ZnS modified s-doped fe-n-c catalyst and preparation method and application thereof

Abstract

This invention discloses a ZnS-modified S-doped Fe-N-C catalyst, its preparation method, and its applications, belonging to the field of electrocatalytic materials and energy conversion technology. Using metal sulfate as a single precursor, this invention employs a one-step in-situ sulfidation strategy to simultaneously construct Fe-N4 active sites, dope S atoms, and generate ZnS nanoparticles in situ via pyrolysis under nitrogen protection, thus preparing a ZnS@Fe-NSC structured catalyst. This material exhibits high CO selectivity, low overpotential, and excellent long-term stability. The ZnS nanoparticles act as electron donors, regulating the electronic structure of the Fe center, enhancing the Fe-N coordination bond strength, effectively inhibiting Fe dissolution, and improving the CO2 reduction reaction kinetics and catalyst durability. This invention features a single precursor, simplified process, and controllable structure, showing broad application prospects in electrocatalytic CO2 resource utilization and energy conversion devices such as Zn-CO2 batteries.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic materials and energy conversion technology, and particularly relates to a ZnS-modified S-doped Fe-NC catalyst, its preparation method and application. Background Technology

[0002] The continuous rise in atmospheric carbon dioxide (CO2) concentration has led to a series of environmental problems, including global climate change. Electrocatalytic carbon dioxide reduction technology can convert CO2 into high-value-added carbon-based fuels (such as carbon monoxide (CO)), providing a promising pathway for achieving the carbon cycle. Among the various products, carbon monoxide has attracted much attention due to its huge market demand and economic value.

[0003] Currently, while noble metal catalysts can achieve high CO selectivity, their high cost and limited reserves severely restrict their large-scale industrial application. Among non-noble metal catalysts, Fe-NC materials with atomically dispersed FeN4 active sites exhibit excellent CO selectivity approaching 90%, making them the most promising alternative. However, traditional Fe-NC catalysts still face two major challenges: slow reaction kinetics and insufficient long-term operational stability, making it difficult to balance activity and stability.

[0004] Studies have shown that modulating the electronic structure of the central metal through heteroatom doping (such as sulfur) or introducing nanoparticles as electron donors to stabilize the metal center are effective strategies for improving catalyst performance. However, existing synthesis methods typically rely on two or three independent precursors to provide the metal, carbon / nitrogen, and sulfur sources, respectively. This multi-precursor strategy not only leads to complex synthesis processes but also makes it difficult to precisely control the catalyst structure, especially to simultaneously achieve the synergistic introduction of sulfur doping and electron donor nanoparticles, severely limiting the controllable preparation of high-performance catalysts. Therefore, developing a simple synthesis method that can simultaneously achieve active site construction, heteroatom doping, and nanoparticle modification using a single precursor is of paramount importance for promoting the practical application of high-performance, long-life CO2RR (carbon dioxide reduction reaction) catalysts. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a ZnS-modified S-doped Fe-NC catalyst, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a ZnS-modified S-doped Fe-NC catalyst, using zinc sulfate heptahydrate and ferric sulfate as precursors, which are self-assembled with 2-methylimidazole to form an Fe-doped ZIF-8 precursor, and then subjected to one-step pyrolysis to obtain the ZnS-modified S-doped Fe-NC catalyst, denoted as ZnS@Fe-NSC catalyst.

[0007] This invention uses zinc sulfate heptahydrate and ferric sulfate as single integrated precursors of metal and sulfur, and forms an Fe-doped ZIF-8 precursor through self-assembly with 2-methylimidazole; the in-situ generation of S atom doping and ZnS nanoparticles is achieved simultaneously through a one-step pyrolysis process, and finally a structured catalyst with high CO2 reduction activity and stability is obtained.

[0008] Furthermore, the preparation method of the ZnS-modified S-doped Fe-NC catalyst includes the following steps: Zinc sulfate heptahydrate and ferric sulfate are dissolved together in water to obtain solution A; Dissolve 2-methylimidazole in water to obtain solution B; Under continuous stirring, solution B was injected into solution A, and the resulting mixture was then allowed to stand and age to obtain the Fe-doped ZIF-8 precursor. The Fe-doped ZIF-8 precursor was vacuum dried until all moisture was removed. The dried Fe-doped ZIF-8 precursor was subjected to one-step pyrolysis. After pyrolysis, it was naturally cooled to room temperature, and the resulting black powder product was collected, which is the ZnS-modified S-doped Fe-NC catalyst.

