Self-supporting composite photoelectrode material with vanadium nitride / bismuth tungstate coating deposited on surface of carbon-carbon composite material and preparation method of self-supporting composite photoelectrode material

Abstract

The invention provides a vanadium nitride / bismuth tungstate coating photoelectrode material deposited on the surface of a carbon-carbon composite material and a method, and relates to the field of design of photoelectrocatalytic materials.The method comprises the steps that bismuth tungstate and vanadium nitride are dispersed in a dispersing agent, then iodine is added, the mixture is mixed to be uniform, and first suspension liquid and second suspension liquid are obtained; and immersing a carbon-carbon composite material into the first suspension liquid, carrying out electrophoretic arc discharge deposition for 1-5 minutes under the voltage of 50-100 V, then immersing the carbon-carbon composite material into the second suspension liquid, carrying out electrophoretic arc discharge deposition for 1-5 minutes under the voltage of 50-100 V, and then drying to obtain the vanadium nitride / bismuth tungstate coating photoelectrode material deposited on the surface of the carbon-carbon composite material, and high-efficiency photoelectrocatalysis water decomposition hydrogen evolution is realized.

Description

Technical Field

[0001] The present invention relates to the field of design of photocatalytic materials, and particularly to a self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material and a preparation method therefor. Background Art

[0002] Photocatalytic water splitting is a technology that uses light energy to drive the decomposition of water to produce hydrogen and oxygen, and has important energy and environmental application prospects. In this process, the photocathode, as a key component, is responsible for receiving photo-generated electrons and catalyzing the reduction of protons to hydrogen, and its performance directly affects the efficiency and stability of the system. An ideal photocathode material needs to have a suitable bandgap to effectively absorb visible light, good electrical conductivity to quickly transport electrons, high catalytic activity to promote proton reduction, and good chemical stability to work in the electrolyte for a long time.

[0003] Bismuth tungstate (Bi2WO6) is a visible-light-responsive semiconductor with a narrow bandgap (2.7–2.8 eV). Its layered perovskite structure and suitable energy band positions provide a basis for photocatalytic water splitting. Although it has advantages such as strong light absorption ability and low cost, problems such as fast recombination of photo-generated carriers and insufficient surface reaction kinetics limit its efficiency. By constructing heterojunctions (such as Bi2WO6 / g-C3N4), loading cocatalysts, or regulating nanostructures and other strategies, the charge separation and catalytic activity can be significantly improved, promoting its application in photocatalytic water splitting. However, the improvement effect of charge separation and catalytic activity cannot meet the current needs and it is difficult to be widely promoted.

[0004] Vanadium nitride (VN) is a transition metal nitride with high electrical conductivity. Although it does not have a semiconductor bandgap, its excellent charge transport ability and chemical stability make it an ideal cocatalyst for improving the performance of photocatalytic water splitting. By constructing a composite structure with a semiconductor material (such as TiO2), VN can significantly enhance the separation efficiency of photo-generated charges and accelerate the reaction kinetic process, and the corrosion resistance and wide pH adaptability of VN further improve the stability of the composite system. Based on these beneficial effects, theoretically, combining it with bismuth tungstate can construct a VN / Bi2WO6 heterojunction, thereby achieving higher charge separation and catalytic activity effects and realizing efficient photocatalytic water splitting for hydrogen evolution. However, there is no relevant report on how to construct the heterostructure specifically to achieve ideal interface regulation and thus verify the above conclusion. Summary of the Invention

[0005] Aiming at the problems existing in the prior art, the present invention provides a self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material and a preparation method thereof, so as to solve the problem that the vanadium nitride / bismuth tungstate heterostructure cannot be constructed at present. The VN / Bi2WO6 coating structure is synthesized on a high-density C / C substrate by an arc discharge deposition technique to form a bismuth tungstate / vanadium nitride heterojunction, which is beneficial to improving the optoelectronic performance of single bismuth tungstate.

