Preparation method and application of cadmium sulfide / zinc oxide / titanium dioxide composite photoanode

Abstract

The present invention discloses a preparation method and application of a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode, which mainly includes the following steps: 1) synthesizing TiO2 through a one-step hydrothermal method to form a well-formed one-dimensional TiO2 nanorod array film on conductive glass; 2) growing a ZnO seed layer on the one-dimensional TiO2 nanorod array film using an immersion method, and then hydrothermally preparing ZnO nanorods on the one-dimensional TiO2 nanorod film with the ZnO seed layer to form a TiO2-ZnO hierarchical structure; and 3) hydrothermally synthesizing CdS quantum dots using cadmium chloride as a cadmium source and thiourea as a sulfur source to prepare a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode. The present invention uses a hydrothermal method to prepare the composite photoanode, which can improve the photoelectric conversion efficiency, increase the light absorption capacity of the photoactive layer, and improve the photoelectric conversion performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor material preparation, in particular to a preparation method and application of a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode. Background Art

[0002] As people's demand for non-renewable energy such as coal, natural gas, and oil increases day by day, resulting in the rapid consumption of non-renewable energy, renewable clean energy represented by solar energy has received widespread attention.

[0003] Solar cells include crystalline silicon cells and thin-film cells. Thin-film cells have attracted widespread attention due to their low cost and high efficiency, and the photoanode is particularly important to the performance of these cells. The n-type semiconductor TiO2 is one of the many photoanode materials. Its low cost and good thermal stability make it a popular choice for the preparation and modification of photoanode composite materials. Currently, TiO2 preparation methods primarily include hydrothermal, sol-gel, precipitation, physical deposition, hydrolysis, and plasma-enhanced CVD. The hydrothermal method is commonly used to produce dense and stable TiO2 thin films. However, TiO2 prepared using the hydrothermal method has a large bandgap (3.2 eV) and is limited to the wavelength of light it absorbs. This limits its ability to effectively absorb visible light, resulting in poor photoelectrochemical performance. Furthermore, pure TiO2 contains recombination centers for photogenerated electron-hole pairs, which hinders their separation and significantly affects its photoelectric conversion performance. Summary of the Invention

[0004] In order to address the deficiencies in the prior art, the present invention provides a preparation method and application of a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode. The present invention adopts a hydrothermal method to prepare the composite photoanode, which can improve the photoelectric conversion efficiency, increase the light absorption capacity of the photoactive layer, and improve the photoelectric conversion performance of the battery.

[0005] In order to achieve the above object, the specific scheme adopted by the present invention is:

[0006] A method for preparing a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode mainly comprises the following steps:

[0007] S1. Growing a TiO2 nanorod film on the conductive layer of the conductive glass using a hydrothermal method, immersing the conductive glass with the TiO2 nanorod film in a ZnO sol for 20 to 30 minutes, taking it out and drying it, and then annealing it at a temperature of 400 to 450°C for 30 to 50 minutes, thereby growing a zinc oxide / titanium dioxide nanorod film on the conductive layer of the conductive glass;

[0008] S2, preparing ZnO precursor solution;

[0009] S3. The ZnO precursor solution prepared in step S2 is transferred to a reactor, and the conductive glass with the zinc oxide / titanium dioxide nanorod film grown thereon obtained in step S1 is tiltedly placed into the reactor, and hydrothermally grown at 80-100° C. for 2.5-3.5 hours. The film is then rinsed, dried, and annealed, thereby growing a zinc oxide / titanium dioxide nanorod hierarchical structure film on the conductive layer of the conductive glass.

[0010] S4, preparing a CdS precursor solution;

[0011] S5. Transfer the CdS precursor solution prepared in step S4 to a reactor, tilt the conductive glass with the zinc oxide / titanium dioxide nanorod hierarchical structure film grown thereon obtained in step S3 into the reactor, hydrothermally grow the film at 120-170° C. for 2-8 hours, remove the film, clean and dry it, and obtain a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode.

[0012] Furthermore, in step S1, the specific method for preparing the zinc oxide / titanium dioxide nanorod film is as follows: in a warm water bath, 1.5-2.0 mL of diethanolamine is added to 50 mL of an ethanol solution of zinc acetate with a concentration of 0.3 mol / L-0.5 mol / L, and the mixture is stirred evenly to obtain a ZnO sol.

