Composite photoanode and preparation method thereof, photoelectrochemical device

Abstract

The present invention discloses a composite photoanode, comprising: a conductive substrate; a TiO2 nanorod array grown on the conductive substrate; and a support layer deposited on the TiO2 nanorod array; wherein the support layer comprises an amorphous carbon sphere photosensitizer and a cobalt carbonitride cocatalyst. The preparation method thereof is as follows: growing a TiO2 nanorod array on a conductive substrate; preparing an amorphous carbon sphere suspension and a cobalt carbonitride suspension respectively; adding the amorphous carbon sphere suspension to the TiO2 nanorod array and performing a first high-temperature calcination to obtain a TiO2 / CSs photoanode; adding the cobalt carbonitride suspension to the TiO2 / CSs photoanode and performing a second high-temperature calcination to obtain a TiO2 / CSs / Co-CNs composite photoanode. In the present invention, amorphous carbon spheres are used as a photosensitizing layer and cobalt carbonitride is used as a cocatalytic layer to coordinate the effects, thereby improving the carrier separation efficiency of the photoanode, introducing a large number of active sites, and effectively improving the photoelectrocatalytic activity of the composite photoanode.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrochemical devices, in particular to a composite photoanode and a preparation method thereof, and also to a photoelectrochemical device comprising the composite photoanode. Background Art

[0002] Using oxide semiconductor photoelectrochemical (PEC) anodes to convert naturally occurring solar energy into clean energy, such as hydrogen and high-value-added chemicals, is a promising approach to addressing today's energy crisis and environmental pollution. Since its initial use as a photoelectrocatalyst in 1972, TiO2 has been considered one of the most popular PEC anode materials. However, its wide bandgap (approximately 3.0–3.2 eV) results in TiO2 absorbing only ultraviolet light, which accounts for only about 4% of the solar spectrum, preventing the efficient utilization of energy from other wavelengths. Severe surface charge recombination and a scarcity of surface active sites also significantly hinder TiO2 photoelectrocatalytic solar hydrogen production. After 50 years of development, various strategies and solutions have emerged to address these issues. However, overall, the efficiency of photoelectrocatalytic solar energy conversion remains low, significantly limiting its industrial production and application. Therefore, effectively regulating the photoanode bandgap, slowing the carrier recombination rate, and increasing the number of active sites on the photoanode surface to enhance the catalytic activity of photoelectrocatalysts has become a research topic of great interest to researchers worldwide. Summary of the Invention

[0003] In view of the deficiencies in the prior art, the present invention provides a composite photoanode and a preparation method thereof to solve the problem that the existing photoanode has few active sites and low photoelectrocatalytic activity.

[0004] In order to solve the above problems, the present invention first provides a composite photoanode, comprising:

[0005] Conductive substrate;

[0006] TiO2 nanorod arrays grown on a conductive substrate; and,

[0007] A support layer is deposited on the TiO2 nanorod array; wherein the support layer includes an amorphous carbon sphere photosensitizer and a cobalt carbonitride cocatalyst.

[0008] Preferably, the support layer has a thickness of 7 μm to 8 μm.

[0009] Preferably, the diameter of the TiO2 nanorod array is 200nm to 400nm, and the rod height is 3μm to 5μm.

[0010] In order to solve the above technical problems, the present invention also provides a method for preparing the composite photoanode described above, the preparation method comprising the following steps:

[0011] S1, growing TiO2 nanorod arrays on a conductive substrate;

[0012] S2. preparing an amorphous carbon sphere suspension and a cobalt carbonitride suspension respectively;

[0013] S3, adding the amorphous carbon sphere suspension to the TiO2 nanorod array and performing a first high-temperature calcination to obtain a TiO2 / CSs photoanode;

[0014] S4. Add the cobalt carbonitride suspension to the TiO2 / CSs photoanode and perform a second high-temperature calcination to obtain a TiO2 / CSs / Co-CNs composite photoanode.

