A ternary composite photo-anode material, a preparation method and application thereof

Abstract

The application relates to a ternary composite photoanode material and a preparation method and application thereof, and the preparation method is as follows: S1, pretreated Ti-Nb alloy is subjected to anodic oxidation treatment and crystallization treatment, and a Ti-Nb-O nanotube array photoanode is obtained after cooling to room temperature; S2, Bi2S3 is deposited on the Ti-Nb-O nanotube array by using a continuous ion layer method, and a Ti-Nb-O / Bi2S3 nanotube array photoanode is obtained after annealing in an inert atmosphere; S3, the Ti-Nb-O / Bi2S3 nanotube array photoanode is immersed in a CQDs solution, and then washing, drying are carried out, and a Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode material is obtained. Compared with the prior art, the ternary heterostructure is constructed, the electron hole separation is promoted, the recombination and the composite phenomenon are reduced, and the photocurrent density is increased by 22 times compared with the traditional Ti-O nanotube array.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical technology, and in particular to a ternary composite photoanode material, its preparation method, and its application. Background Technology

[0002] In the 21st century, rapid industrial development has brought tremendous convenience to human life, but it has also caused a series of environmental problems. With the over-exploitation of fossil fuels, energy issues have come to the forefront. In response to the national sustainable development strategy, the search for new renewable energy sources is urgent. Hydrogen energy is a promising energy source, with only water as a combustion product. It also boasts high energy density and is easy to store and transport, attracting widespread research attention. Since Fujishima and Honda discovered the photoelectrochemical decomposition of water to produce hydrogen and oxygen in 1972, photoelectrochemical water splitting using semiconductors as catalysts is currently the most promising technology. TiO2, due to its non-toxic, harmless, and inexpensive properties, has always been a research hotspot in the environmental field. However, TiO2 itself has a wide band gap, making electron-hole recombination easy. A common measure to improve this problem is elemental doping. Generally, metal ion doping, by introducing metal ions into TiO2, can form new impurity energy levels, narrowing the band gap, changing the mobility and electron concentration of TiO2, and also significantly producing other effects, such as changing the conduction band (CB) position, passivating surface defects, and influencing the TiO2 nanostructure. It has been reported that doping TiO2 with Nb, regardless of whether it is anatase or rutile phase, improves the conductivity of the original TiO2. Small amounts of Nb... 5+ Implantation can significantly improve charge transfer. When Nb is doped into TiO2, Nb... 5+ Replace Ti 4+ Formed on the conduction band of TiO2, for Ti 4+ It provides electrons and achieves a high carrier concentration.

[0003] The published photoelectrochemical properties of photocatalysts to date are far from satisfactory, exhibiting characteristics such as short excited-state lifetimes and relatively low charge separation efficiency. To address these issues, forming heterojunctions between TiO2 and various semiconductor materials can impart high conductivity and good mechanical properties. Furthermore, the synergistic effect between different components typically improves the separation efficiency of photogenerated electron-hole pairs, thereby enhancing catalytic activity. Transition metal sulfides possess advantages such as low cost, low overpotential, and high stability, and rarely exhibit lattice mismatch problems when combined with two-dimensional materials, thus finding widespread application in photoelectrochemistry. Bi2S3 nanoparticles possess a narrow bandgap (Eg = 1.7 eV) and a high absorption coefficient in the visible light region, making them excellent semiconductors for effectively absorbing sunlight and generating charge carriers. Their suitable band structure allows them to be compatible with Ti-Nb-O nanotube arrays for rapid electron transport, thereby improving the overall conductivity of the material and suppressing electron-hole recombination.

[0004] As an emerging optoelectronic material, carbon quantum dots (CQDs) possess numerous advantages due to their unique properties, such as high electron mobility, low cost, good stability, non-toxicity, and natural abundance. CQDs have been reported to serve as ultrafast charge channels in PEC devices and can effectively improve the OER kinetics of the photoanode. CQDs may contribute to the cathode shift of the water oxidation initiation potential in PECs, and they can also enhance ultraviolet light absorption and extend the light collection range to the visible region of the solar spectrum of the photoanode. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art, such as short excited-state lifetime and relatively low charge separation efficiency, and to provide a ternary composite photoanode material, its preparation method, and its application.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing a ternary composite photoanode material, comprising the following steps:

[0008] S1. First, the pretreated Ti-Nb alloy is subjected to anodic oxidation and crystallization treatment, and then cooled to room temperature to obtain Ti-Nb-O nanotube array photoanode;

[0009] S2. Bi2S3 is deposited on the Ti-Nb-O nanotube array obtained in step S1 using a continuous ion layer method, and then annealed in an inert atmosphere to obtain a Ti-Nb-O / Bi2S3 nanotube array photoanode.

