A two-dimensional MOF-derived RuCo / NC nanocomposite material, its preparation method, and its application in electrocatalytic water splitting

Abstract

The present invention provides a two-dimensional MOF-derived RuCo / NC nanocomposite material, its preparation method, and application in electrocatalytic water splitting. The preparation method comprises the following steps: fully dispersing an inorganic cobalt source and an organic ligand in an organic solvent, subjecting the material to a hydrothermal reaction, centrifuging, and drying to obtain a precursor; fully dispersing the precursor and a ruthenium source in a solvent, subjecting the material to a hydrothermal reaction, centrifuging, and drying; and then subjecting the material to an annealing treatment. The material obtained by the present invention has a high specific surface area and large-sized mesopores, which facilitates full exposure of active sites and sufficient contact with the electrolyte. Ru induces an increase in the valence state of Co and an increase in the pyridinic N content, which not only promotes the formation of CoOOH active species during the OER process, thereby significantly improving OER activity, but also enhances H* adsorption, thereby optimizing the HER reaction kinetics. Therefore, the material exhibits excellent electrocatalytic water splitting activity and stability, and has good industrial application value.

Description

Technical Field

[0001] The present invention relates to a two-dimensional MOF-derived RuCo / NC nanocomposite material, a preparation method thereof, and application in electrocatalytic water splitting, belonging to the technical fields of material synthesis and water electrolysis. Background Art

[0002] Hydrogen production by water electrolysis is more competitive than hydrogen production from fossil fuels due to its high efficiency, pollution-free nature, and strong adaptability to renewable energy. The OER half-reaction in water electrolysis is an energy-climbing process that requires the transfer of four electrons and the release of four protons, which is a bottleneck for water electrolysis. Therefore, the development of efficient OER electrocatalysts is crucial to reducing the overall energy consumption of the process. However, the high water dissociation energy barrier of alkaline HER results in a reaction rate that is 2–3 orders of magnitude lower than that of acidic HER. Currently, Pt-based, Ir-based, and Ru-based electrocatalysts are the most active HER and OER electrocatalysts, respectively. However, the high price and scarce reserves of precious metals limit the large-scale application of precious metals. Reducing their usage or finding inexpensive transition metal compounds as alternatives has become an inevitable option.

[0003] Co has a strong affinity for oxygen-containing species, which makes it unique in electrocatalytic OER. However, the limited number of active sites forces researchers to adopt different strategies to improve its intrinsic activity. Among them, alloying has been proven to be a direct and effective method to regulate the surface properties of electrocatalysts (such as electronic structure, synergistic coupling effect and wettability). The platinum group element Ru has a Pt-like H* Gibbs free energy change (ΔG H* ) and the cost is much lower than Pt (4% of Pt), showing excellent HER activity similar to Pt. Therefore, forming an alloy with a trace amount of Ru and a Co matrix can take advantage of the optimal cat-OH bond strength of Co to promote the dissociation of water into H ads , and can utilize Ru's strong H* adsorption capacity to promote H ads Converting it into H2 is a promising method to obtain efficient OWS electrocatalysts. For example, Lin et al. constructed RuCo alloy nanoparticles uniformly anchored on the oxidized CNTs structure through ozone oxidation, freeze drying and thermal activation. The cross-linked hierarchical structure and tunable electronic structure work together to accelerate ion diffusion and charge transfer, thereby improving the reaction kinetics. However, the advantages of the synergistic effect between RuCo nanostructure and carbon cannot be fully utilized. The prepared electrocatalyst requires a potential of 1.56V to start the complete water splitting to reach 10mAcm -2 current density.

[0004] Metal-organic frameworks (MOFs) have high specific surface area and regular, ordered open frameworks. After carbonization derivatization, they can form abundant pores and incorporate intrinsic ligand heteroatoms and metal centers into the carbon matrix, which helps to fully expose the active sites and achieve dual optimization of the functionality and conductivity of metal particles. They are potential excellent precursors for the preparation of RuCo alloys. Chinese patent document CN109453811A discloses a bifunctional composite water electrolysis catalyst, preparation method, and application. First, 4-(2,4,6-tricarboxylphenyl)-2,2':6',2"-terpyridine is used as a ligand, which is mixed and coordinated with polyvinylpyrrolidone, a soluble cobalt salt, and a soluble ruthenium salt. A composite material, RuCo-MOF, is obtained through a hydrothermal reaction. The composite material is then calcined to obtain a bifunctional composite catalyst, RuCo@NC, comprising a nitrogen-doped porous carbon-coated RuCo alloy. The nitrogen-doped porous carbon in this catalyst has a layered structure, and the RuCo alloy particles are independently and evenly dispersed within the nitrogen-doped porous carbon layered structure. However, the material in this invention has difficulty maintaining long-term hydrogen evolution stability at high applied current densities and exhibits hydrogen evolution activity only in acidic and alkaline media. However, the slow kinetics of the oxygen evolution reaction are the primary factor limiting the efficiency of water electrolysis. Therefore, designing an efficient bifunctional hydrogen / oxygen evolution catalyst is key to improving water electrolysis efficiency and reducing device energy consumption.

[0005] The present invention is proposed to solve the above-mentioned problems. Summary of the Invention

[0006] In response to the shortcomings of the prior art, the present invention provides a two-dimensional MOF-derived RuCo / NC nanocomposite material, a preparation method thereof, and an application thereof in electrocatalytic water splitting. The preparation method of the present invention is simple and quick, and the obtained material is environmentally friendly. The two-dimensional MOF-derived RuCo / NC nanocomposite material obtained by the present invention has a high specific surface area and large-sized mesopores, which are conducive to the full exposure of active sites and sufficient contact with the electrolyte; and Ru induces an increase in the valence state of Co and an increase in the pyridinic N content, which can not only promote the formation of CoOOH active substances in the OER process, thereby significantly improving the OER activity, but also enhance the adsorption of H*, thereby optimizing the HER reaction kinetics; therefore, it exhibits excellent electrocatalytic water splitting activity and stability in alkaline media, and has good industrial application value.

[0007] Terminology Notes:

[0008] Room temperature has a well-known meaning in the art, generally referring to 25±5°C.

[0009] The technical solutions of the present invention are as follows:

[0010] A two-dimensional MOF-derived RuCo / NC nanocomposite material is a composite porous material of RuCo alloy and nitrogen-doped carbon. The micromorphology of the composite material is as follows: RuCo alloy nanoparticles coated with nitrogen-doped carbon are uniformly loaded on porous nitrogen-doped carbon with a hexagonal sheet structure.