[0015] Preferably, the solvent of the amorphous carbon sphere suspension is an alcohol solvent, and the concentration of the amorphous carbon sphere suspension is 6M to 10M; the solvent of the cobalt carbonitride suspension is water, and the concentration of the cobalt carbonitride suspension is 1M to 3M.

[0016] Preferably, the process for preparing an amorphous carbon sphere suspension includes: placing a sucrose aqueous solution in a reaction vessel, conducting a hydrothermal reaction at a temperature of 150°C to 200°C for 5h to 6h, separating the reactants after the reaction, drying the reactants to obtain amorphous carbon sphere powder, adding the amorphous carbon sphere powder to an alcohol solvent and stirring and dispersing it to prepare the amorphous carbon sphere suspension.

[0017] Preferably, the process for preparing the cobalt carbonitride suspension includes: dissolving Co(NO3)2·6H2O in formamide to form a reaction solution, placing the reaction solution in a reaction vessel, and conducting a hydrothermal reaction at a temperature of 150°C to 200°C for 15h to 20h. After the reaction is completed, the reactants are separated and dried to obtain cobalt carbonitride powder, and the cobalt carbonitride powder is added to water and stirred to disperse to prepare the cobalt carbonitride suspension.

[0018] Preferably, the temperature of the first high-temperature calcination is 180°C to 220°C, and the temperature of the second high-temperature calcination is 180°C to 250°C.

[0019] Preferably, growing a TiO2 nanorod array on a conductive substrate in step S1 includes: placing a conductive substrate in a mixture of concentrated hydrochloric acid and tetrabutyl titanate solution, subjecting the mixture to a hydrothermal reaction, and subjecting the reacted conductive substrate to a high-temperature calcination treatment to grow a TiO2 nanorod array on the conductive substrate; the temperature of the hydrothermal reaction is 150°C to 200°C, the reaction time is 15h to 20h, the temperature of the high-temperature calcination is 400°C to 600°C, and the calcination time is 2h to 3h.

[0020] The present invention also provides a photoelectrochemical device, which comprises the composite photoanode as described above.

[0021] The present invention provides a composite photoanode and a preparation method thereof. First, a TiO2 nanorod array is grown on a conductive substrate, and an amorphous carbon sphere suspension and a cobalt carbonitride suspension are prepared respectively. The amorphous carbon sphere suspension is added to the TiO2 nanorod array and subjected to high-temperature calcination to obtain a TiO2 / CSs photoanode; the cobalt carbonitride suspension is added to the TiO2 / CSs photoanode and subjected to high-temperature calcination to obtain a TiO2 / CSs / Co-CNs composite photoanode. The TiO2 / CSs / Co-CNs composite photoanode has a supporting layer composed of an amorphous carbon sphere photosensitizer and a cobalt carbonitride co-catalyst. The novel TiO2 / CSs / Co-CNs composite photoanode uses amorphous carbon spheres as a photosensitizer, which serves as the visible light photosensitizing layer and carrier transport layer of the photoanode, and uses cobalt carbonitride as a co-catalyst to provide reaction active sites, thereby promoting the charge separation process and improving the photoresponse current. The preparation method of the TiO2 / CSs / Co-CNs composite photoanode has simple equipment and process, simple operation, green and efficient, low cost, and has broad application prospects in the field of photoelectrocatalysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1a and Figure 1b is a SEM image of the TiO2 nanorod array in Example 1 of the present invention;

[0023] Figure 2 is the XRD pattern of the TiO2 nanorod array in Example 1 of the present invention;

[0024] Figure 3 is the XRD pattern of CSs prepared in Example 1 of the present invention;

[0025] Figure 4 TEM image and FFT diffraction pattern of CSs prepared in Example 1 of the present invention;

[0026] Figure 5 This is the XRD pattern of Co-CNs prepared in Example 1 of the present invention;

[0027] Figure 6 TEM image of Co-CNs prepared in Example 1 of the present invention;

[0028] Figure 7 This is the STEM image of Co-CNs prepared in Example 1 of the present invention;

[0029] Figure 8 This is the XRD pattern of the TiO2 / CSs / Co-CNs composite photoanode prepared in Example 1 of the present invention;

[0030] Figure 9a and Figure 9b This is an SEM image of the TiO2 / CSs / Co-CNs composite photoanode prepared in Example 1 of the present invention;

[0031] Figure 10 These are the photoresponse current JV diagrams of the TiO2 photoanode, TiO2 / CSs composite photoanode and TiO2 / CSs / Co-CNs composite photoanode prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more apparent, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings. Examples of these preferred embodiments are illustrated in the accompanying drawings. The embodiments of the present invention shown in and described with reference to the accompanying drawings are merely exemplary, and the present invention is not limited to these embodiments.