[0006] The present invention is realized by the following technical solutions:

[0007] A preparation method of a self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material, comprising the following steps:

[0008] S1, dispersing bismuth tungstate and vanadium nitride in a dispersant respectively, and then adding iodine respectively and mixing evenly. The mass ratio of vanadium nitride to bismuth tungstate is (0.2 - 0.3):(0.2 - 0.3) to obtain a first suspension and a second suspension;

[0009] S2, immersing the carbon-carbon composite material in the first suspension, and performing electrophoretic arc discharge deposition at a voltage of 50 - 100V for 1 - 5min to obtain a composite A;

[0010] S3, immersing the composite A in the second suspension, performing electrophoretic arc discharge deposition at a voltage of 50 - 100V for 1 - 5min, and then drying to obtain a self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of the carbon-carbon composite material.

[0011] Preferably, in S1, the dispersant is ethylene glycol, isopropyl alcohol, deionized water or acetone. The ratio of bismuth tungstate to the dispersant in the first suspension is (0.2 - 0.3)g:(100 - 150)ml, and the ratio of vanadium nitride to the dispersant in the second suspension is (0.2 - 0.3)g:(100 - 150)ml.

[0012] Preferably, the mass ratio of bismuth tungstate to iodine in the first suspension is (0.2 - 0.3):(0.2 - 0.3), and the ratio of vanadium nitride to iodine in the second suspension is (0.2 - 0.3):(0.2 - 0.3).

[0013] Preferably, the bismuth tungstate in S1 is obtained by the following process:

[0014] Adding nitric acid to a bismuth nitrate pentahydrate solution to obtain a first mixed solution. The ratio of bismuth nitrate pentahydrate, deionized water and nitric acid in the first mixed solution is (0.4 - 2)g:(40 - 70)mL:(1.5 - 15)mmol;

[0015] Subsequently, sodium tungstate dihydrate is added to the first mixed solution to obtain a second mixed solution. The mass ratio of bismuth nitrate pentahydrate to sodium tungstate dihydrate in the second mixed solution is (0.4 - 2):(0.1 - 1). Then, it is mixed evenly to obtain a precursor solution;

[0016] The precursor solution is subjected to a hydrothermal reaction, and then the product therein is washed and dried to obtain the bismuth tungstate.

[0017] Preferably, the temperature during the hydrothermal reaction of the precursor solution is 120 - 190 °C, and the time is 10 - 16 h.

[0018] Preferably, the vanadium nitride in S1 is obtained as follows:

[0019] Ammonia water with a mass percentage of 5% is added to the vanadium chloride solution. The ratio of vanadium chloride to ammonia water is (0.40 - 0.55) g:(5 - 10) mL. Then, a hydrogen peroxide solution with a volume percentage of 30% is added and mixed evenly to obtain a first mixed system;

[0020] Ethanol is added to the first mixed system and mixed evenly to obtain a second mixed system. The second mixed system is subjected to hydrothermal treatment, and then the product therein is washed and dried to obtain a powder;

[0021] The powder and dicyandiamide are mixed evenly according to a mass ratio of 1:(2 - 4) to obtain a mixture. The mixture is heated to 700 - 900 °C in an Ar atmosphere and then subjected to heat preservation treatment to obtain the vanadium nitride.

[0022] Preferably, the ratio of vanadium chloride to deionized water in the vanadium chloride solution is (0.40 - 0.55) g:(15 - 25) mL. The volume ratio of the vanadium chloride solution, hydrogen peroxide solution, and ethanol is (15 - 25):(5 - 10):(20 - 30) to obtain a second mixed system;

[0023] The temperature during the hydrothermal treatment of the second mixed system is 90 - 110 °C, and the time is 10 - 16 h.

[0024] Preferably, after the mixture is heated from room temperature to 700 - 900 °C, it is heat-preserved for 2 - 4 h, and the heating rate is 5 - 10 °C / min to obtain the vanadium nitride.

