Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material and preparation method and application thereof
By preparing Z-type heterojunction Ta3N5/Bi2WO6-FTO photoelectrode materials, the problem of photogenerated carrier recombination in bismuth tungstate and Ta3N5 materials was solved, achieving efficient separation and migration of photogenerated electron-hole pairs, and improving the efficiency and stability of photoelectrochemical water splitting.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHAANXI UNIV OF SCI & TECH
- Filing Date
- 2025-12-29
- Publication Date
- 2026-04-14
AI Technical Summary
The existing photoanode material bismuth tungstate has a fast recombination rate of photogenerated carriers, resulting in low photoelectrocatalytic efficiency. The intrinsic defects introduced during the preparation of Ta3N5 material affect its performance.
A Z-type heterojunction Ta3N5/Bi2WO6-FTO photoelectrode material was used. Bi2WO6 and Ta3N5 powders were prepared by hydrothermal reaction and tube furnace gas-solid reaction nitriding. Combined with an FTO conductive substrate, a tight heterojunction structure was formed, which promoted the separation and migration of photogenerated charges.
It improves the separation efficiency of photogenerated electron-hole pairs, expands the light absorption range, significantly improves photocurrent response and charge separation efficiency, and has good material stability, making it suitable for high-efficiency solar-driven water splitting.
Smart Images
Figure CN121853013A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of functional materials technology, and relates to photoelectrocatalytic materials, specifically to a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, its preparation method, and its application. Background Technology
[0002] Photoelectrocatalytic water splitting technology is a highly efficient and clean energy technology that uses light energy to split water into hydrogen and oxygen. Compared with traditional water electrolysis methods, photoelectrocatalytic water splitting, driven by solar energy, is not only environmentally friendly but also has higher energy conversion efficiency. In this process, the photoanode plays a crucial role. The photoanode's function is to absorb light energy, generate electron-hole pairs, and drive the oxygen evolution reaction (OER), splitting water molecules into oxygen and protons. An ideal photoanode material not only needs a suitable light absorption band gap, but also excellent catalytic activity and stable chemical properties. These characteristics ensure that the photoanode can operate stably in the electrolyte for extended periods, improving the efficiency of water splitting.
[0003] Bismuth tungstate (Bi₂WO₆), a semiconductor material with a narrow bandgap (2.7-2.8 eV), can effectively absorb light energy in the visible light range, making it an ideal candidate photoanode material for photoelectrocatalytic water splitting. Its suitable band position and layered structure give it strong light absorption capabilities during photoelectrocatalysis, enabling it to effectively utilize sunlight to drive the water splitting reaction. Compared to many other semiconductor materials, bismuth tungstate has a lower cost, making it more promising for large-scale applications. However, its photogenerated carrier recombination rate is relatively fast, meaning that photogenerated electrons and holes easily recombine within the material, leading to reduced photoelectrocatalytic efficiency. To overcome this deficiency, a common approach is to construct heterojunction structures. Combining bismuth tungstate with other materials can effectively promote the separation of photogenerated carriers and suppress their recombination, thereby improving photoelectrocatalytic efficiency.
[0004] Ta3N5, a typical n-type semiconductor, has a band gap of approximately 2.1 eV. Furthermore, its conduction and valence band positions simultaneously meet the reduction and oxidation potential requirements of water, making it a highly promising photoanode material for photoelectrochemical water splitting. Theoretical calculations indicate that its maximum saturation photocurrent density can reach 12.9 mA / cm². 2 The theoretical solar energy conversion efficiency (STH) is as high as 15.9%. However, this material is usually prepared by high-temperature ammoniation of Ta₂O₅ precursor, a process that inevitably introduces intrinsic defects into the crystal lattice. While these defects contribute to its n-type conductivity, they also become the main recombination centers for photogenerated charges, severely limiting its practical performance. Currently, research mainly focuses on optimizing its photocatalytic and photoelectrochemical performance through strategies such as preparing nanostructures to increase specific surface area, controlling material morphology, and constructing heterojunction composite systems. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, its preparation method, and its applications. The Ta3N5 / Bi2WO6 heterojunction possesses broad spectral response capability, efficient photogenerated charge separation and migration capability, and good structural stability. Combined with the photogenerated electrons provided by the FTO conductive substrate to be led out to the external circuit, it further suppresses carrier recombination, improves photoelectric conversion efficiency, and enables the photoelectrode material to exhibit excellent photoelectrocatalytic activity.
