Nanosheet flower-like ni-fe-o-s / nf catalysts and methods of making same

Abstract

The application belongs to the field of chemical industry, and particularly relates to a kind of nanosheet flower cluster Ni-Fe-O-S / NF catalyst and its preparation method.The application is a kind of nanosheet flower cluster Ni-Fe-O-S / NF electrode material prepared by ZIF-67 / NF derivation strategy, that is, the Ni-Fe-O-S / NF of the application is etched ZIF-67 while directly in situ grown on the conductive nickel foam substrate;The high-activity bifunctional electrocatalyst mainly involves Ni, Fe, S, O transition metal.The Ni-Fe-O-S / NF catalyst of the application shows good bifunctional catalytic activity when applied to 1.0M KOH electrolytic water.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering, and specifically relates to a nano-flower-like Ni-Fe-OS / NF catalyst and its preparation method. Background Technology

[0002] The continued use of traditional fossil fuels has led to increasingly serious environmental pollution and energy shortages. Finding an environmentally friendly and sustainable energy source to gradually replace traditional fossil fuels has become a major focus of attention. Hydrogen energy, with its high energy density, environmental friendliness, and renewability, is considered one of the most ideal energy sources for the future. Among various hydrogen production technologies, water electrolysis can rapidly and with zero pollution produce high-purity hydrogen, making it a green hydrogen production technology. However, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) processes involved in water electrolysis involve multiple electron transfer steps, leading to an increased energy barrier and high overpotential. To accelerate the reaction process and reduce the overpotential, catalysts are usually introduced. Noble metal-based materials (such as Pt-, Ru / Ir-, etc.) are a class of highly efficient electrochemical catalysts widely used in the field of water electrolysis for hydrogen production. However, noble metal catalysts generally exhibit only single HER or OER activity, and their reserves are scarce and unevenly distributed geographically, failing to meet the needs of large-scale industrial applications. Developing bifunctional electrocatalysts can simplify electrode material preparation processes, reduce costs, and play a positive and important role in optimizing electrolyzer structures. Therefore, it is of great significance to develop inexpensive and highly active bifunctional electrocatalytic materials.

[0003] In the research of non-precious metal electrocatalysts, nickel-based sulfide catalysts have attracted significant attention due to their diverse chemical compositions and tunable electronic environments. However, nickel-based sulfide catalysts generally exhibit poor single HER or OER catalytic activity. Introducing other HER and OER catalytically active substances into nickel-based sulfides to form heterogeneous catalysts can activate active sites and thus enhance HER and OER activity, representing one of the most direct and effective approaches to achieving bifunctional catalytic activity.

[0004] Most bifunctional electrocatalysts are currently constructed through stepwise assembly. This method is not only cumbersome in its preparation, but also risks introducing materials that may obscure the catalyst's active sites, leading to a significant reduction in final catalyst activity. For example, patent CN113584521A discloses a branch-shaped heterostructure bifunctional electrocatalyst constructed through stepwise assembly. First, NiMoO4 nanorods are synthesized on a nickel foam substrate, followed by phosphating to form NiMo-P nanorods. Then, CoFe-LDH nanosheets are deposited on the NiMo-P nanorods using electrodeposition. This three-step process forms a multi-component bifunctional electrocatalyst. The resulting NiMo-P@CoFe-LDH electrocatalyst exhibits certain electrocatalytic activity and stability. However, the complex preparation process and stepwise assembly technique prevent the catalyst from achieving its full catalytic efficiency.

[0005] Therefore, it is necessary to develop a holistic construction strategy for the direct synthesis of heterogeneous catalytic materials with differences in HER and OER activities. Numerous studies have shown that NiS2 and FeNi2S4 possess good HER catalytic activity. Meanwhile, NiS and NiO, as active species for OER, have also attracted widespread attention. Patent publication CN 110918103 A discloses a three-phase NiS-NiS2-Ni3S4 electrocatalyst, characterized by an independent NiS-NiS2-Ni3S4 composed of a three-phase nickel sulfide outer layer and a three-phase nickel sulfide inner layer. This constructed nickel sulfide composite electrocatalyst exposes abundant active sites, improves interfacial electron transport, and promotes the hydrogen evolution reaction. However, the HER activity of this simply combined three-phase NiS-NiS2-Ni3S4 catalyst remains unsatisfactory, and researchers have not further explored the oxygen evolution reaction.