[0025] Preferably, the carbon-carbon composite material in S2 is obtained as follows:

[0026] The initial carbon-carbon composite material is subjected to ultrasonic treatment successively with concentrated hydrochloric acid, deionized water, and absolute ethanol to obtain the carbon-carbon composite material.

[0027] A self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material prepared by the preparation method of the self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material described in any one of the above. The bismuth tungstate is stacked on the surface of the carbon-carbon composite material in a flaky manner, and vanadium nitride is attached to the surface of the bismuth tungstate, and vanadium nitride and bismuth tungstate form a heterojunction coating.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] The preparation method of the self-supporting composite photoanode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material of the present invention uses a C / C composite material as a carrier, and has the advantages of high specific surface area, excellent electrical conductivity, good chemical stability, high temperature resistance, light weight, strong designability and environmental friendliness in photocatalytic water splitting. These characteristics make it have good application prospects in the field of clean energy. The VN / Bi2WO6 heterojunction synthesized by electrophoretic arc discharge deposition on the C / C composite material. Adding iodine to the suspension can adsorb on the surfaces of bismuth tungstate and vanadium nitride particles, change their potentials, and enhance the electrostatic repulsion between particles, thus preventing agglomeration. Iodine, as an electrolyte, dissociates into I- or I3- ions, increasing the ion concentration and electrical conductivity of the solution. This helps to form a stable electric field during electrophoresis, promotes the directional migration and efficient deposition of charged particles. First, it is deposited in the suspension containing bismuth tungstate. The bismuth tungstate can be stacked on the surface of the carbon-carbon composite material in a flaky manner, exposing a large specific surface area, which is beneficial to the generation of photogenerated carrier pairs. Then, it is deposited in the suspension containing vanadium nitride. The vanadium nitride is attached to the surface of the bismuth tungstate, providing more active sites, which is beneficial to the transport of photogenerated electrons and the occurrence of surface hydrogen evolution reduction reaction. The outer layer of VN accelerates the migration of photogenerated electrons from the middle layer Bi2WO6 to the catalytic interface by virtue of its high electrical conductivity, thereby inhibiting carrier recombination. At the same time, its surface nitrogen vacancies and metal-like properties regulate the band bending through the Schottky effect, significantly reducing the overpotential of the hydrogen evolution reaction. The present invention combines light absorption, charge directional transport and catalytic active site optimization to achieve efficient photocatalytic water splitting for hydrogen production. By using electrophoretic arc discharge deposition technology, through precise control of the deposition voltage and time, a VN / Bi2WO6 heterojunction coating is directionally constructed on the surface of the C / C composite material, and the thickness of the coating is controlled, realizing efficient photocatalytic water splitting for hydrogen production, providing a guarantee for the design of an efficient catalytic layer on the photoanode surface. Description of the Drawings

[0030] Figure 1a X-ray diffraction analysis diagram of Bi2WO6 prepared in Example 1 of the present invention.

[0031] Figure 1b X-ray diffraction analysis diagram of VN prepared in Example 1 of the present invention.

[0032] Figure 2 Scanning diagram of VN / Bi2WO6-C / C prepared in Example 1 of the present invention.

[0033] Figure 3 LSV (linear sweep voltammetry curve) of C / C, Bi2WO6-C / C and VN / Bi2WO6-C / C in Example 1 of the present invention in a solution with pH = 9.5 under simulated sunlight.

[0034] Figure 4 Impedance fitting curve of VN / Bi2WO6-C / C prepared in Example 1 of the present invention in a solution with pH = 9.5 under simulated sunlight. Detailed implementation manners

[0035] The following further elaborates on the present invention in conjunction with specific embodiments, which is an explanation rather than a limitation of the present invention.

