An electrocatalyst, a method for preparing the same, and use thereof

Abstract

The application discloses an electrocatalyst, a preparation method and application thereof, and relates to the technical field of electrocatalysis. By loading multi-metal oxides on a foam substrate, metal elements in the multi-metal oxides include Fe, Co, Cr and Cu, synergistic effects of multiple metals are utilized, and strong interaction of Cu-Cr in a dissolving and electrochemical deposition process, so that FeCoCrCuO x @CF shows excellent HER catalytic activity, can efficiently and stably electrolyze water under high current density, shows excellent long-term stability for HER, and has a good application prospect in a device for large-scale electrolysis of water to produce hydrogen.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, and more specifically, to an electrocatalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen is an important carrier of green energy and a major raw material for ammonia fertilizer production, playing a vital role in industrial production. Generally speaking, many H2 production processes come at the expense of the environment. For example, in the most commonly used industrial steam methane reforming (SMR) process, producing 1 ton of H2 generates at least 6.6 tons of CO2.

[0003] Hydrogen production via water electrolysis powered by renewable energy is a green hydrogen production technology that is still in its early stages, and the hydrogen produced by this process accounts for only a small portion of the market share. The water electrolysis catalyst, as the core material of electrocatalytic hydrogen production equipment, is a major factor limiting the development of green hydrogen production processes. Specifically, noble metal catalysts (such as Pt and IrO2 / RuO2) play an important role in water splitting, but they suffer from scarcity, high cost, and instability at high current densities, hindering their widespread industrial application.

[0004] Therefore, developing a low-cost water electrolysis catalyst that can operate efficiently and stably at high current densities remains a pressing technical problem that needs to be solved.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an electrocatalyst, its preparation method and application, with the aim of providing a low-cost water electrolysis catalyst that can operate efficiently and stably at high current densities.

[0007] This invention is implemented as follows:

[0008] In a first aspect, the present invention provides an electrocatalyst comprising a foam substrate and a multi-metal oxide supported on the foam substrate, wherein the metal elements in the multi-metal oxide include Fe, Co, Cr and Cu.

[0009] In an optional embodiment, the molar ratio of Fe, Co, Cr and Cu in the polymetallic oxide is 1:0.5-1.0:0.5-1.0:0.5-1.0; preferably 1:0.8-1.0:0.8-1.0:0.8-1.0.

[0010] In an optional embodiment, the mass ratio of the foam substrate to the total mass of the multi-metal oxide is 1:0.9 to 1.3, preferably 1:1.0 to 1.2;

[0011] Preferably, the foam substrate is at least one of a cobalt foam substrate and a nickel-iron foam substrate.

[0012] In a second aspect, the present invention provides a method for preparing any of the electrocatalysts in the foregoing embodiments, comprising: loading a polymetallic oxide onto a foam substrate.

[0013] In an optional embodiment, iron salt, cobalt salt, chromium salt and copper salt are mixed in a solution system to obtain a mixed salt solution, and the mixed salt solution is loaded onto a foam substrate and reacted at 280℃~320℃ for 8h-15h.

[0014] Preferably, the total concentration of metal elements in the mixed salt solution is 2M to 3M, and the mass-to-volume ratio of the foam substrate to the mixed salt solution is (45 to 52) mg:(5 to 10) mL;

[0015] Preferably, the mixed salt solution is loaded onto a foam substrate at 280°C to 320°C by dropwise addition.

[0016] In an optional embodiment, the preparation process of the mixed salt solution includes: mixing an iron salt solution, a cobalt salt solution, a chromium salt solution, and a copper salt solution and then ultrasonically treating the mixture;

[0017] Preferably, the iron salt solution, cobalt salt solution, chromium salt solution, and copper salt solution are all aqueous solutions of nitric acid.

[0018] In an optional embodiment, the method further includes: performing post-processing after the reaction is complete to obtain the precursor to be activated, and then performing electrochemical activation treatment on the precursor to be activated.

[0019] Preferably, the electrochemical activation process includes: using the precursor to be activated as the working electrode, selecting a counter electrode and a reference electrode, and performing CV activation in an electrolyte;

[0020] More preferably, the counter electrode is a carbon rod, the reference electrode is Hg / HgO, and the electrolyte is a 0.8M to 1.2M inorganic alkaline solution; even more preferably, the inorganic alkaline solution is an aqueous solution of potassium hydroxide.

