A nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst and a preparation method thereof

Abstract

This invention belongs to the field of catalyst technology and discloses a nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst and its preparation method. The catalyst has the molecular formula CoNi-MOF@ACW and the structure is a dodecahedral CoNi-MOF grown on nitrogen-doped biomass carbon ACW with Co and Ni in an atomically dispersed state. Preparation method: (1) Prepare nitrogen-doped biomass carbon ACW; (2) Prepare a complex of metallic nickel and PI-PINi; (3) Dissolve water-soluble zinc salt, water-soluble cobalt salt and PINi together in methanol to obtain solution A; (4) Add 2-methylimidazole to methanol to obtain solution B; (5) Add ACW to solution A, stir evenly and then add solution B, continue stirring evenly; (6) Take out the solid material to obtain the precursor CoPINi-MOF@ACW; (8) Wash CoPINi-MOF@ACW with methanol and then dry; (9) Embed CoPINi-MOF@ACW with NH4Cl and pyrolyze to obtain the target catalyst. The catalyst of this invention has extremely high ORR-OER bifunctional catalytic activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst and its preparation method. Background Technology

[0002] Due to the rapid depletion of resources and over-reliance on fossil fuels, developing renewable energy and improving its utilization efficiency has become a key factor determining the future of human society. Achieving efficient and circular utilization of renewable energy requires establishing an energy conversion pathway that is rich in raw materials, has high utilization efficiency, and is environmentally friendly. Rechargeable zinc-air batteries (ZABs) are considered the most promising energy storage system due to their advantages such as high theoretical energy density, low cost, environmental friendliness, and the safety of non-flammable electrolytes. During the charging and discharging process of ZABs, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key factors affecting energy conversion efficiency. The inherently slow kinetic rates of ORR and OER lead to high overpotentials, low energy conversion rates, and low power density of ZABs, greatly limiting their application. High-performance oxygen electrocatalysts are key to solving these problems. Traditionally, noble metals such as Pt and Ru have become commercial catalysts due to their high catalytic activity in ORR and OER. However, their scarcity and poor bifunctionality limit the large-scale application of this technology. Therefore, developing bifunctional, noble metal-free electrocatalysts with high activity and low cost is an urgent and challenging task.

[0003] Due to their unique organic and inorganic structures, metal-organic frameworks (MOFs) can anchor and disperse metals within a carbon framework, forming atomically dispersed metal sites. This makes MOFs a precursor for synthesizing atomically dispersed catalysts with excellent electrocatalytic performance. Among all MOFs, nitrogen-rich imidazole molecular sieve frameworks (ZIFs) are typical sacrificial templates for preparing single-metal atom and nitrogen-doped carbon materials through pyrolysis. The transition metal within the framework can interact with nitrogen and carbon atoms to form a homogeneous metal-nitrogen-carbon structure as active sites. However, ZIFs, as sacrificial templates, require high-temperature carbonization, resulting in layered stacking, which significantly reduces the utilization of active sites. Therefore, the electrocatalytic activity of these single ZIF-derived carbon materials for ORR and OER does not meet current requirements. To overcome this limitation, there is an urgent need for a renewable resource as a support, serving as the framework for deposited catalysts and achieving a highly dispersed state. Biomass-derived carbon materials are considered ideal supports for electrocatalysts due to their renewable, environmentally friendly, and low-cost advantages.

[0004] Chinese patents CN202210921948.5 (application date August 2, 2022) and CN202210802486.5 (application date July 7, 2022) both directly synthesize bimetallic MOFs. However, due to the lack of a support, the dispersion is poor, and the active sites cannot be fully utilized, failing to meet the current requirements for ORR-OER performance. Therefore, researching and developing bifunctional catalysts that meet ORR-OER requirements is an urgent task for researchers in this field. Summary of the Invention

[0005] To address the technical problems existing in the prior art: ① Existing catalysts lack a support, resulting in poor dispersion and inability to fully utilize active sites; ② Noble metal catalysts have insufficient activity and stability in ORR-OER bifunctionality. The purpose of this invention is to provide a nitrogen-doped carbon-supported cobalt-nickel bifunctional ORR-OER catalyst and its preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst, wherein the catalyst has the molecular formula CoNi-MOF@ACW, and the structure is a dodecahedral CoNi-MOF grown on nitrogen-doped biomass carbon ACW, with Co and Ni existing in an atomically dispersed state.

