Gradient coating bismuth tungstate / zirconium nitride (oxynitride)-carbon-carbon self-supporting electro-catalysis electrode material and preparation method and application of gradient coating bismuth tungstate / zirconium nitride (oxynitride)-carbon-carbon self-supporting electro-catalysis electrode material

Abstract

The invention discloses a gradient coating bismuth tungstate / zirconium nitride (oxynitride)-carbon-carbon self-supporting electro-catalysis electrode material and a preparation method and application thereof.The preparation method comprises the steps that bismuth tungstate powder and zirconium nitride (oxynitride) powder are prepared respectively, and the bismuth tungstate powder and the zirconium nitride (oxynitride) powder are prepared into deposition solutions respectively; fixing the cleaned C / C substrate on a negative electrode of microwave electrophoretic deposition equipment, then placing the C / C substrate in a bismuth tungstate deposition solution for microwave electrophoretic deposition for 10-30 minutes, then placing the C / C substrate in a zirconium nitride (oxynitride) deposition solution for microwave electrophoretic deposition for 10-30 minutes, and then drying the C / C substrate to obtain the gradient coating bismuth tungstate / zirconium nitride (oxynitride)-carbon-carbon self-supporting electro-catalysis electrode material. According to the material, the separation efficiency of photon-generated carriers is improved, so that recombination of the photon-generated carriers is reduced, and the photoelectrocatalysis performance of bismuth tungstate is improved; the microwave electrophoretic deposition technology is adopted, and the technology can achieve rapid deposition, is good in uniformity, easy and convenient to operate, capable of being accurately controlled and high in reproducibility.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional materials, relates to photocatalytic materials, and particularly relates to the preparation and photocatalytic application of a gradient-coated bismuth tungstate / nitrogen (oxygen) zirconium-carbon / carbon self-supporting electrocatalytic electrode material. Background Art

[0002] As a rich and clean energy source, the efficient utilization of solar energy is crucial for alleviating the fossil energy crisis and environmental problems. Since the Fujishima Akira team discovered the TiO2 photocatalytic water splitting effect in 1972, photoelectrochemical water splitting for hydrogen production technology has received attention due to its potential in converting solar energy into clean hydrogen energy and has become an effective way to address energy and environmental challenges. Selecting a suitable photocatalytic material is the key to achieving a breakthrough in this technology.

[0003] Regarding the currently reported photocatalytic materials, noble metal oxides with high activity are expensive, and non-noble metal photocatalytic materials generally have problems such as a narrow light response range and a fast recombination rate of photo-generated electron-hole pairs, severely restricting the wide application of photocatalytic water splitting technology. In recent years, bismuth-based metal oxides have great potential in the field of photocatalytic water splitting due to their narrow bandgap, high stability, low cost, simple synthesis process, and non-toxicity. Bismuth tungstate (Bi2WO6) is a typical perovskite-type composite oxide with a bandgap of about 2.7 eV, capable of absorbing light with a wavelength less than 460 nm. It also has an Aurivillius-type oxide layered structure, which is beneficial for the effective separation of photo-generated electron-hole pairs. In addition, the appropriate band edge of bismuth tungstate enables it to be applied to photocatalytic water splitting. However, bismuth tungstate has problems such as a small absorption part of the solar spectrum, poor charge transport, and still a relatively high recombination of photo-generated electron-hole pairs. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a gradient-coated bismuth tungstate / nitrogen (oxygen) zirconium-carbon / carbon self-supporting electrocatalytic electrode material with excellent photocatalytic performance, as well as its preparation method and application.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A preparation method of a gradient-coated bismuth tungstate / nitrogen (oxygen) zirconium-carbon / carbon self-supporting electrocatalytic electrode material, comprising the following steps:

[0007] Step 1: Add 0.6 - 1.0 g of bismuth nitrate to 30 - 45 mL of water, and add 5 - 25 mg of CTAB and stir evenly to prepare solution A;

