A photocatalyst and its preparation method and application

Abstract

The present invention discloses a photocatalyst and its preparation method and application, belonging to the field of semiconductor photocatalytic water decomposition hydrogen production technology. A photocatalyst preparation method comprises the following steps: S1: preparing CeVO4 nanoparticles, S2: preparing AZnIn2S4 / BCeVO4 heterojunction nanomaterials, using a solvent thermal synthesis method, weighing zinc chloride, indium trichloride tetrahydrate, and thioacetamide and dissolving them in a solvent, continuously ultrasonicating for 25-40 minutes to obtain a mixed solution, dispersing the CeVO4 nanoparticles prepared in step S1 in the mixed solution, ultrasonicating for 25-35 minutes at room temperature, then transferring to an autoclave for heating, centrifuging to obtain a precipitate, washing the precipitate, removing impurities on the precipitate surface, and drying to obtain the AZnIn2S4 / BCeVO4 heterojunction nanomaterial as a photocatalyst. The present invention synthesizes the AZnIn2S4 / BCeVO4 heterojunction by a solvent thermal method to obtain a photocatalyst with high photocatalytic performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor photocatalytic water decomposition to produce hydrogen, and in particular relates to a photocatalyst and a preparation method and application thereof. Background Art

[0002] Energy is a vital foundation for the survival and sustainable development of human society. Meeting growing energy demands while reducing carbon emissions is one of modern society's most daunting challenges, one that can only be addressed with the help of new sustainable energy technologies. Solar energy is the only renewable energy source that can adequately replace fossil fuels. Converting solar energy directly into clean energy is one of the most challenging scientific challenges of the 21st century. Hydrogen, a carbon-free, clean energy source, is widely considered an ideal fuel due to its unique advantages, including cleanliness, sustainability, high calorific value, and high energy density. Among various technologies, solar-driven water splitting for photocatalytic hydrogen production is considered the most important technology for converting inexhaustible solar energy into storable hydrogen fuel and an ideal hydrogen production pathway for the transition to low-carbon energy.

[0003] Among metal sulfide photocatalysts, ZnIn2S4 is a potential environmentally friendly, visible-light-driven photocatalyst. Its favorable optical properties and suitable band gap (2.2-2.8 eV) have attracted considerable research attention, demonstrating its suitability for visible-light photocatalytic hydrogen evolution. However, as with most photocatalysts, ZnIn2S4 suffers from poor photocatalytic activity due to its rapid electron-hole pair recombination, low carrier transport rate, and lack of active sites as a single semiconductor photocatalyst. Therefore, identifying a suitable semiconductor to match the energy levels of pure ZnIn2S4 to construct a composite photocatalyst to address these deficiencies is key to improving its photocatalytic hydrogen production capacity.

[0004] Cerium vanadate (CeVO4) is a relatively cheap semiconductor material with excellent optical absorption properties in the ultraviolet-visible region and its inherent special 4f electronic structure ([Xe] 4f 1 5d 1 6s 2 ) and the abundant rare earth element electron transition modes, resulting in good redox performance, which has become a current research hotspot. Although research on the physicochemical properties of CeVO4 has advanced rapidly, the design of its photocatalysts based on bandgap engineering remains an unresolved issue. The key challenge is the high electron-hole pair recombination rate, which makes it impossible to utilize the full spectrum of sunlight. Summary of the Invention