[0007] The preparation method and steps are as follows: (1) Preparation of nitrogen-doped biomass carbon ACW; (2) Dissolve the water-soluble nickel salt and 1,10-phenanthroline (PI) in water, freeze until particulate matter precipitates, then thaw at room temperature, centrifuge the solution, discard the supernatant to obtain a mud-like substance, wash with ice water, and finally dry at room temperature to obtain the complex of metallic nickel and PI—PINi (PINi structure: 3 1,10-phenanthroline groups coordinate with metallic nickel, and then form a metal salt with a nitrate group); in this step, the water-soluble nickel salt is calculated based on the elemental nickel, and the ratio of water-soluble nickel salt, 1,10-phenanthroline and water is 1 mmol: (3-3.5) mmol: (15-20) mL; (3) Dissolve the water-soluble zinc salt, water-soluble cobalt salt and PNI together in methanol to obtain solution A; in this step, the water-soluble zinc salt is calculated as zinc element, the water-soluble cobalt salt is calculated as cobalt element, and the ratio of water-soluble zinc salt, water-soluble cobalt salt, PNI and methanol is (2.5-3.0) mmol∶1 mmol∶(0.15-0.20) mmol∶(10-15) mL; (4) Add 2-methylimidazole to methanol to obtain solution B; in this step, the ratio of 2-methylimidazole to methanol is (16-20) mmol: (10-15) mL. (5) Add nitrogen-doped biomass carbon ACW to solution A, stir evenly, then add solution B and continue stirring evenly; in this step, the ratio of ACW, solution A and solution B is 0.1 g∶(10-15) mL∶(10-15) mL; (6) After step (5) is completed, the solid material is removed to obtain the precursor - nitrogen-doped biomass carbon ACW supported CoPINi-MOF, i.e., CoPINi-MOF@ACW; (7) Clean CoPINi-MOF@ACW with methanol and then dry it; (8) The dried CoPINi-MOF@ACW was embedded in NH4Cl, heated to 550-600 ℃, and pyrolyzed for 3-5 h; then heated to 900-920 ℃ and pyrolyzed for 2-3 h to obtain the target catalyst CoNi-MOF@ACW.

[0008] Preferably, the water-soluble nickel salt is Ni(NO3)2·6H2O, the water-soluble zinc salt is Zn(NO3)2·6H2O, and the water-soluble cobalt salt is Co(NO3)2·6H2O.

[0009] Ideally, in step (8), the heating rate at both locations is controlled at 3-5 ℃ / min.

[0010] Preferably, step (1) for preparing nitrogen-doped biomass carbon ACW is as follows: (1.1) Clean the wood blocks ultrasonically with anhydrous ethanol and then dry them; (1.2) Dissolve KCl, ZnCl2, and NH4Cl in water; in this step, the ratio of KCl, ZnCl2, NH4Cl and water is 1 mmol : (2.5-3.0) mmol : (55-65) mmol : (7-10) mL; (1.3) Soak the wood blocks prepared in step (1.1) in the salt solution prepared in step (1.2), stir at room temperature, and then dry the cedar wood blocks. (1.4) The fir blocks prepared in step (1.3) are heated to 900-920 °C under a protective atmosphere, pyrolyzed for 2-3 h, and cooled to room temperature to obtain nitrogen-doped biomass carbon ACW.

[0011] Preferably, the wood block is a fir wood block.

[0012] Ideally, in step (1.4), the heating rate is controlled at 3-5 ℃ / min.

[0013] Beneficial effects: 1. This invention creatively designs a CoNi-MOF catalyst supported on nitrogen-doped biomass carbon ACW, comprising a nitrogen-doped biomass carbon support ACW and CoNi-MOF supported on ACW. The metal cations cobalt and nickel on CoNi-MOF, through the synergistic coupling effect between ACW and MOF, not only overcome the aggregation and stacking of MOF catalysts during synthesis, but also greatly increase the dispersibility of MOF and improve the utilization rate of active sites. The nitrogen-doped biomass carbon ACW is obtained by pyrolysis of wood blocks soaked in KCl, ZnCl2 and NH4Cl solutions, which regulates the charge density distribution of carbon components and improves the ORR reaction activity, with the half-wave potential of ORR reaching 0.883 V.

