Bismuth tungstate / tungsten carbide-C / C composite photoelectric cathode material and preparation method thereof

Abstract

The invention discloses a bismuth tungstate / tungsten carbide-C / C composite photoelectric cathode material and a preparation method thereof, and belongs to the technical field of photocathode materials, a carbon / carbon composite material is immersed in a mixed water system in which Bi2O3 is dispersed and Na2WO4. 2H2O and CTAB are dissolved, hydrothermal treatment is performed at 140-180 DEG C, and then the carbon / carbon composite material is taken out and cleaned to obtain a precursor; wC powder is dispersed, then iodine is added, the mixture is evenly mixed, and deposition liquid is obtained; and taking the Bi2WO6-C / C composite photoelectric cathode precursor as a negative electrode, carrying out hydrothermal electrophoretic deposition in a deposition solution at the current density of 1-3A / m < 2 >, then taking out and drying to obtain the bismuth tungstate / tungsten carbide-C / C composite photoelectric cathode material which shows relatively strong photoelectrocatalytic hydrogen evolution performance in an alkaline solution.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocathode materials, and relates to a bismuth tungstate / tungsten carbide-C / C composite photocathode material and a preparation method thereof. Background Art

[0002] In the field of photocatalysis, the photocathode plays a key role in capturing photo-generated electrons and participating in chemical reactions, and its applications cover multiple fields such as energy conversion, environmental purification, and organic synthesis. In photocatalytic hydrogen production, as the core component of the photocatalytic reaction, its performance directly determines the utilization efficiency of photo-generated electrons. Therefore, it is crucial to improve the performance of the photocathode.

[0003] Bismuth tungstate (Bi2WO6), as an important inorganic compound and n-type semiconductor material, shows significant application potential in the photocathode in the field of photocatalysis. Bismuth tungstate is an oxide semiconductor material with a direct bandgap (a narrow bandgap of about 2.7 - 2.8 eV), belonging to a direct-type semiconductor. Its crystal presents a layered structure, with tungstate ions and bismuth ions arranged alternately. This ordered layered structure improves the light absorption efficiency, enabling bismuth tungstate to have good electron transport performance and light absorption performance, showing broad application prospects in the optoelectronic field. However, when Bi2WO6 is used as a single material in the photocathode, the recombination rate of photo-generated electrons and holes is relatively high, resulting in a significant reduction in photocatalytic efficiency. At the same time, the utilization of the infrared part of the solar spectrum is insufficient, limiting its photoelectric conversion efficiency as a photocathode.

[0004] Generally, the modification of bismuth tungstate is usually carried out by a composite method. In this regard, after the composite of bismuth tungstate with materials such as Ag2S / AgI, the recombination rate is significantly reduced, and the photocatalytic performance is improved. At the same time, the bandgap of Bi2WO6 can be reduced to 2.14 eV, and the light absorption range is extended to 700 nm, significantly improving the solar energy utilization rate. However, these materials still have the following problems: First, the interfacial compatibility between bismuth tungstate and Ag2S / AgI is poor, resulting in an increase in interfacial resistance and affecting the transport efficiency of photo-generated carriers; Second, as noble metal compounds, the raw material costs of Ag2S and AgI are relatively high; Third, during long-term photocatalytic reactions, Ag2S / AgI will undergo photocorrosion, leading to a decline in the performance of the composite material. Therefore, there is currently a lack of a bismuth tungstate composite modified material with simple preparation, low cost, and stable interface. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides a bismuth tungstate / tungsten carbide-C / C composite photo-cathode material and a preparation method thereof, so as to solve the problem that there is currently a lack of a bismuth tungstate composite modification material with simple preparation, low cost and stable interface. The WC / Bi2WO6 photo-catalytic material is synthesized on the carbon / carbon composite material by a hydrothermal electrophoresis deposition method, and the synthesized WC / Bi2WO6-C / C material exhibits strong photo-catalytic hydrogen evolution performance in an alkaline solution.

