Self-supporting Biy-coated CoOOH / NF composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of electro-catalytic water decomposition, and relates to a self-supporting Biy-coated CoOOH / NF composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: synthesizing an ultrathin Bix-coated Co-MOF / NF precursor on a foamed nickel carrier through a solvothermal method; then, inducing the precursor to generate surface reconstruction through electrochemical treatment, converting the precursor into a CoOOH carrier, and synchronously regulating and controlling the oxygen vacancy concentration in the CoOOH carrier; the self-supporting Biy-coated CoOOH composite material is obtained. The obtained composite material has a high-activity specific surface area, accurate control of the size of bismuth species can be achieved, and then continuous regulation and control of catalytic performance are achieved. And the catalyst shows excellent oxygen evolution reaction catalytic activity and long-term stability, and is suitable for an efficient water electrolysis hydrogen production system. According to the invention, the problem of performance degradation caused by the use of a binder is avoided, and a universal and reliable technical route is provided for controllable preparation of the high-performance self-supporting electrode.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic water splitting technology, and relates to a self-supporting Bi y @CoOOH / NF composite materials, their preparation methods, and applications. Background Technology

[0002] Electrocatalytic water splitting for hydrogen production is one of the key technologies driving the clean energy transition. Among numerous non-precious metal catalysts, cobalt-based materials (especially cobalt hydroxyl oxide generated through electrochemical surface reconstruction) are considered to have good application prospects in the alkaline oxygen evolution reaction. Surface reconstruction is the process by which precursors form a real active structure through rapid dissolution and redeposition under reaction conditions. However, the generated CoOOH usually suffers from insufficient intrinsic activity and poor conductivity, limiting its further application. To further improve the catalytic performance of CoOOH, introducing a second metal element to construct a heterogeneous interface has become an effective strategy. Among them, bismuth, a main group metal, has attracted attention due to its ability to adjust the d-band center of transition metals and optimize the adsorption energy of reaction intermediates. However, traditional synthesis methods (such as hydrothermal and calcination) often lead to severe agglomeration of bismuth when it is introduced, forming micron or nano-sized particles, resulting in a decrease in the density of active sites and a weakening of the interaction between bismuth and the support.

[0003] Studies have shown that the catalytic regulation ability of bismuth is closely related to its size: when present in the form of single atoms or quantum dots, it readily forms strong metal-support interactions, significantly promoting interfacial charge transfer and reaction kinetics; while the regulatory effect of large-sized bismuth particles is weak, and they may even cover the active sites. Currently, there is a lack of reliable methods to simultaneously achieve precise control of oxygen vacancy concentration during surface reconstruction and to use vacancy anchoring of bismuth species to control their size (from single atoms to quantum dots). This lack of technology leads to unclear active structures, reliance on empirical exploration for catalytic performance optimization, and difficulty in achieving rational material design.

[0004] Therefore, there is an urgent need to develop a novel material preparation strategy that can synergistically couple surface reconstruction, defect engineering, and metal size control to achieve precise construction of high-performance heterojunction electrocatalysts at the atomic / nanoscale. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a self-supporting Bi y @CoOOH / NF composite materials, their preparation methods, and applications. This invention achieves synergistic regulation of oxygen vacancy concentration and bismuth species size through a controllable electrochemical reconstruction strategy, thereby precisely constructing high-performance oxygen evolution reaction electrocatalysts at the atomic / nanoscale.

[0006] The technical solution of the present invention is as follows: A self-supporting Bi yThe preparation method of @CoOOH / NF composite material includes the following steps: (1) Dissolve Co(NO3)3·6H2O in ethanol and DMF, and denote it as solution A; dissolve 1,4-H2BDC in deionized water and DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then carry out hydrothermal reaction of the mixture and the foamed nickel NF after washing with HCl and deionized water. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained; (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in Bi(NO3)3·5H2O solution, and then reacted continuously to obtain Bi. x @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor; (3) The Bi obtained in step (2) x A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed in 1 M KOH electrolyte within a specific potential range (relative to Ag / AgCl) to obtain self-supporting Bi2. y @CoOOH composite material (where y represents the Bi:Co atomic ratio in the sample).

[0007] Preferably, in step (1), the molar ratio of Co(NO3)2·6H2O to 1,4-H2BDC is (0.8~2):(0.8~2), and the concentration of Co(NO3)2·6H2O after dissolving in ethanol and DMF solution is 0.01-0.05 mol / L.

