Oxide-doped mof-supported transition metal phosphide composites, methods of making and using the same

Abstract

The present application relates to an oxide-doped MOF supported transition metal phosphide composite material, a preparation method and application thereof, the preparation method comprising: reacting an MOF supported transition metal phosphide material in a high-oxidizing metal salt solution. The composite material prepared by the present application has hydrogen evolution reaction (HER) catalytic performance beyond that of commercial Pt / C material, the activity is more than doubled compared to before oxidation, the stability is greatly improved, and the composite material can be stably operated at a current density of 0.5 A cm ‑2 for more than 1000 hours without attenuation, and the performance does not change significantly after more than 3000 start-stop cycles in a reverse current test, which has great industrial application value for water electrolysis with fluctuating power supply. The preparation method of the present application is simple, has strong expandability, uses cheap and readily available raw materials, has a short production cycle, high reproducibility, and is suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the field of transition metal phosphide composite technology, specifically to an oxide-doped MOF-supported transition metal phosphide composite material, its preparation method, and its application. Background Technology

[0002] Developing inexpensive, efficient, and readily available transition metal electrocatalysts is crucial for advancing the industrialization of water electrolysis for hydrogen production. Metal-organic frameworks (MOFs) are considered ideal electrocatalyst supports or precursors due to their high specific surface area, tunable pore structure, and controllable chemical composition. However, the poor conductivity of MOFs and their tendency to collapse under electrochemical conditions severely limit their practical application in water electrolysis. Therefore, constructing MOF-based composite catalysts has become an important strategy to overcome the bottlenecks in stability and conductivity.

[0003] Transition metal phosphides (TMPs) possess hydrogenase-like active centers and exhibit excellent catalytic performance in the hydrogen evolution reaction (HER). However, they are prone to oxidation in alkaline media and exhibit poor stability. Transition metal oxides (TMOs) are structurally stable under alkaline conditions and can maintain high electrochemical stability through reversible changes in the valence state of metal ions, but their intrinsic catalytic activity is generally poor. Combining the high activity of TMPs with the structural stability of TMOs, and leveraging the coordination environment and framework dispersion effects of MOFs to construct a "MOF-TMP-TMO" multi-component composite material system, it is expected to synergistically improve the activity and durability of electrocatalysts. This could provide a new material pathway for efficient and stable water electrolysis hydrogen production technology, further promoting its industrialization. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention provides a method for preparing an oxide-doped MOF-supported transition metal phosphide composite material, comprising, MOF-supported transition metal phosphide materials were reacted in a highly oxidizing metal acid salt solution to obtain oxide-doped MOF-supported transition metal phosphide composite materials.

[0005] Furthermore, the highly oxidizing metal salt solution includes at least one of permanganate, ferrate, and dichromate.

[0006] Furthermore, the concentration of the highly oxidizing metal salt solution is between 1 mmol / L and the saturation concentration.

[0007] Furthermore, the reaction is continued at a temperature of 20-60°C; 1-60min.

[0008] Furthermore, the preparation method of the oxide-doped MOF-supported transition metal phosphide material includes, A reaction system was obtained by mixing a transition metal salt, a pH adjuster, and a solvent, followed by a solvothermal reaction to obtain a hydroxide precursor. MOF materials are obtained by reacting hydroxide precursors and organic ligands using a gas-phase reaction method. Based on the gas-phase reaction method, MOF materials and phosphorus sources are reacted to obtain MOF-supported transition metal phosphide materials.

[0009] Furthermore, the pH adjuster includes at least one of urea, hexamethylenetetramine, ethylenediamine, melamine, ammonia, ammonium fluoride, ammonium chloride, and ammonium sulfate; The organic ligand includes at least one of imidazole, 2-methylimidazole, and 1,4-phthalic acid; The phosphorus source mentioned includes one of sodium hypophosphite, red phosphorus, and black phosphorus.

[0010] Furthermore, the concentrations of the transition metal salt and the pH adjuster in the reaction system are 0.05-0.2 mol / L and 0.4-0.8 mol / L, respectively.

