Ta-Co-MOF-P / NF composite material and preparation method and application thereof

Abstract

The invention belongs to the technical field of electro-catalytic water decomposition, and relates to a preparation method and application of a Ta-Co-MOF-P / NF composite material under the combined action of a built-in electric field and an asymmetric bridge oxygen bond. The method comprises the following steps: firstly, performing one-step solvothermal synthesis on a foamed nickel carrier to obtain a bimetal Ta-Co-MOF / NF precursor, and then performing low-temperature phosphating treatment to construct a Co-MOF and CoP heterogeneous interface on a substrate. And a built-in electric field formed by regulating and controlling the phosphorization degree and a Co-O-Ta asymmetric bridge oxygen bond formed by a proper Ta doping amount jointly change the water molecule configuration so as to improve the water decomposition activity. The catalyst can enhance the interaction force with water molecules, and the proportion of free water in the surface water molecule configuration is increased, so that active hydrogen species are easier to dissociate and release, thereby accelerating the alkaline HER reaction kinetics and mass transfer process. The material shows excellent HER catalytic activity and long-term stability in an alkaline environment.

Description

Technical Field

[0001] This invention belongs to the field of electrocatalytic water splitting technology, specifically relating to a Ta-Co-MOF-P / NF composite material for efficient hydrogen evolution reaction, its preparation method, and its application. Background Technology

[0002] Hydrogen energy, as a clean and renewable energy carrier, is key to achieving carbon neutrality. Electrocatalytic water splitting for hydrogen production is one of the most promising green hydrogen production technologies. However, the kinetics of the hydrogen evolution reaction in alkaline media are slow, severely limiting the overall energy conversion efficiency. Therefore, developing efficient, stable, and low-cost alkaline HER electrocatalysts is crucial.

[0003] Metal-organic frameworks (MOFs) have shown great potential in electrocatalysis due to their high specific surface area and tunable pore structure. Among them, cobalt-based MOFs are considered as promising candidates to replace noble metal Pt catalysts. However, intrinsic MOFs have poor electrical conductivity and limited adsorption-desorption capacity for water molecules, resulting in unsatisfactory HER activity and stability.

[0004] Currently, introducing a built-in electric field through heterojunction construction to promote charge transport, or modulating the electronic structure through metal doping, are effective strategies for improving catalyst performance. However, how to synergistically control the electronic structure and interfacial chemical environment of materials through simple preparation processes, thereby simultaneously optimizing the adsorption configuration of water molecules and the adsorption-desorption energy of hydrogen species, remains a challenge in this field. Summary of the Invention

[0005] To address the aforementioned bottlenecks, this invention proposes a synergistic performance enhancement strategy on a three-dimensional nickel foam substrate by inducing a built-in electric field through a heterogeneous interface and employing a metal doping approach. This strategy utilizes the degree of phosphating to create a Co-MOF / CoP heterogeneous interface, constructing a built-in electric field that effectively promotes electron transfer, improves reaction pathways, and alters the configuration of water molecules at the interface. Furthermore, adjusting the tantalum doping amount optimizes the interface water molecule configuration through Co-O-Ta asymmetric bridging oxygen bonds, thereby enhancing the kinetics of the alkaline HER reaction. The altered interface water molecule configuration generates more free water, continuously providing sufficient protons to the interface during the HER process. Simultaneously, water molecules are brought closer to the catalyst surface, strengthening the interaction between water molecules and the catalyst, which helps improve the activation efficiency of water molecules and accelerates the HER process. Therefore, developing a dual-strategy synergistic method to disrupt the order of the water network is an urgent need and a feasible solution for developing alkaline water electrolysis for hydrogen production.

[0006] This invention provides a Ta-Co-MOF-P / NF composite material, its preparation method, and its application in electrocatalytic water splitting. This catalyst, by constructing a heterogeneous interface, induces a built-in electric field and modulates the tantalum doping amount to form Co-O-Ta asymmetric bridging oxygen bonds, exhibiting significantly enhanced hydrogen evolution reaction activity and stability in an alkaline environment.