[0008] Preferably, in step (1) A, the volume ratio of ethanol to DMF is (1~2):(1~2).

[0009] Preferably, in step (1) B, the volume ratio of deionized water to DMF is (1~2):(25~30), and the area of ​​the nickel foam NF is 2cm×4cm.

[0010] Preferably, the hydrothermal reaction temperature in step (1) is 150~200 ℃; the hydrothermal reaction time is 10~20 hours.

[0011] Preferably, the concentration c of the Bi(NO3)3·5H2O solution in step (2) is 0 < c ≤ 0.05 mol / L.

[0012] Preferably, the continuous reaction temperature in step (2) is 25~100 ℃; the continuous reaction time is 5~15 hours.

[0013] Preferably, in step (3), the potential range is (-0.2-0.8) V, and the preferred number of CV cycles is 1 to 100.

[0014] The present invention also provides Bi prepared by the above method. y @CoOOH / NF composite material.

[0015] The present invention also provides the above-mentioned Bi y Application of @CoOOH / NF composite material in electrocatalytic water splitting.

[0016] The core of the technical solution of this invention lies in constructing a novel Bi y @CoOOH / NF composite self-supporting electrode. Employing a rapid electrochemical surface reconstruction method, by precisely controlling parameters such as voltage and scan cycles, the following were simultaneously achieved: converting the precursor into a highly active CoOOH support; introducing and precisely controlling the concentration of oxygen vacancies in situ within the CoOOH lattice; using the generated oxygen vacancies as anchoring sites to induce the precipitation of bismuth species originally present in the MOF and stabilize them into active centers of a specific size, adjustable from single atoms to quantum dots, ultimately constructing a structurally robust BiOOH / NF composite self-supporting electrode. y The @CoOOH heterostructure induces strong metal-support interactions at its interface. This interaction is key to improving catalytic performance, as it significantly optimizes interfacial charge transport efficiency and reaction kinetics.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention can controllably prepare Bi y @CoOOH / NF composite self-supporting electrode. By controlling a single electrochemical parameter, the oxygen vacancy concentration and the directional induction of bismuth species size (from single atom to quantum dot) are simultaneously achieved during the surface reconstruction process. This effectively overcomes the problems of easy aggregation of bismuth and low density of active sites in traditional methods, and realizes the rational design and controllable construction of material structure at the atomic / nanoscale.

[0018] This invention innovatively achieves effective regulation of the strong metal-support interaction between Bi and CoOOH by synergistically controlling oxygen vacancy concentration and bismuth species size, providing a new design dimension and regulation method for optimizing the microenvironment of the active site interface and improving intrinsic catalytic activity and reaction kinetics.

[0019] The entire preparation process is mild and easy to operate, requiring no complex treatments such as high-temperature calcination, and also avoids the performance degradation problem caused by the use of binders. It provides a universal and reliable technical route for the controllable preparation of high-performance self-supporting electrodes and has good prospects for large-scale application. Attached Figure Description

[0020] Figure 1 The XRD results are for the materials prepared in Examples 6-10; Figure 2 The elemental distribution results are for the material prepared in Example 9; Figure 3 The Raman spectra of the materials prepared in Comparative Example 1 and Examples 12-15 are shown below. Figure 4 XPS spectra of the materials prepared in Comparative Example 1 and Examples 12-15; Figure 5 High-magnification transmission electron microscope images of the materials prepared in Examples 13-15, for Comparative Example 1; Figure 6 The images shown are aberration-corrected transmission electron microscope images and elemental distribution diagrams of the material prepared in Example 11. Figure 7 EPR results for the materials prepared in Comparative Example 1 and Examples 12-15; Figure 8 For Comparative Example 1, LSV curves of the materials prepared in Examples 13-15; Figure 9 For Comparative Example 1, the it curves of the materials prepared in Examples 13-15; Figure 10 EIS curves of the materials prepared in Examples 13-15, for Comparative Example 1; Figure 11 For Comparative Example 1, the Cdl results of the materials prepared in Examples 13-15; In the figure, 8-10 represent the samples prepared in Examples 8-10, respectively; 11-15 represent the samples prepared in Comparative Example 1 and Examples 12-15, respectively. Detailed Implementation

[0021] The present invention will be further described below with reference to specific embodiments, and the advantages and features of the present invention will become clearer with the description. However, the embodiments are merely exemplary and do not constitute any limitation on the scope of the present invention. Those skilled in the art should understand that modifications or substitutions can be made to the details and form of the technical solutions of the present invention without departing from the spirit and scope of the present invention, but all such modifications and substitutions fall within the protection scope of the present invention.

