A S-(FeNiM)LDH / IF electrocatalyst, preparation method and application thereof

Abstract

The present invention relates to the technical field of electrocatalytic water decomposition to produce hydrogen, and in particular to an S-(FeNiM)LDH / IF electrocatalyst, a preparation method, and applications thereof. M is Co or In, and the electrocatalyst is a three-dimensional layered nanosheet structure sheet. Cobalt acetate (or indium chloride), nickel acetate, and foamed iron are used as raw materials. The cobalt acetate and nickel acetate are first dissolved in H2O and ethanol at a temperature of 25°C. After reacting for 30 minutes, a Na2S solution is slowly added and the reaction is continued for 30 minutes. A NaOH solution is slowly added dropwise and reacted for 30 minutes. The reaction is then heated to 80°C and reacted for 2.5 hours to obtain a composite material S-(FeNiM)LDH / IF (M=Co, In) having a layered nanosheet structure. The S-(FeNiCo)LDH / IF composite material prepared by the present invention was used as the anode, and the S-(FeNiIn)LDH / IF composite material prepared by the present invention was used as the cathode to form an electrolytic cell (S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF), which was used for electrolysis of water and achieved good catalytic effect.

Description

Technical Field

[0001] The present invention relates to the technical field of electrocatalytic water decomposition to produce hydrogen, and in particular to an S-(FeNiM)LDH / IF electrocatalyst, a preparation method and applications thereof. Background Art

[0002] The development of clean renewable energy is an inevitable choice for human society to achieve sustainable development. Electrolysis of water to produce H2 is one of the effective methods for the production, storage and use of renewable energy in the future. The process includes the oxygen evolution reaction (OER, OH - -4e - →O2+2H2O, in alkaline medium) and hydrogen evolution reaction (HER, 2H2O+2e - →2OH - +H2). Because the oxygen evolution reaction (OER) involves the transfer of four protons and electrons, its high chemical energy barrier and slow reaction kinetics hinder the industrialization of H2 production through water electrolysis. Furthermore, OER is a fundamental reaction in electrochemical energy conversion and storage systems, including CO2 / N2 reduction, fuel cells, and metal-air batteries. Currently, the most effective OER catalysts are oxides of the precious metals iridium and ruthenium (IrO2 and RuO2), but their scarcity and high cost severely limit their large-scale application. Therefore, the development of efficient and stable non-precious metal-based OER catalysts holds great scientific value and broad application prospects.

[0003] The commonly used non-precious metal catalysts for OER are mainly Fe, Co and Ni-based catalysts. Although people have been committed to studying the preparation methods and principles of this type of catalysts for many years, it is still challenging to develop non-precious metal-based OER catalysts with high activity, high stability and low cost.

[0004] In view of the above-mentioned defects, the inventors of the present invention finally obtained the present invention after a long period of research and practice. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the current non-precious metal OER reaction catalysts have high potentials and slow OER kinetic reactions, which hinder the realization of industrial electrolysis of water to produce H2. A S-(FeNiM)LDH / IF electrocatalyst, a preparation method and its application are provided.

[0006] In order to achieve the above object, the present invention discloses an S-(FeNiM)LDH / IF electrocatalyst, wherein M is Co or In, and the electrocatalyst is a three-dimensional layered nanosheet structure sheet.

[0007] The present invention also discloses a method for preparing the above-mentioned S-(FeNiM)LDH / IF electrocatalyst, comprising the following steps:

[0008] S1, put cobalt acetate or indium chloride, nickel acetate and iron foam into a round-bottom flask, add H2O and ethanol, stir in an oil bath at 25°C for 30 minutes, and then slowly add Na2S solution dropwise;

[0009] S2, stirring the solution obtained in step S1 for 30 min, and then slowly adding dropwise a mixed solution consisting of NaOH and H2O;

[0010] S3, continue stirring the solution obtained in step S2 for 30 minutes, then stir it at 80°C and keep it warm for 0.5 to 3.5 hours, collect the product, wash it with H2O, and obtain a sample after drying. If cobalt acetate is used in step S1, S-(FeNiCo)LDH / IF electrocatalyst will be obtained, and if indium chloride is used, S-(FeNiIn)LDH / IF electrocatalyst will be obtained.

[0011] In step S1, the amount of cobalt acetate or indium chloride is 0.5-1.26 mmol, the amount of nickel acetate is 0.5-1.26 mmol, the foam iron is a piece of 1×0.5 cm foam iron, the amount of H2O is 10-45 mL, the amount of ethanol is 5-40 mL, the amount of Na2S in the Na2S solution is 2.5-12.5 mg, and the amount of H2O is 2.5 mL.

[0012] In step S1, the amount of cobalt acetate or indium chloride is 0.36 mmol, the amount of nickel acetate is 0.90 mmol, the foam iron is a piece of 1×0.5 cm foam iron, the amount of H2O is 35 mL, the amount of ethanol is 15 mL, the amount of Na2S in the Na2S solution is 7.5 mg, and the amount of H2O is 2.5 mL.

[0013] In step S2, the amounts of NaOH and H2O in the mixed solution of NaOH and H2O are 30-100 mg and 2.5 mL, respectively.

[0014] In step S2, the amounts of NaOH and H2O in the mixed solution of NaOH and H2O are 50 mg and 2.5 mL, respectively.

[0015] In step S3, the holding temperature is 80° C. and the holding time is 2.5 h.