[0007] The core of this invention lies in adjusting the degree of phosphating. Leveraging the band structure difference between Co-MOF and CoP, a significant built-in electric field is induced at the heterojunction interface. Simultaneously, rare-earth metal doping forms Co-O-Ta asymmetric bridging oxygen bonds, jointly optimizing the water molecule configuration. This invention achieves effective control of the interfacial electric field by regulating the degree of phosphating. Compared to a single metal doping strategy, the Co-MOF and CoP heterojunction prepared by this invention exhibits significantly improved overall performance in alkaline environments: not only lower overpotential and higher current density, but also excellent long-term stability. Furthermore, compared to single-component phosphide catalysts, the Co-O-Ta asymmetric bridging oxygen bonds induced by this invention also exhibit significantly improved overall performance in alkaline environments. The preparation process employed in this invention has advantages such as mild reaction conditions, simple operation, and good reproducibility, providing a reliable material basis for advancing the practical application of alkaline water electrolysis for hydrogen production.

[0008] To achieve the above-mentioned objective, this invention provides a method for preparing Ta-Co-MOF-P / NF composite materials, comprising the following steps: (1) Dissolve Co(NO3)2·6H2O and TaCl5 in a mixed solution of NN dimethylformamide (DMF), deionized water and ethanol (EtOH) to form solution A; dissolve terephthalic acid (PTA) in the same mixed solution of NN dimethylformamide (DMF), deionized water and ethanol (EtOH) and denote it as solution B; immerse the pretreated nickel foam (NF) in solution B and continue stirring; after mixing and stirring solutions A and B, transfer them to a stainless steel reactor lined with polytetrafluoroethylene and react in a high-temperature drying oven; after naturally cooling to room temperature, wash NF repeatedly with DMF and ethanol, and dry with cold air to obtain the precursor Ta-Co-MOF / NF.

[0009] (2) The Ta-Co-MOF / NF and NaH2PO2·H2O obtained in step (1) are placed in two porcelain boats in a tube furnace, heat-treated under a nitrogen atmosphere and naturally cooled to room temperature to obtain Ta-Co-MOF-P / NF.

[0010] Preferably, in step (1), the molar ratio of ligand to metal salt is 1:1.

[0011] Preferably, in step (1), the molar ratio of Co(NO3)2·6H2O to TaCl5 is (0.9~0.995):(0.005~0.1).

[0012] Preferably, in step (1), the volume ratio of DMF, deionized water and EtOH is 16:1:1, and the amount of deionized water is 2 mL.

[0013] Preferably, in step (1), the reaction time in the reactor in the high-temperature drying oven is 10~12 h and the temperature is 120~150 ℃.

[0014] Preferably, in step (2), for 2×2 cm 2 Ta-Co-MOF / NF is subjected to low-temperature phosphating treatment, and the amount of phosphorus source (NaH2PO2·H2O) is controlled from 0.3 to 0.8 g, which can achieve controllable doping of P and precise structural control.

[0015] Preferably, in step (2), the heat treatment temperature is 300~350 ℃.

[0016] Preferably, in step (2), the heat treatment time is 1 to 2 hours.

[0017] The present invention also provides a Ta-Co-MOF-P / NF composite material prepared by the above method.

[0018] The present invention also provides the application of the above-mentioned Ta-Co-MOF-P / NF composite material in electrocatalytic water splitting.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention enables the formation of a Ta-Co-MOF-P / NF composite material with the combined effect of a built-in electric field and asymmetric bridging oxygen bonds. Through a simple one-step solvothermal and low-temperature phosphating method, the Co-MOF and CoP heterostructure interface induces a built-in electric field, and tantalum doping forms Co-O-Ta bridging oxygen bonds, effectively promoting the directional migration of interfacial charges, optimizing the water molecule configuration, and enabling the catalyst to exhibit excellent electrocatalytic HER activity and long-term operational stability in an alkaline environment.