[0033] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show structures and / or processing steps closely related to the solutions according to the present invention, while other details that are not closely related to the present invention are omitted.

[0034] In order to solve the problem of few active sites and low photoelectrocatalytic activity in existing photoanodes, this embodiment first provides a composite photoanode, including: a conductive substrate; a TiO2 nanorod array grown on the conductive substrate; and a support layer deposited on the TiO2 nanorod array; wherein the support layer includes an amorphous carbon sphere photosensitizer and a cobalt carbonitride co-catalyst.

[0035] Specifically, the support layer has a thickness of 7 μm to 8 μm.

[0036] Specifically, the diameter of the TiO2 nanorod array is 200nm to 400nm, and the rod height is 3μm to 5μm.

[0037] In the composite photoanode provided by the above embodiment, the amorphous carbon ball photosensitizer has high light stability, good conductivity, and strong absorption capacity for visible light, which can greatly broaden the light absorption range of a single TiO2 photoanode, and at the same time greatly improve the carrier separation efficiency of the photoanode, thereby promoting its photoelectrocatalytic performance. The cobalt carbonitride cocatalyst further improves the photocurrent density of the composite electrode. When sunlight irradiates the TiO2 photoanode, the photogenerated holes will gradually migrate to the cocatalyst and react with OH groups in water at the surface active sites. - The reaction releases oxygen, and the introduction of a large number of active sites can accelerate the surface reaction process, while reducing carrier recombination and providing photoelectrocatalytic performance.

[0038] The present invention also provides a method for preparing the composite photoanode, which comprises the following steps:

[0039] S1. Growing TiO2 nanorod arrays on a conductive substrate.

[0040] Specifically, the conductive substrate is placed in a mixture of concentrated hydrochloric acid and tetrabutyl titanate solution, the mixture is subjected to a hydrothermal reaction, and the conductive substrate after the reaction is subjected to a high-temperature calcination treatment to grow a TiO2 nanorod array on the conductive substrate.

[0041] The volume ratio of concentrated hydrochloric acid to tetrabutyl titanate solution is 50:1, the temperature of the hydrothermal reaction is 150°C to 200°C, the reaction time is 15h to 20h, the temperature of the high-temperature calcination is 400°C to 600°C, and the calcination time is 2h to 3h.

[0042] Specifically, the density of concentrated hydrochloric acid at 20° C. is 1.18 g / mL, and the content of HCl is 36% to 38%.

[0043] In this embodiment, growing a TiO2 nanorod array on a conductive substrate includes: placing the conductive substrate with the conductive surface facing downward into a reactor lined with polytetrafluoroethylene; stirring 15 mL of deionized water, 15 mL of concentrated hydrochloric acid, and 500 μL of tetrabutyl titanate solution, and adding the mixture to the reactor; performing a hydrothermal reaction at 150°C to 200°C for 15 hours to 20 hours, and then cooling the mixture to room temperature to obtain a conductive substrate after the reaction; rinsing the conductive substrate after the reaction with deionized water, air-drying it, and then placing the substrate in a muffle furnace and calcining it at 400°C to 600°C for 2 hours to 3 hours, and then cooling it to room temperature to obtain a rutile phase TiO2 nanorod array.

[0044] In a preferred embodiment, the conductive substrate is pre-treated FTO glass.

[0045] Specifically, the thickness of the FTO glass substrate is 2.0 mm to 2.2 mm, the light transmittance is above 80%, the square resistance is 6 Ω to 7 Ω, and the thickness of the FTO film layer is 300 nm to 350 nm.

