A chiral cobalt-nickel bimetallic electrocatalyst with high spin polarizability, its catalytic electrode, its preparation method, and its application.

Abstract

This invention discloses a chiral cobalt-nickel bimetallic electrocatalyst with high spin polarization, a catalytic electrode, its preparation method, and its applications, relating to the field of catalysis technology. The preparation method includes the following steps: a first mixture is subjected to a solvothermal reaction to obtain the chiral cobalt-nickel bimetallic electrocatalyst. The first mixture comprises a solvent, a cobalt salt, a nickel salt, and cysteine, wherein the cysteine ​​is L-cysteine ​​or D-cysteine. This invention uses a simple solvothermal method to transfer the chirality of cysteine ​​to the surface of a cobalt-nickel bimetallic metal through chemical bonding, preparing a chiral cobalt-nickel bimetallic electrocatalyst. This electrocatalyst exhibits good chiral optical response, numerous active sites, high spin polarization efficiency, the ability to suppress the formation of the byproduct H₂O₂, low overpotential, and excellent electrocatalytic activity for the oxygen evolution reaction.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to a chiral cobalt-nickel bimetallic electrocatalyst with high spin polarization, a catalytic electrode, and its preparation method and application. Background Technology

[0002] Electrocatalytic water splitting technology plays a crucial role in driving sustainable energy conversion, providing a reliable pathway to significantly reduce dependence on traditional fossil fuels. To achieve optimal electrochemical oxygen evolution reaction (OER), researchers typically employ strategies such as metal doping, single-atom engineering, electrochemical surface reconstruction, and screening of different metal elements. Recently, electron spin modulation of the OER process has attracted widespread interest, particularly the reaction intermediate OH... - In the ground state, the process is a spin singlet state, a two-electron transfer process, which favors the formation of the byproduct H2O2. However, the target product O2 exhibits a spin triplet configuration in the ground state, which is a four-electron transfer process. Therefore, there is a spin imbalance in the OER process, resulting in slow kinetics and requiring a large overpotential to achieve a sufficient operating current, thus leading to considerable energy loss in the water electrolyzer.

[0003] To address the performance bottleneck caused by spin imbalance, a method for regulating spin states through the chirality-induced spin selectivity (CISS) effect has been proposed. This effect allows electrons to undergo spin polarization during transport through a chiral system, achieving spin selection without the need for an external magnetic field. Previous studies have utilized double-stranded DNA oligomers, oligopeptides, or chiral nanoparticles to modify catalyst surfaces and regulate electron spin direction through the CISS effect, thereby optimizing the adsorption and conversion of oxygen intermediates during the OER process. Recently, the CISS effect has been applied to sustainable energy conversion applications. Many research teams have coated chiral molecules onto metal oxide films (TiO2, CuO, CoO, Fe3O4). Compared to achiral catalysts, the spin polarization achieved by the CISS effect significantly improves the electrocatalytic OER kinetics, increases current density, and suppresses the formation of the byproduct H2O2, thus improving overall energy efficiency. These pioneering works have laid a solid foundation for subsequent research.

[0004] However, chiral metal oxides exhibit limited catalytic activity in OER reactions due to kinetic constraints and low spin polarization efficiency, which hinders their further development. Furthermore, the complex preparation processes of existing chiral catalysts impede the chiral transfer of chiral organic molecules to the final target product.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a chiral cobalt-nickel bimetallic electrocatalyst with high spin polarization, a catalytic electrode, and its preparation method and application. The aim is to provide a simple method for preparing a chiral cobalt-nickel bimetallic electrocatalyst with good OER catalytic activity and excellent spin polarization effect.

[0007] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a method for preparing a chiral cobalt-nickel bimetallic electrocatalyst, such as... Figure 1 As shown, the process includes the following steps: S1. Provide a first mixture, the first mixture comprising a solvent, a cobalt salt, a nickel salt and cysteine, wherein the cysteine ​​is L-cysteine ​​or D-cysteine; S2. After subjecting the first mixture to a solvothermal reaction (specifically a hydrothermal reaction, in which the solvent is water), the chiral cobalt-nickel bimetallic electrocatalyst is obtained.

[0008] In this invention, during the solvothermal reaction, a CoNi alloy is formed. At the same time, the functional groups such as thiol (-SH), amino (-NH2), and carboxyl (-COOH) in the cysteine ​​molecule are adsorbed onto the surface of the CoNi bimetallic through chemical bonding, achieving stable anchoring and realizing chiral transfer.

[0009] This invention combines high spin polarization achieved through the CISS effect with an OER catalyst. Chirality is induced by the chiral ligand cysteine, and then transferred to the CoNi bimetallic catalyst via chemical bonding. Specifically, a simple and convenient one-pot solvothermal method is used to transfer the chirality of cysteine ​​to the CoNi bimetallic surface through chemical bonding, constructing an amorphous chiral bimetallic cobalt-nickel-based electrocatalyst. This invention utilizes the CoNi bimetallic catalyst, which has good conductivity and a large active area, accelerating the interfacial electron transfer rate and providing more active sites for the OER reaction, thus improving overall catalytic performance and overcoming the limitations of existing chiral oxide catalysts in OER kinetics. Furthermore, the chiral cobalt-nickel bimetallic electrocatalyst provided by this invention can generate a spin polarization effect, thereby reducing the formation of the byproduct H₂O₂ and optimizing the electrocatalytic OER reaction process. The excellent spin polarization efficiency and good electron conduction of the chiral cobalt-nickel bimetallic electrocatalyst give it outstanding OER activity.

