A sulfur-indium-zinc containing sulfur defect and tungsten oxide composite S-type heterojunction photocatalyst, a preparation method and application thereof

Abstract

This invention discloses an S-type heterojunction photocatalyst composed of sulfur-defect-containing indium zinc sulfide and tungsten oxide, its preparation method, and its application. Specifically, this invention involves preparing WO3 nanosheets via a hydrothermal method, then loading them onto the surface of Zn3In2S6 using a solvothermal method, followed by introducing sulfur defects through phototreatment to obtain the S-type heterojunction photocatalyst WO3 / V. S -Zn3In2S6. The S-type heterojunction photocatalyst WO3 / V obtained in this invention. S -Zn3In2S6 exhibits excellent activity, enhanced CH4 selectivity, and good stability in the photocatalytic CO2 reduction reaction. Its preparation method is simple and easy, and it has good application prospects in the photocatalytic CO2 reduction reaction.

Description

Technical Field

[0001] This invention belongs to the fields of air pollution control, energy conservation and emission reduction, and the use of CO2 to produce high-value-added chemical products. Specifically, it relates to an S-type heterojunction photocatalyst WO3 / V composed of sulfur-defect-containing indium zinc sulfide and tungsten oxide. S -Zn3In2S6, its preparation method, and its application in photocatalytic CO2 reduction reaction. This WO3 / V S -Zn3In2S6 catalyst can achieve photocatalytic reduction of CO2 to CO and CH4, and has good activity and stability, providing a new approach for photocatalytic CO2 reduction. Background Technology

[0002] Today, the massive consumption of fossil fuels has led to a year-on-year increase in atmospheric carbon dioxide concentration, triggering a series of environmental problems, including global warming, sea-level rise, ocean acidification, extreme weather, species extinction, and food shortages. To date, many methods for converting carbon dioxide have been explored, including thermocatalysis, electrocatalysis, and photocatalysis. Thermocatalysis typically exhibits high efficiency in carbon dioxide reduction, but usually requires harsh conditions of high temperature and high pressure, resulting in considerable energy costs and safety issues. Electrocatalysis is carried out under an external electric field, and due to overpotential, there is a trade-off between catalytic activity and selectivity. In contrast, photocatalysis relies on solar energy to reduce carbon dioxide, exhibiting advantages such as mild operating conditions, low energy consumption, and readily available resources. Inspired by artificial photosynthesis, utilizing abundant solar energy, cost-effective water, and photocatalysts for photocatalytic reduction of CO2 can convert CO2 into organic matter, thereby mitigating the greenhouse effect and the looming energy crisis.

[0003] Currently, the photocatalytic reduction of carbon dioxide on semiconductor photocatalysts involves at least three main steps: 1. When the energy of the semiconductor photocatalyst is equal to or greater than the band gap energy of the semiconductor (E... g When irradiated by a suitable light source, electron-hole pairs are generated. 2. The generated electrons and holes migrate to the surface of the semiconductor or a co-catalyst in contact with the semiconductor. It should be mentioned that only a portion of the support can reach the surface of the semiconductor or co-catalyst. A large portion of the electron-hole pairs recombine together, releasing energy in the form of heat or photons. 3. Photogenerated electrons reduce CO2 adsorbed on the catalyst surface to CO, HCOOH, CH3OH, or CH4, while holes oxidize H2O to O2.

[0004] In recent years, among numerous semiconductor catalysts, zinc indium sulfide (Zn3In2S6) has emerged as one of the most promising photocatalysts due to its suitable conduction and valence band positions for reducing and oxidizing CO2 and H2O, high light absorption efficiency, and good chemical stability. Its catalytic activity in the photocatalytic reduction of CO2 has been reported. However, severe recombination of photogenerated carriers and insufficient active sites limit the photocatalytic reduction activity of this material for CO2.

