A Fe5Ni4S 8-x O x Process for the preparation of an electrocatalyst and use thereof

Abstract

This invention discloses a Fe5Ni4S 8‑x O x This paper describes the preparation method and application of electrocatalysts, belonging to the fields of materials and electrocatalysis technology. The method involves first synthesizing a nickel-iron-based metal-organic framework (FeNi-MOF) via a hydrothermal method, then adding a sulfur source to hydrothermally synthesize oxygen-doped nickel pyrite (FeNi-MOF-S), and finally annealing at high temperature to generate Fe5Ni4S. 8‑x O x Electrocatalyst. Compared with the traditional high-temperature solid-state synthesis of pyrite, this method is simpler to operate and less expensive. The electrocatalyst prepared by this method has oxygen atoms directionally incorporated into the pyrite lattice, inducing changes in the electronic modes of the metal center and Ni / FeOOH lattice distortion, resulting in excellent oxygen evolution performance and significantly improved catalytic activity and stability. After being assembled into anion exchange membranes for water electrolysis, it also exhibits high activity and long-term stability. This catalyst reduces costs and energy consumption, significantly lowering costs and making it suitable for large-scale renewable energy hydrogen production, thus suitable for industrial production.

Description

Technical Field

[0001] This invention discloses a Fe5Ni4S 8-x O x The preparation methods and electrolytic applications of electrocatalysts belong to the fields of materials science and electrocatalysis technology. Background Technology

[0002] In recent years, with the intensification of climate change and the increasingly severe energy shortage, the development of green and renewable energy to replace traditional fossil fuels has become a global focus. Anion exchange membrane electrolysis (AEMWE) technology, due to its ability to use inexpensive non-precious metal catalysts, significantly reduces system costs and energy consumption, and is considered a feasible route for large-scale renewable energy hydrogen production. However, this technology still faces the problem of slow kinetics in the oxygen evolution reaction (OER), which severely restricts the overall hydrogen production efficiency. The slow OER process leads to a high reaction overpotential, and the increase in overpotential further increases system energy consumption, limiting the further promotion and application of AEMWE technology. Therefore, to improve the energy efficiency and economy of the water electrolysis hydrogen production process, the development of high-performance OER electrocatalysts has become an urgent research task.

[0003] While noble metal catalysts (such as Pt, Ru, and Ir) can accelerate the water electrolysis process and improve energy efficiency, their high cost and inherent scarcity make them unsuitable for large-scale hydrogen production. This core challenge necessitates a shift in current research focus to developing high-performance, low-cost transition metal-based OER electrocatalysts.

[0004] Nickel pyrite [(FeNi)9S8] possesses a three-dimensional network of small metallic cubes connected by sulfur and metal atoms, with iron and nickel atoms occupying interstitial positions in the octahedrons and tetrahedrons, respectively. This structure exhibits satisfactory self-reconstruction properties, making it an ideal model material. However, both experimental and theoretical studies indicate that the OER activity of nickel pyrite electrocatalysts still requires further improvement to compete with noble metal catalysts.

[0005] To address the problems in existing technologies, we noted that patent CN115522216B discloses a phosphorus-doped nickel pyrite electrocatalyst and its preparation method. However, this method involves phosphorus heteroatom doping, resulting in long preparation cycles and low yields, making it difficult to meet the demands of industrial mass production. Another patent, CN115595616B, reports a method for preparing a Fe5Ni4S8 oxygen evolution electrode material, which involves mixing iron salts, nickel salts, thiourea, polyvinylpyrrolidone with ethylene glycol and N,N-dimethylformamide, followed by a solvothermal reaction to obtain the target material. However, this method introduces the polymeric complex polyvinylpyrrolidone, leading to limited improvement in catalytic performance and increasing preparation costs, thus also hindering large-scale application. Currently, systematic reports on catalytic materials based on single-phase (FeNi)9S8 as the main active site, capable of being assembled into anion exchange membrane water electrolyzers with both high activity and long-term operational stability, are still rare. Summary of the Invention