[0022] Example 1 A self-supporting Bi 0.122 Preparation method of @CoOOH / NF composite material: (1) Dissolve 2 mmol Co(NO3)3·6H2O in 20 mL of ethanol and 10 mL of DMF, and denote it as solution A; dissolve 1 mmol 1,4-H2BDC in 2 mL of deionized water and 30 mL of DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then transfer the mixture and NF (2cm×4cm) washed with HCl and deionized water to a PTFE-lined autoclave for reaction. React continuously at 180°C for 10 hours. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained. (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in 30 mL of Bi(NO3)3·5H2O solution (0.8 mmol / L), and then reacted continuously at 40°C for 8 hours to obtain Bi 0.51 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor; (3) The Bi obtained in step (2) 0.51 A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed for 20 cycles in 1 M KOH electrolyte within the range of 0–0.55 V (relative to Ag / AgCl) to obtain Bi0. 0.122 @CoOOH (where y represents the Bi:Co atomic ratio in the sample).

[0023] Example 2 A self-supporting Bi 0.32 Preparation method of @CoOOH / NF composite material: (1) Dissolve 2 mmol Co(NO3)3·6H2O in 20 mL of ethanol and 20 mL of DMF, and denote it as solution A; dissolve 2 mmol 1,4-H2BDC in 1 mL of deionized water and 30 mL of DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then transfer the mixture and NF (2cm×4cm) washed with HCl and deionized water to a PTFE-lined autoclave for reaction. React continuously at 130°C for 12 hours. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained. (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in 30 mL of Bi(NO3)3·5H2O solution (2 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi 1.1 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor; (3) The Bi obtained in step (2)1.1 A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed for 40 cycles in 1 M KOH electrolyte within the range of 0–0.6 V (relative to Ag / AgCl) to obtain Bi0. 0.32 @CoOOH (where y represents the Bi:Co atomic ratio in the sample).

[0024] Example 3 A self-supporting Bi 0.22 Preparation method of @CoOOH / NF composite material: (1) Dissolve 1 mmol Co(NO3)3·6H2O in 20 mL of ethanol and 10 mL of DMF, and denote it as solution A; dissolve 1 mmol 1,4-H2BDC in 1 mL of deionized water and 30 mL of DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then transfer the mixture and NF (2cm×4cm) washed with HCl and deionized water to a PTFE-lined autoclave for reaction. React continuously at 180°C for 12 hours. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained. (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in 30 mL of Bi(NO3)3·5H2O solution (5 mmol / L), and then reacted continuously at 80°C for 10 hours to obtain Bi 1.5 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor; (3) The Bi obtained in step (2) 1.5 A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed for 60 cycles in 1 M KOH electrolyte within the range of 0–0.8 V (relative to Ag / AgCl) to obtain Bi0. 0.22 @CoOOH (where y represents the Bi:Co atomic ratio in the sample).

[0025] Example 4 A self-supporting Bi 0.086 Preparation method of @CoOOH / NF composite material: (1) Dissolve 1 mmol Co(NO3)3·6H2O in 20 mL of ethanol and 10 mL of DMF, and denote it as solution A; dissolve 1 mmol 1,4-H2BDC in 1 mL of deionized water and 30 mL of DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then transfer the mixture and NF (2cm×4cm) washed with HCl and deionized water to a PTFE-lined autoclave for reaction. React continuously at 150°C for 12 hours. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained. (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in 30 mL of Bi(NO3)3·5H2O solution (0.5 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi 0.4 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor; (3) The Bi obtained in step (2) 0.4 A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed for 40 cycles in 1 M KOH electrolyte within the range of 0–0.6 V (relative to Ag / AgCl) to obtain Bi0. 0.086 @CoOOH (where y represents the Bi:Co atomic ratio in the sample).

