A photoanode device for realizing carrier multiplication and a manufacturing method thereof

Abstract

The application discloses a photoanode device for realizing carrier multiplication and a manufacturing method thereof, which comprises an FTO substrate, a BiVO4 film layer, a CdS catalytic layer and a MoS2 auxiliary catalytic layer from bottom to top; the manufacturing method comprises the following steps: (1) washing the FTO substrate and then blowing dry for standby; (2) electrodepositing a BiOI film on the FTO substrate, then dropping and coating a V source precursor solution, and annealing to form a BiVO4 film; (3) water-bath depositing a CdS catalytic layer on the BiVO4 film; (4) placing the FTO substrate treated in the step (3) in an electrolyte, and performing open-closed light LSV test to activate the CdS catalytic layer; (5) blowing dry the activated CdS catalytic layer with nitrogen for standby, and photoelectrodepositing a MoS2 auxiliary catalytic layer on the CdS catalytic layer. The application can improve the photocurrent density and break through the original photoenergy-hydrogen energy conversion efficiency.

Description

Technical Field

[0001] This invention relates to the field of photoelectrochemical technology, and in particular to a photoelectric anode device that achieves carrier multiplication and its manufacturing method. Background Technology

[0002] Among the many emerging hydrogen production technologies, photoelectrochemical water splitting technology has been established as a highly feasible and environmentally sustainable green hydrogen production method by utilizing solar energy to achieve efficient water splitting for hydrogen production.

[0003] In metal-oxide-semiconductor systems, BiVO4 has become a promising photoanode material due to its relatively narrow band gap and conduction band position close to the thermodynamic hydrogen evolution potential. However, some inherent problems still exist that require further investigation and resolution. Therefore, exploring various strategies to improve its light absorption efficiency, charge transfer efficiency, and overall photoelectrochemical water splitting performance to address these limitations is highly significant. Summary of the Invention

[0004] To address the aforementioned problems in existing technologies, this invention provides a photoelectric anode device for achieving carrier multiplication and its manufacturing method. This invention selects electrodeposition, water bath deposition, and photoelectrode deposition methods to grow the co-catalyst, while simultaneously altering the morphology of the surface material through activation, significantly increasing its photocurrent density and breaking through the previous limitations in photo-hydrogen energy conversion efficiency.

[0005] The technical solution of the present invention is as follows:

[0006] The first objective of this invention is to provide a photoelectric anode device that achieves carrier multiplication, comprising, from bottom to top, an FTO substrate, a BiVO4 thin film layer, a CdS catalytic layer, and a MoS2 co-catalytic layer;

[0007] The BiVO4 thin film layer has a porous granular structure;

[0008] The CdS catalyst layer is uniformly attached to the BiVO4 thin film layer in the form of serrated particles;

[0009] The MoS2 co-catalytic layer has a porous honeycomb structure.

[0010] In one embodiment of the present invention, the thickness of the BiVO4 thin film layer is 450-550 nm; the thickness of the CdS catalyst layer is 150-250 nm; and the thickness of the MoS2 co-catalyst layer is 50-150 nm.

[0011] The second objective of this invention is to provide a method for manufacturing the photoanode device that achieves carrier multiplication, specifically comprising the following steps:

[0012] (1) After cleaning the FTO substrate, dry it with nitrogen gas for later use;

[0013] (2) A BiOI film was electrodeposited on an FTO substrate, followed by drop-coating of a V source precursor solution and annealing to form a BiVO4 film.

[0014] (3) CdS was deposited on the BiVO4 film in a water bath. After deposition, the film was rinsed and dried, and then annealed at 400-450℃ for 1-2 hours to form a CdS catalyst layer on the BiVO4 film.

[0015] (4) Place the FTO substrate treated in step (3) in the electrolyte and perform on-off LSV test to activate the CdS catalyst layer.

[0016] (5) The activated CdS catalyst layer is dried with nitrogen and set aside for later use. A MoS2 co-catalyst layer is formed by photoelectrodeposition on the CdS catalyst layer.

