NF-loaded high-valence metal doped-high-entropy layered double hydroxide / MOF composite material, and preparation method and application thereof

Abstract

The invention discloses an NF-loaded high-valence metal doped-high-entropy layered double hydroxide / MOF composite material, and belongs to the technical field of high-entropy catalysts. A two-step hydrothermal method is adopted, firstly, a metal organic framework material (MOF) precursor Ni-MOF is prepared through the hydrothermal method, then a metal salt solution containing iron, zinc, cerium, cobalt and the like is prepared at the room temperature, the solution is fully stirred and subjected to ultrasonic uniformization and transferred into a high-pressure kettle, the precursor Ni-MOF is added, and the metal salt solution containing iron, zinc, cerium, cobalt and the like is obtained. And carrying out hydrothermal treatment, washing and drying to obtain the high-valence metal doped high-entropy layered double hydroxide / MOF composite material loaded on foamed nickel (NF). According to the technical scheme, due to the synergistic effect of the MOF and the high-entropy LDH, the MOF / LDHs have excellent electrochemical performance, and the introduction of the high-valence metal can regulate an electronic structure and expose rich active sites, so that the electrocatalytic activity of the MOF / LDHs is improved, and excellent HER, OER and UOR activities are obtained.

Description

Technical Field

[0001] The present application belongs to the field of high entropy electrocatalyst technology, and specifically relates to NF-supported high-valent metal-doped-high entropy layered hydroxide / MOF composite materials, preparation methods, and applications. Background Art

[0002] As a clean and efficient secondary energy carrier, hydrogen is considered a key path to achieving energy transition and carbon neutrality. Among various hydrogen production technologies, water electrolysis has attracted considerable attention due to its zero carbon emissions and high product purity. This technology electrochemically splits water to produce hydrogen (cathode hydrogen evolution reaction, HER) and oxygen (anode oxygen evolution reaction, OER).

[0003] However, large-scale hydrogen production by water electrolysis still faces significant bottlenecks: the sluggish kinetics of the anode OER reaction require overcoming a high thermodynamic overpotential of 1.23V. This results in the actual electrolysis voltage far exceeding the theoretical value (typically ≥1.8V), resulting in significant energy loss. To reduce the energy consumption of hydrogen production, current strategies focus on two main categories: developing highly active OER electrocatalysts to reduce the overpotential; and replacing OER with thermodynamically more favorable anode reactions.

[0004] Recent research has demonstrated the enormous potential of the urea oxidation reaction (UOR), owing to its extremely low theoretical oxidation potential (0.37 V vs. RHE). UOR technology not only converts pollutants in urea-containing wastewater (such as domestic sewage and industrial wastewater) into harmless products, alleviating water eutrophication, but more importantly, it can replace the energy-intensive OER process, significantly reducing the voltage requirement for hydrogen production by electrolysis, thereby improving energy conversion efficiency and economics.

[0005] Currently, while precious metal-based catalysts (such as Pt and Ir / Ru oxides) exhibit excellent activity for both UOR and HER, their global scarcity and high cost (accounting for over 40% of the total cost of an electrolysis system) severely restrict the commercial viability of large-scale hydrogen production devices. Therefore, the development of non-precious metal electrocatalysts with high activity, long life, and cost advantages is of great strategic significance for promoting the industrialization of urea-assisted efficient hydrogen production technology, promoting a sustainable hydrogen economy, and protecting the environment. Summary of the Invention

[0006] Based on the technical problems involved above, the purpose of this application is to provide a NF-loaded high-valent metal-doped-high-entropy layered double hydroxide / MOF composite material, a preparation method and an application, so as to develop a bifunctional electrocatalyst with high catalytic activity, long life and low cost, which can be used in the field of hydrogen production by water electrolysis and in the field of urea electrolysis.

