Preparation method of electrocatalyst and application of high current density seawater electrolysis

Abstract

This invention belongs to the field of electrocatalytic material preparation technology, and discloses a method for preparing an electrocatalyst with a Fe and Mn co-doped Ni3S2 nanorod array structure. A simple one-step hydrothermal method is used to dissolve ferric chloride hexahydrate, manganese acetate tetrahydrate, and sodium sulfide nonahydrate in deionized water. After stirring and dissolving, the solution is transferred together with nickel foam to a high-pressure reactor. After hydrothermal reaction, the catalyst is washed and dried to obtain the electrocatalyst. This catalyst exhibits good performance in both alkaline freshwater and seawater, and possesses excellent stability and corrosion resistance. The electrocatalytic material prepared by this invention has a unique nanorod array structure, providing more active sites for the reaction, accelerating the electron transfer rate, and thus improving the electrocatalytic water splitting performance.

Description

[0001] Applicants: Jiangsu Jiangke Composite New Materials Co., Ltd., Jiangsu Huaxia Paint Technology Co., Ltd., Jiangsu University Inventors: Xu Yuanguo, Wu Wei, Xie Feng, Meng Suci, Xie Baosheng, Xie Meng, Xie Jimin This research was supported by the National Natural Science Foundation of China (No: 22576086), and we would like to express our sincere gratitude to the National Natural Science Foundation of China for its valuable support. Technical Field

[0002] This invention belongs to the field of electrocatalysis technology, specifically relating to a method for preparing a highly efficient Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalyst for decomposing alkaline freshwater / seawater. Background Technology

[0004] Hydrogen energy, as a clean energy carrier with zero carbon emissions, is one of the core technologies for achieving the goal of "carbon neutrality." Traditional hydrogen production through water electrolysis relies on freshwater resources, exacerbating the global freshwater shortage. Seawater accounts for 96.5% of the Earth's water resources; direct seawater electrolysis for hydrogen production can overcome freshwater limitations, significantly reduce costs, and is a potential solution for large-scale application. However, seawater has a complex composition, containing chloride ions (Cl). - Mg 2+ Ca 2+ Substances such as Cl, the most abundant of which is Cl. - The content of [a certain substance] reached 19.35 g / kg, which posed many technical bottlenecks to the seawater electrolysis catalyst.

[0005] Studies have shown that nickel-based sulfides possess rich crystal forms and structural diversity, and various morphologies such as nanoparticles, nanosheets, and porous structures can be prepared by controlling the synthesis methods. The sulfur (S) element in nickel-based sulfides forms a strong coordination interaction with Ni, which can construct a stable chemical barrier on the catalyst surface, inhibiting the erosion of active sites by Cl⁻ and alleviating electrode corrosion. Some nickel-based sulfides can also generate an oxygen-rich protective layer in situ during the reaction, hindering the deposition of calcium and magnesium ions and effectively improving catalytic stability. In recent years, nickel-based sulfides have been widely reported to have excellent activity. However, despite their high activity, nickel-based sulfides are often unstable under harsh reaction conditions, especially during oxygen evolution. The main reason is that S is oxidized and dissolved at high oxidation potentials, and the active phase undergoes reconstruction during the reaction, accompanied by volume expansion leading to structural collapse. Multiple factors contribute to the decrease in stability. This instability problem is prevalent in various metal sulfides. Recent studies have shown that introducing two or more transition metals (such as Fe, Co, and Mn) with different activities into Ni3S2 can regulate electron density, increase electron transfer rate, or control morphology to expose more active sites, such as nanowires, nanotubes, and nanosheets. This can optimize electronic structure, enhance electrical conductivity, and increase the active surface area of ​​the catalyst, thereby enhancing the overall water splitting of nickel-based sulfides. Therefore, when using Ni3S2 as a water splitting catalyst, factors such as synthesis temperature, composite materials, and morphological structure must be considered to achieve the goal of constructing a highly efficient and stable electrocatalyst. Summary of the Invention

[0006] To address the problems existing in the prior art, the primary objective of this invention is to provide a method for preparing an Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalyst that can undergo oxygen evolution reaction under alkaline seawater conditions.

[0007] Another objective of this invention is to provide a method for preparing an Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalyst capable of undergoing complete water splitting tests under alkaline conditions.

[0008] This invention is achieved through the following technical solution: A method for preparing a Fe and Mn co-doped Ni3S2 nanorod array electrocatalyst capable of oxygen evolution catalysis under alkaline seawater and alkaline freshwater conditions, comprising the following steps: (1) The nickel foam was ultrasonically treated with hydrochloric acid, deionized water and ethanol in sequence, and then dried in an oven to obtain clean nickel foam.

[0009] (2) Dissolve ferric chloride hexahydrate, manganese acetate tetrahydrate and sodium sulfide nonahydrate in deionized water and stir for a certain period of time at a certain temperature.

[0010] (3) The mixture and nickel foam are transferred together into a high-pressure reactor for hydrothermal reaction. The hydrothermally reacted substances are washed and dried to obtain an electrocatalyst.