[0017] In one embodiment of the present invention, the CdS catalyst layer and the BiVO4 thin film layer can form a heterojunction structure, thereby playing a key role in the photoelectrocatalytic water splitting process. After activation treatment, the surface structure of the CdS catalyst layer is transformed into a nanosheet-like structure. This structural transformation significantly improves the separation efficiency and transport capability of photogenerated carriers, resulting in a substantial increase in photocurrent density, far exceeding its theoretical maximum value, and achieving an incident photon-to-current conversion efficiency (IPCE) exceeding 100%. The MoS2 co-catalyst layer exhibits a porous honeycomb structure, with its nanosheet morphology becoming more pronounced.

[0018] In one embodiment of the present invention, in step (1), the cleaning method is as follows: ultrasonic cleaning with acetone, isopropanol and pure water for 5 to 10 minutes each.

[0019] In one embodiment of the present invention, in step (2), the method for electrodepositing BiOI thin film is as follows: using Bi source precursor solution as electrolyte, platinum electrode as counter electrode, Ag / AgCl as reference electrode, applying a voltage of -0.6 to -0.2V (vs Ag / AgCl), electrodepositing for 200 to 300s, and forming BiOI thin film on FTO substrate.

[0020] In one embodiment of the present invention, in step (2), the Bi source precursor solution is prepared by mixing Bi(NO3)3·5H2O, deionized water, and ethylene glycol; wherein the mass-to-volume ratio of Bi(NO3)3·5H2O to deionized water is 5-10:1 mg / mL, the volume ratio of ethylene glycol to water is 2-2.5:1, and the purity of ethylene glycol is 99.5%.

[0021] In one embodiment of the present invention, in step (2), the V source precursor solution is a VO(acac)2 solution prepared by dissolving VO(acac)2 in DMSO; wherein the mass-volume ratio of VO(acac)2 to DMSO is 5-6:1 mg / mL; and the annealing conditions are annealing at 450-500°C for 2-3 hours.

[0022] In one embodiment of the present invention, in step (3), the method of water bath deposition of CdS is as follows: the FTO substrate with the BiVO4 film already deposited is completely immersed in the deposition solution A, and the water bath temperature is set to 70-85°C for deposition for 1-1.5 hours.

[0023] In one embodiment of the present invention, the deposition solution A is prepared by mixing CdSO4, thiourea, ammonia, and deionized water, wherein the mass-to-volume ratio of CdSO4 to water is 0.3–1:1 mg / mL, the mass-to-volume ratio of thiourea to water is 7–8:1 mg / mL, and the volume ratio of ammonia to deionized water is 1:18; the purity of the ammonia is 25–28%. In one embodiment of the present invention, in step (4), the electrolyte is a NaOH-methanol aqueous solution, wherein the mass-to-volume ratio of NaOH to water is 20–25:1 mg / mL; the volume ratio of (AR, 99.7%) methanol to water is 1:45; and the voltage for the on / off LSV test is -0.5V to 0.5V.

[0024] In one embodiment of the present invention, in step (5), the electrolyte used for photoelectrodeposition is prepared by mixing (NH4)2MoS4 and deionized water, wherein the mass-to-volume ratio of (NH4)2MoS4 to deionized water is 0.3 to 0.5:1 mg / mL.

[0025] In one embodiment of the present invention, during the photoelectrode deposition process, an application of 100 mW / cm 2 Simulated sunlight with AM1.5G intensity, with an applied bias voltage of -0.5 to -0.7V, forms a MoS2 co-catalytic layer through photoelectrochemical deposition over 600 to 800 seconds.

[0026] The beneficial technical effects of this invention are as follows:

[0027] (1) After successfully depositing a CdS layer on the surface of BiVO4 in a water bath, a heterojunction structure was formed between BiVO4 and CdS. The formation of this heterojunction significantly enhanced the separation efficiency and transmission capability of photogenerated carriers, resulting in a significant increase in photocurrent density.