[0046] Specifically, the FTO glass pretreatment method is as follows: cutting the FTO glass substrate into a size of 1 cm×2 cm; immersing the cut FTO glass substrate in a mixed solution of anhydrous ethanol, acetone, deionized water, concentrated sulfuric acid and hydrogen peroxide in sequence for ultrasonic treatment for 10 to 20 minutes, wherein the volume ratio of concentrated sulfuric acid to hydrogen peroxide is 7:3; and then immersing the ultrasonically treated FTO glass substrate in deionized water for 5 to 15 minutes to remove the solvents remaining on the FTO glass substrate during the ultrasonic cleaning process.

[0047] S2. Prepare an amorphous carbon sphere suspension and a cobalt carbonitride suspension respectively.

[0048] Specifically, the amorphous carbon sphere suspension is prepared by placing a sucrose aqueous solution in a reaction vessel, performing a hydrothermal reaction at a temperature of 150°C to 200°C for 5 to 6 hours, separating the reactants after the reaction, drying the reactants to obtain amorphous carbon sphere powder, and adding the amorphous carbon sphere powder to an alcohol solvent and stirring and dispersing the mixture to obtain the amorphous carbon sphere suspension. The alcohol solvent is preferably ethanol.

[0049] Specifically, the preparation process of the cobalt carbonitride suspension is as follows: dissolving Co(NO3)2·6H2O in formamide to form a reaction solution, placing the reaction solution in a reaction vessel, and conducting a hydrothermal reaction at a temperature of 150°C to 200°C for 15h to 20h. After the reaction is completed, the reactants are separated and dried to obtain cobalt carbonitride powder, and the cobalt carbonitride powder is added to water and stirred and dispersed to prepare the cobalt carbonitride suspension.

[0050] More specifically, the preparation of the amorphous carbon sphere suspension is as follows: 0.025 g / mL sucrose aqueous solution is charged into a polytetrafluoroethylene-lined reactor, sealed and subjected to hydrothermal reaction at 150°C to 200°C for 5h to 6h, then cooled to room temperature, centrifuged at 11500r / min for 8.5min, and after precipitation, centrifuged and washed three times with deionized water and ethanol at the same rate and time, dried at 60°C to 80°C to obtain amorphous carbon (CSs) powder, and the amorphous carbon sphere powder is added to ethanol and subjected to hydrothermal reaction to obtain an amorphous carbon sphere suspension.

[0051] More specifically, the cobalt carbonitride suspension is prepared as follows: 0.1 g of Co(NO3)2·6H2O is dissolved in 30 mL of formamide, loaded into a reactor lined with polytetrafluoroethylene, sealed and subjected to a hydrothermal reaction at 150°C to 200°C for 15h to 20h, then cooled to room temperature, centrifuged at 11500 r / min for 8.5 min, and after precipitation, washed three times with deionized water at the same rate and time by centrifugation, dried at 60°C to 80°C to obtain cobalt carbonitride (Co-CNs) powder, and the cobalt carbonitride powder is added to water and subjected to a hydrothermal reaction to obtain a cobalt carbonitride suspension.

[0052] S3. Adding the amorphous carbon sphere suspension onto the TiO2 nanorod array and performing a first high-temperature calcination to obtain a TiO2 / CSs photoanode.

[0053] S4. Add the cobalt carbonitride suspension to the TiO2 / CSs photoanode and perform a second high-temperature calcination to obtain a TiO2 / CSs / Co-CNs composite photoanode.

[0054] In a preferred embodiment, the temperature of the first high-temperature calcination is 180°C to 220°C, and the temperature of the second high-temperature calcination is 180°C to 250°C.

[0055] Specifically, an amorphous carbon ball suspension is added to the surface of the TiO2 nanorod array, dried at room temperature, and calcined at 180°C to 220°C in an air atmosphere to obtain a surface-sensitized TiO2 / CSs photoanode. Then, a cobalt carbonitride suspension is dropped onto the surface of the TiO2 / CSs photoanode, dried at room temperature, and calcined at 180°C to 220°C in an air atmosphere to obtain a new TiO2 / CSs / Co-CNs composite photoanode structure constructed using a photosensitizer and a co-catalyst.