[0013] Furthermore, in step S2, the specific method for preparing the ZnO precursor solution is: adding a hexamethylenetetramine aqueous solution with a concentration of 0.01 mol / L to 0.03 mol / L to an aqueous solution of zinc nitrate with a concentration of 0.01 mol / L to 0.03 mol / L, and stirring uniformly to obtain the ZnO precursor solution.

[0014] Furthermore, in step S3, the hydrothermal product is rinsed and dried, and then annealed at a temperature of 400-450° C. for 30-50 minutes.

[0015] Furthermore, in step S4, the specific method for preparing the CdS precursor solution is: first prepare a 0.16-0.4 mol / L cadmium chloride solution and a 0.16-0.4 mol / L thiourea solution respectively, and then mix the cadmium chloride and thiourea solutions evenly to obtain a 0.08-0.2 mol / L CdS precursor solution.

[0016] Furthermore, in step S5, the conductive glass on which the zinc oxide / titanium dioxide nanorod hierarchical structure thin film is grown obtained in step S3 is placed obliquely into a reactor and hydrothermally grown at 160° C. for 6 hours.

[0017] A cadmium sulfide / zinc oxide / titanium dioxide composite photoanode is obtained by adopting the above-mentioned preparation method.

[0018] Cadmium sulfide / zinc oxide / titanium dioxide composite photoanodes are used in dye-sensitized solar cells, photocatalytic degradation of pollutants, and photolysis of water.

[0019] CdS has a narrow band gap (2.4eV) and can absorb light in the range of visible light. When combined with TiO2, it can effectively improve the light absorption performance of the semiconductor material, so that the composite material can effectively absorb in the visible light region and improve the utilization rate of sunlight.

[0020] The present invention adopts butyl titanate (C 16 H 36 O4Ti) as Ti 4+ Concentrated hydrochloric acid (HCl) is used to adjust the acidic environment of the hydrothermal reaction. Zinc acetate [Zn(CH3COO)2·2H2O] is used as the Zn of the ZnO sol in step S1. 2+ The precursor and source of ZnO, anhydrous ethanol (CH3CH2OH) is used as the solvent of ZnO sol in step S1, diethanolamine [HN(CH2CH2OH)2] is used as a complexing agent to promote the growth of ZnO crystals, zinc nitrate [Zn(NO3)2·6H2O] is used as the Zn in step S2. 2+ Precursor and source of hexamethylenetetramine (C6H 12 N4) was used as an alkali source to react with zinc nitrate to generate ZnO nanorods, cadmium chloride (CdCl2•2.5H2O) and thiourea (CH4N2S) were used as Cd 2+ and S 2- precursors and sources.

[0021] Preparation method: The present invention adopts a two-step hydrothermal method for preparation. Compared with the simpler continuous ion layer adsorption method, the CdS particles grown by the hydrothermal method are larger and the heterojunction formation effect is better. At the same time, the preparation is relatively simple, the required reaction environment is simple, the time is not too long, the reaction conditions are also easy to control, and the prepared CdS nanocrystal particles are easy to characterize, and the morphology can be clearly seen under a scanning electron microscope. Compared with methods such as the template method, the hydrothermal method is simpler to operate, and experimental samples with different effects can be obtained by regulating the temperature and time of the hydrothermal reaction. In addition, the reaction environment is closed and the reaction system is an aqueous solution, so no harm is caused to the environment during the reaction process.

[0022] Reaction mechanism: (1) TiO2 is synthesized by a one-step hydrothermal method to generate a well-morphed one-dimensional TiO2 nanorod array film on conductive glass; (2) A ZnO seed layer is grown on the one-dimensional TiO2 nanorod array film by an immersion method, and then ZnO nanorods are hydrothermally prepared on the one-dimensional TiO2 nanorod film with the ZnO seed layer to form a TiO2-ZnO hierarchical structure; (3) CdS quantum dots are hydrothermally synthesized using cadmium chloride as the cadmium source and thiourea as the sulfur source to prepare a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode.

[0023] Technical Benefits: This invention utilizes only a hydrothermal method, and the hydrothermal reaction temperature is not too high, and the reaction time is not too long. Compared to other hierarchically structured quantum dot-sensitized samples, the method simplifies the operational technical requirements and makes it easier to achieve experimental conditions. The invention discloses a method for preparing a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode. The resulting product is used to improve photoelectric conversion efficiency. By composite-forming a narrower bandgap ZnO with a wide-bandgap semiconductor TiO2 and forming a hierarchical structure, the bandgap width of the material is reduced, the contact area of ​​the CdS quantum dots is increased, and more photosensitizer is adsorbed, thereby increasing the light absorption capacity of the photoactive layer and improving the photoelectric conversion performance of the cell.