[0009] Furthermore, the molar ratio of zinc sulfate heptahydrate to ferric sulfate is 5.7:(0.156-0.2).

[0010] Furthermore, the molar ratio of zinc sulfate heptahydrate to 2-methylimidazole is 5.7:(24-30.4).

[0011] Furthermore, the static aging temperature is 20-30℃, and the static aging time is 18-28 hours.

[0012] Furthermore, the pyrolysis step is carried out under inert gas protection.

[0013] For example, the inert gas is selected from nitrogen or argon.

[0014] Furthermore, the temperature of the one-step pyrolysis is 850-950℃. During this process, sulfate ions decompose to release sulfur atoms, achieving S doping of the carbon matrix. Simultaneously, Zn sites react with sulfur to generate ZnS nanoparticles in situ, while 2-methylimidazolium ligands carbonize to form a nitrogen-doped carbon matrix.

[0015] Furthermore, during the aforementioned one-step pyrolysis, the heating rate is 2-8 °C / min, and the pyrolysis time is 1-3 hours.

[0016] Preferably, the one-step pyrolysis is carried out in a tube furnace, under nitrogen atmosphere protection, with a programmed heating rate of 5 °C / min to 900 °C, and isothermal pyrolysis at this temperature for 2 hours.

[0017] The present invention also provides a ZnS-modified S-doped Fe-NC catalyst prepared according to the above method.

[0018] The present invention also provides an application of the above-mentioned ZnS-modified S-doped Fe-NC catalyst in the electrocatalytic CO2 reduction reaction to prepare CO and / or to prepare zinc-carbon dioxide (Zn-CO2) batteries.

[0019] Compared with the prior art, the present invention has the following advantages and technical effects: This invention utilizes metal sulfate as a single precursor and employs a one-step in-situ sulfidation strategy to simultaneously construct Fe-N4 active sites, dope S atoms, and generate ZnS nanoparticles in situ via pyrolysis under nitrogen protection, thus preparing a ZnS@Fe-NSC structured catalyst. This material exhibits high CO selectivity, low overpotential, and excellent long-term stability. The ZnS nanoparticles act as electron donors, modulating the electronic structure of the Fe center, enhancing the Fe-N coordination bond strength, effectively inhibiting Fe dissolution, and improving the CO2 reduction reaction kinetics and catalyst durability. This invention features a single precursor, simplified process, and controllable structure, showing broad application prospects in electrocatalytic CO2 resource utilization and energy conversion devices such as Zn-CO2 batteries. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1In Figure 1, a is a schematic diagram of the synthesis of the ZnS@Fe-NSC catalyst prepared in Example 1 of this invention; b is a scanning electron microscope (SEM) image of the ZnS@Fe-NSC catalyst prepared in Example 1 of this invention; c is a high-resolution transmission electron microscope (HRTEM) image of the ZnS@Fe-NSC catalyst prepared in Example 1 of this invention; d is an aberration-corrected high-angle annular dark-field scanning transmission electron microscope (AC-HAADF-STEM) image of the ZnS@Fe-NSC catalyst prepared in Example 1 of this invention; and ef is an energy-dispersive X-ray spectroscopy (EDS) elemental distribution map of the ZnS@Fe-NSC catalyst prepared in Example 1 of this invention, where e is the HAADF-HRTEM image of ZnS@Fe-NSC, e1 is the total EDS mapping map of ZnS@Fe-NSC, e2 is the EDS mapping map of C element in ZnS@Fe-NSC, e3 is the EDS mapping map of Fe element in ZnS@Fe-NSC, and f is the EDS mapping map of N element in ZnS@Fe-NSC. The mapping diagrams are as follows: f1 is the EDS mapping diagram of O element in ZnS@Fe-NSC, f2 is the EDS mapping diagram of S element in ZnS@Fe-NSC, f3 is the EDS mapping diagram of Zn element in ZnS@Fe-NSC, and g is the X-ray diffraction (XRD) pattern of ZnS@Fe-NSC catalyst prepared in Example 1 of this invention.

[0021] Figure 2 In the figure, a represents the LSV curves of the catalysts of Example 1 and Comparative Examples 1-2 in CO2 saturated electrolyte, b represents the CO Faradaic efficiency of the catalysts of Example 1 and Comparative Examples 1-2 in CO2 saturated electrolyte, c represents the CO partial current density of the catalysts of Example 1 and Comparative Examples 1-2 in CO2 saturated electrolyte, d represents the TOF value of the catalysts of Example 1 and Comparative Examples 1-2 in CO2 saturated electrolyte, e represents the Tafel slope of the catalysts of Example 1 and Comparative Examples 1-2 in CO2 saturated electrolyte, and f represents the double-layer capacitance of the catalysts of Example 1 and Comparative Examples 1-2 in CO2 saturated electrolyte.

