A transition metal-doped nickel phosphide integral composite electrocatalytic material, preparation method and application

Abstract

The present invention provides a transition metal-doped nickel phosphide integral composite electrocatalytic material, a preparation method and an application thereof, belonging to the technical field of electrocatalytic material preparation, wherein the preparation method comprises the following steps: (1) pre-treating a nickel-based material as a carrier, and then preparing a mixed raw material liquid of copper salt and cobalt salt at a certain concentration and molar ratio. (2) placing the nickel substrate in a hydrothermal kettle and adding the raw material liquid, and then placing it in an oven for constant temperature hydrothermal heating to obtain a transition metal-doped integral composite material pre-product; (3) treating the hydrothermal pre-product in a tubular furnace using a phosphating process to obtain a transition metal-doped nickel phosphide integral composite catalytic material. The present invention has the following advantages: First, the process of the present invention is simple, the operation difficulty is low, the raw material source is wide, and the production cost is low. Second, the transition metal-doped nickel phosphide integral composite catalytic material prepared by the method has the advantages of high catalytic activity, stable active substances, and high selectivity.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a transition metal-doped nickel phosphide integral composite electrocatalytic material, belonging to the technical field of electrocatalytic material preparation. Background Art

[0002] Electrocatalytic water splitting for hydrogen production has become a promising energy conversion technology due to its mild operating conditions and clean, pollution-free operation. The water splitting process primarily involves the hydrogen evolution reaction (HER) at the cathode and the oxygen evolution reaction (OER) at the anode. While the HER is a simple two-electron transfer process, the OER involves a complex four-electron transfer process, making the OER the rate-limiting step in water electrolysis. Theoretical studies indicate that the overall thermodynamic potential for water splitting is 1.23 V in both acidic and alkaline electrolytes. To achieve efficient water splitting, voltages significantly higher than 1.23 V are required to achieve a significant current density, which increases the cost of hydrogen production. Compared to hydrogen produced by the HER, the oxygen produced by the anode OER has a lower added value, and the coexistence of hydrogen and oxygen can pose safety risks. To address the challenges facing electrocatalytic water splitting for hydrogen production, hybrid water electrolysis, combining cathode hydrogen evolution with anode organic oxidation, has emerged as a promising approach. At the anode, the organic substrates in the electrolyte usually have good water solubility. Thermodynamically, the energy barrier required for the electrochemical oxidation of organic matter is lower than that of OER, and it is expected to replace OER and ultimately facilitate the simultaneous production of green hydrogen and high-value-added fine chemicals.

[0003] Currently, the global annual production of polyester plastics, such as polyethylene terephthalate (PET), is approximately 65-70 million tons. Its production primarily relies on petroleum-derived terephthalic acid, which limits resources and the environment. Poly(ethylene 2,5-furandicarboxylate) (PEF) plastic has become one of the most promising alternatives to PET plastics due to its lower overall carbon emissions and improved practicality. PEF is produced by polymerizing biomass-based 2,5-furandicarboxylic acid (FDCA) with ethylene glycol. Studies have shown that FDCA has become a high-value-added bio- and chemical intermediate, and the US Department of Energy has designated FDCA as one of 12 priority compounds for building a future green chemical industry. Currently, FDCA is primarily produced through the oxidation of 5-hydroxymethylfurfural (HMF), obtained by dehydration of hexose sugars, using traditional thermal catalytic technology. Electrocatalytic conversion offers advantages over traditional thermal catalysis, including milder reaction conditions, more controllable processes, and simpler operation. Therefore, combining electrochemical HMF oxidation with water splitting can achieve the coupled production of high-value-added FDCA and high-purity hydrogen, giving full play to the advantages of hybrid water electrolysis. In addition, HMF has good water solubility, and its thermodynamic potential for electrooxidation is 0.11V, which is much lower than the thermodynamic potential of water splitting of 1.23V, and can replace the OER reaction with a higher energy barrier at the anode. The development of high-performance and low-cost electrocatalysts is also an important part of achieving efficient water splitting. At present, the existing HMF oxidation electrocatalysts are mainly precious metal catalysts such as palladium, platinum or gold, which are difficult to achieve large-scale utilization due to their high cost and limited resources. Transition metals such as manganese, iron, nickel, cobalt, copper, etc. have the advantages of wide sources and low cost. Therefore, the development of transition metal electrocatalysts that are easy to mass produce, high-performance and highly stable has become a need for the development of electrocatalysis.

