A P-ZIF-8 / CaIn2S4 composite material and its preparation method and application

Abstract

The present invention provides a P-ZIF-8 / CaIn2S4 composite material, a preparation method and application thereof, and relates to the technical field of semiconductor photocatalytic water decomposition to produce hydrogen. The P-ZIF-8 / CaIn2S4 composite material includes CaIn2S4 microspheres and P-ZIF-8 nanoparticles deposited on the CaIn2S4 microspheres, and the P-ZIF-8 nanoparticles are P-doped ZIF-8 nanoparticles. In the present invention, the P-ZIF-8 nanoparticles are deposited on the CaIn2S4 surface, and a heterojunction is formed through surface-interface interaction, which effectively inhibits the recombination of photogenerated electron-hole pairs and accelerates the separation and migration of photogenerated carriers. Compared with the composite of single MOFs and semiconductors, the present invention performs P-doping on ZIF-8 nanoparticles to increase the hydrogen production rate. The composite material provided by the present invention can achieve good photocatalytic water decomposition and hydrogen production performance as a photocatalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photocatalytic water decomposition to produce hydrogen, and in particular to a P-ZIF-8 / CaIn2S4 composite material and a preparation method and application thereof. Background Art

[0002] In recent years, with the development of industry and the widespread use of fossil fuels, energy and environmental issues have intensified. Semiconductor photocatalytic water splitting technology, which harnesses solar energy to decompose water into hydrogen, offers an effective strategy for addressing the energy crisis and alleviating environmental pollution. However, the solar energy utilization efficiency of semiconductor photocatalytic nanomaterials remains low. The development and utilization of new semiconductor photocatalytic nanomaterials is a hot topic in the field of photocatalysis.

[0003] Among numerous semiconductor photocatalytic materials, ternary metal sulfides possess suitable band gap widths and band edge positions, making them considered suitable hydrogen evolution photocatalysts. Among them, CaIn2S4 has attracted attention due to its narrow band gap (1.68-1.74 eV) and superior light absorption performance compared to some other semiconductor materials. However, similar to other ternary metal sulfides, single CaIn2S4 materials still suffer from the disadvantage of rapid recombination of photogenerated carriers, which inhibits their performance in photocatalytic water splitting for hydrogen production. Summary of the Invention

[0004] The purpose of the present invention is to provide a P-ZIF-8 / CaIn2S4 composite material and its preparation method and application. The P-ZIF-8 / CaIn2S4 composite material provided by the present invention has good photocatalytic water decomposition and hydrogen production performance as a photocatalyst.

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

[0006] The invention provides a P-ZIF-8 / CaIn2S4 composite material, comprising CaIn2S4 microspheres and P-ZIF-8 nanoparticles deposited on the CaIn2S4 microspheres, wherein the P-ZIF-8 nanoparticles are P-doped ZIF-8 nanoparticles.

[0007] Preferably, the molar ratio of the P-ZIF-8 nanoparticles to the CaIn2S4 microspheres is 0.05-0.2:1.

[0008] Preferably, the average pore diameter of the P-ZIF-8 / CaIn2S4 composite material is 20 to 22 nm.

[0009] The present invention provides a method for preparing the P-ZIF-8 / CaIn2S4 composite material described in the above scheme, comprising the following steps:

[0010] An inorganic water-soluble zinc source and dimethylimidazole are dispersed in anhydrous methanol, subjected to coordination reaction, and solid-liquid separation to obtain ZIF-8;

[0011] Co-calcining the ZIF-8 and a phosphorus source to obtain P-ZIF-8 nanoparticles;

[0012] The P-ZIF-8 nanoparticles, water, ethanol, a water-soluble calcium source, a water-soluble indium source and thioacetamide are mixed and subjected to a hydrothermal reaction to obtain a P-ZIF-8 / CaIn2S4 composite material.