[0006] To solve the above problems, the present invention provides a Fe5Ni4S 8-x O x This paper describes a novel synthesis route for gilt pyrite (FeNi)9S8, proposing a doping strategy based on partial sulfidation of an oxygen-coordinated bimetallic FeNi-MOF precursor. This successfully prepared a gilt pyrite structure with coexisting sulfur and oxygen (Fe5Ni4S). 8-x O x This process simplifies experimental operations, reduces production costs, and possesses good operability. The directional doping of oxygen atoms into the nickel pyrite lattice induces modulation and reconstruction of the electronic structure at the metal center, leading to lattice distortion in Ni / FeOOH and thus endowing the material with excellent oxygen evolution reaction properties. Furthermore, Fe5Ni4S... 8-x O x The anion exchange membrane water electrolyzer, assembled as the anode, exhibits high catalytic activity and long-term operational stability, showing promising prospects for industrial application.

[0007] The present invention adopts the following technical solution: A Fe5Ni4S 8-x O x The preparation method of the electrocatalyst involves first synthesizing a nickel-iron-based metal-organic framework FeNi-MOF via a hydrothermal method, followed by the addition of a sulfur source for hydrothermal synthesis of oxygen-doped nickel pyrite FeNi-MOF-S, and finally high-temperature annealing to generate Fe5Ni4S. 8-x O x Electrocatalyst.

[0008] The process includes the following steps: Step S1: Dissolve 2,5-dihydroxyterephthalic acid (C8H6O6), nickel nitrate (Ni(NO3)2), and ferrous chloride (FeCl2) in N,N-dimethylformamide (C3H7NO), and then transfer the solution to a 50 mL autoclave and heat to obtain the FeNi-MOF precursor. Step S2: Dissolve the FeNi-MOF precursor and thiourea CH4N2S in 30 mL of N,N-dimethylformamide C3H7NO, and then transfer to a 50 mL autoclave and heat to obtain FeNi-MOF-S. Step S3: After high-temperature annealing of FeNi-MOF-S, Fe5Ni4S is obtained. 8-x O x Electrocatalyst.

[0009] Further, in step S1, the mass of 2,5-dihydroxyterephthalic acid is 0.08-0.09 g, the mass of nickel nitrate is 0.21-0.23 g, the mass of ferrous chloride is 0.12-0.13 g, and the volume of N,N-dimethylformamide is 30 mL.

[0010] Furthermore, in step S1, the reaction conditions in the autoclave are: heating at 120°C for 20–24 hours.

[0011] Furthermore, in step S2, the mass ratio of CH4N2S to the FeNi-MOF precursor is 1:1, 1:2, or 1:3.

[0012] Furthermore, in step S2, the reaction conditions in the autoclave are: heating at 180°C for 10–12 h.

[0013] Furthermore, in step S3, the annealing temperature is 500–600°C, and the annealing time is 1–2 h.

[0014] Furthermore, a Fe5Ni4S 8-x O x Electrocatalyst, the Fe5Ni4S 8-x O x The electrocatalyst used is Fe5Ni4S 8- x O x The Fe5Ni4S electrocatalyst was prepared using a specific method. 8-x O x The electrocatalyst involves oxygen atoms entering the Fe5Ni4S8 crystal lattice, replacing the S atom lattice sites and maintaining the pyrite structure of Fe5Ni4S8. 8-x O x Nanocrystalline materials.

[0015] Furthermore, a Fe5Ni4S described above8-x O x Electrocatalysts are used as oxygen evolution electrocatalysts in anion exchange membrane water electrolysis.