[0028] (2) After performing overall activation of the photoanode, the turn-on voltage was negatively shifted from 0.3V (vs. RHE) to 0.1V (vs. RHE). The saturation photocurrent density of the photoanode reached approximately 8 mA / cm². 2The saturation photocurrent density far exceeds the theoretical maximum value of BiVO4 (7.5 mA / cm²). 2 The activation operation not only effectively reduces the turn-on voltage but also significantly increases the photocurrent density under high bias voltage, making its performance far exceed the theoretical limit of BiVO4.

[0029] (3) In this invention, after constructing a MoS2 layer on the surface of the photoanode by photoelectrodeposition, the photocurrent density in the low voltage region is increased by about 2.3 times compared with the case without the MoS2 layer, and the anode turn-on voltage also undergoes a significant negative shift, decreasing to -0.2V (vs. RHE). The deposition of the MoS2 layer not only optimizes the surface electrical properties of the photoanode, but also reduces the onset response potential of photogenerated carriers, enabling the photoanode to initiate the photoelectrochemical reaction at a lower applied voltage.

[0030] (4) The present invention has been systematically tested for incident photon to current conversion efficiency (IPCE) of the photoanode. The photoelectric device developed in this invention exhibits excellent performance in an alkaline electrolyte solution containing methanol, with a conversion efficiency exceeding 100%. Attached Figure Description

[0031] Figure 1 This is a frontal scanning electron microscope image of BiVO4 in Example 1;

[0032] Figure 2 This is a front-side scanning electron microscope image of BiVO4 / CdS in Example 1;

[0033] Figure 3 This is a frontal scanning electron microscope image of BiVO4 / CdS (activated) in Example 1;

[0034] Figure 4 This is a front scanning electron microscope image of BiVO4 / CdS(activated) / MoS2 in Example 1;

[0035] Figure 5 This is a linear sweep voltammetry curve of the series of electrodes in Example 1;

[0036] Figure 6 This is a graph showing the incident photon to current conversion efficiency of the series of electrodes in Example 1;

[0037] Figure 7 This is a diagram of the photoelectrochemical water splitting for hydrogen and oxygen production by BiVO4 / CdS (activated) in Example 1.

[0038] Figure 8 The linear sweep voltammetry curves of the series of electrodes in Comparative Example 1 are shown.

[0039] Figure 9 Linear sweep voltammetry curves of the series of electrodes in Comparative Example 2; Detailed Implementation

[0040] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0041] This embodiment provides a method for manufacturing a photoanode device that achieves carrier multiplication, which is also a composite structure photoanode device for photoelectrochemical water splitting. First, a BiVO4 thin film is deposited on the surface of an FTO conductive glass substrate using electrodeposition technology. Then, CdS is deposited on the BiVO4 thin film using a water bath deposition method to construct a BiVO4 / CdS heterojunction layer structure. Next, the BiVO4 / CdS heterojunction structure is activated by on / off light treatment. Finally, MoS2 is further deposited on the activated BiVO4 / CdS photoanode surface using photoelectrochemical deposition. Through the above multi-step process, a photoanode device with a composite structure, namely a BiVO4 / CdS (activated) / MoS2 composite electrode, is successfully fabricated, enabling carrier multiplication for efficient photoelectrochemical hydrogen production applications.

[0042] Example 1

[0043] A photoelectric anode device for achieving carrier multiplication comprises, from bottom to top, an FTO substrate, a BiVO4 thin film layer, a CdS catalytic layer, and a MoS2 co-catalytic layer; the BiVO4 thin film layer has a porous granular structure; the CdS catalytic layer is uniformly attached to the BiVO4 thin film layer in the form of serrated particles; and the MoS2 co-catalytic layer has a porous honeycomb structure.

[0044] Its manufacturing method includes the following steps:

[0045] (1) FTO was ultrasonically cleaned with acetone, isopropanol and pure water for 5 minutes each, and then dried with nitrogen gas for later use.