[0010] The use of cysteine ​​as a chiral ligand in this invention has the following effects: (1) Highly efficient and stable chiral induction: Due to the adsorption of functional groups such as thiol (-SH), amino (-NH2) and carboxyl (-COOH) of cysteine ​​on the surface of CoNi bimetal through chemical bonding, stable anchoring is achieved, ensuring efficient chiral transfer and maintaining structural stability.

[0011] (2) Chiral CoNi bimetallic electrocatalysts exhibit excellent spin polarization effects, enhancing OER reaction activity: The superior spin polarization effect induced by chirality (reaching 88% for L-type chiral CoNi bimetallic electrocatalysts and 81% for D-type chiral CoNi bimetallic electrocatalysts) reduces the generation of the byproduct H2O2, promotes OER reaction kinetics, and makes chiral CoNi bimetallic electrocatalysts high-performance OER electrocatalysts. At an overpotential of 509 mV, the OER current densities of L-type chiral CoNi bimetallic electrocatalysts, D-type chiral CoNi bimetallic electrocatalysts, and non-chiral CoNi bimetallic electrocatalysts are 136, 146, and 100 mA·cm, respectively. -2 The OER current density of the D-type chiral CoNi bimetallic electrocatalyst is 46% higher than that of the non-chiral CoNi bimetallic electrocatalyst.

[0012] (3) Strong compatibility with solvothermal method: On the one hand, the thiol, amino and carboxyl groups in cysteine ​​molecules have good thermal stability and will not decompose at hydrothermal 130 ℃, thus preserving the chemical bonding activity with cobalt-nickel groups. On the other hand, the strong coordination ability of cysteine ​​means that no additional dispersant or surfactant is needed during the hydrothermal process, thus reducing the probability of sample contamination.

[0013] In one embodiment of the present invention, the temperature of the solvothermal reaction is 100~200 °C, and the time of the solvothermal reaction is 6~18 h.

[0014] For example, the temperature of the solvothermal reaction can be 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃, 170 ℃, 180 ℃, 190 ℃ or 200 ℃, etc., and the time of the solvothermal reaction can be 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h or 18 h, etc.

[0015] In one embodiment of the present invention, the cobalt salt includes at least one of cobalt nitrate, cobalt chloride, cobalt sulfate, and cobalt phosphate, and the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate.

[0016] In this embodiment, the cobalt and nickel salts may or may not contain water of crystallization; that is, the present invention does not limit the hydration state of the salts. Whether or not they contain water of crystallization, and the amount of water, depends specifically on the actual situation of each salt in its stable state. For example, cobalt chloride, cobalt phosphate, and nickel sulfate may or may not contain water of crystallization. Cobalt chloride with water of crystallization can be cobalt chloride hexahydrate, cobalt phosphate with water of crystallization can be cobalt phosphate octahydrate, and nickel sulfate with water of crystallization can be nickel sulfate hexahydrate, etc.

[0017] For example, a cobalt salt containing water of crystallization may be at least one of cobalt nitrate hexahydrate, cobalt chloride hexahydrate, cobalt sulfate monohydrate, cobalt sulfate heptahydrate, and cobalt phosphate octahydrate, and a nickel salt containing water of crystallization may be at least one of nickel nitrate hexahydrate, nickel chloride hexahydrate, nickel sulfate hexahydrate, nickel sulfate heptahydrate, and nickel acetate tetrahydrate.

[0018] In one embodiment of the present invention, the molar ratio of the cobalt salt, nickel salt, and cysteine ​​is (1~8):(1~6):(5~21). For example, the molar ratio of the cobalt salt, nickel salt, and cysteine ​​can be 1:1:5, 1:1:10, 1:1:20, 1:3:5, 1:3:10, 1:3:20, 1:3:21, 1:6:5, 1:6:10, 1:6:20, 1:6:21, 4:1:5, 4:1:10, 4:1:20, 4:1:21, 8:1:5, 8:1:10, 8:1:20, or 8:1:21, etc.

[0019] In one embodiment of the present invention, the solvent includes at least one selected from water, methanol, isopropanol, and ethanol.

[0020] When water is used as the solvent, the corresponding reaction is a hydrothermal reaction.

[0021] In a second aspect, the present invention provides a chiral cobalt-nickel bimetallic electrocatalyst, wherein the chiral cobalt-nickel bimetallic electrocatalyst is prepared by the preparation method of the present invention as described above, and the chiral cobalt-nickel bimetallic electrocatalyst has a chiral induced spin selectivity effect.

[0022] A third aspect of the present invention provides a catalytic electrode, wherein the catalytic electrode comprises a conductive support and a catalyst supported on the conductive support, the catalyst being a chiral cobalt-nickel bimetallic electrocatalyst as described above.

[0023] A fourth aspect of the present invention provides a method for preparing the catalytic electrode of the present invention as described above, comprising the following steps: A second mixture is provided, the second mixture comprising a solvent, a cobalt salt, a nickel salt, and cysteine, wherein the cysteine ​​is L-cysteine ​​or D-cysteine; A conductive support is placed in the second mixture, and then a solvothermal reaction is carried out to obtain the catalytic electrode.