[0005] The purpose of the present invention is to provide a photocatalyst and its preparation method and application to overcome at least one of the above-mentioned defects in the prior art.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a photocatalyst, comprising the following steps: S1: preparing CeVO4 nanoparticles, weighing Ce(NO3)3·6H2O and dissolving it in a solvent, continuously stirring to obtain a Ce(NO3)3·6H2O solution, weighing NH4VO3 and adding it to a solvent to dissolve it, heating to obtain an NH4VO3 solution, dropwise adding the NH4VO3 solution into the Ce(NO3)3·6H2O solution to obtain a mixed solution A, heating the mixed solution A to form a precipitate A, cooling the mixed solution A to room temperature, filtering, collecting the precipitate A, washing and filtering the precipitate A multiple times, drying, and collecting to obtain CeVO4 nanoparticles; S2: preparing an AZnIn2S4 / BCeVO4 heterojunction nanomaterial, using a solvent thermal synthesis method, weighing zinc chloride, indium trichloride tetrahydrate, and thioacetamide and dissolving them in a solvent, continuously ultrasonicating for 25-40 minutes to obtain a mixed solution B, dispersing the CeVO4 nanoparticles prepared in step S1 in the mixed solution B, and ultrasonicating for 25-35 minutes at room temperature. min, then transferred to an autoclave for heating, centrifuged to collect precipitate B, washed to remove impurities on the surface of precipitate B, and then dried to obtain AZnIn2S4 / BCeVO4 heterojunction nanomaterials as a photocatalyst. In the AZnIn2S4 / BCeVO4 heterojunction nanomaterials, A is an integer of 1-7, and B is 1 or 2.

[0008] Preferably, in step S1: the solvent is ultrapure water, which is heated at 50°C-70°C to obtain an NH4VO3 solution, and the mixed solution A is heated in a constant temperature water bath at 80°C-100°C for 1.5-2.5 h to form a precipitate A. The precipitate A cooled to room temperature is filtered and washed multiple times with ethanol and ultrapure water, and then dried in a vacuum drying oven at 75°C-95°C and collected.

[0009] Preferably, in step S2, the solvent is ethylene glycol, which is heated at 110° C.-130° C. in a polytetrafluoroethylene-lined autoclave for 1.8-2.2 h, and dried in a vacuum drying oven for 11-13 h.

[0010] Preferably, in step S2, the molar ratio of zinc chloride, indium trichloride tetrahydrate and thioacetamide is 1:(1-3):(3-5).

[0011] Preferably, zinc chloride is replaced by zinc acetate or zinc nitrate.

[0012] The present invention also provides a photocatalyst, which is an AZnIn2S4 / BCeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method, wherein A is an integer of 1-7, and B is 1 or 2.

[0013] Preferably, in the AZnIn2S4 / BCeVO4 heterojunction nanomaterial, the molar ratio of ZnIn2S4 to CeVO4 is (1-7): (1-2).

[0014] Preferably, in the AZnIn2S4 / BCeVO4 heterojunction nanomaterial, the molar ratio of ZnIn2S4 and CeVO4 is 1:1, 1:2, 3:2, 2:1, 5:2, 3:1 or 7:2.

[0015] Preferably, in the AZnIn2S4 / BCeVO4 heterojunction nanomaterial, the molar ratio of ZnIn2S4 to CeVO4 is 3:1.

[0016] The present invention also provides a photocatalyst prepared by the above-mentioned method for preparing the photocatalyst or the use of the above-mentioned photocatalyst as a photocatalytic water decomposition for producing hydrogen.

[0017] Preferably, when the photocatalyst prepared by the above-mentioned photocatalyst preparation method or the above-mentioned photocatalyst is used for photocatalytic water decomposition to produce hydrogen, a mixed solution of sodium sulfide and sodium sulfite is used as a sacrificial agent.

[0018] The beneficial effects of the present invention are:

[0019] 1. The AZnIn2S4 / BCeVO4 heterojunction was synthesized by a solvothermal method to obtain a photocatalyst with high photocatalytic performance.

[0020] 2. By optimizing the molar weight of the AZnIn2S4 / BCeVO4 heterojunction, the photocatalytic hydrogen evolution rate of the optimal photocatalyst 3ZnIn2S4 / CeVO4 heterojunction can reach 15375 μmol⋅g -1 h -1 , its catalytic activity is single-component ZnIn2S4 (816μmol⋅g -1 h -1 ) or CeVO4(154 μmol⋅g -1 h -1 The enhancement of photocatalytic activity is mainly attributed to the broadening of the light absorption range of the photocatalyst, the improvement of the photocatalyst's utilization of sunlight, and the suppression of the recombination of photogenerated carriers.