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

[0007] A preparation method of a bismuth tungstate / tungsten carbide-C / C composite photo-cathode material, comprising the following steps:

[0008] Step 1, impregnate the carbon / carbon composite material in a mixed water system in which Bi2O3 is dispersed, Na2WO4·2H2O and CTAB are dissolved, perform hydrothermal treatment at 140-180 °C for 20-24 h, and then take out the obtained composite for washing to obtain a Bi2WO6-C / C composite photo-cathode precursor;

[0009] Step 2, disperse the WC powder, and then add iodine and mix evenly. The ratio of the WC powder to Bi2O3 in Step 1 is (0.34-0.72) g:(0.1-0.5) mol to obtain a deposition solution;

[0010] Step 3, use the Bi2WO6-C / C composite photo-cathode precursor as the negative electrode, perform hydrothermal electrophoresis deposition in the deposition solution at a current density of 1-3 A / m 2 , and then take out and dry to obtain a bismuth tungstate / tungsten carbide-C / C composite photo-cathode material.

[0011] A further improvement of the present invention lies in:

[0012] The mixed water system described in Step 1 is obtained according to the following process:

[0013] Disperse Bi2O3 in deionized water, and then add Na2WO4·2H2O and CTAB in sequence for dissolution. The molar ratio of Bi2O3, Na2WO4·2H2O and CTAB is (0.1-0.5):(0.2-0.6):(0.01-0.03), and then ultrasonically treat at room temperature for 30 min-1 h to obtain the mixed water system.

[0014] The WC powder described in Step 2 is obtained according to the following process:

[0015] Mix tungsten powder, carbon black with moisture-removed NaCl and KCl. The molar ratio of tungsten powder to carbon black is (0.01 - 0.05):(0.2 - 1). Then calcine at 800 - 1000 °C for 1 - 3 h to obtain a powder. After removing NaCl and KCl from the powder and drying, the WC powder is obtained.

[0016] Mix tungsten powder, carbon black with moisture-removed NaCl and KCl, and then grind for 20 - 40 min before calcination.

[0017] Remove NaCl and KCl from the powder in deionized water at 90 - 100 °C, and finally dry at 90 - 100 °C for 6 - 12 h to obtain the WC powder.

[0018] In step 2, disperse 0.34 - 0.72 g of WC powder in 60 - 90 ml of isopropanol, and then add iodine.

[0019] After dispersing the WC powder in isopropanol, stir for 12 - 24 h, and then add iodine and mix evenly. The mass ratio of iodine to WC powder is (0.34 - 0.72):(0.34 - 0.72) to obtain a deposition solution.

[0020] The temperature of the deposition solution described in step 3 is 40 - 60 °C, and hydrothermal electrophoresis deposition is carried out at a voltage of 5 - 10 V for 1 - 2 h.

[0021] A bismuth tungstate / tungsten carbide-C / C composite photocathode material is obtained by the preparation method of the bismuth tungstate / tungsten carbide-C / C composite photocathode material described in any one of the above.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] A preparation method of a bismuth tungstate / tungsten carbide-C / C composite photo-cathode material. CTAB is used as an intercalating agent for the preparation of Bi2WO6 in an aqueous system. By adjusting the hydrothermal temperature, while Bi2WO6 is loaded on carbon fibers, the distance between the flake structures is significantly increased, and the flower-like structure of Bi2WO6 is not damaged. While retaining the flower-like morphology, the active reaction area is increased, which is more conducive to the subsequent combination of WC and Bi2WO6. The WC powder has good crystallinity and is a good electrical conductor. Its hexagonal crystal structure endows tungsten carbide with hardness similar to that of diamond and stable chemical properties. Then, by means of hydrothermal electrophoresis deposition, with the assistance of iodine, WC particles continue to grow on carbon fibers. By adjusting the current density, when it combines with Bi2WO6, it is relatively dispersed on the C / C composite material. The binding force between the electrode powder of Bi2WO6-C / C and the substrate carbon / carbon composite material is good, the combination is relatively tight, and the powder distribution is relatively uniform. When bismuth tungstate and tungsten carbide are combined, the formed heterojunction interface has important applications on the photo-electrocatalytic photo-cathode. The good conductivity of tungsten carbide helps to accelerate electron transport, while the light absorption performance of bismuth tungstate can effectively utilize light energy to generate photo-generated carriers. The difference in the energy band structures of bismuth tungstate and tungsten carbide at the heterojunction interface can promote the separation of photo-generated electron-hole pairs and reduce their recombination probability, thus significantly improving the photo-electrocatalytic efficiency. In photo-electrocatalytic reactions such as water splitting for hydrogen production, reduction of CO2, and synthesis of ammonia, the photo-cathode with this composite structure exhibits better performance than single materials, providing new material choices and directions for solving energy and environmental problems. The preparation method of the WC / Bi2WO6-C / C photo-cathode material of the present invention by electrophoresis deposition is simple, highly operable, and exhibits strong photo-electrocatalytic hydrogen evolution performance in an alkaline electrolyte. Using the recyclable carbon / carbon composite as the substrate conforms to the principle of environmental friendliness. Description of the Drawings