[0004] Existing transition metal catalytic materials are affected by their synthesis methods, resulting in complex synthesis processes and long preparation times. The synthesized catalysts also have significant deficiencies in selectivity and service life. We used commercial nickel foam as a substrate and first synthesized a transition metal-doped integral composite material pre-product using a hydrothermal method. This was then treated with a phosphating process to form a transition metal-doped nickel phosphide integral composite catalytic material with high activity and stability. Compared with catalysts reported domestically and internationally, this catalytic material has significant advantages in HMF electrooxidation performance. Commercial nickel foam ensures a stable source of raw materials for the synthesized catalyst, and the hydrothermal reaction and phosphating process are important technologies with the potential for scalable production. Further exploration of process conditions suitable for the scale-up of this catalytic material should be continued to lay a solid foundation for practical application. Summary of the Invention

[0005] In order to overcome the performance deficiencies of existing materials, the purpose of the present invention is to provide a method for preparing a transition metal-doped nickel phosphide integral composite catalytic material and its application. This method uses commercial, low-cost nickel foam as a carrier to synthesize a transition metal-doped integral composite material pre-product, and further cooperates with a simple phosphating process to synthesize a transition gold-doped nickel phosphide integral composite catalytic material. This process has the advantages of low cost and low operating difficulty, and can prepare electrocatalytic anode materials with excellent performance. The composite catalytic material prepared using this process has the advantages of high catalytic activity, long life, high selectivity, etc., and has great application potential in the field of catalysis. On this basis, the catalytic activity of HMF-assisted water splitting to produce hydrogen was explored.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is:

[0007] A method for preparing a transition metal-doped nickel phosphide integral composite catalytic material comprises the following steps:

[0008] The first step is to prepare the transition metal-doped overall composite material pre-product

[0009] 1.1) Dissolve copper salt and cobalt salt in water to obtain a salt solution. Add ammonium fluoride and urea to the salt solution and stir to obtain an alkaline raw material solution.

[0010] 1.2) Place the nickel foam in a polytetrafluoroethylene-lined hydrothermal reactor, add the aforementioned raw material solution, and ultrasonicate the reactor in water for 3 minutes. After ultrasonication, conduct a constant-temperature hydrothermal reaction at 120°C-150°C for 4-6 hours. After the hydrothermal reaction, cool naturally to room temperature in an oven, open the hydrothermal reactor, and rinse with water and ethanol to obtain a transition metal-doped monolithic composite preform.

[0011] The second step is to prepare transition metal-doped nickel phosphide overall composite catalytic material

[0012] 2.1) The transition metal-doped monolithic composite material pre-product obtained in the first step is rinsed with water and ethanol, and placed in an oven for drying.

[0013] 2.2) Cut a 1cm×2cm piece of the dried pre-product into a porcelain bowl and add 0-0.5g of a phosphate salt. Place the phosphate salt next to the pre-product and close to it. Then, place the porcelain bowl with the pre-product and phosphate salt in a tube furnace, introduce argon as a protective gas, and control the temperature of the tube furnace at 250-350°C. After 0-1h of phosphating, rinse repeatedly with deionized water and place in an oven for drying to obtain a transition metal-doped nickel phosphide monolithic composite catalytic material. To ensure sufficient phosphating, the argon gas must flow through the phosphate salt first and then through the pre-product.

[0014] Furthermore, the nickel foam in step 1.2) is commercial nickel foam, and the drying temperature is 60° C. and the drying time is 30 minutes. The nickel foam is washed and dried before being added to the hydrothermal kettle.

[0015] Furthermore, in step 1.1), the cobalt salt is one of cobalt nitrate hexahydrate and cobalt chloride hexahydrate, preferably cobalt nitrate hexahydrate; the copper salt is one of copper nitrate trihydrate and copper chloride, preferably copper nitrate trihydrate. The concentrations of cobalt nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride, and urea are preferably 0-1 mmol / L, 0-0.5 mmol / L, 3 mmol / L, and 6 mmol / L, respectively.