[0013] Preferably, the molar ratio of zinc ions to dimethylimidazole in the inorganic water-soluble zinc source is 1:2-6; and the concentration of the inorganic water-soluble zinc source in anhydrous methanol is 0.01-0.1 mol / L.

[0014] Preferably, the phosphorus source includes sodium hypophosphite; the mass ratio of the phosphorus source to ZIF-8 is 5-30:1-1.5.

[0015] Preferably, the co-calcination temperature is 200-400° C., and the holding time is 60-240 min; and the co-calcination is carried out in a nitrogen atmosphere.

[0016] Preferably, the molar ratio of Ca in the water-soluble calcium source, In in the water-soluble indium source and thioacetamide is 1:2:4-6; the molar ratio of the P-ZIF-8 nanoparticles to Ca in the water-soluble calcium source is 0.05-0.2:1.

[0017] Preferably, the temperature of the hydrothermal reaction is 100-180° C., and the time is 12-32 hours.

[0018] The present invention provides the use of the P-ZIF-8 / CaIn2S4 composite material described in the above scheme or the P-ZIF-8 / CaIn2S4 composite material prepared by the preparation method described in the above scheme as a photocatalyst in photocatalytic water decomposition to produce hydrogen.

[0019] The present invention provides a P-ZIF-8 / CaIn2S4 composite material, comprising CaIn2S4 microspheres and P-ZIF-8 nanoparticles deposited on the CaIn2S4 microspheres, wherein the P-ZIF-8 nanoparticles are P-doped ZIF-8 nanoparticles. In the present invention, the P-ZIF-8 nanoparticles are deposited on the surface of CaIn2S4, forming a heterojunction through surface-interface interaction, effectively inhibiting the recombination of photogenerated electron-hole pairs while accelerating the separation and migration of photogenerated carriers. Compared to a single MOFs and semiconductor composite, the present invention performs P-doping on the ZIF-8 nanoparticles, thereby increasing the hydrogen production rate. The composite photocatalyst provided by the present invention can absorb visible light below 650nm, effectively broadening the visible light absorption range of CaIn2S4, and the composite material provided by the present invention can achieve good photocatalytic water decomposition and hydrogen production performance as a photocatalyst.

[0020] The present invention provides a method for preparing the P-ZIF-8 / CaIn2S4 composite material described in the above scheme. The preparation method of the present invention has readily available raw materials, a simple preparation process, few operating steps, excellent hydrogen production performance, and provides new ideas for the rational design of semiconductor photocatalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron micrograph of ZIF-8 prepared in Example 1;

[0022] Figure 2 This is a scanning electron micrograph of the P-ZIF-8 nanoparticles prepared in Example 1;

[0023] Figure 3 This is a scanning electron microscope image of the P-ZIF-8 / CaIn2S4 composite material prepared in Example 1;

[0024] Figure 4 The X-ray diffraction patterns of ZIF-8 and P-ZIF-8 nanoparticles prepared in Example 2;

[0025] Figure 5 This is the X-ray diffraction pattern of the P-ZIF-8 / CaIn2S4 composite material prepared in Example 2;

[0026] Figure 6 This is a hydrogen production activity diagram of the P-ZIF-8 / CaIn2S4 composite material prepared in Example 3;

[0027] Figure 7 This is the hydrogen production activity diagram of the ZIF-8 / CaIn2S4 composite material prepared in Comparative Example 1;

[0028] Figure 8This is the pore size distribution diagram of the P-ZIF-8 / CaIn2S4 composite material prepared in Example 1 and the CaIn2S4 prepared in Comparative Example 2. DETAILED DESCRIPTION

[0029] The invention provides a P-ZIF-8 / CaIn2S4 composite material, comprising CaIn2S4 microspheres and P-ZIF-8 nanoparticles deposited on the CaIn2S4 microspheres, wherein the P-ZIF-8 nanoparticles are P-doped ZIF-8 nanoparticles.