[0010] S3. Immerse the Ti-Nb-O / Bi2S3 nanotube array photoanode obtained in step S2 into the CQDs solution, then wash and dry to obtain the Ti-Nb-O / Bi2S3 / CQDs nanotube array photoanode, i.e., ternary composite photoanode material.

[0011] Furthermore, in step S1, the pretreatment process is as follows: the Ti-Nb alloy is first polished with sandpaper until the surface is smooth, then ultrasonically cleaned with acetone, ethanol and deionized water for 15 minutes each, and then allowed to stand and dry at room temperature.

[0012] Further, in step S1, the anodizing process is as follows: using a mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol as the electrolyte, with Ti-Nb alloy as the anode and graphite plate as the cathode, the reaction is carried out for 1-4 hours at a DC voltage of 35-45V, followed by washing with deionized water and drying at room temperature.

[0013] Furthermore, in step S1, the crystallization temperature is 450-575℃, and the crystallization time is 1-4 hours.

[0014] Furthermore, in step S2, the process of the continuous ion layer method is as follows: the Ti-Nb-O nanotube array is sequentially immersed in bismuth source solution, deionized water, sulfur source solution, and deionized water, each for 10-60 seconds, which constitutes one cycle, and is repeated 5-20 times in total. After washing with deionized water, it is vacuum dried at 60°C for 6 hours.

[0015] Furthermore, the bismuth source is Bi(NO3)3·5H2O, the sulfur source is Na2S·9H2O, and the concentration ratio of the sulfur source to the bismuth source is 1-10 mmol:1-10 mmol.

[0016] Furthermore, in step S2, the inert atmosphere is Ar2, the annealing temperature is 200-350℃, and the annealing time is 1-3h.

[0017] Further, in step S3, 0.01-0.10 g of glucose is added to 50 mL of deionized water and stirred evenly with a glass rod to prepare a glucose solution, which is then heated at 100-180 °C for 5-15 h to obtain a CQDs solution; the Ti-Nb-O / Bi2S3 nanotube array photoanode is immersed in the CQDs solution and soaked at room temperature for 8-12 h; it is then washed with deionized water and vacuum dried at 60 °C for 6 h.

[0018] The second technical solution of the present invention is to provide a ternary composite photoanode material based on the preparation method described in one of the above technical solutions.

[0019] The third technical solution of the present invention is to provide an application of a ternary composite photoanode material, wherein the ternary composite photoanode material is applied in the field of photoelectrocatalysis.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) This invention provides a method for preparing Ti-Nb-O / Bi2S3 / CQDs ternary composite photoanode material. The preparation method is simple and the raw materials are inexpensive. The prepared ternary composite photoanode material has a higher specific surface area and more active sites on the surface and inside the tube. Due to the doping of Nb, the conductivity of Ti-O nanotube array is greatly improved, which can suppress the recombination of electrons and holes.

[0022] (2) The present invention constructs a Ti-Nb-O / Bi2S3 / CQDs ternary heterojunction for rapid electron transport, thereby improving the overall conductivity of the material and suppressing electron-hole recombination so that photogenerated carriers at different energy levels will transfer and separate, suppressing the recombination of photogenerated electron-hole pairs. At the same time, the synergistic effect of Nb doping and Bi2S3 recombination improves the conductivity of Ti-Nb-O nanotube array and the absorption of visible light.

[0023] (3) Compared with the traditional TiO2 nanotube array, the ternary heterostructure prepared by the present invention can greatly promote electron-hole separation and improve its response to visible light by loading CQDs and Bi2S3 quantum dots onto the Ti-Nb-O nanotube array. Experiments have shown that its photocurrent density is increased by 22 times. Attached Figure Description

[0024] Figure 1 Comparative graphs of the cyclic voltammetry curves of the photoanode materials prepared in Example 3, Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6 under full light conditions.

