Bimetal monatomic NiCo / NC-TA electrocatalyst and application thereof in electrocatalytic reaction

Abstract

The invention belongs to the field of electrocatalysts, and particularly relates to a bimetallic monatomic NiCo / NC-TA electrocatalyst and application of the bimetallic monatomic NiCo / NC-TA electrocatalyst in an electrocatalytic reaction. According to the electrocatalyst, Zn < 2 + > salt serves as main metal salt, Ni < 2 + > salt and Co < 2 + > salt serve as double-doped metal salt, and the main metal salt, the double-doped metal salt and 2-methylimidazole react to form an imidazole zeolite framework; and etching and carbonizing the imidazole zeolite skeleton to obtain the catalyst. According to the preparation method, the NiCo-nitrogen-carbon heteronuclear diatomic catalyst is constructed, and the electronic structure of Co atom sites is remarkably regulated and controlled by using introduced Ni metal atoms, so that the adsorption free energy of a reaction intermediate on the surface of the catalyst is optimized, and the electrocatalytic activity of the catalyst in an oxygen reduction reaction, a hydrogen evolution reaction and an oxygen evolution reaction is remarkably improved; the surface area of the catalyst is increased by etching, and more active sites are effectively exposed, so that the ORR, HER and OER processes are promoted.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalysts, specifically relating to a bimetallic single-atom NiCo / NC-TA electrocatalyst and its application in electrocatalytic reactions. Background Technology

[0002] Contemporary society has an increasing demand for various renewable energy devices, such as water electrolysis, zinc-air batteries (ZABS), and fuel cell systems. However, the slow kinetics of the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) severely impair the practical effectiveness of ZABS and water electrolysis. Materials based on noble metals (such as Pt and Ru) are now considered highly effective HER / ORR and OER catalysts, respectively. However, individual noble metal-based compounds only exhibit excellent catalytic efficacy for specific reactions and fail to simultaneously impart efficiency to OER, ORR, and HER processes. Furthermore, the high cost and scarcity of these noble metals also hinder the large-scale industrial development of sustainable energy technologies.

[0003] In recent years, single-atom catalysts (SACs) formed by anchoring isolated transition metals (such as iron and cobalt) onto a nitrogen-doped carbon matrix have been considered as one of the most promising electrocatalysts to replace noble metal (PGM) catalysts due to their abundant reserves, ultra-high atom utilization efficiency and excellent ORR activity.

[0004] While SACs have many advantages, their drawbacks are also undeniable: (1) Due to the single adsorption site, there is an unbreakable linear scaling relationship between the adsorption energies of different intermediates on SACs, which severely limits the activity of the catalyst. (2) The metal loading is low, and the metal atoms of SACs tend to aggregate into nanoparticles during pyrolysis. This problem needs to be solved by reducing the metal loading, which severely reduces the overall activity of the catalyst. (3) Although SACs perform exceptionally well in simple reactions, due to the single active site, they are difficult to handle complex multi-electron processes. Summary of the Invention

[0005] The purpose of this invention is to provide a bimetallic single-atom NiCo / NC-TA electrocatalyst to address the problem that the catalytic activity of existing catalysts for ORR, HER and OER needs to be improved.

[0006] A second objective of this invention is to provide an application of the aforementioned bimetallic single-atom NiCo / NC-TA electrocatalyst to address the problems described above.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A bimetallic single-atom NiCo / NC-TA electrocatalyst, with Zn 2+ Ni is a primary metal salt. 2+ Salt and Co 2+ The salt is a dual-doped metal salt. The main metal salt, the dual-doped metal salt and 2-methylimidazolium react to form an imidazolium zeolite framework; then the imidazolium zeolite framework is etched and carbonized to obtain the final product.

[0009] This invention is an improved invention. By constructing a NiCo-nitrogen-carbon heteronuclear diatomic catalyst, the electronic structure of the Co atomic sites is significantly modulated by the introduced Ni metal atoms, optimizing the adsorption free energy of the reaction intermediates on the catalyst surface, and significantly improving its electrocatalytic activity in the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER). Etching is used to increase the catalyst surface area, effectively exposing more active sites, thereby promoting the ORR, HER, and OER processes.

[0010] Preferably, the molar ratio of Ni to Co in the dual-doped metal salt is 1:1, and the ratio of the molar amount of Zn to the sum of the molar amounts of Ni and Co in the main metal salt is 25:1-35:1.

[0011] More preferably, Zn 2+ The molar ratio of Zn to 2-methylimidazole in the salt is 1:(8-10).

[0012] Preferably, the reaction is carried out at room temperature for 12-24 hours; Zn 2+ Salt, Ni 2+ Salt and Co 2+ All salts are nitrates, and the solvent used in the reaction is methanol.

[0013] Etching the imidazole zeolite framework can generate more defects and remove unstable metal active sites. Preferably, the etching is carried out in a methanol solution of tannic acid, wherein the concentration of tannic acid is 2-5 g / L. More preferably, the imidazole zeolite framework is aged in the methanol solution of tannic acid for 5-15 min to complete the etching.

[0014] Preferably, the carbonization is carried out under a protective atmosphere at a temperature of 880-950℃; the carbonization time is 2-4 hours. More preferably, the carbonization time is 920-950℃; the carbonization time is 3-4 hours; and the ratio of the molar amount of Zn to the sum of the molar amounts of Ni and Co in the main metal salt is 25:1-29:1.

[0015] The above-mentioned bimetallic single-atom NiCo / NC-TA electrocatalyst is used in electrocatalytic reactions, wherein the electrocatalytic reactions are selected from one or more of the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER).

[0016] Density functional theory (DFT) calculations show that this invention uses Ni-N4 sites as electronic modulators to effectively regulate the electronic distribution environment of Co-N4 active sites, achieving precise control of diatomic sites. This enables synergistic promotion of electrocatalytic ORR, HER, and OER, and its electrocatalytic activity and stability are superior to commercial Pt / C and other reference samples.

[0017] Preferably, the application includes using the bimetallic single-atom NiCo / NC-TA electrocatalyst as a cathode catalyst in a metal-air battery. Attached Figure Description

[0018] Figure 1 This document describes the synthesis and characterization of the NiCo / NC-TA electrocatalyst in Example 1 of the present invention. (a) is a schematic diagram of the NiCo / NC-TA electrocatalyst synthesis; (b), (c), and (d) are SEM, TEM, and AC-HAADF-STEM images of the NiCo / NC-TA electrocatalyst, respectively; (e) shows the intensity distribution corresponding to regions A1, A2, and A3 in image (d); and (f) to (j) are HAADF views of the catalyst and schematic diagrams of Co, Ni, N, and C elements.

