Double-MOFs-derived metal phosphide composite material with hollow hierarchical structure as well as preparation method and application of double-MOFs-derived metal phosphide composite material

Abstract

The invention relates to a preparation method and application of a metal phosphide composite material with a hollow hierarchical structure and derived from double MOFs, and belongs to the technical field of electro-catalytic materials. The preparation method comprises the following steps: synthesizing hollow main body MOFs by adopting a soft template method; synthesizing MOFs (at) MOFs with a hollow hierarchical structure; pyrolyzing and carbonizing; and carrying out phosphating reaction to obtain the metal phosphide composite material which is derived from the double MOFs and has a hollow hierarchical structure, namely FeP-ZnCoP-C. The metal phosphide composite material which is derived from double MOFs and has a hollow hierarchical structure is synthesized by adopting a strategy of MOFs-on-MOFs and utilizing a solvothermal method and a phosphating combined method, the material provides more active sites, and meanwhile, the catalytic performance is improved by utilizing the synergistic effect of different components, so that the limitation of single MOFs is solved, and the metal phosphide composite material has a good application prospect. The hydrogen evolution performance is excellent, and a new thought is provided for preparing a non-noble metal-based water decomposition electrocatalyst.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and in particular to a metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs, its preparation method, and its application. Background Technology

[0002] The energy shortage caused by the combustion of fossil fuels and the environmental pollution caused by carbon emissions are becoming increasingly serious problems. To address these issues, the demand for renewable energy has surged in recent years. Among numerous new energy sources, hydrogen energy is considered the most promising alternative to fossil fuels due to its renewable and environmentally friendly characteristics. Among various hydrogen production methods, water electrolysis offers advantages such as high purity, environmental friendliness, and large-scale application, making it a promising candidate for widespread use. Currently, commercially available hydrogen production catalysts are platinum-carbon catalysts (Pt / C). While they exhibit good performance, their high cost limits their future application. Furthermore, the catalytic activity of platinum-carbon catalysts is affected by the pH of the environment, showing greater advantages in acidic environments and relatively weaker catalytic activity in alkaline environments. Therefore, developing a low-cost electrocatalytic hydrogen evolution material that maintains high catalytic activity even under alkaline conditions is particularly important.

[0003] Metal-organic frameworks (MOFs) possess high specific surface areas, rich and tunable pore structures, and surfaces that are easily functionalized, making them widely applicable as electrocatalysts in catalysis and energy storage. However, single MOF materials have certain limitations and therefore typically exhibit poor catalytic performance. Generally, the performance of a material is highly dependent on its structure and composition; therefore, current research primarily focuses on modifying the structure or composition of different MOF materials to improve their performance.

[0004] Application No. 202410067506.8 discloses a composite photocatalyst with a dual MOF structure and its preparation method. The method first prepares ZIF-8 and Bi-MOF using a solvothermal method, then halogenates Bi-MOF with ammonium bromide and grows ZIF-8 in situ. Finally, a one-step calcination method is used to obtain a composite photocatalyst with a dual MOF structure consisting of zinc oxide particles with a dodecahedral structure derived from ZIF-8 and bismuth oxybromide derived from Bi-MOF. This catalyst compensates for the limitations of single MOF materials and improves catalytic performance.

[0005] This invention utilizes a MOFs-on-MOFs growth process to conjugate two MOFs with different compositions or structures, thereby producing complex, well-designed MOFs hybrid materials with unique properties to compensate for the limitations of single MOFs materials. Summary of the Invention

[0006] The purpose of this invention is to provide a hollow hierarchical metal phosphide composite material derived from dual MOFs and its preparation method. By adopting a "MOFs-on-MOFs" strategy, the hollow hierarchical metal phosphide composite material derived from dual MOFs is synthesized using a combination of solvothermal and phosphating methods. This material provides more active sites, and at the same time, the synergistic effect between different components is used to improve catalytic performance, thereby overcoming the limitations of single MOFs. It has excellent hydrogen evolution performance and provides a new approach for the preparation of non-noble metal-based water splitting electrocatalysts.

[0007] Another object of the present invention is to provide the application of the above-mentioned double MOF-derived hollow hierarchical metal phosphide composite material in electrocatalytic hydrogen evolution.