[0007] In a first aspect, the present application provides a method for preparing a NF-supported high-valent metal-doped high-entropy layered double hydroxide / MOF composite material, characterized in that it is carried out according to the following steps:

[0008] Use dilute hydrochloric acid, deionized water, and alcohol to pretreat nickel foam to remove surface impurities;

[0009] Terephthalic acid, N,N-dimethylformamide, ethanol and water are mixed uniformly to obtain a mixed solution A;

[0010] Then, the pretreated nickel foam is immersed in the mixed solution A to obtain product I;

[0011] The product I is then transferred to a first autoclave for hydrothermal reaction, and the obtained product II is centrifuged, washed, and vacuum dried to obtain the precursor Ni-MOF;

[0012] A high-valent metal source, a trivalent iron source, a divalent cobalt source, a trivalent cerium source, a divalent zinc source, and urea are dissolved in deionized water to obtain a mixed solution B; the precursor Ni-MOF is then added to the mixed solution B to obtain a mixed solution C; the high-valent metal source includes a vanadium salt, a chromium salt, or a molybdenum salt;

[0013] The mixed solution C is transferred to a second high-pressure reactor, and the obtained product III is centrifuged, washed, and vacuum-dried to obtain the NF-supported high-valent metal-doped-high-entropy layered double hydroxide / MOF composite material, namely, M-FeCoNiZnCe-LDH / MOF (M=V, Cr, Mo) composite material.

[0014] In some embodiments, the molar volume ratio of terephthalic acid, N,N-dimethylformamide, ethanol and water is (0.1-1) mmol: (0.1-30) mL: (0.1-10) mL: (0.1-10) mL.

[0015] In some embodiments, the molar volume ratio of the ferric iron source: divalent cobalt source: trivalent cerium source: divalent zinc source: urea: deionized water is (0.1-1) mmol: (0.1-1) mmol: (0.1-1) mmol: (0.1-1) mmol: (2-3) mmol: (10-100) mL.

[0016] In some embodiments, the hydrothermal reaction conditions of the second high-pressure reactor are: reacting at a temperature of 100-140° C. for 8-12 hours; then, the obtained product III is centrifugally washed with anhydrous ethanol and deionized water, and vacuum dried at 60-80° C. for 10-12 hours.

[0017] In some embodiments, the trivalent iron source, divalent cobalt source, trivalent cerium source, and divalent zinc source include nitrates, acetates, carbonates, sulfates, and acetonates of the corresponding metals.

[0018] In some embodiments, the molar ratio of any one of the trivalent iron source, divalent cobalt source, trivalent cerium source, and divalent zinc source to the high-valent metal source is (0.1-1) mmol: (0-0.3) mmol.

[0019] In some embodiments, the hydrothermal reaction conditions of the first autoclave are: reaction at a temperature of 100-140° C. for 8-12 hours.

[0020] In some embodiments, the vacuum drying temperature for obtaining the precursor Ni-MOF is 60-80° C., and the drying time is 10-12 h.

[0021] On the other hand, the present application provides a NF-supported high-valent metal-doped-high-entropy layered double hydroxide / MOF composite material, which is prepared by any of the aforementioned preparation methods.

[0022] On the other hand, the present application also provides an application of a NF-supported high-valent metal-doped-high-entropy layered double hydroxide / MOF composite material as an electrolytic catalyst, including applications in water electrolysis and urea electrolysis.

[0023] The preparation method provided in this application is mild and controllable, highly practical, reproducible, environmentally friendly, and has significant advantages such as a wide source of raw materials and low cost.

[0024] Based on this method, a high-entropy LDH / MOF composite electrocatalytic material doped with high-valent metals (M-FeCoNiZnCe-LDH / MOF, M=V, Cr, Mo) was successfully constructed on a nickel foam substrate via a solvothermal preparation method. This material exhibits excellent activity in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and urea oxidation reaction (UOR). Its outstanding performance is attributed to the following synergistic enhancement mechanism:

[0025] 1. High-entropy LDH and MOF are closely linked by sharing metal nodes, which can promote the rapid conduction of electrons and effectively improve the conductive efficiency and stability of the material.