[0056] In a preferred embodiment, the solvent of the amorphous carbon sphere suspension is an alcohol solvent, and the concentration of the amorphous carbon sphere suspension is 6M to 10M; the solvent of the cobalt carbonitride suspension is water, and the concentration of the cobalt carbonitride suspension is 1M to 3M.

[0057] In a more preferred embodiment, the concentration of the ethanol suspension is 6 M, and the concentration of the aqueous suspension is 1 M. The prepared TiO2 / CSs / Co-CNs composite photoanode has better performance.

[0058] The above embodiment provides a method for preparing a composite photoanode, which can prepare a new composite photoanode structure of TiO2 / CSs / Co-CNs with an amorphous carbon ball photosensitizer and a cobalt carbonitride co-catalyst deposited on a TiO2 nanorod array, solving the problem of few active sites and low photoelectrocatalytic activity in existing photoanodes.

[0059] An embodiment of the present invention also provides a photoelectrochemical device, which is, for example, a photoelectrochemical device that uses light irradiation to decompose water to produce hydrogen. The photoelectrochemical device includes a photocathode and a photoanode, wherein the photoanode uses the TiO2 / CSs / Co-CNs composite photoanode provided in an embodiment of the present invention.

[0060] Example 1

[0061] (1) Preparation of TiO2 nanorod arrays

[0062] First, the FTO glass substrate was pretreated, specifically comprising the following steps: the FTO glass substrate was cut into a size of 1 cm × 2 cm using a glass cutter; the cut FTO glass substrate was sequentially immersed in a mixed solution of anhydrous ethanol, acetone, deionized water, concentrated sulfuric acid, and hydrogen peroxide for ultrasonic treatment for 15 minutes, wherein the volume ratio of the concentrated sulfuric acid to hydrogen peroxide was 7:3; and the ultrasonically treated FTO glass substrate was then immersed in deionized water for 10 minutes to remove any solvent residues from the ultrasonic cleaning process.

[0063] Secondly, a TiO2 nanorod array was grown on the pretreated FTO glass substrate, specifically including the following steps: 15 mL of deionized water, 15 mL of concentrated hydrochloric acid and 0.5 mL of tetrabutyl titanate were added to a beaker and stirred at room temperature for 15 minutes to obtain a mixed solution; the pretreated FTO glass substrate was placed with the conductive surface facing down in a high-temperature reactor lined with polytetrafluoroethylene, the prepared mixed solution was added to the lining, and the mixture was hydrothermally reacted at 150°C in an oven for 20 hours and then cooled to room temperature.

[0064] Finally, the reacted FTO glass substrate was taken out from the lining, rinsed with deionized water and dried, and then placed in a muffle furnace and calcined at 500°C for 2 hours. After cooling to room temperature, a rutile phase TiO2 nanorod array was prepared on the FTO glass substrate to form a TiO2 photoanode.

[0065] The prepared TiO2 nanorod arrays were measured by SEM. Figure 1a and Figure 1b is a scanning electron microscope (SEM) image of the TiO2 nanorod array obtained in this embodiment, wherein: Figure 1a This is the top view of the TiO2 nanorod array microstructure. Figure 1b This is a cross-sectional view of the microstructure of TiO2 nanorod array. Figure 1a In the TiO2 array, uniform, square nanorods with a diameter of about 200 to 400 nm can be observed; Figure 1b In the figure, TiO2 nanorods with a height of about 3 μm can also be observed.

[0066] The prepared TiO2 nanorod arrays were subjected to XRD analysis. Figure 2 is the X-ray diffraction (XRD) pattern of the TiO2 nanorod array in this embodiment, as shown in FIG. Figure 2 As shown in the figure, the peaks at 36.1°, 41.2°, 54.3°, 62.7°, 69.0°, and 69.7° in the spectrum correspond to the rutile phase planes (101), (111), (211), (002), (301), and (112), respectively (JCPDS No. 21-1276). The seven asterisks (◆) mark the peaks at 26.4°, 33.7°, 37.8°, 51.5°, 61.6°, 65.6°, and 78.7°, which can be classified as FTO glass substrates. The XRD diffraction pattern confirms that TiO2 nanorod arrays have been prepared and the crystal structure of the TiO2 nanorod arrays has been determined.