[0014] 2. The catalyst prepared by this invention achieves metal doping of MOF and synthesizes an atomically dispersed bimetallic catalyst. The adsorption of OH* on the active site by CoNi-MOF@ACW is improved by the doping of metallic Ni, thereby improving the OER performance. The overpotential of OER is as low as 296 mV.

[0015] 3. This invention introduces Zn during the preparation process. 2+ The boiling point of Zn is 907 ℃. The pyrolysis temperature of the tubular furnace reaches the boiling point of Zn, and Zn is eventually removed. During the Zn removal process, the dispersion of CoNi and carbon defects will increase.

[0016] 4. Low cost, good intrinsic and application performance: The CoNi-MOF@ACW catalyst prepared using non-precious metals showed an ORR half-wave potential of 0.883 V, comparable to 0.860 V for 20% Pt / C, at a current density of 10 mA·cm⁻¹. -2 Below this, the overpotential of OER is 296 mV, close to that of RuO2 (240 mV); the voltage gap (Δ) E = E j=10 - E 1 / 2 With a V as low as 0.64, it exhibits extremely high ORR-OER bifunctional catalytic activity, outperforming commercial catalysts prepared using noble metals such as 20% Pt / C (ΔV). E = 0.82V); Applying the CoNi-MOF@ACW catalyst to the cathode of a zinc-air battery yielded a high efficiency of 212.5 mW·cm⁻¹. -2 It achieves a peak power density and boasts a cycling stability of up to 300 h, thus addressing the issues of insufficient bifunctionality and poor stability of 20% Pt / C+RuO2 noble metal catalysts in ORR-OER (peak power density: 80.9 mW·cm⁻¹). -2 Cyclic stability: 50 h). Attached Figure Description

[0017] Figure 1 : Figure 1 a and b are longitudinal and transverse scanning electron microscope images of ACW (product S4 of Example 1), respectively. Figure 1 c is a scanning electron microscope image of CoNi-MOF (Comparative Example 3); CoNi-MOF@ACW (Example 1) is uncarbonized ( Figure 1 d) and after carbonization ( Figure 1 Scanning electron microscope images of e and f); Figure 1 gi is a transmission electron microscope image of CoNi-MOF@ACW (Example 1).

[0018] Figure 2 X-ray diffraction patterns of carbonized cedar (CW), CoNi-MOF@ACW (Example 1), CoNi-MOF (Comparative Example 3), and ACW (Product of Example 1S4) Figure 2 a, b) and Raman spectra ( Figure 2 c).

[0019] Figure 3 The ORR of CoNi-MOF@ACW (Example 1) with Co-MOF@ACW (Comparative Example 1), Ni-MOF@ACW (Comparative Example 2), CoNi-MOF (Comparative Example 3), ACW (Example 1 S4 product), 20% Pt / C, and RuO2, respectively, were as follows: Figure 3 a), OER ( Figure 3 b) and overpotential Δ E ( Figure 3 c) Performance comparison chart.

[0020] Figure 4 Power density of a liquid zinc-air battery assembled based on CoNi-MOF@ACW (Example 1) and 20% Pt / C+RuO2 ( Figure 4 a) and constant current charge-discharge cycle ( Figure 4 b) Analyze the comparison chart.

[0021] Figure 5 Power density of a quasi-solid-state zinc-air battery assembled based on CoNi-MOF@ACW (Example 1) and 20% Pt / C+RuO2 ( Figure 5 a) and constant current charge-discharge cycle ( Figure 5 b) Analyze the comparison chart. Detailed Implementation

[0022] To make the present invention clearer and more explicit, the present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0023] Example 1 A nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst, wherein the catalyst has the molecular formula CoNi-MOF@ACW, and the structure is a dodecahedral CoNi-MOF grown on nitrogen-doped biomass carbon ACW, with Co and Ni existing in an atomically dispersed state.