[0011] Preferably, the molar contents of ferric chloride hexahydrate, manganese acetate tetrahydrate, and sodium sulfide nonahydrate in step (2) are 5%-30%, 5%-30%, and 10%-80%, respectively. The volume contents of anhydrous ethanol and deionized water are 30%-80% and 20%-80%, respectively.

[0012] Preferably, the stirring temperature in step (2) is 18-25℃ and the stirring time is 1-4 h.

[0013] Preferably, the hydrothermal temperature in step (3) is 80-200℃ and the hydrothermal time is 2-24 h.

[0014] Preferably, the drying temperature in step (3) is 50-90℃ and the drying time is 6-24 h.

[0015] The beneficial effects of the present invention are as follows: (1) The Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalyst prepared by the method of the present invention has an ordered framework of nanorod array structure and nanorods of different sizes, forming a unique structure that provides more active sites for the reaction.

[0016] (2) The Fe and Mn co-doped Ni3S2 nanorod array electrocatalyst prepared by the method of the present invention has good electrochemical performance: the optimal catalyst can generate 500 mA cm⁻¹ in oxygen evolution tests in alkaline dilute aqueous solution with overpotentials of 310 mV and 348 mV, respectively. -2 With 1000 mA cm -2 The electrolysis current for water has a Tafel slope of 38.6 mV dec. -1 The double-layer capacitance is 5.18 mF cm⁻¹. -2 And at 500 mA cm -2 The material remained stable for 200 h at the specified current density, demonstrating its excellent oxygen evolution performance and stability under alkaline freshwater conditions.

[0017] (3) The Fe and Mn co-doped Ni3S2 nanorod array electrocatalyst prepared by the method of the present invention has good electrochemical performance: the optimal catalyst was tested in an alkaline seawater solution for oxygen evolution at a current density of 500 mA cm⁻¹. -2 With 1000 mA cm -2 The overpotentials were 337 mV and 387 mV, respectively, and at 500 mA cm⁻¹ -2The material remained stable at the current density for 200 hours, demonstrating excellent oxygen evolution performance and good corrosion resistance under alkaline seawater conditions.

[0018] (4) The Fe and Mn co-doped Ni3S2 nanorod array electrocatalyst prepared by the method of the present invention has good electrochemical performance: the optimal catalyst, when assembled with commercial Pt / C, showed a total water splitting potential of 1.72 V@100 mA cm⁻¹ in alkaline fresh water and seawater solutions. -2 With 1.74 V@100 mA cm -2 This indicates that the material of the present invention exhibits good oxygen evolution catalytic performance and complete water splitting under alkaline conditions. Attached Figure Description

[0019] Figure 1 XRD pattern of the optimal sample prepared in this invention Figure 2 SEM and TEM images of the optimal sample prepared in this invention. Figure 3 Mapping diagram of the optimal sample prepared in this invention Figure 4 The LSV diagram of oxygen evolution in alkaline fresh water for the optimal sample prepared in this invention. Figure 5 This is a stability diagram of oxygen evolution in alkaline fresh water for the optimal sample prepared in this invention. Figure 6 The LSV diagram of oxygen evolution in alkaline seawater for the optimal sample prepared in this invention. Figure 7 This is a stability diagram of oxygen evolution in alkaline seawater for the optimal sample prepared in this invention. Figure 8 LSV diagram of the optimal sample prepared in this invention for total water hydrolysis Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. Example 1:

[0021] The preparation method of Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalytic material includes the following steps: (1) Dissolve 1.8 mmol ferric chloride hexahydrate, 0.4 mmol manganese acetate tetrahydrate and 6 mmol sodium sulfide nonahydrate in a solution of about 50 mL deionized water.

[0022] (2) Place the resulting mixture solution on a magnetic stirrer and stir for 1 h.

[0023] (3) The resulting mixture and the treated NF were transferred to a 100 mL high-pressure reactor and then hydrothermally reacted at 130 °C for 6 h.

[0024] (4) Collect the obtained sample and wash it three times each with anhydrous ethanol and deionized water, and then dry it at 60°C for 12 hours. Example 2:

[0025] The preparation method of Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalytic material includes the following steps: In order to investigate the effect of different metal ratios on the performance of the catalyst, the Fe:Mn molar ratio in step (1) of Example 1 was controlled to be 1:1, 2:1, 3:1, etc., and the other steps were the same as in Example 1. Example 3:

[0026] The preparation method of Fe and Mn co-doped Ni3S2 nanorod array structure electrocatalytic material includes the following steps: To investigate the effect of the substances obtained at different calcination temperatures on the catalyst performance, the hydrothermal temperatures of the samples were 110℃, 120℃, and 130℃, respectively, and the other steps were the same as in Example 1.

[0027] Figure 1 The XRD pattern of the optimal sample prepared in this invention clearly shows that the synthesized sample corresponds almost completely with the standard card.

[0028] Figure 2 The SEM and TEM images of the optimal sample prepared for this invention clearly show that the synthesized sample exhibits a nanorod array structure, neatly arranged on the surface of nickel foam.