[0024] Figure 1 XRD pattern of Bi2WO6-C / C prepared under the conditions of Example 1 of the present invention.

[0025] Figure 2 XRD pattern of the WC / Bi2WO6 powder-C / C composite photo-cathode material prepared under the conditions of Example 1 of the present invention.

[0026] Figure 3 SEM image of the Bi2WO6 powder prepared without adding CTAB under the conditions of Example 1 of the present invention.

[0027] Figure 4 SEM image of the Bi2WO6 powder prepared under the conditions of Example 1 of the present invention.

[0028] Figure 5SEM image of the WC / Bi2WO6 powder-C / C composite photocathode material prepared under the conditions of Example 1 of the present invention.

[0029] Figure 6 Current density-voltage curve of the WC / Bi2WO6-C / C photocathode material prepared under the conditions of Example 1 of the present invention. Detailed implementation manners

[0030] The following further describes the present invention in detail with specific examples, which are explanations rather than limitations of the present invention.

[0031] A preparation method of a WC / Bi2WO6-C / C composite photocathode material by electrophoretic deposition according to the present invention includes the following steps:

[0032] Step 1: Weigh 0.1 - 0.5 mol of Bi2O3 as powder 1, weigh 0.2 - 0.6 mol of Na2WO4·2H2O as powder 2, and weigh 0.01 - 0.03 mol of CTAB (cetyltrimethylammonium bromide) as an intercalating agent as powder 3;

[0033] Step 2: Disperse powder 1 in 50 - 70 ml of deionized water, then add powder 2 and powder 3 in sequence for dissolution, then ultrasonicate for 30 min - 1 h at room temperature, transfer it into a high-pressure autoclave with a Teflon lining, then immerse the carbon / carbon (C / C) composite material in it, react at 140 - 180 °C for 20 - 24 h, after the reaction ends, take out the electrode, wash it 3 - 5 times with deionized water and ethanol in sequence to obtain a Bi2WO6-C / C electrode precursor, which is electrode 1.

[0034] Step 3: Weigh NaCl and KCl with a molar ratio of 1:1, heat them at 200 - 300 °C for 24 - 36 h to remove moisture and obtain powder 4;

[0035] Step 4: Weigh 0.01 - 0.05 mol of tungsten (W) powder and 0.2 - 1 mol of carbon black and mix them with powder 4, and grind the mixture for 20 - 40 min to obtain powder 5;

[0036] Step 5: Transfer powder 5 to a porcelain boat and calcine it at 800 - 1000 °C for 1 - 3 h. NaCl and KCl can remove the moisture generated during the calcination process and prevent the formation of by-products, and powder 6 is prepared by the molten salt method;

[0037] Step 6: After heating deionized water to 90 - 100 °C, wash powder 6 to remove NaCl and KCl, put the washed powder into an oven and dry it at 90 - 100 °C for 6 - 12 h to obtain WC powder, which is powder 7;

[0038] Step 7, weigh 0.34 - 0.72 g of the prepared powder 7 and disperse it in 60 - 90 ml of isopropanol. After stirring for 12 - 24 h, add 0.34 - 0.72 g of iodine (I), and then continue to stir for 12 - 24 h to obtain Solution 1;

