic voltammetry is performed for 20-60 cycles, preferably 30-50 cycles.

[0037] In a preferred embodiment, the obtained Cu2S@NF self-supporting catalyst is washed after the sulfidation treatment.

[0038] In the preparation of the self-supporting catalyst, the morphology of Cu2S@NF is controlled by changing the applied potential, reaction time and cyclic voltammetry cycles during the preparation process, thereby optimizing the electrocatalytic activity. As a bifunctional electrocatalyst, the material can simultaneously reduce the overpotential of hydrogen evolution and oxygen evolution reactions, and exhibits good stability, and has good application prospects in water electrolysis.

[0039] Meanwhile, the Cu2S prepared by the two-step electrochemical method has a micron flower ball morphology, and the experiment has high repeatability.

[0040] A third object of the present application is to provide a self-supporting catalyst prepared by the preparation method of the second object of the present application.

[0041] A fourth object of the present application is to provide the use of the self-supporting catalyst of the first object of the present application or the self-supporting catalyst prepared by the preparation method of the second object of the present application in overall water splitting, preferably in alkaline overall water splitting.

[0042] In a preferred embodiment, a three-electrode electrochemical system including a working electrode, a reference electrode and a counter electrode is constructed to perform hydrogen evolution reaction and oxygen evolution reaction, wherein the self-supporting catalyst is used as the working electrode; or, a two-electrode system including a working electrode and a counter electrode is constructed to perform overall water splitting, wherein the self-supporting catalyst is used as the working electrode and the counter electrode.

[0043] In further preferred embodiments, the reference electrode is selected from one of Ag / AgCl electrode, saturated calomel electrode, Hg / HgO electrode; and / or, the counter electrode is selected from one of Pt wire, graphite rod.

[0044] In still further preferred embodiments, the electrolyte solution of the electrochemical three-electrode system and two-electrode system is an alkaline aqueous solution, such as KOH aqueous solution; preferably, the molar concentration of the electrolyte solution is 1M; and / or, the electrolyte solution of the electrochemical two-electrode system is an alkaline aqueous solution, such as KOH aqueous solution; preferably, the molar concentration of the electrolyte solution is 0.1M.

[0045] For example: the prepared Cu2S@NF material is cut to an effective area of 1*1cm 2 As the working electrode, Ag / AgCl and Pt are used as the reference electrode and the counter electrode respectively to construct an electrochemical three-electrode system, and the HER and OER performances thereof are tested in 1M KOH aqueous solution. A two-electrode system is constructed to test the overall water splitting performance thereof, wherein: the optimal overpotential of the self-supporting electrode Cu2S@NF in the HER reaction is 105mV when the current density reaches 10mA / cm 2 The optimal overpotential of the self-supporting electrode Cu2S@NF in the OER reaction is 194mV when the current density reaches 10mA / cm 2 The potential of the self-supporting electrode Cu2S@NF in the two-electrode water splitting system is 1.64V when the current density reaches 10mA / cm 2 The self-supporting electrode Cu2S@NF has good catalytic stability in the water splitting reaction.

[0046] The endpoints of the ranges and any values disclosed in the present disclosure are not limited to the precise values recited as the exact dimensions are not critical to the present disclosure. The endpoints of the ranges and the values are approximations that are intended to be rounded to the nearest significant figure. The ranges and values are to be understood to encompass any and all sub-ranges that fall within the stated ranges, inclusive of the minimum and maximum values of the ranges. For numerical values of a range, any intervening value or values between the stated values that are not expressly indicated in the disclosure are intended to be encompassed. For values that are not numerical, any intervening value or values, for example, between stated values that are not expressly indicated in the disclosure are intended to be encompassed. In this respect, it is to be understood that any numerical range recited in the present disclosure is intended to mean and encompass any and all sub-ranges that fall within the stated range, inclusive of the minimum and maximum values of the range. In the following text, the technical solutions of various embodiments can be combined with each other to obtain new technical solutions in principle, which should also be considered as being specifically disclosed herein.