[0024] The catalyst is prepared in the following steps: S1. Cut the cedar wood into even pieces, with dimensions of 2.0 cm (length) × 2.0 cm (width) × 0.5 cm (height). Clean the pieces with anhydrous ethanol using ultrasonic cleaning for 30 min and dry them at 60 ℃ for 12 h. S2. Prepare a salt solution by dissolving KCl, ZnCl2, and NH4Cl in deionized water. The ratio of KCl, ZnCl2, NH4Cl, and deionized water is 0.48 g: 2.4 g: 20 g: 50 mL. S3. Soak the fir blocks prepared in S1 in the salt solution prepared in S2, stir at room temperature for 24 h, remove the fir blocks and dry them in a drying oven at 60 ℃ for 12 h. S4. The fir blocks prepared in S3 were placed in a tube furnace and calcined. The temperature was increased to 900℃ at 5℃ / min under an argon atmosphere, and pyrolyzed for 2 h. After cooling to room temperature, nitrogen-doped biomass carbon (labeled as ACW) was obtained. S5. Dissolve 3.0 g Ni(NO3)2·6H2O and 5.4 g 1,10-phenanthroline (PI) in 150 mL of deionized water, stir at 70 ℃ for 1 h, freeze at -20 ℃ until white particles precipitate, then thaw at room temperature, centrifuge the solution, discard the supernatant to obtain a pink mud-like substance, wash with ice water, and finally dry at room temperature to obtain the Ni-PI complex—PINi; S6. Under magnetic stirring, 0.7 g Zn(NO3)2·6H2O, 0.25 g Co(NO3)2·6H2O and 0.12 g PNI obtained in S5 were dissolved together in 10 mL methanol and stirred thoroughly at room temperature for 30 min to obtain solution A. S7. Add 1.46 g of 2-methylimidazole to 10 mL of methanol to obtain solution B; S8. Add 0.1 g of ACW prepared in S4 to solution A prepared in S6 and stir for 30 min. S9. Add the B solution obtained in S7 to the solution in S8 and stir for 24 h. S10. Remove the solid material to obtain the precursor - nitrogen-doped biomass carbon ACW supported CoPINi-MOF (labeled as CoPINi-MOF@ACW). S11. Wash the CoPINi-MOF@ACW obtained in S10 with methanol and dry it in a vacuum drying oven at 60℃ for 12 h. S12. The dried CoPINi-MOF@ACW from S11 was embedded in NH4Cl, heated to 550 ℃ at 3 ℃ / min, and pyrolyzed for 4 h; then heated to 900 ℃ at 3 ℃ / min and pyrolyzed for 3 h to obtain CoNi-MOF@ACW.

[0025] Comparative Example 1 The difference from Example 1 is that in step S6, the PINi obtained in S5 is not added; otherwise, it is the same as in Example 1. The resulting product is Co-MOF@ACW.

[0026] Comparative Example 2 The difference from Example 1 is that Co(NO3)2·6H2O is not added in step S6; all other steps are the same as in Example 1. The resulting product is Ni-MOF@ACW.

[0027] Comparative Example 3 The difference from Example 1 is that in step S8, the ACW prepared in S4 is not added; all other steps are the same as in Example 1. The resulting product is CoNi-MOF.

[0028] Catalyst structure characterization Figure 1 a and 1b are longitudinal and transverse scanning electron microscope images of ACW (product of Example 1 S4), respectively. Figure 1 c is a scanning electron microscope image of CoNi-MOF (Comparative Example 3); CoNi-MOF@ACW (Example 1) is uncarbonized ( Figure 1 d) and after carbonization ( Figure 1 The scanning electron microscope image of CoNi-MOF@ACW (Example 1) shows that the uncarbonized product refers to the product CoPINi-MOF@ACW in Example 1 S10. Figure 1 gi is a transmission electron microscope image of CoNi-MOF@ACW (Example 1). Figure 1 The longitudinal section of ACW shows that the holes are evenly distributed and of uniform size. Figure 1 b shows its cross-sectional electron micrograph as a polygonal channel with an inner diameter of 20-50 µm. Figure 1 c shows a scanning electron microscope image of CoNi-MOF (Comparative Example 3) that is a typical dodecahedral shape with a size ranging from 500 nm to 1 µm. Multiple dodecahedrons are closely arranged together to form a layered, densely packed structure, and the size of a single dodecahedron remains unchanged. Figure 1The scanning electron microscope image of CoPINi-MOF@ACW (product of Example 1 S10) clearly shows the ZIF precursors grown in situ and anchored on the channels and outer walls. Figure 1 The EF diagram shows that after pyrolysis of CoPINi-MOF@ACW (product of Example 1 S10), the ZIFs loaded on the ACW surface exhibited in-plane shrinkage and partial collapse into small pores. However, after high-temperature calcination, they still maintained the dodecahedral crystal structure. The CoPINi-MOF loaded on ACW was uniformly distributed on the inner walls of the natural pores of carbonized cedar wood, without obvious accumulation and with relatively uniform shape and size. This is attributed to the confinement effect of the natural pores of the wood, which limited the growth of MOF and caused it to be uniformly distributed along the pore walls. Even after high-temperature pyrolysis, the dodecahedral shape of the MOF showed obvious in-plane shrinkage and partial collapse, but no obvious aggregation occurred. Figure 1 High-resolution transmission electron microscopy (TEM) of gi further revealed the detailed structure and morphology of CoNi-MOF@ACW (Example 1), and no lattice fringes corresponding to Co / Ni metal were observed. These results indicate the presence of atomically dispersed Co / Ni in CoNi-MOF@ACW (Example 1).