[0011] According to the preferred embodiment of the present invention, the pyridine N content in the RuCo / NC nanocomposite material is 40-50 wt%; the specific surface area is 150-250 m 2 g -1 ; The pore size is 2-40nm.

[0012] According to the present invention, the particle size of the RuCo alloy nanoparticles coated with nitrogen-doped carbon is preferably 3-6 nm, and the size of the porous nitrogen-doped carbon with a hexagonal sheet structure is 3-5 μm. The above size refers to the length of the longest diagonal of the hexagon.

[0013] The preparation method of the above-mentioned two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0014] (1) The inorganic cobalt source and the organic ligand are fully dispersed in an organic solvent, subjected to a hydrothermal reaction, centrifuged, and dried to obtain a metal organic framework Co-BDC-NH2 precursor;

[0015] (2) fully dispersing the metal organic framework Co-BDC-NH2 precursor and the ruthenium source in a solvent, subjecting the mixture to a hydrothermal reaction, centrifuging, and drying to obtain the RuCo-BDC-NH2 precursor;

[0016] (3) The RuCo-BDC-NH2 precursor was annealed to obtain a two-dimensional MOF-derived RuCo / NC nanocomposite material.

[0017] According to the preferred embodiment of the present invention, in step (1), the inorganic cobalt source is cobalt nitrate hexahydrate, and the organic ligand is 2-aminoterephthalic acid.

[0018] According to the preferred embodiment of the present invention, in step (1), the molar ratio of the inorganic cobalt source to the organic ligand is 1:(0.3-0.6), preferably 1:0.42.

[0019] According to the present invention, preferably, in step (1), the organic solvent is a mixed solvent of methanol and N,N-dimethylformamide; in the mixed solvent, the volume ratio of methanol to N,N-dimethylformamide is 1:1-3, preferably 1:2; the volume ratio of the amount of the organic ligand to the organic solvent is 0.01-0.0.25 mol / L, preferably 0.05 mol / L.

[0020] According to the preferred embodiment of the present invention, in step (1), the hydrothermal reaction time is 22-26 hours, preferably 24 hours; the hydrothermal reaction temperature is 80-120°C, preferably 100°C.

[0021] Preferably, according to the present invention, in step (2), the solvent is ethanol and the ruthenium source is anhydrous ruthenium trichloride.

[0022] According to the preferred embodiment of the present invention, in step (2), the mass ratio of the metal organic framework Co-BDC-NH2 precursor to the ruthenium source is 2-34:1, preferably 10:1.

[0023] According to the preferred embodiment of the present invention, in step (2), the mass ratio of the metal organic framework Co-BDC-NH2 precursor to the volume ratio of the solvent is 1-10 mg / mL.

[0024] According to the preferred embodiment of the present invention, in step (2), the hydrothermal reaction temperature is 60-120°C, preferably 80°C; the hydrothermal reaction time is 8-16h, preferably 12h.

[0025] According to the present invention, preferably, in step (3), the annealing temperature is 300-700°C, the annealing time is 0.5-3h, and the annealing is carried out under the protection of an inert gas; preferably, the annealing temperature is 500°C, the annealing time is 1h, and the inert gas is nitrogen or argon.

[0026] According to a preferred technical solution of the present invention, the preparation method of the two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0027] (1) 3.425 mmol Co(NO3)2·6H2O and 1.450 mmol 2-aminoterephthalic acid were dispersed in a mixed solvent of 10 mL CH3OH and 20 mL DMF, and stirred at room temperature for 3 h to obtain a pink-purple uniform solution. The mixture was then poured into a 50 mL polytetrafluoroethylene-lined autoclave and maintained in an oven at 100°C for 24 h. After the reaction was completed and naturally cooled to room temperature, the obtained pink-purple sample was centrifuged with DMF and CH3OH to remove unreacted impurities, and dried under vacuum at 60°C overnight to obtain the metal-organic framework Co-BDC-NH2 precursor.

[0028] (2) 100 mg of the metal-organic framework Co-BDC-NH2 precursor was dispersed in 20 mL of C2H5OH, and 10 mg of RuCl3 was added to the above solution. The mixture was stirred at room temperature for 10 min to obtain a yellow-green uniform mixed solution. The mixture was then poured into a 50 mL polytetrafluoroethylene-lined autoclave and maintained in an 80 °C oven for 12 h. After the reaction was completed and naturally cooled to room temperature, the obtained product was centrifuged with C2H5OH and dried in vacuum at 60 °C overnight to obtain the RuCo-BDC-NH2 precursor.

[0029] (3) 200 mg of RuCo-BDC-NH2 precursor was placed in a ceramic boat in a tube furnace and then heated at 5 °C min -1 The temperature was raised to 500 °C in an Ar flowing atmosphere and maintained for 1 h. After the reaction was completed, the mixture was naturally cooled to room temperature in an Ar atmosphere and collected to obtain a two-dimensional MOF-derived RuCo / NC nanocomposite material.

[0030] The above two-dimensional MOF-derived RuCo / NC nanocomposites are used in hydrogen evolution from water electrolysis, oxygen evolution from water electrolysis or electrocatalytic water splitting.

[0031] The technical features and beneficial effects of the present invention are as follows:

[0032] 1. The present invention first obtains a sheet-like Co-BDC-NH2 precursor template by solvent thermal reaction, and then uses Ru dissolved in the solvent to 3+ Cation exchange was performed on the precursor to obtain a flaky RuCo-BDC-NH2 precursor. Finally, annealing under an inert gas atmosphere achieved the derivation of the RuCo-BDC-NH2 into the target RuCo / NC electrocatalyst, anchoring a RuCo alloy onto a porous N-doped flaky carbon layer. The preparation method is simple, rapid, and environmentally friendly.

[0033] 2. The present invention introduces Ru 3+ Preparation of RuCo-BDC-NH2 precursor will not destroy the physical structure of the metal organic framework Co-BDC-NH2 precursor template; and Ru 3+ The introduction of Ru reduces the size of the nanoparticles, increasing the specific surface area and improving the utilization of active sites, thereby enhancing electrocatalytic activity. Simultaneously, Ru incorporation effectively inhibits the surface oxidation of Co, facilitating the synergistic effect of the two. The present invention requires an appropriate amount of ruthenium source. A suitable amount of ruthenium source does not significantly alter the flaky morphology of Co / NC. However, excessive ruthenium source causes the metal particles in the Ru-Co / NC to agglomerate, and even fragments and collapses the 2D carbon framework, losing effective anchoring of the metal sites.