[0022] Figure 3 The results show the stability test results of the catalysts of Example 1 and Comparative Examples 1-2 under -0.58 V vs. RHE and the Fe dissolution content after electrolysis. Among them, a is the stability test result of the catalyst of Comparative Example 1 under -0.58 V vs. RHE, b is the stability test result of the catalyst under -0.58 V vs. RHE, and c is the stability test result of the catalyst of Example 1 under -0.58 V vs. RHE.

[0023] Figure 4 This is a SEM image of the catalyst in Comparative Example 1.

[0024] Figure 5 This is a SEM image of the catalyst in Comparative Example 2. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] The present invention provides a method for preparing a ZnS-modified S-doped Fe-NC catalyst, using zinc sulfate heptahydrate and ferric sulfate as precursors, which are self-assembled with 2-methylimidazole to form an Fe-doped ZIF-8 precursor, and then subjected to one-step pyrolysis to obtain a ZnS-modified S-doped Fe-NC catalyst (ZnS@Fe-NSC catalyst).

[0031] This invention uses metal sulfate as a single precursor that integrates iron, zinc, and sulfur sources. It forms a metal-organic framework precursor through self-assembly with a nitrogen-containing organic ligand (2-methylimidazole). Through a one-step pyrolysis process, the doping of S atoms into the carbon matrix, the formation of FeN4 single-atom active sites, and the in-situ generation of ZnS nanoparticles are simultaneously achieved. Finally, a ZnS@Fe-NSC structured catalyst with high CO2 reduction activity and excellent operational stability is obtained.

[0032] In a preferred embodiment of the present invention, the preparation method of ZnS-modified S-doped Fe-NC catalyst includes the following steps: Zinc sulfate heptahydrate and ferric sulfate are dissolved together in water to obtain a homogeneous solution A containing zinc and iron metal ions and sulfate anions; Dissolve 2-methylimidazole in water to obtain nitrogen-containing organic ligand solution B; Under continuous stirring, solution B was injected into solution A, and the resulting mixture was then allowed to stand and age to form an Fe-doped ZIF-8 precursor through a self-assembly process. The Fe-doped ZIF-8 precursor was vacuum dried until all moisture was removed. The dried Fe-doped ZIF-8 precursor was subjected to one-step pyrolysis. During this process, sulfate ions decomposed to release sulfur atoms to achieve S doping of the carbon matrix. At the same time, Zn sites reacted with sulfur to generate ZnS nanoparticles in situ, while 2-methylimidazolium ligands carbonized to form nitrogen-doped carbon matrix and formed atomically dispersed FeN4 active sites. After pyrolysis, the product is naturally cooled to room temperature, and the resulting black powder product is collected. This product is the ZnS-modified S-doped Fe-NC catalyst.

[0033] In a preferred embodiment of the present invention, the molar ratio of zinc sulfate heptahydrate to ferric sulfate is 5.7:(0.156-0.2).

[0034] In a preferred embodiment of the present invention, the molar ratio of zinc sulfate heptahydrate to 2-methylimidazole is 5.7:(24-30.4).

[0035] In a preferred embodiment of the present invention, when solution B is injected into solution A, the stirring rate is 600 rpm.

[0036] In a preferred embodiment of the present invention, the static aging temperature is 20-30°C and the static aging time is 18-28 hours.

[0037] In a preferred embodiment of the present invention, the one-step pyrolysis is carried out under nitrogen or argon protection.

[0038] In a preferred embodiment of the present invention, the temperature of the one-step pyrolysis is 850-950°C, preferably 900-950°C, and more preferably 900°C.

[0039] In a preferred embodiment of the present invention, when performing one-step pyrolysis, the heating rate is 2-8 °C / min and the pyrolysis time is 1-3 hours; preferably, the heating rate is 5 °C / min and the pyrolysis time is 2 hours.

[0040] Embodiments of the present invention also provide a ZnS-modified S-doped Fe-NC catalyst prepared according to the above method.

[0041] Embodiments of the present invention also provide an application of the above-described ZnS-modified S-doped Fe-NC catalyst in electrocatalytic CO2 reduction reaction (CO2RR) to produce CO and / or in zinc-carbon dioxide (Zn-CO2) batteries.