[0026] Example 5 A self-supporting Bi y Preparation method of @CoOOH / NF composite material: (1) Dissolve 1 mmol Co(NO3)3·6H2O in 20 mL of ethanol and 10 mL of DMF, and denote it as solution A; dissolve 1 mmol 1,4-H2BDC in 1 mL of deionized water and 30 mL of DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then transfer the mixture and NF (2cm×4cm) washed with HCl and deionized water to a PTFE-lined autoclave for reaction. React continuously at 170°C for 12 hours. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained. (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in 30 mL of Bi(NO3)3·5H2O solution (0.5 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi x @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor; (3) The Bi obtained in step (2)x A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed for 60 cycles in 1 M KOH electrolyte within the range of 0–0.6 V (relative to Ag / AgCl) to obtain Bi0. y @CoOOH (where y represents the Bi:Co atomic ratio in the sample).

[0027] Example 6 This embodiment describes the synthesis of a Co-MOF / NF catalyst according to the following steps: (1) Dissolve 1 mmol Co(NO3)3·6H2O in 20 mL of ethanol and 10 mL of DMF, and record it as solution A; dissolve 1 mmol 1,4-H2BDC in 1 mL of deionized water and 30 mL of DMF, and record it as solution B; mix solutions A and B thoroughly and stir, and then transfer the mixture and NF (2cm×4cm) washed with HCl and deionized water to a PTFE-lined autoclave for reaction. React continuously at 150°C for 12 hours. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained, and recorded as sample 6.

[0028] Example 7 This embodiment describes the synthesis of Bi according to the following steps. 0.02 @Co-MOF / NF catalyst: (1) Sample 6 prepared in Example 6 was immersed in 30 mL of Bi(NO3)3·5H2O solution (0.2 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi 0.02 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor, denoted as sample 7.

[0029] Example 8 This embodiment describes the synthesis of Bi according to the following steps. 0.4 @Co-MOF / NF catalyst: (1) Sample 6 prepared in Example 6 was immersed in 30 mL of Bi(NO3)3·5H2O solution (0.5 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi. 0.4 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor, denoted as sample 8.

[0030] Example 9 This embodiment describes the synthesis of Bi according to the following steps. 1.1 @Co-MOF / NF catalyst: (1) Sample 6 prepared in Example 6 was immersed in 30 mL of Bi(NO3)3·5H2O solution (2 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi 1.1 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor, denoted as sample 9.

[0031] Example 10 This embodiment describes the synthesis of Bi according to the following steps. 1.4 @Co-MOF / NF catalyst: (1) Sample 6 prepared in Example 6 was immersed in 30 mL of Bi(NO3)3·5H2O solution (5 mmol / L), and then reacted continuously at 60°C for 10 hours to obtain Bi 1.4 @Co-MOF / NF (where x represents the Bi:Co atomic ratio in the sample) precursor, denoted as sample 10.

[0032] Comparative Example 1 This embodiment describes the synthesis of the CoOOH / NF catalyst according to the following steps: (1) Using sample 6 prepared in Example 6 as the working electrode, graphite rod as the counter electrode, and Ag / AgCl electrode as the reference electrode, a three-electrode system was constructed. In 1 M KOH electrolyte, cyclic voltammetry (CV) was performed for 60 cycles in the range of 0-0.6 V (relative to Ag / AgCl) to obtain CoOOH, which was denoted as sample 11.

[0033] Example 12 This embodiment describes the synthesis of Bi according to the following steps. 0.01 @CoOOH / NF catalyst: (1) Using sample 7 prepared in Example 7 as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a three-electrode system was constructed. Cyclic voltammetry (CV) was performed for 60 cycles in 1 M KOH electrolyte within the range of 0-0.6 V (relative to Ag / AgCl) to obtain Bi. 0.01 @CoOOH (where y represents the Bi:Co atomic ratio in the sample), denoted as sample 12.

[0034] Example 13 This embodiment describes the synthesis of Bi according to the following steps. 0.1 @CoOOH / NF catalyst: (1) Using sample 8 prepared in Example 8 as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a three-electrode system was constructed. Cyclic voltammetry (CV) was performed for 60 cycles in 1 M KOH electrolyte within the range of 0-0.6 V (relative to Ag / AgCl) to obtain Bi. 0.1 @CoOOH (where y represents the Bi:Co atomic ratio in the sample), denoted as sample 13.