[0034] 3. The organic ligand used in this invention is preferably 2-aminoterephthalic acid. The electron-rich pyridinic nitrogen can optimize H* adsorption, thereby reducing the energy barrier of the water dissociation step in the alkaline HER process, giving RuCo / NC a significant HER advantage over Co / NC. The presence of nitrogen enhances the intrinsic hydrogen and oxygen evolution activities of RuCo / C to a certain extent, significantly increases the number of active sites, and moderately improves the red charge transfer efficiency of this invention.

[0035] 4. The two-step hydrothermal method adopted in the present invention to prepare RuCo-BDC-NH2 is to first form a stable MOF structure, and then use it as a template for partial cation exchange and finally form a RuCo alloy. In contrast, the one-step hydrothermal method will result in the competitive coordination of Ru to 2-BDC-NH2, making it difficult to form Co-BDC-NH2 with a regular structure and clear active sites.

[0036] 5. The annealing temperature for preparing the RuCo / NC nanocomposite material in the present invention needs to be appropriate. If the temperature is too low, the preparation conditions of the RuCo alloy cannot be met. If the annealing temperature is too high, the metal particles in the RuCo / NC will begin to agglomerate and even the 2D carbon skeleton structure will collapse.

[0037] 6. The powdered electrocatalyst prepared in this invention is more suitable for large-scale slurry preparation and spraying / coating / transferring onto proton exchange membranes for practical PEM electrolysis hydrogen production devices. Furthermore, the nitrogen and carbon sources in the organic ligands introduced during the MOF preparation process eliminate the need for a separate carbon source, which reduces raw material loss and lowers costs from an industrial production perspective.

[0038] 7. In the nanomaterial prepared by the present invention, RuCo alloy nanoparticles coated with nitrogen-doped carbon with a particle size of 3 to 6 nm are uniformly dispersed on the porous nitrogen-doped carbon with a hexagonal sheet structure. The alloy nanoparticles are coated with 2 to 4 layers of amorphous nitrogen-doped carbon, which plays a dual role of enhancing conductivity and inhibiting particle agglomeration and deactivation during the electrocatalytic process, thereby improving structural stability. The nanomaterial of the present invention has a high specific surface area and large-sized mesopores, and the RuCo alloy nanoparticles coated with nitrogen-doped carbon have a small particle size, which is conducive to fully utilizing the advantages of Co's strong oxygen bonding ability and Ru's strong hydrogen adsorption ability, and is conducive to the full exposure of active sites, the rapid penetration of electrolytes and the full contact between active sites and electrolytes, thereby optimizing water electrolysis performance. The Co sites in the nanomaterial of the present invention present a state of reduced electron cloud density, and the increase in Co valence is conducive to coupling with oxygen-containing intermediate species to form a CoOOH active phase during the OER process. The pyridinic N content in the material of the present invention is as high as 44.86%. The electron-rich pyridinic N can optimize the adsorption of H*, thereby reducing the energy barrier of the water dissociation step in the alkaline HER process, making RuCo / NC show obvious HER advantages over Co / NC.

[0039] 8. The nanomaterials prepared by the present invention achieve multifunctional electrocatalytic processes of efficient alkaline HER, OER, OWS and pure water OWS; and have excellent HER, OER and electrocatalytic complete water splitting activity and stability, and have good industrial development prospects. The linear polarization curve performance test of the present invention found that the two-dimensional MOF-derived RuCo / NC nanocomposite material has excellent alkaline HER and OER intrinsic activities (59 and 248 mV@10mA cm -2 ), with outstanding durability (100 and 60h@100mAcm -2 ); The two-electrode alkaline OWS system can achieve 10 mA cm at only 1.523 V. -2 The current density is 200V; under pure water conditions at 70°C, only 1.881V is required to achieve a current of 100mA, showing an excellent application prospect for electrolysis of water to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a transmission electron micrograph of the Co-BDC-NH2 precursor prepared in Example 1;

[0041] Figure 2 This is a transmission electron micrograph of the RuCo-BDC-NH2 precursor prepared in Example 1;

[0042] Figure 3 This is a transmission electron microscopy image of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1;

[0043] Figure 4 This is a transmission electron microscope image of the Co / NC nanomaterial prepared in Comparative Example 1;

[0044] Figure 5 This is a transmission electron micrograph of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 2;

[0045] Figure 6 This is a transmission electron micrograph of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 3;

[0046] Figure 7 This is a transmission electron micrograph of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 4;

[0047] Figure 8 This is a high-resolution transmission electron micrograph of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1;

[0048] Figure 9 Selected electron diffraction images of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1;

[0049] Figure 10 X-ray diffraction patterns of the Co-BDC-NH2 precursor, RuCo-BDC-NH2 precursor, and two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1, and the Co / NC nanomaterial prepared in Comparative Example 1; wherein the abscissa is degrees and the ordinate is intensity;

[0050] Figure 11 X-ray photoelectron spectra of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 (a) Full spectrum, (b) Co 2p, (c) Ru 3p, and (d) N 1s high-resolution spectra; where the abscissa is binding energy and the ordinate is intensity;

[0051] Figure 12 BET test images of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1: (a) N2 isothermal adsorption / desorption curve at 77K, where the abscissa is the relative pressure / P / P0 and the ordinate is the adsorption amount; and (b) pore size distribution diagram, where the abscissa is the pore diameter and the ordinate is the pore volume;

[0052] Figure 13The hydrogen evolution performance tests of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1, the Co / NC nanomaterial prepared in Comparative Example 1, and the commercially available Pt / C with a Pt content of 20 wt% are as follows: (a) linear voltammetric curve, where the abscissa is the standard hydrogen electrode potential for the Ag / AgCl reference electrode; (b) Tafel plot, where the ordinate is the potential; (c) double layer fitting curve, where the abscissa is the scan rate; (d) AC impedance diagram, with the inset being the equivalent circuit diagram; (e) linear polarization curve of RuCo / NC before and after 3000 cycles of cyclic voltammetric scanning, where the abscissa is the standard hydrogen electrode potential for the Ag / AgCl reference electrode; and (f) at 100 mA cm -2 The Vt curve of RuCo / NC electrolysis for 100 h, where the horizontal axis is time and the vertical axis is potential;

[0053] Figure 14 Oxygen evolution performance tests of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1, the Co / NC nanomaterial prepared in Comparative Example 1, and commercially available RuO2: (a) linear voltammetric curve, where the abscissa is the standard hydrogen electrode potential for the Ag / AgCl reference electrode; (b) Tafel plot, where the ordinate is the potential; (c) double layer fitting curve, where the abscissa is the scan rate; (d) AC impedance diagram, with the inset being the equivalent circuit diagram; (e) linear polarization curve of RuCo / NC before and after 3000 cycles of cyclic voltammetric scanning, where the abscissa is the standard hydrogen electrode potential for the Ag / AgCl reference electrode; and (f) at 100 mA cm -2 The Vt curve of RuCo / NC electrolysis for 60 h, where the horizontal axis is time and the vertical axis is potential;

[0054] Figure 15 Comparison of hydrogen evolution linear polarization curves for the two-dimensional MOF-derived RuCo / NC nanocomposites prepared in Examples 1-7 and the nanomaterial prepared in Comparative Example 2; the abscissa is the standard hydrogen electrode potential relative to the Ag / AgCl reference electrode;

[0055] Figure 16 Comparison of oxygen evolution linear polarization curves of the two-dimensional MOF-derived RuCo / NC nanocomposites prepared in Examples 1-7 and the nanomaterial prepared in Comparative Example 2; the abscissa is the standard hydrogen electrode potential relative to the Ag / AgCl reference electrode.