[0019] Figure 2 The diagram shows the structural characterization of the electrocatalysts of this invention; (a) Raman spectra of NiCo / NC-TA, NiCo / NC, Co / NC-TA, and Ni / NC-TA; (b) nitrogen adsorption-desorption isotherms and corresponding pore size distributions of NiCo / NC-TA, NiCo / NC, Co / NC-TA, and Ni / NC-TA measured at 77 K; (c) contact angles of NiCo / NC-TA and NiCo / NC; (d) high-resolution C1s XPS spectra of NiCo / NC-TA, NiCo / NC, Co / NC-TA, and Ni / NC-TA electrocatalysts; and (e) high-resolution N1s XPS spectra; (f) XPS spectrum of Co 2p; (g) XANES spectrum of Co K-edge; and (h) XANES spectrum of Ni K-edge; (i) k-axis of Co and (j) Ni in R space. 3 Weighted FT-EXAFS spectrum; (k)WT contour plot;

[0020] Figure 3The electrocatalytic performance of the electrocatalysts of this invention is characterized as follows: (a) LSV curves of NiCo / NC-TA, NiCo / NC, Co / NC-TA, and Ni / NC-TA electrocatalysts in oxygen-saturated 0.1M KOH solution; (b) Tafel plots of the catalysts obtained from the corresponding LSV data; (c) Ci of the NiCo / NC-TA, NiCo / NC, Co / NC-TA, and Ni / NC-TA electrocatalysts. dl (d) IT curves of NiCo / NC-TA and Pt / C-20%; (e) IT curves of NiCo / NC-TA and Pt / C-20% after the addition of methanol; (f) LSV curves of NiCo / NC-TA and Pt / C-20% before and after ADT; (g) LSV curve of HER in 0.5M H2SO4 electrolyte; (h) LSV curve of HER in 1M KOH electrolyte; (i) LSV curve of OER;

[0021] Figure 4 The in-situ tests and theoretical calculations of this invention include: (a) the in-situ Raman spectrum of the NiCo / NC-TA electrocatalyst in 0.1M KOH; (b) the charge density difference diagram of NiCo / NC-TA; (c) the charge density difference diagram of Co / NC-TA (yellow represents nickel atoms, green represents cobalt atoms); (d) the Gibbs free energy step diagram of the oxygen reduction reaction (ORR) at 1.23V; (e, f) the hydrogen evolution reaction (HER) at 0V; and (g) the Gibbs free energy step diagram of the oxygen evolution reaction (OER) at 1.23V; and (h) the projected density of states (PDOS) diagram.

[0022] Figure 5 The metal-air battery tests of the present invention include: (a) the discharge polarization curve and corresponding power density curve of a primary zinc-air battery with NiCo / NC-TA and Pt / C-20%+RuO2; (b) the open-circuit potential of the primary zinc-air battery with NiCo / NC-TA and Pt / C-20%+RuO2; and (c) the constant-current discharge curve of the primary zinc-air battery with NiCo / NC-TA and Pt / C-20%+RuO2 (voltage range 0.2-1.4V, current density 2-50mA cm⁻¹). -2 (d) 10mA cm -2 (e) Specific capacity curves of primary zinc-air batteries with NiCo / NC-TA and Pt / C-20%+RuO2; (b) Discharge voltage stability diagram of primary zinc-air batteries with NiCo / NC-TA and Pt / C-20%+RuO2. Detailed Implementation

[0023] (I) Description of preferred embodiments of bimetallic single-atom NiCo / NC-TA electrocatalysts

[0024] Heteronuclear diatomic catalysts (HDACs) retain the advantages of single-atom catalysts (SACs) while possessing a selectively tunable coordination environment. Their electrochemical performance is closely related to their coordination environment and the electronic interactions with the support. The coordination environment of a heteronuclear diatomic catalyst includes the coordinating atoms, their number, and structure, which are crucial for altering the fundamental characteristics of the diatomic active sites. Changing the coordination environment of a diatomic catalyst can fine-tune the electronic properties of the active center, thereby significantly impacting the catalyst's electrocatalytic efficiency.

[0025] Developing highly active heteronuclear diatomic catalysts still faces many challenges, such as the stability of active centers, the formation of low-activity sites, and low utilization of active sites. This invention utilizes Zn... 2+ Ni 2+ Co 2+ It forms an imidazole zeolite framework with 2-methylimidazolium, and then undergoes etching and carbonization to construct a transition metal-nitrogen-carbon heteronuclear diatomic catalyst with optimized electronic structure and enhanced function to synergistically promote electrocatalytic ORR, HER and OER.

[0026] The NiCo / NC-TA catalyst exhibits significantly enhanced catalytic activity for ORR, HER, and OER, attributed to the proximity atom effect of adjacent Ni-N sites. Density functional theory (DFT) calculations reveal that the adjacent Ni-N lattice sites act as modulators, effectively regulating the electronic localization of the sole active Co-N lattice site. This leads to weakened OH adsorption on Co-N and enhanced H adsorption, thereby promoting ORR, HER, and OER processes. Furthermore, atomic-level vacancy regulation influences the chemical environment and electronic structure of the active metal center, optimizing oxygen intermediate adsorption and improving ORR, HER, and OER performance. The NiCo / NC-TA catalyst with carbon vacancies outperforms commercial Pt / C and other reference samples in terms of ORR activity and stability.

[0027] The imidazole zeolite framework is made using Zn 2+ Ni 2+ Co 2+ It reacts with 2-methylimidazole to form [ZIF]. Methanol can be used as the solvent. 50–60 mL of methanol is needed for every 0.0029 mol of zinc nitrate. First, zinc nitrate, nickel nitrate, and cobalt nitrate are dissolved in methanol (solution A), then mixed with a methanol solution of 2-methylimidazole (solution B). Solution A is added dropwise to solution B, and the mixture is stirred at room temperature for at least 24 hours to obtain the imidazole zeolite framework NiCo-ZIF.

[0028] Etching was performed in a methanol solution of tannic acid. The concentration of tannic acid was controlled at 5 g / L. During etching, the sample was aged in the methanol solution of tannic acid for 10 min to obtain the etched imidazole zeolite framework NiCo-ZIF-TA.