[0046] (2) 0.087 g Bi(NO3)3·5H2O and 20 mL ethylene glycol (AR, 99.5%) were dissolved in 10 mL deionized water to form a Bi source precursor solution. BiOI thin film was prepared by electrodeposition on FTO substrate for 200 s at a voltage of -0.2 V vs Ag / AgCl.

[0047] Next, 0.0265 g of VO(acac)2 was mixed with 5 mL of DMSO to form a V source precursor solution, which was then drop-coated onto the surface of the BiOI film and annealed at 450 °C for 2 h to obtain a BiVO4 film. Finally, the film was immersed in 1 M NaOH solution for 30 min to remove excess V2O5.

[0048] (3) Add 0.057g CdSO4, 1.3418g thiourea and 10mL ammonia (AR, 28%) to 180mL deionized water to prepare deposition solution A. Immerse the FTO substrate with the BiVO4 film completely in deposition solution A and set the water bath temperature to 80℃ for 1h. After deposition, rinse and dry, and then anneal at 400℃ for 1h to form a CdS catalyst layer on the BiVO4 film.

[0049] (4) Prepare an electrolyte by mixing 1.0 g NaOH, 1 mL methanol (AR, 99.7%) and 45 mL water. Place the FTO substrate treated in step (3) into the electrolyte and perform an on / off LSV test with a voltage range of -0.5 V to 0.5 V to complete the CdS activation.

[0050] (5) Dissolve 0.0104 g of (NH4)2MoS4 in 30 mL of deionized water to prepare an aqueous solution of (NH4)2MoS4. Then, photoelectrodeposit a MoS2 co-catalyst layer on the CdS catalyst layer to finally obtain the photoanode, abbreviated as BiVO4 / CdS(activated) / MoS2 photoanode. During the photoelectrode deposition process, an application of 100 mW / cm² is used. 2 Simulated sunlight with AM 1.5G standard intensity, external bias voltage -0.5V, photoelectrodeposition for 800s.

[0051] In the preparation of the BiVO4 / CdS(activated) / MoS2 photoanode, this invention performed scanning electron microscopy (SEM) analysis on the photoelectrodes prepared at each stage, including BiVO4, BiVO4 / CdS, BiVO4 / CdS(activated), and the final BiVO4 / CdS(activated) / MoS2, to observe their microstructure and structural characteristics. Specifically, the SEM image of BiVO4 is shown below. Figure 1 As shown, the SEM image of the BiVO4 / CdS photoelectrode is as follows: Figure 2 As shown in the figure, the SEM image of the BiVO4 / CdS photoelectrode after activation treatment is as follows: Figure 3 As shown, the final SEM image of the BiVO4 / CdS(activated) / MoS2 composite photoelectrode is as follows. Figure 4 As shown.

[0052] Depend on Figure 1 It can be seen that the BiVO4 photoelectrode exhibits a granular structure and forms a porous morphology overall.

[0053] Depend on Figure 2 As can be seen from the BiVO4 / CdS photoelectrode, CdS is tightly attached to the surface of BiVO4, and the overall particles exhibit a serrated appearance.

[0054] Depend on Figure 3It can be seen that the activated BiVO4 / CdS photoelectrode has a quantum nanosheet structure generated on its surface.

[0055] Depend on Figure 4 It can be seen that after MoS2 deposition, it also coats the surface of BiVO4 / CdS, and the hexagonal structure of the quantum nanosheets becomes clearer and more defined.