[0024] In this invention, the selection of solvent, cobalt salt, and nickel salt in the second mixture is the same as that in the selection of solvent, cobalt salt, and nickel salt in the first mixture described above. The temperature and time of the solvothermal reaction are the same as those used in the preparation of the chiral cobalt-nickel bimetallic electrocatalyst described above.

[0025] This invention provides a simple and convenient one-pot solvothermal method for in-situ preparation of a chiral cobalt-nickel bimetallic electrocatalyst on a conductive support, yielding a catalytic electrode. During the reaction, the chirality of cysteine ​​is transferred to the CoNi bimetallic surface through chemical bonding. The catalytic electrode prepared by the method provided in this invention exhibits spin polarization, thereby reducing the formation of the byproduct H₂O₂, demonstrating high spin polarization efficiency and good electron conductivity, resulting in excellent OER activity. For the catalytic electrode of the L-type chiral cobalt-nickel bimetallic electrocatalyst, its performance at 10 mA·cm⁻¹ is [not specified in the original text]. -2 50 mA·cm -2 100mA·cm -2 The overpotentials at current densities were 125 mV, 240 mV, and 392 mV, respectively; for the catalytic electrode of the D-type chiral cobalt-nickel bimetallic electrocatalyst, its overpotential at 10 mA·cm⁻¹ was... -2 50 mA·cm -2 100 mA·cm -2 The overpotentials at the current densities are 125 mV, 244 mV and 367 mV, respectively.

[0026] Furthermore, compared to other chiral ligands (such as tartaric acid, phenylalanine, tryptophan, etc.), the use of L-cysteine ​​or D-cysteine ​​as chiral ligands in this invention has a more significant chiral enhancement effect on OER activity, resulting in a catalytic electrode with lower overpotential and better OER activity. This is mainly because tartaric acid, due to its strong acidity, decomposes the conductive support such as nickel foam during solvothermal processes, making it unsuitable for solvothermal preparation methods. The catalytic electrode prepared by electrodeposition using tartaric acid as a chiral ligand in this invention exhibits OER activity at 10 mA·cm⁻¹. -2 The overpotential at the current density is 249 mV. A catalytic electrode prepared by solvothermal method using phenylalanine as a chiral ligand exhibits an overpotential of 249 mV at 10 mA·cm⁻¹. -2 The overpotential at the current density is 136 mV; however, the steric hindrance of the indole ring in the tryptophan (Trp) molecule hinders electron transfer, thus affecting the OER activity of the catalytic electrode. The catalytic electrode prepared by solvothermal method using tryptophan as a chiral ligand exhibits OER activity at 10 mA·cm⁻¹. -2The overpotential at the current density is 357 mV. This demonstrates that, compared to other chiral ligands, using cysteine ​​as the chiral ligand at 10 mA·cm⁻¹ exhibits superior performance at this current density. -2 The overpotential is reduced to 125 mV.

[0027] In one embodiment of the present invention, the conductive carrier includes nickel foam, titanium foam, indium tin oxide (ITO) conductive glass, fluorine-doped tin oxide (FTO) conductive glass, and Ti3C2T. x At least one of carbon cloth.

[0028] In a fifth aspect, the present invention provides the application of the chiral cobalt-nickel bimetallic electrocatalyst described above or the catalytic electrode described above in the present invention in the catalytic oxygen evolution reaction.

[0029] Compared with the prior art, the present invention has the following advantages and technical effects: (1) Excellent OER Activity: This invention prepares chiral cobalt-nickel bimetallic electrocatalysts or catalytic electrodes through the chemical bonding between chiral cysteine ​​and cobalt-nickel based metals. High spin polarization efficiency is achieved by leveraging the chiral-induced spin selectivity effect, effectively promoting the generation of the target product, triplet oxygen, and exhibiting excellent OER activity. Specifically, the prepared L-type chiral CoNi bimetallic electrocatalyst achieves a spin polarization rate of 88%, effectively suppressing the generation of the byproduct H2O2 and significantly improving energy conversion efficiency. The catalytic electrode of the prepared L-type CoNi bimetallic electrocatalyst exhibits excellent OER activity at 10 mA·cm⁻¹. -2 50 mA·cm -2 100 mA·cm -2 At current densities, they exhibit low overpotentials of 125 mV, 240 mV, and 392 mV, respectively.

[0030] (2) Abundant active sites: The solvothermal method forms an interwoven and stacked flower-like cluster structure, which greatly increases the number of exposed catalytic active sites; at the same time, the three-dimensional structure promotes the reaction of reactants (OH-). - The rapid diffusion of the active site and product (O2) reduces mass transfer resistance and improves the contact efficiency between the active site and the reactant.

[0031] (3) Excellent process scalability and cost advantages: The electrocatalyst and catalytic electrode of the present invention are constructed based on non-precious metals Co and Ni, as well as chiral cysteine, which is readily available and inexpensive. The preparation process adopts a solvothermal method, which is convenient to operate, requires no complex equipment, is suitable for large-scale production, and has good economic benefits and industrial application prospects.

[0032] (4) Highly efficient electron transport performance: The prepared catalytic electrode uses a highly conductive substrate as a support, and the stable coordination effect of the chiral ligand and the cobalt-nickel bimetallic catalyst ensures the rapid conduction of spin-polarized electrons. This system effectively reduces the interfacial charge transfer resistance and further enhances the kinetic performance of the OER reaction. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the preparation process of a chiral cobalt-nickel bimetallic electrocatalyst.