[0016] The present invention also discloses the application of the above-mentioned S-(FeNiM)LDH / IF electrocatalyst in OER, HER and overall water splitting reactions.

[0017] Compared with the prior art, the beneficial effects of the present invention are:

[0018] 1. The preparation process of the catalyst is simple: The preparation process of S-(FeNiM)LDH / IF (M=Co, In) is simple and is completed using a "seed" assisted method. Using cobalt acetate (or indium chloride), nickel acetate, and foamed iron as raw materials, the cobalt acetate and nickel acetate are first dissolved in H2O and ethanol at a temperature of 25°C. After reacting for 30 minutes, Na2S solution is slowly added and the reaction is continued for 30 minutes. NaOH solution is slowly added dropwise and reacted for 30 minutes. The temperature is then raised to 80°C and reacted for 2.5 hours to obtain a composite material S-(FeNiM)LDH / IF (M=Co, In) with a layered nanosheet structure.

[0019] 2. The present invention establishes a redox equilibrium system with a simple composition, including H2O, ethanol, Na2S and O2 in the air, which can effectively regulate the micromorphology and electronic structure of S-(FeNiM)LDH / IF(M=Co,In). The product S-(FeNiM)LDH / IF(M=Co,In) after regulation has a nanosheet structure. The Na2S in this equilibrium system is reducing and the O2 in the air is oxidizing, which can effectively regulate the electronic structure of S-(FeNiM)LDH / IF(M=Co,In). In the product S-(FeNiM)LDH / IF(M=Co,In) after regulation, sulfur exists in an oxidized form, and the valence states of iron, nickel and cobalt are mainly +2 and +3. The microstructure and unique electronic structure of S-(FeNiM)LDH / IF(M=Co,In) nanosheets are the main reasons for its ability to significantly improve the OER electrochemical performance;

[0020] 3. High OER catalytic activity: When the S-(FeNiCo)LDH / IF prepared by the present invention is used for OER reaction, the test equipment is an electrochemical workstation, the working electrode is the S-(FeNiCo)LDH / IF electrode prepared above, the counter electrode is a platinum sheet electrode (1×2 cm), the reference electrode is a Hg / HgO electrode, and the electrolyte is a 1M KOH solution. Under the above test conditions, the current density reaches 1000 mA cm -2 The corresponding OER reaction overpotential is only 288 mV, while under the same test conditions, (FeNiCo)LDH / IF is -2 The corresponding overpotential at the current density is 357mV. In comparison, the OER electrochemical performance of S-(FeNiCo)LDH / IF is greatly improved. Moreover, compared with other catalysts, S-(FeNiCo)LDH / IF can also be listed as one of the OER catalysts with better electrochemical performance; and S-(FeNiCo)LDH / IF has good catalytic stability: after 5000 cycles of cyclic voltammetry and 130h it test, the OER performance has not been significantly reduced.

[0021] 4. High HER catalytic activity: The present invention also uses a similar preparation method to prepare a sulfur-doped iron nickel indium layered hydroxide (S-(FeNiIn)LDH / IF) composite material. When the S-(FeNiIn)LDH / IF prepared by the present invention is used for the HER reaction, the test equipment is an electrochemical workstation, the working electrode is the S-(FeNiIn)LDH / IF electrode prepared above, the counter electrode is a platinum sheet electrode (1×2cm), the reference electrode is a Hg / HgO electrode, and the electrolyte is a 1M KOH solution. Under the above test conditions, the current density reaches 100mA·cm -2 The corresponding HER reaction overpotential is only 174mV, while under the same test conditions, (FeNiCo)LDH / IF is -2 The corresponding overpotential at this current density is 232 mV. In comparison, the electrochemical performance of S-(FeNiIn)LDH / IF is significantly improved. Moreover, compared with other catalysts, S-(FeNiIn)LDH / IF is also one of the HER electrocatalysts with better electrochemical performance. Moreover, S-(FeNiIn)LDH / IF has good catalytic stability: after 5000 cycles of cyclic voltammetry, the HER performance has not been significantly reduced.

[0022] 5. Good water electrolysis performance: The S-(FeNiCo)LDH / IF composite material prepared by the present invention is used as the anode, and the S-(FeNiIn)LDH / IF composite material prepared by the present invention is used as the cathode to form an electrolytic cell (S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF), which is used for water electrolysis and achieves good catalytic effect. The test equipment is an electrochemical workstation, and the electrolyte is 1M KOH solution. When the current density reaches 500mA·cm -2 When the electrolysis reaction potential of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF is only 1.74 V, under the same test conditions, the electrolysis reaction potential of (FeNiCo)LDH / IF||(FeNiCo)LDH / IF is only 1.74 V when the electrolysis reaction potential of (FeNiCo)LDH / IF||(FeNiCo)LDH / IF is 500 mA·cm -2 The corresponding potential at this current density is 1.99V. In comparison, the water electrolysis performance of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF is significantly improved. Furthermore, compared with other catalysts, S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF can be ranked among the best in water electrolysis performance. Furthermore, the catalytic stability of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF in water electrolysis is excellent, with no significant decrease in water electrolysis performance after 145 hours of testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 SEM images of S-(FeNiCr)(OH)2 / IF with different Cr dosages (a 2.5%, b 5.0%, c 7.5%, d 10.0%, e 12.5%, f 28.5%)