[0006] Therefore, it is of great significance to develop an overall preparation strategy to directly generate nickel-based sulfide heterogeneous electrocatalysts with HER and OER activities through rational design, and to utilize the synergistic effect between different components and the improved electronic environment to achieve highly efficient bifunctional catalytic activity of the catalyst. Summary of the Invention

[0007] The main technical problem solved by this invention is to provide a nano-flower-like Ni-Fe-OS / NF catalyst and its preparation method.

[0008] To address the aforementioned technical problems, this invention provides a method for preparing a nano-flower-like Ni-Fe-OS / NF catalyst, comprising the following steps:

[0009] 1) Clean NF is obtained by washing and drying the nickel foam (NF) using conventional washing and drying methods;

[0010] 2) Dissolve the surfactant in deionized water to obtain solution A (surfactant solution).

[0011] The organic ligand is dissolved in liquid alcohol to obtain solution B (organic ligand solution one).

[0012] Dissolve the cobalt source in liquid alcohol to obtain solution C (cobalt source solution);

[0013] The clean NF obtained in step 1) is first placed in solution A (surfactant solution) and ultrasonically activated to obtain surface-activated NF;

[0014] After surface activation, NF was placed in solution B (organic ligand solution one) and immediately solution C (cobalt source solution) was added. After uniform stirring (stirring time was 0.5-1.5h), it was allowed to grow at room temperature for 11-13h. After washing, it was dried (baked) to obtain ZIF-67 / NF precursor.

[0015] The weight ratio of the organic ligand in solution B to the cobalt source in solution C is 3.2–3.4:1.4–1.5.

[0016] 3) Dissolve the organic ligand in liquid alcohol to obtain solution D (organic ligand solution two);

[0017] The nickel source and the iron source are dissolved in deionized water to obtain solution E (nickel source / iron source mixture); the molar ratio of nickel source to iron source is 2.5:1.4-1.6.

[0018] After mixing and stirring solutions D and E, the ZIF-67 / NF precursor obtained in step 2) was added, and then the mixture was transferred to a high-pressure reactor and allowed to stand for 40-80 min. Then, it was reacted at 120±10℃ for 6±1 h. After the reaction was completed, it was washed to obtain Ni-FeLDH / NF (nanosheet Ni-Fe hydroxide).

[0019] When the nickel source in solution E is 2.5 mmol, the organic ligand in solution D is 1.6–1.7 g;

[0020] 4) The Ni-Fe LDH / NF obtained in step 3) is pyrolyzed at 600-900℃ for 2±0.5h under inert gas protection and naturally cooled to room temperature to obtain Ni-Fe-O / NF;

[0021] 5) Under inert gas protection, using sulfur powder as the sulfur source (the amount of sulfur powder is 0.1-0.3g), the Ni-Fe-O / NF obtained in step 4) is subjected to gas sulfidation heat treatment.

[0022] The heat treatment temperature is 150–350℃ and the heat treatment time is 0.5–1.5 h (preferably 300℃, 1 h) to obtain a nano-flower-like Ni-Fe-OS / NF catalyst (heterogeneous Ni-Fe-OS / NF target sample).

[0023] An improvement to the preparation method of the nanosheet flower cluster Ni-Fe-OS / NF catalyst of the present invention:

[0024] The surfactant is sodium polystyrene sulfonate;

[0025] The organic ligand is methylimidazole or dimethylimidazole;

[0026] The cobalt source is cobalt nitrate;

[0027] The nickel source is nickel nitrate;

[0028] The iron source is ferric nitrate;

[0029] The sulfur source is sulfur powder.

[0030] As a further improvement to the preparation method of the nanosheet flower cluster Ni-Fe-OS / NF catalyst of the present invention:

[0031] The liquid alcohol is methanol;

[0032] The inert gas is argon.

