A sulfogallium zinc copper / titanium dioxide composite photocatalyst and a preparation method and application thereof

Abstract

The application discloses a kind of sulfur gallium zinc copper / titanium dioxide composite photocatalyst and its preparation method and application, belong to inorganic catalyst preparation field, preparation method is to Cu (dedtc) 2, Ga (dedtc) 3, Zn (dedtc) 2, TiO2 and oleylamine, n-dodecanethiol, and 1-octadecene are added to reaction container, reaction liquid is heated to 90-120 DEG C and preheated, under preheating temperature, vacuum is extracted for 10~30min;Then temperature is raised to 200~280 DEG C, under N2 atmosphere, reaction is 0.5~1.5h, after cooling, with n-hexane ultrasonic washing, after drying, sulfur gallium zinc copper / titanium dioxide composite photocatalyst is obtained.The composite photocatalyst prepared by the application has good photocatalytic activity and stability.

Description

Technical Field

[0001] The present invention belongs to the field of inorganic catalyst preparation, and specifically relates to a sulfur gallium zinc copper / titanium dioxide composite photocatalyst and a preparation method and application thereof. Background Art

[0002] Traditional hydrogen production technology relies on fossil fuel reforming or water electrolysis, which has high energy consumption or carbon emission problems and is difficult to meet the needs of green and low-carbon development. Photocatalytic water decomposition to produce hydrogen has become a frontier direction in global energy research because of its direct use of solar visible light to drive chemical reactions, mild reaction conditions and environmental friendliness. Photocatalytic water decomposition to produce hydrogen is achieved by semiconductor photocatalysts absorbing solar energy, exciting the generation of electron-hole pairs, and then inducing the decomposition of water to produce hydrogen. In theory, "zero-carbon" energy conversion can be achieved. However, existing photocatalytic systems still face problems such as low quantum efficiency, high charge recombination rate and catalyst instability. Therefore, there is an urgent need to develop new photocatalyst materials with wide spectral response, efficient carrier separation ability and long-term stability.

[0003] In recent years, the performance of photocatalysts has been significantly improved through strategies such as heterogeneous structure construction, material surface engineering, and defect doping. Further optimization of photocatalytic hydrogen production systems has important scientific significance and application value for achieving carbon neutrality and sustainable development.

[0004] Multinary copper-based chalcogenides have been widely used in the field of photocatalytic hydrogen production due to their excellent visible light absorption properties and environmental friendliness. In the past few decades, copper-based semiconductor nanocrystals and their derivatives have attracted considerable research interest. Compared with toxic heavy metal-based semiconductors, copper-based materials are naturally abundant, low-cost and non-toxic. The optimal band gap of copper-based metal sulfides has a good absorption coefficient for sunlight and excellent photocatalytic performance. This makes copper-based metal sulfides one of the most advantageous choices for applications such as solar energy conversion and photocatalysis. In particular, CuZnInS and CuZnGaS have the advantages of adjustable band gap, good thermal and chemical stability, and environmental friendliness, making them ideal materials for solar energy to hydrogen energy conversion.

[0005] The photocatalytic activity of TiO2 originates from the generation of electron-hole pairs by photoexcitation. Upon absorbing photons with energy above the band gap, electrons in the valence band (VB) transition to the conduction band (CB), forming highly active electrons and holes that drive the oxidation and reduction reactions in photocatalysis, respectively. As a typical photocatalytic semiconductor material, TiO2 has become a classic material in photocatalysis due to its stable chemical properties, corrosion resistance, non-toxicity, low cost, and widespread application in solar energy conversion, air / water purification, and self-cleaning materials. TiO2 has found widespread application in energy, environmental management, and industrial catalysis. TiO2 oxidizes water molecules (H2O) to produce oxygen (O2) through photogenerated holes, while electrons reduce protons to produce H2. TiO2 photocatalytic systems can be integrated into solar cells and hydrogen fuel cells for renewable energy storage. In wastewater treatment and air purification, TiO2 can simultaneously degrade organic pollutants and produce hydrogen. The combination of TiO2 photocatalytic organic synthesis and CO2 reduction offers a new path for green chemical engineering. However, the wide band gap of TiO2 means that it can only absorb ultraviolet light, and the rapid recombination of electron-hole pairs also seriously restricts its quantum efficiency.