[0021] More preferably, when the electrochemical activation treatment is HER electrochemical activation, the number of CV activation cycles is 3500 to 4500, the scan rate is 280 mV / s to 320 mV / s, and the potential range is -1.7 V to -1.4 V.

[0022] More preferably, when the electrochemical activation treatment is OER electrochemical activation, the number of CV activation cycles is 80 to 120, the scan rate is 280 mV / s to 320 mV / s, and the potential range is 0.7 V to 1.0 V.

[0023] In an optional embodiment, the post-processing includes: cooling the reacted material to room temperature, and then sequentially washing with water and ultrasonic treatment.

[0024] In an optional embodiment, the foam substrate is pretreated before the mixed salt solution is loaded onto the foam substrate. The pretreatment process includes: ultrasonically treating the foam substrate sequentially with an organic solvent, an inorganic acid, and water.

[0025] Preferably, the organic solvent is selected from at least one of acetone and ethanol;

[0026] Preferably, the inorganic acid is hydrochloric acid.

[0027] Thirdly, the present invention provides the application of the electrocatalyst of any of the foregoing embodiments or the electrocatalyst prepared by any of the foregoing embodiments in the hydrogen evolution reaction, oxygen evolution reaction or total water splitting.

[0028] This invention has the following beneficial effects: By loading a multi-metal oxide onto a foam substrate, the metal elements in the multi-metal oxide including Fe, Co, Cr, and Cu, and utilizing the synergistic effect of multiple metals and the strong interaction between Cu and Cr during dissolution and electrochemical deposition, FeCoCrCuO x @CF exhibits outstanding HER catalytic activity, can efficiently and stably electrolyze water at high current densities, demonstrates excellent long-term stability for HER, and shows promising application prospects in large-scale water electrolysis hydrogen production devices. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 The polarization curves for the hydrogen evolution reaction are shown.

[0031] Figure 2 The polarization curves for the oxygen evolution reaction are shown.

[0032] Figure 3 The polarization curves for the total water splitting of the bifunctional catalyst are shown.

[0033] Figure 4 FeCoCrCuO x @CF catalytic material and commercial material electrolysis water stability test curves;

[0034] Figure 5The LSV curves are shown before and after the catalyst stability test. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] Transition metal oxides (TMOs) have been extensively studied as highly efficient electrocatalysts for HER / OER due to their low cost, multiple valence states, simple preparation, and suitable electronic configurations, especially for oxides of iron, nickel, and cobalt. However, their electrocatalytic performance is unsatisfactory due to their inherent weak conductivity. Based on this, this application aims to prepare an electrocatalyst capable of achieving efficient and stable hydrogen production at high current densities by improving the selection of metal elements.

[0037] This invention provides an electrocatalyst comprising a foam substrate and a multi-metal oxide supported on the foam substrate. The metal elements in the multi-metal oxide include Fe, Co, Cr and Cu. Due to the synergistic effect of the multiple metals and the strong interaction between Cu and Cr during dissolution and electrochemical deposition, the electrocatalyst exhibits outstanding HER catalytic activity.

[0038] In some embodiments, the foam substrate is a cobalt foam substrate (CF), and its structural formula can be represented as FeCoCrCuO. x @CF, using cobalt foam as a substrate is beneficial for further improving catalytic performance. Specifically, the cobalt foam substrate is a commercially available material.

[0039] In some embodiments, the molar ratio of Fe, Co, Cr, and Cu in the polymetallic oxide is 1:0.5–1.0:0.5–1.0:0.5–1.0; preferably 1:0.8–1.0:0.8–1.0:0.8–1.0. Controlling the amounts of Fe, Co, Cr, and Cu within the above range is preferable, as it significantly improves the FeCoCrCuO content. x The catalytic activity of @CF. Specifically, in polymetallic oxides, the molar ratio of Fe, Co, Cr and Cu can be 1:0.5:0.5:0.5, 1:0.6:0.6:0.6, 1:0.7:0.7:0.7, 1:0.8:0.8:0.8, 1:0.9:0.9:0.9, 1:1.0:1.0:1.0, etc.

[0040] Furthermore, the mass ratio of the foam substrate to the total mass of the multi-metal oxide is 1:0.9 to 1.3, preferably 1:1.0 to 1.2. Specifically, the mass ratio of the foam substrate to the total mass of the multi-metal oxide can be 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, etc.