[0024] Results: The present invention modifies TiO2 with a hierarchical ZnO structure, thereby obtaining a composite material with better performance after sensitization with CdS quantum dots. The transient photocurrent density of the cadmium sulfide / zinc oxide / titanium dioxide composite photoanode material obtained under the conditions of CdS hydrothermal sensitization reaction temperature and time (160°C, 6h) is 1.5~2.0 mA / cm 2 ) Compared with the transient photocurrent density of TiO2 thin film (0.03 mA / cm 2 ) increased by more than 50 times, compared with the transient photocurrent density of ZnO / TiO2 nanorod hierarchical structure film (0.12 mA / cm 2) increased by more than 10 times. Specifically, the characteristic peak frequency of the cadmium sulfide / zinc oxide / titanium dioxide composite photoanode material prepared under the conditions of CdS hydrothermal sensitization temperature and time (160°C, 6 hours) was 1 Hz, corresponding to a minority carrier lifetime of 159.15 ms. In contrast, the characteristic peak frequency of a single TiO2 thin film was 97.7 Hz, corresponding to a minority carrier lifetime of 1.63 ms. Therefore, the composite material obtained by forming a hierarchical structure of TiO2 composite narrow-bandgap semiconductors and then modifying them with CdS has a minority carrier lifetime nearly 100 times higher than that of a single TiO2 thin film material. Furthermore, the cadmium sulfide / zinc oxide / titanium dioxide composite photoanode material exhibited low impedance when subjected to CdS hydrothermal sensitization at 160°C for 6 hours. This indicates that a hydrothermal reaction temperature of 160°C optimizes charge transfer at the interface, effectively reducing electron-hole recombination and inhibiting reverse electron transfer from the photoanode film to the electrode. This allows efficient transfer of photogenerated electricity to the TiO2, where it is then collected by the FTO, improving the utilization rate of photogenerated electrons. Furthermore, the CdS hydrothermal sensitization reaction temperature of 160°C and a reaction time of 6 hours exhibited the highest transient photocurrent density. Therefore, the optimal reaction conditions for CdS hydrothermal sensitization of the present invention are 160°C for 6 hours.

[0025] Beneficial effects:

[0026] The preparation method of a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode disclosed in the present invention has the following advantages:

[0027] (1) The present invention uses TiO2 with excellent photoelectric conversion performance and ZnO with excellent mobility properties as wide bandgap semiconductor materials, and adopts a hydrothermal method to grow small-sized secondary ZnO nanorods on TiO2 one-dimensional nanorods, thereby preparing a zinc oxide / titanium dioxide nanorod hierarchical structure film as the substrate of the composite photoanode. By utilizing the zinc oxide / titanium dioxide nanorod hierarchical structure film to form absorption light scattering, extend the light path, improve the light absorption efficiency, and increase the interface area of ​​the array, more photosensitizers can be adsorbed or deposited, thereby improving the light absorption capacity of the photoactive layer and improving the photoelectric conversion performance of the battery.

[0028] (2) The preparation method of the present invention is simple to operate, low in cost, highly repeatable, and has good stability, which greatly improves the photoelectric performance of the thin film material. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the preparation process of the composite photoanode in Example 1.

[0030] Figure 2 This is the XRD pattern of the composite photoanode prepared in Example 1-4.

[0031] Figure 3This is a scanning electron microscope image of the TiO2 nanorod film prepared in Comparative Example 1.

[0032] Figure 4 This is a scanning electron microscope image of the zinc oxide / titanium dioxide nanorod hierarchical structure film prepared in Comparative Example 2.

[0033] Figure 5 This is a scanning electron microscope image of the cadmium sulfide / titanium dioxide composite photoanode prepared in Comparative Example 3.

[0034] Figure 6 This is a scanning electron microscope image of the composite photoanode prepared in Example 3.

[0035] Figure 7 1 is the impedance diagram of the composite photoanode prepared in Examples 1 to 4.

[0036] Figure 8 3 is a phase angle frequency diagram of the composite photoanode prepared in Comparative Example 1 and Examples 2 to 4.