[0056] Figure 17The overall water splitting performance tests of the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1, the Co / NC nanomaterial prepared in Comparative Example 1, and commercially available Pt / C with a Pt content of 20 wt% and RuO2 are as follows: (a) linear polarization curves of overall water splitting, where the abscissa is the potential; and (b) RuCo / NC at 10 mA cm -2 The Vt curve below, where the horizontal axis is time and the vertical axis is potential.

[0057] Figure 18 The full water splitting performance test of the two-dimensional MOF-derived RuCo / NC nanocomposite material obtained in Example 1 and commercially available Pt / C and RuO2 with a Pt content of 20 wt% is shown: (a) Schematic diagram of the homemade PEM electrolyzer structure; (b) LSV curves of iR compensation of RuCo / NC / NF‖RuCo / NC / NF, 20% Pt / C / NF‖RuO2 / NF and NF‖NF in pure water at room temperature (25°C) and industrial temperature (60, 70 and 80°C) of PEM water electrolysis, where the horizontal axis is potential and the vertical axis is current; (c) Potential bar graphs of 100 mA and 200 mA respectively, where the vertical axis is potential. DETAILED DESCRIPTION

[0058] The method of the present invention is described in detail below with reference to specific embodiments and accompanying drawings.

[0059] Unless otherwise specified, the experimental methods used in the examples are conventional methods. The materials, reagents, etc. used in the examples are all commercially available unless otherwise specified.

[0060] Example 1

[0061] A method for preparing a two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0062] 3.425mmol (996.8mg) of Co(NO3)2·6H2O and 1.450mmol (262.7mg) of 2-aminoterephthalic acid (2-NH2-BDC) were dispersed in a mixed solvent of 10mL of CH3OH and 20mL of DMF, and stirred at room temperature for 3h to obtain a pink-purple uniform solution. The mixture was then poured into an autoclave with a 50mL polytetrafluoroethylene liner and maintained in an oven at 100°C for 24h. After the reaction was completed and naturally cooled to room temperature, the obtained pink-purple sample was centrifuged with DMF and CH3OH to remove unreacted impurities, and dried under vacuum at 60°C overnight to obtain the metal-organic framework Co-BDC-NH2 precursor, named Co-BDC-NH2;

[0063] 100 mg of the metal-organic framework Co-BDC-NH2 precursor was dispersed in 20 mL of C2H5OH, and 0.05 mmol (10 mg) of RuCl3 was added to the above solution. The mixture was stirred at room temperature for 10 min to obtain a yellow-green uniform mixed solution. The mixture was then poured into an autoclave with a 50 mL polytetrafluoroethylene liner and maintained in an 80 ° C oven for 12 h. After the reaction was completed and naturally cooled to room temperature, the obtained product was centrifuged with C2H5OH and dried in vacuum at 60 ° C overnight to obtain a RuCo-BDC-NH2 precursor, recorded as RuCo-BDC-NH2.

[0064] 200 mg of RuCo-BDC-NH2 precursor was placed in a ceramic boat in a tube furnace and heated at 5 °C min -1 The temperature was raised to 500 °C in an Ar flowing atmosphere at a rate of 0.05 and maintained for 1 h. After the reaction was completed, the mixture was naturally cooled to room temperature in an Ar atmosphere and collected to obtain a two-dimensional MOF-derived RuCo / NC nanocomposite material. The sample was recorded as RuCo / NC.

[0065] Example 2

[0066] A method for preparing a two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0067] The preparation of Co-BDC-NH2 was the same as in Example 1;

[0068] 100 mg of the metal-organic framework Co-BDC-NH2 precursor was dispersed in 20 mL of C2H5OH, and 0.025 mmol (5 mg) of RuCl3 was added to the above solution. The mixture was stirred at room temperature for 10 min to obtain a yellow-green uniform mixed solution. The mixture was then poured into an autoclave with a 50 mL polytetrafluoroethylene liner and maintained in an 80 ° C oven for 12 h. After the reaction was completed and naturally cooled to room temperature, the obtained product was centrifuged with C2H5OH and dried in vacuum at 60 ° C overnight to obtain a RuCo-BDC-NH2 precursor, recorded as RuCo-BDC-NH2.

[0069] The preparation of the two-dimensional MOF-derived RuCo / NC nanocomposite material was the same as in Example 1, and the sample was recorded as 5 mg RuCo / NC.

[0070] Example 3

[0071] A method for preparing a two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0072] The preparation of Co-BDC-NH2 was the same as in Example 1;

[0073] 100 mg of the metal-organic framework Co-BDC-NH2 precursor was dispersed in 20 mL of C2H5OH, and 0.15 mmol (30 mg) of RuCl3 was added to the above solution. The mixture was stirred at room temperature for 10 min to obtain a yellow-green uniform mixed solution. The mixture was then poured into an autoclave with a 50 mL polytetrafluoroethylene liner and maintained in an 80 ° C oven for 12 h. After the reaction was completed and naturally cooled to room temperature, the obtained product was centrifuged with C2H5OH and dried in vacuum at 60 ° C overnight to obtain a RuCo-BDC-NH2 precursor, recorded as RuCo-BDC-NH2.

[0074] The preparation of the two-dimensional MOF-derived RuCo / NC nanocomposite material was the same as in Example 1, and the sample was recorded as 30 mg RuCo / NC.