[0042] Unless otherwise specified, the room temperature in this invention is 25±2℃.

[0043] All raw materials used in the embodiments of the present invention were obtained through commercial purchase.

[0044] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0045] The technical solution of the present invention will be further illustrated by the following embodiments.

[0046] Example 1 A method for preparing a ZnS-modified S-doped Fe-NC catalyst, comprising the following steps: a. Dissolve 1.64 g (5.7 mmol) zinc sulfate heptahydrate and 62.5 mg (0.156 mmol) ferric sulfate together in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g (24 mmol) of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 30 °C for 24 hours to obtain a solid precursor (Fe@ZIF-8). d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 900 ℃ at a heating rate of 5 ℃ / min, and then pyrolyze it at this temperature for 2 hours. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@Fe-NSC catalyst.

[0047] Example 2 A method for preparing a ZnS-modified S-doped Fe-NC catalyst, comprising the following steps: a. Dissolve 1.64 g of zinc sulfate heptahydrate and 62.5 mg of ferric sulfate together in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 25 °C for 20 hours to age, thus obtaining a solid precursor. d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 850 °C at a heating rate of 5 °C / min, and then pyrolyze it at this temperature for 2 hours. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@Fe-NSC catalyst.

[0048] Example 3 A method for preparing a ZnS-modified S-doped Fe-NC catalyst, comprising the following steps: a. Dissolve 1.64 g of zinc sulfate heptahydrate and 62.5 mg of ferric sulfate together in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 25 °C for 24 hours to age, thus obtaining a solid precursor. d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 900 ℃ at a heating rate of 3 ℃ / min, and then pyrolyze it at this temperature for 3 hours. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@Fe-NSC catalyst.

[0049] Example 4 A method for preparing a ZnS-modified S-doped Fe-NC catalyst, comprising the following steps: a. Dissolve 1.64 g of zinc sulfate heptahydrate and 80.0 mg (0.2 mmol) of ferric sulfate together in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand and age at 30 °C for 18 hours to obtain a solid precursor; d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 950 °C at a heating rate of 2 °C / min, and then pyrolyze it at this temperature for 1 hour. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@Fe-NSC catalyst.

[0050] Example 5 A method for preparing a ZnS-modified S-doped Fe-NC catalyst, comprising the following steps: a. Dissolve 1.64 g of zinc sulfate heptahydrate and 62.5 mg of ferric sulfate together in 125 mL of distilled water to prepare solution A; b. Dissolve 2.50 g (30.4 mmol) of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 800 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand and age at 20 °C for 28 hours to obtain a solid precursor; d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under the protection of argon atmosphere, heat it to 900 ℃ at a heating rate of 5 ℃ / min, and then pyrolyze it at this temperature for 1.5 hours. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@Fe-NSC catalyst.

[0051] Example 6 A method for preparing a ZnS-modified S-doped Fe-NC catalyst, comprising the following steps: a. Dissolve 1.64 g of zinc sulfate heptahydrate and 62.5 mg of ferric sulfate together in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 25 °C for 24 hours to age, thus obtaining a solid precursor. d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, continue to heat it to 900℃ at a heating rate of 8℃ / min, and pyrolyze it at this temperature for 2 hours. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@Fe-NSC catalyst.

[0052] Comparative Example 1 A method for preparing an Fe-NC catalyst, comprising the following steps: a. Dissolve 1.70 g of zinc nitrate hexahydrate and 84.5 mg of ferric chloride hexahydrate (ensuring the same molar ratio of zinc to iron as in this comparative example and Example 1) together in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 25 °C for 24 hours to age, thus obtaining a solid precursor. d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 900 ℃ at a heating rate of 5 ℃ / min, and then pyrolyze it at this temperature for 2 hours. f. After the pyrolysis process is complete, allow the tube furnace to cool naturally to room temperature, and collect the resulting black powder product, which is the Fe-NC catalyst. Its SEM image is shown below. Figure 4 As shown, the original shape of ZIF was preserved, indicating that Fe-NC was successfully prepared.

[0053] Comparative Example 2 A method for preparing an Fe-NSC catalyst, comprising the following steps: a. Dissolve 1.70 g of zinc nitrate hexahydrate and 62.5 mg of ferric sulfate (ensuring the same molar ratio of zinc to iron as in this comparative example and Example 1) in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 25 °C for 24 hours to age, thus obtaining a solid precursor. d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 900 ℃ at a heating rate of 5 ℃ / min, and then pyrolyze it at this temperature for 2 hours. f. After the pyrolysis process is complete, allow the tube furnace to cool naturally to room temperature, and collect the resulting black powder product, which is the Fe-NSC catalyst. Its SEM image is shown below. Figure 5 As shown, the morphology changed significantly due to the effect of sulfate ions, indicating that Fe-NSC was successfully prepared.

