A ternary composite photocatalyst, its preparation method and application

Abstract

The present invention relates to the technical field of semiconductor photocatalytic water splitting for hydrogen production, and particularly relates to a ternary composite photocatalyst, a preparation method thereof, and an application thereof. The ternary composite photocatalyst provided by the present invention comprises CaIn₂S₄ nanospheres and CoP / ZnP₂ composite nanoparticles deposited on the surface of the CaIn₂S₄ nanospheres. This ternary composite photocatalyst has good photocatalytic water splitting activity, can absorb visible light below 600 nm, effectively broadens the visible light absorption range of CaIn₂S₄, improves the solar energy conversion efficiency, and the ternary composite photocatalyst provided by the present invention can achieve efficient photocatalytic water splitting for hydrogen production, realize long-term stable catalysis, and has excellent water splitting for hydrogen production performance.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photocatalytic water splitting for hydrogen production, and particularly to a ternary composite photocatalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Semiconductor photocatalytic water splitting technology can utilize solar energy to split water into hydrogen, which is an effective strategy to solve the energy crisis and alleviate environmental pollution. Ternary metal sulfides are considered to be suitable hydrogen evolution photocatalysts, and their advantages are: (1) The electronegativity potential of the S 3p orbital is larger than that of the O 2p orbital, resulting in a narrower band gap and enabling the utilization of a wider solar spectrum; (2) Larger exposed active sites; (3) Diverse species and chemical structures; (4) Higher chemical stability and photo-stability than binary metal sulfides. However, the photocatalytic hydrogen evolution performance and solar energy utilization rate of ternary metal sulfides are still very low.

[0003] CaIn2S4 is an alkaline earth metal-based n-type semiconductor and has been widely used in the field of photocatalysis due to its high visible light activity and narrow band gap (1.68 - 1.74 eV). However, similar to other ternary metal sulfides, CaIn2S4 has poor photo-generated charge separation and transport performance, and it is difficult for interfacial charge transfer. Therefore, its photocatalytic hydrogen evolution performance and solar energy utilization rate are also very low. Summary of the Invention

[0004] In view of this, the present invention provides a ternary composite photocatalyst, a preparation method thereof, and an application thereof. The ternary composite photocatalyst provided by the present invention has good photocatalytic water splitting activity and excellent hydrogen production performance by water splitting.

[0005] In order to achieve the above-mentioned invention purposes, the present invention provides the following technical solutions:

[0006] The present invention provides a ternary composite photocatalyst, which includes CaIn2S4 microspheres and CoP / ZnP2 composite nanoparticles deposited on the surface of the CaIn2S4 microspheres.

[0007] Preferably, the molar ratio of the CoP / ZnP2 composite nanoparticles to CaIn2S4 is 0.2 - 0.8:1.

[0008] The present invention also provides a preparation method of the ternary composite photocatalyst described in the foregoing solution, including the following steps:

[0009] (1) Mix a zinc source, a cobalt source, water, and an alkali to perform a first hydrothermal reaction to obtain a precursor; subject the precursor to phosphating treatment to obtain CoP / ZnP2 composite nanoparticles;

[0010] (2) Mix calcium nitrate, indium nitrate, thioacetamide, ethanol and water to obtain a mixed solution;

[0011] (3) Perform a second hydrothermal reaction on the mixed solution and CoP / ZnP2 composite nanoparticles to obtain a ternary composite photocatalyst;

[0012] There is no limitation on the time sequence between step (1) and step (2).

[0013] Preferably, the zinc source is zinc chloride, and the cobalt source is cobalt chloride and / or cobalt nitrate.

[0014] Preferably, the molar concentration of the zinc source in the feed liquid of the first hydrothermal reaction is 0.01 - 0.1 mol / L, and the molar concentration of the cobalt source is 0.02 - 0.2 mol / L; in the feed liquid of the first hydrothermal reaction, the molar ratio of Zn 2+ and Co 2+ is 1:2 - 4.

[0015] Preferably, the phosphating treatment includes the following steps: mix the precursor with sodium hypophosphite and calcine to obtain CoP / ZnP2 composite nanoparticles; the mass ratio of sodium hypophosphite to the precursor is 20 - 30:1 - 1.5.