[0016] Furthermore, in step 1.1), 0-0.291 g of cobalt salt and 0-0.121 g of copper salt are added to every 40 ml of water.

[0017] Furthermore, the ammonium fluoride in step 1.1) can be replaced by ammonium bifluoride, and the urea can be replaced by potassium hydroxide.

[0018] Furthermore, in the step 2.1), the drying temperature is 50° C. and the time is 15 min. In the step 2.1), the drying temperature is 50° C. and the time is 30 min.

[0019] Furthermore, in step 2.2), the flow rate of argon is controlled at 20-25 ml / min.

[0020] Furthermore, in the step 2.2), the phosphate salt is one of sodium phosphate, sodium hypophosphite monohydrate, and potassium phosphate.

[0021] A transition metal-doped nickel phosphide integral composite catalytic material is prepared by the above method.

[0022] The application of the transition metal-doped nickel phosphide integral composite catalytic material prepared by the above method in the hybrid water electrolysis hydrogen production reaction is as follows: the composite catalytic material obtained above is used as the anode to assemble into a three-electrode test system, the cathode uses a commercial Pt sheet electrode, and the reference electrode is saturated Ag / AgCl.

[0023] Analysis of the innovative features of the present invention: The nickel foam substrate used in the present invention has a porous structure, which can not only enhance the mass transfer between the electrolyte and the catalyst surface but also enable the overall composite catalytic material to maintain good conductivity and mechanical strength. At the same time, the added additives such as urea or potassium hydroxide provide an alkaline environment during the hydrothermal process, which allows the nickel substrate to partially dissolve in the reaction solution during the hydrothermal process. The dissolved nickel compound, copper salt, and cobalt salt form a composite catalytic material that covers the surface of the nickel substrate, achieving the synthesis of an overall composite electrocatalytic anode material with a nickel-rich surface without the addition of nickel salts. Additives such as ammonium fluoride (ammonium bifluoride) can modify the crystalline structure of the composite catalytic material, allowing the cobalt salt, copper salt, and nickel compound dissolved in the reaction solution to effectively recombine to form an amorphous compound. This amorphous structure, relying on the large surface area of ​​the porous nickel foam, can provide more active sites, thereby significantly reducing the energy barrier of the electrochemical reaction. During phosphating, the phosphorus-containing vapor generated by the decomposition of the phosphate salt under high temperature conditions is utilized to form phosphides on the surface of the pre-product. These phosphides form defective active sites, further reducing the activation energy of the reaction.

[0024] The beneficial effects of the present invention are:

[0025] (1) The method of the present invention has a simple process, low operational difficulty, a wide source of raw materials, and low production cost, and can prepare a composite catalytic material with excellent performance. The XRD spectrum shows the successful preparation of amorphous materials. On this basis, the catalytic activity of the catalytic material in the electrooxidation reaction in 1 mol / L KOH and 0.05 mol / L HMF electrolyte was investigated. The results showed that the starting potential of the entire system was close to the theoretical potential of water electrolysis of 1.23 V; the current density could reach 155 mA cm at an operating voltage of 1.5 V. -2 ; In the 9 cycle stability tests, the HMF conversion rate was 100%, showing good stability.

[0026] (2) In addition, compared with the catalytic materials reported in other works, the transition metal-doped nickel phosphide integral composite catalytic material prepared by this method has the advantages of high current density, stable active substances, and high selectivity, and has great application potential in the field of catalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a field emission scanning electron microscope photograph of the copper and cobalt doped nickel phosphide integral composite catalytic material prepared in Example 1.

[0028] Figure 2 This is the XRD spectrum of the copper- and cobalt-doped nickel phosphide integral composite catalytic material prepared in Example 1.

[0029] Figure 3These are linear voltammetric scan graphs of the composite catalytic materials prepared in Examples 1 (copper and cobalt doped nickel phosphide integral composite catalytic material), 2 (copper doped nickel phosphide integral composite catalytic material), 3 (copper doped integral composite catalytic material), 4 (cobalt doped nickel phosphide integral composite catalytic material) and 5 (cobalt doped integral composite catalytic material).