[0025] Figure 2 Comparative graphs of the photoanode materials prepared in Example 3, Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6 under visible light are shown.

[0026] Figure 3 The graph shows the photohydrogen conversion efficiency of the photoanode materials prepared in Examples 3, 2, 4, 5, and 6. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0028] Unless otherwise specified, the raw materials or processing techniques used in the following embodiments and comparative examples are all conventional commercially available raw materials or conventional processing techniques in the art.

[0029] Example 1:

[0030] A method for preparing a Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode material, comprising the following steps:

[0031] (1) Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240 mesh, 1000 mesh and 1500 mesh water sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15min respectively.

[0032] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0033] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode with titanium mineral phase.

[0034] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-Nb-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 7 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. Then transfer it to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain Ti-Nb-O / Bi2S3 nanotube array.

[0035] (3) Preparation of CQDs: 0.09 g of glucose and 50 mL of deionized water were stirred evenly with a glass rod to prepare a glucose solution. The solution was then transferred to a polytetrafluoroethylene liner and hydrothermally heated at 180 °C for 10 h. The CQDs solution was obtained after cooling to room temperature.

[0036] The Ti-Nb-O / Bi2S3 nanotube array was immersed in CQDs solution at room temperature for 5 hours, then washed three times with deionized water, and transferred to a vacuum drying oven at 60°C for 6 hours to obtain the Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode electrode material.

[0037] Three-electrode tests were performed using the Chenhua CHI660E electrochemical workstation employing different LSV, IT, VOPT, EIS, and MOTT methods. The working electrode, counter electrode, and reference electrode were connected to the electrochemical workstation, with a xenon lamp as the light source and an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0038] Example 2:

[0039] A method for preparing a Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode material, comprising the following steps:

[0040] (1) Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240 mesh, 1000 mesh and 1500 mesh water sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15min respectively.

[0041] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0042] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode with titanium mineral phase.

[0043] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-Nb-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 7 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. Then transfer it to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain Ti-Nb-O / Bi2S3 nanotube array.

[0044] (3) Preparation of CQDs: 0.09 g of glucose and 50 mL of deionized water were stirred evenly with a glass rod to prepare a glucose solution. The solution was then transferred to a polytetrafluoroethylene liner and hydrothermally heated at 180 °C for 10 h. The CQDs solution was obtained after cooling to room temperature.

[0045] The Ti-Nb-O / Bi2S3 nanotube array was immersed in CQDs solution at room temperature for 10 hours, then washed three times with deionized water, and transferred to a vacuum drying oven at 60°C for 6 hours to obtain the Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode electrode material.

[0046] Three-electrode tests were performed using the Chenhua CHI660E electrochemical workstation employing different LSV, IT, VOPT, EIS, and MOTT methods. The working electrode, counter electrode, and reference electrode were connected to the electrochemical workstation, with a xenon lamp as the light source and an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0047] Example 3:

[0048] A method for preparing a Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode material, comprising the following steps:

[0049] (1) Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240 mesh, 1000 mesh and 1500 mesh water sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15min respectively.

[0050] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0051] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode with titanium mineral phase.

[0052] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-Nb-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 7 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. Then transfer it to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain Ti-Nb-O / Bi2S3 nanotube array.

[0053] (3) Preparation of CQDs: 0.09 g of glucose and 50 mL of deionized water were stirred evenly with a glass rod to prepare a glucose solution. The solution was then transferred to a polytetrafluoroethylene liner and hydrothermally heated at 180 °C for 10 h. The CQDs solution was obtained after cooling to room temperature.

[0054] The Ti-Nb-O / Bi2S3 nanotube array was immersed in CQDs solution at room temperature for 15 hours, then washed three times with deionized water, and transferred to a vacuum drying oven at 60°C for 6 hours to obtain the Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode electrode material.

[0055] Three-electrode tests were performed using the Chenhua CHI660E electrochemical workstation employing different LSV, IT, VOPT, EIS, and MOTT methods. The working electrode, counter electrode, and reference electrode were connected to the electrochemical workstation, with a xenon lamp as the light source and an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0056] Comparative Example 1:

[0057] A method for preparing a Ti-Nb-O / Bi2S3 nanotube array composite photoanode material, comprising the following steps:

[0058] (1) Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240 mesh, 1000 mesh and 1500 mesh water sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15min respectively.