[0036] A preparation method of a self-supporting composite photoanode material with a vanadium nitride / tungstic acid bismuth coating deposited on the surface of a carbon-carbon composite material of the present invention includes the following steps:

[0037] Step 1: Add 0.4 - 2 g of bismuth nitrate pentahydrate to 40 - 70 mL of deionized water, magnetically stir at a rotation speed of 300 - 1000 r / min for 20 - 60 min to obtain solution A. Add 3 - 10 mL of a nitric acid solution with a concentration of 0.5 - 1.5 mol / L to solution A, and ultrasonically stir for 10 - 30 min to obtain solution B. Add 0.1 - 1 g of sodium tungstate dihydrate to solution B, magnetically stir at a rotation speed of 300 - 1000 r / min for 20 - 60 min to obtain solution C. Transfer the mixed solution C to a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, heat to 120 - 190 °C for hydrothermal reaction for 10 - 16 h, naturally cool to room temperature, centrifuge and wash the hydrothermal reaction product, and dry at 60 - 90 °C for 8 - 14 h to obtain powder D.

[0038] Step 2: Weigh 0.40 - 0.55 g of vanadium chloride, disperse it in 15 - 25 mL of deionized water, dropwise add 5 - 10 mL of 5 wt% dilute ammonia water, and magnetically stir for 30 - 60 minutes to prepare solution E. Measure 5 - 10 mL of a hydrogen peroxide solution with a volume percentage of 30% and add it to solution E, and magnetically stir for 6 - 7 hours to prepare solution F. Measure 20 - 30 mL of ethanol and dropwise add it to solution F, and fully stir for 30 - 60 minutes to prepare solution G. Transfer solution G to a 100 mL polytetrafluoroethylene reaction kettle, carry out hydrothermal reaction at 90 °C - 110 °C for 10 - 16 h, wash the obtained product with deionized water and ethanol, vacuum filter, and dry at 60 °C to obtain powder H.

[0039] Step 3, powder H and dicyandiamide are mixed in a mass ratio of 1: (2-4), the mixed powder is fully ground and mixed, and then placed in an alumina porcelain boat, heated to 700-900° C. in an Ar atmosphere using a tube furnace and maintained for 2-4 hours at a heating rate of 5-10° C. / min, and cooled to room temperature to obtain powder I;

[0040] Step 4: weigh 0.2-0.3 g of powder D and I respectively and place them in two beakers, add 100-150 ml of ethylene glycol to each beaker, stir magnetically until evenly dispersed, then add 0.2-0.3 g of iodine, continue stirring until evenly dispersed (the iodine has dissolved at this time) to obtain suspension J and suspension K; place a high-density substrate (1.6-1.9 g / cm 3 ) The C / C composite material was ultrasonically pretreated with concentrated hydrochloric acid, water and anhydrous ethanol in sequence, fixed on the negative electrode of the deposition equipment after drying, and then placed in suspensions J and K in sequence without cleaning in the intermediate process. A voltage of 50-100V was applied each time for electrophoretic arc discharge deposition for 1-5 minutes. The self-supporting sample after two depositions was placed in an oven to dry, and finally the VN / Bi2WO6-C / C photoelectrode material was obtained.

[0041] Example 1

[0042] A method for preparing a self-supporting composite photoelectrode material (VN / Bi2WO6-C / C photoelectrode material) with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material, specifically comprising the following steps:

[0043] Step 1, adding 0.53g of bismuth nitrate pentahydrate to 50mL of deionized water, stirring magnetically at a speed of 800r / min for 30min to obtain solution A, adding 3mL of 1.5mol / L nitric acid solution to solution A, ultrasonicating for 30min to obtain solution B, adding 0.18g of sodium tungstate dihydrate to solution B, stirring magnetically at a speed of 800r / min for 30min to obtain solution C, transferring the mixed solution C to a polytetrafluoroethylene-lined autoclave, heating to 160°C for hydrothermal reaction for 12h, cooling naturally to room temperature, centrifuging the hydrothermal reaction product, washing, and drying at 70°C for 10h to obtain powder D;