[0030] Figure 4 This is a graph showing the HMF oxidation cycle stability test of Example 6 (copper and cobalt-doped nickel phosphide integral composite catalytic material).

[0031] Figure 5 Graphs of the Faraday efficiencies of Examples 1-8 are shown. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the embodiments.

[0033] Example 1

[0034] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut the nickel foam into 2.5 cm x 3.5 cm pieces and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Weigh 0.121 g of copper nitrate, 0.291 g of cobalt nitrate, 0.111 g of ammonium fluoride, and 0.36 g of urea, mix them with 40 ml of deionized water, and stir to obtain a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam. The hydrothermal reactor is then placed in a thermostatic oven and heated at 120°C for 6 hours. After the hydrothermal reaction, the reactor is cooled to room temperature in the oven and opened to obtain a copper- and cobalt-doped monolithic composite preform. The copper- and cobalt-doped monolithic composite preform is rinsed with ethanol and dried in an oven at 50°C for 15 minutes. Cut a 1 cm x 2 cm piece of the hydrothermal preform into a 1 cm x 2 cm piece, place it in a porcelain bowl, and add 0.5 g of sodium hypophosphite monohydrate. Place the porcelain in a tube furnace and bake at 300℃ for 1 hour, using argon as the protective gas and controlling the argon flow rate at 20ml / min. After baking, the copper and cobalt doped nickel phosphide integral composite catalytic material can be obtained. Figure 1 It can be seen that the surface of nickel foam after phosphating forms a typical rod-shaped protrusion structure. Figure 2 It can be seen that the obtained copper- and cobalt-doped nickel phosphide overall composite catalytic material only shows the characteristic peaks of the nickel substrate in the XRD spectrum, and is therefore an amorphous composite material.

[0035] The composite catalytic material obtained above was used as the anode, the commercial Pt sheet electrode was used as the cathode, and the reference electrode was saturated Ag / AgCl. 15 ml of 1 M KOH and 95 mg of HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material. Figure 3It can be seen that the solid line represents the linear sweep voltammetry curve (LSV) of the synthesized copper and cobalt doped nickel phosphide overall composite catalytic material, and its starting potential for HMF oxidation is very close to the thermodynamic potential of water electrolysis.

[0036] Example 2

[0037] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut the nickel foam into 2.5 cm x 3.5 cm pieces and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Weigh 0.121 g of copper nitrate, cobalt nitrate-free, 0.111 g of ammonium fluoride, and 0.36 g of urea, mix with 40 ml of deionized water, and stir to obtain a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam. Then, place the hydrothermal reactor in a constant temperature oven at 130°C for 6 hours. After the hydrothermal reaction, cool it naturally in the oven to room temperature and open the hydrothermal reactor to obtain a copper-doped monolithic composite preform. Rinse the copper-doped monolithic composite preform obtained in step 2 with ethanol and dry it in an oven at 50°C for 15 minutes. Cut a 1 cm x 2 cm piece of the hydrothermal preform, place it in a porcelain bowl, and add 0.5 g of sodium hypophosphite monohydrate. The porcelain is placed in a tube furnace and calcined at 300°C for 1 hour, using argon as a protective gas at a flow rate of 20 ml / min. After calcination, a copper-doped nickel phosphide monolithic composite catalytic material is obtained.

[0038] The composite catalytic material obtained above was used as the anode, the commercial Pt sheet electrode was used as the cathode, and the reference electrode was saturated Ag / AgCl. 15 ml of 1 M KOH and 95 mg of HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material. Figure 3 As can be seen from the short dashed line, the copper-doped nickel phosphide overall composite catalytic material corresponds to 100 mA cm at a voltage of 1.5 V vs. RHE. -2 The current density was high, showing good HMF oxidation performance.

[0039] Example 3

[0040] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut the nickel foam into 2.5cm×3.5cm pieces and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Weigh 0.121g of copper nitrate, no cobalt nitrate, 0.111g of ammonium fluoride and 0.36g of urea, mix them with 40ml of deionized water and stir evenly to obtain a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam, then place the hydrothermal reactor in a constant temperature oven and hydroheat at 120°C for 6 hours. After the hydrothermal reaction, cool it naturally to room temperature in the oven and open the hydrothermal reactor to obtain a copper-doped integral composite material. Rinse the copper-doped integral composite material obtained in step 2 with ethanol and place it in an oven at 50°C for 15 minutes without subsequent phosphating process.