[0021] 3. The photocatalyst of the present invention can be used for photocatalytic decomposition of water to produce hydrogen.

[0022] 4. The present invention realizes high-efficiency photocatalytic decomposition of water to produce hydrogen, and has high practical value and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1It is the XRD diagram of CeVO4, ZnIn2S4 and ZnIn2S4 / CeVO4 system heterojunction nanomaterials prepared by the present invention.

[0024] Figure 2 This is a field emission scanning electron microscope (FESEM) image of CeVO4 prepared in the present invention.

[0025] Figure 3 This is a field emission scanning electron microscope (FESEM) image of ZnIn2S4 prepared in the present invention.

[0026] Figure 4 This is a field emission scanning electron microscope (FESEM) image of 3ZnIn2S4 / CeVO4 prepared in the present invention.

[0027] Figure 5 It is the ultraviolet-visible diffuse reflectance (DRS) graph of CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 system heterojunction nanomaterials prepared by the present invention.

[0028] Figure 6 This is a performance diagram of photocatalytic water decomposition to produce hydrogen by CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 system heterojunction nanomaterials prepared in the present invention under the full spectrum and the condition of a mixed solution of sodium sulfide and sodium sulfite as a sacrificial agent. DETAILED DESCRIPTION

[0029] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0030] Example 1:

[0031] The method for preparing the photocatalyst provided in this embodiment comprises the following steps:

[0032] S1: Preparation of CeVO4 nanoparticles:

[0033] (1) Using the precipitation method, 0.434 g of Ce(NO3)3·6H2O was weighed and dissolved in 20 mL of ultrapure water. After continuous stirring, a Ce(NO3)3·6H2O solution (slightly transparent) was obtained.

[0034] (2) Weigh 0.117 g of NH4VO3 and dissolve it in 20 mL of ultrapure water. Heat the mixture at 60°C to obtain an NH4VO3 solution (light yellow).

[0035] (3) NH4VO3 solution was added dropwise to Ce(NO3)3·6H2O solution to obtain mixed solution A. Mixed solution A was heated in a constant temperature water bath at 90°C for 2 h to form precipitate A (brown).

[0036] (4) The mixed solution A was cooled to room temperature, filtered, and the precipitate A was collected. The precipitate A was washed and filtered with ethanol and ultrapure water for multiple times, and then dried in a vacuum drying oven at 80°C and collected to obtain CeVO4 nanoparticles.

[0037] S2: Preparation of ZnIn2S4 / CeVO4 heterojunction nanomaterials:

[0038] (5) Using the solvothermal synthesis method, 0.34 g zinc chloride (ZnCl2), 1.46 g indium trichloride tetrahydrate (InCl3•4H2O), and 0.76 g thioacetamide (TAA) were weighed and dissolved in 50 mL ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0039] (6) Weigh 0.2 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0040] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0041] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain ZnIn2S4 / CeVO4 heterojunction nanomaterials as a photocatalyst.

[0042] The molar ratio of zinc chloride, indium trichloride tetrahydrate and thioacetamide in step S2 is 1:2:4.

[0043] In other embodiments, zinc chloride can be replaced by zinc acetate or zinc nitrate.

[0044] This embodiment also provides a photocatalyst, which is a ZnIn2S4 / CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method. The molar ratio of ZnIn2S4 to CeVO4 is 1:1.

[0045] This embodiment also provides a use of a photocatalyst prepared by the above-described photocatalyst preparation method or a photocatalyst as described above for photocatalytic water decomposition to produce hydrogen. When the photocatalyst prepared by the above-described photocatalyst preparation method or a photocatalyst as described above is used for photocatalytic water decomposition to produce hydrogen, a mixed solution of sodium sulfide and sodium sulfite is used as a sacrificial agent.