[0037] Figure 9 Graphs of transient photocurrents of the composite photoanodes prepared in Comparative Examples 1-2 and Examples 1-4 are shown. DETAILED DESCRIPTION

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0039] A method for preparing a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode comprises the following steps:

[0040] S1, preparation of ZnO / TiO2 nanorod film;

[0041] S11, growing a TiO2 nanorod film on the conductive layer of FTO conductive glass using a hydrothermal method;

[0042] S12. In a warm water bath, add diethanolamine (the diethanolamine used is a liquid organic reagent, and 1.5-2.0 mL can be directly added dropwise) to 50 mL of a 0.3 mol / L-0.5 mol / L zinc acetate ethanol solution, and stir evenly to obtain a ZnO sol.

[0043] S13, immersing the conductive glass with the TiO2 nanorod film in ZnO sol for 20-30 minutes, taking it out and drying it, and then annealing it at a temperature of 400-450° C. for 30-50 minutes, thereby growing a zinc oxide / titanium dioxide nanorod film on the conductive layer of the FTO conductive glass;

[0044] S2. Prepare a ZnO precursor solution: add a hexamethylenetetramine aqueous solution with a concentration of 0.01 mol / L to 0.03 mol / L to an aqueous solution of zinc nitrate with a concentration of 0.01 mol / L to 0.03 mol / L, and stir evenly to obtain a ZnO precursor solution;

[0045] S3. The ZnO precursor solution prepared in step S2 is transferred to a reactor, and the FTO conductive glass with the zinc oxide / titanium dioxide nanorod film grown thereon obtained in step S1 is tiltedly placed into the reactor, and hydrothermally grown at 80-100° C. for 2.5-3.5 hours, with the angle between the conductive glass and the substrate in the reactor being 45-60°. After the reaction is completed, the obtained film is alternately rinsed with deionized water and ethanol, dried, and annealed at 400-450° C. for 30-50 minutes, thereby growing a zinc oxide / titanium dioxide nanorod hierarchical structure film on the conductive layer of the conductive glass;

[0046] S4. Prepare a CdS precursor solution: first prepare a 0.16-0.4 mol / L cadmium chloride solution and a 0.16-0.4 mol / L thiourea solution respectively, and then mix the cadmium chloride and thiourea solutions evenly to prepare a 0.08-0.2 mol / L CdS precursor solution;

[0047] S5. Transfer the CdS precursor solution prepared in step S4 to a reactor, tilt the conductive glass with the zinc oxide / titanium dioxide nanorod hierarchical structure film grown thereon obtained in step S3 into the reactor, hydrothermally grow the film at 120-170° C. for 2-8 hours, remove the film, clean and dry it, and obtain a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode.

[0048] A cadmium sulfide / zinc oxide / titanium dioxide composite photoanode is prepared by the above preparation method.

[0049] The cadmium sulfide / zinc oxide / titanium dioxide composite photoanode is used in the fields of dye-sensitized solar cells, photocatalytic degradation of pollutants and photolysis of water.

[0050] The FTO substrate used in the present invention was purchased from South China Xiangcheng Technology Co., Ltd.; butyl titanate (C 16 H 36 O4Ti), concentrated hydrochloric acid (HCl), zinc acetate [Zn(CH3COO)2·2H2O], anhydrous ethanol (CH3CH2OH), diethanolamine [HN(CH2CH2OH)2], zinc nitrate [Zn(NO3)2·6H2O], hexamethylenetetramine (C6H 12 N4), cadmium chloride (CdCl2•2.5H2O), and thiourea (CH4N2S) were purchased from the market.

[0051] Example 1

[0052] (1) After scrubbing the FTO glass substrate with detergent, ultrasonically clean it with acetone, alcohol, and deionized water for 20 minutes, and then place it in an electric blast drying oven to dry;

[0053] (2) Use a measuring cylinder in a fume hood to measure 15 mL of concentrated HCl and 15 mL of deionized water, respectively, and pour them into a beaker to mix. Then seal the mixed beaker with plastic wrap and place it on a constant temperature magnetic stirrer to stir for 15 minutes. After mixing evenly, add 0.5 mL of butyl phthalate (C 16 H 36 O4Ti), and stirred for 40 min to make the mixed solution colorless, uniform and transparent, thus successfully preparing the precursor solution of TiO2 nanorod arrays;

[0054] (3) Place the conductive glass dried in step (1) with the conductive surface facing downward into the inner lining of the reactor, with the angle between the glass and the inner lining being 60°. Transfer the reaction solution obtained in step (1) to the polytetrafluoroethylene lining. Heat and insulate the reactor in a blast drying oven at 160°C for a hydrothermal reaction time of 10 hours, and then cool to room temperature in the furnace.