[0006] Therefore, the core issue of current research is how to improve the efficiency and stability of photocatalysts through modification. Summary of the Invention

[0007] The present invention provides a sulfur gallium zinc copper / titanium dioxide composite photocatalyst and its preparation method and application. The sulfur gallium zinc copper / titanium dioxide composite photocatalyst synthesized by the present invention not only has good photocatalytic water decomposition hydrogen production performance, but also has good stability.

[0008] A method for preparing a sulfur gallium zinc copper / titanium dioxide composite photocatalyst comprises the following steps: Step 1, preparing Cu(dedtc)2, Ga(dedtc)3, and Zn(dedtc)2; Step 2, preparing a sulfur gallium zinc copper / titanium dioxide (CuZnGaS / TiO2) composite photocatalyst material: pouring Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2 and TiO2 into a three-necked flask, and then adding oleylamine (C 18 H 37 N), n-dodecyl mercaptan (C 12 H 26 S) and 1-octadecene (C 18 H 36) is poured in; first, preheat the reaction solution to 90-120°C on a heating mantle, evacuate at the preheating temperature for 10-30 minutes, then raise the temperature to 200-280°C, and react under a N2 atmosphere for 0.5-1.5 hours; finally, wait for the reaction solution to cool naturally. The mixture is ultrasonically washed with n-hexane, and the obtained solid is placed in a vacuum drying oven and dried to obtain a CuZnGaS / TiO2 composite photocatalyst material; preferably, in step 1, the preparation method of copper diethyldithiocarbamate Cu(dedtc)2 is as follows: sodium diethyldithiocarbamate is dissolved in deionized water to obtain a ligand sodium salt solution; copper nitrate trihydrate is dissolved in deionized water to obtain a copper nitrate solution; then, the copper nitrate solution is slowly added to the ligand sodium salt solution through a constant pressure dropping funnel, and stirred under magnetic stirring conditions; after the reaction is completed, the mixture is centrifuged to collect the precipitated product, and the product is ultrasonically washed with deionized water and ethanol in turn, and the obtained solid is placed in a vacuum drying oven and dried to obtain copper diethyldithiocarbamate (Cu(dedtc)2).

[0009] Gallium diethyldithiocarbamate (Ga(dedtc)3) and Zn(dedtc)2 are prepared using the same method as Cu(dedtc)2. Gallium nitrate trihydrate and zinc nitrate hexahydrate are replaced with copper nitrate trihydrate, and the gallium salt Ga(dedtc)3 and zinc salt Zn(dedtc)2 are prepared using the same method.

[0010] Preferably, in step 1: 15-200 mmol of sodium diethyldithiocarbamate is dissolved in 200-1000 mL of deionized water to obtain a ligand sodium salt solution; 10-50 mmol of copper nitrate trihydrate is dissolved in 200-1000 mL of deionized water to obtain a copper nitrate solution; the magnetic stirring time is 1-1.5 hours; the number of ultrasonic washings using deionized water is 2 to 4 times; the drying temperature is 60° C., and the drying time is 10-20 hours.

[0011] Preferably, in step 2: Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2, TiO2, C 18 H 37 N (oleylamine), C 12 H 26 S (n-dodecyl mercaptan) and C 18 H 36 The dosage ratio of (1-octadecene) is (0.25-1.00) mmol: (0.25-1.00) mmol: (1.00-5.00) mmol: (9-90) mg: (8-40) mL: (8-40) mL: (4-20) mL.

[0012] Preferably, in step 2: during ultrasonic washing with n-hexane, the washing times are 2 to 4 times; the drying temperature is 60° C., and the drying time is 10 to 20 hours.

[0013] The sulfur gallium zinc copper / titanium carbide composite material prepared by the present invention can be used for photocatalytic decomposition of water to produce hydrogen.