[0034] Figure 2 The images shown are SEM images of different catalytic electrodes in Example 1, where (a) is the SEM image of chiral L-Cys-CoNi / NF, (b) is the SEM image of chiral D-Cys-CoNi / NF, and (c) is the SEM image of achiral DL-Cys-CoNi / NF.

[0035] Figure 3 In the diagram, (a) is a TEM image of chiral L-Cys-CoNi in Example 1, (b) is a surface scan distribution map of element C, (c) is a surface scan distribution map of element O, (d) is a surface scan distribution map of element S, (e) is a surface scan distribution map of element Co, and (f) is a surface scan distribution map of element Ni.

[0036] Figure 4 (a) is the circular dichroism spectrum of chiral L-Cys-CoNi, chiral D-Cys-CoNi, and achiral DL-Cys-CoNi in Example 1. (b) is the result of spectrophotometric detection of the byproduct H2O2 after electrolysis of chiral L-Cys-CoNi / NF and achiral DL-Cys-CoNi / NF for a certain period of time at an OER potential of 1.6V.

[0037] Figure 5 The images show the atomic force microscopy (IV) characterization results of different samples in Example 1, where (a) is the average IV curve of the chiral L-Cys-CoNi film in the range of -7 V to +7 V, (b) is the average IV curve of the chiral D-Cys-CoNi film in the range of -7 V to +7 V, and (c) is the average IV curve of the achiral DL-Cys-CoNi film in the range of -7 V to +7 V.

[0038] Figure 6 The graphs show the electrochemical test results of chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF in Example 1. (a) shows the LSV test results, and (b) shows the results at 10 mA·cm⁻¹. -2 50 mA·cm -2100mA·cm -2 The overpotential results under current density are shown in (c) and (d) are the results of the Tafel slope test.

[0039] Figure 7 The graphs show the OER test results for the solvothermal L-Cys-CoNi / NF in Example 1, the electrodeposition L-Cys-CoNi / NF in Comparative Example 1, the solvothermal L-Trp-CoNi / NF in Comparative Example 2, the solvothermal L-Pheny-CoNi / NF in Comparative Example 3, and the electrodeposition L-TA-CoNi / NF in Comparative Example 4. (a) shows the LSV test results, and (b) shows the results at 10 mA·cm⁻¹. -2 The overpotential results under current density are shown in the figure. Detailed Implementation

[0040] This invention provides a chiral cobalt-nickel bimetallic electrocatalyst with high spin polarizability, a catalytic electrode, its preparation method, and its applications. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0042] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0043] The present invention will be further described below through specific embodiments.

[0044] In the following embodiments, unless otherwise specified, the raw materials, equipment, etc. used are all commercially available products.

[0045] In the following examples, the thickness of the nickel foam (NF) used is 1.5 mm.

[0046] Example 1 This embodiment uses a solvothermal method (specifically a hydrothermal method) to prepare the catalytic electrode, which includes the following steps: (1) Pretreatment: Cut NF into rectangles 2 cm long and 1 cm wide (planar dimensions: 1.0 cm × 2.0 cm), then immerse the NF in 3.0 M hydrochloric acid and sonicate for 10 minutes. This step is to remove the oxide layer on the surface of the nickel foam, which is beneficial for the in-situ growth of the catalyst. After sonication, rinse with ultrapure water, then sonicate with acetone, ethanol and ultrapure water for 5 minutes in sequence, and then dry for later use.

[0047] (2) Preparation of precursor solution: 72.7 mg nickel nitrate hexahydrate (Ni(NO3)2·6H2O) and 217.5 mg cobalt nitrate hexahydrate (Co(NO3)2·6H2O) were dissolved in 10 mL of ultrapure water to obtain the precursor solution.

[0048] (3) Hydrothermal reaction: 608 mg of L-cysteine ​​(L-Cys) was dispersed in 10 mL of ultrapure water to obtain an L-Cys solution. The L-Cys solution was then dispersed into the precursor solution under magnetic stirring for 10 minutes to obtain a mixture. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene (PTFE), and a clean piece of NF was placed against the reactor wall at a certain angle. Finally, the high-pressure reactor was sealed and kept at 130 °C for 10 hours. After natural cooling to room temperature, a chiral cobalt-nickel bimetallic electrocatalyst (i.e., chiral L-Cys-CoNi) was formed on the NF.

[0049] (4) Product washing: The obtained product was washed 4 times with ultrapure water and ethanol alternately to remove all uncoordinated free cysteine ​​ligands and impurities, and then dried under vacuum at 50 °C for 6 h to obtain a catalytic electrode (denoted as chiral L-Cys-CoNi / NF, which includes NF and chiral L-Cys-CoNi supported on NF). This catalytic electrode can be directly used as the working electrode for electrochemical testing.

[0050] Using the same method as above, except that L-cysteine ​​(L-Cys) is replaced with D-cysteine ​​(D-Cys), a catalytic electrode is obtained, denoted as chiral D-Cys-CoNi / NF (which includes NF and chiral D-Cys-CoNi supported on NF).