[0056] This invention focuses on the BiVO4 / CdS(activated) / MoS2 series photoanodes, and conducts linear sweep voltammetry tests in a mixed solution of NaOH and methanol. Figure 5 Incident photon to current conversion efficiency test Figure 6 );

[0057] Depend on Figure 5 It can be seen that, among the comparisons of electrodes with different structures, BiVO4 exhibits the worst photoelectric performance, with a photocurrent density of only 1.6 mA / cm² at 1.8 V (vs. RHE). 2 This result indicates that BiVO4 alone, when used as a photoanode material, exhibits low photoelectrochemical activity, making it insufficient to meet the requirements for efficient photocatalytic hydrogen production. By depositing a CdS layer on the BiVO4 substrate via a water bath, the performance of the photoanode was significantly improved. This result demonstrates that the introduction of the CdS layer effectively promotes the separation and transport of photogenerated carriers, thereby enhancing the photoelectrochemical activity of the photoanode. Its turn-on voltage shifted negatively from 0.3V (vs. RHE) to 0.1V (vs. RHE), and the increase in photocurrent density was particularly significant at high bias voltages, with the saturation photocurrent density reaching approximately 8 mA / cm². 2 The saturation photocurrent density is twice that of the unactivated operation. This result not only demonstrates that activation treatment can significantly improve the photoelectrochemical performance of the photoanode, but also that its saturation photocurrent density even exceeds the theoretical maximum value of BiVO4 (7.5 mA / cm²). 2 To further improve the turn-on potential, a MoS2 co-catalyst layer was added to the photoanode. At this point, a negative shift in the turn-on voltage to -0.1V (vs. RHE) was observed, and simultaneously, the photocurrent density increased by approximately 2.3 times at the low voltage. This invention successfully increased the photocurrent density of the photoanode to above its theoretical maximum value and significantly reduced the turn-on voltage, resulting in a substantial improvement in its overall photoelectrochemical performance.

[0058] from Figure 6The test results clearly show that after CdS layer deposition and subsequent activation treatment, the incident photon-to-current conversion efficiency (IPCE) of the BiVO4 / CdS (activated) photoanode is significantly improved, exceeding 100%. This phenomenon reveals a key physical process: under photoexcitation conditions, the number of electrons generated by the photoanode is not only comparable to, but even exceeds, the number of photons absorbed. This process significantly enhances the separation and transport efficiency of photogenerated carriers, thereby greatly improving photoelectrochemical performance. Furthermore, when a MoS2 layer is deposited on the surface of the BiVO4 / CdS (activated) photoanode, its IPCE value remains above 100%. This result further verifies the significant improvement in photoelectrochemical performance brought about by the introduction of the MoS2 cocatalyst layer, achieving higher photoelectric conversion efficiency. This provides new ideas and directions for the design and optimization of photoanode materials, namely, by rationally designing the catalyst layer structure, the photon-to-current conversion efficiency can be effectively improved, thereby achieving efficient photoelectrochemical energy conversion.

[0059] Figure 7 The actual hydrogen and oxygen production collected during the photoanode BiVO4 / CdS (activation) test was shown by gas chromatography analysis. The observed hydrogen to oxygen molar ratio was significantly higher than the ideal stoichiometric ratio of 2:1 under water redox conditions alone. This deviation indicates that other oxidation reactions occurred at the photoanode in addition to water oxidation. This observation not only verifies the photocurrent enhancement effect brought about by the electrolyte but also demonstrates that this effect significantly improves the efficiency of hydrogen production from water splitting at the photocathode.

[0060] Example 2

[0061] Same as Example 1, except that the applied voltage for preparing the BiVO4 thin film layer is different in the manufacturing method. The specific steps are as follows:

[0062] 0.087 g Bi(NO3)3·5H2O was dissolved in 20 mL of ethylene glycol (AR, 99.5%) in 10 mL of deionized water to form a Bi source precursor solution. BiOI thin films were prepared by electrodeposition on an FTO substrate for 200 s at a voltage of -0.4 V vs Ag / AgCl.

[0063] Next, 0.0265 g of VO(acac)2 was mixed with 5 mL of DMSO to form a V source precursor solution, which was then drop-coated onto the surface of the BiOI film and annealed at 450 °C for 2 h to obtain a BiVO4 film. Finally, the film was immersed in 1 M NaOH solution for 30 min to remove excess V2O5.