[0014] Beneficial Effects: This invention utilizes a simple one-step hydrothermal method and an in-situ growth composite strategy to load sulfur gallium zinc copper nanorods onto titanium dioxide nanoparticles, resulting in a sulfur gallium zinc copper / titanium dioxide composite photocatalyst material. The Z-shaped heterojunction formed at the interface of sulfur gallium zinc copper and titanium dioxide effectively improves the separation efficiency of electrons and holes, reduces the probability of recombination of photogenerated electron-hole pairs, and thus enhances redox reactions, exhibiting excellent photocatalytic activity and stability, and significantly reducing photocorrosion. This composite photocatalytic material exhibits photocatalytic properties and has been successfully used for the photocatalytic decomposition of water to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Field emission scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) images of the sample prepared in Example 2;

[0016] Figure 2 XRD pattern and XPS pattern of the sample prepared in Example 2;

[0017] Figure 3 The UV-visible diffuse reflectance spectrum and energy band structure diagram prepared in Example 2;

[0018] Figure 4 Electrochemical impedance spectroscopy (EIS), transient photocurrent, photoluminescence (PL), and time-resolved photoluminescence (TRPL) test graphs prepared in Example 2;

[0019] Figure 5 This is a diagram of the photocatalytic performance, apparent quantum efficiency and stability prepared in Example 2. DETAILED DESCRIPTION

[0020] The technical solutions of the present invention are described in detail below through examples, but the protection scope of the present invention is not limited to the examples.

[0021] Example 1: Step 1, preparation of Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2 materials: Sodium diethyldithiocarbamate (C5H 10NNaS2·3H2O, 30 mmol) and copper nitrate trihydrate (Cu(NO3)2·3H2O, 10 mmol) were dissolved in 200 mL of deionized water. The copper nitrate solution was then slowly added to the ligand sodium salt solution via a constant pressure dropping funnel and stirred under magnetic stirring for 1 hour. After the reaction, the mixture was centrifuged at 9000 rpm for 10 minutes to collect the precipitated product. The product was ultrasonically washed four times with deionized water and once with ethanol. The resulting solid was dried in a vacuum drying oven at 60°C for 12 hours to obtain the copper salt Cu(dedtc)2. By replacing copper nitrate trihydrate with gallium nitrate trihydrate and zinc nitrate hexahydrate, Ga(dedtc)3 and Zn(dedtc)2 were prepared.

[0022] Step 2, preparation of CuZnGaS / TiO2 composite photocatalyst material: Pour Cu(dedtc)2 (0.25mmol), Ga(dedtc)3 (0.25mmol), Zn(dedtc)2 (1mmol) and TiO2 (10mg) into a three-necked flask, and then add oleylamine (C 18 H 37 N, 8 mL), n-dodecyl mercaptan (C 12 H 26 S, 8 mL) and 1-octadecene (C 18 H 36 ,4 mL) was poured into the mixture. The reaction solution was first preheated to 100°C on a heating mantle and evacuated at this temperature for 20 minutes. The reaction temperature was then raised to 250°C at a rate of 10°C / min and maintained under a nitrogen atmosphere for 1 hour. The reaction solution was allowed to cool naturally. Ultrasonic washing with n-hexane was performed four times, and the resulting solid was dried in a vacuum drying oven at 60°C for 12 hours. The resulting product was designated CuZnGaS / TiO2.

[0023] Example 2: Step 1, preparation of Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2 materials: sodium diethyldithiocarbamate (C5H 10 NNaS2·3H2O, 40 mmol) and copper nitrate trihydrate (Cu(NO3)2·3H2O, 10 mmol) were dissolved in 400 mL of deionized water. The copper nitrate solution was then slowly added to the ligand sodium salt solution via a constant pressure dropping funnel and stirred under magnetic stirring for 1 hour. After the reaction, the mixture was centrifuged at 9000 rpm for 10 minutes to collect the precipitated product. The product was ultrasonically washed four times with deionized water and once with ethanol. The resulting solid was dried in a vacuum drying oven at 60°C for 12 hours to obtain the copper salt Cu(dedtc)2. Gallium salt Ga(dedtc)3 and zinc salt Zn(dedtc)2 were prepared by replacing copper nitrate trihydrate with gallium nitrate trihydrate and zinc nitrate hexahydrate.