[0026] 2. MOF composites can greatly increase the specific surface area of the composite material, increase the contact area between the electrode material and the electrolyte, thereby improving the electrochemical performance, and also provide additional buffer space for the electrolyte, expand the accessible interface between the electrolyte and the nanostructure, thereby shortening the diffusion path of electrons and ions and improving the electrochemical kinetics;

[0027] 3. The synergistic effect between multiple metals in high-entropy LDH accelerates charge transfer, and different electronegativity regulates the electronic structure and charge density of the material;

[0028] 4. High-valent metal doping can effectively improve the catalytic activity of the material, improve the inherent catalytic activity of the catalyst, and expose more active sites. This doping not only optimizes the charge distribution of the catalytic material, but also improves the adsorption capacity of the active sites for reaction intermediates, thereby reducing the reaction energy barrier and ultimately significantly improving the intrinsic activity of the catalytic material.

[0029] The V / Cr / Mo-FeCoNiZnCe-LDH / MOF composite material prepared in this application has excellent bifunctional electrocatalytic performance and can be used for electrolysis of water to produce hydrogen, and can also be used for electrocatalytic urea oxidation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the present application but do not constitute a limitation of the present application. In the accompanying drawings:

[0031] Figure 1 The X-ray powder diffraction analysis pattern (XRD) of the NF-supported high-valent metal-doped-high-entropy layered double hydroxide / MOF composite material obtained in this application;

[0032] Figure 2 This is a morphology analysis image (SEM) of the high-valent metal vanadium-doped V-FeCoNiZnCe-LDH / MOF composite material obtained in Example 2 of this application;

[0033] Figure 3 a is a linear sweep voltammetry (LSV) graph comparing the hydrogen evolution reaction performance of NF-loaded high-valent metal doped-high entropy layered double hydroxide / MOF composite materials in 1M KOH obtained in exemplary embodiments 1 to 6 of the present application; Figure 3 b is a linear sweep voltammetry (LSV) graph comparing the hydrogen evolution reaction performance of the NF-supported mono- to penta-layered double hydroxide / MOF composite materials obtained in exemplary embodiments 7 to 13 of the present application in 1M KOH;

[0034] Figure 4 a is a linear sweep voltammetry (LSV) graph comparing the oxygen evolution reaction performance of the NF-supported mono- to penta-layered double hydroxide / MOF composite materials obtained in exemplary embodiments 7 to 13 of the present application in 1 M KOH; Figure 4 b, Figure 4c is a linear sweep voltammetry (LSV) graph comparing the oxygen evolution reaction performance of the NF-loaded high-valent metal doped-high entropy layered double hydroxide / MOF composite materials obtained in exemplary embodiments 1 to 6 of the present application in 1M KOH.

[0035] Figure 5 a, Figure 5 b is a linear sweep voltammetry (LSV) graph comparing the urea oxidation performance of NF-loaded high-valent metal-doped high-entropy layered double hydroxide / MOF composite materials obtained in exemplary embodiments 2, 5, 6, and 7 of the present application in 1M KOH+0.33M urea; Figure 5 c, Figure 5 d is a linear sweep voltammetry (LSV) graph comparing the urea oxidation reaction performance of the NF-supported mono- to penta-layered double hydroxide / MOF composite materials obtained in exemplary embodiments 7 to 13 of the present application in 1 M KOH + 0.33 M urea.

[0036] Figure 6 .Linear sweep voltammetry (LSV) curves comparing the urea oxidation reaction performance of high-valent metal doped-high entropy layered double hydroxide / MOF composite materials with different loading amounts of NF obtained in exemplary embodiments 1 to 4 of the present application in 1M KOH+0.33M urea.

[0037] Figure 7 a, Figure 7 b is a linear sweep voltammetry (LSV) graph comparing the complete water splitting performance of NF-loaded high-valent metal doped-high entropy layered double hydroxide / MOF composite materials obtained in exemplary embodiments 2, 5, 6, and 7 of the present application in 1 M KOH and 1 M KOH + 0.33 M urea; Figure 7 c, Figure 7 d is a linear sweep voltammetry (LSV) graph comparing the complete water splitting performance of the NF-supported mono- to penta-layered double hydroxide / MOF composite materials obtained in exemplary embodiments 7 to 13 of the present application in 1 M KOH and 1 M KOH + 0.33 M urea. DETAILED DESCRIPTION

[0038] The present application will be further described below in conjunction with specific examples. It should be understood that these embodiments are only intended to illustrate the present application and are not intended to limit the scope of the present application. In addition, it should be understood that after reading the contents taught in this application, those skilled in the art may make various changes or modifications to the present application, and these equivalent forms also fall within the scope defined by the claims appended hereto.