[0008] Add 0.15 - 0.30 g of ammonium tungstate into 15 - 30 mL of water, and add 0.8 - 1.3 g of citric acid, then stir evenly to prepare solution B;

[0009] When heating solution B to 50 - 90 °C, immediately drop solution A into it at a rate of 1 - 5 drops / s, and stir until it is uniform to obtain solution C;

[0010] Step 2: Transfer solution C into a reaction kettle, and carry out hydrothermal reaction at 140 - 190 °C in an oven for 10 - 16 h. After cooling to room temperature, wash, dry, grind it, then place it in a muffle furnace and calcine it at 300 - 500 °C for 3 - 5 h. After cooling to room temperature, bismuth tungstate powder is obtained;

[0011] Step 3: Weigh zirconium chloride and urea according to a mass ratio of 1:(2 - 4), fully grind and mix them evenly, then put them into an alumina boat, and heat them at 900 - 1200 °C in an Ar atmosphere for 3 - 6 h using a tube furnace. After cooling to room temperature, zirconium nitride (oxide) powder is obtained;

[0012] Step 4: Weigh 0.4 - 0.5 g of bismuth tungstate powder and zirconium nitride (oxide) powder respectively and place them in two beakers. Then add 170 - 220 ml of acetone solution to each, stir until they are evenly dispersed, and then add 0.4 - 0.5 g of iodine to each. Continue to stir until they are uniform to obtain deposition solution G and deposition solution H;

[0013] Step 5: Fix the cleaned C / C substrate on the negative electrode of the microwave electrophoresis deposition equipment, then place it in solution H for microwave electrophoresis deposition for 10 - 30 min. After completion, place it in solution G for microwave electrophoresis deposition for 10 - 30 min, and then dry it to obtain the gradient coating bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material.

[0014] The present invention also has the following technical features:

[0015] Preferably, the stirring described in Step 1 and Step 4 is magnetic stirring at a speed of 400 - 800 rmp for 2 - 4 h.

[0016] Preferably, the washing described in Step 2 is filtration washing with deionized water and absolute ethanol for 2 - 5 times.

[0017] Preferably, the heating rate of the tube furnace in Step 3 is 5 - 10 °C / min.

[0018] Preferably, the cleaning method of the C / C substrate described in Step 5 is to carry out ultrasonic treatment with isopropanol, water and absolute ethanol in sequence for 1 h, and then dry it at 60 - 90 °C for 1 - 3 h.

[0019] Preferably, during the electrophoresis deposition process described in Step 5, a voltage of 10 - 20 V and a current of 1 - 3 A are applied.

[0020] The present invention also protects a gradient coating bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared by the method as described above and its application as a photoanode in the process of photoelectrocatalysis.

[0021] Compared with the prior art, the present invention has the following technical effects:

[0022] In the present invention, a bismuth tungstate / zirconium nitride (oxide)-carbon / carbon gradient coating structure is synthesized on a C / C substrate by microwave electrophoresis deposition technology. The C / C substrate has the advantages of light weight, high specific surface area, strong conductivity and strong bonding. The heterostructure of bismuth tungstate / zirconium nitride (oxide) effectively enhances the heterointerfacial interaction. Zirconium nitride, as an electron transport layer, transports the photogenerated electrons generated by the light absorption of bismuth tungstate to the C / C substrate and then to the photocathode, which effectively improves the separation efficiency of photogenerated carriers, thereby reducing the recombination of photogenerated carriers and further improving the photoelectrocatalytic performance of bismuth tungstate.