[0020] This invention innovatively achieves controllable adjustment of the built-in electric field, asymmetric bridging oxygen bonds, and improved interfacial water molecule configuration by regulating the degree of phosphating and the amount of tantalum doping. This provides a new dimension of regulation for optimizing the interfacial electronic structure and breaking the orderliness of the interfacial water network. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The XRD results are for the materials prepared in Example 2 and Comparative Examples 1 and 2. Figure 2 These are scanning electron microscope images of the material prepared in Example 2; Figure 3 Here are high-magnification transmission electron microscope images and elemental distribution maps of the material prepared in Example 2; Figure 4 The images shown are processed Tauc plots of the UV-Vis diffuse reflectance absorption spectra of the materials prepared in Example 2 and Comparative Examples 1 and 2. Figure 5 XPS valence band spectra of the materials prepared in Example 2 and Comparative Examples 1 and 2; Figure 6 The Zeta results are for the materials prepared in Examples 2, 5-7 and Comparative Example 1; Figure 7 The Raman spectra of the materials prepared in Example 2 and Comparative Examples 1 and 2 are shown. Figure 8 The contact angle test results are for the materials prepared in Example 2 and Comparative Examples 1 and 2; Figure 9 The LSV curves are for the materials prepared in Examples 2, 1, 3, 4, 5, 6, 7 and Comparative Examples 1 and 2. Figure 10 The it curve is the curve of the material prepared in Example 2; Figure 11 C is the material prepared in Example 2 and Comparative Examples 1 and 2. dl result; Figure 12 EIS curves of the materials prepared in Example 2 and Comparative Examples 1 and 2; Figure 13 Tafel slope diagrams of the materials prepared in Example 2 and Comparative Examples 1 and 2; In the figure, 1, 2, 3, 4, 5, 6, 7, 9, and 10 represent the samples prepared in Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, Comparative Example 1, and Comparative Example 2, respectively. Detailed Implementation

[0022] 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.

[0023] Example 1 This embodiment synthesizes a 0.5% Ta-Co-MOF-0.5P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.995 mmol Co(NO3)2·6H2O and 0.005 mmol TaCl5 in a mixture of 32 mL N,N-dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Separately, 1 mmol terephthalic acid (PTA) was added to the above mixture and stirred until homogeneous to obtain solution B. Pretreated nickel foam (NF) was then immersed in solution B and stirred continuously. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 0.5% Ta-Co-MOF / NF.

[0024] (2) Using the 0.5% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2 The 0.5% Ta-Co-MOF / NF sample and 0.5 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 0.5% Ta-Co-MOF-0.5P / NF (referred to as sample 1).

[0025] Example 2 This embodiment synthesizes a 1% Ta-Co-MOF-0.5P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.99 mmol Co(NO3)2·6H2O and 0.01 mmol TaCl5 in a mixture of 32 mL NN dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by adding 1 mmol terephthalic acid (PTA) to the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 1% Ta-Co-MOF / NF.

[0026] (2) Using the 1% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2 The 1% Ta-Co-MOF / NF sample and 0.5 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 1% Ta-Co-MOF-0.5P / NF (referred to as sample 2).

[0027] Example 3 This embodiment synthesizes a 2% Ta-Co-MOF-0.5P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.98 mmol Co(NO3)2·6H2O and 0.02 mmol TaCl5 in a mixture of 32 mL NN dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 2% Ta-Co-MOF / NF.

[0028] (2) Using the 2% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2The 2% Ta-Co-MOF / NF sample and 0.5 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 2% Ta-Co-MOF-0.5P / NF (referred to as sample 3).

[0029] Example 4 This embodiment synthesizes a 10% Ta-Co-MOF-0.5P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.9 mmol Co(NO3)2·6H2O and 0.1 mmol TaCl5 in a mixture of 32 mL N,N dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 10% Ta-Co-MOF / NF.

[0030] (2) Using the 10% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2 The 10% Ta-Co-MOF / NF sample and 0.5 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 10% Ta-Co-MOF-0.5P / NF (referred to as sample 4).