[0024] Figure 2 SEM images of catalysts with different elements: (a) S-(FeNiAl)(OH)2 / IF, (b) S-(FeNiCu)

[0025] SEM images of (OH)2 / IF, (c) S-(FeNiSr)(OH)2 / IF, and (d) S-(FeNiMn)(OH)2 / IF;

[0026] Figure 3 are SEM photos of catalysts of different elements, (a) is the SEM image of Example 34, (b) is the SEM image of Example 33, (c) is the SEM image of Example 36, (d) is the SEM image of Example 32, (e) is the SEM image of Example 31, and (f) is the SEM image of Example 38;

[0027] Figure 4 OER overpotential of catalysts synthesized from different elements (a) S-(FeNiIn)LDH / IF, (b) S-(FeNiZn)LDH / IF, (c) S-(FeNiV)LDH / IF, (d) S-(FeCoIn)LDH / IF, (e) S-(FeCoZn)LDH / IF, (f) S-(FeCoV)LDH / IF, (g) (FeNiIn)LDH / IF, (h) (FeCoIn)LDH / IF, (i) S-(FeNi)LDH / IF, (j) S-(FeCo)LDH / IF, (k) (FeNi)LDH / IF, (l) (FeCo)LDH / IF, (m) (FeNiCo)S / IF, (n) (FeNiCo)LDH / IF, (o) S-(FeNiCo)LDH / IF;

[0028] Figure 5 Comparison of Tafel slopes of catalysts of different elements synthesized experimentally

[0029] Figure 6 Diagram of the preparation mechanism of S-(FeNiCo)LDH / IF;

[0030] Figure 7 This is a SEM image of the S-(FeNiCo)S-seed / IF prepared in Example 30;

[0031] Figure 8 XPS graph of S-(FeNiCo)S-seed / IF prepared in Example 30: (a) Fe 2p peak curve, (b) Ni 2p peak curve, (c) Co 2p peak curve, (d) S 2p peak curve;

[0032] Figure 9 Electron micrographs of the samples: (a) SEM photograph of foamed iron, (b, c) SEM photographs of S-(FeNiCo)LDH / IF prepared in Example 3 (b and c have different magnifications), (d) TEM photograph of S-(FeNiCo)LDH / IF prepared in Example 3, (e) HRTEM photograph of S-(FeNiCo)LDH / IF prepared in Example 3, (f) SAED diffraction rings of S-(FeNiCo)LDH / IF prepared in Example 3;

[0033] Figure 10 Raman spectrum and XPS curves of S-(FeNiCo)LDH / IF prepared in Example 3: (a) Raman spectrum; (b) XPS S2p peak curve, (c) XPS Ni2p peak curve, (d) XPS Co2p peak curve, (e) XPS Fe2p peak curve, and (f) XPS O1s peak curve.

[0034] Figure 11 Electron microscopic images of the (FeNiCo)LDH / IF prepared in Example 28: (a, b) SEM images, (c) TEM images, and (d) HRTEM images;

[0035] Figure 12 SEM images of S-(FeNiCo)LDH / IF prepared with different Na2S dosages: (a) 2.5 mg Na2S (Example 1), (b) 5.0 mg Na2S (Example 2), (c) 10 mg Na2S (Example 4), and (d) 12.5 mg Na2S (Example 5). Scale bars are 2 μm.

[0036] Figure 13 (a) SEM photo and (b) TEM photo of S-(FeNiIn)LDH / IF prepared in Example 15;

[0037] Figure 14OER performance of the prepared samples: (a) LSV curves of the OER reaction of S-(FeNiCo)LDH / IF (prepared in Example 3), S-(FeNiIn)LDH / IF (prepared in Example 15), (FeNiCo)LDH / IF (prepared in Example 28), and (FeNiIn)LDH / IF (prepared in Example 31) (electrolyte: 1 M KOH); (b) LSV curves of these samples at a current density of 1000 mA cm -2 (c) The corresponding overpotential of the OER reaction of these samples, (d) The comparison of the active area (ECSA) of S-(FeNiCo)LDH / IF (prepared in Example 3) and (FeNiCo)LDH / IF (prepared in Example 28), (e) The LSV curve of S-(FeNiCo)LDH / IF (prepared in Example 3) before and after 5000 CV scans; (f) The IT curve of S-(FeNiCo)LDH / IF (prepared in Example 3).

[0038] Figure 15 HER performance of the prepared samples: (a) LSV curves of HER reaction of S-(FeNiIn)LDH / IF (prepared in Example 15), S-(FeNiCo)LDH / IF (prepared in Example 3), (FeNiIn)LDH / IF (prepared in Example 31) and (FeNiCo)LDH / IF (prepared in Example 28) (electrolyte: 1 M KOH); (b) HER reaction of the four samples prepared in Example 15, Example 3, Example 31 and Example 28 at a current density of 100 mA cm -2 (c) Tafel slope diagram of the HER reaction of the four samples prepared in Example 15, Example 3, Example 31, and Example 28, (d) Comparison of the LSV curves of S-(FeNiIn)LDH / IF before and after 5000 CV scans.