[0039] Metal-organic framework (MOF) catalysts, as porous materials, possess unique structures derived from the self-assembly of metal ions or metal clusters with organic ligands. Due to their high surface area, flexible and tunable pore structure, and abundant active sites, MOF catalysts have shown remarkable potential in heterogeneous catalysis. High-entropy LDHs are a novel class of materials composed of multiple metal elements doped in a high-entropy form. These materials, due to their unique structure and properties, have shown great potential in electrocatalysis. When combined, MOF and LDH form a heterostructure, and the synergistic effect of MOF and LDH gives MOF / LDHs excellent electrochemical performance. High-valent metal doping has attracted widespread attention due to its unique electronic control capabilities. This is primarily due to the fact that the electronegativity difference between the heteroatom and the host atoms after the introduction of heteroatoms triggers charge transfer. High-valent metals (such as Mo, V, and Cr) can significantly modulate the electronic structure of the host material due to their higher oxidation state and stronger electronegativity. This regulatory effect not only optimizes the charge distribution of the catalytic material, but also improves the adsorption capacity of the active sites for reaction intermediates, thereby reducing the reaction energy barrier and ultimately significantly improving the intrinsic activity of the catalytic material.

[0040] In the specific embodiment of the present application, the process of pre-treating nickel foam can be carried out according to the following conventional steps:

[0041] 1) Using 2-4 M dilute hydrochloric acid as a cleaning solution, ultrasonically clean the nickel foam for 10-20 minutes;

[0042] 2) Using ethanol as a cleaning solution, ultrasonically clean the nickel foam for 10 to 20 minutes;

[0043] 3) Using deionized water as a washing liquid, ultrasonically clean the nickel foam for 10 to 20 minutes;

[0044] 4) Vacuum drying at 50-60°C for 8-10 hours.

[0045] Example 1

[0046] The preparation method of V (VCl35 mg) modified FeCoNiZnCe-LDH / MOF bifunctional catalyst includes the following steps:

[0047] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0048] 5 mg of VCl₃, 202 mg of Fe(NO₃)₃·9H₂O, 146 mg of Co(NO₃)₂·6H₂O, 144 mg of Zn(NO₃)₂·6H₂O, 217 mg of Ce(NO₃)₃·6H₂O, and 150 mg of urea were weighed into a 100 mL beaker. 36 mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50 mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 h. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 h to obtain V-FeCoNiZnCe-LDH / MOF (5 mg).

[0049] Example 2

[0050] The preparation method of V (VCl3 15 mg) modified FeCoNiZnCe-LDH / MOF bifunctional catalyst includes the following steps:

[0051] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0052] 15 mg of VCl₃, 202 mg of Fe(NO₃)₃·9H₂O, 146 mg of Co(NO₃)₂·6H₂O, 144 mg of Zn(NO₃)₂·6H₂O, 217 mg of Ce(NO₃)₃·6H₂O, and 150 mg of urea were weighed into a 100 mL beaker. 36 mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50 mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 h. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 h to obtain V-FeCoNiZnCe-LDH / MOF (15 mg).

[0053] Example 3

[0054] The preparation method of V (VCl330 mg) modified FeCoNiZnCe-LDH / MOF bifunctional catalyst includes the following steps:

[0055] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0056] 30 mg of VCl₃, 202 mg of Fe(NO₃)₃·9H₂O, 146 mg of Co(NO₃)₂·6H₂O, 144 mg of Zn(NO₃)₂·6H₂O, 217 mg of Ce(NO₃)₃·6H₂O, and 150 mg of urea were weighed into a 100 mL beaker. 36 mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50 mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 h. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 h to obtain V-FeCoNiZnCe-LDH / MOF (30 mg).