[0041] This invention also provides a method for preparing an electrocatalyst, comprising: loading the aforementioned multi-metal oxide onto a foam substrate, the specific preparation method being unrestricted. In some embodiments, the preparation can be carried out using the following method:

[0042] S1, Preprocessing

[0043] Before loading the mixed salt solution onto the foam substrate, the foam substrate is pretreated. The pretreatment cleans the foam substrate and forms acid corrosion, making it easier to load multi-metal oxides.

[0044] In some embodiments, the pretreatment process includes: sequentially ultrasonically treating the foam substrate with an organic solvent, an inorganic acid, and water, first cleaning the surface with an organic solvent, then acid etching the surface with an inorganic acid, and then cleaning the residual organic solvent and inorganic acid with water.

[0045] Furthermore, the organic solvent is selected from at least one of acetone and ethanol, and can be any one or more of the above; the inorganic acid is hydrochloric acid, and can be any one or more of the above.

[0046] S2, supported polymetallic oxide

[0047] Iron, cobalt, chromium, and copper salts were mixed in a solution system to obtain a mixed salt solution. This mixed salt solution was then loaded onto a foam substrate and reacted at 280℃–320℃ for 8–15 hours. Under high temperature conditions, the nitrates decomposed to form oxides, resulting in oxides of the metal elements loaded onto the foam substrate.

[0048] Specifically, the reaction temperature can be 280℃, 290℃, 300℃, 310℃, 320℃, etc., and the reaction time can be 8h, 10h, 12h, 15h, etc.

[0049] In some embodiments, the total concentration of metal elements in the mixed salt solution is 2M to 3M, such as 2.0M, 2.5M, 3.0M, etc. The mass-to-volume ratio of the foam substrate to the mixed salt solution is (45-52) mg:(5-10) mL, to ensure that the amount of metal oxide loaded meets the requirements. Specifically, the mass-to-volume ratio of the foam substrate to the mixed salt solution can be 45 mg:5 mL, 48 mg:7 mL, 50 mg:8 mL, 52 mg:10 mL, etc.

[0050] In some embodiments, the mixed salt solution is loaded onto a foam substrate at 280°C to 320°C by dripping. The dripping method controls the slow addition of the mixed salt solution, thereby improving the uniformity of solution distribution.

[0051] In some embodiments, the preparation process of the mixed salt solution includes: mixing an iron salt solution, a cobalt salt solution, a chromium salt solution, and a copper salt solution, followed by ultrasonic treatment. The ultrasonic treatment time is not limited, and a homogeneous solution is formed by ultrasonic treatment. The iron salt solution, cobalt salt solution, chromium salt solution, and copper salt solution can be, but are not limited to, an aqueous solution of nitric acid, i.e., a mixture of an aqueous solution of ferric nitrate, an aqueous solution of cobalt nitrate, an aqueous solution of chromium nitrate, and an aqueous solution of copper nitrate.

[0052] S3, Post-processing

[0053] After the reaction is complete, post-processing is performed to obtain the precursor to be activated. The post-processing process involves separating the products after the reaction. In actual operation, the material can be cooled to room temperature after the reaction is complete, and then subjected to water washing and ultrasonic treatment in sequence. Impurities are removed by water washing, and loosely attached particles are removed by ultrasonic treatment. The ultrasonic treatment time can be very short, such as 8s-20s.

[0054] S4, Electrochemical Activation Treatment

[0055] Electrochemical activation of the precursor to be activated is beneficial to improving the catalytic activity of the material.

[0056] It should be noted that some components in the precursor will leach out at the interface between the catalyst and the electrolyte and react with the electrolyte. As the activation time increases, some of the leached components will deposit back onto the catalyst surface, resulting in a remodeling of the catalyst's surface morphology.

[0057] In some embodiments, the electrochemical activation process includes: using the precursor to be activated as the working electrode, selecting a counter electrode and a reference electrode, and performing CV activation in an electrolyte. The parameter control for HER electrochemical activation and OER electrochemical activation differs slightly.

[0058] In some embodiments, the counter electrode may be, but is not limited to, a carbon rod; the reference electrode may be, but is not limited to, Hg / HgO; and the electrolyte is a 0.8M to 1.2M inorganic alkaline solution (such as 0.8M, 1.0M, 1.2M, etc.), which may be, but is not limited to, an aqueous solution of potassium hydroxide. The above-described counter electrode, reference electrode, and electrolyte can be used for both HER electrochemical activation and OER electrochemical activation.