[0033] As a further improvement to the preparation method of the nanosheet flower cluster Ni-Fe-OS / NF catalyst of the present invention:

[0034] The ultrasonic activation time in step 2) is 50-70 min.

[0035] As a further improvement to the preparation method of the nanosheet flower cluster Ni-Fe-OS / NF catalyst of the present invention:

[0036] Step 4) The heating rate is 9–11 °C / min.

[0037] Step 5) The heating rate is 4-6℃ / min.

[0038] As a further improvement to the preparation method of the nanosheet flower cluster Ni-Fe-OS / NF catalyst of the present invention:

[0039] The inert protective gas is argon.

[0040] As a further improvement to the preparation method of the nanosheet flower cluster Ni-Fe-OS / NF catalyst of the present invention:

[0041] Dissolve 40 mg of sodium polystyrene sulfonate in 50 ± 5 mL of deionized water to obtain solution A (surfactant solution);

[0042] Dissolve 3.28 g of dimethylimidazole / methylimidazole in 50 ± 5 mL of methanol to obtain solution B (organic ligand solution one);

[0043] Dissolve 1.45g of cobalt nitrate hexahydrate in 50±5mL of methanol to obtain solution C (cobalt source solution);

[0044] Dissolve 1.64 g of dimethylimidazole in 10 ± 1 mL of methanol to obtain solution D (organic ligand solution II);

[0045] Dissolve 2.5 mmol nickel nitrate hexahydrate and 1.5 mmol ferric nitrate hexahydrate in 20 ± 2 mL of deionized water to obtain solution E (nickel source / iron source mixture);

[0046] 0.2g of sulfur powder was used as the sulfur source.

[0047] Note: NF cut to 2×3cm 2 size.

[0048] The present invention also provides a nano-flower cluster-shaped Ni-Fe-OS / NF catalyst prepared by any of the above methods.

[0049] This invention relates to a nano-flower-like Ni-Fe-OS / NF electrode material prepared using a ZIF-67 / NF derivatization strategy. This highly active bifunctional electrocatalyst primarily involves transition metals such as Ni, Fe, S, and O. The Ni-Fe-OS / NF of this invention is produced by etching ZIF-67 while simultaneously growing it directly in situ on a conductive nickel foam substrate.

[0050] The nanosheet-like Ni-Fe-OS / NF catalyst of this invention (for high-efficiency total water splitting multiphase nanosheet-like Ni-Fe-OS / NF catalyst) mainly overcomes the problems of single catalytic activity, few active sites, and poor stability in existing technologies. More importantly, it avoids the masking of active sites and poor conductivity caused by the coating step, and also solves the problem of active site destruction caused by stepwise synthesis in the conventional preparation of bifunctional catalysts. The preparation method of this invention is ingenious, simple, and effective in promoting the in-situ growth of the multiphase catalyst on a conductive substrate (nickel foam), enhancing the catalyst's conductivity; at the same time, it directly generates a multiphase electrocatalytic material with both HER and OER activities, producing a synergistic effect and effectively activating the catalyst's active sites. In addition, the in-situ growth of the multiphase Ni-Fe-OS / NF catalyst in this invention, coupled with the synergistic effect of the multiphase, simultaneously regulates the electronic configuration, accelerates electron transfer, and enhances conductivity. The Ni-Fe-OS / NF catalyst exhibits excellent HER and OER activities and total water splitting performance, providing a valuable reference for the preparation of high-efficiency bifunctional electrocatalysts.