[0057] Example 4

[0058] The preparation method of V (VCl345 mg) modified FeCoNiZnCe-LDH / MOF bifunctional catalyst includes the following steps:

[0059] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0060] 45 mg of VCl₃, 202 mg of Fe(NO₃)₃·9H₂O, 146 mg of Co(NO₃)₂·6H₂O, 144 mg of Zn(NO₃)₂·6H₂O, 217 mg of Ce(NO₃)₃·6H₂O, and 150 mg of urea were weighed into a 100 mL beaker. 36 mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50 mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 h. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 h to obtain V-FeCoNiZnCe-LDH / MOF (45 mg).

[0061] Example 5

[0062] The preparation method of Cr (15 mg) modified FeCoNiZnCe-LDH / MOF bifunctional catalyst comprises the following steps:

[0063] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0064] 15mg of Cr(NO3)2·9H2O, 202mg of Fe(NO3)3·9H2O, 146mg of Co(NO3)2·6H2O, 144mg of Zn(NO3)2·6H2O, 217mg of Ce(NO3)3·6H2O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnet were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes, followed by sonication to completely dissolve the mixture. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water, picked up with tweezers and evenly placed in a culture dish, covered with plastic wrap, and then evenly pierced with tweezers. The sample was placed in a vacuum drying oven set to 60°C and dried for 10 h to obtain Cr-FeCoNiZnCe-LDH / MOF (15 mg) material.

[0065] Example 6

[0066] The preparation method of Mo (15 mg) modified FeCoNiZnCe-LDH / MOF bifunctional catalyst comprises the following steps:

[0067] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0068] 15mg of Na2MoO4, 202mg of Fe(NO3)3·9H2O, 146mg of Co(NO3)2·6H2O, 144mg of Zn(NO3)2·6H2O, 217mg of Ce(NO3)3·6H2O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain Mo-FeCoNiZnCe-LDH / MOF (15mg).

[0069] Example 7

[0070] The preparation method of FeCoNiZnCe-LDH / MOF bifunctional catalyst comprises the following steps:

[0071] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0072] 202mg of Fe(NO3)3·9H2O, 146mg of Co(NO3)2·6H2O, 144mg of Zn(NO3)2·6H2O, 217mg of Ce(NO3)3·6H2O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain the FeCoNiZnCe-LDH / MOF material.

[0073] Example 8

[0074] The preparation method of FeCoNiZn-LDH / MOF bifunctional catalyst comprises the following steps:

[0075] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0076] 404mg of Fe(NO₃)₃·9H₂O, 292mg of Co(NO₃)₂·6H₂O, 288mg of Zn(NO₃)₂·6H₂O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain the 0.1-FeCoNiZn-LDH / MOF material.

[0077] Example 9

[0078] The preparation method of FeCoNiZn-LDH / MOF bifunctional catalyst comprises the following steps:

[0079] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0080] 202mg of Fe(NO3)3·9H2O, 146mg of Co(NO3)2·6H2O, 144mg of Zn(NO3)2·6H2O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pricked with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain the FeCoNiZn-LDH / MOF material.

[0081] Example 10

[0082] The preparation method of FeCoNiCe-LDH / MOF bifunctional catalyst comprises the following steps:

[0083] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0084] 202mg of Fe(NO3)3·9H2O, 146mg of Co(NO3)2·6H2O, 217mg of Ce(NO3)3·6H2O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes and then completely dissolved by sonication. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and several holes were evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain the FeCoNiCe-LDH / MOF material.

[0085] Example 11

[0086] The preparation method of FeCoNi-LDH / MOF bifunctional catalyst comprises the following steps:

[0087] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0088] 202mg of Fe(NO₃)₃·9H₂O, 146mg of Co(NO₃)₂·6H₂O, and 150mg of urea were weighed into a 100mL beaker. 36mL of deionized water and a magnetic bar were added. The mixture was stirred at an appropriate speed on a magnetic stirrer for 10 minutes, followed by complete dissolution by sonication. The solution was then transferred to a 50mL autoclave, the Ni-MOF precursor was added, and the reaction was hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain the FeCoNi-LDH / MOF material.