[0055] (4) The TiO2 film obtained in step (3) was taken out and rinsed with deionized water and alcohol in sequence. The dried sample was placed in a crucible and annealed in a muffle furnace at a heating rate of 5°C / min from room temperature to 450°C, followed by holding for 30 minutes and cooling in the furnace to obtain a TiO2 nanorod film;

[0056] (5) Prepare 0.4 mol / L zinc acetate ethanol solution, add diethanolamine in a water bath, and stir for 30 min to obtain ZnO sol;

[0057] (6) Immerse the conductive glass with the TiO2 thin film obtained in step (3) in the sol prepared above for 30 minutes;

[0058] (7) After drying and annealing (temperature: 450°C, holding time: 30 min), a zinc oxide / titanium dioxide nanorod film was obtained;

[0059] (8) Prepare a 0.02 mol / L aqueous solution of zinc nitrate, add 0.02 mol / L hexamethylenetetramine, and stir for 20-30 min;

[0060] (9) After stirring evenly, transfer 15 mL of the reaction solution obtained in step (8) to a high-pressure reactor (capacity 50 mL), place the FTO conductive glass with the ZnO seed layer coated with TiO2 one-dimensional nanorods with the conductive surface facing downward, with the angle between the glass and the inner substrate at 60°, and hydrothermally grow at 90°C for 3.5 h;

[0061] (10) After the reaction is completed, the film obtained in step (9) is washed alternately with deionized water and ethanol, dried, and annealed at 450°C for 3 minutes to obtain a zinc oxide / titanium dioxide nanorod hierarchical structure film;

[0062] (11) Weigh 1.6446 g of cadmium chloride and 0.5481 g of thiourea into a 100 ml beaker, add 30 ml of deionized water, and prepare a 0.24 mol / L cadmium chloride solution and a 0.24 mol / L thiourea solution, respectively. Mix the obtained cadmium chloride and thiourea solutions in a beaker and stir for 30 minutes to obtain a 0.12 mol / L CdS precursor solution.

[0063] (12) Transfer 15 mL of the CdS precursor solution obtained in step (11) to a high-pressure reactor (capacity 50 mL);

[0064] (13) The FTO conductive glass with the hierarchical structured thin film of zinc oxide / titanium dioxide nanorods prepared in step (10) was placed with the conductive surface facing downward, with the angle between the glass and the inner substrate being 60°, in a CdS precursor solution and hydrothermally grown at 160°C for 2 hours to obtain a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode.

[0065] Example 2

[0066] The difference between this embodiment and embodiment 1 is that the hydrothermal reaction temperature in step (13) is 160° C. and the reaction time is 4 h, and the remaining steps are the same as those in embodiment 1.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that the hydrothermal reaction temperature in step (13) is 160° C. and the reaction time is 6 h, and the remaining steps are the same as those in embodiment 1.

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that the hydrothermal reaction temperature in step (13) is 160° C. and the reaction time is 8 h, and the remaining steps are the same as those in embodiment 1.

[0071] Comparative Example 1

[0072] The difference between this embodiment and embodiment 1 is that the TiO2 nanorod film is not processed through steps (5) to (13).

[0073] Comparative Example 2

[0074] The difference between this embodiment and embodiment 1 is that the zinc oxide / titanium dioxide nanorod hierarchical structure film is not processed through steps (11) to (13).

[0075] Comparative Example 3

[0076] The difference between this embodiment and embodiment 1 is that the reaction substrate in step (13) is the conductive glass with TiO2 nanorod film after annealing obtained in step (4), that is, only a single TiO2 is used as the substrate, and CdS is directly hydrothermally compounded without compounding ZnO.

[0077] Effect embodiment

[0078] Figure 2 The XRD patterns of the composite photoanodes prepared in Examples 1-4 show that the intensity of the diffraction peak increases with increasing hydrothermal time. When the hydrothermal time is 6 h, the diffraction peak intensity along (101) of the CdS-sensitized cadmium sulfide / zinc oxide / titanium dioxide composite photoanode is relatively strong. The diffraction peak of CdS can be seen from the X-ray diffraction spectrum, indicating that the CdS quantum dots are uniformly attached to the surface of the zinc oxide / titanium dioxide nanorod hierarchical structure film. Within the hydrothermal time range of 2 to 8 h, the nucleation and growth of the CdS quantum dots are promoted as the hydrothermal reaction time increases.