[0006] To achieve the above objectives, the present invention employs the following technical solution: A method for preparing a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material includes the following steps: Step 1: Prepare Bi2WO6 powder using a hydrothermal reaction method; Step 2: Prepare Ta3N5 powder using a tube furnace gas-solid reactive nitriding method; Step 3: Weigh 0.35-0.70 g of Bi2WO6 powder and 0.15-0.31 g of Ta3N5 powder into beakers, add 150-200 mL of isopropanol to the beakers, stir the powders and ultrasonically disperse them until uniform to obtain precursor solution F. Using a dip coating machine, vertically immerse the pretreated FTO substrate into precursor solution F, let it stand for a few seconds, and then pull it up at a constant speed of 1-3 mm / s to form a uniform wet film on the substrate surface. Step 4: Immediately transfer the glass slide loaded with the wet film to a preheated hot stage and heat-treat it at 60°C for 5-10 min in an air atmosphere; finally, place the prepared film in a tube furnace and anneal it at 400-500°C for 1-2 h under an argon protective gas atmosphere to finally obtain the Ta3N5 / Bi2WO6-FTO photoelectrode material.
[0007] The present invention also has the following technical features: Preferably, the method for preparing the Bi2WO6 powder includes: S1. Add 0.6-1.0 g of bismuth nitrate to 30-45 mL of water to prepare solution A; add 0.15-0.30 g of sodium tungstate to 15-30 mL of deionized water to prepare solution B; add solution A dropwise to solution B at a rate of 1-5 drops / s, adjust the pH to 4-6, stir until homogeneous, add 0.1-0.2 g of sodium citrate and continue stirring for 2 hours to obtain solution C; S2. Transfer solution C to a polytetrafluoroethylene liner and hydrothermally react at 120-140℃ for 8-14 h. After cooling to room temperature, wash, dry, grind, and place in a tube furnace for calcination at 200-400℃ for 1-4 h. After cooling to room temperature, obtain powder D, which is Bi2WO6 powder.
[0008] Furthermore, in step S1, 6% relative volume fraction of nitric acid is used to adjust the pH.
[0009] Preferably, the method for preparing the Ta3N5 powder includes: Weigh 2-3 g of melamine and place it in an alumina ceramic boat at the inlet of a tube furnace. Then weigh 0.2-0.4 g of tantalum oxide and place it in the alumina ceramic boat at the center of the tube furnace. Heat the furnace to 600-1200℃ under an Ar atmosphere and maintain the temperature for 3-8 h. After cooling to room temperature, powder E is obtained. Preferably, the pretreatment method for the FTO substrate includes ultrasonic cleaning with acetone, anhydrous ethanol and deionized water in sequence.
[0010] This invention also protects a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material prepared by the method described above and its application in electrocatalytic water splitting.
[0011] Compared with the prior art, the present invention has the following technical effects: This invention prepares a Ta3N5 / Bi2WO6 coating structure on a fluorine-doped tin oxide (FTO) glass substrate using a dip-coating method, forming a Z-shaped Ta3N5 / Bi2WO6 heterojunction. Due to the tight heterojunction structure formed between the two phases of Ta3N5 and Bi2WO6, and the matching of their band structures, a highly efficient carrier transport channel is established at the interface, enabling rapid separation of photogenerated charges. This effectively promotes the separation and migration of photogenerated electron-hole pairs, thereby significantly suppressing recombination. The separated carriers are directionally transported to the reaction interface, where holes are efficiently used for the water oxidation reaction. The Ta3N5 / Bi2WO6 heterojunction achieves complementary and extended light absorption ranges, covering a wider range from ultraviolet to visible light, significantly improving the solar energy capture efficiency. As a result, this composite material achieves a photocurrent response far exceeding that of a single component, superior charge separation efficiency, and more stable photoelectrochemical performance, providing a promising photoanode material for achieving efficient solar-driven water splitting. The Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material of this invention has good stability and corrosion resistance. Ta3N5 itself has relatively stable chemical properties, and Bi2WO6 is a layered perovskite material with strong structural stability. After being combined with Ta3N5, the interface is tightly bonded, which can effectively suppress the dissolution, aggregation or phase transition of single components during light exposure or reaction. The FTO substrate has strong chemical inertness and is not easily corroded in aqueous solution or electrolyte, while providing stable support for the composite semiconductor layer. This invention uses the dip-coating method to prepare thin films. This technology is simple to operate, the process is flexible and controllable, and it can be reused with a high utilization rate. Attached Figure Description
[0012] Figure 1 Z-type heterojunction Ta3N prepared in Example 1 5 / XRD pattern of Bi2WO6; Figure 2 The scan image shows the Z-type heterojunction Ta3N5 / Bi2WO6 prepared in Example 1; Figure 3 LSV diagram of Ta3N5 / Bi2WO6-FTO prepared for Example 1 in a solution at pH 9.5 under simulated sunlight. Detailed Implementation
[0013] The following detailed explanation of the specific content of the present invention is provided in conjunction with embodiments. These descriptions are intended to explain the present invention and not to limit it.