[0023] The present invention adopts microwave electrophoresis deposition technology, which can deposit quickly, has good uniformity, is easy to operate, can be precisely controlled and has high reproducibility. Description of the Drawings

[0024] Figure 1 X-ray diffraction analysis diagram of the bismuth tungstate / zirconium nitride (oxide) mixed powder prepared in Example 1;

[0025] Figure 2 Scanning diagram of the gradient coating bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared in Example 1;

[0026] Figure 3 LSV diagram of the gradient coating bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode materials prepared in Examples 1-3 in a solution with pH = 9.5 under simulated sunlight;

[0027] Figure 4 Impedance fitting curve of the gradient coating bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared in Example 1 in a solution with pH = 9.5 under simulated sunlight;

[0028] Figure 5 Applied bias photo-electrochemical conversion efficiency (ABPE) of the photo-electrode of the gradient coating bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared in Example 1 in a solution with pH = 9.5 under simulated sunlight. Detailed Embodiments

[0029] The following further elaborates on the specific content of the present invention in detail in conjunction with embodiments.

[0030] Example 1

[0031] This embodiment provides a preparation method of a gradient coating bismuth tungstate / nitrogen (oxygen) zirconium carbide-carbon self-supporting electrocatalytic electrode material, comprising the following steps:

[0032] Step 1: Add 0.6 g of bismuth nitrate to 30 mL of water, and add 5 mg of CTAB, and magnetically stir at a speed of 400 rmp for 4 h until evenly mixed to prepare solution A;

[0033] Add 0.15 g of ammonium tungstate to 15 mL of water, and add 0.8 g of citric acid, and magnetically stir at a speed of 400 rmp for 4 h until evenly mixed to prepare solution B;

[0034] When solution B is heated to 50 °C, immediately drop solution A into it at a rate of 2 drops / s, and stir until evenly mixed to obtain solution C;

[0035] Step 2: Transfer solution C to a reaction kettle, carry out hydrothermal reaction at 140 °C in an oven for 16 h, cool to room temperature, filter and wash 3 times with deionized water and absolute ethanol, then dry, grind, and place in a muffle furnace to calcine at 300 °C for 5 h. After cooling to room temperature, bismuth tungstate powder is obtained;

[0036] Step 3: Weigh zirconium chloride and urea according to a mass ratio of 1:2, fully grind and mix them evenly, then put them into an alumina porcelain boat, heat in a tubular furnace at 900 °C for 6 h under an Ar atmosphere, with a heating rate of 5 °C / min. After cooling to room temperature, nitrogen (oxygen) zirconium carbide powder is obtained;

[0037] Step 4: Weigh 0.4 g of bismuth tungstate powder and nitrogen (oxygen) zirconium carbide powder respectively and place them in two beakers, then add 170 ml of acetone solution to each, stir until evenly dispersed, then add 0.4 g of iodine to each, and continue to stir until evenly mixed to obtain deposition solution G and deposition solution H;

[0038] Step 5: Ultrasonically clean the C / C substrate with isopropanol, water, and absolute ethanol for 1 h in sequence, then dry it at 60 °C for 3 h, fix it on the negative electrode of a microwave electrophoresis deposition device, then place it in solution H for microwave electrophoresis deposition, apply a voltage of 10 V and a current of 1 A for 30 min. After completion, place it in solution G and apply a voltage of 10 V and a current of 1 A for microwave electrophoresis deposition for 30 min, and then dry to obtain the gradient coating bismuth tungstate / nitrogen (oxygen) zirconium carbide-carbon self-supporting electrocatalytic electrode material.

[0039] Figure 1X-ray diffraction analysis pattern of the bismuth tungstate / zirconium nitride (oxide) mixed powder prepared in Example 1. It can be seen from the figure that the main phases of the prepared mixed powder are Bi2WO6, ZrN and Zr7O8N4. The characteristic peaks at 28.12°, 47.04° and 56.62° correspond to the (131), (202) and (133) crystal planes of Bi2WO6 (PDF#39-0256) respectively; the characteristic peaks at 33.72°, 39.16° and 56.68° correspond to the (111), (200) and (220) crystal planes of ZrN (PDF#35-0753) respectively; the characteristic peaks at 30.16°, 35.04° and 50.42° correspond to the (211), (122) and (214) crystal planes of Zr7O8N4 (PDF#50-1172) respectively. This indicates that the phases of bismuth tungstate and zirconium nitride (oxide) are successfully compounded.