[0054] Comparative Example 3 A method for preparing a ZnS@NSC catalyst, comprising the following steps: a. Dissolve 1.64 g of zinc sulfate heptahydrate in 125 mL of distilled water to prepare solution A; b. Dissolve 1.97 g of 2-methylimidazole in 125 mL of deionized water to prepare solution B; c. Under a constant stirring rate of 600 rpm, solution B was rapidly injected into solution A, and then the mixture was allowed to stand at 25 °C for 24 hours to age, thus obtaining a solid precursor. d. Dry the solid precursor obtained in step c under vacuum at 60 °C until all moisture is removed; e. Place the dried precursor obtained in step d in a tube furnace, and under nitrogen atmosphere protection, heat it to 900 ℃ at a heating rate of 5 ℃ / min, and then pyrolyze it at this temperature for 2 hours. f. After the pyrolysis process is completed, allow the tube furnace to cool naturally to room temperature and collect the resulting black powder product, which is the ZnS@NSC catalyst.

[0055] The ZnS@Fe-NSC catalyst prepared in Example 1 and the comparative sample were subjected to a series of characterization and performance tests. The test results are as follows: 1. Catalyst Synthesis and Structural Characterization: like Figure 1 As shown in Figure a, the synthesis process of the ZnS@Fe-NSC catalyst in Example 1 is illustrated: a mixed solution containing Fe2(SO4)3 and ZnSO4·7H2O is rapidly mixed with a 2-methylimidazole solution to form an Fe-doped ZIF-8 precursor through self-assembly. Subsequently, the precursor is pyrolyzed at 900℃ under a nitrogen atmosphere, simultaneously achieving in-situ generation of S-doped ZnS nanoparticles. Scanning electron microscope image (…) Figure 1 (b) shows that the prepared ZnS@Fe-NSC catalyst basically retains the morphology of the ZIF-8 precursor. High-resolution transmission electron microscopy image ( Figure 1 (c) High-density nanoparticles were observed loaded on the catalyst surface. X-ray diffraction pattern ( Figure 1 The image (g) shows that the ZnS@Fe-NSC sample exhibits distinct diffraction peaks at 28.4°, 30.5°, and 47.5°, corresponding to the characteristic crystal planes of ZnS, while the Fe-NC and Fe-NSC samples only show broad diffraction peaks for carbon. Aberration-corrected high-angle annular dark-field scanning transmission electron microscope image (g) Figure 1 The middle d-axis shows bright, isolated bright spots distributed on a carbon substrate, providing direct evidence of atomic-level dispersion of iron species. (Elemental distribution map of energy-dispersive X-ray spectroscopy) Figure 1 The results from the ef (including e1-e3 and f1-f3) further confirm the uniform distribution of the five elements Zn, S, N, Fe, and C in the catalyst.

[0056] 2. Evaluation of the catalyst's CO2 electroreduction performance: For H-type batteries, the catalyst ink consisted of 5 mg of catalyst powder, 20 μL of Nafion solution (5 wt%), and 230 μL of isopropanol (as a solution), and was ultrasonically dispersed for at least 1 hour to ensure uniform mixing. Subsequently, 50 μL of the catalyst ink was dropped onto carbon paper (SGL SIGRACET 28BC) to achieve a 1 mg·cm⁻¹ concentration. -2 The catalyst loading was determined. Electrochemical measurements of the H-type battery were performed using a three-electrode system. The anode and cathode chambers were separated by a pre-activated proton exchange membrane (Nafion 117), and the electrolyte was a 0.5 M KHCO3 solution. A platinum plate (1 × 1 cm²) was used. 2 An Ag / AgCl electrode (saturated with 3 M KCl solution) was used as the counter electrode and reference electrode, respectively. All measured potentials were converted to the reversible hydrogen electrode (RHE) scale using the formula: E RHE = E AgCl + 0.0591 × pH + 0.210 V, where E AgCl The potential for Ag / AgCl is given. All electrodes are connected to an electrochemical workstation (Cortest CS310M). Before electrolysis, the electrolyte is prepared at a flow rate of 50 mL / min.-1 The electrolyte was purified and saturated using high-purity CO2 gas. A flow rate of 20 mV·s was adopted. -1 The scan rate was measured using linear sweep voltammetry (LSV). The CO2 reduction reaction (CO2RR) performance of the catalyst at different potentials was evaluated using galvanostatic method (CA).