[0041] The composite catalytic material obtained above was used as the anode, a commercial Pt sheet electrode was used as the cathode, and a saturated Ag / AgCl reference electrode was used. 15 ml of 1 M KOH and 95 mg of HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material. Figure 3 The long dashed line shows that when only copper is added, its electrochemical performance is significantly higher than that of pure nickel foam. Figure 5 It can be seen that the synthesized copper-doped monolithic composite material has an anode Faradaic efficiency of 97.1%.

[0042] Example 4

[0043] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut the nickel foam into 2.5 cm x 3.5 cm pieces and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Mix 0.291g of copper nitrate, 0.111g of ammonium fluoride, and 0.36g of urea with 40ml of deionized water and stir thoroughly to produce a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam, then place the hydrothermal reactor in a constant temperature oven at 120°C for 6 hours. After the hydrothermal reaction, cool the preform to room temperature in the oven and open the hydrothermal reactor to obtain a cobalt-doped monolithic composite material preform. Rinse the cobalt-doped monolithic composite material preform obtained in step 2 with ethanol and dry it in an oven at 50°C for 15 minutes. Cut a 1cm x 1.5cm piece of the hydrothermal preform, place it in a porcelain bowl, and add 0.5g of sodium hypophosphite monohydrate. The porcelain is placed in a tube furnace and calcined at 300°C for 1 hour, using argon as a protective gas at a flow rate of 20 ml / min. After calcination, a cobalt-doped nickel phosphide monolithic composite material is obtained.

[0044] The composite catalytic material obtained above was used as the anode, the commercial Pt sheet electrode was used as the cathode, and the reference electrode was saturated Ag / AgCl. 15 ml of 1 M KOH and 95 mg of HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material. Figure 3 It can be seen that the onset potential of the cobalt-doped nickel phosphide overall composite material is also very close to the theoretical potential of water splitting 1.23V.

[0045] Example 5

[0046] The nickel foam was washed with clean water and dried in an oven at 60°C for 30 minutes. The nickel foam was cut into 2.5 cm x 3.5 cm pieces using a blade and placed vertically in a polytetrafluoroethylene hydrothermal reactor. Copper nitrate-free, 0.291 g cobalt nitrate, 0.111 g ammonium fluoride, and 0.36 g urea were mixed with 40 ml of deionized water and stirred to obtain a raw material solution. This raw material solution was poured into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam. The hydrothermal reactor was then placed in a thermostatic oven and hydrothermalized at 150°C for 4 hours. After the hydrothermal reaction, the reaction mixture was naturally cooled to room temperature in the oven and the hydrothermal reactor was opened to obtain a cobalt-doped monolithic composite material. The cobalt-doped monolithic composite material obtained in step 2 was rinsed with ethanol and dried in an oven at 50°C for 15 minutes without subsequent phosphating. The resulting composite catalyst was used as the anode, a commercial Pt sheet electrode was used as the cathode, and a saturated Ag / AgCl reference electrode was used. Add 15 ml of 1M KOH and 95 mg of HMF into the electrolytic cell, turn on the electrochemical workstation, and test the catalytic performance of the material. Figure 5 It can be seen that the synthesized copper-doped monolithic composite material has an anode Faradaic efficiency of 98.2%.

[0047] Example 6

[0048] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut 2.5 cm x 3.5 cm pieces of nickel foam and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Weigh 0.121 g of copper chloride, 0.291 g of cobalt chloride hexahydrate, 0.111 g of ammonium bifluoride, and 0.05 g of potassium hydroxide, mix them with 40 ml of deionized water, and stir thoroughly to obtain a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam. The hydrothermal reactor is then placed in a thermostatic oven and hydrothermalized at 120°C for 4 hours. After the hydrothermal reaction, cool naturally to room temperature in the oven and then open the hydrothermal reactor to obtain a copper- and cobalt-doped monolithic composite preform. Rinse the resulting copper- and cobalt-doped monolithic composite preform with ethanol and dry it in an oven at 50°C for 15 minutes. Cut a 1 cm x 2 cm piece of the hydrothermal preform, place it in a porcelain bowl, and add 0.5 g of sodium phosphate. The porcelain is placed in a tube furnace and calcined at 250°C for 1 hour using argon as a protective gas at a flow rate of 20 ml / min. After calcination, a copper- and cobalt-doped nickel phosphide monolithic composite material is obtained.