[0040] Figure 2 Scanning image of the gradient-coated bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared in Example 1. It can be seen from the figure that a large amount of bismuth tungstate / zirconium nitride (oxide) heterostructures are loaded on the surface of carbon fibers.

[0041] Figure 3 LSV diagram of the gradient-coated bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode materials prepared in Examples 1-3 in a solution with pH = 9.5 under simulated sunlight. It can be seen that the synthesized self-supporting electrodes all have a large photocurrent density at 1.23 V vs. RHE, indicating that this system has excellent photoelectrocatalytic water splitting performance;

[0042] Figure 4 Impedance fitting curve of the gradient-coated bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared in Example 1 in a solution with pH = 9.5 under simulated sunlight, indicating good conductivity of this system;

[0043] Figure 5 ABPE diagram of the photo-electrode of the gradient-coated bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material prepared in Example 1 in a solution with pH = 9.5 under simulated sunlight, indicating good photoelectric conversion efficiency of this system.

[0044] Example 2

[0045] This example provides a preparation method of a gradient-coated bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material, including the following steps:

[0046] Step 1: Add 0.6 g of bismuth nitrate to 30 mL of water, add 5 mg of CTAB, and magnetically stir at a speed of 400 - 800 rmp for 2 h until evenly mixed to prepare solution A;

[0047] Add 0.15 g of ammonium tungstate to 15 mL of water, add 0.8 g of citric acid, and magnetically stir at a speed of 400 rmp for 2 h until evenly mixed to prepare solution B;

[0048] When solution B is heated to 50 °C, immediately drop solution A into it at a rate of 1 drop / s, and stir until evenly mixed to obtain solution C;

[0049] Step 2: Transfer solution C to a reaction kettle, carry out hydrothermal reaction at 140 °C in an oven for 10 h. After cooling to room temperature, filter and wash it 3 times with deionized water and absolute ethanol, then dry, grind, and place it in a muffle furnace to calcine at 300 °C for 3 h. After cooling to room temperature, bismuth tungstate powder is obtained;

[0050] Step 3: Weigh zirconium chloride and urea according to a mass ratio of 1:3, fully grind and mix them evenly, then put them into an alumina boat, heat them in a tubular furnace at 900 °C for 3 h under Ar atmosphere, with a heating rate of 6 °C / min. After cooling to room temperature, zirconium nitride (oxide) powder is obtained;

[0051] Step 4: Weigh 0.4 g of bismuth tungstate powder and zirconium nitride (oxide) powder respectively and place them in two beakers. Then add 170 ml of acetone solution to each, stir until evenly dispersed, and then add 0.4 g of iodine to each. Continue to stir until evenly mixed to obtain deposition solution G and deposition solution H;

[0052] Step 5: Ultrasonically clean the C / C substrate with isopropanol, water, and absolute ethanol for 1 h in sequence, then dry it at 60 °C for 1 h and fix it at the negative electrode of the microwave electrophoresis deposition equipment. Subsequently, place it in solution H, apply a voltage of 10 V and a current of 1 A, and carry out microwave electrophoresis deposition for 10 min. After completion, place it in solution G, apply a voltage of 10 V and a current of 1 A, and carry out microwave electrophoresis deposition for 10 min. Then dry it to obtain a gradient coating of bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material.