[0039] Figure 16 Electrolysis performance of the samples: (a) LSV curves of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF, S-(FeNiCo)LDH / IF||S-(FeNiCo)LDH / IF and (FeNiCo)LDH / IF||(FeNiCo)LDH / IF (electrolyte: 1 M KOH); (b) LSV curves of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF, S-(FeNiCo)LDH / IF||S-(FeNiCo)LDH / IF and (FeNiCo)LDH / IF||(FeNiCo)LDH / IF at a current density of 500 mA cm -2(c) is the comparison between the actual and theoretical values ​​of H2 and O2 produced by S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF; (d) is the IT curve of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF. DETAILED DESCRIPTION

[0040] The above and other technical features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

[0041] Example 1

[0042] The specific preparation steps of S-(FeNiCo)LDH / IF-1 are as follows:

[0043] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 1mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0044] Example 2

[0045] The specific preparation steps of S-(FeNiCo)LDH / IF-2 are as follows:

[0046] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 2mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0047] Example 3

[0048] The specific preparation steps of S-(FeNiCo)LDH / IF-3 are as follows:

[0049] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0050] Example 4

[0051] The specific preparation steps of S-(FeNiCo)LDH / IF-4 are as follows:

[0052] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 4mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0053] Example 5

[0054] The specific preparation steps of S-(FeNiCo)LDH / IF-5 are as follows:

[0055] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 5mg / mL Na2S solution (because sodium sulfide solution has S 2-, which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0056] Example 6

[0057] The specific preparation steps of S-(FeNiCo)LDH / IF-6 are as follows:

[0058] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 15 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0059] Example 7

[0060] The specific preparation steps of S-(FeNiCo)LDH / IF-7 are as follows:

[0061] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a 40 mg / mL NaOH solution dropwise. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0062] Example 8

[0063] The specific preparation steps of S-(FeNiCo)LDH / IF-8 are as follows:

[0064] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 40mL of H2O and 5mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0065] Example 9

[0066] The specific preparation steps of S-(FeNiCo)LDH / IF-9 are as follows:

[0067] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 5mL of H2O and 40mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0068] Example 10

[0069] The specific preparation steps of S-(FeNiCo)LDH / IF-10 are as follows:

[0070] Weigh 0.5mmol of cobalt acetate and 1.26mmol of nickel acetate into a round-bottom flask, then place a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0071] Example 11

[0072] The specific preparation steps of S-(FeNiCo)LDH / IF-11 are as follows:

[0073] Weigh 1.26mmol of cobalt acetate and 0.5mmol of nickel acetate into a round-bottom flask, then place a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0074] Example 12

[0075] The specific preparation steps of S-(FeNiCo)LDH / IF-12 are as follows:

[0076] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 0.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0077] Example 13

[0078] The specific preparation steps of S-(FeNiCo)LDH / IF-13 are as follows:

[0079] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2-, which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 3.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0080] Example 14

[0081] The specific preparation steps of S-(FeNiIn)LDH / IF-1 are as follows:

[0082] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 1.25mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0083] Example 15

[0084] The specific preparation steps of S-(FeNiIn)LDH / IF-2 are as follows:

[0085] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0086] Example 16

[0087] The specific preparation steps of S-(FeNiIn)LDH / IF-3 are as follows:

[0088] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 20mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0089] Example 17

[0090] The specific preparation steps of S-(FeNiIn)LDH / IF-4 are as follows:

[0091] Weigh 0.5mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0092] Example 18

[0093] The specific preparation steps of S-(FeNiIn)LDH / IF-5 are as follows:

[0094] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 5mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2-, which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0095] Example 19

[0096] The specific preparation steps of S-(FeNiIn)LDH / IF-6 are as follows:

[0097] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 45mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0098] Example 20

[0099] The specific preparation steps of S-(FeNiIn)LDH / IF-7 are as follows:

[0100] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 5mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0101] Example 21

[0102] The specific preparation steps of S-(FeNiIn)LDH / IF-8 are as follows:

[0103] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 40mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0104] Example 22

[0105] The specific preparation steps of S-(FeNiIn)LDH / IF-9 are as follows:

[0106] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 1mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0107] Example 23

[0108] The specific preparation steps of S-(FeNiIn)LDH / IF-10 are as follows:

[0109] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 5mg / mL Na2S solution (because sodium sulfide solution has S 2-, which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0110] Example 24

[0111] The specific preparation steps of S-(FeNiIn)LDH / IF-11 are as follows:

[0112] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 15 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0113] Example 25

[0114] The specific preparation steps of S-(FeNiIn)LDH / IF-12 are as follows:

[0115] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a 40 mg / mL NaOH solution dropwise. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0116] Example 26

[0117] The specific preparation steps of S-(FeNiIn)LDH / IF-13 are as follows:

[0118] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 0.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0119] Example 27

[0120] The specific preparation steps of S-(FeNiIn)LDH / IF-14 are as follows:

[0121] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mLH2O and 15mL ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 3.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0122] Example 28

[0123] The specific preparation steps of (FeNiCo)LDH / IF are as follows:

[0124] Weigh 0.36 mmol of cobalt acetate and 0.90 mmol of nickel acetate into a round-bottom flask, then place a piece of foam iron (1×0.5 cm), add 32.5 mL of H2O and 15 mL of ethanol, stir at 25°C for 30 min, then slowly add 2.5 mL of 20 mg / mL NaOH solution, continue stirring for 30 min, then slowly heat to 80°C, keep stirring for 2.5 h, collect the product, wash with deionized water, and dry to obtain a sample.

[0125] Example 29

[0126] The specific preparation steps of (FeNiCo)S / IF are as follows:

[0127] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 32.5mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 121mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared and used immediately. Preparation too early in advance may cause errors). Continue stirring for 30 minutes, then slowly heat to 80°C, then keep stirring for 2.5 hours, collect the product, wash with deionized water, and dry to obtain a sample.