[0029] Figure 2 X-ray diffraction patterns of carbonized cedar (CW), CoNi-MOF@ACW (Example 1), CoNi-MOF (Comparative Example 3), and ACW. Figure 2 a, b) and Raman spectra ( Figure 2 c). The preparation process of carbonized cedar (CW) is as follows: S1, cedar wood is cut into uniform blocks with dimensions of 2.0 cm (length) × 2.0 cm (width) × 0.5 cm (height), ultrasonically cleaned with anhydrous ethanol for 30 min, and dried at 60℃ for 12 h; S2, the cedar blocks prepared in S1 are placed in a tube furnace and calcined, heated to 900℃ at 5℃ / min under an argon atmosphere, pyrolyzed for 2 h, and cooled to room temperature to obtain carbonized cedar (labeled CW). Figure 2 In a, the diffraction peaks of ACW at 23.7° and 43.5° correspond to the (002) and (101) crystal planes of graphitic carbon, respectively. Compared with carbonized cedar (CW), the broad C (002) peak in the XRD mode of ACW shifts to a larger angle, which is because the doping of N atoms reduces the interplanar spacing of CW. Figure 2In sample b, the Co / Ni diffraction peaks of CoNi-MOF (Comparative Example 3) highly overlap, with the diffraction peaks at 44.2°, 51.6°, and 76.0° corresponding to the (111), (200), and (220) crystal planes, respectively. However, no diffraction peaks for metallic Co and Ni were found in the XRD pattern of CoNi-MOF@ACW (Example 1), indicating that Co and Ni elements may exist in an atomically dispersed manner. The Raman spectra of the materials are as follows: Figure 2 As shown in c, two distinct peaks can be observed in all samples, located at 1343 cm⁻¹. -1 The D-band peak originates from sp 3 The amorphous state of carbon represents the degree of disorder in carbon, located at 1589 cm⁻¹. -1 The G-band peak represents sp 2 The in-plane stretching vibrations of hybrid carbon represent the degree of graphitization of carbon. I D / I G The ratio is an important parameter reflecting the defect status of carbon materials. ACW, CoNi-MOF (Comparative Example 3), and CoNi-MOF@ACW (Example 1) are compared. I D / I G The ratios were 0.978, 1.01 and 1.07, respectively, indicating that CoNi-MOF@ACW (Example 1) has higher disorder and more carbon defects, with a higher chance of exposing active sites, further increasing ORR and OER performance.

[0030] Electrochemical performance testing of catalyst ORR / OER The catalysts CoNi-MOF@ACW (Example 1), Co-MOF@ACW (Comparative Example 1), Ni-MOF@ACW (Comparative Example 2), CoNi-MOF (Comparative Example 3), and ACW (Product S4 of Example 1) prepared according to this invention were tested under a CHI760E electrochemical workstation. First, the rotating disk electrode (RDE) was polished with Al2O3 powder (0.05 µm). Then, a dispersion consisting of catalyst (4 mg), anhydrous ethanol (500 µL), and 5 wt% Nafion (50 µL) was ultrasonically treated for 30 min. Next, the prepared uniform dispersion (15 µL) was added dropwise to the glassy carbon surface of the RDE in three portions. Using the RDE as the working electrode, a platinum wire electrode as the counter electrode, and a silver / silver chloride electrode (Ag / AgCl) as the reference electrode, a three-electrode system was formed, and the tests were performed in 0.1 M KOH electrolyte. A comparative sample was prepared using a commercially available 20% Pt / C, RuO2 catalyst.