[0030] In the present invention, the molar ratio of the P-ZIF-8 nanoparticles to the CaIn2S4 microspheres is preferably 0.05 to 0.2:1, more preferably 0.1 to 0.15:1. In the present invention, the average pore diameter of the P-ZIF-8 / CaIn2S4 composite material is 20 to 22 nm, and in the embodiment of the present invention, specifically 21.48 nm.

[0031] In the present invention, the P doping amount in the P-ZIF-8 nanoparticles is preferably 3-5%, more preferably 4%. In the present invention, the P element is connected to the ZIF-8 nanoparticles via Zn-P bonds.

[0032] In the present invention, the P-ZIF-8 nanoparticles are deposited on the surface of CaIn2S4, forming a heterojunction through surface-interface interactions, effectively inhibiting the recombination of photogenerated electron-hole pairs while accelerating the separation and migration of photogenerated carriers. Compared to the composite of single MOFs and semiconductors, the present invention P-dopes the ZIF-8 nanoparticles, thereby increasing the hydrogen production rate. The composite photocatalyst provided by the present invention can absorb visible light below 650nm, effectively broadening the visible light absorption range of CaIn2S4. Furthermore, the composite material provided by the present invention can achieve good photocatalytic water splitting hydrogen production performance as a photocatalyst.

[0033] The present invention provides a method for preparing the P-ZIF-8 / CaIn2S4 composite material described in the above scheme, comprising the following steps:

[0034] An inorganic water-soluble zinc source and dimethylimidazole are dispersed in anhydrous methanol, subjected to coordination reaction, and solid-liquid separation to obtain ZIF-8;

[0035] Co-calcining the ZIF-8 and a phosphorus source to obtain P-ZIF-8 nanoparticles;

[0036] The P-ZIF-8 nanoparticles, water, ethanol, a water-soluble calcium source, a water-soluble indium source and thioacetamide are mixed and subjected to a hydrothermal reaction to obtain a P-ZIF-8 / CaIn2S4 composite material.

[0037] In the present invention, unless otherwise specified, the required raw materials are commercially available products well known to those skilled in the art.

[0038] The invention disperses an inorganic water-soluble zinc source and dimethylimidazole in anhydrous methanol, performs coordination reaction, and performs solid-liquid separation to obtain ZIF-8.

[0039] In the present invention, the inorganic water-soluble zinc source is preferably zinc chloride and / or zinc nitrate, more preferably zinc nitrate; the molar ratio of zinc ion to dimethylimidazole in the inorganic water-soluble zinc source is preferably 1:2-6, more preferably 1:3-5, and even more preferably 1:4. In the present invention, the concentration of the inorganic water-soluble zinc source in anhydrous methanol is preferably 0.01-0.1 mol / L, more preferably 0.02-0.08 mol / L, and even more preferably 0.04-0.06 mol / L.

[0040] The present invention has no special requirements for the dispersion method, and any dispersion method well known to those skilled in the art can be used, such as stirring dispersion and ultrasonic dispersion. When the mixing method is stirring dispersion, the stirring speed is preferably 200 to 600 rpm / min.

[0041] In the present invention, the coordination reaction is preferably carried out at room temperature with stirring. The room temperature described in the present invention does not require additional heating or cooling. The present invention has no particular requirements for the duration of the coordination reaction, as long as the precipitation no longer increases. During the coordination reaction, the zinc ion and the ligand dimethylimidazole undergo in situ self-assembly to form ZIF-8.

[0042] The present invention has no special requirements for the solid-liquid separation method, and any solid-liquid separation method known in the art can be used, such as centrifugation. After the solid-liquid separation, the present invention preferably further comprises washing the obtained solid with anhydrous methanol and drying it to obtain ZIF-8.

[0043] After obtaining ZIF-8, the present invention co-calcines the ZIF-8 with a phosphorus source to obtain P-ZIF-8 nanoparticles.