[0014] Example 1 This embodiment provides a method for preparing a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, including the following steps: Step 1: Add 0.6 g of bismuth nitrate to 30 mL of water and stir continuously for 30 min to prepare solution A; add 0.15 g of sodium tungstate to 15 mL of deionized water and stir for 30 min to prepare solution B; add solution A dropwise to solution B at a rate of 1 drop / s, add 6% relative volume fraction nitric acid to adjust the pH to 6, stir until uniform, add 0.1 g of sodium citrate and continue stirring for 2 h to obtain solution C; Solution C was transferred to a polytetrafluoroethylene liner and hydrothermally reacted at 120°C for 10 h. After cooling to room temperature, it was washed, dried, ground, and then calcined in a tube furnace at 200°C for 4 h. After cooling to room temperature, powder D was obtained. Step 2: Weigh 2 g of melamine and place it in an alumina ceramic boat at the inlet of a tube furnace. Then weigh 0.2 g of tantalum oxide and place it in the alumina ceramic boat at the center of the tube furnace. Heat the furnace to 600℃ under an Ar atmosphere and maintain the temperature for 3 h. After cooling to room temperature, powder E is obtained. Step 3: Weigh 0.35 g of powder D and 0.15 g of powder E into beakers respectively, add 150 mL of isopropanol to the beakers, stir for 1 h, and then sonicate for 30 min to obtain precursor solution F. Pre-treat the FTO conductive glass by ultrasonic cleaning with acetone, anhydrous ethanol and water in sequence. Using a dip coating machine, vertically immerse the FTO substrate into the precursor solution F, let it stand for a few seconds, and then pull it up at a constant speed of 1 mm / s to form a uniform wet film on the substrate surface. Step 4: Immediately transfer the glass slide loaded with the wet film to a preheated hot stage and heat-treat it at 60°C for 10 min in an air atmosphere. Then place it in a tube furnace and anneal it at 400°C for 2 h in an argon atmosphere as a protective gas to finally obtain the Ta3N5 / Bi2WO6-FTO photoelectrode material.
[0015] Figure 1 Ta3N prepared in Example 1 5 / XRD and X-ray diffraction (XRD) analysis of Bi2WO6 showed that the experimental sample matched the standard card, confirming that the crystal structure of the sample was complete and met expectations. Figure 2 The image shows a scan of Ta3N5 / Bi2WO6 prepared in Example 1. Bismuth tungstate appears as nanoflowers, exposing a large specific surface area, while Ta3N5 is attached to the surface of Bi2WO6 in a spherical shape. Figure 3 The LSV diagram of Ta3N5 / Bi2WO6-FTO prepared in Example 1 in a solution simulated under sunlight at pH 9.5 shows that its photocurrent density reaches 1.58 mA / cm² at 1.23 V. 2 .