[0089] Example 12

[0090] The preparation method of FeNi-LDH / MOF bifunctional catalyst comprises the following steps:

[0091] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0092] 202mg of Fe(NO₃)₃·9H₂O and 150mg of urea were weighed into a 100mL beaker, followed by 36mL of deionized water and a magnetic stirrer. The mixture was stirred at an appropriate speed for 10 minutes, followed by complete dissolution by sonication. The solution was then transferred to a 50mL autoclave, and the Ni-MOF precursor was added. The reaction was then hydrothermally reacted in an oven at 100°C for 8 hours. The sample was washed three times with ethanol and deionized water. The sample was picked up with tweezers and evenly placed in a Petri dish. The dish was covered with plastic wrap and evenly pierced with tweezers. The sample was then dried in a vacuum oven at 60°C for 10 hours to obtain the FeNi-LDH / MOF material.

[0093] Example 13

[0094] The preparation method of Ni-LDH / MOF bifunctional catalyst comprises the following steps:

[0095] 166 mg of terephthalic acid was dissolved in 20 mL of N,N-dimethylformamide, 5 mL of ethanol, and 5 mL of water. Ultrasonic mixing was performed for 10 minutes to achieve uniform mixing. The treated NFs were then immersed in the mixed solution and transferred to a 50 mL polytetrafluoroethylene-lined stainless steel autoclave. The hydrothermal reaction was carried out in a 120°C oven for 4 hours. After cooling, the product was rinsed with deionized water and dried in a vacuum oven at 60°C for 10 hours. Finally, the Ni-MOF precursor was obtained.

[0096] Weigh 150mg of urea into a 100mL beaker, add 36mL of deionized water, and then add a magnet. Stir at an appropriate speed on a magnetic stirrer for 10 minutes, then completely dissolve it by ultrasonication. The solution is then transferred to a 50mL autoclave, and the precursor Ni-MOF is added. The reaction is then hydrothermally reacted in an oven at 100°C for 8 hours. The sample is washed three times with ethanol and deionized water. The sample is picked up with tweezers and evenly placed in a Petri dish. Cover with plastic wrap, poke several holes evenly with tweezers, and dry in a vacuum drying oven at 60°C for 10 hours to obtain the Ni-LDH / MOF material.

[0097] The raw materials and amounts used in the above examples are summarized in the following table:

[0098]

[0099]

[0100] Step 1 in the above implementation case is only an exemplary operation, and a large industrial stirred reactor can be used to improve production efficiency and product quantity.

[0101] like Figure 1 As shown, the XRD patterns of the V-doped V-FeCoNiZnCe-LDH / MOF (15 mg) sample grown on the NF substrate and its comparative sample were obtained by referring to the method of the embodiment. There are three typical strong diffraction peaks at 44.5°, 51.8° and 76.3°, which are caused by the diffraction peaks of NF. The remaining characteristic diffraction peaks at 20.49°23.81°, 30.14° and 38.26° correspond to the crystal planes of LDH (110), (111), (102) and (131), respectively (JCPDS#44-0617). In order to determine the exact structure of MOF in the material, the XRD pattern of V-FeCoNiZnCe-LDH / MOF (15 mg) was further compared in detail with the Ni-MOF (No.985792) simulation card, and it can be found that these peaks match well with Ni-MOF. In addition, the prepared FeCoNiZnCe-LDH / MOF and Ni-LDH / MOF materials also exhibited similar XRD patterns, indicating their LDH structures.

[0102] like Figure 2 As shown in the figure, a SEM image of a V-doped V-FeCoNiZnCe-LDH / MOF (15 mg) sample grown on a NF substrate was obtained using the method of the reference example. The image shows that the V-FeCoNiZnCe-LDH / MOF (15 mg) material exhibits a nanoflower-like structure. The composite material grows seamlessly on the nickel skeleton and is composed of many flat and large nanosheets, like a "nanoforest," which are interconnected to form a macroporous structure.