[0046] Example 2:

[0047] The difference between this embodiment and the first embodiment lies in step S2:

[0048] S2: Preparation of ZnIn2S4 / 2CeVO4 heterojunction nanomaterials:

[0049] (5) Using the solvothermal synthesis method, 0.34 g zinc chloride (ZnCl2), 1.46 g indium trichloride tetrahydrate (InCl3•4H2O), and 0.76 g thioacetamide (TAA) were weighed and dissolved in 50 mL ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0050] (6) Weigh 0.4 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0051] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0052] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain ZnIn2S4 / 2CeVO4 heterojunction nanomaterials as a photocatalyst.

[0053] This embodiment also provides a photocatalyst, which is a ZnIn2S4 / 2CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method. The molar ratio of ZnIn2S4 to CeVO4 is 1:2.

[0054] Example 3:

[0055] The difference between this embodiment and the first embodiment lies in step S2:

[0056] S2: Preparation of 3ZnIn2S4 / 2CeVO4 heterojunction nanomaterials:

[0057] (5) Using the solvothermal synthesis method, 1.02 g of zinc chloride (ZnCl2), 4.38 g of indium trichloride tetrahydrate (InCl3•4H2O), and 2.28 g of thioacetamide (TAA) were weighed and dissolved in 50 mL of ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0058] (6) Weigh 0.4 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0059] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0060] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain 3ZnIn2S4 / 2CeVO4 heterojunction nanomaterials as a photocatalyst.

[0061] This embodiment also provides a photocatalyst, which is a 3ZnIn2S4 / 2CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method, with a molar ratio of ZnIn2S4 to CeVO4 of 3:2.

[0062] Example 4:

[0063] The difference between this embodiment and the first embodiment lies in step S2:

[0064] S2: Preparation of 2ZnIn2S4 / CeVO4 heterojunction nanomaterials:

[0065] (5) Using the solvothermal synthesis method, 0.68 g zinc chloride (ZnCl2), 2.92 g indium trichloride tetrahydrate (InCl3•4H2O) and 1.52 g thioacetamide (TAA) were weighed and dissolved in 50 mL ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0066] (6) Weigh 0.2 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0067] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0068] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain 2ZnIn2S4 / CeVO4 heterojunction nanomaterials as a photocatalyst.

[0069] This embodiment also provides a photocatalyst, which is a 2ZnIn2S4 / CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method, with a molar ratio of ZnIn2S4 to CeVO4 of 2:1.

[0070] Embodiment 5:

[0071] The difference between this embodiment and the first embodiment lies in step S2:

[0072] S2: Preparation of 5ZnIn2S4 / 2CeVO4 heterojunction nanomaterials:

[0073] (5) Using the solvothermal synthesis method, 1.7 g zinc chloride (ZnCl2), 7.3 g indium trichloride tetrahydrate (InCl3•4H2O) and 3.8 g thioacetamide (TAA) were weighed and dissolved in 50 mL ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0074] (6) Weigh 0.4 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0075] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0076] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain 5ZnIn2S4 / 2CeVO4 heterojunction nanomaterials as a photocatalyst.

[0077] This embodiment also provides a photocatalyst, which is a 5ZnIn2S4 / 2CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method, with a molar ratio of ZnIn2S4 to CeVO4 of 5:2.

[0078] Example 6:

[0079] The difference between this embodiment and the first embodiment lies in step S2:

[0080] S2: Preparation of 3ZnIn2S4 / CeVO4 heterojunction nanomaterials:

[0081] (5) Using the solvothermal synthesis method, 1.02 g of zinc chloride (ZnCl2), 4.38 g of indium trichloride tetrahydrate (InCl3•4H2O), and 2.28 g of thioacetamide (TAA) were weighed and dissolved in 50 mL of ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0082] (6) Weigh 0.2 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0083] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0084] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain 3ZnIn2S4 / CeVO4 heterojunction nanomaterials as a photocatalyst.

[0085] This embodiment also provides a photocatalyst, which is a 3ZnIn2S4 / CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method, with a molar ratio of ZnIn2S4 to CeVO4 of 3:1.