[0008] To achieve the above objectives, the present invention specifically adopts the following technical solution: A method for preparing a metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs includes the following steps: (1) Synthesis of hollow bulk NH2-MIL-88: Solid NH2-MIL-88 (MIL) nanoparticles were synthesized using FeCl3·6H2O, NH2-H2BDC and polyvinylpyrrolidone (PVP). (2) Synthesis of hollow MIL@ZIFs: The MIL nanoparticles obtained in step (1) were dispersed in an organic solvent, and then Co(NO3)2·6H2O, Zn(NO3)2·6H2O and 2-methylimidazole were added in sequence. After the reaction was completed, the solid product MIL@ZIFs was obtained by centrifugation, washing and drying. (3) Pyrolysis carbonization Under an inert atmosphere, the solid product of MIL@ZIFs obtained in step (2) was calcined and then cooled to room temperature to obtain MIL@ZIFs-oxide material; (4) Phosphating reaction Sodium hypophosphite and the MIL@ZIFs-oxide catalyst obtained in step (3) were placed in a glass tube, and then the glass tube was placed in a tube furnace. Sodium hypophosphite was placed near the gas inlet of the tube furnace, and MIL@ZIFs-oxide catalyst was placed near the gas outlet of the tube furnace. Under an inert atmosphere, the temperature was raised to the third temperature and held for a period of time, and then cooled to room temperature to obtain the phosphated FeP-ZnCoP@C composite material.

[0009] Further, step (1) specifically includes: adding FeCl3·6H2O to DMF solvent, sonicating and stirring at room temperature to obtain solution A; adding NH2-H2BDC and polyvinylpyrrolidone (PVP) to solution A and stirring at room temperature to obtain a mixed solution; then transferring the above mixed solution to a glass flask, placing the glass flask in an oil bath and refluxing it with stirring; then, after cooling to room temperature, centrifuging is performed, and the separated solids are washed with DMF and anhydrous ethanol respectively, and dried in a vacuum drying oven to obtain solid NH2-MIL-88 nanoparticles (abbreviated as MIL).

[0010] Further, in step (1), the mass ratio of FeCl3·6H2O, NH2-H2BDC and PVP is (0.10-0.20): (0.08-0.12): (0.25-0.30).

[0011] Further, in step (1), all stirring is done using magnetic stirring, with a stirring speed of 400-600 r / min and a stirring time of 1 ± 0.5 h; the reflux reaction temperature is 140-150℃ and the reflux reaction time is 2 ± 0.5 h; the centrifugation speed is 7000-10000 r / min and the centrifugation time is 4-8 min; the vacuum drying temperature is controlled at 50-80℃ and the vacuum drying time is 10-14 h.

[0012] Furthermore, in step (1), the reflux reaction temperature is 145℃; the centrifugation speed is 8000 r / min.

[0013] Furthermore, the organic solvent in step (2) is methanol.

[0014] Step (2) specifically includes: dispersing the MIL nanoparticles obtained in step (1) into methanol and stirring at room temperature to obtain a mixed solution; adding Co(NO3)2·6H2O and Zn(NO3)2·6H2O into the above mixed solution and stirring at room temperature to obtain solution B; then adding 2-methylimidazole into the above solution B, and after completing the reaction at room temperature with stirring, centrifuging, washing with methanol, and vacuum drying to obtain the MIL@ZIFs solid product.

[0015] Further, in step (2), the mass ratio of MIL, Co(NO3)2·6H2O, Zn(NO3)2·6H2O and 2-methylimidazole is (0.004-0.008): (0.010-0.013): (0.002-0.004): (0.050-0.070).

[0016] Furthermore, in step (2), all stirring is done using magnetic stirring, with a stirring speed of 400-600 r / min and a stirring time of 20-25 h; the reaction temperature is 25℃±5℃, the stirring speed is 400-600 r / min, and the reaction time is 40±10 min; the centrifugation speed is 6000-9000 r / min, the centrifugation time is 4-8 min, and the vacuum drying temperature is controlled at 50-80℃, with a vacuum drying time of 10-14 h.

[0017] Further, in step (3), a staged calcination is adopted, specifically including: firstly, heating to a first temperature of 100-300℃ at a heating rate of 5±0.5℃ / min, and holding at the first temperature for 1±0.5 h; then heating to a second temperature of 400-600℃ at a heating rate of 5±0.5℃ / min, and holding at the second temperature for 2±0.5 h.

[0018] Furthermore, in step (3), the first temperature is 200°C and the second temperature is 500°C.

[0019] Furthermore, in step (3), the inert atmosphere is N2.

[0020] Furthermore, in step (4), the mass ratio of sodium hypophosphite to MIL@ZIFs-oxide catalyst is (1.50-3.00): (0.06-0.07).

[0021] Further, in step (4), the glass tube is placed in the following manner: the sodium hypophosphite is placed near the gas inlet of the tube furnace so that the PH3 generated by the pyrolysis of sodium hypophosphite and the downstream sample undergo a phosphating reaction.

[0022] Furthermore, in step (4), the inert atmosphere is N2.