[0044] In the present invention, the phosphorus source preferably includes sodium hypophosphite, preferably sodium hypophosphite monohydrate. The mass ratio of the phosphorus source to ZIF-8 is preferably 5-30:1-1.5, more preferably 10-25:1, and even more preferably 20:1. In the present invention, the co-calcination preferably includes placing the phosphorus source and ZIF-8 in the upstream and downstream of a furnace for co-calcination. In the present invention, the co-calcination temperature is preferably 200-400°C, more preferably 250-350°C, and even more preferably 300°C; the holding time is preferably 60-240 minutes, more preferably 90-210 minutes, and even more preferably 120-180 minutes; and the co-calcination is preferably carried out in a nitrogen atmosphere. The present invention does not have any particular requirements for the heating rate to the co-calcination temperature; any heating rate known in the art can be used. In an embodiment of the present invention, the heating rate is 5°C / min. During the co-calcination process of the present invention, the phosphorus source decomposes to generate PH3, which coordinates with the metal ions, breaks the Zn-N bond and forms a Zn-P bond, thereby converting ZIF-8 into P-ZIF-8 particles.

[0045] In a specific embodiment of the present invention, the phosphorus source and ZIF-8 are preferably placed in porcelain boats respectively, and the porcelain boats are placed upstream and downstream of a tube furnace, calcined under a nitrogen inert atmosphere, and after natural cooling, the product in the downstream quartz boat is P-ZIF-8 nanoparticles.

[0046] After obtaining the P-ZIF-8 nanoparticles, the present invention mixes the P-ZIF-8 nanoparticles, water, ethanol, a water-soluble calcium source, a water-soluble indium source and thioacetamide, and performs a hydrothermal reaction to obtain a P-ZIF-8 / CaIn2S4 composite material.

[0047] In the present invention, the mixing preferably includes: first dissolving the P-ZIF-8 nanoparticles into a mixture of water and ethanol, then sequentially adding a water-soluble calcium source, a water-soluble indium source and thioacetamide, and stirring.

[0048] In the present invention, the volume ratio of water to ethanol is preferably 1:1-2, more preferably 1:1; the water is preferably deionized water; the water-soluble calcium source is preferably calcium nitrate and / or calcium chloride; and the water-soluble indium source is preferably indium chloride and / or indium nitrate. In the present invention, the molar ratio of Ca in the water-soluble calcium source, In in the water-soluble indium source, and thioacetamide is preferably 1:2:4-6, more preferably 1:2:5. In the present invention, the molar ratio of P-ZIF-8 nanoparticles to Ca in the water-soluble calcium source is preferably 0.05-0.2:1, more preferably 0.1-0.15:1.

[0049] In the present invention, the temperature of the hydrothermal reaction is preferably 80 to 180°C, more preferably 100 to 160°C, and even more preferably 120°C; the time of the hydrothermal reaction is preferably 12 to 32 hours, more preferably 18 to 26 hours, and even more preferably 24 hours. During the hydrothermal reaction, the P-ZIF-8 nanoparticles are deposited on the surface of CaIn2S4 to obtain CaIn2S4 microspheres loaded with P-ZIF-8.

[0050] In a specific embodiment of the present invention, the hydrothermal reaction is carried out in a polytetrafluoroethylene-lined reactor. In this specific embodiment, the polytetrafluoroethylene lining of the reactor is pretreated prior to the hydrothermal reaction. The pretreatment preferably includes the following steps: sequentially cleaning the polytetrafluoroethylene lining with aqua regia and deionized water, and drying the lining. The present invention has no particular requirements for the cleaning method; any cleaning method familiar to those skilled in the art can be used. In the present invention, the drying method is preferably air-drying.