[0024] Step 2, preparation of CuZnGaS / TiO2 composite photocatalyst material: Pour Cu(dedtc)2 (0.5mmol), Ga(dedtc)3 (0.5mmol), Zn(dedtc)2 (4mmol) and TiO2 (20mg) into a three-necked flask, then add oleylamine (C 18 H 37 N, 16 mL), n-dodecyl mercaptan (C 12 H 26 S, 16 mL) and 1-octadecene (C 18 H 36 , 8 mL) was poured into the mixture. The reaction solution was preheated to 100°C on a heating mantle and evacuated at this temperature for 20 minutes. The reaction temperature was then raised to 250°C at a rate of 10°C / min and maintained under a nitrogen atmosphere for 1 hour. The reaction solution was allowed to cool naturally. Ultrasonic washing with n-hexane was performed four times, and the resulting solid was dried in a vacuum drying oven at 60°C for 12 hours. The resulting product was designated CuZnGaS / TiO2.

[0025] Example 3: Step 1, preparation of Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2 materials: Sodium diethyldithiocarbamate (C5H 10 NNaS2·3H2O, 15 mmol) and copper nitrate trihydrate (Cu(NO3)2·3H2O, 15 mmol) were dissolved in 300 mL of deionized water. The copper nitrate solution was then slowly added to the ligand sodium salt solution via a constant pressure dropping funnel and stirred under magnetic stirring for 1 hour. After the reaction, the mixture was centrifuged at 9000 rpm for 10 minutes to collect the precipitated product. The product was ultrasonically washed three times with deionized water and once with ethanol. The resulting solid was dried in a vacuum drying oven at 60°C for 12 hours to obtain the copper salt (Cu(dedtc)2). Gallium salt Ga(dedtc)3 and zinc salt Zn(dedtc)2 were prepared by replacing copper nitrate trihydrate with gallium nitrate trihydrate and zinc nitrate hexahydrate.

[0026] Step 2, preparation of CuZnGaS / TiO2 composite photocatalyst material: Pour Cu(dedtc)2 (1mmol), Ga(dedtc)3 (1mmol), Zn(dedtc)2 (1.2mmol) and TiO2 (12.5mg) into a three-necked flask, and then add oleylamine (C 18 H 37 N, 5mL), n-dodecyl mercaptan (C 12 H 26 S, 5 mL) and 1-octadecene (C18 H 36 , 4.8 mL) was poured into the reaction mixture. The reaction solution was preheated to 110°C on a heating mantle and evacuated at this temperature for 30 minutes. The reaction temperature was then raised to 260°C at a rate of 10°C / min and maintained under a nitrogen atmosphere for 1.5 hours. The reaction solution was allowed to cool naturally. Ultrasonic washing was performed twice with n-hexane, and the resulting solid was dried in a vacuum drying oven at 60°C for 12 hours. The resulting product was designated CuZnGaS / TiO2.

[0027] There is no obvious difference in the structure of the products prepared in Examples 1-3, but there are great differences in the performance of the products. Example 1 has the best performance, Example 2 is the second best, and Example 3 has the worst performance.

[0028] Replacing TiO2 in step 2 of Example 2 with 0 to obtain CuZnGaS; replacing TiO2 in step 2 of Example 2 with 9.375 mg to obtain CuZnGaS / TiO2 with 9.1 wt % TiO2; replacing TiO2 in step 2 of Example 2 with 10.7 mg to obtain CuZnGaS / TiO2 with 12.5 wt % TiO2; replacing TiO2 in step 2 of Example 2 with 12.5 mg to obtain CuZnGaS / TiO2 with 14.3 wt % TiO2; replacing TiO2 in step 2 of Example 2 with 13.125 mg to obtain CuZnGaS / TiO2 with 16.7 wt % TiO2; replacing TiO2 in step 2 of Example 2 with 13.65 mg to obtain CuZnGaS / TiO2 with 17.5 wt % TiO2; replacing TiO2 in step 2 of Example 2 with 15 mg to obtain 18.2 wt % TiO2 TiO2 in step 2 of Example 2 was replaced by 37.5 mg to obtain 20 wt% TiO2 of CuZnGaS / TiO2; TiO2 in step 2 of Example 2 was replaced by 75 mg to obtain 50 wt% TiO2 of CuZnGaS / TiO2.