[0029] Carbonization was carried out by calcination at 920℃ for 3 hours. Calcination was conducted under a protective atmosphere (e.g., N2 atmosphere), with the temperature rising to 920℃ at a rate of 2–5℃ / min. After natural cooling to room temperature, the target sample NiCo / NC-TA was obtained.

[0030] The preferred embodiments of the bimetallic single-atom NiCo / NC-TA electrocatalyst are illustrated below with specific examples. All the chemicals involved are commercially available and have not undergone further purification. The reagents used in the experiments were: Zn(NO3)2·6H2O (AR) from Xihua, Co(NO3)2·6H2O (AR) from Comio, Ni(NO3)2·6H2O (AR) from Comio, and tannic acid (ACS) from Aladdin. Ruthenium oxide and 2-methylimidazole (AR) were from Aladdin. Pt / C (20 wt%) was purchased from Alfa Aesar, and Nafion solution (5 wt%) was purchased from DuPont. Methanol and ethanol were from Tianjin Fuyu Reagent.

[0031] Example 1

[0032] The bimetallic single-atom NiCo / NC-TA electrocatalyst of this embodiment was prepared using the following steps: 0.87 g Zn(NO3)2·6H2O (297.52, 0.0029 mol); 0.0145 g Co(NO3)2·6H2O (290.83, 0.00005 mol); and 0.0145 g Ni(NO3)2·6H2O (0.00005 mol) were dissolved together in 30 mL of methanol, and the resulting solution was designated as solution A. 1.97 g 2-methylimidazole (82.1, 0.024 mol) was added to 20 mL of methanol, and the resulting solution was designated as solution B. Solution A was added dropwise to solution B, and the mixture was stirred at room temperature for 24 h. After the reaction, the mixture was centrifuged and vacuum dried to obtain NiCo-ZIF.

[0033] 250 mg of tannic acid was dissolved in 50 mL of methanol to form a 5 g / L tannic acid-methanol mixture. 0.1 g of NiCo-ZIF was added to the tannic acid-methanol solution, stirred and mixed, allowed to stand for 10 min, and then centrifuged to obtain NiCo-ZIF-TA.

[0034] NiCo-ZIF-TA was placed in a tube furnace and heated to 920℃ at a heating rate of 2℃ / min under a N2 atmosphere. It was calcined for 3 hours and then naturally cooled to room temperature to obtain the target sample NiCo / NC-TA.

[0035] Based on this embodiment, while maintaining the molar ratio of Ni to Co at 1:1, the ratio of the molar amount of Zn to the sum of the molar amounts of Ni and Co can be 25:1 or 35:1, which can achieve an effect that is basically equivalent to the 29:1 ratio in the above embodiment.

[0036] Furthermore, the reaction time can be adjusted to 12h or 16h. The concentration of the tannic acid methanol solution can be 2g / L or 4g / L, and the etching time can be 5min, 12min, or 15min. The carbonization temperature can be 880℃ or 950℃, and the carbonization time can be 2h or 4h, all of which achieve essentially the same effect as the above-mentioned embodiments.

[0037] Comparative Example 1: Preparation of single-atom Ni-N catalyst Ni / NC-TA

[0038] The electrocatalyst of Comparative Example 1 is labeled Ni / NC-TA. The only difference from Example 1 is that Co(NO3)2·6H2O is not added during the preparation of NiCo-ZIF, and the amount of Ni(NO3)2·6H2O added is 0.0001 mol.

[0039] Comparative Example 2: Preparation of Co / NC-TA single-atom Co-N catalyst

[0040] The electrocatalyst of Comparative Example 2 is labeled Co / NC-TA. The only difference from Example 1 is that Ni(NO3)2·6H2O is not added during the preparation of NiCo-ZIF, and the amount of Co(NO3)2·6H2O added is 0.0001 mol.

[0041] Comparative Example: Preparation of 3NiCo / NC

[0042] The electrocatalyst of Comparative Example 3 is labeled as NiCo / NC. Compared with Example 1, the only difference is that no etching process is performed. The obtained NiCo-ZIF is directly placed in a tube furnace and heated to 920°C at a heating rate of 2°C / min under N2 atmosphere. It is calcined for 3 hours and then naturally cooled to room temperature to obtain the target sample NiCo / NC.

[0043] Morphological characteristics

[0044] The morphology and elemental distribution of the prepared samples were observed using a field emission scanning electron microscope (SEM, Hitachi-SU8600, Japan), a transmission electron microscope (TEM, JEM-2100F, Japan), and an energy dispersive spectrometer (Oxford UltimMax40, Japan).

[0045] Synthesis strategies for bimetallic single-atom NiCo / NC-TA electrocatalysts, such as Figure 1 As shown in figure a. Scanning electron microscopy (SEM) observations show that the NiCo / NC-TA catalyst exhibits a dodecahedral shape with a hollow-like structure, and the particle size is approximately 50 nm. Figure 1 (b) While the unetched NiCo / NC catalyst retains its dodecahedral structure, it does not form a hollow structure, and its particle size is approximately 100 nm. The etched single-atom Co / NC-TA catalyst has a particle size of approximately 120 nm, and its structure is similar to that of the NiCo / NC-TA catalyst. The morphology and size of the Ni / NC-TA catalyst are consistent with those of the NiCo / NC-TA catalyst.

[0046] The results of transmission electron microscopy (TEM) observations of the NiCo / NC-TA catalyst are consistent with those of SEM. Figure 1 c). Numerous uniformly distributed bright spots were observed under high-angle annular dark-field scanning electron microscopy (AC-HAADF-STEM), indicating a uniform distribution of metal atoms within the catalyst. Paired bright spots (marked with orange circles) in the image reveal the presence of dual single atoms. Figure 1 d). In a randomly selected region, the distance between atomic pairs was determined to be approximately [missing information] through intensity distribution analysis. The uniform dispersion of the two atomic sites in the NiCo / NC-TA catalyst was confirmed. Figure 1 e). AC-HAADF-STEM imaging of the NiCo / NC-TA catalyst further demonstrates that Co, Ni, N, and C elements are uniformly distributed within the catalyst. Figure 1 fj).

[0047] Structural Analysis

[0048] To further reveal the structural characteristics of the catalyst, this study employed X-ray powder diffraction (XRD), Raman spectroscopy and N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, and synchrotron radiation for in-depth characterization.