[0067] (2) Preparation of amorphous carbon sphere suspension and cobalt carbonitride suspension

[0068] Preparation of amorphous carbon sphere suspension: 0.025 g / mL sucrose aqueous solution was placed in a sealed reactor lined with polytetrafluoroethylene, and hydrothermally reacted at 180°C for 6 hours, then cooled to room temperature and centrifuged at 11500 r / min for 8.5 minutes. After precipitation, it was washed three times with deionized water and ethanol at the same speed and time, and dried at 60°C to obtain amorphous carbon sphere (CSs) powder. The prepared amorphous carbon sphere powder was added to ethanol to prepare a 6M amorphous carbon sphere suspension.

[0069] Preparation of cobalt carbonitride suspension: 0.1 g Co(NO3)2·6H2O was dissolved in 30 ml formamide, loaded into a polytetrafluoroethylene-lined reactor, sealed and hydrothermally reacted at 200°C for 15 hours, then cooled to room temperature and centrifuged at 11500 rpm for 8.5 minutes. After precipitation, it was washed three times with deionized water at the same speed and time, and dried at 60°C to obtain cobalt carbonitride (Co-CNs) powder. The prepared cobalt carbonitride powder was added to water to prepare a 1M cobalt carbonitride suspension.

[0070] The prepared CSs material was subjected to XRD analysis. Figure 3 The XRD pattern of the CSs powder prepared in this example is shown in FIG. Figure 3 As shown in Figure 2, the XRD diffraction pattern confirms the preparation of CSs material and the crystal structure of the CSs powder. A characteristic steamed-bun peak is observed in the 2θ range of 20° to 40°, indicating that CSs is an amorphous material.

[0071] The prepared CSs powder was subjected to TEM measurement, and the TEM image of the obtained CSs powder was as follows: Figure 4The microstructure of CSs powder was determined by fast Fourier transform, and the FFT diffraction pattern was obtained, as shown in Figure 4 The view in the lower right corner. Figure 4 As shown in Figure 3, it can be observed that the CSs powder is a spherical structure with a diameter of about 0.5 μm. The FFT diffraction of the inner area of ​​the CSs powder also shows its amorphous characteristics, which is consistent with the fact reflected by the XRD measurement of the CSs powder.

[0072] The prepared Co-CNs material was subjected to XRD analysis. Figure 5 This is the XRD pattern of the Co-CNs powder prepared in this example. The XRD diffraction pattern can be used to determine that the Co-CNs material has been prepared, and the crystal structure of the Co-CNs material can be determined. The 2θ=27° in the spectrum corresponds to the peak of the classic carbon nitride phase (002), indicating that the Co-CNs material has a layered stacking structure.

[0073] The prepared Co-CNs powder was subjected to TEM analysis. Figure 6 The TEM image of the Co-CNs powder prepared in this example is shown in Figure 2. The microstructure of the Co-CNs was determined by TEM. Figure 7 As shown in Figure 3, it can be observed that Co-CNs are stacked and aggregated sheet structures, which is consistent with the fact reflected by the XRD measurement of Co-CNs.

[0074] Figure 7 The STEM image of the Co-CNs powder prepared in this example is shown in Figure 2. The microstructure of the Co-CNs was determined by SEM. Figure 7 As shown in the STEM image, a whole fuzzy area can be observed, indicating that the Co-CNs material has no obvious crystallization and is a stacked and aggregated lamellar structure. X-ray energy spectrum analysis of the Co-CNs also shows that elements such as N, C, and Co are uniformly distributed in the Co-CNs material.