[0047] Compared with the prior art, the present application has the following beneficial effects:

[0048] (1) One of the features of the present application is to realize the in-situ controllable growth of micro-flower ball Cu2S on the foam nickel substrate by using the electrochemical two-step synthesis method, i.e. constant potential-cyclic voltammetry method, for the first time. Compared with traditional methods such as hydrothermal method, anion exchange method and chemical vapor deposition method, the method has the advantages of simple operation, low cost and environmental friendliness. At the same time, the controllable preparation of the material morphology and size can be realized by changing the electrochemical parameters, and then the application performance is optimized.

[0049] (2) The second feature of the present application is to load active material on the metal foam material as the substrate. The three-dimensional network structure of the foam nickel can effectively improve the specific surface area of the material, increase the number of active sites and the utilization rate of active material. The self-supporting electrode is prepared by using the in-situ growth on the foam nickel by using the electrochemical method, and the additional binder and conductive agent are not needed, which avoids the adverse effects of the additives on the catalytic activity and stability of the material.

[0050] (3) The third feature of the present application is that the self-supporting material Cu2S@NF prepared as a bifunctional electrocatalyst exhibits excellent catalytic activity and stability in HER and OER, has great advantages compared with other non-noble metal electrocatalysts, and has good application prospect in water electrolysis. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 The Cu2S@NF sulfidation potential determination cyclic voltammogram in Example 1 is shown. 2+ The reduction potential determination cyclic voltammogram.

[0052] Figure 2 The Cu2S@NF sulfidation potential determination cyclic voltammogram in Example 1 is shown.

[0053] Figure 3 The X-ray diffraction pattern (XRD) of the self-supporting catalyst Cu2S@NF in Example 1 is shown.

[0054] Figure 4 The energy spectrum analysis (EDS) of the self-supporting catalyst Cu2S@NF in Example 1 is shown.

[0055] Figure 5 The X-ray photoelectron spectroscopy analysis (XPS) of the self-supporting catalyst Cu2S@NF in Example 1 is shown.

[0056] Figure 6 The SEM electron micrograph of Cu@NF in Example 1 is shown.

[0057] Figure 7 The SEM electron micrograph of the self-supporting catalyst Cu2S@NF in Example 1 is shown.

[0058] Figure 8Hydrogen evolution reaction (HER) polarization curves of self-supported catalyst Cu2S@NF of Examples 1-3 measured at an electrochemical workstation are shown.

[0059] Figure 9 Hydrogen evolution reaction (HER) Tafel plots of self-supported catalyst Cu2S@NF of Examples 1-3 measured at an electrochemical workstation are shown.

[0060] Figure 10 Oxygen evolution reaction (OER) polarization curves of self-supported catalyst Cu2S@NF of Examples 1-3 measured at an electrochemical workstation are shown.

[0061] Figure 11 Oxygen evolution reaction (OER) Tafel plots of self-supported catalyst Cu2S@NF of Example 1 measured at an electrochemical workstation are shown.

[0062] Figure 12 Polarization curves of self-supported catalyst Cu2S@NF of Example 1 in a two-electrode electrolysis water system are shown.

[0063] Figure 13 Stability test of self-supported catalyst Cu2S@NF of Example 1 is shown. DETAILED DESCRIPTION

[0064] It is necessary to point out that the following examples are only used to further illustrate the present application and should not be understood as limiting the scope of the present application. Any non-essential improvement and adjustment of the present application made by those skilled in the art according to the content of the present application shall still fall within the protection scope of the present application.

[0065] It is also necessary to point out that each specific technical feature described in the following detailed description can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present application will not describe each possible combination manner.

[0066] Furthermore, any combination of the various different embodiments of the present application can also be made, as long as it does not contradict the idea of the present application, and the technical solution thus formed shall be part of the original disclosure of the present specification and shall also fall within the protection scope of the present application.

[0067] The raw materials used in the examples, if not particularly limited, are disclosed in the prior art, for example, can be directly purchased or prepared according to the preparation method disclosed in the prior art.