[0103] The obtained NF-loaded different high-valent metal doped-high entropy layered double hydroxide / MOF composites were used as electrode materials for HER / OER / UOR. Electrochemical tests were carried out in 1M KOH and urea (1M KOH + 0.33M urea) electrolyte using a three-electrode system. The linear sweep voltammetry (LSV) curves of HER / OER / UOR and complete water splitting are shown in Figure 2. Figure 3 a, 4b, 5a, 5b, 7a, 7b. Figure 3 a reflects the hydrogen evolution reaction (HER) activity of different high-valent metal doping-high entropy layered double hydroxide / MOF composites. Compared with Cr doping or Mo doping, V doping has excellent HER activity; Figure 4 b reflects the oxygen evolution reaction (OER) activity of different high-valent metal doping-high entropy layered double hydroxide / MOF composites. Compared with Cr doping or Mo doping, V doping has excellent OER activity; Figure 5 5a and 5b reflect the urea electrooxidation reaction (UOR) activity of different high-valent metal doping-high entropy layered double hydroxide / MOF composites. Compared with Cr doping or Mo doping, V doping has excellent UOR activity; Figure 7 Figures a and 7b reflect the overall water splitting performance of different high-valent metal doping-high entropy layered double hydroxide / MOF composites. Compared with Cr doping or Mo doping, V doping has excellent overall water splitting performance;

[0104] It can be clearly seen from the above Examples 2, 5, 6, and 7 that within the preset ratio range of the present application, the V-doped high-entropy layered double hydroxide / MOF composite material has the best catalytic activity, so the V-doped high-entropy layered double hydroxide / MOF composite material is the optimal embodiment.

[0105] The obtained NF-loaded V-doped high-entropy layered double hydroxide / MOF composites were used as electrode materials for HER / OER / UOR. Electrochemical tests were carried out in 1 M KOH and urea (1 M KOH + 0.33 M urea) electrolyte using a three-electrode system. The linear sweep voltammetry (LSV) curves of OER and UOR are shown in Figure 2. Figure 4 c. Figure 6 shown. Figure 4 c reflects the oxygen evolution reaction (OER) activity of different amounts of V-doped high-entropy layered double hydroxide / MOF composites. After 0.0955mmolV doping, the high-entropy layered double hydroxide / MOF composite material has excellent OER activity; Figure 6 The results show that the urea electrooxidation reaction (UOR) activity of different amounts of V-doped high-entropy layered double hydroxide / MOF composites is excellent after 0.0955 mmol V doping.

[0106] It can be clearly seen from the above Examples 1, 2, 3, and 4 that within the specific preset ratio range of the present application, the high-entropy layered double hydroxide / MOF composite material doped with 0.0955 mmolV has the best catalytic activity, so the 0.0955 mmolV-doped high-entropy layered double hydroxide / MOF composite material is the optimal embodiment.

[0107] The obtained mono- to penta-layered double hydroxide / MOF composites were used as electrode materials for HER / OER / UOR. Electrochemical tests were carried out in 1M KOH and urea (1M KOH + 0.33M urea) electrolyte using a three-electrode system. The linear sweep voltammetry (LSV) curves of HER / OER / UOR and complete water splitting are shown in Figure 2. Figure 3 As shown in b, 4a, 5c, 5d, 7c, and 7d. Figure 3 b reflects the hydrogen evolution reaction (HER) activity of the one- to five-membered layered double hydroxide / MOF composites. Compared with the one- to four-membered layered double hydroxide / MOF composites, the five-membered layered double hydroxide / MOF composites have excellent HER activity; Figure 4 a reflects the oxygen evolution reaction (OER) activity of the one- to five-membered layered double hydroxide / MOF composites. Compared with the one- to four-membered layered double hydroxide / MOF composites, the five-membered layered double hydroxide / MOF composites have excellent OER activity; Figure 5 c and 5d reflect the urea electrooxidation reaction (UOR) activity of the mono- to penta-layered double hydroxide / MOF composites. Compared with the mono- to quaternary ones, the penta-layered double hydroxide / MOF composites have excellent UOR activity. Figure 7 c and 7d reflect the overall water splitting performance of the one- to five-membered layered double hydroxide / MOF composites. Compared with the one- to four-membered layered double hydroxide / MOF composites, the five-membered layered double hydroxide / MOF composites have excellent overall water splitting performance.