[0044] Step 2, weighing 0.40g of vanadium chloride and dispersing it into 15mL of deionized water, adding 5mL of ammonia water dropwise, and magnetically stirring for 30 minutes to prepare solution E, measuring 5mL of 30% by volume hydrogen peroxide solution and adding it to solution E, magnetically stirring for 6 hours to prepare solution F, measuring 20mL of ethanol and adding it dropwise to solution F, stirring it thoroughly for 30 minutes to prepare solution G, transferring solution G into a 100mL polytetrafluoroethylene reactor and performing hydrothermal reaction at 90°C for 16h, washing the obtained product with deionized water and ethanol, vacuum filtering, and drying at 60°C to obtain powder H;

[0045] Step 3: Weigh 0.3 g of powder H and 1 g of dicyandiamide. After thoroughly grinding and mixing the mixed powder, put it into an alumina boat. Use a tube furnace to heat it to 700 °C in an Ar atmosphere and maintain for 4 hours, with a heating rate of 5 °C / min. After cooling to room temperature, powder I is obtained.

[0046] Step 4: Weigh 0.2 g of powder D and I respectively and place them in two beakers. Add 100 ml of ethylene glycol to each of the two beakers. After magnetic stirring until evenly dispersed, add 0.2 g of iodine to each. Continue stirring until uniform to obtain suspension J and suspension K. Ultrasonically pretreat the C / C substrate successively with concentrated hydrochloric acid, water, and absolute ethanol, dry it, and fix it at the negative electrode of the electrophoretic deposition equipment. Subsequently, place it in suspension J and K in sequence. Apply a voltage of 50 V each time for electrophoretic arc discharge deposition for 5 min. The self-supporting samples after two depositions are placed in an oven to dry, and finally, the VN / Bi2WO6-C / C photoanode material is obtained (remove suspension K to obtain Bi2WO6-C / C).

[0047] Figure 1a XRD pattern of Bi2WO6 prepared in Example 1. Its diffraction peaks accurately correspond to the Bi2WO6 PDF#39-0256 standard card, indicating that the crystallinity of the sample is very good, there are no other impurities, and the pure phase of Bi2WO6 is successfully prepared.

[0048] Figure 1b XRD pattern of VN prepared in Example 1. Its diffraction peaks accurately correspond to the VN PDF#73-0528 standard card. Similarly, the pure phase of VN is successfully prepared.

[0049] Figure 2 Scanning image of VN / Bi2WO6-C / C prepared in Example 1. It can be clearly seen that two substances with different morphologies form a heterojunction attached to C / C. Bismuth tungstate is stacked in flakes, exposing a large specific surface area, which is beneficial for the generation of photogenerated carrier pairs. Vanadium nitride is attached to the surface of bismuth tungstate and exposed on the surface, providing more active sites, which is beneficial for the transport of photogenerated electrons and the occurrence of surface hydrogen evolution reduction reaction.

[0050] Figure 3 Hydrogen evolution performance diagram of C / C, Bi2WO6-C / C, and VN / Bi2WO6-C / C in Example 1 in a solution with pH = 9.5 under simulated sunlight. It can be seen from the figure that under the condition of 10 mA / cm -2 The overpotential of VN / Bi2WO6-C / C is lower than that of C / C and Bi2WO6-C / C, indicating that VN / Bi2WO6-C / C has better hydrogen evolution performance.

[0051] Figure 4This is the impedance fitting diagram of VN / Bi2WO6-C / C prepared in Example 1. The starting point is close to the origin of the coordinate system, indicating that VN / Bi2WO6-C / C has a small internal resistance, a short charge conduction path, and good conductivity.

[0052] Example 2

[0053] A method for preparing a VN / Bi2WO6-C / C photoelectrode material, specifically comprising the following steps:

[0054] Step 1, adding 1.06g of bismuth nitrate pentahydrate to 60mL of deionized water, stirring magnetically at a speed of 600r / min for 40min to obtain solution A, adding 5mL of 1.0mol / L nitric acid solution to solution A, ultrasonicating for 20min to obtain solution B, adding 0.24g of sodium tungstate dihydrate to solution B, stirring magnetically at a speed of 600r / min for 40min to obtain solution C, transferring the mixed solution C to a polytetrafluoroethylene-lined autoclave, heating to 140°C for hydrothermal reaction for 14h, cooling naturally to room temperature, centrifuging the hydrothermal reaction product, washing, and drying at 80°C for 8h to obtain powder D;