[0016] Preferably, the temperature of the calcination is 200 - 600 °C, the time is 20 - 260 min, and the calcination is carried out in a nitrogen atmosphere.

[0017] Preferably, the molar ratio of calcium nitrate, indium nitrate to thioacetamide is 1:2 - 3:4 - 6.

[0018] Preferably, the temperature of the first hydrothermal reaction is 100 - 200 °C, the time is 2 - 26 h; the temperature of the second hydrothermal reaction is 100 - 200 °C, the time is 2 - 26 h.

[0019] The present invention also provides the application of the ternary composite photocatalyst described in the foregoing solution in semiconductor photocatalytic water splitting for hydrogen production.

[0020] The present invention provides a ternary composite photocatalyst, which includes CaIn2S4 microspheres and CoP / ZnP2 composite nanoparticles deposited on the surface of the CaIn2S4 microspheres. The ternary composite photocatalyst provided by the present invention uses CoP / ZnP2 composite nanoparticles as a cocatalyst and loads them on the surface of CaIn2S4, increasing the reactive active sites, which is conducive to the rapid separation and migration of photogenerated electrons and holes at the surface and interface. This ternary composite photocatalyst can absorb visible light below 600 nm, effectively broadening the visible light absorption range of CaIn2S4, improving the solar energy conversion efficiency, and the ternary composite photocatalyst provided by the present invention can achieve efficient photocatalytic water splitting for hydrogen production and realize long-term stable catalysis.

[0021] Meanwhile, the preparation method of the ternary composite photocatalyst provided by the present invention has a simple preparation process, few operation steps, high production efficiency, and is easy to realize industrial mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Scanning electron microscope image of the precursor described in Example 1;

[0023] Figure 2 Scanning electron microscope image of the CoP / ZnP2 composite nanoparticles described in Example 1;

[0024] Figure 3 Scanning electron microscope image of the ternary composite photocatalyst described in Example 1;

[0025] Figure 4 X-ray diffraction pattern of CoP / ZnP2 and CaIn2S4 described in Example 2;

[0026] Figure 5 Hydrogen production activity diagram of the ternary composite photocatalyst described in Example 3;

[0027] Figure 6 Hydrogen production activity diagram of the binary composite photocatalyst described in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention provides a ternary composite photocatalyst, which includes CaIn2S4 microspheres and CoP / ZnP2 composite nanoparticles deposited on the surface of the CaIn2S4 microspheres. In the present invention, the molar ratio of the CoP / ZnP2 composite nanoparticles to CaIn2S4 is preferably 0.2 to 0.8:1, more preferably 0.3 to 0.4:1; the loading amount of the CoP / ZnP2 composite nanoparticles of the ternary composite photocatalyst is 10 wt% to 40 wt% of the CaIn2S4 microspheres.

[0029] In the present invention, CoP / ZnP2 composite nanoparticles in the ternary composite photocatalyst are loaded on the surface of CaIn2S4 as a co-catalyst, increasing the reaction active sites, facilitating the rapid separation and migration of photo-generated electrons and holes at the surface interface. Moreover, the ternary composite photocatalyst provided by the present invention can absorb visible light below 600 nm, effectively broadening the absorption range of CaIn2S4 and improving the solar energy conversion efficiency. At the same time, the ternary composite photocatalyst provided by the present invention can efficiently achieve photocatalytic water splitting for hydrogen production and realize long-term stable catalysis.

[0030] The present invention also provides a preparation method of the ternary composite photocatalyst described in the foregoing solution, comprising the following steps:

[0031] (1) Mix a zinc source, a cobalt source, water, and an alkali to conduct a first hydrothermal reaction to obtain a precursor; subject the precursor to phosphating treatment to obtain CoP / ZnP2 composite nanoparticles;

[0032] (2) Mix calcium nitrate, indium nitrate, thioacetamide, ethanol, and water to obtain a mixed solution;

[0033] (3) Conduct a second hydrothermal reaction on the mixed solution and the CoP / ZnP2 composite nanoparticles to obtain a ternary composite photocatalyst;

[0034] There is no limitation on the time sequence between step (1) and step (2).

