A chiral CoFe-based oxygen evolution electrocatalyst, its preparation method and application

Abstract

This invention relates to the field of electrocatalyst technology, and in particular to a chiral CoFe-based oxygen evolution electrocatalyst, its preparation method, and its application. Iron salts, cobalt salts, and chiral tartaric acid are dissolved together in N,N-dimethylformamide solvent to form a homogeneous mixed solution. Hydrazine hydrate is added to the mixed solution and thoroughly mixed. The solution is then transferred to a high-pressure reactor and subjected to a solvothermal reaction at a set temperature to obtain a nanocatalyst precursor. The nanocatalyst precursor is then subjected to centrifugation, washing, drying, and vacuum calcination to obtain the product. This method successfully prepares a chiral CoFe-based nanocatalyst through the inductive effect of chiral tartaric acid, combined with a specific solvothermal reaction and subsequent heat treatment process. This chiral CoFe-based electrocatalyst exhibits significantly enhanced catalytic activity and stability in the oxygen evolution electrocatalytic reaction, demonstrating superior electrochemical performance compared to achiral catalysts.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst technology, and in particular to a chiral CoFe-based oxygen evolution electrocatalyst, its preparation method, and its application. Background Technology

[0002] The oxygen evolution reaction (OER) is a crucial process in renewable energy conversion and storage systems, but its slow kinetics severely limit the efficiency of technologies such as water electrolysis for hydrogen production. While traditional noble metal catalysts (such as IrO2 and RuO2) possess excellent activity, their high cost and scarcity restrict their large-scale application. In recent years, transition metal (Fe, Co, Ni, etc.) based catalysts have become a research hotspot due to their low cost and tunable electronic structure. In particular, the Fe-Co bimetallic system can significantly enhance intrinsic activity through synergistic effects.

[0003] Chiral nanomaterials, due to their unique chirality-induced spin selectivity (CISS) effect, can achieve self-regulation of electrocatalytic reactions, generating polarization currents, reducing reaction overpotentials and energy barriers, and improving electrocatalytic efficiency. However, existing methods for synthesizing chiral catalysts (such as template methods and electrochemical deposition) generally suffer from problems such as complex processes and low chiral purity. Therefore, developing a Fe,Co bimetallic electrocatalyst with a simple process and controllable chiral structure to achieve high-efficiency OER performance remains an unsolved technical challenge. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the problems of complex catalyst preparation process and difficulty in chiral structure control in the prior art. By optimizing the metal precursor, chiral ligand and solvothermal reaction conditions, the controllable preparation of chiral CoFe-based electrocatalysts with specific chiral structures is realized.

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a chiral CoFe-based oxygen evolution electrocatalyst, comprising the following steps: S11: Dissolve iron salt, cobalt salt and chiral tartaric acid in an organic solvent to obtain the initial solution; S12: Add a reducing agent to the initial solution and react at 120-200℃ for 12-14 h to obtain a reaction solution; S13: The reaction solution is subjected to solid-liquid separation and vacuum calcination at 450-550℃ for 4-6 hours to obtain the chiral CoFe-based oxygen evolution electrocatalyst.

[0006] Preferably, the iron salt is one or more of ferric chloride, ferric nitrate, and ferric sulfate; the cobalt salt is one or more of cobalt chloride, cobalt nitrate, and cobalt sulfate; and the chiral tartaric acid is D-tartaric acid or L-tartaric acid (purchased from Maclean's). Tartaric acid molecules contain two identical chiral carbon atoms and exist in three stereoisomers: enantiomers D-tartaric acid and L-tartaric acid, and an optically inactive meso-tartaric acid. The D / L types have opposite optical rotation directions, and mixing equal amounts can form a racemic mixture. The difference in their spatial configurations leads to differences in optical rotation, coordination characteristics, and biological activity.

[0007] Preferably, in the initial solution, the molar ratio of iron salt, cobalt salt, and chiral tartaric acid is 0.5-2:0.5-2:1-3. The precursor solution is treated using a solvothermal method to induce the directional growth of the CoFe-based electrocatalyst under the induction of chiral tartaric acid. Upon completion of the reaction, a chiral CoFe-based electrocatalyst is obtained.

[0008] Preferably, the concentration of the solute in the initial solution is 10-40 mg / mL.