[0016] Through the above design scheme, the present invention can bring the following beneficial effects: This invention presents a novel method for synthesizing nickel pyrite and proposes an innovative doping strategy to partially sulfide a sulfur-oxygen coexisting nickel pyrite electrocatalyst (Fe5Ni4S) from an oxygen-coordinated bimetallic FeNi-MOF precursor. 8-x O x The experimental procedure is simplified and easy to operate; the prepared nickel-pyrite electrocatalyst (Fe5Ni4S) 8-x O x Linear sweep voltammetry (OER) was performed on the prepared nickel pyrite electrocatalyst (Fe5Ni4S), and the overpotential was reduced by 0.115 V compared to the comparative sample, demonstrating excellent oxygen evolution performance. 8-x O x ) at 100 mA cm -2 It exhibits excellent long-term stability with a current density exceeding 5000 hours.

[0017] The nickel pyrite electrocatalyst (Fe5Ni4S) prepared according to the preparation method provided in this invention is... 8-x O x After assembling the anion exchange membrane and electrolyzing water, at 1A cm -2 It exhibits high activity of 1.73V and long-term stability of 1000h at industrial current densities. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: Figure 1 Fe5Ni4S prepared in Example 1 of this invention 8-x O x SEM images of electrocatalyst materials; Figure 2 Fe5Ni4S prepared in Example 1 of this invention 8-x O x TEM image of the electrocatalyst material; Figure 3 Fe5Ni4S prepared in Example 2 of this invention 8-x O x SEM images of electrocatalyst materials; Figure 4 Fe5Ni4S prepared in Example 2 of this invention 8-x O x TEM image of the electrocatalyst material; Figure 5 Fe5Ni4S prepared in Example 3 of this invention 8-x O x SEM images of electrocatalyst materials; Figure 6 The OER linear scan voltammetry curves for Embodiment 1 and the comparative example of the present invention are shown below. Figure 7 Example 1 of the present invention was performed at 100 mA cm⁻¹ -2 The chronopotential curve of a galvanostat under current density; Figure 8 This is a comparison of the polarization curves of the anion exchange membranes assembled in Example 1 and the comparative example after water electrolysis. Figure 9 Embodiment 1 of the present invention is in 1A cm -2 The chronopotential curve of a galvanostat under industrial current density; Figure 10 Fe5Ni4S prepared in Example 1 of this invention 8-x O x XRD pattern of electrocatalyst material. Detailed Implementation

[0019] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0020] This invention provides a Fe5Ni4S 8-x O x The preparation method of the electrocatalyst involves first synthesizing a nickel-iron-based metal-organic framework FeNi-MOF via a hydrothermal method, followed by the addition of a sulfur source for hydrothermal synthesis of oxygen-doped nickel pyrite FeNi-MOF-S, and finally high-temperature annealing to generate Fe5Ni4S. 8-x O x Electrocatalyst.

[0021] The process includes the following steps: Step S1: Dissolve 2,5-dihydroxyterephthalic acid (C8H6O6), nickel nitrate (Ni(NO3)2), and ferrous chloride (FeCl2) in N,N-dimethylformamide (C3H7NO), and then transfer the solution to a 50 mL autoclave and heat to obtain the FeNi-MOF precursor. Step S2: Dissolve the FeNi-MOF precursor and thiourea CH4N2S in 30 mL of N,N-dimethylformamide C3H7NO, and then transfer to a 50 mL autoclave and heat to obtain FeNi-MOF-S. Step S3: After high-temperature annealing of FeNi-MOF-S, Fe5Ni4S is obtained. 8-x O x Electrocatalyst.

[0022] Further, in step S1, the mass of 2,5-dihydroxyterephthalic acid is 0.08-0.09 g, the mass of nickel nitrate is 0.21-0.23 g, the mass of ferrous chloride is 0.12-0.13 g, and the volume of N,N-dimethylformamide is 30 mL.

[0023] Furthermore, in step S1, the reaction conditions in the autoclave are: heating at 120°C for 20–24 h, with a heating rate of 5°C / min.

[0024] Furthermore, in step S2, the mass ratio of CH4N2S to the FeNi-MOF precursor is 1:1, 1:2, or 1:3.

[0025] Furthermore, in step S2, the reaction conditions in the autoclave are: heating at 180°C for 10–12 h, with a heating rate of 5°C / min.