[0051] In contrast, the same method as above was used, except that L-cysteine ​​(L-Cys) was replaced with DL-cysteine ​​(DL-Cys) to obtain a catalytic electrode, denoted as achiral DL-Cys-CoNi / NF (which includes NF and achiral DL-Cys-CoNi supported on NF).

[0052] test: (1) The chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF were characterized by scanning electron microscopy (SEM); the electrocatalyst on the NF in the chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF was collected by scraping, and the resulting powders (chiral L-Cys-CoNi, chiral D-Cys-CoNi, and achiral DL-Cys-CoNi) were characterized by transmission electron microscopy (TEM). The results are as follows: Figure 2 and Figure 3 As shown.

[0053] Depend on Figure 2 As shown in (a) and (b), the microstructure of the chiral cobalt-nickel bimetallic electrocatalysts (chiral L-Cys-CoNi and chiral D-Cys-CoNi) is a three-dimensional, flower-like cluster structure with interwoven stacking. Figure 2 As shown in (c), the achiral cobalt-nickel bimetallic electrocatalyst (achiral DL-Cys-CoNi) exhibits a stacked nanoparticle morphology. These structural differences indicate that cysteine ​​molecules play a crucial regulatory role in the morphology of the cobalt-nickel-based nanostructure, altering the electrocatalyst's microstructure characteristics and contributing to a larger active surface area, thus promoting the reaction of OH- (OH-) - The rapid diffusion of O2 and the product reduces mass transfer resistance and promotes the exposure of active sites during the catalytic reaction.

[0054] Figure 3 Image (a) is a TEM image of chiral L-Cys-CoNi, with a scale bar of 200 nm. Figure 3 (b) to (f) are the elemental surface scan distribution maps, showing that the corresponding elements C, O, S, Co and Ni are uniformly and clearly distributed, confirming the successful synthesis of chiral L-Cys-CoNi.

[0055] (2) To investigate the chiral transfer of cysteine ​​molecules to the CoNi bimetallic structure and its chiral optical response, circular dichroism spectroscopy was performed on chiral L-Cys-CoNi, chiral D-Cys-CoNi, and achiral DL-Cys-CoNi to detect the differences in absorption of left-handed and right-handed circularly polarized light. The results are as follows: Figure 4 As shown in (a) of the diagram.

[0056] Depend on Figure 4As shown in (a), the circular dichroism (CD) spectra of chiral L-Cys-CoNi and chiral D-Cys-CoNi exhibit good mirror-symmetric signals in the approximately 200-275 nm range, reflecting the difference in optical response between the chiral enantiomers. In contrast, the CD signal of the achiral DL-Cys-CoNi is almost flat, indicating that racemic DL cysteine, due to chiral cancellation, does not impart a chiral optical response to DL-Cys-CoNi. This result confirms that the molecular chirality of L-Cys and D-Cys is successfully transferred to the CoNi bimetal, and that L-Cys-CoNi and D-Cys-CoNi possess good chiral optical responses.

[0057] (3) To investigate the inhibitory effect of chiral L-Cys-CoNi / NF on the formation of the byproduct H2O2 in the OER reaction and its chiral OER-enhancing effect, this invention uses o-toluidine as a redox indicator. At a potential of 1.6 V, chiral L-Cys-CoNi / NF and achiral DL-Cys-CoNi / NF were electrolyzed in an electrolyte for a certain period of time, and the generation of H2O2 as a catalyst in the OER process was detected by spectrophotometry. Specifically, chiral L-Cys-CoNi / NF and achiral DL-Cys-CoNi / NF were used as working electrodes, and graphite rods and Hg2Cl2 / Hg were used as counter electrodes and reference electrodes, respectively. Coulometric electrolysis was performed in an electrolyte, wherein the electrolyte was 0.1 M Na2SO4 solution (50 mL, pH=6.5). After electrolysis for 30 minutes, 3.2 mL of electrolyte was mixed with 0.8 mL of 0.1% (w / v) o-toluidine solution (containing 1.0 M HCl), and the mixture was developed in the dark for 10 minutes. Finally, the absorption spectrum of the mixed solution was measured in the range of 300-600 nm using a UV-Vis spectrophotometer.

[0058] The results are as follows Figure 4 As shown in (b), the achiral DL-Cys-CoNi / NF exhibits a distinct absorption peak at 445 nm, while the absorption peak of the chiral L-Cys-CoNi / NF is significantly weakened at this point. This indicates that the chiral L-Cys-CoNi / NF modulates the OH group through a chirality-induced spin selectivity effect. - The spin electrons of the intermediate are aligned in the same parallel direction, which restricts the two-electron reaction process for the formation of H2O2 and promotes the four-electron reaction process for the formation of the target product O2; while for the achiral DL-Cys-CoNi / NF, OH - The intermediate's spin electrons are randomly distributed, with antiparallel OH groups... -The intermediate generates the byproduct H2O2, a process that reduces OER activity. Characterization results confirm that chiral L-Cys-CoNi / NF enhances the four-electron reaction selectivity of OER and reduces the formation of the byproduct H2O2, providing reaction pathway-level support for improving its OER activity.