[0075] Example 4

[0076] A method for preparing a two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0077] The preparation of Co-BDC-NH2 was the same as in Example 1;

[0078] 100 mg of the metal-organic framework Co-BDC-NH2 precursor was dispersed in 20 mL of C2H5OH, and 0.25 mmol (50 mg) of RuCl3 was added to the above solution. The mixture was stirred at room temperature for 10 min to obtain a yellow-green uniform mixed solution. The mixture was then poured into an autoclave with a 50 mL polytetrafluoroethylene liner and maintained in an 80 ° C oven for 12 h. After the reaction was completed and naturally cooled to room temperature, the obtained product was centrifuged with C2H5OH and dried in vacuum at 60 ° C overnight to obtain a RuCo-BDC-NH2 precursor, recorded as RuCo-BDC-NH2.

[0079] The preparation of the two-dimensional MOF-derived RuCo / NC nanocomposite material was the same as in Example 1, and the sample was recorded as 50 mg RuCo / NC.

[0080] Example 5

[0081] A method for preparing a two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0082] The preparation of Co-BDC-NH2 and RuCo-BDC-NH2 was the same as in Example 1;

[0083] 200 mg of RuCo-BDC-NH2 precursor was placed in a ceramic boat in a tube furnace and heated at 5 °C min -1The temperature was raised to 300 °C in an Ar flowing atmosphere at a rate of 100 °C and maintained for 1 h. After the reaction was completed, the sample was naturally cooled to room temperature in an Ar atmosphere and collected to obtain a two-dimensional MOF-derived RuCo / NC nanocomposite material. The sample was recorded as RuCo / NC-300 °C.

[0084] Example 6

[0085] A method for preparing a two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps:

[0086] The preparation of Co-BDC-NH2 and RuCo-BDC-NH2 was the same as in Example 1;

[0087] 200 mg of RuCo-BDC-NH2 precursor was placed in a ceramic boat in a tube furnace and heated at 5 °C min -1 The temperature was raised to 700 °C in an Ar flowing atmosphere and maintained for 1 h. After the reaction was completed, the sample was naturally cooled to room temperature in an Ar atmosphere and collected to obtain a two-dimensional MOF-derived RuCo / NC nanocomposite material. The sample was recorded as RuCo / NC-700 °C.

[0088] Example 7

[0089] A method for preparing a two-dimensional MOF-derived RuCo / C nanocomposite material comprises the following steps:

[0090] 3.425mmol (996.8mg) Co(NO3)2·6H2O and 1.450mmol (240.9mg) terephthalic acid (1,4-BDC) were dispersed in a mixed solvent of 10mL CH3OH and 20mL DMF, and stirred at room temperature for 3h to obtain a pink-purple uniform solution. The mixture was then poured into an autoclave with a 50mL polytetrafluoroethylene liner and maintained in an oven at 100℃ for 24h. After the reaction was completed and naturally cooled to room temperature, the obtained pink-purple sample was centrifuged with DMF and CH3OH to remove unreacted impurities, and dried under vacuum at 60℃ overnight to obtain the metal-organic framework Co-BDC precursor, named Co-BDC;

[0091] The preparation of RuCo-BDC and RuCo / C is the same as that of RuCo-BDC-NH2 and RuCo / NC in Example 1, and the sample is recorded as RuCo / C.

[0092] Comparative Example 1

[0093] A method for preparing a Co / NC nanomaterial comprises the following steps:

[0094] The preparation of Co-BDC-NH2 was the same as in Example 1;

[0095] 200 mg of Co-BDC-NH2 precursor was placed in a ceramic boat in a tube furnace and heated at 5 °C min -1 The reaction was continued until 500 °C at a heating rate of 100 °C under an Ar flow atmosphere and maintained for 1 h. After the reaction was completed, the sample was naturally cooled to room temperature under an Ar atmosphere and collected. The obtained sample was recorded as Co / NC.

[0096] Comparative Example 2

[0097] A method for preparing a RuCo / NC nanocomposite material comprises the following steps:

[0098] The Ru source was introduced by a one-step hydrothermal method: 3.425 mmol (996.8 mg) of Co(NO3)2·6H2O, 1.450 mmol (262.7 mg) of 2-aminoterephthalic acid (2-NH2-BDC) and 0.05 mmol (10 mg) of RuCl3 were dispersed in a mixed solvent of 10 mL of CH3OH and 20 mL of DMF, and stirred at room temperature for 3 h to obtain a uniform solution. The mixture was then poured into an autoclave with a 50 mL polytetrafluoroethylene liner and maintained in an oven at 100°C for 24 h. After the reaction was completed and naturally cooled to room temperature, the obtained sample was centrifuged with DMF and CH3OH to remove unreacted impurities, and dried under vacuum at 60°C overnight to obtain the metal-organic framework RuCo-BDC-NH2 precursor, named RuCo-BDC-NH2;

[0099] The preparation of the two-dimensional MOF-derived RuCo / NC nanocomposite material was the same as in Example 1, and the sample was denoted as RuCo / NC-onestep.

[0100] Test Example 1

[0101] The Co-BDC-NH2 precursor, RuCo-BDC-NH2 precursor and two-dimensional MOF-derived RuCo / NC nanocomposites prepared in Example 1, the two-dimensional MOF-derived RuCo / NC nanocomposites prepared in Examples 2-4, and the nanomaterials prepared in Comparative Examples 1 and 2 were characterized and tested as follows:

[0102] Transmission electron microscopy: First, the transmission electron microscopy image of the Co-BDC-NH2 precursor prepared in Example 1 is as follows Figure 1 As shown, Co-BDC-NH2 has a hexagonal sheet structure, is smooth and has a size (longest diagonal) of about 3 to 5 μm. The transmission electron microscope image of the RuCo-BDC-NH2 precursor prepared in Example 1 is shown in FIG. Figure 2 As shown, the hexagonal morphology is very similar to that of Co-BDC-NH2, confirming that Ru 3+The introduction of the precursor does not destroy the physical structure of the Co MOFs template, and the size is about 3 to 5 μm. The transmission electron microscope image of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 is as follows: Figure 3 As shown in the figure, it is found that the particle distribution of RuCo / NC is more uniform. From the embedded particle size distribution diagram, it can be seen that the obtained particle size is concentrated at 4.0nm, and Ru 3+ The introduction of RuCo / NC will reduce the particle size, which will lead to an increase in specific surface area and an improvement in the utilization of active sites, thereby enhancing the electrocatalytic activity. In addition, there are obvious gaps between the RuCo / NC particles. This porous property is conducive to the rapid penetration of the electrolyte. The transmission electron microscope image of the Co / NC nanomaterial prepared in Comparative Example 1 is shown in FIG. Figure 4 As shown in Figure 2, it is found that Co / NC still maintains a sheet-like structure, and the metal / metal oxide nanoparticles are relatively evenly distributed on the carbon layer, but there is still a local agglomeration of particles. From the embedded particle size distribution diagram, it can be seen that the particle size is concentrated at 6.5nm. The transmission electron microscopy images of the two-dimensional MOF-derived RuCo / NC nanocomposites prepared in Example 2-4 are shown in Figure 2. Figure 5-7 As shown in the figure, a small amount of RuCl3 did not significantly change the flaky morphology of Co / NC, while after the action of excessive RuCl3, the metal particles in Ru-Co / NC began to agglomerate, and even the 2D carbon skeleton structure became broken and collapsed, losing effective anchoring to the metal sites.