[0049] The composite catalytic material obtained above was used as the anode, the commercial Pt sheet electrode was used as the cathode, and the reference electrode was saturated Ag / AgCl. 15 ml of 1 M KOH and 95 mg of HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material. Figure 4 As shown in Figure 3, there was no significant decrease in current density during 9 18-h constant voltage tests, demonstrating good electrochemical stability.

[0050] Example 7

[0051] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut 2.5 cm x 3.5 cm pieces of nickel foam and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Weigh 0.121 g of copper chloride, 0.291 g of cobalt chloride hexahydrate, 0.111 g of ammonium bifluoride, and 0.05 g of potassium hydroxide, mix them with 40 ml of deionized water, and stir thoroughly to obtain a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam. The hydrothermal reactor is then placed in a thermostatic oven and hydrothermalized at 120°C for 5 hours. After the hydrothermal reaction, cool the reaction mixture to room temperature in the oven and then open the hydrothermal reactor to obtain a copper- and cobalt-doped monolithic composite preform. Rinse the resulting copper- and cobalt-doped monolithic composite preform with ethanol and dry it in an oven at 50°C for 15 minutes. Cut a 1 cm x 2 cm piece of the hydrothermal preform, place it in a porcelain bowl, and add 0.5 g of sodium phosphate. The porcelain is placed in a tube furnace and calcined at 250°C for 1 hour, using argon as a protective gas at a flow rate of 25 ml / min. After calcination, a copper- and cobalt-doped nickel phosphide monolithic composite material is obtained.

[0052] The composite catalytic material obtained above was used as the anode, a commercial Pt sheet electrode was used as the cathode, and a saturated Ag / AgCl reference electrode was used. 15 ml of 1 M KOH and 95 mg of HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material.

[0053] Example 8

[0054] Wash the nickel foam with clean water, place it in an oven, and dry it at 60°C for 30 minutes. Use a blade to cut 2.5 cm x 3.5 cm pieces of nickel foam and place them vertically in a polytetrafluoroethylene hydrothermal reactor. Weigh 0.121 g of copper chloride, 0.291 g of cobalt chloride hexahydrate, 0.111 g of ammonium bifluoride, and 0.05 g of potassium hydroxide, mix them with 40 ml of deionized water, and stir thoroughly to obtain a raw material solution. Pour the raw material solution into the polytetrafluoroethylene hydrothermal reactor containing the nickel foam. The hydrothermal reactor is then placed in a thermostatic oven and hydrothermalized at 120°C for 5 hours. After the hydrothermal reaction, cool naturally to room temperature in the oven and then open the hydrothermal reactor to obtain a copper- and cobalt-doped monolithic composite preform. Rinse the resulting copper- and cobalt-doped monolithic composite preform with ethanol and dry it in an oven at 50°C for 15 minutes. Cut a 1 cm x 2 cm piece of the hydrothermal preform, place it in a porcelain bowl, and add 0.5 g of potassium phosphate. The porcelain is placed in a tube furnace and calcined at 350°C for 1 hour, using argon as a protective gas at a flow rate of 25 ml / min. After calcination, a copper- and cobalt-doped nickel phosphide monolithic composite material is obtained.

[0055] The composite catalytic material obtained above was used as the anode, the commercial Pt sheet electrode was used as the cathode, and the reference electrode was saturated Ag / AgCl. 1M KOH and 95mg HMF were added to the electrolytic cell, and the electrochemical workstation was turned on to test the catalytic performance of the material. Figure 5 As shown, the anode faradaic efficiency of Examples 1-8 is maintained above 98%, which indicates that the synthesized composite catalytic material has good selectivity for HMF oxidation reaction.