[0086] Embodiment seven:

[0087] The difference between this embodiment and the first embodiment lies in step S2:

[0088] S2: Preparation of 7ZnIn2S4 / 2CeVO4 heterojunction nanomaterials:

[0089] (5) Using the solvothermal synthesis method, 2.38 g of zinc chloride (ZnCl2), 10.22 g of indium trichloride tetrahydrate (InCl3•4H2O), and 5.32 g of thioacetamide (TAA) were weighed and dissolved in 50 mL of ethylene glycol. The mixture was ultrasonicated for 30 min to obtain a mixed solution B.

[0090] (6) Weigh 0.4 g of CeVO4 nanoparticles prepared in step S1 and disperse them in mixed solution B. Ultrasonicate at room temperature for 30 min.

[0091] (7) The mixture was then transferred to a 100 mL polytetrafluoroethylene-lined autoclave and heated at 120 °C for 2 h. The precipitate B was collected by centrifugation.

[0092] (8) The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried in a vacuum drying oven for 12 h to obtain 7ZnIn2S4 / 2CeVO4 heterojunction nanomaterials as a photocatalyst.

[0093] This embodiment also provides a photocatalyst, which is a 7ZnIn2S4 / 2CeVO4 heterojunction nanomaterial prepared by the above-mentioned photocatalyst preparation method, with a molar ratio of ZnIn2S4 to CeVO4 of 7:2.

[0094] Embodiment 8:

[0095] This embodiment provides a method for preparing ZnIn2S4 nanoflowers:

[0096] 0.34 g zinc chloride (ZnCl2), 1.46 g indium trichloride tetrahydrate (InCl3•4H2O) and 0.76 g thioacetamide (TAA) were weighed and ultrasonically dissolved in 50 mL ethylene glycol, and stirred continuously at room temperature for 30 min; the formed solution was transferred to a 100 mL polytetrafluoroethylene-lined autoclave, heated at 120 ℃ for 2 h, centrifuged, washed, separated, and dried in a vacuum drying oven for 12 h to obtain a petal-like catalyst composed of ZnIn2S4 nanosheets.

[0097] Phase characterization of prepared CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 heterojunction nanomaterials:

[0098] Figure 1The XRD patterns of the prepared CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 heterojunction nanomaterials are shown below. The pure CeVO4 nanoparticles exhibit nine distinct characteristic diffraction peaks at 18.28°, 24.22°, 30.58°, 32.53°, 34.40°, 39.21°, 43.78°, 48.17°, and 55.91°, which are attributed to the diffraction of the (101), (200), (211), (112), (220), (301), (103), (312), and (420) crystal planes of the CeVO4 nanoparticles, respectively. The crystal diffraction data agree well with the results from the standard card PDF#12-0757 for tetragonal CeVO4. Pure ZnIn2S4 nanospheres have obvious diffraction peaks at 2 = 21.45°, 27.89°, 30.41°, 47.44°, 52.48° and 55.83°, which correspond to the (006), (102), (104), (110), (116) and (002) crystal plane diffraction of the standard card PDF#65-2023 of the hexagonal phase ZnIn2S4. Comparing the characteristic diffraction patterns of pure ZnIn2S4 with photocatalysts of different molar ratios, it was found that in the ZnIn2S4 / CeVO4 heterojunction catalyst, diffraction peaks of CeVO4 and ZnIn2S4 can be present, and the positions of the characteristic diffraction peaks are almost unchanged, indicating that the crystal structures of ZnIn2S4 and CeVO4 do not change after forming a heterojunction. It is noteworthy that after forming a heterojunction with ZnIn2S4, the diffraction peak of CeVO4 gradually weakens and eventually disappears with further addition of ZnIn2S4. This is due to the relatively weak diffraction intensity as the CeVO4 content in the heterojunction catalyst decreases. XRD patterns show that no other impurity phases are detected in any of the samples, indicating the high purity of the samples obtained.