[0053] Example 3

[0054] This example provides a preparation method of a gradient coating of bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material, including the following steps:

[0055] Step 1: Add 0.8 g of bismuth nitrate to 40 mL of water, add 20 mg of CTAB, and magnetically stir at a speed of 600 rmp for 3 h until evenly mixed to prepare solution A;

[0056] Add 0.20 g of ammonium tungstate to 20 mL of water, and add 0.1 g of citric acid. Stir magnetically at a speed of 600 rmp for 3 h until evenly mixed to prepare solution B;

[0057] When the solution B is heated to 70 °C, immediately drop the solution A at a rate of 3 drops / s, and stir until evenly mixed to obtain solution C;

[0058] Step 2: Transfer the solution C to a reaction kettle, carry out hydrothermal reaction at 160 °C in an oven for 14 h. After cooling to room temperature, filter and wash 3 times with deionized water and absolute ethanol, then dry, grind, and place in a muffle furnace to calcine at 400 °C for 4 h. After cooling to room temperature, bismuth tungstate powder is obtained;

[0059] Step 3: Weigh zirconium chloride and urea according to a mass ratio of 1:4, fully grind and mix them evenly, then put them into an alumina boat. Use a tubular furnace to heat at 1000 °C for 4 h in an Ar atmosphere, and the heating rate is 7 °C / min. After cooling to room temperature, zirconium nitride (oxide) powder is obtained;

[0060] Step 4: Weigh 0.45 g of bismuth tungstate powder and zirconium nitride (oxide) powder respectively and place them in two beakers. Then add 200 ml of acetone solution to each, stir until evenly dispersed, and then add 0.45 g of iodine to each. Continue to stir until evenly mixed to obtain deposition solution G and deposition solution H;

[0061] Step 5: Ultrasonic clean the C / C substrate with isopropanol, water, and absolute ethanol for 1 h in sequence, then dry it at 70 °C for 2 h, and fix it on the negative electrode of the microwave electrophoresis deposition equipment. Then place it in solution H, apply a voltage of 15 V and a current of 2 A, and carry out microwave electrophoresis deposition for 20 min. After completion, place it in solution G, apply a voltage of 15 V and a current of 2 A, and carry out microwave electrophoresis deposition for 20 min. Then dry it to obtain a gradient coating of bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material.

[0062] Example 4

[0063] This example provides a preparation method of a gradient coating of bismuth tungstate / zirconium nitride (oxide)-carbon / carbon self-supporting electrocatalytic electrode material, including the following steps:

[0064] Step 1: Add 1.0 g of bismuth nitrate to 45 mL of water, and add 25 mg of CTAB. Stir magnetically at a speed of 800 rmp for 4 h until evenly mixed to prepare solution A;

[0065] Add 0.30 g of ammonium tungstate to 30 mL of water, and add 1.3 g of citric acid. Stir magnetically at a speed of 800 rmp for 4 h until evenly mixed to prepare solution B;

[0066] When the solution B is heated to 90 °C, immediately drop the solution A at a rate of 5 drops / s, and stir until evenly mixed to obtain solution C;

[0067] Step 2: Transfer solution C into a reaction kettle, carry out hydrothermal reaction at 190 °C for 16 h in an oven. After cooling to room temperature, filter and wash with deionized water and absolute ethanol three times, then dry, grind, place in a muffle furnace, and calcine at 500 °C for 5 h. After cooling to room temperature, bismuth tungstate powder is obtained.

[0068] Step 3: Weigh zirconium chloride and urea according to a mass ratio of 1:4, fully grind and mix them evenly, then put them into an alumina boat. Use a tube furnace to heat at 1200 °C for 6 h under an Ar atmosphere, with a heating rate of 5 °C / min. After cooling to room temperature, zirconium oxynitride powder is obtained.

[0069] Step 4: Weigh 0.5 g of bismuth tungstate powder and zirconium oxynitride powder respectively and place them in two beakers. Then add 220 ml of acetone solution to each, stir until evenly dispersed, and then add 0.5 g of iodine to each. Continue to stir until evenly mixed to obtain deposition solution G and deposition solution H.