[0128] Example 30

[0129] The specific preparation steps of (FeNiCo)S-seed / IF are as follows:

[0130] Weigh 0.36mmol of cobalt acetate and 0.90mmol of nickel acetate into a round-bottom flask, then place a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared and used immediately. Preparation too early in advance may cause errors). After stirring for 30 minutes, the product was collected, washed with deionized water, and dried to obtain a sample.

[0131] Example 31

[0132] The specific preparation steps of (FeNiIn)LDH / IF are as follows:

[0133] Weigh 1.26 mmol of nickel acetate into a round-bottom flask, then place a piece of iron foam (1 x 0.5 cm), add 28.5 mL of H₂O and 15 mL of ethanol, and then add 4 mL of a 5 mg / mL indium chloride solution. Stir at 25°C for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution dropwise. Continue stirring for 30 minutes, then slowly raise the temperature to 80°C. Then, maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0134] Example 32

[0135] The specific preparation steps of (FeCoIn)LDH / IF are as follows:

[0136] Weigh 1.26 mmol of cobalt acetate into a round-bottom flask, then place a piece of iron foam (1 x 0.5 cm), add 28.5 mL of H₂O and 15 mL of ethanol, and then add 4 mL of a 5 mg / mL indium chloride solution. Stir at 25°C for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution dropwise. Continue stirring for 30 minutes, then slowly raise the temperature to 80°C. Then, maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0137] Example 33

[0138] The specific preparation steps of (FeCo)LDH / IF are as follows:

[0139] Weigh 1.26 mmol of cobalt acetate into a round-bottom flask, then place a piece of iron foam (1 x 0.5 cm), add 32.5 mL of H₂O and 15 mL of ethanol, and stir at 25°C for 30 minutes. Slowly add 2.5 mL of a 20 mg / mL NaOH solution dropwise. Continue stirring for 30 minutes, then slowly raise the temperature to 80°C. Maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0140] Example 34

[0141] The specific preparation steps of (FeNi)LDH / IF are as follows:

[0142] Weigh 1.26 mmol of nickel acetate into a round-bottom flask, then place a piece of iron foam (1 x 0.5 cm), add 32.5 mL of H₂O and 15 mL of ethanol, and stir at 25°C for 30 minutes. Slowly add 2.5 mL of a 20 mg / mL NaOH solution dropwise. Continue stirring for 30 minutes, then slowly raise the temperature to 80°C. Maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0143] Example 35

[0144] The specific preparation steps of S-(FeNi)LDH / IF are as follows:

[0145] Weigh 1.26mmol nickel acetate into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL H2O and 15mL ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2-, which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0146] Example 36

[0147] The specific preparation steps of S-(FeCo)LDH / IF are as follows:

[0148] Weigh 1.26mmol of cobalt acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0149] Example 37

[0150] The specific preparation steps of S-(FeCoZn)LDH / IF are as follows:

[0151] Weigh 1.26mmol of cobalt acetate and 0.14mmol of zinc acetate, put them into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0152] Example 38

[0153] The specific preparation steps of S-(FeNiZn)LDH / IF are as follows:

[0154] Weigh 1.26mmol nickel acetate and 0.14mmol zinc acetate, put them into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL H2O and 15mL ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0155] Example 39

[0156] The specific preparation steps of S-(FeNiV)LDH / IF are as follows:

[0157] Weigh 1.26mmol nickel acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL H2O and 15mL ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a solution (composed of a 20 mg / mL NaOH solution and 0.14 mmol of ammonium metavanadate). Continue stirring for 30 minutes, slowly raise the temperature to 80°C, then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0158] Example 40

[0159] The specific preparation steps of S-(FeCoV)LDH / IF are as follows:

[0160] Weigh 1.26mmol of cobalt acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 30mL of H2O and 15mL of ethanol, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2-, which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors). Stir for 30 minutes, then slowly add 2.5 mL of a solution (composed of a 20 mg / mL NaOH solution and 0.14 mmol of ammonium metavanadate). Continue stirring for 30 minutes, slowly raise the temperature to 80°C, then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0161] Example 41

[0162] The specific preparation steps of S-(FeCoIn)LDH / IF are as follows:

[0163] Weigh 1.26mmol of cobalt acetate and put it into a round-bottom flask, then put a piece of foam iron (1×0.5cm), add 26mL of H2O and 15mL of ethanol, add 4mL of 5mg / mL indium chloride solution, stir at 25℃ for 30min, then slowly add 2.5mL of 3mg / mL Na2S solution (because sodium sulfide solution has S 2- , which is easily oxidized by O2 in the air and must be prepared immediately before use; preparing too early in advance may cause errors. Stir for 30 minutes, then slowly add 2.5 mL of a 20 mg / mL NaOH solution. Continue stirring for 30 minutes, slowly raise the temperature to 80°C, and then maintain stirring for 2.5 hours. Collect the product, wash with deionized water, and dry to obtain a sample.