[0005] An S-type heterojunction consists of an oxide semiconductor (OP) and a reduced semiconductor (RP). When they come into contact, electrons in RP, which has a higher Fermi level, tend to transfer to OP, which has a lower Fermi level. The Fermi levels reach equilibrium, and OP and RP exhibit downward and upward band bending, respectively. At this point, RP is positively charged and OP is negatively charged, creating a built-in electric field from RP to OP. When illuminated, electrons in OP and RP are excited from the valence band to the conduction band. Due to Coulomb attraction, the built-in electric field, and band bending, photogenerated electrons in OP recombine with photogenerated holes in RP, preventing the transfer of photogenerated electrons in RP and holes in OP, thus preserving photogenerated carriers with higher redox capabilities. S-type heterojunctions are feasible in terms of both charge transfer and redox capability enhancement. However, S-type heterojunction photocatalysts still cannot avoid the phenomenon of insufficient CO2 active sites. To address this problem, this invention uses a catalyst modification method, modifying the catalyst by constructing an S-type heterojunction and introducing defects through illumination to achieve synergistic enhancement of CO2 reduction activity. Summary of the Invention

[0006] To address the issue of insufficient catalyst activity in existing photocatalytic CO2 reduction applications, this invention provides an S-type heterojunction photocatalyst WO3 / V composed of sulfur-defect-containing indium zinc sulfide and tungsten oxide. S -Zn3In2S6, its preparation method and applications: This method is simple and rapid, and yields WO3 / V S The Zn3In2S6 catalyst exhibits high photocatalytic activity for CO2 reduction and CH4 selectivity, providing a new approach for subsequent catalyst design and showing promising application prospects.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An S-type heterojunction photocatalyst composed of sulfur-defect-containing indium zinc sulfide and tungsten oxide, wherein the S-type heterojunction photocatalyst is a composite photocatalyst constructed by using sulfur-defect-containing indium zinc sulfide as the reducing semiconductor and tungsten oxide as the oxidizing semiconductor.

[0009] Furthermore, the aforementioned S-type heterojunction composite photocatalyst is WO3 / V S-Zn3In2S6, where WO3 and V S The molar ratio of Zn3In2S6 is 10~40:100.

[0010] Furthermore, the photoreduction activity of the aforementioned S-type heterojunction composite photocatalyst in H2O vapor was evaluated under ambient temperature and pressure using a 300W xenon lamp with a wavelength (λ) controlled within the range of 380 nm to 780 nm. Using a gas-solid batch reactor, with high-purity CO2 introduced and 3 mL of H2O injected, the CO generation rate was 13.68 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate was 34.68 μmol·g. -1 ·h -1 CH4 selectivity increased from 43% to 72%.

[0011] The above-mentioned method for preparing an S-type heterojunction photocatalyst involves preparing WO3 nanosheets using nitric acid solution and hydrated sodium tungstate as raw materials; adding WO3 nanosheets to hydrated zinc sulfate, hydrated indium nitrate, and thioacetamide as raw materials to hydrothermally synthesize a WO3 / Zn3In2S6 composite photocatalyst; and introducing sulfur defects into the WO3 / Zn3In2S6 composite photocatalyst using a phototreatment method to obtain the S-type heterojunction photocatalyst WO3 / V S -Zn3In2S6 (abbreviated as WO3 / V) S -ZIS).

[0012] The preparation method of the above-mentioned S-type heterojunction photocatalyst specifically includes the following steps:

[0013] S1: HNO3 was mixed with deionized water and stirred for 10 min to obtain solution A; Na2WO4·2H2O was dissolved in deionized water and stirred for 10 min to obtain solution B; solution A was added dropwise to solution B under magnetic stirring, and then stirred vigorously for 0.5 h. The mixture was transferred to a hydrothermal device, sealed, and reacted at 180℃ for 3 h; after the reaction was completed, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed with ethanol and deionized water, and then dried at 60℃ for 12 h to obtain WO3 nanosheets.

[0014] S2: ZnSO4·7H2O and In(NO3)3·4.5H2O were dissolved in deionized water and stirred for 0.5 h. Then CH3CSNH2 and WO3 nanosheets were added and stirring was continued for 0.5 h. The mixture was transferred to a hydrothermal device, sealed, and reacted at 160 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged to collect the precipitate, and washed with ethanol and deionized water. Then it was dried at 60 °C for 12 h to obtain the WO3 / Zn3In2S6 photocatalyst.

[0015] S3: Irradiation of the WO3 / Zn3In2S6 photocatalyst for 0.5 h yielded the S-type heterojunction photocatalyst WO3 / V. S -Zn3In2S6.

[0016] Furthermore, in step S1 above, the concentration of HNO3 solution is 65%, and the volume is 10 ml; the volume of Na2WO4·2H2O is 1.0 g.

[0017] Furthermore, in step S2 above, the molar ratio of ZnSO4·7H2O, In(NO3)3·4.5H2O, CH3CSNH2, and WO3 nanosheets is 30:20:60:1~4.