[0070] Step 5: Ultrasonically clean the C / C substrate with isopropanol, water, and absolute ethanol for 1 h in sequence, then dry at 90 °C for 3 h and fix it at the negative electrode of a microwave electrophoresis deposition device. Subsequently, place it in solution H, apply a voltage of 20 V and a current of 3 A, and carry out microwave electrophoresis deposition for 30 min. After completion, place it in solution G, apply a voltage of 20 V and a current of 3 A, and carry out microwave electrophoresis deposition for 30 min. Then dry to obtain a gradient-coated bismuth tungstate / zirconium oxynitride-carbon / carbon self-supporting electrocatalytic electrode material.

[0071] Those of ordinary skill in the art will realize that the embodiments described herein are for helping readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations without departing from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A method for preparing a gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material, characterized in that: The following steps are involved: Step 1, add 0.6-1.0 g of bismuth nitrate into 30-45 mL of water, and add 5-25 mg of CTAB and stir evenly to prepare solution A; Add 0.15-0.30g of ammonium tungstate to 15-30mL of water, and add 0.8-1.3g of citric acid and stir evenly to prepare solution B; When solution B is heated to 50-90°C, solution A is immediately added dropwise at a rate of 1-5 drops / s and stirred until uniform to obtain solution C; Step 2: Transfer solution C to a reactor, perform hydrothermal reaction at 140-190° C. in an oven for 10-16 hours, cool to room temperature, wash, dry, grind, and place in a muffle furnace for calcination at 300-500° C. for 3-5 hours, and cool to room temperature to obtain bismuth tungstate powder; Step 3, weighing zirconium chloride and urea in a mass ratio of 1: (2-4), grinding and mixing them thoroughly, and then putting them into an alumina porcelain boat, using a tube furnace to heat at 900-1200° C. for 3-6 hours under Ar atmosphere, and cooling to room temperature to obtain zirconium nitride (oxy) powder; Step 4: Weigh 0.4-0.5 g of bismuth tungstate powder and zirconium nitride (oxy) powder respectively and place them in two beakers, then add 170-220 ml of acetone solution to each beaker, stir until evenly dispersed, then add 0.4-0.5 g of iodine to each beaker, continue stirring until evenly dispersed, and obtain deposition solution G and deposition solution H; Step 5: Fix the cleaned C / C substrate on the negative electrode of the microwave electrophoretic deposition equipment, and then place it in solution H for microwave electrophoretic deposition for 10 to 30 minutes. After completion, place it in solution G for microwave electrophoretic deposition for 10 to 30 minutes, and then dry it to obtain a gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material.

2. The method for preparing the gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material according to claim 1, characterized in that: The stirring described in step 1 and step 4 is magnetic stirring at a speed of 400 to 800 rpm for 2 to 4 hours.

3. The method for preparing the gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material according to claim 1, characterized in that: The washing in step 2 is performed by filtering and washing with deionized water and anhydrous ethanol for 2 to 5 times.

4. The method for preparing the gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material according to claim 1, characterized in that: In step 3, the heating rate of the tubular furnace is 5-10°C / min.

5. The method for preparing the gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material according to claim 1, characterized in that: The cleaning method of the C / C substrate described in step 5 is to perform ultrasonic cleaning with isopropanol, water and anhydrous ethanol for 1 hour in sequence, and then dry at 60-90° C. for 1-3 hours.

6. The method for preparing the gradient coating bismuth tungstate / zirconium nitride (oxygen)-carbon-carbon self-supporting electrocatalytic electrode material according to claim 1, characterized in that: During the electrophoretic deposition process described in step five, a voltage of 10 to 20 V and a current of 1 to 3 A are applied.

7. A gradient coating bismuth tungstate / zirconium nitride (oxy)de-carbon-carbon self-supporting electrocatalytic electrode material prepared by the method as described in any one of claims 1 to 6.

8. A use of the gradient coated bismuth tungstate / zirconium nitride (oxy)de-carbon-carbon self-supporting electrocatalytic electrode material as described in claim 7 as a photoanode in a photoelectrocatalytic process.

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