[0039] Step 8, pour Solution 1 into the hydrothermal electrophoresis deposition reactor. Use the graphite electrode as the positive electrode and Electrode 1 as the negative electrode. Keep the positive and negative electrodes parallel. Test with an ohmmeter to ensure the electrodes are conducting. Insert the electrodes into the reactor. After assembling the hydrothermal electrophoresis deposition equipment, connect the external electrode wires;

[0040] Step 9, set the voltage to 5 - 10 V and the current density to 1 - 3 A / m 2 , react at 40 - 60 °C for 1 - 2 h. After the equipment cools naturally, take out the electrodes and let them dry in the air to obtain the WC / Bi2WO6-C / C photocathode material.

[0041] Example 1:

[0042] A preparation method for preparing WC / Bi2WO6-C / C composite photocathode material by electrophoresis deposition includes the following steps:

[0043] Step 1, weigh 0.1 mol of Bi2O3 as Powder 1, weigh 0.2 mol of Na2WO4·2H2O as Powder 2, and weigh 0.01 mol of CTAB as an intercalating agent as Powder 3;

[0044] Step 2, disperse Powder 1 in 50 ml of deionized water, then add Powder 2 and Powder 3 in sequence for dissolution. Then, ultrasonicate for 30 min at room temperature and transfer it to a Teflon-lined autoclave. Put the carbon / carbon (C / C) composite material into the autoclave and react at 160 °C for 24 h. After the reaction ends, take out the electrodes and wash them 3 times with deionized water and ethanol in sequence to obtain the Bi2WO6-C / C electrode precursor, which is Electrode 1.

[0045] Step 3, weigh NaCl and KCl with a molar ratio of 1:1, heat them at 300 °C for 24 h to remove moisture and obtain Powder 4;

[0046] Step 4, weigh 0.01 mol of W powder and 0.2 mol of carbon black and mix them with Powder 4. After mixing, grind for 30 min to obtain Powder 5;

[0047] Step 5, transfer Powder 5 to a porcelain boat and calcine it at 950 °C for 2 h to obtain Powder 6;

[0048] Step 6, heat deionized water to 95 °C and wash Powder 6 to remove NaCl and KCl. Put the washed powder into an oven and dry it at 95 °C for 12 h to obtain WC powder, which is Powder 7;

[0049] Step 7, weigh 0.34 g of the prepared powder 7 and disperse it in 60 ml of isopropanol. After stirring for 24 h, add 0.34 g of iodine (I), and then continue stirring for 24 h to obtain Solution 1;

[0050] Step 8, pour Solution 1 into the hydrothermal electrophoretic deposition reactor. Use the graphite electrode as the positive electrode and Electrode 1 as the negative electrode. Keep the positive and negative electrodes parallel. Test with an ohmmeter to ensure electrode conduction. Insert the electrodes into the reactor. After assembling the hydrothermal electrophoretic deposition equipment, connect the external electrode wires;

[0051] Step 9, set the voltage to 5 V and the current density to 1 A / m 2 , react at 40 °C for 2 h. After the equipment cools naturally, take out the electrodes and let them dry in the air to obtain the WC / Bi2WO6-C / C photocathode material.

[0052] From Figure 1 the shown XRD pattern, it can be clearly seen that there are peaks of Bi2WO6 on the prepared Electrode Material 1, which can prove that the hydrothermal method can prepare Bi2WO6 powder on the C / C substrate.

[0053] Figure 2 is the XRD pattern of the WC / Bi2WO6 composite powder prepared by the present invention. It can be seen from the pattern that the WC and Bi2WO6 powders are successfully compounded.

[0054] Figure 3 is the SEM image of bismuth tungstate powder without adding CTAB. It can be observed that the powder has the typical "flower-like" morphology of bismuth tungstate, with sheet-like stacking, but there is almost no spacing between the sheet-like structures, which is not conducive to the attachment of active sites.

[0055] Figure 4 is the SEM image of bismuth tungstate powder after adding CTAB. Obviously, the distance between the sheet-like structures increases significantly. While the spacing increases, the "flower-like" structure is not damaged, increasing the active reaction area while retaining the morphology.