[0056] Example 9 (this example is a blank control)

[0057] Wash the nickel foam with clean water, place it in an oven, and dry it at 60℃ for 30 minutes. Use the dried nickel foam directly as the anode, use a commercial Pt sheet electrode as the cathode, and use a saturated Ag / AgCl reference electrode. Add 15ml of 1M KOH and 95mg of HMF to the electrolytic cell, turn on the electrochemical workstation, and test the catalytic performance of the material. Figure 3 It can be seen that the short dot-dashed line represents the HMF oxidation performance of the nickel foam substrate. Compared with the composite catalysts of Examples 1-5 above, the electrochemical performance of the pure nickel foam substrate is significantly worse than that of the composite catalyst.

[0058] The above-described embodiments merely express the implementation methods of the present invention, but should not be understood as limiting the scope of the patent of the present invention. It should be pointed out that for those skilled in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. An application of a transition metal-doped nickel phosphide monolithic composite electrocatalytic material, characterized in that the transition metal-doped nickel phosphide monolithic composite catalytic material is applied in a 5-hydroxymethylfurfural (HMF)-assisted water electrolysis hydrogen production reaction; The nickel phosphide integral composite electrocatalytic material is prepared by the following steps: The first step is to prepare the transition metal-doped overall composite material pre-product 1.1) Dissolve copper salt and cobalt salt in water to obtain a salt solution, then add ammonium fluoride and urea to the salt solution, and stir evenly to obtain an alkaline raw material solution; wherein, Add 0-0.291g of cobalt salt and 0-0.121g of copper salt to every 40ml of water; 1.2) placing the nickel foam in a hydrothermal kettle lined with polytetrafluoroethylene, adding the above-mentioned raw material solution, placing the hydrothermal kettle in water for ultrasonic treatment, and conducting a constant-temperature hydrothermal reaction; after the hydrothermal reaction, naturally cooling to room temperature in an oven, opening the hydrothermal kettle, and rinsing to obtain a transition metal-doped monolithic composite material pre-product; wherein the constant-temperature hydrothermal reaction temperature is 120°C-150°C, and the reaction time is 4-6 hours; The second step is to prepare transition metal-doped nickel phosphide overall composite catalytic material 2.1) placing the transition metal-doped monolithic composite material pre-product obtained in the first step into an oven for drying; 2.2) placing the dried pre-product in a porcelain state and adding a phosphate salt, with the phosphate salt being placed on one side of the pre-product and close to the pre-product, wherein for every 0.09-0.1 g of the pre-product, 0-0.5 g of the phosphate salt is added; then placing the porcelain state in a tube furnace, introducing argon as a protective gas, and performing a phosphating treatment at 250-350° C. for 0-1 h, followed by rinsing and drying to obtain a transition metal-doped nickel phosphide monolithic composite catalytic material; wherein, The flow rate of argon is controlled at 20-25 ml / min, and in order to ensure sufficient phosphating, the flow of argon must first pass through the phosphate salt and then through the pre-product.

2. The use of a transition metal-doped nickel phosphide integral composite catalytic material according to claim 1, characterized in that the ammonium fluoride in step 1.1) is replaced by ammonium bifluoride, and the urea is replaced by potassium hydroxide.

3. The use of a transition metal-doped nickel phosphide integral composite catalytic material according to claim 1, characterized in that: In the step 1.1), the cobalt salt is one of cobalt nitrate hexahydrate and cobalt chloride hexahydrate; and the copper salt is one of copper nitrate trihydrate and copper chloride.

4. The use of a transition metal-doped nickel phosphide integral composite catalytic material according to claim 3, characterized in that: In the step 1.1), the cobalt salt is cobalt nitrate hexahydrate; the copper salt is copper nitrate trihydrate; the concentrations of the cobalt nitrate hexahydrate, copper nitrate trihydrate, ammonium fluoride, and urea are preferably 0-1 mmol / L, 0-0.5 mmol / L, 3 mmol / L, and 6 mmol / L, respectively.

5. The use of a transition metal-doped nickel phosphide integral composite catalytic material according to claim 1, characterized in that: In the step 2.2), the phosphate salt is one of sodium phosphate, sodium hypophosphite monohydrate, and potassium phosphate.

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