[0023] Further, in step (4), the temperature is increased to a third temperature at a rate of 5±5℃ / min, and held at the third temperature for 2±0.5 h, wherein the third temperature is 300-400℃.

[0024] Furthermore, in step (4), the third temperature is 350°C.

[0025] The present invention also provides a metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs prepared by the above preparation method, which is the above-mentioned phosphated FeP-ZnCoP@C composite material.

[0026] This invention also provides the application of the above-mentioned double MOFs-derived hollow hierarchical metal phosphide composite material as a catalyst in electrocatalytic hydrogen evolution.

[0027] The beneficial effects of this invention are as follows: 1. The preparation method of the metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs of the present invention uses a soft template method to pre-synthesize hollow host MOFs, avoiding the tedious process of template removal later. The present invention employs a combination of solvothermal method and phosphating, which is simple to operate, low in cost, and suitable for large-scale use. In addition, the hollow hierarchical structure is beneficial for exposing more active sites, improving the utilization rate of active sites, and effectively shortening the mass transfer distance.

[0028] 2. The metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs prepared in this invention can improve catalytic performance by utilizing the synergistic effect between different components, thus overcoming the limitations of a single component; the strong heterogeneous electronic interaction around the heterogeneous interface can effectively regulate the electronic state of the material, thereby optimizing the adsorption / desorption of H2O and the adsorption of protons in the alkaline HER process, which is beneficial to the hydrogen evolution reaction.

[0029] 3. When the metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs prepared in this invention is used as a catalyst for the electrocatalytic hydrogen evolution reaction, it achieves a viscosity of 10 mA cm⁻¹. -2 The overpotential required for this current density is only 75 mV, and the Tafel slope is 39.5 mV dec. -1 It exhibits good hydrogen evolution performance. Attached Figure Description

[0030] Figure 1 These are electron microscope images of different MOF materials, among which Figure 1 (a) and (b) are SEM and TEM images of NH2-MIL-88 prepared in step (1) of Example 1 according to the present invention, respectively; Figure 1 (c) is a SEM image of the ZnCo-ZIFs prepared in step (1) of Comparative Example 2; Figure 1 (d) is a SEM image of MIL@ZIFs prepared in step (2) of Example 1; Figure 2 The XRD patterns are those of NH2-MIL-88 prepared in step (1) of Example 1 according to the present invention, ZnCo-ZIFs prepared in step (1) of Comparative Example 2, and MIL@ZIFs prepared in step (2) of Example 1. Figure 3 The infrared spectra (FT-IR) of NH2-MIL-88 prepared in step (1) of Example 1, ZnCo-ZIFs prepared in step (1) of Comparative Example 2, and MIL@ZIFs prepared in step (2) of Example 1 are shown. Figure 4This is an XRD pattern of the FeP-ZnCoP@C composite material according to Example 1 of the present invention; Figure 5 These are electron microscope images of the FeP-ZnCoP@C composite material according to Example 1 of the present invention; wherein (a) is a SEM image and (b) is a TEM image; Figure 6 This is a mapping elemental distribution diagram of the FeP-ZnCoP@C composite material according to Example 1 of the present invention; Figure 7 These are HER performance graphs of the catalysts of Example 1, Comparative Example 1, Comparative Example 2 and commercially available Pt / C (20%) according to the present invention; wherein (a) is the LSV curve of HER and (b) is the Tafel plot of HER. Figure 8 This is a stability test diagram of the hydrogen evolution electrochemical reaction of the FeP-ZnCoP@C composite material according to Example 1 of the present invention. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Unless otherwise specified, all raw materials, reagents and testing instruments used in this invention are commercially available products.

[0033] Unless otherwise specified, the term "room temperature" as used in this invention refers to the indoor temperature under normal conditions, approximately between 20°C and 25°C.

[0034] As used herein, unless otherwise specified, numerical ranges include both the beginning and end values ​​of the range. For example, when a temperature is described as "140-150°C", this means that both 140°C and 150°C are valid values ​​for that temperature.

[0035] Example 1: Preparation of FeP-ZnCoP@C composite material with hollow hierarchical structure A method for preparing a metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs includes the following steps: (1) Synthesis of hollow NH2-MIL-88 0.150 g FeCl3·6H2O was added to 10 mL DMF solvent, sonicated for 5 min, and magnetically stirred at 500 r / min for 10 min at room temperature to obtain solution A. 0.10 g NH2-H2BDC and 0.29 g polyvinylpyrrolidone were added to solution A, and the mixture was magnetically stirred at 500 r / min for 1 h at room temperature until completely dissolved to obtain a mixed solution. The mixed solution was then transferred to a glass flask, placed in an oil bath, and refluxed at 145 °C with magnetic stirring at 500 r / min for 2 h. After naturally cooling to room temperature, the mixture was centrifuged at 8000 r / min for 5 min. The separated solid was washed twice with DMF and anhydrous ethanol, and dried in a vacuum drying oven at 80 °C for 12 h to obtain solid NH2-MIL-88 nanoparticles (referred to as MIL nanoparticles).