[0068]

Example 1

[0069] a) Pretreatment of foam nickel: Take foam nickel with a size of 1 x 3 cm 2The nickel foam was ultrasonically cleaned in 0.1 M hydrochloric acid, ethanol and double-distilled water for 5 min, respectively, to remove the surface oxides and possible adsorbed impurities;

[0070] b) Preparation of electrolyte solution: 60 mL of 0.1 M KCl solution was added into a beaker, and then 0.16 g of anhydrous CuCl2 powder was weighed and added into the beaker, which was stirred at room temperature until clear, to obtain a mixed solution of 0.1 M KCl and 20 mM CuCl2 as an electrolyte solution for copper deposition;

[0071] c) Cu 2+ Determination of reduction potential: In this experiment, an electrochemical three-electrode system was used, with the pretreated nickel foam sheet as the working electrode, an Ag / AgCl electrode and a Pt wire as the reference electrode and the counter electrode, respectively. The above electrodes were completely immersed in the electrolyte solution prepared in b). The electrochemical cyclic voltammetry method was used to scan in the voltage range of -1.2 V-0 V, with a scanning rate of 50 mV / s, as shown in FIG. 2. Figure 1 A reduction peak was observed near -0.2 V, corresponding to the reduction of Cu 2+ in the solution;

[0072] d) Electrochemical preparation of Cu@NF: In the electrochemical system of c), the electrochemical deposition was carried out by using the constant potential method, applying a potential of -0.2 V, and the reaction time was 5400 s. The deposition of yellow substances was observed on the surface of the nickel foam, and Cu@NF was obtained;

[0073] e) Preparation of sulfidation solution: 60 mL of 0.1 M NaOH solution was added into a beaker, and then 0.0168 g of NaHS was weighed and added into the beaker, which was stirred until clear, to obtain a mixed solution of 0.1 M NaOH and 5 mM NaHS for sulfidation of Cu@NF;

[0074] f) Electrochemical preparation of Cu2S@NF: The Cu@NF sheet prepared in c) was used as the working electrode, and the mixed solution prepared in e) was used as the electrolyte solution. The cyclic voltammetry method was used to scan in the range of -1.0 V-0.5 V, as shown in FIG. 4. Figure 2 An oxidation peak appeared near -0.8 V, corresponding to the sulfidation of Cu. The cyclic voltammetry scan was performed in the voltage range of -0.5 V-1.0 V for 40 cycles, to complete the sulfidation process of the sample, and Cu2S@NF was obtained;

[0075] g) The prepared Cu2S@NF was cleaned and stored, to obtain a self-supported catalyst Cu2S@NF.

[0076] As Figure 3As shown, part of the characteristic peaks in the sample are in good agreement with the standard PDF card JCPDS: 04-0850 of Ni, and other characteristic peaks are in good agreement with the standard PDF card JCPDS: 65-2980 of Cu2S, so the sample prepared by the method contains Cu2S.

[0077] Figure 4 and 5 It can be seen that the sample contains Ni, Cu and S elements, which proves that the electrochemical method can realize the deposition of Cu on NF and further sulfuration.

[0078] Figure 6 The SEM image and local magnification image of Cu@NF show that blocky copper particles are uniformly deposited on the nickel foam under the constant potential method, and the adhesion is relatively stable.

[0079] Figure 7 The SEM image and local magnification image of Cu2S@NF show that the blocky Cu particles are sulfided into micron flower ball-like Cu2S after the cyclic voltammetry method, and the particle size is about 5um.

[0080]

Example 2

[0081] The same as Example 1, only changing the number of sulfuration cycles in step f) to 20 cycles, to prepare a self-supporting full water splitting electrocatalyst Cu2S@NF.

[0082]

Example 3

[0083] The same as Example 1, only changing the applied potential in step d) to-0.1V, to prepare a self-supporting full water splitting electrocatalyst Cu2S@NF.

[0084]

Example 4

[0085] The same as Example 1, only changing the applied potential in step d) to-0.3V, to prepare a self-supporting full water splitting electrocatalyst Cu2S@NF.

[0086]

Example 5

[0087] A small piece of the self-supporting full water splitting electrocatalyst Cu2S@NF prepared in Examples 1-4 is cut off as an electrode piece, and the working area is controlled to be 1×1cm 2 The prepared electrode piece is clamped by a clamp electrode and placed in a three-electrode system to carry out OER and HER reactions in 1MKOH solution, and the LSV curve is tested, and the scanning rate is 2mV / s.