[0049] The crystal structure of the materials was determined using X-ray diffraction (XRD, D8 ADVANCE, CuKα radiation) in the range of 5°–80°. XRD patterns showed no significant metal diffraction peaks in any of the samples, thus ruling out the formation of metal particles and clusters.

[0050] Raman measurements were performed on a Lab RAMHR Evolution spectrometer to detect the spectral characteristics and chemical bonds of the samples. The Raman spectra (...) Figure 2 In (a), each catalyst clearly exhibits the G-band (1585.2 cm⁻¹). -1 ) and D band (1339.2cm) -1 ), respectively corresponding to sp 2 Hybridized carbon atoms and carbon lattice defects. I in NiCo / NC-TA D / I G The ratio (1.05) is slightly higher than that of NiCo / NC. D / I G The ratio (1.02) indicates that the etching effect of tannic acid contributes to increasing carbon defects. Meanwhile, the Ig of NiCo / NC-TA... D / I G The ratio is also higher than that of Co / NC-TA (1.01) and Ni / NC-TA (1.03), indicating that NiCo / NC-TA has a higher degree of defect, which is beneficial to provide more active sites and promote the electrochemical reaction.

[0051] Nitrogen adsorption / desorption data were recorded at liquid nitrogen temperature (77 K) using a BELSORP MaxII apparatus. Before measurement, the sample was degassed under vacuum at 120 °C for 12 h. Specific surface area was calculated using the Brunauer-Emmett-Teller (BET) equation, and total pore volume was calculated from the amount adsorbed at a relative pressure (P / P0) of 0.99. Adsorption-desorption isotherms ( Figure 2 b) indicates that the Brunauer-Emmett-Teller (BET) specific surface area of ​​NiCo / NC-TA (550 cm² g) -1 Significantly higher than NiCo / NC (53cm² g) -1 ) and Co / NC-TA (404cm2 g) -1 This is attributed to the etching effect of tannic acid and the introduction of Ni metal, which increases the degree of defects. However, its specific surface area is slightly lower than that of Ni / NC-TA (558 cm² g). -1This is likely due to the low Ni content in the single-atom Ni samples. The pore size distribution curves show that, compared to the NiCo / NC sample, NiCo / NC-TA, Co / NC-TA, and Ni / NC-TA are all mesoporous materials, with NiCo / NC-TA exhibiting a larger mesopore volume. This phenomenon can be attributed to the etching effect of tannic acid and the interaction between Ni and Co ions during synthesis, which may lead to lattice distortion and defect formation, thereby promoting the formation of complex and diverse pore structures. The abundant mesoporous structure of NiCo / NC-TA facilitates the transport of reaction intermediates, thus promoting the reaction process.

[0052] To investigate the effect of etching techniques on catalyst properties, contact angle measurements were performed on NiCo / NC-TA and NiCo / NC catalysts. Hydrophilicity was assessed using contact angle measurements. Figure 2 c) shows that NiCo / NC-TA exhibits exceptionally good wettability (26°, compared to 79° for NiCo / NC), which is attributed to the surface oxygen-containing groups introduced during the etching process. This hydrophilicity promotes electrolyte penetration and ensures full utilization of subsurface active sites.

[0053] X-ray photoelectron spectroscopy (XPS) was used to measure the electron binding energy of the sample surface on an Ultra DLDX X-ray electron spectrometer. The surface chemical state of the catalyst was further analyzed using X-ray photoelectron spectroscopy (XPS). High-resolution spectral deconvolution was performed on the C1s XPS peaks of NiCo / NC-TA, NiCo / NC, Ni / NC-TA, and Co / NC-TA catalysts, yielding four peaks (…). Figure 2 d), respectively sp 2 Carbon (284.8 eV), sp 3 Carbon (285.5 eV), CO (286.6 eV), and C=O (288.8 eV). Carbon materials typically contain two types of carbon atoms: basal-plane and sp-plane. 2 carbon atoms and defects sp 3 Carbon atom, defect level by sp 3 The content determines the value. The sp2 / sp3 ratio of NiCo / NC-TA (5.73) is higher than that of Ni / NC-TA (3.69), NiCo / NC (3.56) and Co / NC-TA (2.58), indicating that NiCo / NC-TA has a higher defect content, which is consistent with the Raman spectroscopy results.

[0054] N1s XPS spectrum ( Figure 2e) revealed four distinct peaks: pyridine-N (398.4 eV), metal-N (399.8 eV), pyrrole-N (400.7 eV), and graphite-N (401.3 eV), indicating coordination between Ni and Co atoms and N. Comparing the peaks of different nitrogen species in different catalysts, the NiCo / NC-TA catalyst showed the highest metal-N content, followed by Co / NC-TA, NiCo / NC, and Ni / NC-TA. This matches the metal content detected by ICP. Therefore, it can be inferred that the metal-N bonding is beneficial to improving electrochemical performance. Due to the low Ni content in the catalyst, the Ni 2p peak was not detected in the XPS spectrum.

[0055] The changes in the binding energy of Co in single-atom and diatomic catalysts were observed by peak fractionation. Compared to Co / NC-TA, the 2p binding energy of Co in NiCo / NC-TA showed a positive shift of approximately 0.4 eV, indicating that the introduction of Ni led to a higher oxidation state of Co. This may be attributed to the electron-gathering effect of Ni. Figure 2 f).

[0056] X-ray absorption fine structure (XAFS) was used to measure and analyze the electronic configuration and coordination structure of Co and Ni at the atomic level. Co K-edge X-ray absorption near-edge structure (XANES) revealed the difference in valence states between NiCo / NC-TA and the comparative samples Co / NC-TA, Co foil, CoO, and Co3O4. The first derivative of Co K-edge XANES further revealed the exact valence state of Co. It can be seen that the absorption threshold of NiCo / NC-TA lies between CoO and Co3O4 on the linear fitting curve, indicating that the oxidation state of Co in NiCo / NC-TA is between +2 and +3, and higher than that of Co in Co / NC-TA. This is likely due to the electron-gaining effect of Ni atoms in NiCo / NC-TA, leading to an increase in the electron density around Co atoms. Figure 2 g). The k-side of nickel in the NiCo / NC-TA catalyst is located between the nickel foil and NiO, suggesting that the oxidation state of nickel is between 0 and +2. Figure 2 h). Co Fourier Transform (FT) from NiCo / NC-TA 3 Weighted EXAFS curve ( Figure 2 i) It can be seen that only in R space are observed A peak at this location can be attributed to Co-N coordination, and no Co-Co coordination peak was observed, indicating that the catalyst is a single atom. For the NiCo / NC-TA nickel FT-EXAFS curve, there is a main peak, which is attributed to... The Ni-N coordination at this location indicates that nickel atoms exist in an atomically dispersed state, without forming nickel nanoparticles or clusters. Figure 2 j). The above coordination indicates the existence of metal-nitrogen interactions, which can stabilize single atoms in the system and promote its electrocatalytic activity and stability.