[0108] It can be clearly seen from the above Examples 7, 9 to 13 that within the specific preset ratio range of the present application, the five-membered layered double hydroxide / MOF composite material has the most excellent catalytic activity, and therefore the five-membered layered double hydroxide / MOF composite material is the optimal embodiment.

[0109] The above description is only part of the embodiments or preferred embodiments of the present application, and does not limit the scope of protection of the present application. Any equivalent structure or equivalent process transformation made using the description of the present application, or directly or indirectly applied in other related technical fields, are also included in the scope of protection of the present application.

Claims

1. A method for preparing a NF-supported high-valent metal-doped high-entropy layered double hydroxide / MOF composite material, characterized in that: It is carried out according to the following steps: Use dilute hydrochloric acid, deionized water, and alcohol to pretreat nickel foam to remove surface impurities; Terephthalic acid, N,N-dimethylformamide, ethanol and water are mixed uniformly to obtain a mixed solution A; Then, the pretreated nickel foam is immersed in the mixed solution A to obtain product I; The product I is then transferred to a first autoclave for hydrothermal reaction, and the obtained product II is centrifuged, washed, and vacuum dried to obtain the precursor Ni-MOF; A high-valent metal source, a trivalent iron source, a divalent cobalt source, a trivalent cerium source, a divalent zinc source, and urea are dissolved in deionized water to obtain a mixed solution B; the precursor Ni-MOF is then added to the mixed solution B to obtain a mixed solution C; the high-valent metal source includes a vanadium salt, a chromium salt, or a molybdenum salt; The mixed solution C is transferred to a second high-pressure reactor, and the obtained product III is centrifuged, washed, and vacuum-dried to obtain the NF-supported high-valent metal-doped-high-entropy layered double hydroxide / MOF composite material, namely, M-FeCoNiZnCe-LDH / MOF (M=V, Cr, Mo) composite material.

2. The preparation method according to claim 1, wherein The molar volume ratio of the terephthalic acid, N,N-dimethylformamide, ethanol and water is (0.1-1) mmol: (0.1-30) mL: (0.1-10) mL: (0.1-10) mL.

3. The preparation method according to claim 1, wherein The molar volume ratio of the trivalent iron source: the divalent cobalt source: the trivalent cerium source: the divalent zinc source: the urea: the deionized water is (0.1-1) mmol: (0.1-1) mmol: (0.1-1) mmol: (0.1-1) mmol: (2-3) mmol: (10-100) mL.

4. The preparation method according to claim 1, wherein The hydrothermal reaction conditions of the second high-pressure reactor are: reaction at a temperature of 100-140° C. for 8-12 hours; The obtained product III is then washed by centrifugation with anhydrous ethanol and deionized water, and dried in vacuo at 60-80° C. for 10-12 h.

5. The preparation method according to claim 1, wherein The trivalent iron source, divalent cobalt source, trivalent cerium source and divalent zinc source include nitrates, acetates, carbonates, sulfates and acetic acid acetonates of the corresponding metals.

6. The preparation method according to claim 1, wherein the molar ratio of any one of the trivalent iron source, divalent cobalt source, trivalent cerium source, and divalent zinc source to the high-valent metal source is (0.1-1) mmol: (0-0.3) mmol.

7. The preparation method according to claim 1, wherein The hydrothermal reaction conditions of the first autoclave are: reaction at a temperature of 100 to 140° C. for 8 to 12 hours.

8. The preparation method according to claim 1, wherein The vacuum drying temperature for obtaining the precursor Ni-MOF is 60-80° C., and the drying time is 10-12 hours.

9. A NF-supported high-valent metal-doped high-entropy layered double hydroxide / MOF composite material, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 8.

10. Application of a NF-supported high-valent metal-doped high-entropy layered double hydroxide / MOF composite material as an electrolytic catalyst, including applications in water electrolysis and urea electrolysis.

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