[0059] Furthermore, when the electrochemical activation treatment is HER electrochemical activation, the number of CV activation cycles is 3500–4500, the scan rate is 280 mV / s–320 mV / s, and the potential range is -1.7 V to -1.4 V. Specifically, the number of activation cycles can be 3500, 3800, 4000, 4200, 4500, etc.; the scan rate can be 280 mV / s, 300 mV / s, 320 mV / s, etc.

[0060] Furthermore, when the electrochemical activation treatment is OER electrochemical activation, the number of CV activation cycles is 80–120, the scan rate is 280 mV / s–320 mV / s, and the potential range is 0.7 V–1.0 V. Specifically, the number of activation cycles can be 80, 90, 100, 110, 120, etc.; the scan rate can be 280 mV / s, 300 mV / s, 320 mV / s, etc.

[0061] Tests showed that electrochemically activated FeCoCrCuO x @CF not only at 10mA cm -2 An ultra-low overpotential of 40mV was achieved at a current density, and a dec voltage as low as 27.3mV was also achieved. -1 The Tafel slope is superior to most reported transition metal catalysts and comparable to commercial Pt / C. Furthermore, at 500 mA cm⁻¹... -2 At high current densities, this catalyst exhibits excellent long-term stability for HER, with the voltage increasing by only 31 mV after 165 h of stability testing. Meanwhile, FeCoCrCuO... x The @CF catalyst also exhibited excellent long-term stability throughout the water splitting process. At 500 mA cm⁻¹ -2 At high current densities, after 100 hours of overall water decomposition, the voltage increased by only 7 mV. More importantly, even in simulated industrial environments (6 M KOH, 60 °C), at high current densities (500 mA cm⁻¹), the voltage remained stable. -2 Under these conditions, after 100 hours of overall water decomposition, the voltage only increased by 24mV.

[0062] Based on the above effects, FeCoCrCuO x @CF has promising applications in large-scale water electrolysis hydrogen production devices, specifically in hydrogen evolution reaction, oxygen evolution reaction, or total water electrolysis reaction processes.

[0063] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0064] Example 1

[0065] This embodiment provides a method for preparing an electrocatalyst, including the following steps:

[0066] (1) Preprocessing

[0067] Take a cobalt foam substrate (CF, 1cm x 1.2cm, 1.6mm thick) and sonicate it for 10 minutes in sequence with acetone, 6M hydrochloric acid and deionized water.

[0068] (2) Loaded polymetallic oxides

[0069] Mixing Fe(NO3)3·9H2O with water yields a 2.5M iron nitrate solution; mixing Co(NO3)2·6H2O with water yields a 2.5M cobalt nitrate solution; mixing Cr(NO3)3·9H2O with water yields a 2.5M chromium nitrate solution; and mixing Cu(NO3)2·3H2O with water yields a 2.5M copper nitrate solution.

[0070] An equal volume of the above 2.5M metal nitrate solution was added to a clean, dry vial, and then sonicated to form a homogeneous solution, resulting in a mixed salt solution containing Fe, Co, Cr, and Cu elements.

[0071] 100 μL of mixed salt solution was added dropwise to the CF substrate at 300 °C, and the reaction was repeated three times. The substrate was then kept at 300 °C overnight for a total of 12 h.

[0072] (3) Post-processing

[0073] After the reaction was complete, the sample was cooled to room temperature, rinsed with deionized water, and then sonicated for 10 seconds to remove loosely attached particles. The resulting product was named FeCoCrCuO. x @CF.

[0074] Comparative Example 1

[0075] The only difference from Example 1 is that the types of elements in the mixed salt solution in step (2) are different, as follows: In step (2), equal volumes of 2.5M iron nitrate solution and cobalt nitrate solution are added to a clean and dry vial, and then ultrasonic treatment is performed to form a homogeneous solution, resulting in a mixed salt solution containing FeCo elements.

[0076] The product obtained in this comparative example is named FeCoO x @CF.

[0077] Comparative Example 2

[0078] The only difference from Example 1 is that the types of elements in the mixed salt solution in step (2) are different, as follows: In step (2), equal volumes of 2.5M iron nitrate solution, cobalt nitrate solution and chromium nitrate solution are added to a clean and dry vial, and then ultrasonic treatment is performed to form a homogeneous solution to obtain a mixed salt solution containing FeCoCr elements.