[0088] According to the electrode area, the current density is plotted, and the current density at 10mA / cm 2The potential at different times was recorded and the Tafel slope was obtained by linear fitting. The test results are shown in Table 1. Figures 8-11 and Table 1.

[0089] Table 1: Performance test of self-supporting catalyst Cu2S@NF for overall water splitting

[0090]

[0091]

[0092] From the data in the above table, one skilled in the art can see that the present application is superior to most non-noble metal electrocatalysts, and the self-supporting overall water splitting electrocatalyst Cu2S@NF in Example 1 has the best catalytic activity for HER and OER.

[0093] Figure 8 and Figure 9 are the HER polarization curves of the self-supporting catalyst Cu2S@NF, Cu@NF and NF in Example 1, the present application Example 1 has smaller overpotential and smaller Tafel slope at the same current density, indicating that the catalyst prepared in the present application has better performance for catalyzing hydrogen evolution reaction in 1M KOH alkaline solution.

[0094] Figure 10 and 11 are the OER polarization curves of the self-supporting catalyst Cu2S@NF, Cu@NF and NF in Example 1, the present application Example 1 has smaller overpotential, i.e. requires lower voltage, at the same current density, indicating that the catalyst prepared in the present application has better performance for catalyzing oxygen evolution reaction in 1M KOH alkaline solution.

[0095]

Example 6

[0096] A two-electrode water electrolysis system was constructed, the electrolyte solution was 0.1M KOH, and Cu2S@NF material was used for both working electrode and counter electrode, Figure 12 is the polarization curve of the system for water electrolysis, and the current density reaches 10mA / cm 2 at 1.64V.

[0097] The self-supporting overall water splitting electrocatalyst Cu2S@NF prepared in Example 1 was subjected to stability test, and the results are shown in Figure 13 , wherein, after 20h continuous work under the application of constant potential 1.8V, the potential change is not large, indicating that the electrocatalyst prepared in the present application has good stability.

[0098] The present application is described in detail above with reference to specific embodiments and exemplary examples, but these are not to be understood as limiting the present application. It is understood by a person skilled in the art that various equivalent substitutions, modifications or improvements can be made to the technical solutions of the present application and the embodiments thereof without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The scope of protection of the present application is defined by the appended claims.

Claims

1. A self-supporting catalyst comprising a foamed nickel substrate and Cu2S particles supported on the foamed nickel substrate, wherein, The Cu2S particles are micron flower balls, and the average particle size of the Cu2S particles is 5±3 μm; the preparation method of the self-supporting catalyst comprises the following steps: step 1, Cu 2+ Determination of reduction potential: using an electrochemical three-electrode system, the working electrode foam nickel, the reference electrode and the counter electrode are immersed in an electrolyte solution containing copper ions, and the reduction peak of Cu 2+ is determined as a by adopting electrochemical cyclic voltammetry to scan in a negative voltage range; step 2, electrochemical preparation of Cu@NF: in the electrochemical system of step 1, constant potential treatment is carried out by adopting constant potential method with (a±0.2) as the applied potential to obtain Cu@NF; step 3, electrochemical preparation of Cu2S@NF: Cu@NF obtained in step 2 is immersed into an electrolyte solution containing sulfur-containing inorganic matter as the working electrode, and cyclic voltammetry is adopted to scan to obtain the sulfidation potential of Cu as b; cyclic voltammetry scanning is carried out in the voltage range of (b±0.5) to realize the sulfidation treatment of Cu, and the Cu2S@NF self-supporting catalyst is obtained; In step 1, the copper ions in the electrolyte solution are derived from a water-soluble copper salt, and the molar concentration of the water-soluble copper salt in the electrolyte solution is 5-30 mM; in step 3, the molar concentration of the sulfur-containing inorganic substance in the electrolyte solution is 1-15 mM; and in step 3, the cyclic voltammetry scanning is performed for 20-60 cycles during the sulfidation treatment.