[0009] Preferably, the organic solvent is N,N-dimethylformamide (DMF), ethylene glycol (EG), or polyethylene glycol (PEG, molecular weight 200-600). DMF is a strongly polar aprotic solvent, and its core advantages in preparing electrocatalyst precursors are significant: excellent solubility for solutes such as metal salts and chiral tartaric acid, enabling uniform dispersion of components; high boiling point and slow volatilization, preventing coating cracking; and chemical and electrochemical inertness, not interfering with the catalytic system.

[0010] Preferably, the reducing agent is hydrazine hydrate, ethylenediamine, or ammonia, and the volume ratio of the reducing agent to the initial solution is 1-5:95-99.

[0011] The hydrazine hydrate was used as a reducing agent. The reaction precursor solution with added hydrazine hydrate was placed on a magnetic stirrer and mixed thoroughly. The uniformly mixed solution was transferred to a polytetrafluoroethylene reactor liner and sealed in a stainless steel high-pressure reactor. The product was obtained by solvothermal reaction under the set reaction temperature conditions.

[0012] Preferably, in step S13, the solid-liquid separation method involves centrifugation followed by washing with alcohol and water 3-6 times, and vacuum drying at 70-90°C for 5-7 hours. The obtained product is then washed sequentially with anhydrous ethanol and deionized water by centrifugation to remove unreacted substances and solvent residues. The washed product is then dried under vacuum to obtain the final chiral CoFe-based electrocatalyst.

[0013] The present invention also provides a chiral CoFe-based oxygen evolution electrocatalyst prepared by the above-described method. This catalyst possesses a spherical nanostructure and exhibits excellent electrocatalytic activity in the OER reaction.

[0014] The present invention also provides an application of the above-mentioned chiral CoFe-based oxygen evolution electrocatalyst in water electrolysis.

[0015] Preferably, the application employs a three-electrode system, using the chiral CoFe-based oxygen evolution electrocatalyst as the working electrode, a Hg / HgO electrode as the reference electrode, and a platinum sheet electrode as the counter electrode. This three-electrode system is suitable for alkaline water electrolysis catalysis: the working electrode supports the electrocatalyst under test, accurately characterizing its intrinsic hydrogen / oxygen evolution catalytic activity; the Hg / HgO reference electrode is suitable for strongly alkaline environments, providing a stable, non-polarized potential reference; the platinum sheet counter electrode has high inertness and good conductivity, only closing the conductive circuit and not interfering with the test.

[0016] Compared with the prior art, the above-described technical solution of the present invention has the following advantages: 1. This invention uses chiral tartaric acid as a ligand and achieves chiral regulation of Fe,Co bimetallic nanocatalysts under mild conditions through a solvothermal method, solving the problems of cumbersome synthesis steps and unstable structure of traditional chiral catalysts.

[0017] 2. By optimizing the ratio of metal salt to chiral ligand, reaction temperature and time, the morphology and chiral characteristics of the catalyst can be precisely controlled, and the resulting product has a high specific surface area and abundant active sites.

[0018] 3. This catalyst exhibits enantioselective catalytic performance in the OER reaction, providing a new approach for the development of chiral electrocatalytic materials.

[0019] 4. The preparation method is simple and reproducible, suitable for large-scale production, and has broad application prospects in the field of energy conversion and storage. Attached Figure Description

[0020] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0021] Figure 1 Scanning electron microscope (SEM) image of the CoFe-based electrocatalyst in Example 1; Figure 2 Scanning electron microscope image of the CoFe-based electrocatalyst in Example 2; Figure 3 Scanning electron microscope image of the CoFe-based electrocatalyst in Example 3; Figure 4 Comparison of linear sweep voltammetry (LSV) curves of the OER reaction in 1 M KOH electrolyte for Examples 1, 2 and 3; Figure 5Comparison of Tafel slopes of the OER reaction in 1 M KOH electrolyte for Examples 1, 2, and 3; Figure 6 Circular dichroism (CD) spectra of the CoFe-based electrocatalysts in Examples 1, 2 and 3. Detailed Implementation

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0023] Example 1: Preparation method of levorotatory chiral CoFe-based electrocatalyst Step 1: Dissolve 0.5 mmol ferric chloride (FeCl3), 0.5 mmol cobalt chloride (CoCl2) and 1 mmol L-tartaric acid in 20 mL of N,N-dimethylformamide (DMF) and stir magnetically for 30 minutes to form a homogeneous initial solution.