[0018] Furthermore, in step S3 above, the illumination conditions are: the light source is a xenon lamp with a light wave band of 380~780 nm and a xenon lamp power of 300 W.

[0019] The above-mentioned S-type heterojunction photocatalyst is used in photocatalytic CO2 reduction.

[0020] The significant advantages of this invention are:

[0021] This invention modifies Zn3In2S6 by constructing an S-type heterojunction with WO3 nanosheets in a suitable ratio and introducing sulfur vacancies, resulting in a WO3 / V S The sulfur vacancies on the surface of the Zn3In2S6 catalyst serve as adsorption sites for CO2, promoting CO2 adsorption and activation. Furthermore, the S-shaped heterostructure assembled with WO3 nanosheets not only accelerates the migration and separation of photoexcited charge carriers but also enhances the adsorption of H2O and V2O. S The formation of the S-type heterojunction facilitates the adsorption and activation of more CO2 and promotes the protonation of *CO to form CH4. The synergistic optimization of the S-type heterojunction and sulfur vacancies in carbon dioxide reduction improves the activity and CH4 selectivity of the prepared catalyst in the CO2 reduction reaction under UV-Vis light. Attached Figure Description

[0022] Figure 1 V S -Zn3In2S6, WO3, 10%WO3 / V S -Zn3In2S6、20%WO3 / V S -Zn3In2S6、30%WO3 / V S -Zn3In2S6 and 40%WO3 / V S XRD pattern of Zn3In2S6.

[0023] Figure 2 V S-Zn3In2S6, WO3, 20%WO3 / V S DRS plot of Zn3In2S6.

[0024] Figure 3 V S -Zn3In2S6, WO3 and 20%WO3 / V S SEM image of Zn3In2S6.

[0025] Figure 4 V S -Zn3In2S6, WO3, 20%WO3 / V S Photocurrent and impedance diagrams of Zn3In2S6.

[0026] Figure 5 V S -Zn3In2S6, WO3, 10%WO3 / V S -Zn3In2S6、20%WO3 / V S -Zn3In2S6、30%WO3 / V S -Zn3In2S6 and 40%WO3 / V S Evaluation diagrams of the photocatalytic CO2 reduction activity and selectivity of Zn3In2S6. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention; that is, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the accompanying drawings and embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0028] Example 1: 10% WO3 / V S Preparation of Zn3In2S6

[0029] S1: Mix 10 mL of 65 wt% HNO3 with 40 mL of deionized water and stir for 10 min to obtain solution A; dissolve 1.0 g of Na2WO4·2H2O in 20 mL of deionized water and stir for 10 min to obtain solution B; add solution A dropwise to solution B under magnetic stirring, and stir vigorously for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 180 °C for 3 h; after the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence, and then dry it at 60 °C for 12 h to obtain WO3 nanosheets (abbreviated as WO3).

[0030] S2: Dissolve 3.0 mmol of ZnSO4·7H2O and 2.0 mmol of In(NO3)3·4.5H2O in 60 ml of deionized water and stir for 0.5 h. Then add 6.0 mmol of CH3CSNH2 and 0.1 mmol of WO3 nanosheets and continue stirring for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 160 °C for 12 h. After the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence. Then dry it at 60 °C for 12 h to obtain 10% WO3 / Zn3In2S6 photocatalyst.

[0031] S3: The WO3 / Zn3In2S6 photocatalyst was irradiated with a 300 W xenon lamp equipped with an infrared filter (wavelength range 380 nm-780 nm) for 0.5 h to obtain an S-type heterojunction photocatalyst with 10% WO3 / V S -Zn3In2S6.

[0032] Example 2: 20% WO3 / V S Preparation of Zn3In2S6

[0033] S1: Mix 10 mL of 65 wt% HNO3 with 40 mL of deionized water and stir for 10 min to obtain solution A; dissolve 1.0 g of Na2WO4·2H2O in 20 mL of deionized water and stir for 10 min to obtain solution B; add solution A dropwise to solution B under magnetic stirring, and stir vigorously for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 180 °C for 3 h; after the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence, and then dry it at 60 °C for 12 h to obtain WO3 nanosheets.

[0034] S2: Dissolve 3.0 mmol of ZnSO4·7H2O and 2.0 mmol of In(NO3)3·4.5H2O in 60 mL of deionized water and stir for 0.5 h. Then add 6.0 mmol of CH3CSNH2 and 0.2 mmol of WO3 nanosheets and continue stirring for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 160 °C for 12 h. After the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence. Then dry it at 60 °C for 12 h to obtain 20% WO3 / Zn3In2S6 photocatalyst.