[0026] Furthermore, in step S3, the annealing temperature is 500–600°C, and the annealing time is 1–2 h.

[0027] Furthermore, a Fe5Ni4S 8-x O x Electrocatalyst, the Fe5Ni4S 8-x O x The electrocatalyst used is Fe5Ni4S 8- x O x The electrocatalyst was prepared using a specific method.

[0028] In pyrite materials, oxygen atoms enter the Fe5Ni4S8 crystal lattice, replacing some of the S atom lattice sites and maintaining the pyrite structure of Fe5Ni4S8. 8-x O x Nanocrystalline material, Fe5Ni4S 8-x O x The range of X in the composition of the nanocrystalline material is 1 ≤ X ≤ 3. The value of X is controlled by the amount of sulfur added.

[0029] Furthermore, a Fe5Ni4S described above 8-x O xElectrocatalysts are used as oxygen evolution electrocatalysts in anion exchange membrane water electrolysis. Example 1

[0030] (1) 2,5-dihydroxyterephthalic acid (C8H6O6, 0.08 g), nickel nitrate (Ni(NO3)2, 0.22 g) and ferrous chloride (FeCl2, 0.14 g) were dissolved in N,N-dimethylformamide (C3H7NO, 30 mL), and then the solution was transferred to a 50 mL autoclave and heated to obtain the FeNi-MOF precursor; (2) FeNi-MOF and thiourea (CH4N2S, 100 mg) were dissolved in N,N-dimethylformamide (C3H7NO, 30 mL), and then transferred to a 50 mL autoclave and heated to obtain FeNi-MOF-S; (3) FeNi-MOF-S was annealed at high temperature (600℃) to obtain Fe5Ni4S. 8-x O x Electrocatalyst. Example 2

[0031] (1) 2,5-dihydroxyterephthalic acid (C8H6O6, 0.08 g), nickel nitrate (Ni(NO3)2, 0.22 g) and ferrous chloride (FeCl2, 0.14 g) were dissolved in N,N-dimethylformamide (C3H7NO, 30 mL), and then the solution was transferred to a 50 mL autoclave and heated to obtain the FeNi-MOF precursor; (2) FeNi-MOF and thiourea (CH4N2S, 50 mg) were dissolved in N,N-dimethylformamide (C3H7NO, 30 mL), and then transferred to a 50 mL autoclave and heated to obtain FeNi-MOF-S; (3) FeNi-MOF-S was annealed at high temperature (600℃) to obtain Fe5Ni4S. 8-x O x -1 Electrocatalyst. Example 3

[0032] (1) 2,5-dihydroxyterephthalic acid (C8H6O6, 0.08 g), nickel nitrate (Ni(NO3)2, 0.22 g) and ferrous chloride (FeCl2, 0.14 g) were dissolved in N,N-dimethylformamide (C3H7NO, 30 mL), and then the solution was transferred to a 50 mL autoclave and heated to obtain the FeNi-MOF precursor; (2) FeNi-MOF and thiourea (CH4N2S, 200 mg) were dissolved in N,N-dimethylformamide (C3H7NO, 30 mL), and then transferred to a 50 mL autoclave and heated to obtain FeNi-MOF-S; (3) FeNi-MOF-S was annealed at high temperature (600℃) to obtain Fe5Ni4S. 8-x O x -2 Electrocatalyst.

[0033] Comparative Example (1) Dissolve ferrous sulfate heptahydrate (FeSO4·7 H2O, 0.463 g) and nickel sulfate hexahydrate (NiSO4·6 H2O, 0.35 g) in 55 mL of N,N-dimethylformamide (DMF) and 15 mL of ethylene glycol (EG), and sonicate for 60 minutes. (2) Add thiourea (CH4N2S, 640mg) to the above solution, sonicate for 15 minutes, transfer the solution to a 100mL autoclave and heat at 190℃ for 12 hours to obtain a comparative example.