[0059] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0060] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature with the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode of the titanium mineral phase.

[0061] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-Nb-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 5 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. After drying, transfer the Ti-Nb-O / Bi2S3 nanotube array to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain the Ti-Nb-O / Bi2S3 nanotube array.

[0062] Three-electrode tests were performed using the Chenhua CHI660E electrochemical workstation employing different LSV, IT, VOPT, EIS, and MOTT methods. The working electrode, counter electrode, and reference electrode were connected to the electrochemical workstation, with a xenon lamp as the light source and an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0063] Comparative Example 2:

[0064] A method for preparing a Ti-Nb-O / Bi2S3 nanotube array composite photoanode material, comprising the following steps:

[0065] (1) Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240 mesh, 1000 mesh and 1500 mesh water sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15min respectively.

[0066] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0067] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode with titanium mineral phase.

[0068] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-Nb-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 7 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. After drying, transfer the Ti-Nb-O / Bi2S3 nanotube array to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain the Ti-Nb-O / Bi2S3 nanotube array.

[0069] Using the Chenhua CHI660E electrochemical workstation, a three-electrode testing system was conducted using different LSV, IT, VOPT, EIS, and MOTT methods. The working electrode, counter electrode, and reference electrode were connected to the electrochemical workstation, and a xenon lamp was used as the light source with an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0070] Comparative Example 3:

[0071] A method for preparing a Ti-Nb-O / Bi2S3 nanotube array composite photoanode material, comprising the following steps:

[0072] (1) Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240 mesh, 1000 mesh and 1500 mesh water sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 15min respectively.

[0073] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0074] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode with titanium mineral phase.

[0075] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-Nb-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 9 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. After drying, transfer the Ti-Nb-O / Bi2S3 nanotube array to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain the Ti-Nb-O / Bi2S3 nanotube array.

[0076] Using the Chenhua CHI660E electrochemical workstation, different cyclic voltammetry, constant current charge-discharge, and electrochemical impedance spectroscopy methods were employed. A three-electrode testing system was used, with the working electrode, counter electrode, and reference electrode connected to the workstation. The light source was a xenon lamp with an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0077] Comparative Example 4:

[0078] A method for preparing a Ti-Nb-O nanotube array composite photoanode material, comprising the following steps:

[0079] Pretreatment: The Ti-Nb alloy sheet with a size of 10mm×20mm×1mm (Nb content of 3%) was polished with 240-grit, 1000-grit, and 1500-grit wet sandpaper until the surface was smooth. Then it was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes respectively.

[0080] Anodizing: The treated Ti-Nb alloy sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-Nb-O nanotube array.

[0081] Crystallization treatment: The anodized Ti-Nb-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain a Ti-Nb-O nanotube array photoanode with titanium mineral phase.

[0082] Using the Chenhua CHI660E electrochemical workstation, different cyclic voltammetry, constant current charge-discharge, and electrochemical impedance spectroscopy methods were employed. A three-electrode testing system was used, with the working electrode, counter electrode, and reference electrode connected to the workstation. The light source was a xenon lamp with an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0083] Comparative Example 5:

[0084] A method for preparing a Ti-O nanotube array photoanode includes the following steps:

[0085] Pretreatment: Pure Ti wafers with dimensions of 10mm×20mm×1mm were polished with 240-grit, 1000-grit, and 1500-grit wet sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes respectively.

[0086] Anodizing: The treated Ti sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40 V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-O nanotube array.

[0087] Crystallization treatment: The anodized Ti-O nanotube array is transferred to a muffle furnace and annealed at 550℃ for 2 hours. After cooling to room temperature in the furnace, it is taken out to obtain an anatase phase Ti-O nanotube array photoanode.

[0088] Using the Chenhua CHI660E electrochemical workstation, different cyclic voltammetry, constant current charge-discharge, and electrochemical impedance spectroscopy methods were employed. A three-electrode testing system was used, with the working electrode, counter electrode, and reference electrode connected to the workstation. The light source was a xenon lamp with an illumination intensity of 100 mW / cm². -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0089] Comparative Example 6:

[0090] A method for preparing a Ti-O / Bi2S3 nanotube array photoanode, comprising the following steps:

[0091] (1) Pretreatment: Pure Ti wafers with dimensions of 10mm×20mm×1mm were polished with 240-grit, 1000-grit, and 1500-grit wet sandpaper until the surface was smooth, and then ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 15 minutes respectively.