[0103] High-resolution transmission electron microscopy: High-resolution images of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 are shown in Figure 2. Figure 8 As shown, the lattice distances of the prepared two-dimensional MOF-derived RuCo / NC nanocomposites were measured to be only 0.173, 0.195, and 0.208 nm, which are attributed to the interplanar spacing of the Co (200) plane and the RuCo (101) and (002) planes, respectively, further confirming the alloying of RuCo. In addition, the particles are coated with 2 to 4 layers of amorphous carbon, which plays a dual role in enhancing conductivity and preventing particle aggregation and deactivation during electrocatalysis, thereby improving structural stability.

[0104] Selected area electron diffraction image: The selected area electron diffraction image of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 is as follows: Figure 9 As shown, it was found that the interplanar spacings of 0.177 and 0.125 nm, and 0.225 and 0.180 nm determined by the diffraction spots correspond to the (200) and (220) planes of Co, and the (100) and (103) planes of RuCo, respectively, confirming the formation of a RuCo alloy structure.

[0105] X-ray diffraction pattern: Figure 10X-ray diffraction patterns of the Co-BDC-NH2 precursor, RuCo-BDC-NH2 precursor and two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1, and the Co / NC nanomaterial prepared in Comparative Example 1. 3+ The diffraction peak position and intensity of the Co-BDC-NH2 template did not change significantly after the reaction, indicating that Ru 3+ Co 2+ Direct cation exchange and Ru in C2H5OH solution 3+ Weak hydrolysis-induced indirect H + Etching does not destroy the long-range ordered structure of Co MOFs, and Co / NC shows diffraction peaks at 36.8°, 44.4°, and 51.3°, corresponding to the (311) crystal plane of Co3O4, the (111) and (200) crystal planes of Co, respectively. The derivative peak intensity at 44.4° is the highest, indicating that Co-BDC-NH2 will be converted into carbon-supported Co nanoparticles under a reducing atmosphere. The higher surface energy will cause it to be oxidized by air into stable Co3O4, forming a metal@metal oxide core-shell structure. 3+ After the introduction of Ru, the diffraction peaks attributed to the (311) crystal plane of Co3O4 and the (200) crystal plane of Co disappeared, while the diffraction peak intensity attributed to the (111) crystal plane of Co decreased and the half-peak width increased, indicating that the crystallinity of the sample deteriorated and the particle size decreased. This confirms that Ru was incorporated into the Co lattice or that Ru and Co bonded to form a RuCo alloy. The presence of Ru effectively inhibited the surface oxidation of Co, and no Co3O4 phase precipitated in the sample. In addition, the RuCo / NC did not show characteristic diffraction peaks attributed to Ru, which may be related to the low Ru content.

[0106] X-ray photoelectron spectroscopy: Figure 11 (a) is the full XPS spectrum of RuCo / NC prepared in Example 1 and Co / NC prepared in Comparative Example 1. RuCo / NC has Ru 3p orbital characteristic peaks at 285.06 and 462.49 eV, indicating that Ru was successfully introduced. Figure 11 (b) is the Co 2p fine spectrum of RuCo / NC prepared in Example 1. The 780.56 eV and 782.29 eV in RuCo / NC correspond to the 2p 3 / 2 Track Co 0 and Co 2+ The fitted peak shifts toward higher binding energy compared to Co / NC, indicating that the Co site in RuCo / NC exhibits a reduced electron cloud density, and the increase in Co valence is conducive to coupling with oxygen-containing intermediate species to generate CoOOH active phase during the OER process. Figure 11 (c) is the Ru 3p fine spectrum of RuCo / NC prepared in Example 1, with metallic Ru 0and oxidation state Ru 4+ Coexistence of forms. Figure 11 (d) is the N1s fine spectrum of RuCo / NC prepared in Example 1. The pyridinic N content in RuCo / NC is as high as 44.86%. The electron-rich pyridinic N can optimize the adsorption of H*, thereby reducing the energy barrier of the water dissociation step in the alkaline HER process, making RuCo / NC show a significant HER advantage over Co / NC.

[0107] N2 isothermal adsorption / desorption measurement curve and pore size distribution: The N2 isothermal adsorption / desorption measurement curve and pore size distribution of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 are shown in FIG. Figure 12 As shown in Figure 2, the specific surface area of ​​RuCo / NC is as high as 203.53 m 2 g -1 , which facilitates full exposure of active sites. Thanks to the scission of organic ligands during pyrolysis and their conversion into small molecule gases, RuCo / NC exhibits a rich micro- and mesoporous structure, as evidenced by the presence of a distinct type IV adsorption isotherm hysteresis loop within the relative pressure range of 0.50 to 0.99 Pa. Furthermore, the pore size of RuCo / NC is concentrated at 10.7 nm. The larger mesopore size facilitates full contact between the electrocatalyst and the electrolyte, thereby optimizing the electrocatalytic OER reaction kinetics.

[0108] Test Example 2

[0109] The performance of hydrogen and oxygen evolution was tested as follows: In a typical three-electrode system, a carbon rod and Ag / AgCl (containing a saturated KCl aqueous solution) were used as the counter electrode and the reference electrode, respectively. The working electrode was prepared as follows: 5 mg of the catalyst sample was dispersed in 500 μL of C2H5OH (containing 15 μL of Nafion), ultrasonicated for 0.5 h to obtain a mixed slurry, and 100 μL of the slurry was drop-coated on a 1×1 cm 2 The pretreated CP was loaded with 1 mg cm -2 ).

[0110] The catalyst samples are: the two-dimensional MOF-derived RuCo / NC nanocomposite materials prepared in Examples 1-7, the nanomaterials prepared in Comparative Examples 1-2, and commercially available Pt / C with a Pt content of 20 wt%.

[0111] All electrochemical tests in this invention were conducted on a CHI 660 electrochemical workstation. The 1.0M KOH aqueous solution used in the electrochemical test required pre-nitrogen flow for 30 minutes to remove oxygen. The carbon paper used required surface pretreatment with a mixture of concentrated sulfuric acid and concentrated nitric acid to remove oxides and impurities. The actual area immersed in the electrolyte was 1 cm 2 The scan rate of the linear polarization curve was set to 5 mV·s -1, and a stable polarization curve was obtained after scanning 20 times.