[0031] Example 5 This embodiment synthesizes a 1% Ta-Co-MOF-0.3P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.99 mmol Co(NO3)2·6H2O and 0.01 mmol TaCl5 in a mixture of 32 mL NN dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 1% Ta-Co-MOF / NF.

[0032] (2) Using the 1% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2 The 1% Ta-Co-MOF / NF sample and 0.3 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 1% Ta-Co-MOF-0.3P / NF (referred to as sample 5).

[0033] Example 6 This embodiment synthesizes a 1% Ta-Co-MOF-0.6P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.99 mmol Co(NO3)2·6H2O and 0.01 mmol TaCl5 in a mixture of 32 mL NN dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 1% Ta-Co-MOF / NF.

[0034] (2) Using the 1% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2The 1% Ta-Co-MOF / NF sample and 0.6 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 1% Ta-Co-MOF-0.6P / NF (referred to as sample 6).

[0035] Example 7 This embodiment synthesizes a 1% Ta-Co-MOF-0.8P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.99 mmol Co(NO3)2·6H2O and 0.01 mmol TaCl5 in a mixture of 32 mL NN dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 1% Ta-Co-MOF / NF.

[0036] (2) Using the 1% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2 The 1% Ta-Co-MOF / NF sample and 0.8 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into 1% Ta-Co-MOF-0.8P / NF (referred to as sample 7).

[0037] Example 8 This embodiment synthesizes a 1% Ta-Co-MOF-0.5P / NF heterojunction catalyst according to the following steps: (1) Solution A was prepared by dissolving 0.99 mmol Co(NO3)2·6H2O and 0.01 mmol TaCl5 in a mixture of 32 mL NN dimethylformamide (DMF), 2 mL deionized water and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. The pretreated nickel foam (NF) was then immersed in solution B and stirred. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven at 130 °C for 10 h. After naturally cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 1% Ta-Co-MOF / NF.

[0038] (2) Using the 1% Ta-Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment, and a 2×2 cm 2 The 1% Ta-Co-MOF / NF sample and 0.5 g NaH2PO2·H2O were placed in two porcelain boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 320 °C at 2 °C / min for 1 h and then naturally cooled to room temperature, eventually transforming into 1% Ta-Co-MOF-0.5P / NF (referred to as sample 8).

[0039] Comparative Example 1 This comparative example synthesizes a 1% Ta-Co-MOF / NF catalyst according to the following steps: Solution A was prepared by dissolving 0.99 mmol Co(NO3)2·6H2O and 0.01 mmol TaCl5 in a mixture of 32 mL N,N dimethylformamide (DMF), 2 mL deionized water, and 2 mL ethanol (EtOH). Solution B was prepared by dissolving 1 mmol terephthalic acid (PTA) in the same mixture and stirring until homogeneous. Pretreated nickel foam (NF) was then immersed in solution B and stirred continuously. After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene (PTFE) and reacted in a high-temperature drying oven at 150 °C for 12 h. After natural cooling to room temperature, the NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor 1% Ta-Co-MOF / NF (sample 9).

[0040] Comparative Example 2 This comparative example synthesizes a Co-MOF-0.5P / NF heterojunction catalyst according to the following steps: (1) Dissolve 1 mmol Co(NO3)2·6H2O in a mixed solution of 32 mL NN dimethylformamide (DMF), 2 mL deionized water, and 2 mL ethanol (EtOH) to form solution A. Separately, dissolve 1 mmol terephthalic acid (PTA) in the same mixed solution and stir until homogeneous, and denote this as solution B. Immerse the pretreated nickel foam (NF) in solution B and continue stirring. After mixing and stirring solutions A and B, transfer them to a stainless steel reactor lined with polytetrafluoroethylene and react in a high-temperature drying oven at 150 °C for 12 h. After naturally cooling to room temperature, wash the NF repeatedly with DMF and ethanol, and dry with cold air to obtain the precursor Co-MOF / NF.