[0029] Figure 1 These are the scanning electron microscope and EDS elemental analysis images of the samples prepared in Example 2, where a is the SEM image of CuZnGaS (abbreviated as CZGS), b is the scanning image of TiO2, c is the scanning image of 17.5 wt% CZGS / TiO2, and di is the elemental analysis image. Figure 1 The prepared CuZnGaS monomers are nanorod-shaped crystals with a length of 100-200 nm and a diameter of 20-30 nm. Figure 1 Figure b shows that TiO2 is a spherical particle with a diameter of 200-300nm. Figure 1Figure c shows that in the CuZnGaS / TiO2 composite photocatalyst material grown in situ by a one-pot hydrothermal method, the size of the TiO2 nanoparticles and the size of the CuZnGaS monomer nanorods remain unchanged. After hydrothermal synthesis, the CuZnGaS monomers attach to the surface of the TiO2 monomers. The CuZnGaS nanorods on the TiO2 surface are more dense, increasing the contact area between the two materials. The composite photocatalyst material has a larger specific surface area, providing more active sites, promoting the surface reaction of photogenerated carriers. The nanometer size also shortens the path for photogenerated charges to migrate from the bulk phase to the surface, reducing the probability of recombination. EDS elemental spectrum ( Figure 1 Figure (di) confirmed the existence and uniform distribution of O, Ti, S, Ga, Zn, and Cu elements contained in the CuZnGaS / TiO2 composite photocatalyst material, thereby indirectly verifying the successful construction of the CuZnGaS / TiO2 composite photocatalyst material.

[0030] Figure 2 X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) of the sample prepared in Example 2. Figure 2In Figure a, XRD analysis of pure CuZnGaS monomer shows that characteristic diffraction peaks are detected at 2θ values ​​of 26.90°, 28.50°, 30.52°, 39.61°, 47.56°, 51.77° and 56.39°, corresponding to the diffraction of (100), (002), (101), (102), (110), (103) and (112) crystal planes, respectively. The peaks of TiO2 nanoparticles at 25.3°, 37.8°, 48.0°, 53.9° and 55.1° correspond to the lattice planes of (101), (004), (200), (105) and (211), respectively, indicating that it is an anatase structure. Characteristic peaks of CuZnGaS and anatase phase TiO2 are observed in the CuZnGaS / TiO2 composite photocatalyst material, indicating that the crystal structures of both have not changed during the composite process. As the mass fraction of TiO2 increases (from 16.7% to 50%), the diffraction peak intensity of CuZnGaS in the composite material (such as 26.90° and 30.52°) gradually weakens, while the intensity of the characteristic peak of the (101) crystal plane of TiO2 (25.3°) gradually increases. This trend indicates that the crystallinity of CuZnGaS and TiO2 is directly related to their mass fractions, and the coexistence of the two does not induce the formation of new phases or lattice distortion. It is worth noting that the characteristic peak of TiO2 does not appear in the XRD pattern of the photocatalytic monomer (pure CuZnGaS), while the diffraction peak of TiO2 in the composite material gradually becomes more prominent with increasing content, but is not accompanied by a significant shift of the background peak of the matrix material (CuZnGaS), indicating that the composite of TiO2 and CuZnGaS does not destroy the integrity of its main lattice. The above results confirm that by regulating the mass ratio of TiO2 and CuZnGaS, the controllable recombination of photocatalytic active components can be achieved while maintaining the stability of the crystal structures of the two, providing a key structural basis for optimizing interfacial charge transport and photocatalytic performance. Figure 2 Figure b is the full XPS spectrum. The composite photocatalyst material is composed of Cu, Zn, Ga, S, Ti, and O elements, which corresponds to the previous EDS spectrum results. Figure 2 The ch in the middle is the spectrum of each element. The chemical state analysis of Ti element shows that TiO2 monomer presents typical Ti characteristic double peaks at binding energies of 464.1eV and 458.5eV, corresponding to Ti 2p 1 / 2 and Ti 2p 3 / 2 , and the CuZnGaS / TiO2 spectrum with 17.5 wt% TiO2 content shows that the original binding energy has a certain degree of positive shift relative to the TiO2 monomer, which are 465.2 eV (Ti 2p 1 / 2 ) and 459.4eV(Ti 2p 3 / 2The O 1s spectrum in the figure shows that the binding energy of CuZnGaS / TiO2 with 17.5 wt% TiO2 content also shows a certain degree of positive shift (from 529.7 eV to 532 eV) compared with TiO2 monomer. Analysis of the CuZnGaS component shows that there are two diffraction peaks in the Cu 2p spectrum. The two binding energies of Cu in CuZnGaS / TiO2 with 17.5 wt% TiO2 content are 931.6 eV and 951.9 eV, respectively, corresponding to Cu 2p 3 / 2 and Cu 2p 1 / 2 The two binding energies of Zn are 1021.4 eV and 1044.4 eV, corresponding to the Zn 2p 3 / 2 and Zn 2p 1 / 2 The two binding energies of Ga are 1144.0 eV and 1117.2 eV, corresponding to Ga 2p 1 / 2 and Ga 2p 3 / 2 The two binding energies of S are 162.6 eV and 161.2 eV, corresponding to S 2p 1 / 2 and S 2p 3 / 2 In contrast to TiO2, the XPS spectra of the four elements Cu, Zn, Ga, and S show that CuZnGaS / TiO2 with a TiO2 content of 17.5 wt% exhibits a certain degree of negative binding energy shift compared with CuZnGaS, indicating that there is a strong interaction between TiO2 and CuZnGaS. This phenomenon further provides a basis for the construction of the interface heterojunction of CuZnGaS / TiO2 composite photocatalyst materials.