[0051] The Ni-Fe-OS / NF catalyst of the present invention, with optimized electronic configuration, exhibits excellent electrochemical activity in alkaline electrolytes, at 10 mA cm⁻¹. -2 At the specified current density, the HER overpotential is only 92mV, and the OER overpotential is as low as 90mV. Furthermore, only a 1.49V full-cell electrolysis voltage is required to achieve a 10mA cm⁻¹. -2 The Ni-Fe-OS / NF catalyst exhibits high current density and stable operation time exceeding 150 hours, significantly optimizing existing Pt / C-IrO2 noble metal electrocatalysts. The excellent water electrolysis catalytic activity of the Ni-Fe-OS / NF catalyst provides a simple and effective synthetic strategy for the preparation of duplex electrocatalysts.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] (1) This invention employs a ZIF-67 / NF etching-derivative strategy to directly generate a Ni-Fe-OS / NF catalyst with multiphase components and a unique nanosheet flower-like structure. The designed ZIF-67 / NF etching-derivative strategy provides advantageous structural features, making it easier for the catalyst material to grow in situ on NF. Furthermore, the etching and regeneration processes effectively regulate the electronic environment of the catalyst, improving its catalytic activity. In addition, the introduction of Ni and Fe sources during the solvothermal process affects the nickel oxidation process, leading to the promotion of multiphase catalyst generation after the subsequent sulfidation step. The high-temperature pyrolysis of hydroxide causes hydroxyl decomposition, generating a large amount of water vapor, resulting in a porous structure in the nanosheets. Reasonable pyrolysis control yields a beneficial porous nanosheet structure, enhancing electrolyte diffusion and increasing the contact between the catalyst and the electrolyte. In the final high-temperature sulfidation process, through screening and precise control of the sulfidation conditions, not only is the porous morphology of the Ni-Fe-OS / NF catalyst preserved, but multiphase components of NiS2, NiS, FeNi2S4, and NiO are also directly generated. Figure 1 The favorable heterogeneous components and morphological structure of the Ni-Fe-OS / NF catalyst lead to the exposure of abundant active sites and a large electrochemical active area. The overall synthesis strategy of the heterogeneous Ni-Fe-OS / NF catalyst designed in this invention is simple and effective, and suitable for the direct generation of heterogeneous catalysts. By adopting the ZIF-67 / NF derivatization strategy, controlling the relative addition amount of nickel-iron source, and parameters such as pyrolysis temperature and sulfidation conditions, the generation of a heterogeneous nanosheet flower-like Ni-Fe-OS / NF catalyst with high bifunctional catalytic activity was successfully achieved.

[0054] (2) The Ni-Fe-OS / NF catalyst of this invention exhibits excellent bifunctional catalytic activity when applied to the electrolysis of water using 1.0M KOH. The Ni-Fe-OS / NF catalyst only requires OER and HER overpotentials of 90 and 92 mV to reach 10 mA cm⁻¹.-2 The slopes of Taffy are 43 and 95 mV dec, respectively. -1 Furthermore, it can operate stably for over 150 hours without catalyst shedding or significant morphological deformation. When using the Ni-Fe-OS / NF catalyst for complete water splitting tests, it exhibits a low complete water splitting cell voltage of 1.49V at 10 mA cm⁻¹. -2 At the same current density, the stability performance remained stable for 150 hours, maintaining a linear voltage curve with no significant catalyst detachment. Overall, its performance was significantly superior to noble metal-based PtC and IrO2 electrocatalysts.

[0055] In summary, this invention utilizes Ni and Fe etching to grow Ni-Fe LDH / NF on ZIF-67 / NF, followed by pyrolysis under an argon atmosphere to obtain Ni-Fe-O / NF, and finally, inert gas sulfidation treatment to directly synthesize a heterogeneous Ni-Fe-OS / NF catalyst. The advantages of this invention lie in its simple catalyst preparation process, readily available raw materials, and, more importantly, the direct synthesis of a heterogeneous electrocatalyst with a specific porous nanosheet-like cluster structure. Furthermore, the catalyst's electronic environment can be favorablely controlled. In a 1.0 M KOH electrolyte, the Ni-Fe-OS / NF catalyst exhibits excellent HER and OER catalytic activity, as well as overall water splitting catalytic performance. This provides valuable inspiration for the development of directly synthesized heterogeneous, highly active bifunctional electrocatalysts. Attached Figure Description

[0056] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0057] Figure 1 The image shows the XRD pattern of the Ni-Fe-OS / NF catalyst (including the products obtained in each step) prepared in Example 1 of this invention.