[0092] Anodizing: The treated Ti sheet was used as the anode and the graphite plate as the cathode. A mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol was used as the electrolyte. The oxidation was carried out for 1 hour under a DC voltage of 40 V. Then, the surface impurities were cleaned with deionized water and dried at room temperature to obtain a Ti-O nanotube array.

[0093] Crystallization treatment: The anodized Ti-O nanotube array is transferred to a muffle furnace and annealed at 550°C for 2 hours. After cooling to room temperature with the furnace, it is taken out to obtain an anatase phase Ti-O nanotube array photoanode.

[0094] (2) Weigh 0.2425g Bi(NO3)3·5H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution A. Weigh 0.1201g Na2S·9H2O and dissolve it in 100mL of deionized water. Mix well to obtain solution B. Immerse the Ti-O nanotube array photoanode obtained in S1 in solution A for 30s, deionized water for 30s, solution B for 30s, and deionized water for 30s in sequence. This step is called one cycle. Repeat the cycle 7 times. Then wash it three times with deionized water and transfer it to a vacuum drying oven at 60℃ for 6h. After drying, transfer the Ti-O / Bi2S3 nanotube array to a tube furnace filled with Ar2 for annealing treatment at 350℃ for 2h. Cool it to room temperature to obtain the Ti-O / Bi2S3 nanotube array photoanode.

[0095] Using the Chenhua CHI660E electrochemical workstation, different cyclic voltammetry, constant current charge-discharge, and electrochemical impedance spectroscopy methods were employed. A three-electrode testing system was used, with the working electrode, counter electrode, and reference electrode connected to the workstation. A xenon lamp with an illumination intensity of 100 mW / cm² was used as the light source. -2 The photoelectrochemical properties of the electrode material were measured in 0.35M Na2S and 0.25M Na2SO3 solutions.

[0096] The photoelectrochemical performance of the above embodiments and comparative examples is shown in Table 1.

[0097] Table 1. Comparison of photocurrent densities of photoanode materials prepared in the examples and comparative examples.

[0098]

[0099] As can be seen from the table, the photocurrent density of the Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode materials prepared in Examples 1-3 is higher than that of the Ti-Nb-O / Bi2S3 nanotube array photoanode materials prepared in Comparative Examples 1-3, Comparative Example 4, Comparative Example 5, and Comparative Example 6. This is mainly because carbon dots, as photosensitizers, synergistically construct a continuous type II heterojunction with Bi2S3, thereby suppressing electron-hole recombination and improving its performance. The Ti-Nb-O / Bi2S3 nanotube array photoanode material prepared in Comparative Example 2 also has a higher photocurrent density than the Ti-Nb-O nanotube array photoanode material prepared in Comparative Example 4, the Ti-O nanotube array photoanode material prepared in Comparative Example 5, and the Ti-O / Bi2S3 nanotube array photoanode material prepared in Comparative Example 6. This is mainly because Nb doping introduces an impurity energy level into the Ti-O nanotube array, thereby shifting the conduction band and valence band downward, thus reducing the band gap value and making the Bi2S3 and Ti-Nb-O energy bands more matched. The photocurrent density of the Ti-O / Bi2S3 nanotube array photoanode material prepared in Comparative Example 6 is higher than that of the Ti-O nanotube array photoanode material prepared in Comparative Example 5. This indicates that a type II heterojunction is formed between Bi2S3 and the Ti-O nanotube array. When irradiated by light, electrons and holes are separated. Electrons flow to the Ti-O substrate and transfer to the counter electrode for hydrogen evolution, while holes transfer from the conduction band of Ti-O to the conduction band of Bi2S3 to participate in the oxygen evolution reaction, thereby inhibiting electron-hole recombination.

[0100] Figure 1The figures show a comparison of the cyclic voltammetry curves of the photoanode materials prepared in Example 3, Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6 under full-light conditions. The results show that the photocurrent density of the Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode material prepared in Example 3 is higher than that of the Ti-Nb-O / Bi2S3 nanotube array photoanode materials prepared in Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6.