[0035] Example 14 This embodiment describes the synthesis of Bi according to the following steps. 0.2 @CoOOH / NF catalyst: (1) Using sample 10 prepared in Example 10 as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a three-electrode system was constructed. Cyclic voltammetry (CV) was performed for 60 cycles in 1 M KOH electrolyte within the range of 0-0.6 V (relative to Ag / AgCl) to obtain Bi. 0.2 @CoOOH (where y represents the Bi:Co atomic ratio in the sample), denoted as sample 14.

[0036] Example 15 This embodiment describes the synthesis of Bi according to the following steps. 0.4 @CoOOH / NF catalyst: (1) Using sample 9 prepared in Example 9 as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode, a three-electrode system was constructed. Cyclic voltammetry (CV) was performed for 60 cycles in 1 M KOH electrolyte within the range of 0-0.6 V (relative to Ag / AgCl) to obtain Bi. 0.4 @CoOOH (where y represents the Bi:Co atomic ratio in the sample), denoted as sample 15.

[0037] Experimental Example 1 The products of Examples 6-10, Comparative Example 1, and Examples 12-15 were tested respectively.

[0038] Depend on Figure 1 It can be seen that the XRD results of the sample prepared in Example 6 show characteristic diffraction peaks of the Co-MOF phase, indicating that the main component of the sample prepared in Example 6 is Co-MOF. Furthermore, the XRD results of the samples prepared in Examples 7-10 show characteristic diffraction peaks of both the Co-MOF and Bi phases, indicating that the main components of the samples prepared in Examples 7-10 are Co-MOF and Bi.

[0039] Depend on Figure 2 It can be seen that the sample prepared in Example 9 includes Co, Bi, C and O elements.

[0040] Depend on Figure 3 It can be seen that the samples prepared in Comparative Example 1 and Examples 12-15 show characteristic peaks of CoOOH, proving that Bi x The @Co-MOF / NF precursor is transformed into a highly active CoOOH support after electrochemical surface reconstruction treatment.

[0041] Depend on Figure 4 The results show that the sample prepared in Comparative Example 1 contains Co, C, and O elements, and the samples prepared in Examples 12-15 contain Co, Bi, C, and O elements, proving that the element types of the samples did not change after reconstruction.

[0042] Depend on Figure 5 The results showed that no particles appeared in the sample prepared in Comparative Example 1, while particles of different sizes appeared in the samples prepared in Examples 13-15, with particle sizes of 2.9 nm (Bi). 0.1 @CoOOH), 3.4 nm (Bi 0.4 @CoOOH), and 4.0 nm (Bi 0.2 @CoOOH). This demonstrates that the directional induction of bismuth species size was achieved during the surface reconstruction process, effectively overcoming the difficulties of bismuth element agglomeration and low active site density in traditional methods.

[0043] Depend on Figure 6 It can be seen that the sample prepared in Example 11 contains Bi single atoms, proving that this method can achieve atomic-level size control of bismuth species.

[0044] Depend on Figure 7 It can be seen that the samples prepared in Comparative Example 1 and Examples 12-15 have different numbers of oxygen vacancy defects. The lowest signal intensity was observed in Bi0.4@CoOOH, and the Ov signal initially weakened and then strengthened with the increase of bismuth concentration. This demonstrates that the loading of Bi-QD is negatively proportional to the Ov concentration, indicating that this method can introduce and precisely control the concentration of oxygen vacancies in situ in the CoOOH lattice. By using the generated oxygen vacancies as anchoring sites, bismuth species originally present in the MOF are precipitated and stably formed into active centers of a specific size, ultimately constructing a structurally stable Bi0.4@CoOOH. y @CoOOH heterostructures, and induce strong metal-support interactions at their interfaces.

[0045] Experimental Example 2 The electrocatalytic performance of the catalyst was tested using a standard three-electrode system. The working electrode was a sample grown on a nickel foam substrate, the counter electrode was a graphite rod, and the reference electrode was an Ag / AgCl electrode. The electrolyte was 1 mkOH. Before testing, the working electrode was activated by cyclic voltammetry (CV) within a potential window of 1.0–1.60 V (vs. RHE) until the curve stabilized. Subsequently, linear sweep voltammetry (LSV) was performed at a scan rate of 5 mV / s within the same potential range, and the LSV curve was recorded. The stability of the catalyst was evaluated using chronopotentiometry, i.e., at 25 mA cm⁻¹. -2 It was continuously operated at a constant current density. Electrochemical impedance spectroscopy (EIS) measurements were performed at open-circuit potentials, ranging from 100 kHz to 0.01 Hz, with a perturbation amplitude of 5 mV. All measured potentials were converted to potentials relative to the reversible hydrogen electrode.