[0112] Electrochemical impedance spectroscopy (EIS) was obtained at a DC potential (-322 mV vs. RHE for HER and 1.704 V vs. RHE for OER), corresponding to a current density of 10 mA cm in the LSV curves of HER and OER. -2 The test frequency is 0.01~100000Hz, and the amplitude is 0.005V.

[0113] The Tafel curve is obtained by iR-compensated linear polarization curve, and the selected range is the Faraday range where hydrogen and oxygen evolution occur.

[0114] Double layer capacitance (C dl ) by scanning the HER non-Faradaic range (0.724-0.824 V vs. RHE) and the OER non-Faradaic range (1.224-1.324 V vs. RHE) at different scan rates (5-40 mV s -1 , with an interval of 5mV s -1 ) was tested and calculated.

[0115] The electrochemical hydrogen and oxygen production performance test results of the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1, the Co / NC nanomaterial prepared in Comparative Example 1, and commercially available Pt / C with a Pt content of 20 wt% and RuO2 are as follows:

[0116] The hydrogen and oxygen evolution performances of the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1 are as follows: Figure 13 and Figure 14 shown. Figure 13 (a) and 14 (a) are linear polarization curves (LSV). It can be seen from the figure that the optimized RuCo / NC exhibits excellent HER in 1.0 M KOH electrolyte (overpotential 59 mV@10 mA cm -2 ) and OER (overpotential 248 mV@10 mA cm -2 ) electrocatalytic performance, and Co / NC requires overpotentials as high as 225 mV and 390 mV to achieve 10 mA cm -2 The current density of the electrocatalyst is shown to be 0.0447 W·m-1, which indicates that the RuCo alloying strategy adopted in the present invention can improve the intrinsic catalytic activity of the electrocatalyst for hydrogen evolution and oxygen evolution.

[0117] The Tafel curve is obtained by iR-compensated linear polarization curve, and the selected range is the Faraday interval where hydrogen and oxygen evolution occur. Figure 13 (b) and 14(b) show that the Tafel slope of hydrogen evolution of Co / NC is as high as 198.9 mV dec. -1, while RuCo / NC only has 68.5mV dec -1 , indicating that RuCo alloying optimizes the HER reaction kinetics of the electrocatalyst and achieves rapid hydrogen production at high current density. The Tafel slope of oxygen evolution of Co / NC is as high as 88.6mV dec -1 , while the Tafel slope of RuCo / NC is only 63.8mVdec -1 , indicating that RuCo / NC has both excellent OER intrinsic activity and reaction kinetics.

[0118] Double layer capacitance (C dl ) by scanning the HER non-Faradaic range (0.724-0.824 V vs. RHE) and the OER non-Faradaic range (1.224-1.324 V vs. RHE) at different scan rates (5-40 mV s -1 , with an interval of 5mV s -1 ) CV test and calculation are performed. The double layer capacitance of the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1 is shown in the figure. Figure 13 (c) and 14(c), the C of RuCo / NC dl The values ​​were as high as 164.39mF cm -2 and 160.35mF cm -2 , C of Co / NC dl The value is only 2.97mF cm -2 and 14.84 mF cm -2 , while those of RuCo / NC are as high as 30.34 mF cm -2 and 27.64mF cm -2 , that is, RuCo alloying increases the ECSA of hydrogen evolution of the electrocatalyst by 9.2 times, indicating that the excellent HER electrocatalytic activity of RuCo / NC is determined by the abundant active sites. It also increases the ECSA of oxygen evolution of Co / NC to a certain extent, thereby promoting the exposure of active sites.

[0119] Electrochemical impedance spectroscopy (EIS) was obtained at a DC potential (-322 mV vs. RHE for HER and 1.704 V vs. RHE for OER), corresponding to a current density of 10 mA cm in the LSV curves of HER and OER. -2 The potential of the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1 is shown in the following figure. Figure 13 (d) and 14 (d), it can be seen from the figure that the charge transfer resistance (R ct) were as high as 20.11Ω and 15.98Ω, respectively, while those of Ru-Co / NC were only 12.94Ω and 1.958Ω, which means that RuCo alloying makes the R of hydrogen evolution and oxygen evolution of the electrocatalyst ct The RuCo alloying significantly improved the electrical conductivity of Co / NC and achieved efficient surface / interface electron transfer during the electrocatalytic OER process.

[0120] In the cyclic stability test, the linear polarization curves of hydrogen and oxygen evolution of the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1 were tested before and after 3000 CV scans. Figure 13 (e) with Figure 14 (e) As shown in the figure, it is found that after CV test, Ru-Co / NC is -2 The hydrogen evolution potential under the current density was only negatively shifted by 11 mV, and the almost overlapping linear polarization curves of oxygen evolution and hydrogen evolution indicated excellent cyclic stability of hydrogen and oxygen evolution.

[0121] In the long-term stability test, the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1 was -2 The following test constant current stability test is as follows Figure 13 As shown in Figures 14(f) and 14(f), after 100 h of continuous electrolysis, 88.11% of the initial voltage for hydrogen evolution and 98.69% of the initial voltage for oxygen evolution can be maintained, indicating that it has excellent long-term stability for both hydrogen and oxygen evolution.

[0122] Comparison of the electrocatalytic hydrogen and oxygen evolution performance of the two-dimensional MOF-derived RuCo / NC nanocomposites prepared in Examples 1-7 and the nanomaterials prepared in Comparative Example 2 Figure 15 and Figure 16 As shown, it can be seen from the linear polarization curves of Example 1 and other samples that the two-dimensional MOF-derived RuCo / NC nanocomposite material prepared in Example 1 of the present invention has more efficient full water splitting performance.

[0123] Test Example 3

[0124] The test method for complete water splitting is as follows: In a typical two-electrode system, the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 serves as both the cathode and the anode, and the working electrode is prepared in the same manner as in the three-electrode system. For comparison, 20% Pt / C and RuO2 are used as the cathode and anode, respectively, and the electrode preparation method is the same as above. The electrolyte used in the electrochemical test is a 1.0M KOH aqueous solution, which needs to be pre-gassed with nitrogen for 30 minutes to remove oxygen; the carbon paper used needs to be pre-treated with a mixture of concentrated sulfuric acid and concentrated nitric acid to remove oxides and impurities, and the actual area immersed in the electrolyte is 1 cm 2 The two-electrode test for complete water splitting was performed in the potential range of 0 to 2 V, and the scan rate of the linear polarization curve was set to 5 mV·s -1 .