[0058] according to Figure 1 It can be seen that the prepared Ni-Fe-OS / NF catalyst exhibits a multiphase composition, specifically including: NiS (PDF#86-2281), NiS2 (PDF#73-0574), FeNi2S4 (PDF#47-1740) and NiO (PDF#47-1049).

[0059] Figure 2 The OER:LSV diagram of the Ni-Fe-OS / NF catalyst (including the products obtained in each step) prepared in Example 1 of this invention;

[0060] according to Figure 2It can be seen that the prepared heterogeneous Ni-Fe-OS / NF catalyst exhibits excellent OER performance. It is worth noting that the OER performance of the heterogeneous Ni-Fe-OS / NF catalyst prepared in this invention is significantly better than that of the noble metal IrO2 catalyst.

[0061] Figure 3 The HER:LSV diagram of the Ni-Fe-OS / NF catalyst (including the products obtained in each step) prepared in Example 1 of this invention;

[0062] according to Figure 3 It can be seen that the prepared heterogeneous Ni-Fe-OS / NF catalyst exhibits competitive HER catalytic activity.

[0063] Figure 4 This is a complete water splitting diagram of the Ni-Fe-OS / NF catalyst (including the products obtained in each step) prepared in Example 1 of this invention;

[0064] according to Figure 4 It can be seen that the prepared heterogeneous Ni-Fe-OS / NF catalyst exhibits excellent overall water splitting performance at 10 mA cm⁻¹. -2 At the current density, the voltage of the water-splitting cell is as low as 1.49V. In addition, the prepared heterogeneous Ni-Fe-OS / NF catalyst has a water-splitting performance that far exceeds that of the PtC||IrO2 noble metal catalyst. Detailed Implementation

[0065] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto:

[0066] The stirring speed is 1200±200 rpm.

[0067] Example 1

[0068] (1) Cut the nickel foam (NF) into 2×3cm pieces. 2 To determine the size, the NF was first ultrasonically cleaned for 60 minutes with 3.0M hydrochloric acid, then ultrasonically cleaned for 30 minutes each with ethanol and deionized water, and finally dried overnight (approximately 12 hours) in a vacuum drying oven at 70°C to obtain clean NF.

[0069] (2) Under normal stirring conditions: 40 mg of sodium polystyrene sulfonate was dissolved in 50 mL of deionized water to obtain a surfactant solution (solution A); 3.28 g of dimethylimidazole was dissolved in 50 mL of methanol to obtain an organic ligand solution (solution B); 1.45 g of cobalt nitrate hexahydrate was dissolved in 50 mL of methanol to obtain a cobalt source solution (solution C).

[0070] The clean NF obtained in step (1) is first placed in solution A to achieve ultrasonic surface activation for 1 hour to obtain surface-activated NF;

[0071] After surface activation, NF was placed in solution B and immediately added to solution C. The mixture was stirred vigorously for 30 min, then allowed to grow at room temperature for 12 h. After washing (rinsing three times with methanol and deionized water respectively), it was dried overnight in a vacuum oven at 70 °C to obtain the ZIF-67 / NF precursor.

[0072] (3) Under normal stirring conditions: 1.64 g of dimethylimidazole was dissolved in 10 mL of methanol to obtain organic ligand solution two (solution D); 2.5 mmol of nickel nitrate hexahydrate and 1.5 mmol of ferric nitrate hexahydrate were dissolved in 20 mL of deionized water to obtain nickel source / iron source mixture (solution E);

[0073] After thoroughly mixing and stirring solutions D and E, the ZIF-67 / NF precursor obtained in step (2) was added, and then the mixture was transferred to a high-pressure reactor and allowed to stand for 60 min. Then, it was reacted at 120 °C for 6 h. After the reaction was completed, the mixture was washed (rinsed three times with methanol and deionized water respectively), and then dried overnight at 70 °C in a vacuum drying oven to obtain nanosheet Ni-Fe hydroxide (Ni-FeLDH / NF).

[0074] (4) The Ni-Fe LDH / NF obtained in step (3) above is heated to 600℃ under Ar gas for 2h and then naturally cooled to room temperature to obtain Ni-Fe-O / NF;

[0075] The heating rate is 10℃ / min.