[0046] Depend on Figure 8 It can be seen that, under the same current density, the overpotential of Example 15 is much lower than that of the samples prepared in Comparative Example 1 and Examples 13 and 14. This demonstrates that Bi... 0.4 @CoOOH exhibits strong metal-support interactions, thus enhancing the electrocatalytic OER performance of the material.

[0047] Depend on Figure 9 It can be seen that the diameter of the semicircle in the Nyquist plot of Example 15 is smaller than the diameter of the semicircle of the samples prepared in Comparative Examples 1, 13, and 14, indicating that Bi 0.4 @CoOOH exhibits the best charge transfer capability, demonstrating that the strong metal-support interaction formed between Bi and CoOOH significantly reduces charge transport resistance and promotes interfacial charge transfer, thereby greatly improving the material's electronic conductivity and overall reaction kinetics.

[0048] Depend on Figure 10 It can be seen that the sample prepared in Example 15 has a performance of 25 mA cm⁻¹ -2 The relatively stable current value at the given current density proves that Bi 0.4 @CoOOH exhibits good stability.

[0049] Depend on Figure 11 It can be seen that the C of the samples prepared in Example 15 and Comparative Examples 1, 13, and 14 dl The values ​​were 258.2, 39.3, 230.6, and 106.2 mF / cm, respectively. -2 This indicates that Bi 0.4 @CoOOH exhibits the optimal active surface area, demonstrating that strong metal-support interactions can optimize electronic structure and induce the generation of new active sites.

Claims

1. A self-supporting Bi y The method for preparing @CoOOH / NF composite material is characterized by, The preparation method includes the following steps: (1) Dissolve Co(NO3)3·6H2O in ethanol and DMF, and denote it as solution A; dissolve 1,4-H2BDC in deionized water and DMF, and denote it as solution B; mix solutions A and B thoroughly and stir, and then carry out hydrothermal reaction with the mixture and the foamed nickel NF after washing with HCl and deionized water. After washing and drying with DMF, deionized water and ethanol, Co-MOF / NF is obtained. (2) Subsequently, the Co-MOF / NF prepared in step (1) was immersed in Bi(NO3)3·5H2O solution, and then reacted continuously to obtain Bi. x @Co-MOF / NF precursor, where x represents the Bi:Co atomic ratio in the sample; (3) The Bi obtained in step (2) x A three-electrode system was constructed using a Co-MOF / NF electrode as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Cyclic voltammetry (CV) was performed in 1 M KOH electrolyte within a potential range relative to Ag / AgCl to obtain self-supporting Bi2. y @CoOOH composite material, where y represents the Bi:Co atomic ratio in the sample.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of Co(NO3)2·6H2O to 1,4-H2BDC is (0.8~2):(0.8~2); the concentration of Co(NO3)2·6H2O after dissolving in ethanol and DMF solution is 0.01-0.05 mol / L.

3. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of ethanol to DMF in solution A is (1~2):(1~2).

4. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of deionized water to DMF in solution B is (1~2):(25~30); the area of ​​the nickel foam NF is 2cm×4cm.

5. The preparation method according to claim 1, characterized in that, In step (1), the hydrothermal reaction temperature is 150~200 ℃; the hydrothermal reaction time is 10~20 hours.

6. The preparation method according to claim 1, characterized in that, In step (2), the concentration c of the Bi(NO3)3·5H2O solution is 0 < c ≤ 0.05 mol / L.

7. The preparation method according to claim 1, characterized in that, In step (2), the continuous reaction temperature is 25~100 ℃; the continuous reaction time is 5~15 hours.

8. The preparation method according to claim 1, characterized in that, In step (3), the potential range is (-0.2-0.8) V; the number of CV cycles is 1~100.

9. Bi obtained by the preparation method according to any one of claims 1-8 y @CoOOH / NF composite material.

10. The Bi as described in claim 9 y Application of @CoOOH / NF composite material in electrocatalytic water splitting.

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