[0035] In the present invention, unless otherwise specified, the required materials are all commercially available products well-known to those skilled in the art. The present invention has no special requirements for the mixing method, and a mixing method well-known to those skilled in the art can be used, such as stirring and mixing, ultrasonic mixing; when the mixing method is stirring and mixing, the rotation speed of the magnetic stirrer is preferably 100 - 300 rpm / min.

[0036] In the present invention, a zinc source, a cobalt source, water, and an alkali are mixed to conduct a first hydrothermal reaction to obtain a precursor. In the present invention, the zinc source is preferably zinc chloride. In the present invention, the cobalt source is preferably cobalt chloride and / or cobalt nitrate, and more preferably cobalt nitrate. In the present invention, the molar concentration of the zinc source in the feed liquid of the first hydrothermal reaction is preferably 0.01 - 0.1 mol / L, more preferably 0.02 - 0.05 mol / L, and the molar concentration of the cobalt source is preferably 0.02 - 0.2 mol / L, more preferably 0.04 - 0.15 mol / L; Zn 2+ and Co 2+The molar ratio is preferably 1:2 to 4, and more preferably 1:2 to 2.5. In the present invention, the base is preferably ammonia water, and the amount of the base is preferably adjusted to make the pH value of the feed liquid of the first hydrothermal reaction 9 to 11. In the present invention, the temperature of the first hydrothermal reaction is preferably 100 to 200 °C, more preferably 110 to 180 °C, still more preferably 120 °C, the time of the first hydrothermal reaction is preferably 2 to 26 h, more preferably 18 to 30 h, still more preferably 20 h; the pH value of the feed liquid of the first hydrothermal reaction is preferably 9 to 11. In the present invention, during the first hydrothermal reaction, the zinc source and the cobalt source undergo a precipitation reaction under alkaline conditions to form hydroxides, and the chemical formula of the precursor is represented as Zn x Co 1-x (OH) y .

[0037] In a specific embodiment of the present invention, it is preferred to first mix the zinc source, the cobalt source and water to obtain a mixed solution; after adding a base to the mixed solution to make the pH value of the feed liquid 9 to 11, then perform the first hydrothermal reaction.

[0038] In a specific embodiment of the present invention, the hydrothermal reaction is carried out in a reaction kettle with a polytetrafluoroethylene inner liner. In a specific embodiment of the present invention, before the hydrothermal reaction, it further includes pre-treating the polytetrafluoroethylene inner liner of the reaction kettle, and the pre-treatment preferably includes the following steps: successively cleaning and drying the polytetrafluoroethylene inner liner of the reaction kettle with aqua regia, deionized water and ethanol. The present invention has no special requirements for the cleaning method, and the cleaning methods well-known to those skilled in the art can be used. In the present invention, the drying method is preferably nitrogen blowing.

[0039] After obtaining the precursor, the present invention performs a phosphating treatment on the precursor to obtain CoP / ZnP2 composite nanoparticles. In the present invention, the phosphating reaction preferably includes the following steps: mixing the precursor with sodium hypophosphite and performing calcination to obtain CoP / ZnP2 composite nanoparticles. In the present invention, the mass ratio of sodium hypophosphite to the precursor is preferably 20 to 30:1 to 1.5, and more preferably 20:1. In the present invention, the calcination temperature is preferably 200 to 600 °C, more preferably 350 to 450 °C, still more preferably 300 to 400 °C, the calcination time is preferably 20 to 260 min, more preferably 40 to 200 min, still more preferably 60 to 120 min, and the calcination is preferably carried out in a nitrogen atmosphere. In the present invention, during the phosphating treatment, sodium hypophosphite decomposes at high temperature to generate PH3, which promotes the formation of CoP / ZnP2 composite nanoparticles as a complexing agent and improves the crystallinity of the product.

[0040] In a specific embodiment of the present invention, preferably, sodium hypophosphite and the precursor mixture are placed in a quartz boat, and the quartz boat is put into a tube furnace. After calcination under a nitrogen protection atmosphere, it is naturally cooled. The product in the quartz boat is the CoP / ZnP2 composite nanoparticles.