[0031] Figure 3ORR for CoNi-MOF@ACW (Example 1), Co-MOF@ACW (Comparative Example 1), Ni-MOF@ACW (Comparative Example 2), CoNi-MOF (Comparative Example 3), ACW, 20% Pt / C, and RuO2 Figure 3 a), OER ( Figure 3 b) and overpotential Δ E ( Figure 3 c) Performance comparison chart. From Figure 3 As can be seen from a, CoNi-MOF@ACW (Example 1) has a high half-wave potential (0.883 V) comparable to 20% Pt / C (0.860 V), and its ORR performance is significantly better than other catalysts in the comparative sample; Figure 3 b is the OER performance test of the catalyst, at 10 mA·cm⁻¹. -2 The measured overpotential of CoNi-MOF@ACW (Example 1) was 296 mV, which is close to that of RuO2 (240 mV) and superior to that of other comparative samples. Figure 3 c is the Δ value derived from the catalyst's ORR and OER performance. E Figure 1 shows CoNi-MOF@ACW (Example 1) at 10 mA·cm⁻¹. -2 The potential difference (Δ) between the voltage at current density and the half-wave voltage of ORR E It is only 0.64 V, which is lower than that of commercial catalysts with 20% Pt / C and RuO2.

[0032] The results of Example 1 and Comparative Examples 1-3 are shown in Table 1.

[0033] The following results were obtained from the comparison: ① As can be seen from Comparative Examples 1 and 2, the ORR and OER performance of single metal cobalt or nickel are weaker than those of bimetallic components (Example 1); ② As can be seen from Comparative Example 3, if the catalyst does not use an ACW support, the bifunctional activity is weakened.

[0034] Catalyst Zinc-Air Battery Performance Testing A dispersion consisting of the CoNi-MOF@ACW catalyst (Example 1) prepared in this invention (4 mg), anhydrous ethanol (500 µL), and 5 wt% Nafion (50 µL) was ultrasonically treated for 30 min to obtain a catalyst slurry. The catalyst slurry was uniformly dispersed on hydrophobic carbon paper with a dropping area of ​​2 cm (length) × 2 cm (width) and dried at 60 ℃ for 2 h to obtain a catalyst loading of 1.0 mg·cm⁻¹. -2 New carbon paper. The same procedure was followed, but a control sample was prepared using 20% ​​Pt / C+RuO2 at a mass ratio of 1:1.

[0035] The prepared catalyst was used in a zinc-air battery (ZABs) for practical application testing. The zinc sheet was used as the anode of the battery, and the air electrode, which was assembled in sequence with an air diffusion layer, nickel foam and carbon paper coated with the catalyst, was used as the cathode. The electrolyte was a mixed aqueous solution of 6M KOH + 0.2M Zn(OAc)2. Figure 4 The power density of the liquid zinc-air battery assembled based on CoNi-MOF@ACW (Example 1) and 20% Pt / C+RuO2 is ( Figure 4 a) and constant current charge-discharge cycle ( Figure 4 b) Analyze the comparison chart. From Figure 4 It can be seen that ZABs with a cathode coated with CoNi-MOF@ACW (Example 1) catalyst have a high power density (212.5 mW·cm⁻¹). -2 ), far exceeding 20% ​​Pt / C+RuO2 (80.9 mW·cm -2 Furthermore, it exhibits excellent durability within 300 h with no obvious signs of degradation, while ZABs based on 20% Pt / C+RuO2 show a large charge-discharge gap after 50 h of cycling.

[0036] 3.0 g of polyvinyl alcohol (PVA) was dissolved in 30 mL of deionized water and stirred at 90 °C for 2 h to obtain a transparent solution. Then, 20 mL of 6 M KOH solution was added, stirred for 30 min, and stored at room temperature for 5 h to form a PVA gel. A quasi-solid-state ZAB was assembled in the following order: zinc foil anode, PVA gel electrolyte, catalyst CoNi-MOF@ACW (Example 1) cathode, and nickel foam current collector. Figure 5 The power density of the quasi-solid-state zinc-air battery assembled based on CoNi-MOF@ACW (Example 1) and 20% Pt / C+RuO2 is ( Figure 5 a) and constant current charge-discharge cycle ( Figure 5 b) Analyze the comparison chart. From Figure 5 It can be seen that the quasi-solid-state battery using CoNi-MOF@ACW (Example 1) as the cathode has a maximum power density of 54.3 mW·cm⁻¹. -2 To further test the stability of CoNi-MOF@ACW (Example 1), a test was conducted at 2 mA·cm⁻¹. -2 Constant current charge-discharge cycle tests were conducted, and the assembled quasi-solid-state ZABs showed stable charge-discharge stability during 60 h of cycling.