[0079] The product obtained in this comparative example is named FeCoCrO x @CF.

[0080] Comparative Example 3

[0081] The only difference from Example 1 is that the types of elements in the mixed salt solution in step (2) are different, as follows: In step (2), equal volumes of 2.5M iron nitrate solution, cobalt nitrate solution and copper nitrate solution are added to a clean and dry vial, and then ultrasonic treatment is performed to form a homogeneous solution to obtain a mixed salt solution containing FeCoCu elements.

[0082] The product obtained in this comparative example is named FeCoCuO. x @CF.

[0083] Experimental Example 1

[0084] The performance of the products obtained in the test examples and Comparative Example 1, including hydrogen evolution, oxygen evolution, and total water splitting performance, was compared with that of Pt / C and RuO2. The results are shown in Table 1.

[0085] Test method:

[0086] (1) HER electrochemical activation part

[0087] Electrochemical activation of the sample is required before testing HER performance. Specifically, the obtained sample is used as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode. CV activation is performed for 4000 cycles in a 1M KOH electrolyte. The scan rate is 300 mV / s. -1 The potential range is -1.7V to -1.4V (vs Hg / HgO).

[0088] (2) Electrochemical activation part of OER

[0089] Electrochemical activation of the sample is required before testing OER performance. Specifically, the obtained sample is used as the working electrode, a carbon rod as the counter electrode, and Hg / HgO as the reference electrode. CV activation is performed for 100 cycles in a 1M KOH electrolyte. The scan rate is 300 mV / s. -1 The potential range is 0.7V to 1.0V (vs Hg / HgO).

[0090] Table 1 Comparison of hydrogen and oxygen evolution and total water electrolysis performance.

[0091]

[0092]

[0093] The polarization curve of the hydrogen evolution reaction is as follows: Figure 1 As shown, the polarization curve of the oxygen evolution reaction is as follows: Figure 2 As shown, the polarization curves of total water splitting are as follows: Figure 3 As shown, FeCoCrCuO x The electrolysis stability test curves of @CF catalytic materials and commercial materials are shown below. Figure 4 As shown, the LSV curves before and after the catalyst stability test are as follows: Figure 5 As shown.

[0094] It can be seen that FeCoCrCuO x @CF catalytic materials exhibit better stability at 500 mA cm⁻¹ -2 At the specified current density, the performance curve showed little fluctuation after 100 hours of performance testing at room temperature, indicating that the performance was essentially maintained. Conversely, under the same conditions, the fully hydrolyzing electrode composed of commercial materials showed significant fluctuations in its curve after 80 hours of stability testing, and the voltage increased by 75mV after 100 hours of stability testing. Furthermore, even under simulated industrial conditions (6M KOH, 60℃), at 500mA cm⁻¹... -2 Under a current density of [value], after 100 hours of testing, FeCoCrCuO [resulted in a certain value]. x @CF catalyst voltage increased by only 24mV, outperforming commercial materials.

[0095] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electrocatalyst, characterized in that, It includes a foam substrate and a multi-metal oxide supported on the foam substrate, wherein the metal elements in the multi-metal oxide are Fe, Co, Cr and Cu; The preparation process of the electrocatalyst includes: mixing iron salt solution, cobalt salt solution, chromium salt solution and copper salt solution in a solution system to obtain a mixed salt solution, loading the mixed salt solution onto the foam substrate, and reacting at 280℃~320℃ for 8h-15h; wherein the iron salt solution, the cobalt salt solution, the chromium salt solution and the copper salt solution are respectively an aqueous solution of iron nitrate, an aqueous solution of cobalt nitrate, an aqueous solution of chromium nitrate and an aqueous solution of copper nitrate; After the reaction is completed, post-processing is performed to obtain the precursor to be activated, and the precursor to be activated is subjected to electrochemical activation treatment; the electrochemical activation treatment process includes: using the precursor to be activated as the working electrode, selecting the counter electrode and the reference electrode, and performing CV activation in an electrolyte; the electrolyte is a 0.8M~1.2M inorganic alkaline solution; When the electrochemical activation treatment is HER electrochemical activation, the number of CV activation cycles is 3500~4500 cycles, the scan rate is 280mV / s~320mV / s, and the potential range is -1.7V~-1.4Vvs Hg / HgO; When the electrochemical activation treatment is OER electrochemical activation, the number of CV activation cycles is 80~120 cycles, the scan rate is 280mV / s~320mV / s, and the potential range is 0.7V~1.0Vvs Hg / HgO; In the polymetallic oxide, the molar ratio of Fe, Co, Cr and Cu is 1:0.5~1.0:0.5~1.0:0.5~1.0, and the total concentration of metal elements in the mixed salt solution is 2M~3M.