[0011] The molar amount of the organic ligand is 5-20 times the molar amount of the metal in the hydroxide; The amount of phosphorus source used is 2-30 times the mass of the MOF-supported transition metal phosphide material.

[0012] The amount of phosphorus source used is 2-30 times the mass of MOF.

[0013] Furthermore, the solvothermal reaction is carried out at a temperature of 90-140°C for 6-12 hours; The gas-phase reaction method includes heating to 250-350°C at a heating rate of 1-5°C / min and holding at that temperature for 1-2 hours under a protective atmosphere.

[0014] The present invention also provides a MOF-loaded transition metal phosphide composite material, which is obtained by the above preparation method.

[0015] This invention also provides the application of the above-mentioned MOF-loaded transition metal phosphide composite material in catalysis.

[0016] Compared with the prior art, the beneficial effects of the present invention include: The oxide-doped MOF-supported transition metal phosphide composite material prepared in this invention exhibits HER catalytic performance surpassing that of commercial Pt / C materials, and can achieve catalytic activity at 0.5 A·cm⁻¹. -2It can operate stably for more than 1,000 hours under high current density without degradation, and its performance shows no significant change after withstanding more than 3,000 start-stop cycles in reverse current testing, making it valuable for industrial applications of fluctuating power supply in water electrolysis.

[0017] The preparation method of this invention is simple, highly scalable, uses inexpensive and readily available raw materials, has a short production cycle, and is suitable for large-scale production.

[0018] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0020] Figure 1 The XRD pattern of the MnO2-CoP / MOF material prepared in Example 1 is shown; Figure 2 The scanning electron microscope image of the MnO2-CoP / MOF material prepared in Example 1 is shown; Figure 3 The elemental distribution diagram of the MnO2-CoP / MOF material prepared in Example 1 is shown; Figure 4 A high-magnification transmission electron microscope image of the MnO2-CoP / MOF material prepared in Example 1 is shown; Figure 5 The HER polarization curves of the materials obtained in Example 1, Comparative Example 1 and Comparative Example 2, and the commercial palladium on carbon catalyst are shown. Figure 6 The chronocurrent curves of the materials obtained in Example 1 and Comparative Example 1 are shown; Figure 7 The reverse current test curve of the MnO2-CoP / MOF prepared in Example 1 is shown. The test method is positive current (current density 0.5 A·cm). -2 ) 10 min and reverse current (current density 0.1 A·cm) -2 The 1-minute tests were performed alternately.

[0021] Figure 8 The HER polarization curves of the materials obtained in Examples 1-3 are shown; Figure 9The HER polarization curves of the materials obtained in Examples 1 and 4-7 are shown. Figure 10 The HER polarization curves of the materials obtained in Examples 1 and 8-10 are shown. Figure 11 The HER polarization curves of the materials obtained in Example 1, Comparative Example 1, and Comparative Example 2 in simulated seawater are shown. Figure 12 The material obtained in Example 1 was shown to react in simulated seawater at a rate of 0.2 A·cm⁻¹. -2 and 0.5A·cm -2 The timing current curve of the current density; Figure 13 The HER polarization curves of the materials obtained in Examples 1, 15, and 16, as well as the palladium-on-carbon catalyst, are shown. Figure 14 The HER polarization curves of the materials obtained in Examples 1, 21 and 22, as well as the palladium-on-carbon catalyst, are shown. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the invention, are intended to cover non-exclusive inclusion.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] The concept of this invention lies in treating MOF-supported transition metal phosphide materials with a highly oxidizing metal acid salt solution to oxidize part of the MOF into transition metal oxides, thereby constructing a composite material. Based on the high activity of transition metal phosphides, the stability of transition metal oxides, and the coordination and dispersing effects of MOFs, the composite material exhibits excellent electrocatalytic activity.