[0076] (5) Under Ar gas protection, using sulfur powder as sulfur source, the Ni-Fe-O / NF obtained in step (4) is subjected to a separate gas sulfidation reaction.

[0077] That is, at a heating rate of 5℃ / min, the Ni-Fe-O / NF obtained in step (4) is heated together with 0.2g of sulfur powder to 300℃ and then heat-treated at 300℃ for 1h, and finally the multiphase Ni-Fe-OS / NF electrocatalyst (nanoplastic flower cluster Ni-Fe-OS / NF catalyst) is obtained directly.

[0078] Experiment 1: Following conventional detection methods, the heterogeneous Ni-Fe-OS / NF electrocatalyst prepared in Example 1 only requires OER and HER overpotentials of 90 and 92 mV respectively in 1.0 MKOH to reach 10 mA cm⁻¹. -2 Current density, and at 10 mA cm -2 The voltage of the fully electrolyzed water cell is as low as 1.49V.

[0079] The ZIF-67 / NF precursor obtained in step (2) of Example 1, the Ni-Fe LDH / NF obtained in step (3), and the Ni-Fe-O / NF obtained in step (4) were tested according to the method in Experiment 1, and the results are shown in Table 1 below.

[0080] Table 1

[0081]

[0082] Comparative Example 1 Series

[0083] Compared to Example 1, the amounts of nickel nitrate hexahydrate and ferric nitrate hexahydrate in step (3) of "dissolving 2.5 mmol nickel nitrate hexahydrate and 1.5 mmol ferric nitrate hexahydrate in 20 mL deionized water" were changed as shown in Table 2 below; the rest remained the same as in Example 1, thus obtaining the corresponding comparative examples 1-1 to 1-5. The results were obtained by testing according to the method of Experiment 1, as shown in Table 2 below.

[0084] Table 2

[0085]

[0086] Comparative Example 2 Series

[0087] Compared to Example 1, step (4) "pyrolysis at 600℃ for 2 hours" was changed to the pyrolysis temperature and pyrolysis time as shown in Table 3 below, while the rest remained the same as in Example 1, thus obtaining the corresponding Comparative Examples 2-1 to 2-3. The performance was tested according to the method of Experiment 1, and the results are shown in Table 3 below.

[0088] Table 3

[0089]

[0090] Comparative Example 3 Series

[0091] Compared to Example 1, the "0.2g sulfur powder" in step (5) was replaced with the amount of sulfur powder described in Table 4 below, while the rest remained the same as in Example 1, thus obtaining the corresponding Comparative Examples 3-1 to 3-5. The results were obtained by testing according to the method in Experiment 1, as shown in Table 4 below.

[0092] Table 4

[0093]

[0094] Comparative Example 4 Series

[0095] Compared to Example 1, the "heat treatment at 300°C for 1 hour" in step (5) was changed to the heat treatment temperature and time as shown in Table 5 below, while the rest remained the same as in Example 1, thus obtaining the corresponding Comparative Examples 4-1 to 4-4. The performance was tested according to the method of Experiment 1, and the results are shown in Table 5 below.

[0096] Table 5

[0097]

[0098]

[0099] Comparative Example 5: Step (2) of Example 1 was omitted, i.e., the preparation of the ZIF-67 / NF precursor was omitted, and the ZIF-67 / NF precursor in step (3) was replaced with clean NF. The rest remained the same as in Example 1. The electrocatalyst was tested according to the method described in Experiment 1, and the obtained electrocatalyst was measured at 10 mA cm⁻¹. -2 At current density, an overpotential of 147 mV OER and 167 mV HER were observed.