[0036] (2) Synthesis of hollow MIL@ZIFs 6 mg of the MIL nanoparticles synthesized in step (1) were dispersed in 12 mL of methanol and magnetically stirred at 500 r / min for 30 min at room temperature to obtain a mixed solution. 12 mg of Co(NO3)2·6H2O and 3.5 mg of Zn(NO3)2·6H2O were added to the above mixed solution and magnetically stirred at 500 r / min for 24 h at room temperature to obtain solution B. Then 60 mg of 2-methylimidazole was added to the above solution B and stirred at 500 r / min for 40 min at room temperature. After centrifugation, the mixture was washed three times with methanol and vacuum dried in a vacuum drying oven at 80 °C for 12 h to obtain a brown MIL@ZIFs solid product.

[0037] (3) Pyrolysis carbonization The solid product of MIL@ZIFs synthesized in step (2) was placed in a tube furnace for pyrolysis reaction to carbonize the organic ligands in MOFs. N2 was introduced as a protective gas, and the temperature was raised to 200℃ at a heating rate of 5℃ / min and held for 1 h. Then the temperature was raised to 500℃ at the same heating rate and held for 2 h. After cooling to room temperature, the product was taken out to obtain MIL@ZIFs-oxide material.

[0038] (4) Phosphating reaction Sodium hypophosphite and the MIL@ZIFs-oxide material obtained in step (3) were placed in a quartz glass tube at a mass ratio of 30:1. The glass tube was placed in a tube furnace, with the sodium hypophosphite near the gas inlet of the tube furnace and the MIL@ZIFs-oxide material near the gas outlet of the tube furnace. Inert gas N2 was introduced, and the temperature was raised to 350°C at a rate of 5°C / min. After holding at this temperature for 2 h and cooling to room temperature, the phosphated FeP-ZnCoP@C composite material was obtained.

[0039] Example 2: Preparation of hollow hierarchical FeP-ZnCoP@C composite material A method for preparing a metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs includes the following steps: (1) Synthesis of hollow NH2-MIL-88 0.10 g FeCl3·6H2O was added to 10 mL DMF solvent, sonicated for 5 min, and magnetically stirred at 500 r / min for 10 min at room temperature to obtain solution A. 0.08 g NH2-H2BDC and 0.25 g polyvinylpyrrolidone were added to solution A, and the mixture was magnetically stirred at 500 r / min for 1 h at room temperature until completely dissolved to obtain a mixed solution. Subsequently, the above mixed solution was transferred to a glass flask, which was placed in an oil bath and refluxed at 145 °C with magnetic stirring at 500 r / min for 2 h. After naturally cooling to room temperature, the mixture was centrifuged at 8000 r / min for 5 min. The separated solid was washed twice with DMF and anhydrous ethanol, and dried in a vacuum drying oven at 80 °C for 12 h to obtain solid NH2-MIL-88 nanoparticles (referred to as MIL nanoparticles).

[0040] (2) Synthesis of hollow MIL@ZIFs 4 mg of the MIL nanoparticles synthesized in step (1) were dispersed in 12 mL of methanol and magnetically stirred at 500 r / min for 30 min at room temperature to obtain a mixed solution. 10 mg of Co(NO3)2·6H2O and 2.0 mg of Zn(NO3)2·6H2O were added to the above mixed solution and magnetically stirred at 500 r / min for 24 h at room temperature to obtain solution B. Then 50 mg of 2-methylimidazole was added to the above solution B and stirred at 500 r / min for 40 min at room temperature. After centrifugation, the mixture was washed three times with methanol and vacuum dried in a vacuum drying oven at 80 °C for 12 h to obtain a brown MIL@ZIFs solid product.

[0041] (3) Pyrolysis carbonization The solid product of MIL@ZIFs synthesized in step (2) was placed in a tube furnace for pyrolysis reaction to carbonize the organic ligands in MOFs. N2 was introduced as a protective gas, and the temperature was raised to 200℃ at a heating rate of 5℃ / min and held for 1 h. Then the temperature was raised to 500℃ at the same heating rate and held for 2 h. After cooling to room temperature, the product was taken out to obtain MIL@ZIFs-oxide material.