[0057] Wavelet transform (WT) was used to confirm that Ni and Co exist in single-atom form. For example... Figure 2 As shown in k, the Ni-N coordination of NiCo / NC-TA can... It was observed that, compared to nickel foil and NiO, Co-N coordination can... It was observed that, compared to cobalt foil, CoO, and Co3O4, isolated Ni-N4 and Co-N4 structural units coexist in the NiCo / NC-TA catalyst. All results indicate that isolated Ni-N4 and Co-N4 structural units exist simultaneously in the NiCo / NC-TA catalyst.

[0058] (II) Preferred Implementation Methods for the Application of Bimetallic Single-Atom NiCo / NC-TA Electrocatalysts in Electrocatalytic Reactions

[0059] Based on the structural characteristics of the bimetallic single-atom NiCo / NC-TA electrocatalysts, they exhibit better catalytic performance in oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER).

[0060] Example 2

[0061] The application of the bimetallic single-atom NiCo / NC-TA electrocatalyst in electrocatalytic reactions in this embodiment involves coating the aforementioned NiCo / NC-TA electrocatalyst onto the electrode to promote the ORR, OER, and HER processes. Specific details are as follows:

[0062] 2.1 ORR Test

[0063] ORR testing was performed on a CHI760E electrochemical workstation. A platinum wire electrode, a 3mm glassy carbon electrode (GCE), and an Ag / AgCl electrode were used as the counter, working, and reference electrodes, respectively. The electrochemical test slurry was prepared by adding 4 mg of sample to a mixture of 950 μL (1:1 volume ratio of deionized water to anhydrous ethanol) and 50 μL of 5 wt% Nafion solution. 8 μL of the slurry was evenly dropped onto both the disc (4 mm diameter) and ring (4 mm diameter) electrodes. The sample loading was 255 μg / cm³. -2Allow it to air dry naturally. The electrolyte is a 0.1 mol L⁻¹ KOH aqueous solution. To achieve O₂ saturation, continuous oxygenation is required before the test. Cyclic voltammetry (CV) is performed in a 0.1 M KOH solution saturated with N₂ and O₂ at a scan rate of 50 mV / s. -1 Linear sweep voltammetry (LSV) experiments were conducted in an O2-saturated 0.1M KOH solution at a rotation speed of 1600 rpm and a scan rate of 10 mV / s. -1 The double-layer capacitance (C0) in the non-Radial region was determined by cyclic voltammetry. dl The electrochemically active specific surface area (ECSA) of NiCo / NC-TA and control samples at different scan rates can be estimated. Long-term durability testing was performed using chronoamperometry for 10 hours. Methanol tolerance was assessed using the chronoamperometric response after adding 2.8 mL of methanol (3M) at 120 seconds. (KL) equation analysis of transferred electrons:

[0064]

[0065] In the formula, J represents the measured current density, the limiting current density jL is the current density corresponding to a potential of 0.4V (vs. RHE), ω is the angular velocity of the electrode, k is the electron transfer rate constant, n is the number of transferred electrons, and F is the Faraday constant. -1 C0 is the volume concentration of oxygen in a 0.1 MkOH solution (1.26 x 10⁻⁶). -6 mol cm -3 D0 is the diffusion coefficient of oxygen in the electrolyte (1.93 x 10⁻⁶). -5 cm2 s -l ), where v is the kinetic viscosity (0.01 cm⁻¹). 2 s -1 ).

[0066] In the ORR reaction, the half-wave potential E is defined as follows: under the condition that the rotating disk electrode (RDE) rotates at 1600 rpm, when j reaches j L The potential corresponding to half of the value. The current signal of the intermediate product can also be collected via the ring electrode to calculate the number of electrons transferred during the oxygen reduction process. A potential is applied to the Pt ring to collect the H2O2 produced during the oxygen reduction reaction to generate a current signal. The hydrogen peroxide yield H2O2 (%) and the number of transferred electrons (n) during the ORR process are obtained from the following formulas:

[0067] n = 4 * I disk / (I disk +I ring / N)

[0068] H2O2 (%) = 200 * I ring / (I disk *N+I ring )

[0069] Among them, I ring with I disk The currents measured are for the platinum ring section and the glass carbon disk section, respectively, with N being 0.424.

[0070] Measurement of electrochemical active area (ECSA): Cyclic voltammetry (CV) tests were performed at different scan rates within the non-Radichtal potential range of 1.00–1.10 V vs RHE to obtain the double-layer capacitance (Cdl) value. ECSA was calculated using the following formula:

[0071]

[0072] Where Cs is the specific capacitance of the complete electric double layer (0.04 mF cm⁻¹). -2 ).

[0073] In the oxygen reduction electrochemical testing of the prepared electrocatalyst slurry using rotating disk electrode and rotating ring electrode techniques, significant results were obtained in an oxygen-saturated 0.1M KOH solution. Based on the cyclic voltammetry (CV) curves... Figure 3 a) and linear sweep voltammetry (LSV) measurement ( Figure 3 b) It was found that the NiCo / NC-TA electrocatalyst exhibits excellent half-wave potential (E) in alkaline media. 1 / 2 The maximum band gap (V) of NiCo / NC-TA (0.821 V), Ni / NC-TA (0.722 V), and the unetched bimetallic electrocatalyst NiCo / NC-TA (0.809 V) was 0.882 V, significantly better than that of the single metal catalysts Co / NC-TA (0.821 V), Ni / NC-TA (0.722 V), and the unetched bimetallic electrocatalyst NiCo / NC-TA (0.809 V). In alkaline electrolyte, the maximum band gap of NiCo / NC-TA and Co / NC-TA at E1 / 2 was 61 mV, revealing the significant promoting effect of adjacent Ni-N bonds on improving the oxygen reduction kinetics of Co-N.