[0041] In the present invention, calcium nitrate, indium nitrate, thioacetamide, ethanol and water are mixed to obtain a mixed solution. In the present invention, the molar ratio of calcium nitrate, indium nitrate to thioacetamide is preferably 1:2-3:4-6, more preferably 1:2-2.5:4-5; the volume ratio of ethanol to water is preferably 1:1-1.5, more preferably 1:1; the mass ratio of calcium nitrate to water is preferably 1:100-150, more preferably 1:100. In an embodiment of the present invention, the molar ratio of calcium nitrate, indium nitrate to thioacetamide is 1:2.5:4, the volume ratio of ethanol to water is 1:1, and the mass ratio of calcium nitrate to water is 1:100. Under this ratio, the mixing process can ensure the complete dissolution of calcium nitrate, guarantee the complete conversion of the calcium source, and at the same time, can provide mild conditions for the second hydrothermal reaction process, ensure that the particles do not agglomerate during the second hydrothermal reaction process, and have good dispersibility.

[0042] After obtaining the mixed solution and the CoP / ZnP2 composite nanoparticles, the present invention performs a second hydrothermal reaction on the mixed solution and the CoP / ZnP2 composite nanoparticles to obtain the ternary composite photocatalyst. In the present invention, the temperature of the second hydrothermal reaction is preferably 100-200 °C, more preferably 120 °C, and the time of the second hydrothermal reaction is preferably 2-26 h, more preferably 24 h. In the present invention, the mass ratio of the mixed solution to the CoP / ZnP2 composite nanoparticles is preferably 75:1. During the second hydrothermal reaction process of the present invention, the CoP / ZnP2 composite nanoparticles are anchored on the surface of CaIn2S4 to obtain CaIn2S4 microspheres deposited with CoP / ZnP2.

[0043] In the present invention, after the second hydrothermal reaction, it is preferably further included to perform post-treatment on the second hydrothermal reaction product. The post-treatment preferably includes the following steps: washing and drying the second hydrothermal reaction product in sequence to obtain the ternary composite photocatalyst.

[0044] The present invention has no special requirements for the washing method, and any washing method well-known to those skilled in the art can be used, such as repeatedly rinsing with water or ethanol; the present invention has no special requirements for the drying method, and any drying method well-known to those skilled in the art can be used, such as heating and drying in a vacuum drying oven.

[0045] The present invention also provides an application of the ternary composite photocatalyst described in the foregoing solution in semiconductor photocatalytic water splitting for hydrogen production.

[0046] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] Example 1

[0048] (1) 0.6815 g of zinc chloride hexahydrate (ZnCl2·6H2O), 2.9103 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 60 mL of deionized water were mixed to obtain a first mixed solution; ammonia water (NH3·H2O) was added to the first mixed solution until the pH value of the mixed solution reached 9. The reaction material solution after adjusting the pH value was transferred to a reaction kettle with a polytetrafluoroethylene inner lining, heated at 180 °C for 20 h and then naturally cooled. After the precipitate was washed and centrifuged, it was dried at 80 °C for 12 h to obtain a precursor.

[0049] 6.0 g of sodium hypophosphite monohydrate (NaH2PO2·H2O) and 0.3 g of the precursor were mixed and placed in a quartz boat. The quartz boat was put into a tube furnace and calcined under a nitrogen protection atmosphere. It was heated to 400 °C at a heating rate of 5 °C / min and then held for 60 min, and then naturally cooled. The product in the quartz boat was CoP / ZnP2 composite nanoparticles.

[0050] ((2) 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), 0.6010 g of thioacetamide (TAA), 30 mL of deionized water and 30 mL of ethanol mixed solution were mixed to obtain a mixed solution.

[0051] (3) The mixed solution and 0.2388 g of the CoP / ZnP2 composite nanoparticles were mixed and stirred for 30 min to obtain a second mixed solution; the second mixed solution was transferred to a reaction kettle with a polytetrafluoroethylene inner lining, heated at 120 °C for 24 h and then naturally cooled. After the precipitate was washed and centrifuged, it was dried at 60 °C for 12 h to obtain a ternary composite photocatalyst. The loading amount of the CoP / ZnP2 composite nanoparticles in the ternary composite photocatalyst was 30%.