[0029] Figure 3 The mapping diagram shows the optimal sample prepared according to the present invention. It can be clearly seen from the diagram that the four elements Fe, Mn, Ni and S are evenly distributed in the synthesized sample.

[0030] Figure 4 The LSV diagram of oxygen evolution in alkaline fresh water for the optimal sample prepared in this invention clearly shows that the synthesized sample exhibits good overpotential, specifically η. 100 =266 mV, η 500 =310 mV and η 1000 =348 mV.

[0031] Figure 5This is a stability graph of the optimal sample prepared in this invention in alkaline fresh water for oxygen evolution. It clearly shows that the synthesized sample exhibits excellent long-term durability in alkaline fresh water at a current density of 500 mA cm⁻¹. -2 Under certain conditions, it can operate stably for 200 hours with minimal potential decay.

[0032] Figure 6 The figure shows the LSV (Left Potential Variation) of the optimal sample prepared in this invention in alkaline seawater. It can be clearly seen from the figure that the overpotentials of the synthesized sample in the oxygen evolution test in alkaline seawater are η... 100 =268 mV, η 500 =337mV and η 1000 =387 mV.

[0033] Figure 7 This is a stability graph of the optimal sample prepared in this invention in alkaline seawater. It clearly shows that the synthesized sample exhibits excellent long-term durability in alkaline seawater at a current density of 500 mA cm⁻¹. -2 Under certain conditions, it can operate stably for 200 hours with minimal potential decay.

[0034] Figure 8 The image shows the LSV (Liquid Potential Variation) of the optimal sample prepared in this invention for water hydrolysis. It clearly shows that the overpotential of the synthesized sample in both alkaline freshwater and seawater solutions for water hydrolysis was 1.72 V @ 100 mA cm⁻¹. -2 and 1.74V@100 mA cm -2 This indicates that the material of the present invention has good oxygen evolution catalytic performance under alkaline conditions.

[0035] Note: The above embodiments are only used to illustrate the present invention and are not intended to limit the technical solutions described in the present invention. Therefore, although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. All technical solutions and improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A Fe and Mn co-doped Ni3S2 nanorod array material (Fe,Mn-Ni3S2), characterized in that, The Fe and Mn co-doped catalyst can "anchor" S atoms through stronger metal-sulfur bonds, reducing S dissolution and loss. Simultaneously, the doping of Fe and Mn in the crystal lattice increases the number of active sites and forms a structural support framework, inhibiting the collapse of the Ni3S2 lattice during electrocatalysis and extending the catalyst's cycle life. The electrocatalyst was tested in alkaline solutions for oxygen evolution and total water splitting. The optimized Fe,Mn-Ni3S2 catalyst requires overpotentials of 348 mV and 387 mV in alkaline fresh water and seawater, respectively, to reach 1000 mA cm⁻¹. −2 In a Pt / C||Fe,Mn-Ni3S2 electrolytic cell in alkaline fresh water and alkaline seawater, when the current density is 100 mA cm⁻¹ −2 The voltages were 1.72 V and 1.74 V, respectively; the electrocatalyst was tested at 500 mA cm⁻¹. −2 It exhibits excellent durability in both media, maintaining its activity without significant reduction within 200 hours, indicating good corrosion resistance and great potential for industrial applications.

2. A method for preparing an electrocatalyst made of Fe and Mn co-doped Ni3S2 nanorod array material, characterized in that, Includes the following steps: (1) Pretreatment of nickel foam (NF) Nickel foam was ultrasonically treated with hydrochloric acid, deionized water and ethanol in sequence, and then dried in an oven to obtain clean nickel foam. (2) Synthesis of Fe,Mn-Ni3S2 Nanocomposite materials were prepared by a simple one-step hydrothermal method. Ferric chloride hexahydrate, manganese acetate tetrahydrate, and sodium sulfide nonahydrate were dissolved in deionized water. The mixture was stirred and dissolved on a magnetic stirrer and then transferred to a high-pressure reactor along with NF. The hydrothermally heated material was washed and dried to obtain an electrocatalyst.

3. The method for preparing an electrocatalyst according to claim 2, which is characterized in that, In step (2), the molar contents of ferric chloride hexahydrate, manganese acetate tetrahydrate, and sodium sulfide nonahydrate are 5%-30%, 5%-30%, and 10%-80%, respectively. The volume contents of anhydrous ethanol and deionized water are 30%-80% and 20%-80%, respectively.

4. The method for preparing an electrocatalyst according to claim 2, which is characterized in that, The stirring temperature in step (2) is 18-25℃ and the stirring time is 1-4 h.

5. The method for preparing an electrocatalyst according to claim 2, which is characterized in that, The hydrothermal temperature in step (2) is 80-200℃ and the hydrothermal time is 2-24 h.

6. The method for preparing an electrocatalyst according to claim 2, which is characterized in that, The drying temperature in step (2) is 50-90℃ and the drying time is 6-24 h.

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