[0074] Further calculations of Jk(0.8V) and Jk(0.85V) for each catalyst were performed. Using the Koutecky-Levich (KL) equation, the kinetic current density (jk) at a given potential was obtained. For NiCo / NC-TA, jk at 0.8V and 0.85V vs. RHE was 37.06 mA cm⁻¹. -2 With 12.64mA cm -2 The results showed that NiCo / NC-TA significantly outperformed the other comparative samples, demonstrating that NiCo / NC-TA exhibits superior ORR reaction kinetics.

[0075] The Tafel slope was calculated based on the LSV curve to evaluate the ORR reaction kinetics. The Tafel slope for NiCo / NC-TA was 41.71 mV dec. -1 The value was the lowest among the catalysts studied, indicating that it possesses excellent oxygen reduction kinetics. Figure 3 c). To further evaluate the usable active surface area of ​​the obtained catalyst, electrochemical CV curve analysis was performed at different scan rates to obtain the double-layer capacitance (Cf) in the non-Radida region. dl ()( Figure 3 d) Evaluating the electrochemical surface area (ECSA) of the catalyst, NiCo / NC-TA exhibited a larger double-layer capacitance (22.21 mF cm⁻¹). -2 ) and ECSA (555.25m 2 g -1 The NiCo / NC-TA sample exhibits the highest number of exposed active sites, far exceeding other electrocatalytic samples. This is related to the large specific surface area of ​​NiCo / NC-TA. Furthermore, the intrinsic activity of active sites in NiCo / NC-TA and other comparative samples was evaluated using turnover frequency (TOF), and the TOF value of NiCo / NC-TA was superior to that of the other comparative samples.

[0076] After evaluating the intrinsic catalytic activity of the catalyst, in order to understand the selectivity of the obtained catalyst in ORR, according to The electron transfer number for NiCo / NC-TA was calculated to be 3.92 using the KL equation, confirming the 4-electron transfer mechanism of the oxygen reduction reaction (ORR). For the other comparative samples, we performed LSV curve tests at different rotational speeds and calculated using the KL equation. The electron transfer numbers for NiCo / NC, Co / NC-TA, and Pt / C-20% samples were close to 4, while the electron transfer number for Ni / NC-TA was close to 2.

[0077] The obtained catalyst and commercial Pt / C were further evaluated using a rotating ring-disk electrode (RRDE). The test conditions for RRDE were similar to those for RDE, and the data obtained from RRDE were used to calculate the H2O2 yield and the number of electrons transferred (n) during ORR. The results showed that within the test voltage range, the H2O2 generated by NiCo / NC-TA catalysis was negligible, and the number of electrons transferred (n) was close to the theoretical value of 4, which is similar to the performance of commercial Pt / C catalysts, indicating that NiCo / NC-TA is comparable to advanced commercial Pt / C.

[0078] The methanol tolerance of NiCo / NC-TA and Pt / C was determined by adding 3 mL of methanol to 0.1 M KOH electrolyte, and the results are as follows: Figure 3As shown in Figure e, the current density of the NiCo / NC-TA catalyst only experienced a slight disturbance upon the addition of methanol throughout the test, remaining essentially stable overall. In contrast, the current density of the Pt / C catalyst decreased significantly after the addition of 3 mL of methanol, indicating that the NiCo / NC-TA catalyst exhibits strong tolerance to methanol. This broadens the application capabilities of NiCo / NC-TA in other energy storage devices, such as fuel cells.

[0079] The long-term stability of NiCo / NC-TA was tested using the chronoamperometry method. Stability tests showed that the NiCo / NC-TA catalyst exhibited only a 2% current decay after 20 hours, while the commercial Pt / C catalyst maintained only 81% of its initial current. Figure 3 f) indicates that the NiCo / NC-TA catalyst has more reliable stability.

[0080] The ORR stability of NiCo / NC-TA was further evaluated using accelerated durability testing (ADT). After 10,000 long-term cycles, the E0 of NiCo / NC-TA was [value missing]. 1 / 2 With j L No significant degradation occurred, indicating that the NiCo / NC-TA catalyst exhibits excellent durability. In contrast, the Pt / C-20% catalyst showed a half-wave potential change of 0.06 V and a limiting current density reduction of 0.6 mA / cm². -2 The changes are significant.

[0081] 2.2 OER and HER tests

[0082] OER and HER tests were performed on a CHI760E electrochemical workstation. The electrolyte was 1 mol / L. -1 KOH and 0.5 mL -1 For H2SO4 aqueous solution, the potential relative to the Ag / AgCl electrode used in this work was converted to the potential relative to the reversible hydrogen electrode (RHE) according to E(vs.RHE)=E(vs.Ag / AgCl)+0.059pH, and the overpotentials (η) of HER and OER were calculated based on η=E(vs.RHE)-0.198V and η=E(vs.RHE)-1.23V, respectively.

[0083] To evaluate the electrocatalytic activities of HER and OER, at room temperature, at 50 mV s -1 The scan rate was measured using a cathode linear scan voltammetry (LSV) curve, and the electrochemical impedance spectroscopy (EIS) spectrum had frequencies from 10... 2 At 10Hz, the amplitude is 10mV.

[0084] All density functional theory calculations were performed using the Vienna ab initio simulation package (VASP). The Perdew-Burke-Ernzerhof (PBE) functional was employed to handle exchange-correlation interactions. Structural relaxation was performed using a plane-wave basis set with a kinetic energy cutoff of 400 eV and an energy convergence criterion of 10. -4 eV, force convergence criterion is (2×2×1) Monkhorst-Pack k-point sampling was employed. A sufficiently large vacuum gap was used to prevent interactions between adjacent periodic structures. The calculations of H2 and H2O are performed in The calculations were performed within a box, using only the gamma point. Free energy diagrams for OER, ORR, and HER were calculated relative to the calculated hydrogen electrode. The free energies for the gas phase and adsorbed species can be obtained using the following equations:

[0085] ΔG=ΔE + ΔZPE -TΔS (9)

[0086] Where ΔE represents the difference in reaction energy, ΔZPE represents the zero-point vibrational energy, T represents the temperature (set to 298.15 K), and ΔS represents the change in entropy.