[0101] Figure 2 The figures show a comparison of the cyclic voltammetry curves of the photoanode materials prepared in Example 3, Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6 after filtering out light below 420 nm. The results show that the photocurrent density of the Ti-Nb-O / Bi2S3 / CQDs nanotube array ternary composite photoanode material prepared in Example 3 is higher than that of the Ti-Nb-O / Bi2S3 nanotube array photoanode materials prepared in Comparative Example 2, Comparative Example 4, Comparative Example 5, and Comparative Example 6.

[0102] Figure 3 The graphs show the photohydrogen conversion efficiency of the photoanode materials prepared in Examples 3, 2, 4, 5, and 6. The results show that the photohydrogen conversion efficiency of the Ti-Nb-O / Bi₂S₃ / CQDs nanotube array ternary composite photoanode material prepared in Example 3 is higher than that of the Ti-Nb-O / Bi₂S₃ nanotube array photoanode material prepared in Comparative Example 2, 4, 5, and 6.

[0103] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a ternary composite photoanode material, characterized in that, Includes the following steps: S1. First, the pretreated Ti-Nb alloy is subjected to anodic oxidation and crystallization treatment, and then cooled to room temperature to obtain Ti-Nb-O nanotube array photoanode; S2. Bi2S3 is deposited on the Ti-Nb-O nanotube array obtained in step S1 using a continuous ion layer method, and then annealed in an inert atmosphere to obtain a Ti-Nb-O / Bi2S3 nanotube array photoanode. S3. Immerse the Ti-Nb-O / Bi2S3 nanotube array photoanode obtained in step S2 into the CQDs solution, then wash and dry to obtain the Ti-Nb-O / Bi2S3 / CQDs nanotube array photoanode, i.e., ternary composite photoanode material; In step S2, the continuous ion layer method is as follows: the Ti-Nb-O nanotube array is sequentially immersed in bismuth source solution, deionized water, sulfur source solution, and deionized water, each for 10-60 s, which constitutes one cycle, and is repeated 5-20 times in total. Then it is washed with deionized water and vacuum dried at 60 °C for 6 h. The bismuth source was Bi(NO3)3·5H2O, and the sulfur source was Na2S·9H2O. The concentration ratio of the sulfur source to the bismuth source was 1-10 mmol : 1-10 mmol. In step S3, the CQDs solution is prepared as follows: 0.01-0.10 g of glucose is added to 50 mL of deionized water and stirred evenly with a glass rod to prepare a glucose solution, which is then heated at 100-180 °C for 5-15 h to obtain the CQDs solution; the Ti-Nb-O / Bi2S3 nanotube array photoanode is immersed in the CQDs solution and soaked at room temperature for 8-12 h; it is then washed with deionized water and vacuum dried at 60 °C for 6 h; The Bi2S3 is deposited on the surface of the Ti-Nb-O nanotube array, and the CQDs are loaded on the surface of Bi2S3 and form a continuous type II heterojunction with Bi2S3.

2. The method for preparing the ternary composite photoanode material according to claim 1, characterized in that, In step S1, the pretreatment process is as follows: the Ti-Nb alloy is first polished with sandpaper until the surface is smooth, then ultrasonically cleaned with acetone, ethanol and deionized water for 15 min each, and then allowed to stand and dry at room temperature.

3. The method for preparing the ternary composite photoanode material according to claim 1, characterized in that, In step S1, the anodic oxidation process is as follows: using a mixed solution of 0.4 wt.% NH4F and 2 vol.% H2O in ethylene glycol as the electrolyte, with Ti-Nb alloy as the anode and graphite plate as the cathode, the reaction is carried out for 1-4 h at a DC voltage of 35-45 V, followed by washing with deionized water and drying at room temperature.

4. The method for preparing the ternary composite photoanode material according to claim 1, characterized in that, In step S1, the crystallization temperature is 450-575 °C and the crystallization time is 1-4 h.

5. The method for preparing the ternary composite photoanode material according to claim 1, characterized in that, In step S2, the inert atmosphere is Ar, the annealing temperature is 200-350 °C, and the annealing time is 1-3 h.

6. A ternary composite photoanode material, characterized in that, The preparation method of the ternary composite photoanode material according to any one of claims 1-5.

7. An application of the ternary composite photoanode material as described in claim 6, characterized in that, The ternary composite photoanode material is applied in the field of photoelectrocatalysis.

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