[0079] Figure 3 This is a scanning electron microscope image of the TiO2 nanorod film prepared in Comparative Example 1. Figure 4 This is a scanning electron microscope image of the zinc oxide / titanium dioxide nanorod hierarchical structure film prepared in comparative example 2. Figure 5 This is a scanning electron microscope image of the cadmium sulfide / titanium dioxide composite photoanode prepared in comparative example 3. Figure 6 is a scanning electron microscope image of the composite photoanode prepared in Example 3. Figure 4 It can be seen that by growing a thin rod-shaped ZnO layer on the surface of the TiO2 nanorod film, under the same hydrothermal reaction conditions (temperature: 160℃, time 6h), Figure 6 Different from Figure 5 CdS composite photoanode on substrate. Figure 3 and Figure 5 It can be seen that under this hydrothermal condition, the CdS crystals have covered the bottom TiO2 substrate; Figure 4 and Figure 6 It can be seen that the density of CdS quantum dots grown on the substrate of ZnO / TiO2 nanorod hierarchical structure film is better, and the substrate is 100% covered, and the complete CdS quantum dots are almost invisible; Figure 5 and Figure 6It can be seen that the CdS quantum dots grown on the TiO2 nanorod film are complete and relatively dense, while the Comparative Example 3 has a small portion of voids in the middle and is less dense than Example 3. This explains why the use of a hierarchical ZnO structure can increase the interfacial area of ​​the array, allowing for the adsorption or deposition of more quantum dots and improving the overall performance of the film.

[0080] Figure 7 The impedance plots for the composite photoanodes prepared in Examples 1-4 show that the impedance value first decreases and then increases with increasing hydrothermal reaction time. The impedance value of the cadmium sulfide / zinc oxide / titanium dioxide composite photoanode obtained after a hydrothermal reaction time of 6 hours, as in Example 3 (i.e., a hydrothermal temperature of 160°C and a hydrothermal time of 6 hours), is the lowest, effectively reducing the resistance to charge transfer and accelerating charge transfer.

[0081] Figure 8 The phase angle frequency diagram of the thin films obtained in comparative example 1 and examples 2 to 4 is shown in FIG. Figure 8 As can be seen, as the hydrothermal reaction time increases, the characteristic peak frequency of the composite photoanode decreases from high to low and then increases again. These peak frequencies are all lower than those of the annealed TiO2 in Comparative Example 1, demonstrating that the composite photoanode effectively improves the performance of pure TiO2. When the hydrothermal reaction time is 6 hours, as in Example 3 (i.e., hydrothermal temperature of 160°C, hydrothermal time: 6 hours), the composite photoanode obtained after the hydrothermal reaction has the lowest characteristic peak frequency, indicating a lower recombination rate and a longer charge carrier lifetime. A longer electron lifetime is associated with a higher short-circuit current density. This increase in electron lifetime can be attributed to passivation of surface states or a weakening of electronic coupling between the photoanode and the electrolyte.

[0082] Figure 9 The transient photocurrent graphs of the films obtained from Examples 1-2 and Examples 1-4 show that the transient photocurrent of the composite photoanode increases first and then decreases with the extension of the hydrothermal reaction time. Among them, the composite photoanode obtained after the hydrothermal reaction of Example 3 (i.e., hydrothermal temperature of 160°C, hydrothermal time: 6h) has the largest transient photocurrent (1.5-2mA / cm 2 ).

[0083] The present invention combines TiO2, which has excellent photoelectric conversion performance, and ZnO, which has excellent mobility properties, as wide-bandgap semiconductor materials. A hydrothermal method is used to grow small, two-dimensional ZnO nanorods on one-dimensional TiO2 nanorods, thereby producing a hierarchical ZnO / TiO2 nanorod film that serves as the substrate for the composite photoanode. The hierarchical ZnO / TiO2 nanorod film creates light absorption and scattering, extending the optical path and improving light absorption efficiency. This increases the interfacial area of ​​the array, allowing for the adsorption or deposition of more photosensitizers, thereby increasing the light absorption capacity of the photoactive layer and improving the photoelectric conversion performance of the cell. Due to the excellent photoelectric conversion performance of TiO2 and the excellent electron mobility and diffusion coefficient of ZnO, the hierarchical structure formed by the two composites offers superior performance compared to single TiO2 and ZnO thin films. ZnO's excellent electron mobility and diffusion coefficient enhance the transport of photogenerated electrons and reduce carrier recombination. Furthermore, the hierarchical structure provides the material with a higher specific surface area, allowing it to absorb more photosensitizers and thus enhance its light absorption capacity. In summary, the ZnO / TiO2 nanorod hierarchical structure film has the above advantages.