[0087] In addition to exhibiting excellent performance in oxygen reduction electrochemistry, NiCo / NC-TA also demonstrates outstanding hydrogen evolution reaction (HER) activity in 0.5 M H₂SO₄ and 1 M KOH solutions, reaching 10 mA cm⁻¹ under both acidic and alkaline conditions. -2 The required overpotentials for the current densities are 237.7 mV ( Figure 3 g) and 92mV ( Figure 3 The oxygen evolution reaction (OER) catalytic performance of the catalyst was tested in a three-electrode setup using 1.0 M KOH electrolyte. The NiCo / NC-TA catalyst exhibited higher OER catalytic activity, requiring only an overpotential of 244 mV to reach 10 mA cm⁻¹. -2 The current density is superior to that of Ni / NC-TA, Co / NC-TA, NiCo / NC, and RuO2 ( Figure 3 i). In summary, the NiCo / NC-TA electrocatalyst not only exhibits outstanding half-wave potential and excellent stability in ORR, but also demonstrates superior performance in HER and OER, making it a highly efficient and multifunctional electrocatalyst.

[0088] 2.3 In-situ characterization of NiCo / NC-TA catalyst

[0089] In exploring the mechanism of electrocatalytic oxygen reduction reaction (ORR) and designing highly efficient catalysts, real-time monitoring of the structural dynamics of the active sites is crucial. This study employed in-situ Raman spectroscopy to conduct an in-depth analysis of the electronic and atomic structure evolution of the NiCo / NC-TA electrocatalyst, in which Ni-N and Co-N coexist, during the ORR process.

[0090] In the pursuit of elucidating the mechanism of the electrocatalytic oxygen reduction reaction (ORR) and designing advanced catalysts, real-time monitoring of the structural dynamics of active sites is crucial. In this study, in-situ Raman spectroscopy was employed to investigate the dynamic structure and electronic evolution of active sites during ORR. In the initial state, such as... Figure 4 As shown in figure a, no significant Raman peaks were observed, indicating that ORR has not yet started. The Raman spectrum shows a peak at approximately 1600 cm⁻¹. -1 and 1350cm -1 The two characteristic peaks correspond to the G and D bands of carbon, respectively. Throughout the test, the ID / IG ratio remained stable, confirming the high structural stability of the NiCo / NC-TA electrocatalyst under ORR conditions. When the potential was increased to 1.1 V vs. RHE, the peaks at 605 cm⁻¹... -1 A new peak appeared, which was attributed to the formation of CoOOH. As the potential decreased, the peak at 500 cm⁻¹... -1 The peak at 1048 cm⁻¹ gradually becomes more prominent, indicating the formation of Co(OH)₂ and thus revealing the transformation from CoOOH to Co(OH)₂ during the ORR process. Furthermore, at 1048 cm⁻¹... -1 The observed peaks are characteristic of the *OH deformation mode. The intensity of these peaks increases with further decrease in potential, indicating a significant interaction between the Co-N active sites and superoxide ions (*OOH) in NiCo / NC-TA. These findings provide valuable insights into the catalytic behavior of NiCo / NC-TA electrocatalysts in the ORR process.

[0091] To further elucidate the sources of the anomalous catalytic performance of NiCo / NC-TA catalysts in the oxygen reduction reaction (ORR), hydrogen evolution reaction (HER), and oxygen evolution reaction (OER), we performed density functional theory (DFT) simulations. Based on XAS results, we constructed structural models of Ni-N4, Co-N4, and Ni-N4 / Co-N4 to represent Ni / NC-TA, Co / NC-TA, and NiCo / NC-TA catalysts, respectively. After optimization, when the distance between Ni and Co atoms is approximately [missing information], [missing information]. At that time, the Ni-N4 / Co-N4 system exhibited a superior electronic structure, compared with ( Figure 1 e) Consistent. Comparative analysis of charge density differences ( Figure 4bc) shows that the Co atoms in Co / NC-TA and NiCo / NC-TA lost 0.9128 e - and 0.9638e - Introducing Ni atoms into the NiCo / NC-TA system results in more charge transfer from Co-N4 to the substrate, which may further reduce the d-band center of the Co sites and alleviate excessive adsorption of intermediates. The ORR free energy curve ( Figure 4 d) shows that at a standard electrode potential of 1.23 V, the rate-determining steps (RDS) for the Ni-N4 and Co-N4 sites in the NiCo / NC-TA system, and for Co / NC-TA and Ni / NC-TA, are O2 to *OOH, requiring Gibbs free energy changes (ΔG) of 1.42 eV, 0.44 eV, 0.51 eV, and 1.24 eV, respectively. This indicates that the Co-N4 site in the NiCo / NC-TA system overcomes the lowest energy barrier in the ORR after the introduction of Ni, promoting the reaction. The Ni-N4 site in Ni / NC-TA and NiCo / NC-TA has a higher energy barrier in the *OOH→*O step, thus tending to protonate and form 2e ... - The process. Compared to Ni-N4, the Co-N4 sites in Co / NC-TA and NiCo / NC-TA are more prone to OO bond breakage, which is beneficial for 4e. - ORR. In 4e - In ORR, the Co-N4 site is the only active site in the NiCo / NC-TA system, while the Ni-N4 site plays a regulatory role.

[0092] In the HER process, we examined the Volmer-Heyrovsky mechanism under alkaline conditions. The HER process on NiCo / NC-TA is as follows: Figure 4 As shown in e, the rate-determining step (RDS) for Co / NC-TA is the adsorption of H2O, with a ΔG value of 0.53 eV. The RDS for Co-N4 / Ni-N4 in Ni / NC-TA and NiCo / NC-TA is from *H2O to *H and OH. - The dissociation of *H adsorption at the Co-N4 sites in the Ni-N / Co-N system showed ΔG values ​​of 1.95 eV, 0.49 eV, and 1.87 eV, respectively. Compared to Co / NC-TA, the introduction of Ni led to a shift in the major adsorption intermediate from *H2O to *H during the HER process, which is more favorable for the HER reaction. This indicates that Co-N4 in the NiCo / NC-TA system exhibits the best catalytic activity in alkaline HER, with the nearby Ni-N4 moiety promoting the dissociation of *H2O from the Co-N4 active site. Consistent with the Gibbs free energy of *H adsorption, the ΔG values ​​of the Co-N4 active site in the Ni-N / Co-N system were 1.95 eV, 0.49 eV, and 1.87 eV, respectively. H*=0.16eV) is lower than that of a single Co-N4 active site (ΔG H* =0.18eV)( Figure 4 f) indicates that the Co-N4 active site in the NiCo / NC-TA system exhibits optimal *H adsorption strength. The nearby Ni-N4 moiety optimizes *H adsorption at the Co-N4 active site.