[0075] (3) Preparation of TiO2 / CSs composite photoanode

[0076] 50 μL of the 6M amorphous carbon sphere suspension prepared in step (2) was dropped onto the surface of the TiO2 nanorod array prepared in step (1), dried at room temperature, sintered at 200°C in a muffle furnace under air atmosphere for 1 h, and cooled to room temperature to obtain a TiO2 / CSs composite photoanode.

[0077] (4) Preparation of TiO2 / CSs / Co-CNs composite photoanode

[0078] 100 μL of the 1M cobalt carbonitride suspension prepared in step (2) was dropped onto the surface of the TiO2 / CSs composite photoanode prepared in step (3), and the mixture was calcined again at 200°C in a muffle furnace under air atmosphere. After cooling, the TiO2 / CSs / Co-CNs composite photoanode was finally obtained.

[0079] The TiO2 / CSs / Co-CNs composite photoanode prepared in this example was subjected to XRD analysis, and the results were as follows: Figure 8 The XRD pattern shown in the figure shows that the TiO2 / CSs / Co-CNs material was prepared and its crystal structure was determined. Since the CSs material is an amorphous structure, the Co-CNs material has a unique characteristic peak at 2θ=27°, which coincides with the characteristic peak of the (110) crystal plane of the FTO glass substrate. Therefore, the XRD characteristic peaks of the TiO2 / CSs / Co-CNs composite photoanode are consistent with the Figure 2 The XRD characteristic peaks of the rutile TiO2 nanorod arrays overlap, which also shows that the three materials are combined in the form of physical contact and no chemical changes occur between them.

[0080] The microstructure of TiO2 / CSs / Co-CNs composite photoanode was determined by SEM. Figure 9a and Figure 9b 9a is a top view of the microstructure of TiO2 / CSs / Co-CNs. Figure 9b The cross-sectional view of the microstructure of TiO2 / CSs / Co-CNs. Figure 9a and Figure 9b Aggregated flaky Co-CNs were observed flattened on the surface of the CSs layer and interspersed within the interstices of the CSs layer. The entire supported layer was approximately 7 to 8 μm thick. The close contact between the CSs layer and the Co-CNs facilitated carrier transport and the catalytic reaction, further promoting charge separation and enhancing the photoelectrocatalytic activity of the composite photoanode.

[0081] Photoelectrochemical tests were performed on the TiO2 photoanode obtained in step (1), the TiO2 / CSs composite photoanode obtained in step (3), and the TiO2 / CSs / Co-CNs composite photoanode obtained in step (4) in Example 1 above. Specifically, the photoelectrochemical tests involved:

[0082] (1) All photoelectrochemical measurements were performed using a CHI660e potentiostat in a typical three-electrode cell at room temperature, with the photoanode (the TiO2 / CSs / Co-CNs composite photoanode prepared above) as the working electrode, Pt foil as the counter electrode, and Ag / AgCl as the reference electrode.

[0083] (2) The prepared TiO2 / CSs / Co-CNs composite photoanode was inserted into the electrolyte with a test area of ​​1 cm×1 cm. The electrolyte was 0.05 M Na2SO4 solution with a pH of 5.6.

[0084] (3) Photoelectrochemical measurements were performed under 1 s of simulated sunlight using a peccell PEC-L01 solar simulator equipped with a 100 W xenon arc lamp and an AM 1.5 filter.

[0085] (4) For photocurrent measurement, linear sweep voltammetry (LSV) was used with a scan rate of 0.05 V / s.

[0086] (5) According to the Nernst equation (E RHE =E Ag / AgCl +0.0591pH+E 0 Ag / Cl ), the measured potential of the Ag / AgCl electrode (saturated KCl solution) is converted into the potential of the reversible hydrogen electrode (V RHE ) potential. Then, according to the test results, a JV curve is drawn, such as Figure 10 shown.

[0087] from Figure 10 As shown in the JV curve, the photocurrent of the TiO2 / CSs / Co-CNs composite photoanode is about 1.73 mA / cm at 1.23 V. 2 (1.23vs RHE), which is 3.8 times that of pure TiO2 photoanode, showing excellent PEC performance, confirming the effective role of CSs materials and Co-CNs materials in improving the solar light conversion process.