[0016] Example 2 This embodiment provides a method for preparing a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, including the following steps: Step 1: Add 0.8 g of bismuth nitrate to 35 mL of water and stir continuously for 30 min to prepare solution A; add 0.20 g of sodium tungstate to 20 mL of deionized water and stir for 30 min to prepare solution B; add solution A dropwise to solution B at a rate of 3 drops / s, add 6% relative volume fraction nitric acid to adjust the pH to 5, stir until uniform, add 0.1 g of sodium citrate and continue stirring for 2 h to obtain solution C; Solution C was transferred to a polytetrafluoroethylene liner and hydrothermally reacted at 130°C for 14 h. After cooling to room temperature, it was washed, dried, ground, and then calcined in a tube furnace at 300°C for 2 h. After cooling to room temperature, powder D was obtained. Step 2: Weigh 2.5 g of melamine and place it in an alumina ceramic boat at the inlet of a tube furnace. Then weigh 0.2 g of tantalum oxide and place it in the alumina ceramic boat at the center of the tube furnace. Heat the furnace to 700℃ under an Ar atmosphere and maintain the temperature for 4 h. After cooling to room temperature, powder E is obtained. Step 3: Weigh 0.70 g of powder D and 0.31 g of powder E into beakers, add 200 mL of isopropanol to the beakers, stir for 2 h, and then sonicate for 30 min to obtain precursor solution F. Pre-treat the FTO conductive glass by ultrasonic cleaning with acetone, anhydrous ethanol and water in sequence. Using a dip coating machine, vertically immerse the FTO substrate into precursor solution F, let it stand for a few seconds, and then pull it up at a constant speed of 2 mm / s to form a uniform wet film on the substrate surface. Step 4: Immediately transfer the glass slide loaded with the wet film to a preheated hot stage and heat-treat it at 60°C for 5 min in an air atmosphere. Then place it in a tube furnace and anneal it at 500°C for 2 h in an argon atmosphere as a protective gas to finally obtain the Ta3N5 / Bi2WO6-FTO photoelectrode material.
[0017] Example 3 This embodiment provides a method for preparing a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, including the following steps: Step 1: Add 0.9 g of bismuth nitrate to 40 mL of water and stir continuously for 30 min to prepare solution A; add 0.25 g of sodium tungstate to 25 mL of deionized water and stir for 30 min to prepare solution B; add solution A dropwise to solution B at a rate of 4 drops / s, add 6% relative volume fraction nitric acid to adjust the pH to 4, stir until uniform, add 0.15 g of sodium citrate and continue stirring for 2 h to obtain solution C; Solution C was transferred to a polytetrafluoroethylene liner and hydrothermally reacted at 140°C for 12 h. After cooling to room temperature, it was washed, dried, ground, and then calcined in a tube furnace at 300°C for 3 h. After cooling to room temperature, powder D was obtained. Step 2: Weigh 3 g of melamine and place it in an alumina ceramic boat at the inlet of a tube furnace. Then weigh 0.4 g of tantalum oxide and place it in the alumina ceramic boat at the center of the tube furnace. Heat the furnace to 1200℃ under an Ar atmosphere and maintain the temperature for 8 h. After cooling to room temperature, powder E is obtained. Step 3: Weigh 0.70 g of powder D and 0.15 g of powder E into beakers, add 180 mL of isopropanol to the beakers, stir for 2 h, and then sonicate for 60 min to obtain precursor solution F. Pre-treat the FTO conductive glass by ultrasonic cleaning with acetone, anhydrous ethanol and water in sequence. Using a dip coating machine, vertically immerse the FTO substrate into precursor solution F, let it stand for a few seconds, and then pull it up at a constant speed of 3 mm / s to form a uniform wet film on the substrate surface. Step 4: Immediately transfer the glass slide loaded with the wet film to a preheated hot stage and heat-treat it at 60°C for 8 min in an air atmosphere. Then place it in a tube furnace and anneal it at 450°C for 1.5 h in an argon atmosphere as a protective gas to finally obtain the Ta3N5 / Bi2WO6-FTO photoelectrode material.