[0093] During the OER process ( Figure 4 (g) At the standard test potential of 1.23V, the RDS of NiCo / NC-TA Co-N4 and Co / NC-TA is O* formation, with ΔG values ​​of 0.34eV and 0.39eV, respectively, while the RDS of Ni / NC-TA and NiCo / NC-TA Ni-N4 is OH* formation, with ΔG values ​​of 0.94eV and 0.87eV, respectively. These results demonstrate that the RDS energy barrier of NiCo / NC-TA Co-N4 is lower than that of Co / NC-TA and Ni / NC-TA. Due to the introduction of adjacent Ni-N4 sites, the Co-N4 sites in the NiCo / NC-TA system exhibit an advantage in OER performance.

[0094] Furthermore, the projected density of states (PDOS) Figure 4 h) Calculations show that the d-band center of Ni-N4 in NiCo / NC-TA (-1.953 eV) is further away from the Fermi level than that of Ni / NC-TA (-1.925 eV); similarly, the d-band center of Co-N4 in NiCo / NC-TA (-1.2 eV) is also further away from the Fermi level than that of Co / NC-TA (-0.54 eV). Therefore, due to the introduction of Ni atoms, the d-band center of the NiCo / NC-TA catalyst shifts relative to the Fermi level. Because the d-band center is located further away from the Fermi level, the chemical bond between the active Co site and the oxygen-based intermediate becomes weaker, leading to a lower binding energy and thus reducing the free energy barrier of the reaction.

[0095] Experimental Example 3

[0096] The NiCo / NC-TA catalyst from Example 1 was used as the cathode catalyst in a zinc-air battery, with a coating amount of 1.5 mg / cm². 2 Zinc-air batteries (ZABs) were constructed using zinc sheets as the anode and a mixed solution of 6M KOH and 0.2M zinc acetate as the electrolyte. As a comparison, the Pt / C-20%+RuO2 electrocatalyst had the same coating amount, and the mass ratio of Pt / C-20% to RuO2 was 1:1.

[0097] The results show that zinc-air batteries (ZABs) with NiCo / NC-TA cathodes achieve a high MW cm⁻¹. -2peak power density ( Figure 5 a) and a high open-circuit potential of up to 1.32V ( Figure 5 b) This is superior to commercial Pt / C-20%+RuO2 (100MW cm⁻¹) -2 ). ( Figure 5 c) shows the range from 2 to 50 mA cm -2 Capacity at various discharge current densities within the range. When the current density reverses back to 2 mA cm⁻¹. -2 At that time, the capacity can be recovered very well. Even at 50 mA / cm -2 No significant decrease in discharge voltage was observed even at high current densities. Figure 5 As shown in d, the zinc-air battery based on NiCo / NC-TA operates at 10 mA cm⁻¹. -2 It also showed a capacity of 753mAh g. -1 Its specific capacity is much higher than that of Pt / C-20%+RuO2 (665mAh g). -1 The study was conducted based on zinc-air batteries through constant current discharge-charge cycles. Figure 5 e). For the NiCo / NC-TA-based zinc-air battery, stable cycle performance during discharge and charge processes can be observed within 120 hours (180 cycles), which is superior to the Pt / C-20%+RuO2-based zinc-air battery under the same test conditions, where the discharge voltage drops significantly within 30 hours, confirming the excellent stability of NiCo / NC-TA in practical zinc-air batteries.

[0098] In summary, a bimetallic single-atom catalyst was constructed by anchoring isolated Ni and Co atoms on a nitrogen-doped carbon substrate, and the proximity electron effect of adjacent Ni and Co atoms was utilized to synergistically promote electrocatalytic ORR, HER, and OER. Due to the modulation effect of adjacent Ni-N4, NiCo / NC-TA exhibits excellent trifunctional performance, showing higher intrinsic activity and long-term stability compared to Co / NC-TA. In-situ Raman spectroscopy confirmed a strong interaction between the Co-N active center and the superoxide ion OO in NiCo / NC-TA. Furthermore, DFT calculations revealed that Co-N is the active center of NiCo / NC-TA, and Ni-N is the modulating site, thereby improving the catalytic performance of NiCo / NC-TA catalysts in ORR, HER, and OER. This work reveals the modulation effect of isolated diatomic metal sites at the atomic scale, providing insights for the development of multifunctional, high-performance diatomic catalysts.

[0099] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A bimetallic single-atom NiCo / NC-TA electrocatalyst, characterized in that, With Zn 2+ Ni is a primary metal salt. 2+ Salt and Co 2+ The salt is a dual-doped metal salt. The main metal salt, the dual-doped metal salt and 2-methylimidazolium react to form an imidazolium zeolite framework; then the imidazolium zeolite framework is etched and carbonized to obtain the final product.

2. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 1, characterized in that, The molar ratio of Ni to Co in the dual-doped metal salt is 1:1, and the ratio of the molar amount of Zn to the sum of the molar amounts of Ni and Co in the main metal salt is 25:1-35:

1.

3. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 2, characterized in that, Zn 2+ The molar ratio of Zn to 2-methylimidazole in the salt is 1:(8-10).

4. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 1, characterized in that, The reaction is carried out at room temperature for 12-24 hours; Zn 2+ Salt, Ni 2+ Salt and Co 2+ All salts are nitrates, and the solvent used in the reaction is methanol.

5. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 1, characterized in that, The etching is carried out in a methanol solution of tannic acid, wherein the concentration of tannic acid is 2-5 g / L.

6. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 5, characterized in that, The imidazole zeolite framework was aged in a methanol solution of tannic acid for 5-15 minutes to complete the etching.

7. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 1, characterized in that, The carbonization is carried out under a protective atmosphere at a temperature of 880-950℃; the carbonization time is 2-4 hours.

8. The bimetallic single-atom NiCo / NC-TA electrocatalyst as described in claim 7, characterized in that, The carbonization time is 920-950℃; the carbonization time is 3-4h; the ratio of the molar amount of Zn to the sum of the molar amounts of Ni and Co in the main metal salt is 25:1-29:

1.

9. The application of a bimetallic single-atom NiCo / NC-TA electrocatalyst as described in any one of claims 1 to 8 in an electrocatalytic reaction, characterized in that, The electrocatalytic reaction is selected from one or more of the following: oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER).

10. The application as described in claim 9, characterized in that, The applications include using the bimetallic single-atom NiCo / NC-TA electrocatalyst as a cathode catalyst in a metal-air battery.

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