[0026] Accordingly, the present invention provides a method for preparing an oxide-doped MOF-supported transition metal phosphide composite material, comprising, MOF-supported transition metal phosphide materials were reacted in a highly oxidizing metal acid salt solution to obtain oxide-doped MOF-supported transition metal phosphide composite materials.

[0027] In some preferred embodiments, the concentration of the highly oxidizing metal salt solution is between 1 mmol / L and the saturation concentration.

[0028] In some preferred embodiments, the highly oxidizing metal salt solution includes at least one of permanganate, ferrate, and dichromate.

[0029] In some preferred embodiments, the reaction is carried out at a temperature of 20-60°C for 1-60 minutes.

[0030] In some preferred embodiments, the preparation method of the oxide-doped MOF-supported transition metal phosphide composite material includes, A reaction system was obtained by mixing a transition metal salt, a pH adjuster, and a solvent, followed by a solvothermal reaction to obtain a hydroxide precursor. MOF materials are obtained by reacting hydroxide precursors and organic ligands using a gas-phase reaction method. Based on the gas-phase reaction method, MOF materials and phosphorus sources are reacted to obtain MOF-supported transition metal phosphide materials.

[0031] In some preferred embodiments, the concentrations of the transition metal salt and the pH adjuster in the reaction system are 0.05-0.2 mol / L and 0.4-0.8 mol / L, respectively; The solvothermal reaction is carried out at a temperature of 90-140℃ for 6-12 hours. The molar amount of the organic ligand is 5-20 times the molar amount of the metal in the MOF-supported transition metal phosphide material; The amount of phosphorus source used is 2-30 times the mass of the MOF-supported transition metal phosphide material.

[0032] In some preferred embodiments, to facilitate electrochemical testing, a support can be added in the initial stage of preparing the hydroxide precursor. The support can be a porous metal material (foamed nickel, foamed copper, foamed aluminum, foamed titanium, etc.), carbon felt, carbon fiber, metal sheet, etc. The amount (area) of the support used is not strictly limited and can be selected according to conventional practices in the art, as long as it can ensure good growth of the metal hydroxide. It should be emphasized that even without a support, the resulting composite material still has good catalytic performance.

[0033] It should be noted that the types of transition metal salts and solvents are not strictly limited. Solvents can be at least one of water, ethanol, acetone, ethylene glycol, isopropanol, etc., but for solvents dissolving highly oxidizing metal salts, it must be ensured that the solvent does not react with the highly oxidizing metal salt. Transition metal salts are selected from at least one of nitrates, hydrochlorides, sulfates, and acetates, and the preferred transition metal element is at least one of iron, cobalt, nickel, and copper.

[0034] In some preferred embodiments, the pH adjuster includes at least one of urea, hexamethylenetetramine, ethylenediamine, melamine, ammonia, ammonium fluoride, ammonium chloride, and ammonium sulfate; The organic ligand includes at least one of imidazole, 2-methylimidazole, and 1,4-phthalic acid; The phosphorus source includes one of sodium hypophosphite, red phosphorus, and black phosphorus.

[0035] In some preferred embodiments, the gas-phase reaction method includes heating to 250-350°C at a heating rate of 1-5°C / min and holding at that temperature for 1-2 hours under a protective gas atmosphere. The protective gas includes at least one of rare gases, nitrogen, etc.

[0036] The present invention will be further described in detail below through specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0037] Example 1 A method for preparing MnO2-doped CoP / MOF composite material includes the following steps: S1. Dissolve 1 mmol of Co(NO3)2·6H2O, 4 mmol of NH4F, and 5 mmol of CO(NH2)2 in 15 mL of ultrapure water to obtain a solution. Then transfer the solution to a 22 mL reaction vessel, immerse a 1×2 cm piece of carbon cloth in the solution, and heat it to 120 °C at a heating rate of 5 °C / min and maintain it for 8 h. After natural cooling, collect the insoluble matter and wash it three times with ultrapure water to obtain the hydroxide precursor.