[0099] Morphological characterization of prepared CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 heterojunction nanomaterials

[0100] CeVO4 nanoparticles showed irregular nanoparticles with diameters of 20-80 nm, which were larger in size and in agglomerated form ( Figure 2 The particle size of CeVO4 in all composite materials is similar. In the ZnIn2S4 sample, it can be clearly seen that many nanosheets with a thickness of about 20-30 nm are interwoven and self-assembled into a flower-like microsphere structure with a radius of 1-2 μm ( Figure 3 ), the nanosheet structure has a large specific surface area and can provide more active sites for photocatalytic reactions. Figure 4It can be clearly seen that CeVO4 presents relatively large particles. After CeVO4 is grown on ZnIn2S4 as a substrate, CeVO4 grows in situ and covers the surface of ZnIn2S4 nanoflower balls. The introduction of CeVO4 does not affect the growth of ZnIn2S4. It is evenly distributed on the surface of ZnIn2S4 and forms a firm attachment. After the ZnIn2S4 / CeVO4 forms a heterojunction, it has a more uniform and compact structure. The close adhesion between different catalysts to form an interface heterojunction will be beneficial to accelerate the rapid migration of photogenerated carriers during the photocatalytic reaction.

[0101] Characterization of optical properties of prepared CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 heterojunction nanomaterials

[0102] from Figure 5 As can be seen in the figure, CeVO4 exhibits a steep absorption edge in the visible light region, while the absorption edge of pure ZnIn2S4 in the visible light range is less steep and has a smaller wavelength, indicating that the visible light absorption range of ZnIn2S4 is smaller than that of CeVO4. The light absorption edge of the ZnIn2S4 / CeVO4 heterojunction has a significant red shift, and the visible light absorption range is expanded. Compared with pure ZnIn2S4, the heterojunction photocatalyst absorbs light over a wider range, indicating that the ZnIn2S4 / CeVO4 heterojunction is more efficient in utilizing visible light than pure ZnIn2S4. These results indicate that the simultaneous recombination of ZnIn2S4 and CeVO4 broadens the visible light absorption range of the ZnIn2S4 / CeVO4 heterojunction, and the heterojunction photocatalyst has an improved photocatalytic response to solar visible light.

[0103] Photocatalytic water splitting and hydrogen production performance test of the prepared CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 system series heterojunction nanomaterials under full spectrum irradiation

[0104] Under constant stirring, 0.02 g of the ZnIn2S4 / CeVO4 series photocatalyst was placed in a flat-paneled Pyrex flask containing 100 mL of aqueous solution (0.35 M sodium sulfide solution and 0.25 M sodium sulfite solution, volume ratio 1:1). After evacuation for 30 minutes, 20 mL of high-purity argon was introduced into the reactor via a syringe to remove oxygen from the reaction system. The photoreaction system was kept under vacuum until the pressure gauge stabilized. A 300 W xenon lamp was then used to illuminate the solution with full spectrum illumination. The amount of hydrogen produced by the reaction was measured and analyzed using a GC-9790II gas chromatograph, using Ar as the carrier gas and a TCD detector.

[0105] Depend on Figure 6It can be seen that CeVO4, ZnIn2S4, and ZnIn2S4 / CeVO4 heterojunction series samples all have good sunlight response.

[0106] Specific: Through Figure 6 It can be seen that among the ZnIn2S4 / CeVO4 heterojunction nanomaterials, the photocatalytic performance is best when the molar ratio of ZnIn2S4 and CeVO4 is 3:1, that is, 3ZnIn2S4 / CeVO4.

[0107] In this embodiment, the photocatalytic hydrogen evolution rate of the best photocatalyst 3ZnIn2S4 / CeVO4 heterojunction can reach 15375 μmol⋅g -1 h -1 , its catalytic activity is single-component ZnIn2S4( 816 μmol⋅g -1 h -1 ) or CeVO4(154 μmol⋅g -1 h -1 ) by 18.9 or 100 times. This enhanced photocatalytic activity is primarily attributed to broadening the photocatalyst's light absorption range, improving the photocatalyst's utilization of sunlight, and inhibiting the recombination of photogenerated carriers, enabling highly efficient photocatalytic water splitting to produce hydrogen. This approach has high practical value and application prospects.