[0042] (4) Phosphating reaction Sodium hypophosphite and the MIL@ZIFs-oxide material obtained in step (3) were placed in a quartz glass tube at a mass ratio of 25:1. The glass tube was placed in a tube furnace, with the sodium hypophosphite near the gas inlet of the tube furnace and the MIL@ZIFs-oxide material near the gas outlet of the tube furnace. Inert gas N2 was introduced, and the temperature was raised to 350°C at a rate of 5°C / min. After holding at this temperature for 2 h and cooling to room temperature, the phosphated FeP-ZnCoP@C composite material was obtained.

[0043] Example 3: Preparation of FeP-ZnCoP@C composite material with hollow hierarchical structure A method for preparing a metal phosphide composite material with a hollow hierarchical structure derived from dual MOFs includes the following steps: (1) Synthesis of hollow NH2-MIL-88 0.20 g FeCl3·6H2O was added to 10 mL DMF solvent, sonicated for 5 min, and magnetically stirred at 500 r / min for 10 min at room temperature to obtain solution A. 0.12 g NH2-H2BDC and 0.30 g polyvinylpyrrolidone were added to solution A, and the mixture was magnetically stirred at 500 r / min for 1 h at room temperature until completely dissolved to obtain a mixed solution. The mixed solution was then transferred to a glass flask, placed in an oil bath, and refluxed at 145 °C with magnetic stirring at 500 r / min for 2 h. After naturally cooling to room temperature, the mixture was centrifuged at 8000 r / min for 5 min. The separated solid was washed twice with DMF and anhydrous ethanol, and dried in a vacuum drying oven at 80 °C for 12 h to obtain solid NH2-MIL-88 nanoparticles (referred to as MIL nanoparticles).

[0044] (2) Synthesis of hollow MIL@ZIFs 8 mg of the MIL nanoparticles synthesized in step (1) were dispersed in 12 mL of methanol and magnetically stirred at 500 r / min for 30 min at room temperature to obtain a mixed solution. 13 mg of Co(NO3)2·6H2O and 4.0 mg of Zn(NO3)2·6H2O were added to the above mixed solution and magnetically stirred at 500 r / min for 24 h at room temperature to obtain solution B. Then 70 mg of 2-methylimidazole was added to the above solution B and stirred at 500 r / min for 40 min at room temperature. After centrifugation, the mixture was washed three times with methanol and vacuum dried in a vacuum drying oven at 80 °C for 12 h to obtain a brown MIL@ZIFs solid product.

[0045] (3) Pyrolysis carbonization The solid product of MIL@ZIFs synthesized in step (2) was placed in a tube furnace for pyrolysis reaction to carbonize the organic ligands in the MOF. N2 was introduced as a protective gas, and the temperature was raised to 200℃ at a heating rate of 5℃ / min and held for 1 h. Then the temperature was raised to 500℃ at the same heating rate and held for 2 h. After cooling to room temperature, the product was taken out to obtain MIL@ZIFs-oxide catalyst material.

[0046] (4) Phosphating reaction Sodium hypophosphite and the MIL@ZIFs-oxide material obtained in step (3) were placed in a quartz glass tube at a mass ratio of 40:1. The glass tube was placed in a tube furnace, with the sodium hypophosphite near the gas inlet of the tube furnace and the MIL@ZIFs-oxide material near the gas outlet of the tube furnace. Inert gas N2 was introduced, and the temperature was raised to 350°C at a rate of 5°C / min. After holding at this temperature for 2 h and cooling to room temperature, the phosphated FeP-ZnCoP@C composite material was obtained.

[0047] Comparative Example 1: Preparation of Hollow FeP@C Catalyst (1) 0.150 g FeCl3·6H2O was added to 10 mL DMF solvent, sonicated for 5 min, and magnetically stirred at 500 r / min for 10 min at room temperature to obtain solution A; 0.10 g NH2-H2BDC and 0.29 g polyvinylpyrrolidone were added to solution A, and magnetically stirred at 500 r / min for 1 h at room temperature until completely dissolved to obtain a mixed solution; then, the above mixed solution was transferred to a glass flask, the glass flask was placed in an oil bath, and refluxed at 145℃ with magnetic stirring at 500 r / min for 2 h; then, after naturally cooling to room temperature, it was centrifuged at 8000 r / min for 5 min, the separated solid was washed twice with DMF and anhydrous ethanol, and dried in a vacuum drying oven at 80℃ for 12 h to obtain solid NH2-MIL-88 nanoparticles (referred to as MIL nanoparticles).

[0048] (2) The MIL nanoparticles synthesized in step (1) are subjected to pyrolysis reaction in the same way as step (3) of Example 1, so that the organic ligands in MOFs are carbonized, and finally the product MIL-oxide material is obtained.