[0055] Step 2, weighing 0.55g of vanadium chloride and dispersing it into 25mL of deionized water, adding 10mL of ammonia water dropwise, and magnetically stirring for 60 minutes to prepare solution E, measuring 10mL of 30% by volume hydrogen peroxide solution and adding it to solution E, magnetically stirring for 7 hours to prepare solution F, measuring 30mL of ethanol and adding it dropwise to solution F, stirring it thoroughly for 60 minutes to prepare solution G, transferring solution G into a 100mL polytetrafluoroethylene reactor and performing hydrothermal reaction at 110°C for 10h, washing the obtained product with deionized water and ethanol, vacuum filtering, and drying at 60°C to obtain powder H;

[0056] Step 3, weighing 0.3 g of powder H and 1.2 g of dicyandiamide, grinding and mixing the mixed powders thoroughly, and then putting them into an alumina porcelain boat, heating them to 900° C. in an Ar atmosphere in a tube furnace and maintaining them for 2 hours at a heating rate of 5° C. / min, and cooling them to room temperature to obtain powder I;

[0057] Step 4, weigh 0.3g of powder D and I respectively and place them in two beakers, add 150ml of ethylene glycol to each of the two beakers, stir magnetically until evenly dispersed, then add 0.3g of iodine each, continue stirring until evenly dispersed to obtain suspension J and suspension K; the C / C substrate is ultrasonically pretreated with concentrated hydrochloric acid, water and anhydrous ethanol in turn, fixed on the negative electrode of the electrophoretic deposition equipment after drying, and then placed in suspensions J and K in turn, applying a voltage of 80V each time for electrophoretic arc discharge deposition for 1min, and the self-supporting sample after two depositions is placed in an oven to dry, and finally the VN / Bi2WO6-C / C photoelectrode material is obtained.

[0058] Example 3

[0059] A preparation method of VN / Bi2WO6-C / C photoanode material specifically includes the following steps:

[0060] Step 1: Add 0.53 g of bismuth nitrate pentahydrate to 70 mL of deionized water, magnetically stir at a speed of 500 r / min for 60 min to obtain solution A. Add 8 mL of nitric acid solution with a concentration of 0.8 mol / L to solution A, ultrasonically stir for 20 min to obtain solution B. Add 0.12 g of sodium tungstate dihydrate to solution B, magnetically stir at a speed of 500 r / min for 60 min to obtain solution C. Transfer the mixed solution C to a high-pressure reaction kettle with a polytetrafluoroethylene inner liner, heat to 180 °C for hydrothermal reaction for 12 h, naturally cool to room temperature, centrifuge and wash the hydrothermal reaction product, and dry at 60 °C for 14 h to obtain powder D;

[0061] Step 2: Weigh 0.55 g of vanadium chloride, disperse it in 25 mL of deionized water, add 10 mL of ammonia water dropwise, and magnetically stir for 60 minutes to prepare solution E. Measure 10 mL of hydrogen peroxide solution with a volume percentage of 30% and add it to solution E, magnetically stir for 7 hours to prepare solution F. Measure 30 mL of ethanol and add it dropwise to solution F, stir thoroughly for 60 minutes to prepare solution G. Transfer solution G to a 100 mL polytetrafluoroethylene reaction kettle, carry out hydrothermal reaction at 100 °C for 14 h, wash the obtained product with deionized water and ethanol, vacuum filter, and dry at 60 °C to obtain powder H;

[0062] Step 3: Weigh 0.2 g of powder H and 1 g of dicyandiamide, thoroughly grind and mix the mixed powder, put it into an alumina porcelain boat, use a tube furnace to heat to 900 °C in an Ar atmosphere and maintain for 2 hours, with a heating rate of 5 °C / min, and obtain powder I after cooling to room temperature;