[0024] Step 2: Slowly add 0.2 mL of hydrazine hydrate (N2H4·H2O, 1% by volume) to the initial solution and stir continuously for 1 hour to obtain a dark red reaction precursor solution.

[0025] Step 3: Transfer the precursor solution to a 50 mL polytetrafluoroethylene liner, seal it in a stainless steel reactor, and place it in an oven at 180°C for 12 hours.

[0026] Step 4: After the reaction is completed, the product is naturally cooled and washed by alternating centrifugation with anhydrous ethanol and deionized water (8000 rpm, 5 minutes × 3 times). After vacuum drying at 80℃ for 6 hours, it is calcined at 500℃ for 5 hours to obtain a chiral CoFe-based catalyst with a spherical structure.

[0027] Example 2: Preparation method of dextrorotatory chiral CoFe-based electrocatalyst The difference between this embodiment and Example 1 is as follows: In step one, D-tartaric acid is used instead of L-tartaric acid, and 0.5 mmol of ferric chloride (FeCl3), 0.5 mmol of cobalt chloride (CoCl2) and 1.5 mmol of D-tartaric acid are dissolved in 20 mL; in step two, the amount of hydrazine hydrate added is increased to 0.5 mL (2.5% by volume); in step three, the reaction temperature is adjusted to 160℃, the reaction time is extended to 14 hours, the product is collected after washing, vacuum dried at 80℃ for 6 hours, and then calcined at 500℃ for 5 hours; finally, a dextrorotatory CoFe-based electrocatalyst with a spherical structure is obtained.

[0028] Example 3: As a chiral comparative example Step 1: Weigh 2.0 mmol of FeCl3, 0.5 mmol of CoCl2·6H2O and 3.0 mmol of L-tartaric acid, add them to 25 mL of DMF solvent, and stir magnetically for 40 minutes until completely dissolved.

[0029] Step 2: Slowly add 0.75 mL of hydrazine hydrate at a rate of 0.1 mL / min and continue stirring for 2 hours to form a homogeneous precursor solution.

[0030] Step 3: Transfer the mixture to a 100 mL reactor and react at 200℃ for 12 hours with a heating rate of 5℃ / min.

[0031] Step 4: After the reaction is complete, allow the mixture to cool naturally, centrifuge to collect the product, and wash it three times each with ethanol and deionized water.

[0032] Step 5: After vacuum drying at 80℃ for 6 hours, calcination at 500℃ for 5 hours yields a black powdered catalyst.

[0033] Application example: Electrochemical performance tests were conducted on Examples 1, 2, and 3 using 1 M KOH as the electrolyte at 26°C. The reference electrode was a Hg / HgO electrode, and the counter electrode was a platinum sheet electrode. The constant voltage range was 1.2–1.8 V vs. RHE, and the current density was 100–200 mA / cm². 2 .

[0034] In Example 1, the scanning electron microscope image of the left-handed chiral CoFe-based electrocatalyst prepared in this example is shown below. Figure 1 As shown, the electrochemical linear scan voltammetry curve and Tafel slope are as follows: Figure 4 As shown in Example 1 of 5.

[0035] In Example 2, SEM showed that the product had a spherical structure of 200-300 nm. The SEM image of the dextrorotatory chiral CoFe-based electrocatalyst prepared in this example is shown below. Figure 2 As shown, the electrochemical linear sweep voltammetry curve and Tafel slope are as follows: Figure 4 and 5 As shown in Example 2.

[0036] In Example 3, SEM showed that the product had a spherical structure of 200-300 nm. The scanning electron microscope image of the non-chiral CoFe-based electrocatalyst prepared in this example is shown below. Figure 3 As shown, the electrochemical linear scan voltammetry curve and Tafel slope are as follows: Figure 4 and 5 As shown in Example 3.

[0037] According to the preparation method of the chiral CoFe-based electrocatalyst described in the above embodiments, in a non-aqueous solvent (DMF) system, the chiral center and its α-hydroxycarboxylic acid structure in the chiral tartaric acid molecule can react with Co in the solution. 2+ and Fe 3+ Metal ions (or other valence states) directly undergo strong coordination to form metal-tartaric acid complex precursors with chiral configurations.