[0051] In the present invention, after the hydrothermal reaction, the resulting product system is preferably subjected to solid-liquid separation, and the resulting solid is washed and dried to obtain a P-ZIF-8 / CaIn2S4 composite material. The present invention has no particular requirements for the washing method, and a washing method well known to those skilled in the art can be used, such as washing with a mixture of water and ethanol. The present invention has no particular requirements for the drying method, and a drying method well known to those skilled in the art can be used, such as air drying.

[0052] The present invention provides the use of the P-ZIF-8 / CaIn2S4 composite material described in the above scheme or the P-ZIF-8 / CaIn2S4 composite material prepared by the preparation method described in the above scheme as a photocatalyst in photocatalytic water decomposition to produce hydrogen.

[0053] The P-ZIF-8 / CaIn2S4 composite material provided by the present invention, its preparation method and application are described in detail below in conjunction with the embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] (1) Preparation of ZIF-8 nanoparticles: 1.7949 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1.9704 g of dimethylimidazole (2-MeIm) were weighed and dispersed in 80 mL of anhydrous methanol to form a precursor solution. The solution was stirred for 12 h for coordination reaction, centrifuged, washed with anhydrous methanol, and dried in vacuum at 60°C overnight to obtain ZIF-8.

[0056] (2) Preparation of P-ZIF-8 nanoparticles: Weigh 4.0 g of sodium hypophosphite monohydrate (NaH2PO2·H2O) and 0.8 g of ZIF-8 prepared in step (1) and place them in porcelain boats A and B, respectively. Place the quartz boats A and B in the upstream and downstream of a tube furnace and calcine them at high temperature in a nitrogen inert atmosphere at a heating rate of 5°C / min from room temperature to 400°C. Keep the temperature for 60 min, cool naturally, and collect the sample in porcelain boat B to obtain P-ZIF-8 nanoparticles.

[0057] (3) Preparation of P-ZIF-8 / CaIn2S4 composite photocatalyst: 0.0794 g of P-ZIF-8 prepared in step (2) was weighed and dissolved in a mixed solution of 30 mL of deionized water and 30 mL of ethanol, and 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), and 0.6010 g of thioacetamide (TAA) were added in sequence. After continuous stirring for 30 min, the mixed solution described in this step was transferred to a polytetrafluoroethylene-lined reactor, heated at 120°C for 24 h, and naturally cooled to obtain a precipitate. The precipitate obtained in this step was then washed and centrifuged. After separation, it was vacuum-dried at 60°C overnight to obtain a P-ZIF-8 / CaIn2S4 composite material, wherein the loading amount of P-ZIF-8 nanoparticles in the composite material was 10 wt%.

[0058] The ZIF-8, P-ZIF-8 nanoparticles and P-ZIF-8 / CaIn2S4 composite materials described in Example 1 were tested using a scanning electron microscope. The obtained SEM images are shown in FIG. Figure 1 、 Figure 2 、 Figure 3 As shown. Figure 1 、 Figure 2 and Figure 3 Phosphating treatment increases the surface roughness and specific surface area of ZIF-8. The morphology of the P-ZIF-8 / CaIn2S4 composite material is primarily due to the uniform loading of P-ZIF-8 particles on the CaIn2S4 surface. Phosphating ZIF-8 also exhibits a larger specific surface area, forming a heterojunction with CaIn2S4 through surface-interface interaction, which expands the visible light absorption region.

[0059] The BJH test of P-ZIF-8 / CaIn2S4 composite photocatalyst was carried out, and the results are shown in Figure 8 , showing that the average pore size of the P-ZIF-8 / CaIn2S4 composite photocatalyst is 21.48 nm.

[0060] Example 2

[0061] (1) Preparation of ZIF-8 nanoparticles: 1.7949 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1.9704 g of dimethylimidazole (2-MeIm) were weighed and dispersed in 80 mL of anhydrous methanol to form a precursor solution. The solution was stirred for 12 h for coordination reaction, centrifuged, washed with anhydrous methanol, and dried in vacuum at 60°C overnight to obtain ZIF-8.