[0052] The precursor, CoP / ZnP2 composite nanoparticles and ternary composite photocatalyst described in Example 1 were scanned by an electron microscope, and the obtained SEM is as Figure 1 、Figure 2 and Figure 3 as shown. It can be seen from Figure 1 , Figure 2 and Figure 3 that the morphology of the ternary composite photocatalyst is mainly that CoP / ZnP2 uniformly wraps on the surface of CaIn2S4, and it can be seen that there are partial defect regions in the ternary composite nanoparticles provided in Example 1 of the present invention, generating more active sites.

[0053] Example 2

[0054] (1) Mix 0.6815 g of zinc chloride hexahydrate (ZnCl2·6H2O), 2.9103 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 60 mL of deionized water to obtain a first mixed solution; add ammonia water (NH3·H2O) to the first mixed solution until the pH value of the mixed solution reaches 9.5, transfer the reaction material solution after adjusting the pH value to a reaction kettle with a polytetrafluoroethylene inner liner, heat at a temperature of 180 °C for 20 h and then cool naturally, wash and centrifuge the precipitate, and dry at a temperature of 80 °C for 12 h to obtain a precursor;

[0055] Mix 4.0 g of sodium hypophosphite (NaH2PO2·H2O) and 0.2 g of the precursor and place them in a quartz boat, put the quartz boat into a tube furnace, calcine under a nitrogen protection atmosphere, raise the temperature to 400 °C at a heating rate of 5 °C / min and then hold for 60 min, and cool naturally. The product in the quartz boat is the CoP / ZnP2 composite nanoparticles.

[0056] (2) Mix 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·, 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), 0.6010 g of thioacetamide (TAA), 30 mL of deionized water and 30 mL of ethanol mixed solution to obtain a mixed solution.

[0057] (3) Mix the mixed solution and 0.1592 g of the CoP / ZnP2 composite nanoparticles, stir for 30 min to obtain a second mixed solution; transfer the second mixed solution to a reaction kettle with a polytetrafluoroethylene inner liner, heat at a temperature of 120 °C for 24 h, then cool naturally, wash and centrifuge the precipitate, and dry at a temperature of 60 °C for 12 h to obtain a ternary composite photocatalyst. The loading amount of the CoP / ZnP2 composite nanoparticles in the ternary composite photocatalyst is 20%.

[0058] Perform XRD tests on the CoP / ZnP2 composite nanoparticles, CaIn2S4 microspheres and the ternary composite photocatalyst described in Example 2. The obtained X-ray diffraction spectra are as Figure 4As shown in the figure. The preparation method of the CaIn2S4 nanoparticles comprises the following steps:

[0059] Mix 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), 0.6010 g of thioacetamide (TAA), 30 mL of deionized water and 30 mL of ethanol mixed solution to obtain a mixed solution; transfer the mixed solution to a reaction kettle lined with polytetrafluoroethylene, heat it at a temperature of 120 °C for 24 h, then cool it naturally, wash and centrifuge the precipitate, and dry it at a temperature of 60 °C for 12 h to obtain CaIn2S4 microspheres.

[0060] From Figure 4 It can be seen that the XRD peak positions appear at 31.60°, 36.32°, 46.24°, corresponding to the (011), (111), (112) planes (PDF#29 - 497), and 48.10° corresponding to the (-104) plane (PDF#24 - 1436), indicating that the CoP / ZnP2 composite nanoparticles were successfully prepared by phosphating treatment in Example 2 of the present invention. Moreover, it can be seen that the CoP / ZnP2 composite nanoparticles were successfully deposited on the surface of CaIn2S4 in Example 2 of the present invention.