2. A preparation method of a self-supporting catalyst, for the preparation of the self-supporting catalyst of claim 1, comprising: Step 1, Cu 2+ Determination of reduction potential: using an electrochemical three-electrode system, the working electrode foam nickel, the reference electrode and the counter electrode are immersed in the electrolyte solution containing copper ions, and the reduction peak of Cu 2+ is determined as a by scanning in the negative voltage range using electrochemical cyclic voltammetry. Step 2, electrochemical preparation of Cu@NF: in the electrochemical system of step 1, constant potential treatment is performed by using constant potential method with (a±0.2) as the applied potential to obtain Cu@NF; Step 3, electrochemical preparation of Cu2S@NF: Cu@NF obtained in step 2 is immersed into an electrolyte solution containing a sulfur-containing inorganic substance as a working electrode, and cyclic voltammetry is performed to obtain a sulfidation potential of Cu as b; cyclic voltammetry scanning is performed in the voltage range of (b±0.5) to realize sulfidation treatment of Cu, and a Cu2S@NF self-supporting catalyst is obtained. In step 1, the copper ions in the electrolyte solution are derived from a water-soluble copper salt, and the molar concentration of the water-soluble copper salt in the electrolyte solution is 5-30 mM; in step 3, the molar concentration of the sulfur-containing inorganic substance in the electrolyte solution is 1-15 mM; and in step 3, the cyclic voltammetry scanning is performed for 20-60 cycles during the sulfidation treatment.

3. The preparation method according to claim 2, characterized in that, Step 2, electrochemical preparation of Cu@NF: in the electrochemical system of step 1, constant potential treatment is performed by using constant potential method with (a±0.1) as the applied potential to obtain Cu@NF.

4. The preparation method according to claim 2, characterized in that, Step 3, electrochemical preparation of Cu2S@NF: Cu@NF obtained in step 2 is immersed into an electrolyte solution containing a sulfur-containing inorganic substance as a working electrode, and cyclic voltammetry is performed to obtain a sulfidation potential of Cu as b; cyclic voltammetry scanning is performed in the voltage range of (b±0.3) to realize sulfidation treatment of Cu, and a Cu2S@NF self-supporting catalyst is obtained.

5. The preparation method according to claim 2, characterized in that, Pretreatment of the foamed nickel is performed before step 1.

6. The preparation method according to claim 5, characterized in that, The foamed nickel is ultrasonically cleaned in an acid solution, an alcohol solvent and distilled water, respectively.

7. The preparation method according to claim 2, wherein, In step 1, the electrolyte solution is a neutral solution; and / or, In step 1, the reference electrode is selected from one of Ag / AgCl electrode, saturated calomel electrode and Hg / HgO electrode; and / or, In step 1, the counter electrode is selected from one of Pt wire and graphite rod.

8. The preparation method according to claim 7, wherein, In step 1, the electrolyte solution is a neutral salt solution.

9. The preparation method according to any one of claims 2-8, wherein, In step 3, the sulfur-containing inorganic substance is selected from at least one of NaHS and Na2S; and / or, In step 3, the electrolyte solution is an alkaline aqueous solution.

10. The production method according to any one of claims 2 to 8, characterized by, In step 3, the molar concentration of the sulfur-containing inorganic substance in the electrolyte solution is 3-8 mM.

11. The preparation method according to claim 9, wherein, In step 3, cyclic voltammetry is performed in a potential range of -1.0~ -0.5 V.

12. The preparation method according to claim 9, characterized in that, In step 3, cyclic voltammetry is performed for 30~50 cycles during the sulfuration process.

13. Use of the self-supporting catalyst of claim 1 or the self-supporting catalyst obtained by the preparation method of any one of claims 2~12 in overall water splitting.

14. Use according to claim 13, characterized in that, Use of the self-supporting catalyst in overall water splitting under alkaline conditions.

15. The use according to claim 13, characterized in that, An electrochemical three-electrode system including a working electrode, a reference electrode and a counter electrode is constructed to perform hydrogen evolution reaction and oxygen evolution reaction, wherein the self-supporting catalyst is used as the working electrode; or, a two-electrode system including a working electrode and a counter electrode is constructed to perform overall water splitting, wherein the self-supporting catalyst is used as the working electrode and the counter electrode.

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