[0062] (2) Preparation of P-ZIF-8 nanoparticles: Weigh 5.0 g of sodium hypophosphite monohydrate (NaH2PO2·H2O) and 0.5 g of ZIF-8 prepared in step (1) and place them in porcelain boats A and B, respectively. Place the quartz boats A and B in the upstream and downstream of a tube furnace and calcine them at high temperature in a nitrogen inert atmosphere at a heating rate of 5°C / min from room temperature to 400°C. Keep the temperature for 60 min, cool naturally, and collect the sample in porcelain boat B to obtain P-ZIF-8 nanoparticles.

[0063] (3) Preparation of P-ZIF-8 / CaIn2S4 composite material: 0.1588 g of P-ZIF-8 nanoparticles prepared in step (2) were weighed and dissolved in a mixed solution of 30 mL of deionized water and 30 mL of ethanol, and 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), and 0.6010 g of thioacetamide (TAA) were added in sequence. After continuous stirring for 30 min, the mixed solution obtained in this step was transferred to a polytetrafluoroethylene-lined reactor, heated at 120°C for 24 h, and naturally cooled to obtain a precipitate. The precipitate in this step was then washed and centrifuged. After separation, it was vacuum-dried at 60°C overnight to obtain a P-ZIF-8 / CaIn2S4 composite material, wherein the loading amount of P-ZIF-8 nanoparticles in the composite material was 20 wt%.

[0064] The P-ZIF-8, P-ZIF-8 nanoparticles, and P-ZIF-8 / CaIn2S4 composite materials were subjected to XRD tests, and the obtained XRD diffraction patterns were as follows: Figure 4 、 Figure 5 As shown. Figure 4 It can be seen that the crystal phase of the original MOFs did not change before and after phosphating. Figure 5 It can be seen that the XRD peaks appear at 27.4°, 47.7°, 33.1°, and 43.5°, corresponding to (311), (440), (400), and (511) (PDF#31-0272), indicating that the present invention successfully obtained the P-ZIF-8 / CaIn2S4 composite material through phosphating treatment.

[0065] Example 3

[0066] (1) Preparation of ZIF-8 nanoparticles: 1.7949 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1.9704 g of dimethylimidazole (2-MeIm) were weighed and dispersed in 80 mL of anhydrous methanol to form a precursor solution. The solution was stirred for 12 h for coordination reaction, centrifuged, washed with anhydrous methanol, and dried in vacuum at 60°C overnight to obtain ZIF-8.

[0067] (2) Preparation of P-ZIF-8 nanoparticles: 6.0 g of sodium hypophosphite monohydrate (NaH2PO2·H2O) and 0.3 g of ZIF-8 prepared in step (1) were weighed and placed in porcelain boats A and B, respectively. The quartz boats A and B described in this step were placed in the upstream and downstream of a tube furnace, and calcined at high temperature under a nitrogen inert atmosphere, with the temperature rising from room temperature to 400°C at a heating rate of 5°C / min, and kept warm for 60 min. After natural cooling, the sample in porcelain boat B was collected to obtain P-ZIF-8 nanoparticles;

[0068] (3) Preparation of P-ZIF-8 / CaIn2S4 composite material: 0.2382 g of P-ZIF-8 prepared in step (2) was weighed and dissolved in a mixed solution of 30 mL of deionized water and 30 mL of ethanol, and 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), and 0.6010 g of thioacetamide (TAA) were added in sequence. After continuous stirring for 30 min, the mixed solution obtained in this step was transferred to a polytetrafluoroethylene-lined reactor, heated at 120°C for 24 h, and naturally cooled to obtain a precipitate. The precipitate obtained in this step was then washed and centrifuged. After separation, it was vacuum-dried at 60°C overnight to obtain a P-ZIF-8 / CaIn2S4 composite material, wherein the loading amount of P-ZIF-8 nanoparticles in the composite material was 30 wt%.