[0049] (3) Sodium hypophosphite and the MIL-oxide material obtained in step (2) are placed in a quartz glass tube at a mass ratio of 30:1. The glass tube is placed in a tube furnace, with the sodium hypophosphite near the gas inlet of the tube furnace and the MIL-oxide material near the gas outlet of the tube furnace. Inert gas N2 is introduced and the temperature is raised to 350°C at a rate of 5°C / min. After holding at the temperature for 2 hours and cooling to room temperature, phosphated FeP@C material is obtained.

[0050] Comparative Example 2: Preparation of ZnCoP@C catalyst (1) Synthesis of ZnCo-ZIFs 0.24 g Co(NO3)2·6H2O and 0.07 g Zn(NO3)2·6H2O were dispersed in 60 mL of methanol, sonicated until homogeneous, and then 1.2 g 2-methylimidazole was added. The mixture was magnetically stirred at 500 r / min at room temperature for 24 h. Subsequently, it was centrifuged at 8000 rpm / min for 5 min, washed three times with methanol, and dried in a vacuum drying oven at 80℃ for 12 h to obtain purple powder ZnCo-ZIFs solid (ZIFs solid for short).

[0051] (2) The ZIFs solid obtained in step (1) is subjected to pyrolysis reaction according to the same pyrolysis carbonization method in step (3) of Example 1, so that the organic ligands in MOFs are carbonized, and finally the product ZIFs-oxide material is obtained.

[0052] (3) Sodium hypophosphite and the ZIFs-oxide material obtained in step (2) are placed in a quartz glass tube at a mass ratio of 30:1. The glass tube is placed in a tube furnace, with the sodium hypophosphite near the gas inlet of the tube furnace and the ZIFs-oxide material near the gas outlet of the tube furnace. Inert gas N2 is introduced and the temperature is raised to 350°C at a rate of 5°C / min. After holding at the temperature for 2 h and cooling to room temperature, phosphated ZnCoP@C material is obtained.

[0053] Experimental Example Experimental Example 1: Characterization of Material Morphology and Structure Figure 1 These are morphology images of different MOF materials, among which Figure 1 (a) and (b) are SEM and TEM images of NH2-MIL-88 prepared in step (1) of Example 1, respectively; Figure 1 (c) is a SEM image of the ZnCo-ZIFs prepared in step (1) of Comparative Example 2; Figure 1 (d) is a SEM image of MIL@ZIFs prepared in step (2) of Example 1.

[0054] from Figure 1 As can be seen from (a) and 1(b), the host NH2-MIL-88 nanoparticles prepared in step (1) of Example 1 of the present invention have a hollow, uniform octahedral structure. After the hollow hierarchical MIL@ZIFs are synthesized in step (2), the guest ZnCo-ZIFs are uniformly and densely distributed on the surface of MIL, and maintain the original octahedral structure, such as Figure 1 As shown in (d).

[0055] Figure 2 The figures show the XRD patterns of NH2-MIL-88 prepared in step (1) of Example 1, ZnCo-ZIFs prepared in step (1) of Comparative Example 2, and MIL@ZIFs prepared in step (2) of Example 1. As can be seen from the figures, typical characteristic diffraction peaks of ZnCo-ZIFs were detected in MIL@ZIFs, proving that a hierarchical structure of dual MOFs was formed according to the preparation method of the present invention.

[0056] Figure 3 The images show the Fourier Transform Infrared (FT-IR) spectra of NH2-MIL-88 prepared in step (1) of Example 1, ZnCo-ZIFs prepared in step (1) of Comparative Example 2, and MIL@ZIFs prepared in step (2) of Example 1. As can be seen from the figures, the peak value at 1573 cm⁻¹ is... -1 and 1381 cm -1 The peak is related to the asymmetric stretching of the carboxyl group, at 600 cm⁻¹. -1 ~1500 cm-1 The peaks within the range are caused by the tensile and bending vibrations of the imidazole ring, further confirming that NH2-MIL-88 and ZnCo-ZIFs coexist in this composite material.

[0057] Figure 4 The image shows the XRD pattern of the hollow hierarchical FeP-ZnCoP@C composite material prepared in Example 1. As can be seen from the image, the phase structure of MOFs was transformed after carbonization and phosphating.

[0058] Figure 5 These are electron microscope (EM) images of the FeP-ZnCoP@C composite material from Example 1, where (a) is an SEM image and (b) is a TEM image. The images show that the FeP-ZnCoP@C composite material prepared according to Example 1 of the present invention retains its original hollow structure and does not collapse due to calcination and phosphating reactions. Furthermore, a covering layer forms on the surface of the hollow core, exhibiting a hollow hierarchical structure. According to the present invention, the hollow hierarchical structure is beneficial for increasing the contact area with the electrolyte to expose more active sites.