[0057] like Figure 2 As shown in Figure a, in a CO2-saturated 0.5 M KHCO3 electrolyte, the ZnS@Fe-NSC catalyst exhibits the highest current density and the lowest onset potential. CO Faradaic efficiency ( Figure 2 As shown in b), ZnS@Fe-NSC exhibited the highest CO selectivity across all test potentials, reaching 98.53% at -0.58 V vs. RHE. CO partial current density ( Figure 2 The value of c indicates that ZnS@Fe-NSC exhibits optimal catalytic current across the entire potential range. The CO conversion frequency calculated based on the Fe active sites ( Figure 2 The data from the middle section shows that ZnS@Fe-NSC reaches 24,386 h at -0.68 V vs. RHE. -1 The capacitance was significantly higher than that of the control sample. Electrochemical double-layer capacitance test ( Figure 2 The value of e indicates that the electrochemical active areas of the three are not significantly different. Tafel slope analysis ( Figure 2 The data from f shows that ZnS@Fe-NSC has the smallest Tafel slope (206 mV·dec). -1 This indicates that it has the fastest CO generation kinetics.

[0058] 3. Catalyst stability test: After loading the catalyst onto carbon paper, chronoamperometry (CA) was used for continuous electrolysis at a constant potential of -0.58 V vs. RHE. During electrolysis, the retention of activity was assessed by monitoring changes in current density, and the Faradaic efficiency (FE) of CO was calculated by periodically detecting gaseous products using online gas chromatography (GC). CO )stability.

[0059] like Figure 3 As shown, after 30 hours of potentiostatic stability testing at -0.58 V vs. RHE, ZnS@Fe-NSC exhibited the lowest current density decay rate (11.32%), while Fe-NSC showed the most significant decay (56.54%). Inductively coupled plasma mass spectrometry analysis of the electrolyte after electrolysis revealed that the ZnS@Fe-NSC catalyst had the lowest Fe dissolution concentration (0.0055 μg / mL), with a dissolution rate of less than 0.5%, significantly lower than Fe-NSC and Fe-NC.

[0060] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a ZnS-modified S-doped Fe-NC catalyst, characterized in that, Using zinc sulfate heptahydrate and ferric sulfate as precursors, they are self-assembled with 2-methylimidazole to form an Fe-doped ZIF-8 precursor, which is then obtained by one-step pyrolysis to obtain the ZnS-modified S-doped Fe-NC catalyst.

2. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 1, characterized in that, Includes the following steps: Zinc sulfate heptahydrate and ferric sulfate are dissolved together in water to obtain solution A; Dissolve 2-methylimidazole in water to obtain solution B; Under continuous stirring, solution B was injected into solution A, and the resulting mixture was then allowed to stand and age to obtain the Fe-doped ZIF-8 precursor. The Fe-doped ZIF-8 precursor was vacuum dried until all moisture was removed. The dried Fe-doped ZIF-8 precursor was subjected to one-step pyrolysis. After pyrolysis, it was naturally cooled to room temperature, and the resulting black powder product was collected, which is the ZnS-modified S-doped Fe-NC catalyst.

3. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 2, characterized in that, The molar ratio of zinc sulfate heptahydrate to ferric sulfate is 5.7:(0.156-0.2).

4. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 2, characterized in that, The molar ratio of zinc sulfate heptahydrate to 2-methylimidazole is 5.7:(24-30.4).

5. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 2, characterized in that, The static aging temperature is 20-30℃, and the static aging time is 18-28 hours.

6. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 2, characterized in that, The pyrolysis step is carried out under inert gas protection.

7. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 2, characterized in that, The temperature of the pyrolysis step is 850-950℃.

8. The method for preparing the ZnS-modified S-doped Fe-NC catalyst according to claim 7, characterized in that, During the aforementioned pyrolysis step, the heating rate is 2-8 °C / min, and the pyrolysis time is 1-3 hours.

9. A ZnS-modified S-doped Fe-NC catalyst, characterized in that, It is prepared according to any one of claims 1-8.

10. The application of the ZnS-modified S-doped Fe-NC catalyst as described in claim 9 in the electrocatalytic CO2 reduction reaction to prepare CO and / or the preparation of zinc-carbon dioxide batteries.

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