[0069] Comparative Example 1

[0070] (1) Preparation of ZIF-8 nanoparticles: 1.7949 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and 1.9704 g of dimethylimidazole (2-MeIm) were weighed and dispersed in 80 mL of anhydrous methanol to form a precursor solution. The solution was stirred for 12 h for coordination reaction, centrifuged, washed with anhydrous methanol, and dried in vacuum at 60°C overnight to obtain ZIF-8 nanoparticles.

[0071] (2) Preparation of ZIF-8 / CaIn2S4 composite material: 0.0794 g ZIF-8 prepared in step (2) was weighed and dissolved in a mixed solution of 30 mL deionized water and 30 mL ethanol, and 0.2904 g calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g indium nitrate pentahydrate (In(NO3)3·5H2O), and 0.6010 g thioacetamide (TAA) were added in sequence. After continuous stirring for 30 min, the obtained mixed solution was transferred to a polytetrafluoroethylene-lined reactor, heated at 120°C for 24 h, and naturally cooled to obtain a precipitate. The precipitate of this step was then washed and centrifuged. After separation, it was vacuum-dried at 60°C overnight to obtain a ZIF-8 / CaIn2S4 composite material, wherein the loading amount of ZIF-8 nanoparticles in the composite material was 10 wt%.

[0072] Comparative Example 2

[0073] Preparation of CaIn2S4 photocatalyst: In a mixed solution of 30 mL of deionized water and 30 mL of ethanol, 0.2904 g of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O), 1.2033 g of indium nitrate pentahydrate (In(NO3)3·5H2O), and 0.6010 g of thioacetamide (TAA) were added in sequence. After continuous stirring for 30 minutes, the obtained mixed solution was transferred to a polytetrafluoroethylene-lined reactor and heated at 120°C for 24 hours. After natural cooling, a precipitate was obtained. The precipitate of this step was then washed and centrifuged. After separation, it was vacuum-dried at 60°C overnight to obtain a CaIn2S4 photocatalyst.

[0074] The CaIn2S4 photocatalyst of Comparative Example 2 was subjected to BJH test, and the results are shown in Figure 8 ,As can be seen from the figure, the average pore size of the CaIn2S4 photocatalyst is 10.94nm.

[0075] The P-ZIF-8 nanoparticles of Example 1, the composite materials of Examples 1 to 3 and Comparative Example 1, and the CaIn2S4 of Comparative Example 2 were used as photocatalysts for photocatalytic hydrogen production tests. The photocatalytic hydrogen production test method comprises the following steps: dispersing 50 mg of the photocatalyst in a mixed solution containing 10 mL of triethanolamine and 40 mL of deionized water; placing the mixed solution in a photocatalytic reaction device, cooling it with circulating water to maintain the system temperature at 5°C, and using a vacuum pump to evacuate for 30 minutes to remove the dissolved air, then turning on a 300W xenon lamp (CEL-HXF 300-T3) to irradiate the photocatalytic reaction device containing the mixed solution from the top, and at the same time adjusting the magnetic stirring to ensure that the catalyst is evenly dispersed, and using a gas chromatograph (GC-7920-TF2A) equipped with a TCD detector to detect the generated H2 gas online. The specific test results are shown in Table 1, where the time-hydrogen production curves obtained in Example 1 and Comparative Examples 1 to 2 are shown in FIG. Figure 6 and Figure 7 As shown, Figure 6 Corresponding to Example 1 and Comparative Example 2 and P-ZIF-8 nanoparticles, Figure 7 Corresponding ratio 1.