[0041] (2) Using the Co-MOF / NF obtained in step (1) as a precursor, the nickel foam sample was subjected to low-temperature phosphating treatment. A 2×2cm... 2 The Co-MOF / NF sample and 0.5 g NaH2PO2·H2O were placed in two ceramic boats in a tube furnace. Under a nitrogen atmosphere, the temperature was increased to 350 °C at 2 °C / min for 2 h and then naturally cooled to room temperature, eventually transforming into Co-MOF-0.5P / NF (referred to as sample 10).

[0042] The products of Example 2 and Comparative Examples 1 and 2 were tested respectively.

[0043] Depend on Figure 1 It can be seen that the XRD results of the sample prepared in Example 2 show characteristic diffraction peaks of Co-MOF and CoP, indicating that the main components of the sample prepared in Example 2 are Co-MOF and CoP.

[0044] Depend on Figure 2 It can be seen that the morphology of the sample prepared in Example 2 is basically a two-dimensional sheet structure loaded on the substrate.

[0045] Depend on Figure 3 It can be seen that the sample prepared in Example 2 contains Co, P and Ta elements, proving that Ta and P elements were successfully doped into the material.

[0046] Depend on Figure 4 The results showed that the band gaps of the samples prepared in Example 2 and Comparative Examples 1 and 2 were 1.94 eV, 2.37 eV and 2.29 eV, respectively.

[0047] Depend on Figure 5 The results show that the conduction band values ​​of the samples prepared in Example 2 and Comparative Examples 1 and 2 are 1.56 eV, 1.78 eV, and 1.71 eV, respectively. Combined with... Figure 4 The results demonstrate that a built-in electric field exists in 1%Ta-Co-MOF-0.5P / NF.

[0048] Depend on Figure 6 It can be seen that the Zeta potentials of the samples prepared in Examples 2 and 5-7 and Comparative Example 1 are -17.43, -13.39, -14.87, -16.3 and -8.5 mV, respectively. The results show that the built-in electric field of 1%Ta-Co-MOF-0.5P / NF is the strongest.

[0049] Depend on Figure 7 It can be seen that there are differences in the Raman peaks of the samples prepared in Example 2 and Comparative Examples 1 and 2. The results prove that there are Co-O-Ta asymmetric bridging oxygen bonds in 1%Ta-Co-MOF-0.5P / NF.

[0050] Depend on Figure 8 The test results show that the contact angles prepared in Example 2 and Comparative Examples 1 and 2 are 20°, 80° and 56°, respectively. The results prove that 1%Ta-Co-MOF-0.5P / NF has better hydrophilicity.

[0051] The electrocatalytic performance of the catalyst was tested using a standard three-electrode system. The sample grown on a nickel foam substrate was used as the working electrode, a graphite rod as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte was a 1 M KOH solution. Before testing, the working electrode was activated by cyclic voltammetry (CV) within a potential window of 0.124–0.376 V (vs. RHE) until the curve stabilized. Subsequently, linear sweep voltammetry (LSV) was performed within the same potential range at a scan rate of 5 mV / s, and the LSV curve was recorded. The stability of the catalyst was evaluated using a chronopotentiometric method, i.e., at 100 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.

[0052] Depend on Figure 9 It can be seen that, under the same current density, the overpotential of Example 2 is much lower than that of the samples prepared in Examples 1, 3, 4, 5, 6, 7 and Comparative Examples 1 and 2. This proves that the built-in electric field generated by the Co-MOF and CoP composite and the Co-O-Ta asymmetric bridging oxygen bond in Example 2 enhance the electrocatalytic HER performance of the material, resulting in the best electrocatalytic HER performance.

[0053] Depend on Figure 10 It can be seen that the sample prepared in Example 2 has a performance of 100 mA cm⁻¹ -2 The relatively stable current value at the given current density demonstrates that 1%Ta-Co-MOF-0.5P / NF has good stability.