[0059] Figure 6 This is a mapping elemental distribution diagram of the FeP-ZnCoP@C composite material of Example 1. As can be seen from the diagram, C, N, O, P, Co, Fe, and Zn elements are uniformly distributed throughout the hollow carbon framework.

[0060] Experimental Example 2: Electrocatalytic Hydrogen Evolution Test Electrocatalytic hydrogen evolution tests were performed on Example 1, Comparative Example 1, Comparative Example 2, and a commercially available Pt / C (20 wt%) catalyst according to the present invention. The specific procedures are as follows: The tests were conducted using a three-electrode system. The reference electrode was Ag / AgCl, the counter electrode was platinum wire, and the working electrode was a glassy carbon electrode with the catalyst supported. The electrolyte was 1 M KOH. Specifically, the working electrode was prepared as follows: 3 mg of the powdered catalysts prepared in Example 1, Comparative Example 1, and Comparative Example 2, as well as a commercially available Pt / C (20 wt%) catalyst, were dispersed in 900 μL of ethanol, 60 μL of deionized water, and 40 μL of 5 wt% naphthol, respectively, and sonicated for 20 min to ensure uniform dispersion. 20 μL of the dispersion was pipetted onto the surface of the glassy carbon electrode and allowed to air dry. Finally, the catalyst-supported glassy carbon electrode was tested for its hydrogen evolution performance in an alkaline 1 M KOH solution.

[0061] Activity testing: Linear sweep voltammetry (LSV) was performed with a test voltage range of 0 to -0.5 V vs. RHE at a scan rate of 10 mV / s. The rotating disk electrode was rotated at 1600 rpm, and the data was collected after stabilization, using the final result. For comparison, commercially available Pt / C was subjected to LSV testing under the same conditions. The potential was converted to the reversible hydrogen potential: E(RHE) = E(Ag / AgCl) + 0.059 pH + 0.197 V.

[0062] Figure 7 (a) is the linear sweep spectroscopy (LSV) curve of the catalyst for electrocatalytic hydrogen evolution, showing that at 10 mA cm⁻¹... -2 At the specified current density, both FeP@C and ZnCoP@C exhibited large hydrogen evolution overpotentials, at 188 mV and 136 mV, respectively. After forming a hollow hierarchical composite structure, the hydrogen evolution overpotential of FeP-ZnCoP@C decreased to 75 mV; a smaller overpotential indicates better hydrogen evolution performance. The performance of the FeP-ZnCoP@C composite material was also significantly improved compared to commercially available Pt / C catalysts.

[0063] Furthermore, at higher current densities (50 mA cm⁻¹) -2 and 100 mA cm -2 Under these conditions, the HER overpotentials of the FeP-ZnCoP@C composite material were 132 mV and 195 mV, respectively, which were lower than those of commercially available Pt / C catalysts and single MOF-derived metal phosphide catalysts, indicating that the synergistic effect between the hollow hierarchical composites can improve the electrocatalytic hydrogen evolution performance.

[0064] Figure 7 (b) is the Tafel slope plot. As can be seen from the figure, the Tafel slope value of FeP-ZnCoP@C of the present invention is 39.5 mV dec. -1 Compared to other samples, it showed the best performance, indicating that the FeP-ZnCoP@C composite material is more conducive to the catalytic reaction.

[0065] Experiment Example 3: Material Stability Test To verify the stability of the hollow hierarchical metal phosphide composite material prepared according to the method of the present invention in the hydrogen evolution electrochemical reaction, the FeP-ZnCoP@C composite material prepared in Example 1 was subjected to chronoamperometry (it) testing, and the specific process is as follows: The sample was coated onto a glassy carbon electrode according to the method in Example 2, and tested in a three-electrode system. Specifically, Ag / AgCl was used as the reference electrode, platinum wire as the counter electrode, and the catalyst-supported glassy carbon electrode as the working electrode. 1 MKOH was used as the electrolyte. The working electrode was prepared as follows: 3 mg of the FeP-ZnCoP@C composite powder catalyst prepared in Example 1 was dispersed in 900 μL of ethanol, 60 μL of deionized water, and 40 μL of 5 wt% naphthol (Nafion). The mixture was sonicated for 20 min to ensure uniform dispersion. 20 μL of the dispersion was pipetted onto the surface of the glassy carbon electrode and allowed to air dry. Stability tests were then performed, and the results were... Figure 8 As shown in the image.