[0031] Figure 3 The UV-visible diffuse reflectance spectrum and energy band structure diagram prepared in Example 2. Figure 3 As shown in Figure a, the absorption edge of TiO2 is around 400nm, while the absorption edges of CuZnGaS and CuZnGaS / TiO2 composite photocatalyst materials are around 550 and 600nm. The CuZnGaS / TiO2 composite photocatalyst material with a TiO2 content of 17.5 wt% exhibits a certain degree of red shift compared to the CuZnGaS monomer. The optical band gap of the material is narrowed, and the energy required for electron transitions within the photocatalyst material is reduced. XPS valence band spectrum analysis of CuZnGaS and TiO2 materials was performed to determine the valence band (VB) position, as shown in Figure 3. Figure 3 As shown in b, the valence band potential of CuZnGaS is +0.40eV, and the valence band potential of TiO2 is +2.20eV. The band gap (E g ) can be calculated by the following formula: ; α is the absorption coefficient, hν is the photon energy, λ is the wavelength, A is the absorbance, and n is an index related to the semiconductor transition type (direct bandgap semiconductor n=1 / 2, indirect bandgap semiconductor n=2). Figure c is the bandgap spectrum of CuZnGaS and TiO2 materials. The bandgap of CuZnGaS (E g ) is 2.62eV, and the band gap of TiO2 (E g ) is 3.20 eV. The conduction band (CB) position can be calculated from the band gap (Eg) and the valence band position (VB) according to the following formula: The calculated conduction band position of CuZnGaS is -2.22eV, while the conduction band position of TiO2 is -1.00eV.

[0032] Figure 4 Electrochemical impedance spectroscopy (EIS), transient photocurrent, photoluminescence (PL) and time-resolved photoluminescence (TRPL) tests of the sample prepared in Example 2. Figure 4 Figure a is the EIS graph of CuZnGaS, TiO2 and CuZnGaS / TiO2 composite photocatalyst materials, among which the impedance is the smallest because the unique crystal structure of TiO2 is conducive to the movement of electrons. After compounding TiO2, the arc radius of the photocatalyst material becomes smaller by about 40%. This result shows that its charge transfer resistance becomes smaller. The low impedance shows that the introduction of TiO2 significantly enhances the separation and transport of photogenerated electron-hole pairs in CuZnGaS. In addition, the charge transfer efficiency is improved and the probability of photogenerated electron-hole recombination is reduced, resulting in more charges moving to the interface to participate in the hydrogen evolution reaction. Figure 4 Figure b shows the transient photocurrent response of the three materials. All three materials exhibited relatively stable photocurrents over four cycles within 200 seconds. This stable photocurrent indicates that the separation and transport of electrons and holes during the photocatalytic process can proceed continuously. The photocurrent of the CuZnGaS / TiO2 composite photocatalyst material is significantly increased by approximately 2.2 times compared to that of CuZnGaS alone, indicating that the introduction of TiO2 inhibits photogenerated electron-hole recombination in the CuZnGaS material. A higher photocurrent density results in more photogenerated electrons and holes under illumination, thereby improving photocatalytic hydrogen production performance. This result is consistent with the EIS test results mentioned above. Figure c shows the time-resolved photoluminescence spectra (TRPL) of the three materials. The fluorescence lifetime of the composite photocatalyst material is significantly longer than that of the CuZnGaS alone. Figure d is the steady-state fluorescence spectra of the two materials. Obviously, compared with CuZnGaS monomer, the CuZnGaS / TiO2 composite photocatalyst material undergoes significant PL quenching, which indicates that the loading of TiO2 promotes charge transfer at the interface and effectively inhibits the recombination of photogenerated electrons and holes, which is beneficial to the photocatalytic decomposition of water to produce hydrogen.