[0164] First, S-doped iron nickel chromium hydroxide (S-(FeNiCr)(OH)2 / IF) electrocatalyst, S-doped iron nickel aluminum hydroxide (S-(FeNiAl)(OH)2 / IF) electrocatalyst, S-doped iron nickel copper hydroxide (S-(FeNiCu)(OH)2 / IF) electrocatalyst, S-doped iron nickel copper hydroxide (S-(FeNiCu)(OH)2 / IF) electrocatalyst, S-doped iron nickel strontium hydroxide (S-(FeNiSr)(OH)2 / IF) electrocatalyst and S-doped iron nickel manganese hydroxide (S-(FeNiMn)(OH)2 / IF) electrocatalyst were prepared. However, no matter what the doping ratio was, no two-dimensional nanosheet structure was obtained. As shown in the figure below ( Figure 1 and Figure 2 ) shows that its structure is irregular and in a state of large aggregates.

[0165] In addition, the experiment continues to explore the involvement of new metal elements (such as vanadium, zinc, indium, cobalt, etc.) in the doping of iron-nickel based catalysts. After a large number of experimental attempts, such as Figure 3As shown in the figure, a series of electrocatalytic materials with nanosheet structures were synthesized, such as S-(FeNiCo)LDH / IF, S-(FeNiIn)LDH / IF, S-(FeCoZn)LDH / IF, etc.

[0166] In order to more comprehensively investigate the effect of element doping on the overall OER performance of the catalyst, electrocatalysts with different elemental compositions were synthesized experimentally, and the OER performance of these electrocatalysts was tested in 1M KOH solution. The comparison of their overpotential and Tafel slope is shown in the figure below. Figure 4 and Figure 5 As shown. Figure 4 It can be seen that at 1000mAcm -2 At the current density, S-(FeNiCo)LDH / IF has the smallest OER overpotential (288mV) among these electrocatalysts; Figure 5 It can be seen that S-(FeNiCo)LDH / IF has the smallest Tafel slope value, indicating that the S-(FeNiCo)LDH / IF electrocatalyst has the optimal OER kinetic process.

[0167] Figure 6 This is a diagram of the preparation process of S-(FeNiCo)LDH / IF composite materials. First, the foamed iron is immersed in a mixed solution of H2O and ethanol containing cobalt acetate and nickel acetate. The foamed iron releases iron ions under acidic conditions. After adding Na2S solution, S 2- It reacts with iron, nickel, and cobalt ions, while the sulfur also reacts with O2 in the air, forming iron-cobalt-nickel sulfides on the surface of the iron foam (the iron-cobalt-nickel sulfide is denoted as (FeNiCo)S-seed, and the composite material of iron-cobalt-nickel sulfide and iron foam is denoted as (FeNiCo)S-seed / IF). Using the (FeNiCo)S-seed as the nucleation "seed," the addition of NaOH allows for continued reaction and growth, forming S-(FeNiCo)LDH / IF.

[0168] Figure 7 This is a scanning electron microscope (SEM) photograph of the (FeNiCo) S-seed / IF prepared in Example 30. It can be seen that its microscopic morphology is nano-sheet-like. Figure 8 From the XPS curve of (FeNiCo)S-seed / IF prepared in Example 30, it can be seen that the iron, cobalt and nickel therein are mainly in the +2 and +3 valences, and the sulfur mainly appears in the oxidized form.

[0169] Figure 9This is an electron microscope photograph of S-(FeNiCo)LDH / IF prepared in Example 3. It can be clearly seen that a large number of sulfur-doped iron-cobalt-nickel hydroxide nanosheets (S-(FeNiCo)LDH) grow on the surface of the foamed iron. These nanosheets are directly stacked together to form three-dimensional nanospheres.

[0170] Figure 10 is the XPS curve of S-(FeNiCo)LDH / IF prepared in Example 3. Figure 10 It can be seen that the nanosheets grown on the surface of the iron foam are primarily composed of iron, cobalt, nickel, sulfur, and oxygen. Iron, cobalt, and nickel are primarily in the +2 and +3 valence states, while sulfur is primarily in the oxidized state. The molar percentages of iron, cobalt, nickel, and sulfur are 55.29%, 37.22%, 7.06%, and 0.44%, respectively (Table 1). After the introduction of sulfur, the average valence of nickel decreased from 2.72 to 2.30 (Table 2). The average valence of cobalt changed slightly, from 2.61 to 2.51 (Table 3). The average valence of iron increased from 2.29 to 2.65 (Table 4). This indicates that the introduction of sulfur alters the electronic structure of the prepared sample, with electrons primarily flowing from Fe to Ni. This change in electronic structure enhances the activity of active sites, leading to improved OER performance.

[0171] To investigate the role of (FeNiCo)S-seed, comparative experiments were conducted to prepare iron, cobalt, and nickel layered hydroxides ((FeNiCo)LDH). Specifically, when Na2S was not added during the preparation of S-(FeNiCo)LDH / IF, meaning no nucleation "seed" was introduced, the resulting product micromorphology was significantly different. Figure 11 This is an electron microscope photo of the (FeNiCo)LDH / IF prepared in Example 28. Figure 11 (b) It can be clearly seen that the number of nanosheets grown without nucleation "seeds" is small and the area of ​​the nanosheets is small. Therefore, (FeNiCo)S-seed promotes the growth of (FeNiCo)LDH. In addition, Figure 11 (d) The lattice spacing of 0.259 nm corresponds to the (012) plane of (FeNiCo)LDH. After the introduction of nucleation "seeds" during the preparation process, the lattice spacing becomes 0.266 nm ( Figure 9 (e) This is mainly because the radius of S atoms is larger than that of O atoms. After the introduction of larger atoms, the lattice spacing increases slightly. This also shows that S atoms are uniformly doped into the lattice of (FeNiCo)LDH. Figure 7 Figure 3 is S-(FeNiCo)LDH / IF prepared with different Na2S dosages. It can be seen that when the Na2S dosage is 7.5 and 10 mg, the thickness of the nanosheets is smaller.