[0059] (4) To further elucidate the spin polarization effect of the chiral cobalt-nickel bimetallic electrocatalyst, its spin polarization charge transport characteristics were quantified using magnetic permeability probe atomic force microscopy. Electrocatalysts (chiral L-Cys-CoNi, chiral D-Cys-CoNi, and achiral DL-Cys-CoNi, respectively) were uniformly dispersed on an ITO substrate using a drop-coating method to form a smooth thin film. Magnetic conductive probes with a CoCr coating were used for testing. Before testing, multiple probes were magnetized for 10 minutes in either an upward (+500 Oe) or downward (-500 Oe) direction using a permanent magnet. During testing, varying voltages were applied to the magnetized probe tips and the ITO substrate supporting the electrocatalyst, and the corresponding current-voltage (IV) curves were recorded at 20 locations and averaged. Through the spin polarization effect of the chiral cobalt-nickel bimetallic electrocatalyst, the current significantly increased when the electron spin direction was aligned with the magnetic field direction; conversely, the current was suppressed when the magnetic field direction was inconsistent with the spin-filtering electron direction. Spin polarizability can be used to quantify the anisotropy of polarization current, and its calculation formula is as follows: (1) Among them, I up with I down These represent the current values ​​when the probe is magnetized upwards and downwards at specific applied potentials (-7 V ~ +7 V), respectively, and P represents the spin polarization.

[0060] The IV curves of chiral L-Cys-CoNi, chiral D-Cys-CoNi, and achiral DL-Cys-CoNi films are shown below. Figure 5 (a) Figure 5 (b) and Figure 5 As shown in (c). For chiral L-Cys-CoNi films ( Figure 5 In (a) of the figure, there is a significant difference in the average current under the two magnetization directions. Within the potential window of -7 V to 7 V, the current value under downward magnetization is significantly higher than that under upward magnetization, and the spin polarization can reach 88%. For chiral D-Cys-CoNi thin films ( Figure 5 In (b), this trend is completely opposite; the current value when magnetized upward is significantly higher than that when magnetized downward, with a spin polarization of 81%. In contrast, in the non-chiral DL-Cys-CoNi thin film, there is no significant difference in the current value corresponding to different magnetization directions. Figure 5(c) Magnetic conductive probe atomic force microscopy results show that strong spin-dependent charge transport exists in the chiral Cys-CoNi film, meaning that electrons are polarized when transported through the chiral bimetallic structure. This phenomenon can be attributed to the chiral-induced spin selectivity effect. The spin polarization of the chiral cobalt-nickel bimetallic electrocatalyst provided by this invention is significantly higher than that of most chiral monometals (less than 60%). The high spin polarization phenomenon in this invention is attributed to the high spin-orbit coupling of the cobalt-nickel bimetallic active center and the efficient chiral transfer effect of cysteine, which also indicates that chiral Cys-CoNi is an excellent electrocatalytic material for regulating the spin polarization process.

[0061] (5) To evaluate the OER activity of chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF, their electrocatalytic performance was studied using linear sweep voltammetry (LSV) under alkaline electrolyte conditions. Specifically, a three-electrode system and an electrochemical workstation were used to test the electrocatalytic oxygen evolution performance of the samples. The alkaline electrolyte was 1 M potassium hydroxide (KOH) solution (pH≈14). A graphite rod was selected as the counter electrode, a mercury / mercury oxide (Hg / HgO) electrode was selected as the reference electrode, and an NF with a planar size of 1 cm × 2 cm was selected as the working electrode. The 1 cm × 1 cm portion of the NF was loaded with chiral L-Cys-CoNi, chiral D-Cys-CoNi, and achiral DL-Cys-CoNi, respectively, and the remaining 1 cm × 1 cm portion was used to connect to the electrode clip. The electrocatalytic performance was measured at 5 mV·s⁻¹. -1 The rate was measured using LSV curves. Furthermore, the corresponding Tafel slopes of the samples were used to evaluate the OER reaction kinetics to gain a deeper understanding of the chiral enhanced oxygen evolution process. The Tafel slope was obtained by linear fitting based on the Tafel equation (E = A + B × log j), where B corresponds to the Tafel slope. Charge transfer resistance was studied by electrochemical impedance spectroscopy (EIS). Electrochemical impedance spectroscopy (EIS) was obtained with an AC amplitude of 10 mV in the frequency range of 100 mHz to 100 kHz. All potentials were converted to values ​​relative to the reversible hydrogen electrode (RHE) according to the Nernst equation, as follows: E RHE = E （测试时设定的电压） + E （参比电极电势） + 0.059×pH(2) The results are as follows Figure 6 As shown.

[0062] Figure 6In (a), LSV testing showed that chiral D-Cys-CoNi / NF and chiral L-Cys-CoNi / NF increased current density faster in the OER reaction and had significantly better activity than achiral DL-Cys-CoNi / NF.

[0063] Figure 6 (b) shows the effect at 10 mA·cm -2 50 mA·cm -2 100 mA·cm -2 Overpotentials at current densities: The overpotentials of chiral L-Cys-CoNi / NF at corresponding current densities were 125 mV, 240 mV, and 392 mV, respectively; those of chiral D-Cys-CoNi / NF were 125 mV, 244 mV, and 367 mV, respectively; and those of achiral DL-Cys-CoNi / NF were 299 mV, 416 mV, and 509 mV, respectively. The results show that the overpotentials of chiral L-Cys-CoNi / NF and chiral D-Cys-CoNi / NF are significantly lower than those of achiral DL-Cys-CoNi / NF. Furthermore, at an overpotential of 509 mV, the OER current densities for chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF were 136, 146, and 100 mA cm⁻¹, respectively. -2 The OER current density of chiral D-Cys-CoNi / NF was increased by 46% compared with that of non-chiral DL-Cys-CoNi / NF. These results indicate that the chiral structure has a significant enhancing effect on OER activity.