[0056] Through Figure 5 the SEM images, it can be seen that particles are obviously loaded on the carbon fibers. The particles have different morphological characteristics, and their morphology has the morphology of bismuth tungstate powder and carbide powder, and the particle dispersion is good, without obvious stacking phenomenon.

[0057] Figure 6 is the J-V curve of the WC / Bi2WO6-C / C composite material prepared by the present invention tested in a 0.5 M sodium hydroxide electrolyte, showing its photocatalytic hydrogen evolution performance. It can be seen that at -10 mA / cm -2Under such circumstances, the over-potential of the WC / Bi2WO6-C / C composite material is 753 mV. The WC / Bi2WO6-C / C photocathode material exhibits strong photocatalytic hydrogen evolution performance, indicating that tungsten carbide can be used as a co-catalyst for photocatalytic hydrogen evolution, and the WC / Bi2WO6-C / C photocathode material can be used as a photocatalytic material, promoting the further development of photocatalytic photocathode materials.

[0058] Example 2

[0059] A preparation method for preparing WC / Bi2WO6-C / C composite photocathode material by electrophoretic deposition includes the following steps:

[0060] Step 1: Weigh 0.2 mol of Bi2O3 as powder 1, weigh 0.2 mol of Na2WO4·2H2O as powder 2, and weigh 0.02 mol of CTAB as an intercalating agent as powder 3.

[0061] Step 2: Disperse powder 1 in 50 ml of deionized water, then add powder 2 and powder 3 in sequence for dissolution. After ultrasonic treatment at room temperature for 30 min, transfer it to a Teflon-lined autoclave. Place the carbon / carbon (C / C) composite material in the autoclave and react at 180 °C for 24 h. After the reaction is completed, take out the electrode and wash it 3 times with deionized water and ethanol in sequence to obtain the Bi2WO6-C / C electrode precursor, which is electrode 1.

[0062] Step 3: Weigh NaCl and KCl with a molar ratio of 1:1, heat them at 300 °C for 36 h to remove moisture, and obtain powder 4.

[0063] Step 4: Weigh 0.01 mol of W powder and 0.2 mol of carbon black and mix them with powder 4. After mixing, grind for 40 min to obtain powder 5.

[0064] Step 5: Transfer powder 5 to a porcelain boat and calcine it at 1000 °C for 2 h to obtain powder 6.

[0065] Step 6: Heat deionized water to 95 °C, wash powder 6 to remove NaCl and KCl. After washing, place the powder in an oven and dry it at 95 °C for 12 h to obtain WC powder, which is powder 7.

[0066] Step 7: Weigh 0.34 g of the prepared powder 7 and disperse it in 60 ml of isopropanol. After stirring for 24 h, add 0.34 g of iodine (I), and continue to stir for 24 h to obtain solution 1.

[0067] Step 8: Pour Solution 1 into the hydrothermal electrophoresis deposition reactor. Use the graphite electrode as the positive electrode and Electrode 1 as the negative electrode. Keep the positive and negative electrodes parallel. Test with an ohmmeter to ensure electrode conduction. Insert the electrodes into the reactor. After assembling the hydrothermal electrophoresis deposition equipment, connect the external electrode wires.

[0068] Step 9: Set the voltage to 5 V and the current density to 1 A / m 2 , react at 60 °C for 2 h. After the equipment cools naturally, take out the electrodes and let them dry in the air to obtain the WC / Bi2WO6-C / C photocathode material.

[0069] Example 3:

[0070] A preparation method for preparing WC / Bi2WO6-C / C composite photocathode material by electrophoresis deposition, comprising the following steps:

[0071] Step 1: Weigh 0.1 mol of Bi2O3 as Powder 1, weigh 0.6 mol of Na2WO4·2H2O as Powder 2, and weigh 0.03 mol of CTAB as an intercalating agent as Powder 3;

[0072] Step 2: Disperse Powder 1 in 50 ml of deionized water, then add Powder 2 and Powder 3 in sequence for dissolution. Then, ultrasonicate for 30 min at room temperature and transfer it to a high-pressure autoclave with a Teflon lining. Put the carbon / carbon (C / C) composite material into the high-pressure autoclave and react at 140 °C for 20 h. After the reaction ends, take out the electrodes and wash them 3 times with deionized water and ethanol in sequence to obtain the Bi2WO6-C / C electrode precursor, which is Electrode 1.