[0035] S3: The WO3 / Zn3In2S6 photocatalyst was irradiated with a 300 W xenon lamp equipped with an infrared filter (wavelength range 380 nm-780 nm) for 0.5 h to obtain an S-type heterojunction photocatalyst with 20% WO3 / V S -Zn3In2S6.

[0036] Example 3: 30%WO3 / V S Preparation of Zn3In2S6

[0037] S1: Mix 10 mL of 65 wt% HNO3 with 40 mL of deionized water and stir for 10 min to obtain solution A; dissolve 1.0 g of Na2WO4·2H2O in 20 mL of deionized water and stir for 10 min to obtain solution B; add solution A dropwise to solution B under magnetic stirring, and stir vigorously for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 180 °C for 3 h; after the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence, and then dry it at 60 °C for 12 h to obtain WO3 nanosheets.

[0038] S2: Dissolve 3.0 mmol of ZnSO4·7H2O and 2.0 mmol of In(NO3)3·4.5H2O in 60 mL of deionized water and stir for 0.5 h. Then add 6.0 mmol of CH3CSNH2 and 0.3 mmol of WO3 nanosheets and continue stirring for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 160 °C for 12 h. After the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence. Then dry it at 60 °C for 12 h to obtain 30% WO3 / Zn3In2S6 photocatalyst.

[0039] S3: The WO3 / Zn3In2S6 photocatalyst was irradiated with a 300 W xenon lamp equipped with an infrared filter (wavelength range 380 nm-780 nm) for 0.5 h to obtain an S-type heterojunction photocatalyst with 30% WO3 / V S -Zn3In2S6.

[0040] Example 4: 40%WO3 / V S Preparation of Zn3In2S6

[0041] S1: Mix 10 mL of 65 wt% HNO3 with 40 mL of deionized water and stir for 10 min to obtain solution A; dissolve 1.0 g of Na2WO4·2H2O in 20 mL of deionized water and stir for 10 min to obtain solution B; add solution A dropwise to solution B under magnetic stirring, and stir vigorously for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 180 °C for 3 h; after the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence, and then dry it at 60 °C for 12 h to obtain WO3 nanosheets.

[0042] S2: Dissolve 3.0 mmol of ZnSO4·7H2O and 2.0 mmol of In(NO3)3·4.5H2O in 60 ml of deionized water and stir for 0.5 h. Then add 6.0 mmol of CH3CSNH2 and 0.4 mmol of WO3 nanosheets and continue stirring for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 160 °C for 12 h. After the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence. Then dry it at 60 °C for 12 h to obtain a 40% WO3 / Zn3In2S6 photocatalyst.

[0043] S3: Irradiating the WO3 / Zn3In2S6 photocatalyst with a 300 W xenon lamp equipped with an infrared filter (wavelength range 380 nm-780 nm) for 0.5 h yielded an S-type heterojunction photocatalyst with 40% WO3 / V S -Zn3In2S6.

[0044] Comparative example:

[0045] S1: Dissolve 3.0 mmol of ZnSO4·7H2O and 2.0 mmol of In(NO3)3·4.5H2O in 60 ml of deionized water and stir for 0.5 h. Then add 6.0 mmol of CH3CSNH2 and continue stirring for 0.5 h. Transfer the mixture to a hydrothermal apparatus, seal it, and react at 160 °C for 12 h. After the reaction is complete, cool to room temperature, centrifuge to collect the precipitate, and wash it with ethanol and deionized water in sequence. Then dry it at 60 °C for 12 h to obtain the Zn3In2S6 photocatalyst.

[0046] S2: The Zn3In2S6 photocatalyst was irradiated with a 300 W xenon lamp equipped with an infrared filter (wavelength range 380 nm-780 nm) for 0.5 h to obtain sulfur vacancy Zn3In2S6 photocatalyst V. S -Zn3In2S6 (abbreviated as V) S -ZIS).