[0064] Figure 6 (c) shows that the Tafel slopes of chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF are 80.89 mV·dec. -1 100.28 mV·dec -1 and 166.16 mV·dec -1 Among them, the chiral L-Cys-CoNi / NF has the smallest Tafel slope, indicating that its OER reaction kinetics are the fastest and its charge transfer process is more efficient.

[0065] Figure 6As shown in (d), the charge transfer resistance of chiral L-Cys-CoNi / NF and chiral D-Cys-CoNi / NF is significantly lower than that of achiral DL-Cys-CoNi / NF, indicating that the interfacial electron transfer rate of chiral catalysts is faster. This is related to the electronic properties regulated by the chiral structure and the surface active sites, further demonstrating their excellent OER activity.

[0066] The results above indicate that chiral Cys-CoNi / NF exhibits a faster intermediate kinetic rate and a more favorable interfacial charge transfer process than achiral DL-Cys-CoNi / NF.

[0067] Comparative Example 1 This comparative example uses an electrodeposition method to prepare a catalytic electrode, including the following steps: 0.25 mmol Ni(NO3)2·6H2O, 0.75 mmol Co(NO3)2·6H2O, and 5 mmol L-Cys were added to a mixed solvent of 15 mL methanol and 35 mL ultrapure water, and the mixture was sonicated for 30 minutes to obtain a composite solution. This composite solution was then used as the electrolyte. A saturated calomel electrode (SCE, Hg2Cl2 / Hg) was used as the reference electrode, and a clean NF (1.0 cm × 2.0 cm planar dimension) was used as the counter electrode. Electrodeposition was performed on another NF (1.0 cm × 2.0 cm planar dimension, working electrode) for 5 minutes. The resulting NF with the electrocatalyst was then rinsed four times alternately with ultrapure water and ethanol, and then dried under vacuum at 50 °C for 6 h. The resulting catalytic electrode is designated as the electrodeposition method L-Cys-CoNi / NF.

[0068] Comparative Example 2 This comparative example uses a solvothermal method to prepare the catalytic electrode, including the following steps: The only difference from Example 1 is that "608 mg of L-Cys was dispersed in 10 mL of ultrapure water to obtain an L-Cys solution" was replaced with "1.02 g of L-tryptophan (L-Trp) was dispersed in 10 mL of methanol to obtain an L-Trp solution". The resulting catalytic electrode is called solvothermal L-Trp-CoNi / NF.

[0069] Comparative Example 3 This comparative example uses a solvothermal method to prepare the catalytic electrode, including the following steps: The only difference from Example 1 is that "608 mg of L-Cys was dispersed in 10 mL of ultrapure water to obtain an L-Cys solution" was replaced with "825 mg of L-phenylalanine (L-Pheny) was dispersed in 10 mL of methanol to obtain an L-Pheny solution". The resulting catalytic electrode is denoted as solvothermal L-Pheny-CoNi / NF.

[0070] Comparative Example 4 Tartaric acid (TA) is a strong acid and will decompose nickel foam during solvothermal processes, requiring the addition of a large amount of NaOH to adjust the pH value, making it unsuitable for this process. Therefore, this comparative example uses an electrodeposition method to prepare the catalytic electrode (denoted as electrodeposition L-TA-CoNi / NF), including the following steps: 0.25 mmol Ni(NO3)2·6H2O, 0.75 mmol Co(NO3)2·6H2O, and 5 mmol L-TA (L-type tartaric acid) were added to a mixed solvent of 15 mL methanol and 35 mL ultrapure water, and the mixture was sonicated for 30 minutes to obtain a composite solution. This composite solution was then used as the electrolyte. A saturated calomel electrode (SCE, Hg2Cl2 / Hg) was used as the reference electrode, and a clean NF (1.0 cm × 2.0 cm planar dimension) was used as the counter electrode. Electrodeposition was performed on another NF (1.0 cm × 2.0 cm planar dimension, working electrode) for 5 minutes. The resulting NF loaded with the electrocatalyst was then rinsed four times alternately with ultrapure water and ethanol, and then dried under vacuum at 50 °C for 6 h to obtain the electrodeposited L-TA-CoNi / NF.

[0071] Electrochemical OER testing of other chiral ligands bound to CoNi bimetals: LSV tests were performed on the solvothermal L-Cys-CoNi / NF, electrodeposition L-Cys-CoNi / NF, solvothermal L-Trp-CoNi / NF, solvothermal L-Pheny-CoNi / NF, and electrodeposition L-TA-CoNi / NF in Examples 1, 1, 2, 3, and 4 (methods described above). The results are as follows: Figure 7 As shown.

[0072] Depend on Figure 7 As shown in (a), the solvothermal L-Cys-CoNi / NF has the lowest LSV overpotential.

[0073] Depend on Figure 7 As shown in (b), at 10 mA·cm -2Overpotential at current density: The overpotential of L-Cys-CoNi / NF by solvothermal method is 125 mV, the overpotential of L-Cys-CoNi / NF by electrodeposition method is 193 mV, the overpotential of L-Trp-CoNi / NF by solvothermal method is 357 mV, the overpotential of L-Pheny-CoNi / NF by solvothermal method is 136 mV, and the overpotential of L-TA-CoNi / NF by electrodeposition method is 249 mV.