[0073] Step 3: Weigh NaCl and KCl with a molar ratio of 1:1 and heat them at 300 °C for 24 h to remove moisture to obtain Powder 4;

[0074] Step 4: Weigh 0.05 mol of W powder and 0.2 mol of carbon black and mix them with Powder 1. After mixing, grind for 30 min to obtain Powder 5;

[0075] Step 5: Transfer Powder 2 to a porcelain boat and calcine it at 950 °C for 1 h to obtain Powder 6;

[0076] Step 6: Heat deionized water to 95 °C and wash Powder 6 to remove NaCl and KCl. Put the washed powder into an oven and dry it at 95 °C for 12 h to obtain WC powder, which is Powder 7;

[0077] Step 7: Weigh 0.34 g of the prepared Powder 7 and disperse it in 60 ml of isopropanol. Stir for 24 h, then add 0.34 g of iodine (I), and continue to stir for 24 h to obtain Solution 1;

[0078] Step 8: Pour Solution 1 into the hydrothermal electrophoresis deposition reactor. Use the graphite electrode as the positive electrode and Electrode 1 as the negative electrode. Keep the positive and negative electrodes parallel, and use an ohmmeter to test to ensure electrode conduction. Insert the electrodes into the reactor. After assembling the hydrothermal electrophoresis deposition equipment, connect the external electrode wires.

[0079] Step 9: Set the voltage to 5 V and the current density to 2 A / m 2 , react at 40 °C for 1 h. After the equipment cools naturally, take out the electrodes, let them dry in the air, and obtain the WC / Bi2WO6-C / C photocathode material.

[0080] Example 4:

[0081] A preparation method for preparing WC / Bi2WO6-C / C composite photocathode materials by electrophoresis deposition, including the following steps:

[0082] Step 1: Weigh 0.5 mol of Bi2O3 as Powder 1, weigh 0.2 mol of Na2WO4·2H2O as Powder 2, and weigh 0.03 mol of CTAB as an intercalating agent as Powder 3.

[0083] Step 2: Disperse Powder 1 in 50 ml of deionized water, then add Powder 2 and Powder 3 in sequence for dissolution. Then, ultrasonicate for 30 min at room temperature and transfer it to a high-pressure autoclave with a Teflon liner. Put the carbon / carbon (C / C) composite material into the high-pressure autoclave and react at 160 °C for 24 h. After the reaction is completed, take out the electrodes and wash them 3 times with deionized water and ethanol in sequence to obtain the Bi2WO6-C / C electrode precursor, which is Electrode 1.

[0084] Step 3: Weigh NaCl and KCl with a molar ratio of 1:1, heat them at 300 °C for 24 h to remove moisture, and obtain Powder 4.

[0085] Step 4: Weigh 0.01 mol of W powder and 0.2 mol of carbon black and mix them with Powder 4. After mixing, grind for 30 min to obtain Powder 5.

[0086] Step 5: Transfer Powder 5 to a porcelain boat and calcine it at 950 °C for 2 h to obtain Powder 6.

[0087] Step 6: Heat deionized water to 95 °C and wash Powder 6 to remove NaCl and KCl. Put the washed powder into an oven and dry it at 95 °C for 12 h to obtain WC powder, which is Powder 7.

[0088] Step 7: Weigh 0.34 g of the prepared Powder 7 and disperse it in 60 ml of isopropanol. Stir for 24 h, then add 0.34 g of iodine (I), and continue to stir for 24 h to obtain Solution 1.

[0089] Step 8: Pour Solution 1 into the hydrothermal electrophoresis deposition reactor. Use the graphite electrode as the positive electrode and Electrode 1 as the negative electrode. Keep the positive and negative electrodes parallel. Test with an ohmmeter to ensure electrode conduction. Insert the electrodes into the reactor. After assembling the hydrothermal electrophoresis deposition equipment, connect the external electrode wires.