[0061] Example 3

[0062] (1) Mix 0.6815 g of zinc chloride hexahydrate (ZnCl2·6H2O), 2.9103 g of cobalt nitrate hexahydrate (Co(NO3)2·6H2O) and 30 mL of deionized water to obtain a first mixed solution; add ammonia water (NH3·H2O) to the first mixed solution until the pH value of the mixed solution reaches 10, transfer the reaction material solution after adjusting the pH value to a reaction kettle lined with polytetrafluoroethylene, heat it at a temperature of 180 °C for 20 h and then cool it naturally, wash and centrifuge the precipitate, and dry it at a temperature of 80 °C for 12 h to obtain a precursor;

[0063] Place 8.0 g of sodium hypophosphite (NaH2PO2·H2O) and 0.4 g of the precursor mixture in a quartz boat, put the quartz boat into a tubular furnace, calcine it under a nitrogen protection atmosphere, heat it at a heating rate of 5 °C / min to 400 °C and then hold for 60 min, and cool it naturally. The product in the quartz boat is the CoP / ZnP2 composite nanoparticles.

[0064] (2) Mix 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), 0.6010 g of thioacetamide (TAA), 30 mL of deionized water and 30 mL of ethanol mixed solution to obtain a mixed solution.

[0065] (3) Mix the mixed solution with 0.3184 g of the CoP / ZnP₂ composite nanoparticles, stir for 30 min to obtain a second mixed solution; transfer the second mixed solution to a reaction kettle lined with polytetrafluoroethylene, heat it at 120 °C for 24 h, then let it cool naturally. Wash and centrifuge the precipitate, and dry it at 60 °C for 12 h to obtain a ternary composite photocatalyst, and the loading amount of the CoP / ZnP₂ composite nanoparticles in the ternary composite photocatalyst is 40%.

[0066] Comparative Example 1

[0067] (1) Mix 2.9103 g of cobalt nitrate hexahydrate (Co(NO₃)₂·6H₂O) with 60 mL of deionized water to obtain a first mixed solution; add ammonia water (NH₃·H₂O) to the first mixed solution until the pH value of the mixed solution reaches 9.5. Transfer the reaction material solution after adjusting the pH value to a reaction kettle lined with polytetrafluoroethylene, heat it at 180 °C for 20 h and then let it cool naturally. Wash and centrifuge the precipitate, and dry it at 80 °C for 12 h to obtain a precursor.

[0068] Put 4.0 g of sodium hypophosphite (NaH₂PO₂·H₂O) and 0.2 g of the precursor into quartz boats A and B respectively. Place quartz boats A and B at the upstream and downstream of a tube furnace, and calcine them under a nitrogen protection atmosphere. Heat them at a heating rate of 5 °C / min to 400 °C and then hold for 60 min, and let it cool naturally. The product in quartz boat B is CoP nanoparticles.

[0069] (2) Mix 0.2904 g of calcium nitrate tetrahydrate (Ca(NO₃)₂·4H₂O), 1.2033 g of indium nitrate pentahydrate (In(NO₃)₃·5H₂O), 0.6010 g of thioacetamide (TAA), 30 mL of deionized water and 30 mL of ethanol mixed solution to obtain a mixed solution.

[0070] (3) Mix the mixed solution with 0.1592 g of the CoP nanoparticles, stir for 30 min to obtain a second mixed solution; transfer the second mixed solution to a reaction kettle lined with polytetrafluoroethylene, heat it at 120 °C for 24 h, then let it cool naturally. Wash and centrifuge the precipitate, and dry it at 60 °C for 12 h to obtain a binary composite photocatalyst, and the loading amount of the CoP composite nanoparticles in the binary composite photocatalyst is 20%.

[0071] Comparative Example 2

[0072] (1) Mix 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), 0.6010 g of thioacetamide (TAA), 30 mL of deionized water and 30 mL of ethanol mixed solution to obtain a mixed solution.

[0073] (2) Transfer the mixed solution to a reaction kettle lined with polytetrafluoroethylene, heat it at 120 °C for 24 h, then cool it naturally. After washing and centrifuging the precipitate, dry it at 60 °C for 12 h to obtain the CaIn2S4 catalyst.