[0125] The results of the full water decomposition performance test are as follows:

[0126] The overall water splitting performance of the two-dimensional MOF-derived RuCo / NC nanocomposite obtained in Example 1, the Co / NC nanocomposite prepared in Comparative Example 1, and the commercially available Pt / C with a Pt content of 20 wt% and RuO2 is shown in FIG. Figure 17 As shown in a, RuCo / NC|RuCo / NC can achieve 10 mA cm with only 1.523 V applied voltage. -2 The current density of RuCo / NC||RuCo / NC is 0.308V less than that of Co / NC||Co / NC for water splitting, indicating that RuCo / NC has excellent potential for electrocatalytic water splitting. Figure 17 As shown in b, it is reflected in 10mA cm -2 After 15 h of continuous electrolysis at a constant current density of 1.5 wt %, the activity still retained 98%.

[0127] Test Example 4

[0128] The two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 was subjected to LSV tests in pure water OWS at different temperatures (25°C, 60°C, 70°C, and 80°C) using a homemade simplified PEM membrane electrode assembly to simulate its applicability under different PEM operating conditions. The working electrode was prepared as follows: 10 mg of the RuCo / NC prepared in Example 1 was dispersed in a mixed solution of 930 μL C2H5OH and 70 μL Nafion. The mixed slurry was ultrasonicated for 0.5 h to obtain a mixed slurry, and 400 μL of the slurry was drop-coated onto a pretreated 2×2 cm carbon paper (ensuring a loading of 1 mg cm). -2); the cathode and anode were obtained respectively. For comparison, 5 mg of 20% Pt / C was dispersed in a mixed solution of 465 μL C2H5OH and 35 μL Nafion, and 4 mg of RuO2 was dispersed in a mixed solution of 1972 μL C2H5OH and 28 μL Nafion. Both were sonicated for 0.5 h, and 400 μL of the slurry was drop-coated on a 2×2 cm pre-treated CP (ensuring a loading of 1 mg cm). -2 ), and obtained comparative cathode and anode, respectively.

[0129] Figure 18 (a) Schematic diagram of the membrane electrode assembly (MEA), which consists of a Nafion membrane, cathode and anode, diffusion layer, and end plates. The Nafion membrane effectively separates the cathode HER and anode OER reactions, while nickel foam (NF) acts as a diffusion layer, current collector, and support. Figure 18 b is the LSV curve of pure water OWS at different temperatures for RuCo / NC / NF‖RuCo / NC / NF (the two-dimensional MOF-derived RuCo / NC nanocomposite prepared in Example 1 is used as cathode and anode), 20% Pt / C / NF‖RuO2 / NF (20% Pt / C and RuO2 are used as cathode and anode respectively) and NF‖NF (cathode and anode omitted). It was found that the performance of NF‖NF was the worst and was almost unaffected by the test temperature, confirming that NF only played an auxiliary role. The performance of 20% Pt / C / NF‖RuO2 / NF was the best, but the degree of performance improvement was small as the test temperature increased. Although the performance of RuCo / NC / NF‖RuCo / NC / NF at 25°C was far inferior to that of 20% Pt / C / NF‖RuO2 / NF, the gap between the two could be significantly narrowed by increasing the temperature. Specifically, from the applied potential comparison bar graph ( Figure 18 c) It can be seen that the difference in applied voltage required to achieve 100 mA between RuCo / NC / NF‖RuCo / NC / NF and 20% Pt / C / NF‖RuO2 / NF is reduced from 1.151 V at 25°C to 0.268 V at 70°C, that is, RuCo / NC / NF‖RuCo / NC / NF only requires 1.881 V to achieve 100 mA at 70°C, indicating that under the actual working conditions of PEM pure water electrolysis for hydrogen production, RuCo / NC can even achieve OWS catalytic activity comparable to that of commercial water electrolysis materials, and has excellent industrial application value.

[0130] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. Application of a two-dimensional MOF-derived RuCo / NC nanocomposite in electrolytic water oxygen evolution or electrocatalytic water splitting, characterized in that: The RuCo / NC nanocomposite material is a composite porous material of RuCo alloy and nitrogen-doped carbon; the microscopic morphology of the composite material is: RuCo alloy nanoparticles coated with nitrogen-doped carbon are uniformly supported on the porous nitrogen-doped carbon with a hexagonal sheet structure; The preparation method of the two-dimensional MOF-derived RuCo / NC nanocomposite material comprises the following steps: (1) The inorganic cobalt source and the organic ligand are fully dispersed in an organic solvent, subjected to a hydrothermal reaction, centrifuged, and dried to obtain a metal organic framework Co-BDC-NH2 precursor; the inorganic cobalt source is cobalt nitrate hexahydrate, and the organic ligand is 2-aminoterephthalic acid; the organic solvent is a mixed solvent of methanol and N,N-dimethylformamide; the volume ratio of methanol to N,N-dimethylformamide in the mixed solvent is 1:1-3; the hydrothermal reaction time is 22-26 h; and the hydrothermal reaction temperature is 80-120°C; (2) The metal organic framework Co-BDC-NH2 precursor and the ruthenium source are fully dispersed in a solvent, subjected to a hydrothermal reaction, centrifuged, and dried to obtain a RuCo-BDC-NH2 precursor; the solvent is ethanol, and the ruthenium source is anhydrous ruthenium trichloride; the mass ratio of the metal organic framework Co-BDC-NH2 precursor to the ruthenium source is 10:1; the hydrothermal reaction temperature is 60-120°C; and the hydrothermal reaction time is 8-16 hours; (3) The RuCo-BDC-NH2 precursor was annealed to obtain a two-dimensional MOF-derived RuCo / NC nanocomposite material; the annealing temperature was 500°C, the annealing time was 1 h, and the annealing was carried out under the protection of an inert gas; the inert gas was nitrogen or argon.

2. The use according to claim 1, characterized in that The RuCo / NC nanocomposite material has a pyridine N content of 40-50 wt% and a specific surface area of ​​150-250 m 2 / g; pore size is 2-40nm.

3. The use according to claim 1, characterized in that The particle size of nitrogen-doped carbon-coated RuCo alloy nanoparticles is 3~6nm; the size of porous nitrogen-doped carbon with hexagonal sheet structure is 3~5μm.

4. The use according to claim 1, characterized in that In step (1), the volume ratio of the amount of the organic ligand to the organic solvent is 0.01-0.0.25 mol / L.

5. The use according to claim 1, characterized in that In step (2), the mass ratio of the metal organic framework Co-BDC-NH2 precursor to the volume ratio of the solvent is 1-10 mg / mL.

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