[0074] It is evident that the OER performance of the solvothermal L-Cys-CoNi / NF is superior to that of the electrodeposition L-Cys-CoNi / NF. Furthermore, the OER performance of the solvothermal L-Cys-CoNi / NF is also superior to that of the solvothermal L-Trp-CoNi / NF, solvothermal L-Pheny-CoNi / NF, and electrodeposition L-TA-CoNi / NF. These results demonstrate that, compared to the electrodeposition method, the solvothermal method (specifically the hydrothermal method) employed in this invention is simpler and can produce chiral catalytic electrodes with better OER activity, thus facilitating the large-scale production of chiral electrocatalysts or catalytic electrodes.

[0075] Compared to other chiral ligands, cysteine's efficient chiral transfer combined with the high spin orbital coupling of the chiral cobalt-nickel bimetallic active center significantly improves spin polarization efficiency, greatly suppresses the generation of byproduct H2O2, and enhances OER activity.

[0076] In summary, this invention provides a chiral cobalt-nickel bimetallic electrocatalyst with high spin polarization, a catalytic electrode, its preparation method, and its applications. First, a three-dimensional, flower-like chiral CoNi bimetallic electrocatalyst with good conductivity and interwoven stacking was synthesized using a solvothermal method. This accelerates interfacial electron conduction, exposes more active sites, and enhances OER activity. Second, chiral cysteine ​​was used as a chiral ligand to transfer chirality to the CoNi bimetallic catalyst. Chiral spin polarization suppressed the generation of singlet spin states, thereby hindering the formation of the byproduct H₂O₂ and promoting the formation of the target product O₂ in the triplet spin state. Furthermore, magnetic permeability probe atomic force microscopy confirmed that the chiral CoNi bimetallic electrocatalyst possesses high spin polarization current, with chiral L-Cys-CoNi achieving a spin polarization of 88% and chiral D-Cys-CoNi achieving 81%, overcoming the limitation of low spin polarization efficiency in existing chiral metal oxides. Compared to achiral DL-Cys-CoNi / NF, at a current density of 10 mA·cm -2At this time, the overpotential of both chiral L-Cys-CoNi / NF and chiral D-Cys-CoNi / NF decreased by 174 mV. At an overpotential of 509 mV, the OER current densities of chiral L-Cys-CoNi / NF, chiral D-Cys-CoNi / NF, and achiral DL-Cys-CoNi / NF were 136, 146, and 100 mA cm⁻¹, respectively. -2 The OER current density of chiral D-Cys-CoNi / NF is increased by 46% compared with that of achiral DL-Cys-CoNi. This invention provides a new strategy for enhancing OER activity in the field of electrocatalysis by means of chiral spin modulation.

[0077] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a chiral cobalt-nickel bimetallic electrocatalyst, characterized in that, Includes the following steps: A first mixture is provided, the first mixture comprising a solvent, a cobalt salt, a nickel salt, and cysteine, wherein the cysteine ​​is L-cysteine ​​or D-cysteine; The chiral cobalt-nickel bimetallic electrocatalyst is obtained by subjecting the first mixture to a solvothermal reaction.

2. The preparation method according to claim 1, characterized in that, The temperature of the solvothermal reaction is 100~200℃, and the time of the solvothermal reaction is 6~18 h.

3. The preparation method according to claim 2, characterized in that, The cobalt salt includes at least one of cobalt nitrate, cobalt chloride, cobalt sulfate, and cobalt phosphate, and the nickel salt includes at least one of nickel nitrate, nickel chloride, nickel sulfate, and nickel acetate.

4. The preparation method according to claim 1, characterized in that, The molar ratio of the cobalt salt, nickel salt and cysteine ​​is (1~8):(1~6):(5~21).

5. The preparation method according to claim 1, characterized in that, The solvent includes at least one of water, methanol, isopropanol, and ethanol.

6. A chiral cobalt-nickel bimetallic electrocatalyst, characterized in that, The chiral cobalt-nickel bimetallic electrocatalyst, prepared by any one of claims 1-5, exhibits a chiral induced spin selectivity effect.

7. A catalytic electrode, characterized in that, The catalytic electrode includes a conductive support and a catalyst supported on the conductive support, wherein the catalyst is the chiral cobalt-nickel bimetallic electrocatalyst as described in claim 6.

8. A method for preparing the catalytic electrode according to claim 7, characterized in that, Includes the following steps: A second mixture is provided, the second mixture comprising a solvent, a cobalt salt, a nickel salt, and cysteine, wherein the cysteine ​​is L-cysteine ​​or D-cysteine; A conductive support is placed in the second mixture, and then a solvothermal reaction is carried out to obtain the catalytic electrode.

9. The preparation method according to claim 8, characterized in that, The conductive carrier includes nickel foam, titanium foam, indium tin oxide conductive glass, fluorine-doped tin oxide conductive glass, and Ti3C2T. x At least one of carbon cloth.

10. The application of the chiral cobalt-nickel bimetallic electrocatalyst of claim 6 or the catalytic electrode of claim 7 in the catalytic oxygen evolution reaction.

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