[0054] Depend on Figure 11 It can be seen that the C of the samples prepared in Example 2 and Comparative Examples 1-2 dl The values ​​were 19.3, 7.9, and 16.1 mF cm, respectively. -2 This indicates that 1%Ta-Co-MOF-0.5P / NF has the optimal active specific surface area. Characterization results confirm that the number of active sites in 1%Ta-Co-MOF-0.5P / NF is significantly increased, which can be attributed to the built-in electric field of Co-MOF and Co-P, the optimization of electronic structure by the Co-O-Ta asymmetric bridging oxygen bond, and the induction effect of new active sites.

[0055] Depend on Figure 12 It can be seen that the diameter of the semicircle in the Nyquist plot of Example 2 is smaller than the diameter of the semicircle of the sample prepared in Comparative Examples 1-2, indicating that 1%Ta-Co-MOF-0.5P / NF has the best charge transfer capability. This proves that the Co-O-Ta asymmetric structure creates unique "cooperative active sites" through electronic interactions, and the built-in electric field formed by the heterogeneous interface effectively reduces the charge transfer impedance, accelerates the interface charge migration process, and significantly improves the electronic conduction efficiency and overall reaction kinetics performance of the material.

[0056] Depend on Figure 13 It can be seen that the Tafel slopes of the samples prepared in Example 2 and Comparative Examples 1-2 are -84.8, -132.0, and -108.3 mV, respectively. This indicates that the sample prepared in Example 2 has a more efficient reaction mechanism. This is attributed to the built-in electric field solving the charge supply bottleneck in the reaction process, and the asymmetric bridging oxygen bond solving the adsorption and desorption bottleneck of the hydrogen intermediate by fine-tuning the electronic state of the active center. This dual approach optimizes the key energy barriers in the reaction pathway.

Claims

1. A method for preparing a Ta-Co-MOF-P / NF heterojunction composite material, characterized in that, Includes the following steps: (1) Dissolve the metal salts Co(NO3)2·6H2O and TaCl5 in a mixed solution of N,N dimethylformamide, deionized water and ethanol to form solution A; The ligand terephthalic acid was dissolved in the same mixed solution, denoted as solution B; the pretreated nickel foam was immersed in solution B and stirred continuously; After mixing and stirring solutions A and B, the mixture was transferred to a stainless steel reactor lined with polytetrafluoroethylene and reacted in a high-temperature drying oven. After naturally cooling to room temperature, NF was repeatedly washed with DMF and ethanol and dried with cold air to obtain the precursor Ta-Co-MOF / NF. (2) The Ta-Co-MOF / NF and NaH2PO2·H2O obtained in step (1) are placed in two porcelain boats in a tube furnace, heat-treated under a nitrogen atmosphere and naturally cooled to room temperature to obtain Ta-Co-MOF-P / NF.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of ligand to metal salt is 1:

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of Co(NO3)2·6H2O and TaCl5 is (0.9~0.995):(0.005~0.1).

4. The preparation method according to claim 1, characterized in that, In step (1), the volume ratio of DMF, deionized water and EtOH solvent is 16:1:1, and the amount of deionized water is 2 mL.

5. The preparation method according to claim 1, characterized in that, In step (1), the reaction time in the reactor in the high-temperature drying oven is 10-12 h, and the temperature is 120-150 ℃.

6. The preparation method according to claim 1, characterized in that, In step (2), the 2×2 cm 2 Ta-Co-MOF / NF was subjected to low-temperature phosphating treatment, and the amount of phosphorus source NaH2PO2·H2O was adjusted to 0.3~0.8 g.

7. The preparation method according to claim 1, characterized in that, The heat treatment temperature in step (2) is 300~350 ℃.

8. The preparation method according to claim 1, characterized in that, The heat treatment time in step (2) is 1 to 2 hours.

9. The Ta-Co-MOF-P / NF composite material prepared by the preparation method according to any one of claims 1-8.

10. The application of the Ta-Co-MOF-P / NF composite material according to claim 9 in electrocatalytic water splitting.

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