Claims

1. A method for preparing a nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst, characterized in that, The steps are as follows: (1) Preparation of nitrogen-doped biomass carbon ACW; (2) Dissolve the water-soluble nickel salt and 1,10-phenanthroline PI in water by stirring, freeze until particulate matter precipitates, then thaw at room temperature, centrifuge the solution, discard the supernatant to obtain a mud-like substance, wash with ice water, and finally dry at room temperature to obtain the complex of metallic nickel and PI-PINi; in this step, the water-soluble nickel salt is calculated as nickel element, and the ratio of water-soluble nickel salt, 1,10-phenanthroline and water is 1 mmol: (3-3.5) mmol: (15-20) mL; (3) Dissolve the water-soluble zinc salt, water-soluble cobalt salt and PNI together in methanol to obtain solution A; in this step, the water-soluble zinc salt is calculated as zinc element, the water-soluble cobalt salt is calculated as cobalt element, and the ratio of water-soluble zinc salt, water-soluble cobalt salt, PNI and methanol is (2.5-3.0) mmol∶1 mmol∶(0.15-0.20) mmol∶(10-15) mL; (4) Add 2-methylimidazole to methanol to obtain solution B; in this step, the ratio of 2-methylimidazole to methanol is (16-20) mmol: (10-15) mL. (5) Add nitrogen-doped biomass carbon ACW to solution A, stir evenly, then add solution B and continue stirring evenly; in this step, the ratio of ACW, solution A and solution B is 0.1 g∶(10-15) mL∶(10-15) mL; (6) After step (5) is completed, the solid material is removed to obtain the precursor - nitrogen-doped biomass carbon ACW supported CoPINi-MOF, i.e., CoPINi-MOF@ACW; (7) Clean CoPINi-MOF@ACW with methanol and then dry it; (8) The dried CoPINi-MOF@ACW was embedded in NH4Cl, heated to 550-600 ℃, and pyrolyzed for 3-5 h; then heated to 900-920 ℃ and pyrolyzed for 2-3 h to obtain the target catalyst CoNi-MOF@ACW.

2. The method for preparing the nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst as described in claim 1, characterized in that: The water-soluble nickel salt is Ni(NO3)2·6H2O, the water-soluble zinc salt is Zn(NO3)2·6H2O, and the water-soluble cobalt salt is Co(NO3)2·6H2O.

3. The method for preparing the nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst as described in claim 1, characterized in that: In step (8), the heating rate at both locations is controlled at 3-5 ℃ / min.

4. The method for preparing the nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst as described in claim 1, characterized in that, Step (1) for preparing nitrogen-doped biomass carbon ACW is as follows: (1.1) Clean the wood blocks ultrasonically with anhydrous ethanol and then dry them; (1.2) Dissolve KCl, ZnCl2, and NH4Cl in water; in this step, the ratio of KCl, ZnCl2, NH4Cl and water is 1 mmol : (2.5-3.0) mmol : (55-65) mmol : (7-10) mL; (1.3) Soak the wood block prepared in step (1.1) in the salt solution prepared in step (1.2), stir at room temperature, remove the wood block and dry it; (1.4) The wood block prepared in step (1.3) is heated to 900-920 °C under a protective atmosphere, pyrolyzed for 2-3 h, and cooled to room temperature to obtain nitrogen-doped biomass carbon ACW.

5. The method for preparing the nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst as described in claim 4, characterized in that: The wood block is a fir wood block.

6. The method for preparing the nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst as described in claim 4, characterized in that: In step (1.4), the heating rate is controlled at 3-5 ℃ / min.

7. A nitrogen-doped carbon-supported cobalt-nickel dual-site ORR-OER catalyst prepared by the method described in claim 1, characterized in that: The catalyst has the molecular formula CoNi-MOF@ACW and a structure of dodecahedral CoNi-MOF grown on nitrogen-doped biomass carbon ACW, with Co and Ni existing in an atomically dispersed state.

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