[0090] Step 9: Set the voltage to 5 V and the current density to 1 A / m 2 , react at 60 °C for 2 h. After the equipment cools naturally, take out the electrodes and let them dry in the air to obtain the WC / Bi2WO6-C / C photocathode material.

Claims

1. A preparation method of a bismuth tungstate / tungsten carbide-C / C composite photo-cathode material, characterized in that, It includes the following steps: Step 1: Immerse the carbon / carbon composite material in a mixed aqueous system in which Bi2O3 is dispersed, Na2WO4·2H2O is dissolved, and CTAB is added. Perform hydrothermal treatment at 140 - 180 °C, and then take out the obtained composite material and wash it to obtain a Bi2WO6-C / C composite photocathode precursor; Step 2: Disperse the WC powder, and then add iodine and mix evenly. The ratio of the WC powder to Bi2O3 in Step 1 is (0.34 - 0.72) g : (0.1 - 0.5) mol to obtain a deposition solution; Step 3: Using the Bi2WO6-C / C composite photocathode precursor as the negative electrode, perform hydrothermal electrophoresis deposition in the deposition solution at a current density of 1-3 A / m 2 , then take it out and dry it to obtain the bismuth tungstate / tungsten carbide-C / C composite photocathode material.

2. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photoemissive cathode material according to claim 1, wherein The mixed aqueous system described in Step 1 is obtained according to the following process: Disperse Bi2O3 in deionized water, and then add Na2WO4·2H2O and CTAB in sequence for dissolution. The molar ratio of Bi2O3, Na2WO4·2H2O, and CTAB is (0.1 - 0.5) : (0.2 - 0.6) : (0.01 - 0.03), and then ultrasonically treat it at room temperature for 30 min - 1 h to obtain the mixed aqueous system.

3. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photoemissive cathode material according to claim 1, characterized in that, In Step 1, after the carbon / carbon composite material is immersed in the mixed aqueous system, perform hydrothermal treatment at 140 - 180 °C for 20 - 24 h, and then take out the obtained composite material.

4. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photocathode material according to claim 1, wherein, The WC powder described in Step 2 is obtained according to the following process: Mix tungsten powder, carbon black, and dehydrated NaCl and KCl. The molar ratio of tungsten powder to carbon black is (0.01 - 0.05) : (0.2 - 1). Then calcine it at 800 - 1000 °C for 1 - 3 h to obtain a powder, and then remove NaCl and KCl in the powder and dry it to obtain the WC powder.

5. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photocathode material according to claim 4, characterized in that, Mix tungsten powder, carbon black, and dehydrated NaCl and KCl, grind them for 20 - 40 min, and then perform calcination.

6. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photoemissive cathode material according to claim 4, characterized in that Remove NaCl and KCl from the powder in deionized water at 90 - 100 °C, and finally dry it at 90 - 100 °C for 6 - 12 h to obtain the WC powder.

7. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photoemissive cathode material according to claim 1, characterized in that, In Step 2, disperse every 0.34 - 0.72 g of WC powder in 60 - 90 ml of isopropanol, and then add iodine.

8. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photocathode material according to claim 7, wherein, After dispersing the WC powder in isopropanol, stir it for 12 - 24 h, and then add iodine and mix evenly. The mass ratio of iodine to WC powder is (0.34 - 0.72) : (0.34 - 0.72) to obtain a deposition solution.

9. The preparation method of the bismuth tungstate / tungsten carbide-C / C composite photocathode material according to claim 1, characterized in that, The temperature of the deposition solution described in Step 3 is 40 - 60 °C, and hydrothermal electrophoresis deposition is carried out at a voltage of 5 - 10 V for 1 - 2 h.

10. A bismuth tungstate / tungsten carbide-C / C composite photocathode material, characterized in that, It is obtained by the preparation method of the bismuth tungstate / tungsten carbide-C / C composite photocathode material according to any one of claims 1 to 9.

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