[0088] In summary, the embodiments of the present invention provide a composite photoanode, which uses amorphous carbon spheres as photosensitizers, as the visible light photosensitive layer and carrier transport layer of the photoanode, greatly broadens the light absorption range of the TiO2 nanorod array, improves the carrier separation efficiency of the photoanode, promotes the photoelectrocatalytic performance, and uses cobalt carbonitride as a co-catalyst to provide reaction active sites, promotes the charge separation process, increases the light response current, and improves the photoelectrocatalytic water decomposition performance of the photoanode. At the same time, the preparation method of the composite photoanode has simple equipment and process, simple operation, green and efficient, low cost, and has broad application prospects in the field of photoelectrocatalysis.

[0089] The above is only a specific implementation method of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for preparing a composite photoanode, characterized in that: The preparation method comprises the following steps: S1, growing TiO2 nanorod arrays on a conductive substrate; S2. preparing an amorphous carbon sphere suspension and a cobalt carbonitride suspension respectively; S3, adding the amorphous carbon sphere suspension to the TiO2 nanorod array and performing a first high-temperature calcination to obtain a TiO2 / CSs photoanode; S4, adding the cobalt carbonitride suspension to the TiO2 / CSs photoanode and performing a second high-temperature calcination to obtain a TiO2 / CSs / Co-CNs composite photoanode; Among them, in step S2, the preparation method of the amorphous carbon sphere suspension includes: charging a 0.025 g / mL sucrose aqueous solution into a polytetrafluoroethylene-lined reactor, sealing it, and hydrothermally reacting it at 180°C for 6 hours, cooling it to room temperature, centrifuging it at 11500 r / min for 8.5 minutes, and after precipitation, centrifuging it three times with deionized water and ethanol at the same speed and time, drying it at 60°C to obtain amorphous carbon sphere powder, and adding the prepared amorphous carbon sphere powder to ethanol to prepare a 6M amorphous carbon sphere suspension; Wherein, in step S2, the preparation method of the cobalt carbonitride suspension includes: dissolving 0.1g Co(NO3)2·6H2O in 30ml formamide, loading into a polytetrafluoroethylene-lined reactor, sealing and hydrothermally reacting at 200°C for 15h, cooling to room temperature, centrifuging at 11500r / min for 8.5min, and washing three times with deionized water at the same speed and time after precipitation, drying at 60°C to obtain cobalt carbonitride powder, and adding the prepared cobalt carbonitride powder to water to prepare a 1M cobalt carbonitride suspension; Step S3 specifically comprises: dropping 50 μL of the 6M amorphous carbon sphere suspension prepared in step S2 on the surface of the TiO2 nanorod array prepared in step S1, drying at room temperature, sintering at 200°C in a muffle furnace under air atmosphere for 1 hour, and cooling to room temperature to obtain a TiO2 / CSs composite photoanode; Among them, step S4 specifically includes: selecting 100 μL of the 1M cobalt carbonitride suspension prepared in step S2 and dropping it on the surface of the TiO2 / CSs composite photoanode prepared in step S3, calcining it again at 200°C in a muffle furnace under air atmosphere, and finally obtaining the TiO2 / CSs / Co-CNs composite photoanode after cooling.

2. The method for preparing a composite photoanode according to claim 1, wherein: The method of growing a TiO2 nanorod array on a conductive substrate includes: placing the conductive substrate in a mixture of concentrated hydrochloric acid and tetrabutyl titanate solution, subjecting the mixture to a hydrothermal reaction, and subjecting the conductive substrate after the reaction to a high-temperature calcination treatment to grow the TiO2 nanorod array on the conductive substrate; wherein the temperature of the hydrothermal reaction is 150°C to 200°C, and the reaction time is 15h to 20h; the temperature of the high-temperature calcination is 400°C to 600°C, and the calcination time is 2h to 3h.

3. A photoelectrochemical device, characterized in that The invention comprises a composite photoanode prepared by the preparation method of the composite photoanode according to claim 1 or 2.

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