[0063] Step 4: Weigh 0.25 g of powder D and I respectively and place them in two beakers. Add 130 ml of ethylene glycol to each of the two beakers, magnetically stir until evenly dispersed, then add 0.25 g of iodine to each, and continue to stir until evenly mixed to obtain suspension J and suspension K; Pre-treat the C / C substrate with concentrated hydrochloric acid, water, and absolute ethanol by ultrasonic treatment in sequence, dry it and fix it on the negative electrode of the electrophoretic deposition equipment, and then place it in suspension J and K in sequence. Apply a voltage of 75 V for electrophoretic arc discharge deposition for 3 min each time. The self-supporting sample after two depositions is placed in an oven to dry, and finally obtain the VN / Bi2WO6-C / C photoanode material.

[0064] Example 4

[0065] A preparation method of VN / Bi2WO6-C / C photoanode material specifically includes the following steps:

[0066] Step 1: Add 1.06 g of bismuth nitrate pentahydrate into 50 mL of deionized water, and magnetically stir for 20 min at a rotation speed of 1000 r / min to obtain solution A. Add 10 mL of nitric acid solution with a concentration of 0.5 mol / L into solution A, and ultrasonically treat for 20 min to obtain solution B. Add 0.36 g of sodium tungstate dihydrate into solution B, and magnetically stir for 20 min at a rotation speed of 1000 r / min to obtain solution C. Transfer the mixed solution C into a high-pressure reaction kettle with a polytetrafluoroethylene liner, heat to 170 °C for hydrothermal reaction for 12 h, naturally cool to room temperature, centrifuge and wash the hydrothermal reaction product, and dry at 60 °C for 14 h to obtain powder D;

[0067] Step 2: Weigh 0.55 g of vanadium chloride and disperse it in 25 mL of deionized water. Dropwise add 8 mL of ammonia water and magnetically stir for 50 minutes to prepare solution E. Measure 8 mL of hydrogen peroxide solution with a volume percentage of 30% and add it into solution E, and magnetically stir for 6 hours to prepare solution F. Measure 20 mL of ethanol and dropwise add it into solution F, and fully stir for 60 minutes to prepare solution G. Transfer solution G into a 100 mL polytetrafluoroethylene reaction kettle and carry out hydrothermal reaction at 110 °C for 14 h. Wash the obtained product with deionized water and ethanol, vacuum filter, and dry at 60 °C to obtain powder H;

[0068] Step 3: Weigh 0.25 g of powder H and 1 g of dicyandiamide. After thoroughly grinding and mixing the mixed powder, put it into an alumina boat, use a tube furnace to heat to 700 °C in an Ar atmosphere and maintain for 4 hours, with a heating rate of 5 °C / min. After cooling to room temperature, obtain powder I;

[0069] Step 4: Weigh 0.3 g of powder D and I respectively and place them in two beakers. Add 130 ml of ethylene glycol to each of the two beakers, magnetically stir until evenly dispersed, then add 0.3 g of iodine to each, and continue to stir until evenly mixed to obtain suspension J and suspension K; Ultrasonically pretreat the C / C substrate successively with concentrated hydrochloric acid, water and absolute ethanol, dry it and fix it at the negative electrode of the electrophoretic deposition equipment, and then place it in suspension J and K successively. Apply a voltage of 60 V for electrophoretic arc discharge deposition for 4 min each time. The self-supporting samples after two depositions are placed in an oven to dry, and finally obtain the VN / Bi2WO6-C / C photoanode material.

Claims

1. A method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material, characterized in that: The following steps are involved: S1, dispersing bismuth tungstate and vanadium nitride in a dispersant respectively, and then adding iodine respectively and mixing them evenly, the mass ratio of vanadium nitride to bismuth tungstate is (0.2-0.3): (0.2-0.3), to obtain a first suspension and a second suspension; S2, immersing the carbon-carbon composite material in the first suspension, and performing electrophoretic arc discharge deposition at a voltage of 50-100 V for 1-5 min to obtain a composite A; S3, immersing the complex A in the second suspension, performing electrophoretic arc discharge deposition at a voltage of 50-100 V for 1-5 min, and then drying to obtain a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of the carbon-carbon composite material.

2. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 1, characterized in that: In S1, the dispersant is ethylene glycol, isopropanol, deionized water or acetone, the ratio of bismuth tungstate to dispersant in the first suspension is (0.2-0.3) g: (100-150) ml, and the ratio of vanadium nitride to dispersant in the second suspension is (0.2-0.3) g: (100-150) ml.

3. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 2, characterized in that: The mass ratio of bismuth tungstate to iodine in the first suspension is (0.2-0.3):(0.2-0.3), and the mass ratio of vanadium nitride to iodine in the second suspension is (0.2-0.3):(0.2-0.3).

4. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 1, characterized in that: The bismuth tungstate described in S1 is obtained by the following process: Adding nitric acid to the bismuth nitrate pentahydrate solution to obtain a first mixed solution, wherein the ratio of bismuth nitrate pentahydrate, deionized water and nitric acid in the first mixed solution is (0.4-2) g: (40-70) mL: (1.5-15) mmol; Then, sodium tungstate dihydrate is added to the first mixed solution to obtain a second mixed solution, wherein the mass ratio of bismuth nitrate pentahydrate to sodium tungstate dihydrate in the second mixed solution is (0.4-2): (0.1-1), and then the mixture is mixed evenly to obtain a precursor solution; The precursor solution is subjected to a hydrothermal reaction, and the product is washed and dried to obtain the bismuth tungstate.

5. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 4, characterized in that: The temperature of the precursor solution during hydrothermal reaction is 120-190° C. and the time is 10-16 hours.

6. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 1, characterized in that: The vanadium nitride described in S1 is obtained by the following process: Adding 5% by mass of ammonia water to the vanadium chloride solution, wherein the ratio of the vanadium chloride to the ammonia water is (0.40-0.55) g: (5-10) mL, and then adding 30% by volume of hydrogen peroxide solution and mixing evenly to obtain a first mixed system; Add ethanol to the first mixed system and mix evenly to obtain a second mixed system, subject the second mixed system to hydrothermal treatment, and then wash and dry the product therein to obtain a powder; The powder and dicyandiamide are mixed at a mass ratio of 1:(2-4) to obtain a mixture, and the mixture is heated to 700-900° C. in an Ar atmosphere, and then subjected to heat preservation treatment to obtain the vanadium nitride.

7. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 6, characterized in that: The ratio of vanadium chloride to deionized water in the vanadium chloride solution is (0.40-0.55) g: (15-25) mL, and the volume ratio of the vanadium chloride solution, the hydrogen peroxide solution and ethanol is (15-25): (5-10): (20-30) to obtain a second mixed system; The temperature of the second mixed system during hydrothermal treatment is 90-110° C. and the time is 10-16 hours.

8. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 6, characterized in that: The mixture is heated from room temperature to 700-900° C. and then kept warm for 2-4 hours at a heating rate of 5-10° C. / min to obtain the vanadium nitride.

9. The method for preparing a self-supporting composite photoelectrode material with a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to claim 1, characterized in that: The carbon-carbon composite material in S2 is obtained by the following process: The initial carbon-carbon composite material is ultrasonically treated with concentrated hydrochloric acid, deionized water and anhydrous ethanol in sequence to obtain the carbon-carbon composite material.

10. A self-supporting composite photoelectrode material having a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material obtained by the method for preparing a self-supporting composite photoelectrode material having a vanadium nitride / bismuth tungstate coating deposited on the surface of a carbon-carbon composite material according to any one of claims 1 to 9, characterized in that: The bismuth tungstate is deposited on the surface of the carbon-carbon composite material in a flake-like manner, and the vanadium nitride is attached to the surface of the bismuth tungstate, and the vanadium nitride and the bismuth tungstate form a heterojunction coating.

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