[0084] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any equivalent changes or modifications made based on the essence of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode, characterized in that: First, TiO2 is synthesized by a one-step hydrothermal method to form a one-dimensional TiO2 nanorod array film on conductive glass; A ZnO seed layer was then grown on the one-dimensional TiO2 nanorod array film using an immersion method. ZnO nanorods were then hydrothermally grown on the one-dimensional TiO2 nanorod film with the ZnO seed layer, forming a zinc oxide / titanium dioxide nanorod hierarchical structure film. Finally, a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode was prepared by hydrothermal synthesis of CdS quantum dots using cadmium chloride as the cadmium source and thiourea as the sulfur source. The specific steps include: S1. Growing a TiO2 nanorod film on the conductive layer of the conductive glass using a hydrothermal method, immersing the conductive glass with the TiO2 nanorod film in a ZnO sol for 20 to 30 minutes, taking it out and drying it, and then annealing it at a temperature of 400 to 450°C for 30 to 50 minutes, thereby growing a zinc oxide / titanium dioxide nanorod film on the conductive layer of the conductive glass; S2. preparing ZnO precursor solution; S3. The ZnO precursor solution prepared in step S2 is transferred to a reactor, and the conductive glass with the zinc oxide / titanium dioxide nanorod film grown thereon obtained in step S1 is tiltedly placed into the reactor, and hydrothermally grown at 80-100° C. for 2.5-3.5 hours. The film is then rinsed, dried, and annealed, thereby growing a zinc oxide / titanium dioxide nanorod hierarchical structure film on the conductive layer of the conductive glass. S4, preparing a CdS precursor solution; S5. Transfer the CdS precursor solution prepared in step S4 to a reactor, tilt the conductive glass with the zinc oxide / titanium dioxide nanorod hierarchical structure film grown thereon obtained in step S3 into the reactor, hydrothermally grow the film at 120-170° C. for 2-8 hours, remove the film, clean it, and dry it to obtain a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode; In step S1, the specific method for preparing the zinc oxide / titanium dioxide nanorod film is as follows: adding 1.5-2.0 mL of diethanolamine to 50 mL of an ethanol solution of zinc acetate with a concentration of 0.3 mol / L-0.5 mol / L in a warm water bath, and stirring uniformly to obtain a ZnO sol; In step S2, the specific method for preparing the ZnO precursor solution is: adding a hexamethylenetetramine aqueous solution with a concentration of 0.01 mol / L to 0.03 mol / L to an aqueous solution of zinc nitrate with a concentration of 0.01 mol / L to 0.03 mol / L, and stirring uniformly to obtain a ZnO precursor solution; In step S4, the specific method for preparing the CdS precursor solution is: first prepare a 0.16-0.4 mol / L cadmium chloride solution and a 0.16-0.4 mol / L thiourea solution respectively, and then mix the cadmium chloride and thiourea solutions evenly to obtain a 0.08-0.2 mol / L CdS precursor solution.

2. The method for preparing a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode according to claim 1, characterized in that: In step S3, the hydrothermal product is rinsed and dried, and then annealed at a temperature of 400-450° C. for 30-50 minutes.

3. The method for preparing a cadmium sulfide / zinc oxide / titanium dioxide composite photoanode according to claim 1, characterized in that: In step S5, the conductive glass on which the zinc oxide / titanium dioxide nanorod hierarchical structure thin film is grown obtained in step S3 is tilted and placed into a reaction vessel for hydrothermal growth at 160° C. for 6 hours.

4. A cadmium sulfide / zinc oxide / titanium dioxide composite photoanode, characterized in that: The invention is obtained by adopting the preparation method described in any one of claims 1 to 3.

5. Use of the cadmium sulfide / zinc oxide / titanium dioxide composite photoanode according to claim 4 in the fields of dye-sensitized solar cells, photocatalytic degradation of pollutants, and photolysis of water.

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