[0018] Example 4 This embodiment provides a method for preparing a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, including the following steps: Step 1: Add 1.0 g of bismuth nitrate to 45 mL of water and stir continuously for 30 min to prepare solution A; add 0.30 g of sodium tungstate to 30 mL of deionized water and stir for 30 min to prepare solution B; add solution A dropwise to solution B at a rate of 5 drops / s, add 6% relative volume fraction nitric acid to adjust the pH to 6, stir until uniform, add 0.2 g of sodium citrate and continue stirring for 2 h to obtain solution C; Solution C was transferred to a polytetrafluoroethylene liner and hydrothermally reacted at 140°C for 8 h. After cooling to room temperature, it was washed, dried, ground, and then calcined in a tube furnace at 400°C for 1 h. After cooling to room temperature, powder D was obtained. Step 2: Weigh 3 g of melamine and place it in an alumina ceramic boat at the inlet of a tube furnace. Then weigh 0.4 g of tantalum oxide and place it in the alumina ceramic boat at the center of the tube furnace. Heat the furnace to 1200℃ under an Ar atmosphere and maintain the temperature for 8 h. After cooling to room temperature, powder E is obtained. Step 3: Weigh 0.35 g of powder D and 0.31 g of powder E into beakers, add 200 mL of isopropanol to the beakers, stir for 2 h, and then sonicate for 60 min to obtain precursor solution F. Pre-treat the FTO conductive glass by ultrasonic cleaning with acetone, anhydrous ethanol and water in sequence. Using a dip coating machine, vertically immerse the FTO substrate into the precursor solution F, let it stand for a few seconds, and then pull it up at a constant speed of 3 mm / s to form a uniform wet film on the substrate surface. Step 4: Immediately transfer the glass slide loaded with the wet film to a preheated hot stage and heat-treat it at 60°C for 10 min in an air atmosphere. Then place it in a tube furnace and anneal it at 500°C for 1 h in an argon atmosphere as a protective gas to finally obtain the Ta3N5 / Bi2WO6-FTO photoelectrode material.
[0019] The above-described specific embodiments are merely illustrative explanations of the present invention and do not constitute any limitation on the scope of protection of the present invention. Those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material, characterized in that, Includes the following steps: Step 1: Prepare Bi2WO6 powder using a hydrothermal reaction method; Step 2: Prepare Ta3N5 powder using a tube furnace gas-solid reactive nitriding method; Step 3: Weigh 0.35-0.70 g of Bi2WO6 powder and 0.15-0.31 g of Ta3N5 powder into beakers, add 150-200 mL of isopropanol to the beakers, stir the powders and ultrasonically disperse them until uniform to obtain precursor solution F. Using a dip coating machine, vertically immerse the pretreated FTO substrate into precursor solution F, let it stand for a few seconds, and then pull it up at a constant speed of 1-3 mm / s to form a uniform wet film on the substrate surface. Step 4: Immediately transfer the glass slide loaded with the wet film to a preheated hot stage and heat-treat it at 60°C for 5-10 min in an air atmosphere; finally, place the prepared film in a tube furnace and anneal it at 400-500°C for 1-2 h under an argon protective gas atmosphere to finally obtain the Ta3N5 / Bi2WO6-FTO photoelectrode material.
2. The method for preparing the Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material as described in claim 1, characterized in that, The method for preparing the Bi2WO6 powder includes: S1. Add 0.6-1.0 g of bismuth nitrate to 30-45 mL of water to prepare solution A; add 0.15-0.30 g of sodium tungstate to 15-30 mL of deionized water to prepare solution B; add solution A dropwise to solution B at a rate of 1-5 drops / s, adjust the pH to 4-6, stir until homogeneous, add 0.1-0.2 g of sodium citrate and continue stirring for 2 hours to obtain solution C; S2. Transfer solution C to a polytetrafluoroethylene liner and hydrothermally react at 120-140℃ for 8-14 h. After cooling to room temperature, wash, dry, grind, and place in a tube furnace for calcination at 200-400℃ for 1-4 h. After cooling to room temperature, obtain powder D, which is Bi2WO6 powder.
3. The method for preparing the Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material as described in claim 2, characterized in that, In step S1, 6% relative volume fraction of nitric acid is used to adjust the pH.
4. The method for preparing the Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material as described in claim 1, characterized in that, The method for preparing the Ta3N5 powder includes: Weigh 2-3 g of melamine and place it in an alumina ceramic boat at the inlet of a tube furnace. Then weigh 0.2-0.4 g of tantalum oxide and place it in the alumina ceramic boat at the center of the tube furnace. Heat the furnace to 600-1200℃ under an Ar atmosphere and maintain the temperature for 3-8 hours. After cooling to room temperature, powder E is obtained, which is Ta3N5 powder.
5. The method for preparing the Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material as described in claim 1, characterized in that, The pretreatment method for the FTO substrate includes ultrasonic cleaning with acetone, anhydrous ethanol and deionized water in sequence.
6. A Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material prepared by the method described in any one of claims 1 to 5.
7. The application of the Z-type heterojunction Ta3N5 / Bi2WO6-FTO photoelectrode material as described in claim 6 in electrocatalytic water splitting.