[0064] Example 3

[0065] Same as Example 1, except that the water bath time for preparing the CdS catalyst layer is different. The specific steps are as follows:

[0066] 0.057 g CdSO4, 1.3418 g thiourea and 10 mL ammonia (AR, 28%) were added to 180 mL deionized water to prepare deposition solution A. The FTO substrate with the BiVO4 film already deposited was completely immersed in deposition solution A and the water bath temperature was set to 70 °C for 1 h. After deposition, the substrate was rinsed and dried, and then annealed at 400 °C for 1 h to form a CdS catalyst layer on the BiVO4 film.

[0067] Comparative Example 1

[0068] Same as Example 1, except that, from bottom to top, the layers are FTO substrate, BiVO4 thin film layer, and MoS2 co-catalyst layer.

[0069] Electrode LSV test results are as follows Figure 8 As shown in the figure. The results indicate that removing the CdS layer from the original number of layers does not change the photoelectric performance of BiVO4 itself; the carrier multiplication effect does not occur when the CdS layer is missing. This fully demonstrates that carrier multiplication is the core and key to the efficient energy conversion of this system.

[0070] Comparative Example 2

[0071] Same as Example 1, except that, from bottom to top, the layers are FTO substrate and CdS catalyst layer.

[0072] Electrode LSV test results are as follows Figure 9 As shown in the figure. The results indicate that removing the BiVO4 thin film layer from the original layer results in lower photoelectric performance than including the BiVO4 thin film layer; the absence of the BiVO4 thin film layer leads to the lack of a light-absorbing host, thus reducing photoelectric performance. This fully demonstrates the importance of the BiVO4 absorber and its excellent ability to form a heterojunction with the CdS layer. The presence of the BiVO4 layer also lays the foundation for the carrier multiplication effect.

[0073] In summary, analysis of the linear sweep voltammetry curves, incident photon-to-current conversion efficiency curves, and gas chromatograms of all examples reveals that this invention, for the first time, combines BiVO4 with a CdS layer and introduces a mixed solution of NaOH and methanol electrolytes. Utilizing the activation effect of CdS, the photocurrent density of the photoanode is significantly increased, exceeding the maximum theoretical value. Furthermore, this invention further introduces the co-catalyst MoS2, resulting in a more negative turn-on voltage for the photoanode. This leads to excellent overall photoelectrochemical performance of the photoanode.

[0074] The photoanode designed in this invention, after incorporating different catalytic layers, has innovatively improved the photon-to-current conversion efficiency.

[0075] The photoanode developed in this invention exhibits superior performance in the photoelectrochemical water splitting process for hydrogen production, successfully breaking through the theoretical limit of traditional light-to-hydrogen energy conversion efficiency. This innovative achievement not only brings groundbreaking progress to the field of new energy, but also provides valuable new ideas and directions for the future development of efficient photocatalytic hydrogen production technology, and is expected to promote the widespread application and further development of related technologies in practical applications.

[0076] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A photoelectric anode device for realizing carrier multiplication, characterized in that, From bottom to top, the layers are: FTO substrate, BiVO4 thin film layer, CdS catalyst layer, and MoS2 co-catalyst layer. The BiVO4 thin film layer has a porous granular structure; The CdS catalytic layer is attached to the BiVO4 thin film layer in the form of quantum nanosheets; The MoS2 co-catalyst layer has a porous honeycomb structure; Its manufacturing method includes the following steps: (1) After cleaning the FTO substrate, dry it with nitrogen gas for later use; (2) A BiOI film was electrodeposited on an FTO substrate, followed by drop-coating of a V source precursor solution and annealing to form a BiVO4 film; (3) CdS was deposited on the BiVO4 film in a water bath. After deposition, the film was rinsed and dried, and then annealed at 400~450℃ for 1~2h to form a CdS catalyst layer on the BiVO4 film. (4) Place the FTO substrate treated in step (3) in the electrolyte and perform on-off LSV test to activate the CdS catalyst layer; The electrolyte is a NaOH-methanol aqueous solution, wherein the mass-to-volume ratio of NaOH to water is 20~25:1 mg / mL; the volume ratio of methanol to water is 1:45; the voltage for the on / off LSV test is -0.5V to 0.5V.