2. The electrocatalyst according to claim 1, characterized in that, In the polymetallic oxide, the molar ratio of Fe, Co, Cr and Cu is 1:0.8~1.0:0.8~1.0:0.8~1.

0.

3. The electrocatalyst according to any one of claims 1-2, characterized in that, The mass ratio of the foam substrate to the total mass of the multi-metal oxide is 1:0.9~1.

3.

4. The electrocatalyst according to claim 3, characterized in that, The mass ratio of the foam substrate to the total mass of the multi-metal oxide is 1:1.0~1.

2.

5. The electrocatalyst according to claim 1, characterized in that, The foam substrate is selected from at least one of cobalt foam substrate and nickel-iron foam substrate.

6. A method for preparing the electrocatalyst according to any one of claims 1 to 5, characterized in that, include: A mixed salt solution is obtained by mixing iron salt solution, cobalt salt solution, chromium salt solution and copper salt solution in a solution system. The mixed salt solution is then loaded onto the foam substrate and reacted at 280℃~320℃ for 8h-15h. The iron salt solution, the cobalt salt solution, the chromium salt solution, and the copper salt solution are respectively an aqueous solution of ferric nitrate, an aqueous solution of cobalt nitrate, an aqueous solution of chromium nitrate, and an aqueous solution of copper nitrate; After the reaction is complete, post-processing is performed to obtain the precursor to be activated, and the precursor to be activated is subjected to electrochemical activation treatment. The electrochemical activation process includes: using the precursor to be activated as the working electrode, selecting a counter electrode and a reference electrode, and performing CV activation in an electrolyte; The electrolyte is a 0.8M~1.2M inorganic alkaline solution; When the electrochemical activation treatment is HER electrochemical activation, the number of CV activation cycles is 3500~4500 cycles, the scan rate is 280mV / s~320mV / s, and the potential range is -1.7V~-1.4Vvs Hg / HgO; When the electrochemical activation treatment is OER electrochemical activation, the number of CV activation cycles is 80~120 cycles, the scan rate is 280mV / s~320mV / s, and the potential range is 0.7V~1.0V vs Hg / HgO; In the polymetallic oxide, the molar ratio of Fe, Co, Cr and Cu is 1:0.5~1.0:0.5~1.0:0.5~1.0, and the total concentration of metal elements in the mixed salt solution is 2M~3M.

7. The preparation method according to claim 6, characterized in that, The mixed salt solution was loaded onto a foam substrate at 280℃~320℃ by dropwise addition.

8. The preparation method according to claim 6, characterized in that, The preparation process of the mixed salt solution includes: mixing iron salt solution, cobalt salt solution, chromium salt solution and copper salt solution and then ultrasonically treating them.

9. The preparation method according to claim 6, characterized in that, Also includes: The counter electrode is a carbon rod, and the reference electrode is Hg / HgO.

10. The preparation method according to claim 9, characterized in that, The inorganic alkaline solution is an aqueous solution of potassium hydroxide.

11. The preparation method according to claim 6, characterized in that, The post-processing includes: cooling the reacted material to room temperature, and then sequentially washing with water and ultrasonic treatment.

12. The preparation method according to claim 6, characterized in that, Before loading the mixed salt solution onto the foam substrate, the foam substrate is pretreated. The pretreatment process includes ultrasonically treating the foam substrate sequentially with an organic solvent, an inorganic acid, and water.

13. The preparation method according to claim 12, characterized in that, The organic solvent is selected from at least one of acetone and ethanol.

14. The preparation method according to claim 12, characterized in that, The inorganic acid is hydrochloric acid.

15. The use of the electrocatalyst according to any one of claims 1 to 5 or the electrocatalyst prepared by any one of claims 6 to 14 in the hydrogen evolution reaction, oxygen evolution reaction or total water splitting.

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