[0038] S2. Using a quartz tube with one open end, a diameter of 2.5 cm, and a length of 10 cm as a reaction vessel, 20 mmol of imidazole powder (20 times the molar amount of metallic cobalt) was placed at the sealed end, and the hydroxide precursor was placed horizontally near the outlet of the quartz tube. Then, the quartz tube was placed in a tube furnace and heated to 280 °C at a rate of 5 °C / min under a N2 atmosphere, and held at this temperature for 1.5 h to obtain MOF material.

[0039] S3. Place 10 mmol (1.06 g) of NaH2PO2·H2O at the sealed end and place 0.25 g of MOF material in the center of the quartz tube. Then, place the quartz tube in a tube furnace and heat it to 270 °C at a rate of 2 °C / min under a nitrogen atmosphere. Hold it at this temperature for 2 h and allow it to cool naturally to obtain MOF-supported transition metal phosphide material, denoted as CoP / MOF.

[0040] S4. Immerse the CoP / MOF in a 5 mmol / L KMnO4 solution for 2 min, then remove and dry at room temperature to obtain the MnO2-doped CoP / MOF composite material, denoted as MnO2-CoP / MOF.

[0041] Example 2-3 The difference from Example 1 is that the temperature is adjusted to 260°C and 280°C in step S3.

[0042] Examples 4-7 The difference from Example 1 is that the concentrations of the KMnO4 solutions were 1 mmol / L, 2 mmol / L, 10 mmol / L, and 20 mmol / L, respectively.

[0043] Examples 8-10 The difference from Example 1 is that the reaction times in step S4 are 1 min, 4 min, and 8 min, respectively.

[0044] Examples 11-13 Compared with Example 1, the difference is that in step S1, CoCl2·6H2O, CoSO4·6H2O and (CH3COO)2Co·4H2O are used to replace Co(NO3)2·6H2O respectively.

[0045] Examples 14-16 Compared with Example 1, the difference is that in step S1, Fe(NO3)3·9H2O, Ni(NO3)2·6H2O and Cu(NO3)2·6H2O are used to replace Co(NO3)2·6H2O, respectively, and the resulting materials are MnO2-FeP / MOF, MnO2-NiP / MOF and MnO2-CuP / MOF.

[0046] Examples 17-18 Compared with Example 1, the difference is that in step S1, nickel foam and titanium sheets are used instead of carbon cloth as carriers.

[0047] Examples 19-21 Compared with Example 1, the difference is that in step S2, 2-methylimidazole, terephthalic acid, and pyromellitic acid are used to replace imidazole, respectively.

[0048] Examples 21-22 Compared with Example 1, the difference is that in step S3, potassium dichromate solution and potassium ferrate solution are used instead of KMnO4 solution, and the resulting materials are CrO4-CoP / MOF and Fe3O4-CoP / MOF, respectively.

[0049] Comparative Example 1 A method for preparing MOF-supported metal phosphide materials includes the following steps: S1. Dissolve 1 mmol of Co(NO3)2·6H2O, 4 mmol of NH4F, and 5 mmol of CO(NH2)2 in 15 mL of ultrapure water to obtain a solution. Then transfer the solution to a 22 mL reaction vessel, immerse a 1×2 cm piece of carbon cloth in the solution, and heat it to 120 °C at a heating rate of 5 °C / min and maintain it for 8 h. After natural cooling, collect the insoluble matter and wash it three times with ultrapure water to obtain the hydroxide precursor.

[0050] S2. Using a quartz tube with one open end, a diameter of 2.5 cm, and a length of 10 cm as a reaction vessel, 20 mmol of imidazole powder was placed at the sealed end, and a hydroxide precursor was placed horizontally near the outlet of the quartz tube. The molar amount of the organic ligand was 5 times the molar amount of the metal in the hydroxide precursor. The quartz tube was then placed in a tube furnace and heated to 280 °C at a rate of 5 °C / min under a N2 atmosphere, and held at this temperature for 1.5 h to obtain a MOF-loaded support.