[0172] Using the same method, sulfur-doped iron-nickel-indium layered hydroxide ((S-(FeNiIn)LDH / IF)) was also prepared. Figure 13 This is an electron microscope photograph of the S-(FeNiIn)LDH / IF prepared in Example 15, which clearly shows a two-dimensional nanosheet structure.

[0173] Table 1 Mass percentage of each element in nanosheet S-(FeNiCo)LDH and (FeNiCo)LDH (measured by ICP-MS)

[0174] Sample S (wt%) Fe (wt%) Co (wt%) Ni (wt%) S-(FeNiCo)LDH 0.44 55.29 7.06 37.22 (FeNiCo)LDH - 75.25 6.09 18.66

[0175] Table 2 Valence of Ni in S-(FeNiCo)LDH / IF and (FeNiCo)LDH / IF

[0176] Sample <![CDATA[Ni 2+ ]]> <![CDATA[Ni 3+ ]]> Average states (FeNiCo)LDH / IF 28.27％ 71.73％ 2.72 S-(FeNiCo)LDH / IF 69.97％ 30.03％ 2.30

[0177] Table 3 Valence of Co in S-(FeNiCo)LDH / IF and (FeNiCo)LDH / IF

[0178] Sample <![CDATA[Co 2+ ]]> <![CDATA[Co 3+ ]]> Average states (FeNiCo)LDH 39.01％ 60.99％ 2.61 S-(FeNiCo)LDH 49.15％ 50.85％ 2.51

[0179] Table 4 Valence of Fe in S-(FeNiCo)LDH / IF and (FeNiCo)LDH / IF

[0180]

[0181] Electrochemical performance of S-(FeNiM)LDH / IF(M=Co,In):

[0182] First, the OER performance of S-(FeNiCo)LDH / IF prepared in Example 3 was tested. Under the condition of 1M KOH as electrolyte, the linear sweep voltammetry (LSV) curve measured by three-electrode electrochemical workstation is as follows: Figure 14 As shown in (a), the working electrode is S-(FeNiCo)LDH / IF, the counter electrode is a platinum sheet electrode (1×2 cm), and the reference electrode is a Hg / HgO electrode. Figure 14 As can be seen from (a), the S-(FeNiCo)LDH / IF prepared in Example 3 has the best OER performance. The current density it generates in the entire scanning range is larger than that generated by the other three samples. The current density of S-(FeNiCo)LDH / IF, S-(FeNiIn)LDH / IF, (FeNiCo)LDH / IF and (FeNiIn)LDH / IF is 1000 mA cm -2 The corresponding overpotential is Figure 14As shown in (b), it can be seen that when the current density reaches 1000 mA cm -2 When the overpotential of S-(FeNiCo)LDH / IF is only 288mV, under the same test conditions, the overpotential of S-(FeNiIn)LDH / IF, (FeNiIn)LDH / IF and (FeNiCo)LDH / IF is only 288mV. -2 The corresponding overpotentials at the current density are 313, 350, and 357 mV, respectively. In comparison, the OER performance of S-(FeNiCo)LDH / IF is greatly improved. Moreover, compared with other Fe-Co-Ni-based electrocatalysts, under similar test conditions, S-(FeNiCo)LDH / IF can also be listed as one of the catalysts with better OER performance (Table 5). Figure 14 (c) is the Tafel slope diagram corresponding to the OER reaction of the samples prepared in Examples 3, 15, 28, and 31. It can be seen that the Tafel slope of the electrocatalyst S-(FeNiCo)LDH / IF among the prepared samples is the smallest, which is 23.9 mV dec. -1 The smaller the Tafel slope, the faster the current density increases, indicating faster catalyst kinetics and better catalytic activity. Figure 14 (d) is a histogram of the electrocatalytic activity area (ECSA) of the samples prepared in Examples 3 and 28. It can be seen that the ECSA of S-(FeNiCo)LDH / IF is 2.90 times that of (FeNiCo)LDH / IF. The LSV curves of the S-(FeNiCo)LDH / IF prepared in Example 3 before and after 1000 scans by cyclic voltammetry (CV) are shown in FIG. Figure 14 (e) is used to test the stability of the catalyst. Figure 14 As can be seen in (e), there is almost no difference between the curves before and after scanning 1000 times, indicating that its stability is good. Figure 14 (f)), the current density at 325 mV only decreased by 8%, further confirming its good stability.

[0183] Table 5 Comparison of OER performance of S-(FeNiCo)LDH / IF obtained in Example 3 and currently reported electrocatalysts under similar conditions

[0184]

[0185]

[0186] like Figure 15 (a) Figure 15 As shown in (b), the HER performance of S-(FeNiIn)LDH / IF prepared in Example 15 is the best, and the HER performance is the best when the current density reaches 100 mA·cm-2 When the overpotential of S-(FeNiIn)LDH / IF is only 174mV, under the same test conditions, the overpotential of S-(FeNiCo)LDH / IF, (FeNiIn)LDH / IF and (FeNiCo)LDH / IF is only 174mV. -2 The corresponding overpotentials at the current density are 210, 217, and 317 mV, respectively. In comparison, the HER performance of S-(FeNiIn)LDH / IF is significantly improved. Figure 15 (c) is the Tafel slope histogram of the four samples. It can be seen that the Tafel slope is 144.9mV dec for (FeNiCo)LDH / IF. -1 It dropped sharply to 48.9mV dec for S-(FeNiIn)LDH / IF -1 , indicating that the HER kinetics of the catalyst is much faster. The CV curve of S-(FeNiIn)LDH / IF prepared in Example 15 ( Figure 15 (d)) shows that the catalyst has good stability.