[0100] Finally, it should be noted that the above examples are merely some specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments and many variations are possible. All variations that can be directly derived or conceived by those skilled in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a nanosheet-like cluster-shaped Ni-Fe-OS / NF catalyst, characterized in that: The preparation of nano-flower-like Ni-Fe-OS / NF catalysts via a ZIF-67 / NF derivatization strategy includes the following steps: 1) The nickel foam is cleaned and dried to obtain clean NF; 2) Dissolve the surfactant in deionized water to obtain solution A. The organic ligand was dissolved in a liquid alcohol to obtain solution B. Dissolve the cobalt source in liquid alcohol to obtain solution C; The clean NF obtained in step 1) is first placed in solution A and ultrasonically activated to obtain surface-activated NF; After surface-activated NF was placed in solution B, solution C was immediately added and stirred evenly. The mixture was then allowed to grow at room temperature for 11-13 hours. After washing and drying, ZIF-67 / NF precursor was obtained. The weight ratio of the organic ligand in solution B to the cobalt source in solution C is 3.2~3.4:1.4~1.

5. 3) Dissolve the organic ligand in liquid alcohol to obtain solution D; The nickel source and the iron source are dissolved in deionized water to obtain solution E; the molar ratio of nickel source to iron source is 2.5:1.4~1.

6. After mixing and stirring solutions D and E, the ZIF-67 / NF precursor obtained in step 2) was added, and then the mixture was transferred to a high-pressure reactor and allowed to stand for 40-80 min. Then it was reacted at 120 ±10℃ for 6 ±1 h. After the reaction was completed, it was washed to obtain Ni-FeLDH / NF. The nickel source in solution E is 2.5 mmol, and the organic ligand in solution D is 1.6–1.7 g. 4) The Ni-Fe LDH / NF obtained in step 3) is pyrolyzed at 600~900 ℃ for 2±0.5 h under inert gas protection and naturally cooled to room temperature to obtain Ni-Fe-O / NF; 5) Under inert gas protection, using sulfur powder as the sulfur source, the Ni-Fe-O / NF obtained in step 4) is subjected to gas sulfidation heat treatment. The heat treatment temperature was 150~350 ℃ and the heat treatment time was 0.5~1.5h to obtain a nano-flower-like Ni-Fe-OS / NF catalyst.

2. The method for preparing the nanosheet flower cluster-shaped Ni-Fe-OS / NF catalyst according to claim 1, characterized in that: The surfactant is sodium polystyrene sulfonate; The organic ligand is methylimidazole or dimethylimidazole; The cobalt source is cobalt nitrate; The nickel source is nickel nitrate; The iron source is ferric nitrate; The sulfur source is sulfur powder.

3. The method for preparing the nanosheet-like Ni-Fe-OS / NF catalyst according to claim 2, characterized in that: The liquid alcohol is methanol; The inert gas is argon.

4. The method for preparing the nanosheet-like Ni-Fe-OS / NF catalyst according to claim 3, characterized in that: The ultrasonic activation time in step 2) is 50~70 min.

5. The method for preparing the nanosheet flower cluster-shaped Ni-Fe-OS / NF catalyst according to claim 4, characterized in that: Step 4) The heating rate is 9~11 ℃ / min. Step 5) The heating rate is 4~6 ℃ / min.

6. The method for preparing the nanosheet flower cluster-shaped Ni-Fe-OS / NF catalyst according to claim 5, characterized in that: The inert protective gas is argon.

7. The method for preparing the nanosheet-like clustered Ni-Fe-OS / NF catalyst according to any one of claims 1 to 6, characterized in that: Dissolve 40±4 mg of sodium polystyrene sulfonate in 50±5 mL of deionized water to obtain solution A; Dissolve 3.28±0.3 g of dimethylimidazole / methylimidazole in 50±5 mL of methanol to obtain solution B; Dissolve 1.45 ± 0.1 g of cobalt nitrate hexahydrate in 50 ± 5 mL of methanol to obtain solution C; Dissolve 1.64±0.1 g of dimethylimidazole in 10±1 mL of methanol to obtain solution D; Dissolve 2.5 mmol nickel nitrate hexahydrate and 1.5 mmol ferric nitrate hexahydrate in 20±2 mL of deionized water to obtain solution E; 0.2 g of sulfur powder was used as the sulfur source.

8. The nano-flower cluster-shaped Ni-Fe-OS / NF catalyst prepared by any one of claims 1 to 7.

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