[0047] Catalyst performance evaluation:

[0048] The photoreduction activity of carbon dioxide in H2O vapor was evaluated in a 175 mL gas-solid batch reactor. 20 mg of photocatalyst was dispersed in 3 mL of water, spread on a tray, and dried at 80 °C to form a uniform thin film before being placed in the reactor. The reactor was then evacuated using a vacuum pump, and carbon dioxide (99.999%) was injected. Next, 2 mL of deionized water was injected into the bottom of the reactor, and the mixture was continuously stirred with a magnetic stirrer. A 300 WXe lamp equipped with an infrared filter (wavelength range 380 nm to 780 nm) was then placed 2–3 cm above the top of the reactor. After specified reaction time intervals, 1 mL of the reaction gas was extracted from the reactor using a chromatographic needle for analysis. The gaseous products were analyzed using a gas chromatograph (Agilent 7890B) equipped with a high-sensitivity thermal conductivity detector (TCD) and flame ionization detector (FID).

[0049] The yield of the gas can be calculated using the following formula:

[0050]

[0051] Where Y is the gas yield, k is the standard curve coefficient of the gas obtained by the external standard method, and S a The area for gas chromatography determination of gas content, V is the reactor volume, m cat t represents the catalyst mass and t represents the reaction time.

[0052] The photocatalytic CO2 reduction performance of various catalysts was evaluated using this method, and the results are shown in Table 1.

[0053] Table 1. Catalytic CO2 reduction performance of different catalysts

[0054]

[0055] As shown in Table 1, compared to the Zn3In2S6 catalyst, the introduction of sulfur defects significantly improved V. S The activity of Zn3In2S6, after complexing with WO3, increases the WO3 / V ratio. S -Zn3In2S6 exhibits significantly enhanced photocatalytic CO2 reduction activity and improved CH4 selectivity.

[0056] Figure 1 For V S -Zn3In2S6,WO3, 10%WO3 / V S -Zn3In2S6, 20%WO3 / V S -Zn3In2S6, 30%WO3 / V S-Zn3In2S6 and 40%WO3 / V S XRD pattern of Zn3In2S6. From Figure 1 As can be seen from this, in WO3 / V S Peaks belonging to WO3 and ZIS were observed in the ZIS composite material. The intensity of the WO3 diffraction peak increased slightly with increasing WO3 content. Meanwhile, no other impurities were detected, reflecting good phase purity in the prepared sample.

[0057] Figure 2 For V S -Zn3In2S6, WO3 and 20%WO3 / V S DRS plot of Zn3In2S6. Figure 2 As can be seen from V S The maximum absorption edges of Zn3In2S6 and WO3 are approximately 500 nm and 460 nm, respectively, indicating that both are photocatalysts that respond to visible light.

[0058] Figure 3 For V S -Zn3In2S6, WO3 and 20%WO3 / V S SEM image of Zn3In2S6. From Figure 3 a shows that V S -Zn3In2S6 exhibits a flower-shaped microsphere structure composed of ultrathin, smooth, interlaced two-dimensional nanosheets. From Figure 3 As can be seen from b, WO3 is composed of irregular two-dimensional nanosheets. From Figure 3 As can be seen from the CD, the WO3 nanosheets are firmly embedded in V. S A 2D / 2D hybrid structure was formed in the Zn3In2S6 microspheres.

[0059] Figure 4 For V S -Zn3In2S6, WO3 and 20%WO3 / V S The photocurrent and impedance diagrams of Zn3In2S6 show that a larger photocurrent response and smaller impedance radius indicate better electron transfer capability, which will accelerate electron transfer and suppress recombination of photogenerated electron-hole pairs. (From the photocurrent flow diagram...) Figure 4 a) It can be seen that the photocurrent response of WO3 is almost negligible, while 20%WO3 / V S The photocurrent response of the Zn3In2S6 composite material significantly exceeds that of the V alone. S -Zn3In2S6, of which 20%WO3 / V S The Zn3In2S6 composite material exhibits the highest photocurrent response. This is evident from electrochemical impedance spectroscopy (EIS). Figure 4b) Measurement results show that 20%WO3 / V S The semi-circular diameters of the Zn3In2S6 composite material are all smaller than those of WO3 and V alone. S - The semi-circular diameter of Zn3In2S6. Including 20% ​​WO3 / V S -Zn3In2S6 exhibits the smallest radius of curvature in its spectrum, indicating the lowest electrochemical impedance. This suggests that due to the construction of the S-type heterojunction, 20% WO3 / V S -Zn3In2S6 can generate more photogenerated electrons under ultraviolet-visible light irradiation, and the resistance to the transfer of photogenerated electrons is smaller. This is conducive to more photogenerated electrons participating in the reaction, thereby improving the performance of the catalyst.