[0108] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, it should be understood by those skilled in the art that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a photocatalyst for photocatalytic water decomposition to produce hydrogen, characterized in that: The following steps are involved: S1: preparing CeVO4 nanoparticles: weighing Ce(NO3)3·6H2O and dissolving it in a solvent, stirring continuously to obtain a Ce(NO3)3·6H2O solution, weighing NH4VO3 and adding it to the solvent to dissolve it, heating to obtain an NH4VO3 solution, dropping the NH4VO3 solution into the Ce(NO3)3·6H2O solution to obtain a mixed solution A, heating the mixed solution A to form a precipitate A, cooling the mixed solution A to room temperature, filtering, collecting the precipitate A, washing and filtering the precipitate A multiple times, drying, and collecting to obtain CeVO4 nanoparticles; S2: Preparation of ZnIn2S4 / CeVO4 heterojunction nanomaterials: Using a solvent thermal synthesis method, zinc chloride, indium trichloride tetrahydrate and thioacetamide were weighed and dissolved in a solvent, and ultrasonication was continued for 25-40 min to obtain a mixed solution B. The CeVO4 nanoparticles prepared in step S1 were dispersed in the mixed solution B, and ultrasonication was performed at room temperature for 25-35 min. The solution was then transferred to an autoclave for heating, and the precipitate B was collected by centrifugation. The precipitate B was washed to remove impurities on the surface of the precipitate B, and then dried to obtain a ZnIn2S4 / CeVO4 heterojunction nanomaterial, which is a photocatalyst. In the ZnIn2S4 / CeVO4 heterojunction nanomaterial, the molar ratio of ZnIn2S4 and CeVO4 is (1-7): (1-2).

2. The method for preparing a photocatalyst according to claim 1, wherein: In step S1: All solvents were ultrapure water; Heat at 50-70°C to obtain NH4VO3 solution; The mixed solution A is heated in a constant temperature water bath at 80°C-100°C for 1.5-2.5 hours to form a precipitate A; The precipitate A cooled to room temperature was washed with ethanol and ultrapure water, filtered multiple times, dried in a vacuum drying oven at 75° C.-95° C., and then collected.

3. The method for preparing a photocatalyst according to claim 1, wherein: In step S2: The solvent is ethylene glycol; Heat at 110-130 °C in a polytetrafluoroethylene-lined autoclave for 1.8-2.2 h; Drying treatment: Dry in a vacuum drying oven for 11-13 h.

4. The method for preparing a photocatalyst according to claim 1, wherein: In step S2: The molar ratio of zinc chloride, indium trichloride tetrahydrate and thioacetamide is 1:(1-3):(3-5).

5. The method for preparing a photocatalyst according to claim 1, wherein: The zinc chloride is replaced by zinc acetate or zinc nitrate.

6. A photocatalyst for photocatalytic water decomposition to produce hydrogen, characterized by: The photocatalyst is a ZnIn2S4 / CeVO4 heterojunction nanomaterial prepared by the preparation method according to any one of claims 1 to 5.

7. The photocatalyst according to claim 6, characterized in that: In the ZnIn2S4 / CeVO4 heterojunction nanomaterial, the molar ratio of ZnIn2S4 to CeVO4 is 3:

1.

8. Use of the photocatalyst prepared by the preparation method according to any one of claims 1 to 5 or the photocatalyst according to any one of claims 6 to 7 in photocatalytic water decomposition to produce hydrogen.

9. The use according to claim 8, characterized in that When the photocatalyst photocatalytically decomposes water to produce hydrogen, a mixed solution of sodium sulfide and sodium sulfite is used as a sacrificial agent.

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