[0074] Test the photocatalytic hydrogen production amount of Examples 1-3 and Comparative Examples 1-2. The test method for the photocatalytic hydrogen production amount includes the following steps: Disperse 25 mg of the photocatalyst in a mixed aqueous solution containing 10 mL of triethanolamine and 40 mL of water to obtain a mixed solution; for the mixed solution, and use a cooling water circulation system to keep the reaction system at 5 °C, and use a vacuum pump to evacuate for 30 min to remove the dissolved air. Then irradiate the solution from which the dissolved air has been removed with a 300 W Xe lamp (CEL-HXF 300-T3) from the top, and use gas chromatography (GC-7920-TF2A) equipped with a TCD detector to online detect the generated H2 gas. The obtained time-hydrogen production amount curve is as Figure 5 and 6 shown. It can be seen from Figure 5 that the ternary composite photocatalyst has good photocatalytic water splitting activity. Among them, the ternary composite photocatalyst described in Example 1 has a hydrogen evolution yield of up to 4741.25 μmol / g under visible light with λ>420 nm for 4 h. At the same time, the ternary composite photocatalysts described in Examples 1-3 have a 24-fold increase in photocatalytic hydrogen production amount compared with CaIn2S4, which is much higher than the catalytic performance of the existing CaIn2S4-based composite photocatalysts. It can be seen from Figure 6 that the hydrogen production performance of the prepared binary composite photocatalyst is far inferior to that of the ternary composite photocatalyst. This is because the ternary composite photocatalysts described in Examples 1-3 of the present invention contain CoP / ZnP2, which can accelerate the separation and transportation of photo-generated carriers, significantly improve the yield of H2, and make the ternary composite photocatalyst have excellent catalytic performance.

[0075] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A ternary composite photocatalyst, characterized in that, The ternary composite photocatalyst comprises CaIn2S4 microspheres and CoP / ZnP2 composite nanoparticles deposited on the surface of the CaIn2S4 microspheres; The loading amount of the CoP / ZnP2 composite nanoparticles in the ternary composite photocatalyst is 20wt% - 40wt% of the CaIn2S4 microspheres; The molar ratio of CoP to ZnP2 in the CoP / ZnP2 composite nanoparticles is 2 - 4:

1.

2. The preparation method of the ternary composite photocatalyst according to claim 1, characterized in that, It includes the following steps: (1) Mix a zinc source, a cobalt source, water and an alkali to carry out a first hydrothermal reaction to obtain a precursor; subject the precursor to phosphidation treatment to obtain CoP / ZnP2 composite nanoparticles; (2) Mix calcium nitrate, indium nitrate, thioacetamide, ethanol and water to obtain a mixed solution; (3) Carry out a second hydrothermal reaction on the mixed solution and the CoP / ZnP2 composite nanoparticles to obtain a ternary composite photocatalyst; There is no limitation on the time sequence between step (1) and step (2).

3. The preparation method according to claim 2, wherein The zinc source is zinc chloride, and the cobalt source is cobalt chloride and / or cobalt nitrate.

4. The preparation method according to claim 2, characterized in that, In the feed liquid of the first hydrothermal reaction, the molar concentration of the zinc source is 0.01 to 0.1 mol / L, and the molar concentration of the cobalt source is 0.02 to 0.2 mol / L; Zn 2+ and Co 2+ in the feed liquid of the first hydrothermal reaction have a molar ratio of 1:2 to 4.

5. The preparation method according to claim 2, characterized in that, The phosphidation treatment includes the following steps: mix the precursor and sodium hypophosphite and carry out calcination to obtain CoP / ZnP2 composite nanoparticles; the mass ratio of sodium hypophosphite to the precursor is 20 - 30:1 - 1.

5.

6. The preparation method according to claim 5, characterized in that, The temperature of the calcination is 200 - 600 °C, the time is 20 - 260 min, and the calcination is carried out in a nitrogen atmosphere.

7. The preparation method according to claim 2, characterized in that, The molar ratio of calcium nitrate, indium nitrate to thioacetamide is 1:2 - 3:4 - 6.

8. The preparation method according to claim 2, characterized in that, The temperature of the first hydrothermal reaction is 100 - 200 °C, the time is 2 - 26 h; the temperature of the second hydrothermal reaction is 100 - 200 °C, the time is 2 - 26 h.

9. Application of the ternary composite photocatalyst according to claim 1 or the ternary composite photocatalyst prepared by the preparation method according to any one of claims 2 - 8 in semiconductor photocatalytic water splitting for hydrogen production.

Images