[0060] Figure 5 For V S -Zn3In2S6, WO3, 10%WO3 / V S -Zn3In2S6, 20%WO3 / V S -Zn3In2S6, 30%WO3 / V S -Zn3In2S6 and 40%WO3 / V S Evaluation graphs of the photocatalytic CO2 reduction activity and selectivity of Zn3In2S6. From Figure 5 It can be seen that, under normal temperature and pressure, the photoreduction activity of CO2 in H2O vapor was evaluated by controlling the light wavelength (λ) range of 380 nm - 780 nm using a 300W xenon lamp. A gas-solid batch reactor was used, with high-purity CO2 and 3 mL of H2O introduced, at a 20% WO3 / V ratio. S The Zn3In2S6 catalyst exhibited the best activity and CH4 selectivity, with a CO formation rate of 13.68 μmol·g⁻¹. -1 ·h -1 The CH4 formation rate was 34.68 μmol·g. -1 ·h -1 CH4 selectivity increased from 43% to 72%. In terms of mechanism of action, when the WO3 loading is less than 20%, there are not enough new adsorption activation sites on the material surface, resulting in poor activity; while when the content is higher than 20%, the excessive WO3 loading reduces the adsorption activation sites due to aggregation and shielding effects, which leads to a decrease in activity.

[0061] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A sulfur-defect-containing S-type heterojunction photocatalyst composed of indium zinc sulfide and tungsten oxide, characterized in that: The S-type heterojunction photocatalyst is an S-type heterojunction composite photocatalyst constructed by using indium zinc sulfide with sulfur defects as the reducing semiconductor and tungsten oxide as the oxidizing semiconductor; the S-type heterojunction composite photocatalyst is WO3 / VS-Zn3In2S6, wherein the molar ratio of WO3 to VS-Zn3In2S6 is 10~40:

100. The preparation method of the S-type heterojunction photocatalyst is as follows: WO3 nanosheets are prepared using nitric acid solution and hydrated sodium tungstate as raw materials; WO3 nanosheets are added to hydrated zinc sulfate, hydrated indium nitrate, and thioacetamide as raw materials to hydrothermally synthesize a WO3 / Zn3In2S6 composite photocatalyst; sulfur defects are introduced into the WO3 / Zn3In2S6 composite photocatalyst using a phototreatment method to obtain the S-type heterojunction photocatalyst WO3 / VS-Zn3In2S6; the preparation method specifically includes the following steps: S1: HNO3 solution was mixed with deionized water and stirred for 10 min to obtain solution A; Na2WO4·2H2O was dissolved in deionized water and stirred for 10 min to obtain solution B; solution A was added dropwise to solution B under magnetic stirring, and then stirred vigorously for 0.5 h. The mixture was transferred to a hydrothermal device, sealed, and reacted at 180 °C for 3 h; after the reaction was completed, the mixture was cooled to room temperature, centrifuged to collect the precipitate, washed with ethanol and deionized water, and then dried at 60 °C for 12 h to obtain WO3 nanosheets. S2: ZnSO4·7H2O and In(NO3)3·4.5H2O were dissolved in deionized water and stirred for 0.5 h. Then CH3CSNH2 and WO3 nanosheets were added and stirred for another 0.5 h. The mixture was then transferred to a hydrothermal apparatus, sealed, and reacted at 160 °C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged to collect the precipitate, and washed with ethanol and deionized water. The precipitate was then dried at 60 °C for 12 h to obtain the WO3 / Zn3In2S6 photocatalyst. S3: Irradiate the WO3 / Zn3In2S6 photocatalyst for 0.5 h to obtain the S-type heterojunction photocatalyst WO3 / VS-Zn3In2S6.

2. The S-type heterojunction photocatalyst according to claim 1, characterized in that: In step S1, the concentration of HNO3 solution is 65%, and the volume is 10 ml; the volume of Na2WO4·2H2O is 1.0 g.

3. The S-type heterojunction photocatalyst according to claim 1, characterized in that: In step S2, the molar ratio of ZnSO4·7H2O, In(NO3)3·4.5H2O, CH3CSNH2, and WO3 nanosheets is 30:20:60:1~4.

4. The S-type heterojunction photocatalyst according to claim 1, characterized in that: In step S3, the illumination conditions are: the light source is a xenon lamp with a light wave band of 380~780nm and a xenon lamp power of 300W.

5. The application of the S-type heterojunction photocatalyst as described in any one of claims 1 to 4 in photocatalytic CO2 reduction.

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