2. A method for manufacturing a photoanode device for carrier multiplication as described in claim 1, characterized in that, Includes the following steps: (1) After cleaning the FTO substrate, dry it with nitrogen gas for later use; (2) A BiOI film was electrodeposited on an FTO substrate, followed by drop-coating of a V source precursor solution and annealing to form a BiVO4 film; (3) CdS was deposited on the BiVO4 film in a water bath. After deposition, the film was rinsed and dried, and then annealed at 400~450℃ for 1~2h to form a CdS catalyst layer on the BiVO4 film. (4) Place the FTO substrate treated in step (3) in the electrolyte and perform on-off LSV test to activate the CdS catalyst layer; The electrolyte is a NaOH-methanol aqueous solution, wherein the mass-to-volume ratio of NaOH to water is 20~25:1 mg / mL; the volume ratio of methanol to water is 1:45; the voltage for the on / off LSV test is -0.5V to 0.5V. (5) The activated CdS catalyst layer is dried with nitrogen and set aside for later use. A MoS2 co-catalyst layer is formed by photoelectrodeposition on the CdS catalyst layer.

3. The manufacturing method according to claim 2, characterized in that, In step (1), the cleaning method is to use acetone, isopropanol and pure water for ultrasonic cleaning for 5-10 minutes each.

4. The manufacturing method according to claim 2, characterized in that, In step (2), the method for electrodepositing BiOI thin film is as follows: using Bi source precursor solution as electrolyte, platinum electrode as counter electrode, Ag / AgCl as reference electrode, applying a voltage of -0.6~-0.2V, electrodepositing for 200~300s, and forming BiOI thin film on FTO substrate.

5. The manufacturing method according to claim 2, characterized in that, In step (2), the Bi source precursor solution is prepared by mixing Bi(NO3)3·5H2O, deionized water and ethylene glycol; wherein the mass-volume ratio of Bi(NO3)3·5H2O to deionized water is 5~10:1 mg / mL, the volume ratio of ethylene glycol to water is 2~2.5:1, and the purity of ethylene glycol is 99.5%.

6. The manufacturing method according to claim 2, characterized in that, In step (2), the V source precursor solution is a VO(acac)2 solution prepared by dissolving VO(acac)2 in DMSO; wherein the mass-volume ratio of VO(acac)2 to DMSO is 5~6:1 mg / mL; and the annealing conditions are annealing at 450~500℃ for 2~3h.

7. The manufacturing method according to claim 2, characterized in that, In step (3), the method for water bath deposition of CdS is as follows: the FTO substrate with the BiVO4 film already deposited is completely immersed in the deposition solution A, and the water bath temperature is set to 70~85℃ for 1~1.5h. Sediment A was prepared by mixing CdSO4, thiourea, ammonia and deionized water, wherein the mass-to-volume ratio of CdSO4 to water was 0.3~1:1 mg / mL, the mass-to-volume ratio of thiourea to water was 7~8:1 mg / mL, and the volume ratio of ammonia to deionized water was 1:18; the purity of ammonia was 25~28%.

8. The manufacturing method according to claim 2, characterized in that, In step (5), the electrolyte used for photoelectrodeposition is prepared by mixing (NH4)2MoS4 with deionized water, wherein the mass-volume ratio of (NH4)2MoS4 to deionized water is 0.3~0.5:1 mg / mL.

9. The manufacturing method according to claim 8, characterized in that, During photoelectrode deposition, an application of 100 mW / cm 2 Simulated sunlight with AM 1.5G intensity, with an applied bias voltage of -0.5 to -0.7V, is used for photoelectrochemical deposition for 600 to 800 seconds to form a MoS2 co-catalytic layer.

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