[0051] S3. Place 10 mmol (1.06 g) of NaH2PO2·H2O at the sealed end, and place the MOF-loaded support in the center of the quartz tube. Then, place the quartz tube in a tube furnace and heat it to 270°C at a rate of 2°C / min under a nitrogen atmosphere. Hold it at this temperature for 2 hours and allow it to cool naturally to obtain the MOF-loaded metal phosphide material, denoted as CoP / MOF.

[0052] Comparative Example 2 A method for preparing a metal oxide-doped MOF material includes the following steps: S1. Dissolve 1 mmol of Co(NO3)2·6H2O, 4 mmol of NH4F, and 5 mmol of CO(NH2)2 in 15 mL of ultrapure water to obtain a solution. Then transfer the solution to a 22 mL reaction vessel, immerse a 1×2 cm piece of carbon cloth in the solution, and heat it to 120 °C at a heating rate of 5 °C / min and maintain it for 8 h. After natural cooling, collect the insoluble matter and wash it three times with ultrapure water to obtain the hydroxide precursor.

[0053] S2. Using a quartz tube with one open end, a diameter of 2.5 cm, and a length of 10 cm as a reaction vessel, 20 mmol of imidazole powder was placed at the sealed end, and a hydroxide carrier was placed horizontally near the outlet of the quartz tube. The molar amount of the organic ligand was 5 times the molar amount of the metal in the carrier carrying the hydroxide. Then, the quartz tube was placed in a tube furnace and heated to 280 °C at a rate of 5 °C / min under a N2 atmosphere, and held at this temperature for 1.5 h to obtain the MOF material.

[0054] S3. Immerse the MOF material in a 5 mmol / L KMnO4 solution for 2 min, then remove and dry at room temperature to obtain a metal oxide-doped MOF material, denoted as MnO2 / MOF.

[0055] Comparative Example 3 A method for preparing MOF composite materials includes the following steps: S1. Dissolve 1 mmol of Co(NO3)2·6H2O, 4 mmol of NH4F, and 5 mmol of CO(NH2)2 in 15 mL of ultrapure water to obtain a solution. Then transfer the solution to a 22 mL reaction vessel, immerse a 1×2 cm piece of carbon cloth in the solution, and heat it to 120 °C at a heating rate of 5 °C / min and maintain it for 8 h. After natural cooling, collect the insoluble matter and wash it three times with ultrapure water to obtain the hydroxide precursor.

[0056] S2. Using a quartz tube with one open end, a diameter of 2.5 cm, and a length of 10 cm as a reaction vessel, 20 mmol of imidazole powder was placed at the sealed end, and a hydroxide precursor was placed horizontally near the outlet of the quartz tube. The molar amount of the organic ligand was 5 times the molar amount of the metal in the support carrying the hydroxide. Then, the quartz tube was placed in a tube furnace and heated to 280 °C at a rate of 5 °C / min under a N2 atmosphere, and held at this temperature for 1.5 h to obtain the MOF material.

[0057] S3. Immerse the MOF material in a KMnO4 solution with a concentration of 5 mmol / L for 2 min, then remove it and dry it at room temperature to obtain the metal oxide doped MOF material.

[0058] S4. Place 10 mmol (1.06 g) of NaH2PO2·H2O at the sealed end, and place the metal oxide-doped MOF material in the center of the quartz tube. Then, place the quartz tube in a tube furnace and heat it to 270°C at a rate of 2°C / min under a nitrogen atmosphere. Hold it at this temperature for 2 hours and allow it to cool naturally to obtain the MOF composite material.

[0059] Test case The crystal structure of MnO2-CoP / MOF in Example 1 was observed using XRD. Figure 1 It can be seen that it mainly exhibits the crystal structure of CoP.

[0060] The microstructure of the MnO2-CoP / MOF in Example 1 was observed using scanning electron microscopy. Figure 2 It can be seen that the overall morphology is a spherical secondary structure assembled from rods. From Figure 3 The data shows that Co, Mn, P, O, and N elements are uniformly distributed in the sample, indicating the successful preparation of the heteromaterial. Figure 4 It can be seen that MnO2-CoP / MOF has lattice spacings of 0.175 and 0.214 nm, which correspond to the (020) and (202) crystal planes of CoP, respectively.