[0034] The prepared Fe5Ni4S 8-x O x The electrocatalyst (Example 1) was used as the working electrode, the Hg / HgO electrode as the reference electrode, and the platinum sheet electrode as the counter electrode. The test was conducted in 1.0 M KOH electrolyte within a voltage range of 0.924–1.9 V (vs. RHE) for 5 mV / s. -1 Under scan rate test conditions, an OER linear scan voltammetric test was performed. From Figure 6 It can be seen that at 10mA cm -2 At the specified current density, Example 1 required an overpotential of 1.425 V, while the comparative example required an overpotential of 1.54 V, indicating that the electrocatalytic oxygen evolution performance of the material in Example 1 was significantly improved compared to the comparative example. Therefore, the Fe5Ni4S prepared in this invention... 8-x O x The material has broad market application prospects as an oxygen evolution electrocatalyst.

Claims

1. A Fe5Ni4S 8-x O x A method for preparing an electrocatalyst, characterized in that: First, nickel-iron based metal-organic framework FeNi-MOF was synthesized via a hydrothermal method. Then, an oxygen-doped nickel pyrite FeNi-MOF-S was synthesized via hydrothermal addition of a sulfur source. Finally, high-temperature annealing was performed to generate Fe5Ni4S. 8-x O x Electrocatalyst.

2. The Fe5Ni4S according to claim 1 8-x O x A method for preparing an electrocatalyst, characterized in that: The process includes the following steps: Step S1: Dissolve 2,5-dihydroxyterephthalic acid (C8H6O6), nickel nitrate (Ni(NO3)2), and ferrous chloride (FeCl2) in N,N-dimethylformamide (C3H7NO), and then transfer the solution to a 50 mL autoclave and heat to obtain the FeNi-MOF precursor. Step S2: Dissolve the FeNi-MOF precursor and thiourea CH4N2S in 30 mL of N,N-dimethylformamide C3H7NO, then transfer to a 50 mL autoclave and heat to obtain FeNi-MOF-S. Step S3: After high-temperature annealing of FeNi-MOF-S, Fe5Ni4S is obtained. 8-x O x Electrocatalyst.

3. The Fe5Ni4S according to claim 1 8-x O x A method for preparing an electrocatalyst, characterized in that: In step S1, the mass of 2,5-dihydroxyterephthalic acid is 0.08-0.09 g, the mass of nickel nitrate is 0.21-0.23 g, the mass of ferrous chloride is 0.12-0.13 g, and the volume of N,N-dimethylformamide is 30 mL.

4. The Fe5Ni4S according to claim 1 8-x O x A method for preparing an electrocatalyst, characterized in that: In step S1, the reaction conditions in the autoclave are: heating at 120°C for 20–24 hours.

5. The Fe5Ni4S according to claim 1 8-x O x A method for preparing an electrocatalyst, characterized in that: In step S2, the mass ratio of CH4N2S to FeNi-MOF precursor is 1:1, 1:2, or 1:

3.

6. The Fe5Ni4S according to claim 1 8-x O x A method for preparing an electrocatalyst, characterized in that: In step S2, the reaction conditions in the autoclave are: heating at 180°C for 10–12 h.

7. The Fe5Ni4S according to claim 1 8-x O x A method for preparing an electrocatalyst, characterized in that: In step S3, the annealing temperature is 500–600°C and the annealing time is 1–2 h.

8. A Fe5Ni4S 8-x O x Electrocatalyst, characterized in that: The Fe5Ni4S 8-x O x The electrocatalyst uses Fe5Ni4S as described in any one of claims 1-7. 8-x O x The Fe5Ni4S electrocatalyst was prepared using a specific method. 8-x O x The electrocatalyst involves oxygen atoms entering the Fe5Ni4S8 crystal lattice, replacing the S atom lattice sites and maintaining the pyrite structure of Fe5Ni4S8. 8-x O x Nanocrystalline materials.

9. A Fe5Ni4S as described in claim 8 8-x O x Electrocatalysts are used as oxygen evolution electrocatalysts in anion exchange membrane water electrolysis.

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