[0187] Finally, a two-electrode water electrolysis device was constructed using the S-(FeNiCo)LDH / IF prepared in Example 3 as the anode and the S-(FeNiIn)LDH / IF prepared in Example 15 as the cathode to examine the water electrolysis performance of the electrocatalysts described in this application. The electrolyte was 1 M KOH. Figure 16 (a) is the LSV curve of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF, S-(FeNiCo)LDH / IF||S-(FeNiCo)LDH / IF and (FeNiCo)LDH / IF||(FeNiCo)LDH / IF. Figure 16 (a) It can be seen that S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF has the best water electrolysis performance. -2 The potential of S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF is only 1.74 V, while under the same test conditions, (FeNiCo)LDH / IF||(FeNiCo)LDH / IF is 500 mA·cm -2 The corresponding potential at the current density is 1.99 V. In comparison, the electrolytic water performance of S-(FeNiIn)LDH / IF has been greatly improved ( Figure 16(b)). In addition, as shown in Table 6, the S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF electrolytic water system requires an ultra-low voltage of 1.74 V to achieve a current density of up to 500 mA cm-1 compared with the recently reported electrolytic water catalysts. -2 . Figure 16 (c) is a comparison of the actual and theoretical values ​​of H2 and O2 generated by S-(FeNiCo)LDH / IF||S-(FeNiIn)LDH / IF. It can be seen that the amount of H2 and O2 actually collected is close to 2:1, and the Faradaic efficiency is almost close to 100%. Its electrolysis water IT curve proves its good stability ( Figure 16 (d)).

[0188] Table 6 Different catalytic materials at 500 mA·cm -2 Comparison of overall water splitting activity at different current densities

[0189]

[0190] The above description is merely a preferred embodiment of the present invention and is intended to be illustrative rather than restrictive of the present invention. Those skilled in the art will appreciate that many changes, modifications, and even equivalents may be made to the present invention within the spirit and scope of the claims, all of which fall within the scope of protection of the present invention.

Claims

1. A method for preparing an S-(FeNiM)LDH / IF electrocatalyst, characterized in that: The following steps are involved: S1, put cobalt acetate or indium chloride, nickel acetate and iron foam into a round-bottom flask, add H2O and ethanol, stir in an oil bath at 25°C for 30 minutes, and then slowly add Na2S solution dropwise; S2, stirring the solution obtained in step S1 for 30 min, and then slowly adding dropwise a mixed solution consisting of NaOH and H2O; S3, continue stirring the solution obtained in step S2 for 30 minutes, then stir it at 80°C and keep it warm for 0.5 to 3.5 hours, collect the product, wash it with H2O, and obtain a sample after drying. If cobalt acetate is used in step S1, S-(FeNiCo)LDH / IF electrocatalyst will be obtained, and if indium chloride is used, S-(FeNiIn)LDH / IF electrocatalyst will be obtained.

2. The method for preparing a S-(FeNiM)LDH / IF electrocatalyst according to claim 1, wherein: In step S1, the amount of cobalt acetate or indium chloride is 0.5-1.26 mmol, the amount of nickel acetate is 0.5-1.26 mmol, the foam iron is a piece of 1×0.5 cm foam iron, the amount of H2O is 10-45 mL, the amount of ethanol is 5-40 mL, the amount of Na2S in the Na2S solution is 2.5-12.5 mg, and the amount of H2O is 2.5 mL.

3. The method for preparing a S-(FeNiM)LDH / IF electrocatalyst according to claim 1, wherein: In step S1, the amount of cobalt acetate or indium chloride is 0.36 mmol, the amount of nickel acetate is 0.90 mmol, the foam iron is a piece of 1×0.5 cm foam iron, the amount of H2O is 35 mL, the amount of ethanol is 15 mL, the amount of Na2S in the Na2S solution is 7.5 mg, and the amount of H2O is 2.5 mL.

4. The method for preparing a S-(FeNiM)LDH / IF electrocatalyst according to claim 1, wherein: In step S2, the amounts of NaOH and H2O in the mixed solution of NaOH and H2O are 30-100 mg and 2.5 mL, respectively.

5. The method for preparing a S-(FeNiM)LDH / IF electrocatalyst according to claim 1, wherein: In step S2, the amounts of NaOH and H2O in the mixed solution of NaOH and H2O are 50 mg and 2.5 mL, respectively.

6. The method for preparing a S-(FeNiM)LDH / IF electrocatalyst according to claim 1, wherein: In step S3, the holding temperature is 80° C. and the holding time is 2.5 h.

7. An S-(FeNiM)LDH / IF electrocatalyst prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The M is Co or In, and the electrocatalyst is a three-dimensional layered nanosheet structure.

8. Use of the S-(FeNiM)LDH / IF electrocatalyst as claimed in claim 7 in OER, HER and overall water splitting reactions.

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