[0061] The HER polarization curves of the MnO2-CoP / MOF prepared in Example 1, the CoP / MOF of Comparative Example 1, the MnO2 / MOF of Comparative Example 2, and commercially available Pt / C were tested in 1 mol / L potassium hydroxide solution. Figure 5 As can be seen, MnO2-CoP / MOF has the lowest overpotential, and only requires an overpotential of 18mV to reach 10mA·cm. -2 The current density demonstrated that it has the highest electrocatalytic hydrogen evolution activity.

[0062] Using 1 mol / L potassium hydroxide solution as the electrolyte, the electrolyte levels of Example 1 and Comparative Example 1 were tested at 200 mA·cm⁻¹. -2 and 500mA·cm -2 The chronopotential curve at current density. From Figure 6 As can be seen, the MnO2-CoP / MOF of Example 1 can operate stably for 1000 hours at this current density with almost no change in performance, while the CoP / MOF of Comparative Example 1 quickly loses its activity. Figure 7 The reverse current test results of MnO2-CoP / MOF were shown, and it can be observed that the catalyst performance of MnO2-CoP / MOF did not decline after 3000 simulated start-stop cycles.

[0063] Using 1 mol / L potassium hydroxide solution as the electrolyte, the HER polarization curves of the materials obtained in Examples 1-3 were tested. Figure 8 As can be seen, compared to Example 1, the activity and stability of Example 2 (which had a lower temperature) and Example 3 (which had a higher temperature) both decreased to some extent. This indicates that the phosphating temperature has a certain influence on the electrocatalytic performance of the final material.

[0064] Using 1 mol / L potassium hydroxide solution as the electrolyte, the HER polarization curves of the materials obtained in Examples 1 and 4-7 were tested. Figure 9 It can be seen that the performance of the prepared MOF-based transition metal phosphide heteromaterials exhibits a volcano-like relationship with the increase of KMnO4 concentration, indicating that there is an optimal range of MnO2 concentration. Excessive MnO2 can easily reduce the exposed area of ​​CoP active sites.

[0065] Using 1 mol / L potassium hydroxide solution as the electrolyte, the HER polarization curves of the materials obtained in Examples 1 and 8-10 were tested. Figure 10 It can be seen that the properties of the prepared MOF-based transition metal phosphide heteromaterials exhibit a volcano-like relationship with reaction time.

[0066] The MnO2 / CoP-MOF prepared in Example 1, the CoP-MOF of Comparative Example 1, and the MnO2 of Comparative Example 2 were compared. X HER polarization curves were tested using MOF and commercially available Pt / C in simulated seawater electrolyte (1 mol / L KOH + 3.5% wt NaCl) at the same concentration and pH. Figure 11 It can be seen that it reaches 10 mA·cm -2 The current density required in Example 1 is only 38mV overpotential, indicating that the MnO2 / CoP-MOF of Example 1 has a significantly improved resistance to chloride ion interference during the catalytic hydrogen evolution reaction compared to Pt / C materials.

[0067] Using simulated seawater as the electrolyte, the MnO2 / CoP-MOF prepared in Example 1 was tested at 500 mA·cm⁻¹. -2 The chronopotential curves at high current densities show that MnO2 / CoP-MOF exhibits excellent stability, capable of operating stably for over 1000 hours at high current densities without degradation. Figure 12 ).

[0068] The HER polarization curves of the materials obtained in Examples 1, 15, and 16, as well as the palladium-on-carbon catalyst, were also tested. Figure 13 As can be seen, compared with MnO2-NiP / MOF and MnO2-CuP / MOF, the MnO2 / CoP-MOF of Example 1 has a lower overpotential.