[0038] Under hydrothermal conditions, this chiral coordination environment is effectively transferred and locked into the final CoFe bimetallic oxide / (hydroxy)oxide lattice. This chiral nanostructure can efficiently induce chiral-induced spin selectivity (CISS) effect: on the one hand, the chiral lattice acts as a spin filter, preferentially transferring electrons with specific spin directions, optimizing the adsorption / desorption process of oxygen intermediates, and directly reducing the overpotential of the oxygen evolution reaction (OER); on the other hand, the synergistic effect between Fe-Co bimetals (such as optimizing charge transfer and regulating the electron density of active sites) indirectly accelerates the reaction kinetics. Therefore, the chiral CoFe-based electrocatalyst prepared by this method exhibits excellent OER performance, with its catalytic activity and stability significantly superior to the corresponding achiral CoFe catalyst, showing important application prospects in fields such as high-efficiency water splitting devices and renewable energy storage and conversion systems.

[0039] Furthermore, the above preparation method is simple and efficient, employing a one-step solvothermal process. The core raw material, chiral tartaric acid, is a natural chiral molecule, abundant in source, inexpensive, and with a simple synthesis process. This effectively solves the technical challenges of complex synthesis processes and difficulty in controlling the purity of chiral structures in existing chiral catalysts, making it highly beneficial for the large-scale, low-cost preparation of this chiral CoFe-based electrocatalyst.

[0040] Furthermore, the chiral CoFe-based oxygen evolution electrocatalyst prepared according to the methods described in the above embodiments achieves highly efficient CISS effect spin modulation and optimized bimetallic electronic structure through its intrinsic chiral lattice. Compared to CoFe catalysts of the same composition but without a chiral structure, this chiral catalyst achieves a high efficiency of 10 mA cm⁻¹. -2 At the OER current density, the overpotential decreased significantly to 290 mV, and the Tafel slope was 38.32 mV dec. -1 It has become a highly promising high-performance oxygen evolution catalyst and a highly efficient electron spin filter material.

[0041] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a chiral CoFe-based oxygen evolution electrocatalyst, characterized in that, Includes the following steps: S11: Dissolve iron salt, cobalt salt and chiral tartaric acid in an organic solvent to obtain the initial solution; S12: Add a reducing agent to the initial solution and react at 120-200℃ for 12-14 h to obtain a reaction solution; S13: The reaction solution is subjected to solid-liquid separation and vacuum calcination at 450-550℃ for 4-6 h to obtain the chiral CoFe-based oxygen evolution electrocatalyst.

2. The preparation method according to claim 1, characterized in that: The iron salt is one or more of ferric chloride, ferric nitrate, and ferric sulfate; the cobalt salt is one or more of cobalt chloride, cobalt nitrate, and cobalt sulfate; and the chiral tartaric acid is D-tartaric acid or L-tartaric acid.

3. The preparation method according to claim 1, characterized in that: In the initial solution, the molar ratio of iron salt, cobalt salt and chiral tartaric acid is 0.5-2:0.5-2:1-3.

4. The preparation method according to claim 1, characterized in that: The concentration of the solute in the initial solution is 10-40 mg / mL.

5. The preparation method according to claim 1, characterized in that: The organic solvent is N,N-dimethylformamide, ethylene glycol, or polyethylene glycol.

6. The preparation method according to claim 1, characterized in that: The reducing agent is hydrazine hydrate, ethylenediamine, or ammonia, and the volume ratio of the reducing agent to the initial solution is 1-5:95-99.

7. The preparation method according to claim 1, characterized in that: In step S13, the solid-liquid separation method is to centrifuge the solid, wash it with alcohol and water 3-6 times, and then vacuum dry it at 70-90℃ for 5-7 hours.

8. A chiral CoFe-based oxygen evolution electrocatalyst prepared by the preparation method according to any one of claims 1-7.

9. The application of the chiral CoFe-based oxygen evolution electrocatalyst of claim 8 in water electrolysis.

10. The application in water electrolysis according to claim 9, characterized in that: The application employs a three-electrode system, using the chiral CoFe-based oxygen evolution electrocatalyst as the working electrode, a Hg / HgO electrode as the reference electrode, and a platinum sheet electrode as the counter electrode.

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