[0076] Depend on Figure 6 It can be seen that the P-ZIF-8 / CaIn2S4 composite photocatalyst has good photocatalytic hydrogen production activity, among which the 10%-P-ZIF-8 / CaIn2S4 photocatalyst can produce 2129.73μmol / g of hydrogen in 2 hours under full-spectrum visible light. At the same time, the ternary composite photocatalyst prepared by the present invention has an 11-fold increase in photocatalytic hydrogen production compared to the original CaIn2S4, which is much higher than the catalytic performance of the existing CaIn2S4-based composite photocatalyst. Figure 7 It can be seen that the hydrogen production performance of the prepared ZIF-8 / CaIn2S4 composite photocatalyst is far inferior to that of the P-ZIF-8 / CaIn2S4 composite photocatalyst after phosphating. This is because during the phosphating process, sodium hypophosphite decomposes to produce PH3, breaking Zn-N bonds and forming Zn-P bonds, converting ZIF-8 into P-ZIF-8 nanoparticles. These particles interact strongly with CaIn2S4 through the surface interface, forming a heterojunction. This accelerates the separation and transport of photogenerated carriers, significantly increasing hydrogen evolution yields and demonstrating excellent catalytic performance.

[0077] Table 1 Hydrogen evolution yield (μmol / g) of Examples and Comparative Examples under full spectrum visible light for 2 h

[0078] P-ZIF-8 nanoparticles Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 0 2129.73 1730.59 1608.64 1399.63 0

[0079] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A P-ZIF-8 / CaIn2S4 composite material, comprising CaIn2S4 microspheres and P-ZIF-8 nanoparticles deposited on the CaIn2S4 microspheres, wherein the P-ZIF-8 nanoparticles are P-doped ZIF-8 nanoparticles.

2. The P-ZIF-8 / CaIn2S4 composite material according to claim 1, wherein The molar ratio of the P-ZIF-8 nanoparticles to the CaIn2S4 microspheres is 0.05-0.2:

1.

3. The P-ZIF-8 / CaIn2S4 composite material according to claim 1 or 2, characterized in that The average pore diameter of the P-ZIF-8 / CaIn2S4 composite material is 20-22 nm.

4. A method for preparing the P-ZIF-8 / CaIn2S4 composite material according to any one of claims 1 to 3, comprising the following steps: An inorganic water-soluble zinc source and dimethylimidazole are dispersed in anhydrous methanol, subjected to coordination reaction, and solid-liquid separation to obtain ZIF-8; Co-calcining the ZIF-8 and a phosphorus source to obtain P-ZIF-8 nanoparticles; The P-ZIF-8 nanoparticles, water, ethanol, a water-soluble calcium source, a water-soluble indium source and thioacetamide are mixed and subjected to a hydrothermal reaction to obtain a P-ZIF-8 / CaIn2S4 composite material.

5. The preparation method according to claim 4, characterized in that The molar ratio of zinc ions to dimethylimidazole in the inorganic water-soluble zinc source is 1:2-6; and the concentration of the inorganic water-soluble zinc source in anhydrous methanol is 0.01-0.1 mol / L.

6. The preparation method according to claim 4, characterized in that The phosphorus source includes sodium hypophosphite; the mass ratio of the phosphorus source to ZIF-8 is 5-30:1-1.

5.

7. The preparation method according to claim 4 or 6, characterized in that: The co-calcination temperature is 200-400° C., and the heat preservation time is 60-240 minutes; and the co-calcination is carried out in a nitrogen atmosphere.

8. The preparation method according to claim 4, characterized in that The molar ratio of Ca in the water-soluble calcium source, In in the water-soluble indium source and thioacetamide is 1:2:4-6; the molar ratio of the P-ZIF-8 nanoparticles to Ca in the water-soluble calcium source is 0.05-0.2:

1.

9. The preparation method according to claim 4 or 8, characterized in that The temperature of the hydrothermal reaction is 100-180° C., and the time is 12-32 hours.

10. Use of the P-ZIF-8 / CaIn2S4 composite material according to any one of claims 1 to 3 or the P-ZIF-8 / CaIn2S4 composite material prepared by the preparation method according to any one of claims 4 to 9 as a photocatalyst in photocatalytic water decomposition to produce hydrogen.

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