[0066] Depend on Figure 8 It can be seen that at 10 mA cm -2 After continuous operation at a current density for 10 h, the stability of the catalyst did not decrease significantly, indicating that the hollow hierarchical metal phosphide composite material prepared according to the method of the present invention has good stability as a catalyst.

[0067] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experimentation on the basis of the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a hollow hierarchical metal phosphide composite material derived from dual MOFs, characterized in that: Comprising the following steps: (1) Synthesis of hollow body NH2-MIL-88: Synthesizing solid NH2-MIL-88 nanoparticles, i.e. MIL nanoparticles, by using FeCl3·6H2O, NH2-H2BDC and polyvinylpyrrolidone; (2) Synthesis of hollow MIL@ZIFs: Dispersing the MIL nanoparticles obtained in step (1) in an organic solvent, then adding Co(NO3)2·6H2O, Zn(NO3)2·6H2O and 2-methylimidazole in sequence, and after the reaction is completed, separating by centrifugation, washing and drying to obtain a MIL@ZIFs solid product; (3) Pyrolysis carbonization: Under an inert atmosphere, calcining the MIL@ZIFs solid product obtained in step (2), and after cooling to room temperature, obtaining a MIL@ZIFs-oxide material; (4) Phosphidation reaction: Placing sodium hypophosphite and the MIL@ZIFs-oxide material obtained in step (3) in a glass tube, then placing the glass tube in a tube furnace, with sodium hypophosphite close to the air inlet of the tube furnace and the MIL@ZIFs-oxide material close to the air outlet of the tube furnace; under an inert atmosphere, heating to a third temperature and holding, then cooling to room temperature to obtain a phosphidized FeP-ZnCoP@C composite material.

2. The method of claim 1, wherein: Step (1) specifically comprises: adding FeCl3·6H2O into a DMF solvent, ultrasonic treatment and stirring at room temperature to obtain a solution A; adding NH2-H2BDC and polyvinylpyrrolidone into the solution A and stirring at room temperature to obtain a mixed solution; then, transferring the mixed solution into a glass flask, placing the glass flask in an oil bath and performing a reflux reaction under stirring; then after cooling to room temperature, performing centrifugal separation, washing the separated solid, and after vacuum drying, obtaining a solid MIL nanoparticle.

3. The preparation method according to claim 2, characterized in that, In step (1), the mass ratio of FeCl3·6H2O, NH2-H2BDC and PVP is (0.10-0.20) : (0.08-0.12) : (0.25-0.30); the reflux reaction temperature is 140-150°C, and the reflux reaction time is 2±0.5 h; the vacuum drying temperature is controlled to be 50-80°C, and the vacuum drying time is 10-14 h.

4. The method of claim 1, wherein, The organic solvent in step (2) is methanol, and specifically comprises: dispersing the MIL nanoparticles obtained in step (1) into methanol, stirring at room temperature to obtain a mixed solution; adding Co(NO3)2·6H2O and Zn(NO3)2·6H2O into the mixed solution, stirring at room temperature to obtain a solution B; then adding 2-methylimidazole into the solution B, after the reaction is completed under stirring at room temperature, performing centrifugal separation, washing and vacuum drying to obtain a MIL@ZIFs solid product.

5. The preparation method according to claim 4, characterized in that, In step (2), the mass ratio of the MIL, Co(NO3)2·6H2O, Zn(NO3)2·6H2O and 2-methylimidazole is (0.004-0.008) : (0.010-0.013) : (0.002-0.004) : (0.050-0.070); the reaction temperature is 25℃±5℃, and the reaction time is 40±10 min; the vacuum drying temperature is controlled at 50-80℃, and the vacuum drying time is 10-14 h.

6. The production method according to claim 1, characterized by, In step (3), hierarchical calcination is used, specifically including: first, heating to a first temperature of 100-300℃ at a heating rate of 5±0.5℃ / min, and maintaining at the first temperature for 1±0.5 h; then heating to a second temperature of 400-600℃ at a heating rate of 5±0.5℃ / min, and maintaining at the second temperature for 2±0.5 h.

7. The production method according to claim 1, characterized by, In step (4), the mass ratio of sodium hypophosphite and the MIL@ZIFs-oxide catalytic material is (1.50-3.00) : (0.06-0.07).

8. The production method according to claim 1, characterized by, In step (4), heating to a third temperature of 300-400℃ at a rate of 5±5℃ / min, and maintaining at the third temperature for 2±0.5 h.

9. A double MOFs derived hollow hierarchical structured metal phosphide composite material, which is prepared according to the preparation method of any one of claims 1 to 8.

10. Use of the double MOFs derived hollow hierarchical structured metal phosphide composite material according to claim 9 as a catalyst in electrocatalytic hydrogen evolution.

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