[0069] The HER polarization curves of the materials obtained in Examples 1, 21, and 22, as well as the palladium-on-carbon catalyst, were also tested. Figure 14 As can be seen, compared with CrO4-CoP / MOF and Fe3O4-CoP / MOF, the MnO2 / CoP-MOF of Example 1 has a lower overpotential.

[0070] It should be noted that, compared to Example 1, Comparative Example 3 used an oxidation-then-phosphating method, resulting in a significant decrease in the catalytic activity and very poor stability of the product. This is because the metal oxide formed by oxidation is converted into phosphide in the subsequent phosphating step, and the phosphide is easily converted into soluble phosphate when electrochemically tested in alkaline solution, causing the loss of active sites.

[0071] In summary, this invention employs a highly oxidizing metal acid salt solution to treat MOF-supported transition metal phosphide materials, oxidizing a portion of the MOF to transition metal oxides, thereby constructing a ternary composite heteromaterial. Based on the high activity of transition metal phosphides, the stability of transition metal oxides, and the coordination and dispersion effects of MOFs, the composite heteromaterial exhibits excellent electrocatalytic activity. The oxide-doped MOF-supported transition metal phosphide composite material prepared in this invention exhibits HER catalytic performance surpassing that of commercial Pt / C materials, and can achieve catalytic activity at 0.5 A·cm⁻¹. -2 It can operate stably for more than 1,000 hours under high current density without degradation, and its performance shows no significant degradation after withstanding more than 3,000 start-stop cycles in reverse current testing, making it valuable for industrial applications of fluctuating power supply in water electrolysis.

[0072] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an oxide-doped MOF-supported transition metal phosphide composite material, characterized in that, include, MOF-supported transition metal phosphide materials were reacted in a highly oxidizing metal acid salt solution to obtain oxide-doped MOF-supported transition metal phosphide composite materials.

2. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 1, characterized in that, The concentration of the highly oxidizing metal acid salt solution is between 1 mmol / L and the saturation concentration; The highly oxidizing metal salt solution includes at least one of permanganate, ferrate, and dichromate.

3. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 1, characterized in that, The reaction was carried out at a temperature of 20-60°C for 1-60 minutes.

4. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 1, characterized in that, The preparation method of the MOF-supported transition metal phosphide material includes: A reaction system was obtained by mixing a transition metal salt, a pH adjuster, and a solvent, followed by a solvothermal reaction to obtain a hydroxide precursor. MOF materials are obtained by reacting hydroxide precursors and organic ligands using a gas-phase reaction method. Based on the gas-phase reaction method, MOF materials and phosphorus sources are reacted to obtain MOF-supported transition metal phosphide materials.

5. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 4, characterized in that, The pH adjuster includes at least one of urea, hexamethylenetetramine, ethylenediamine, melamine, ammonia, ammonium fluoride, ammonium chloride, and ammonium sulfate; The organic ligand includes at least one of imidazole, 2-methylimidazole, and 1,4-phthalic acid; The phosphorus source includes one of sodium hypophosphite, red phosphorus, and black phosphorus.

6. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 4, characterized in that, The concentrations of the transition metal salt and the pH adjuster in the reaction system are 0.05-0.2 mol / L and 0.4-0.8 mol / L, respectively.

7. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 4, characterized in that, The molar amount of the organic ligand is 5-20 times the molar amount of the metal in the hydroxide; The amount of phosphorus source used is 2-30 times the mass of the MOF-supported transition metal phosphide material.

8. The method for preparing the oxide-doped MOF-supported transition metal phosphide composite material according to claim 4, characterized in that, The solvothermal reaction is carried out at a temperature of 90-140℃ for 6-12 hours. The gas-phase reaction method includes heating to 250-350°C in a protective atmosphere at a heating rate of 1-5°C / min and holding at that temperature for 1-2 hours.

9. A composite material of oxide-doped MOF-supported transition metal phosphide, characterized in that, It is obtained by the preparation method according to any one of claims 1-8.

10. The application of the oxide-doped MOF-supported transition metal phosphide composite material as described in claim 6 in catalysis.

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