[0033] Figure 5The photocatalytic performance, apparent quantum efficiency and stability of the sample prepared in Example 2 are shown in FIG. Figure 5 Figure a shows the time-dependent photocatalytic hydrogen production performance of CuZnGaS, TiO2, and CuZnGaS / TiO2 composite photocatalyst materials with different mass fractions of TiO2. Because TiO2 photoexcitation requires ultraviolet light energy, its photocatalytic performance under visible light is extremely weak, resulting in a hydrogen production efficiency of 0. The photocatalytic performance of CuZnGaS monomer is relatively weak, at 1.3630 mmol·g -1 ·h -1 The CuZnGaS / TiO2 composite photocatalyst with 17.5wt% TiO2 content in the composite material has the best hydrogen production performance, which is 4.6673 mmol·g -1 · h -1 , which is 3.43 times that of pure CuZnGaS monomer. Figure 5 Figure b is a bar graph of the photocatalytic hydrogen production rate of CuZnGaS, TiO2, and CuZnGaS / TiO2 composite photocatalyst materials with different mass fractions of TiO2. Starting from 9.1 wt% TiO2, as the TiO2 content increases, the photocatalytic performance also gradually increases until the best performance is the CuZnGaS / TiO2 composite photocatalyst material with 17.5 wt% TiO2 content. After 17.5 wt% TiO2, the photocatalytic activity of the composite material gradually decreases. This may be because the excess TiO2 monomer covers the CuZnGaS monomer, resulting in the inability of photogenerated electrons to migrate to the surface of the CuZnGaS monomer in time, but instead rapidly accumulates inside the TiO2 and then recombines with holes. Finally, the apparent quantum efficiency of the CuZnGaS / TiO2 composite photocatalyst material with 17.5 wt% TiO2 content at different wavelengths and the corresponding hydrogen evolution amount are shown as follows: Figure 5 As shown in Figure c, the apparent quantum efficiency of the material is consistent with the trend of the UV-visible absorption spectrum. The AQE value of the composite photocatalyst material at a wavelength of 365nm is 0.140905%. As the wavelength increases, the AQE value gradually decreases and the amount of hydrogen evolution also decreases. The stability of the photocatalyst material is one of the important reference standards for measuring the quality of the photocatalyst. Figure 5As shown in Figure d, after four cycles, the photocatalytic activity of the CuZnGaS / TiO2 composite photocatalyst material with a 17.5 wt% TiO2 content showed no significant decrease. After 20 hours of photocatalytic hydrogen production, it still maintained 91.6% photocatalytic activity. Compared to 72.0% for CuZnGaS alone, the stability of the photocatalyst material was significantly improved after the TiO2 composite was added. The high chemical stability of TiO2 effectively delayed the photocorrosion of CuZnGaS. In addition, the Z-type heterojunction structure of CuZnGaS / TiO2 promoted the separation of photogenerated electrons and holes, reduced the accumulation of holes on the CuZnGaS surface, and effectively suppressed the photocorrosion caused by hole oxidation, thereby greatly improving the stability.

[0034] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes may be made to the form and details without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a sulfur gallium zinc copper / titanium dioxide composite photocatalyst, characterized in that: The method comprises the following steps: step 1, preparing Cu(dedtc)2, Ga(dedtc)3, and Zn(dedtc)2; step 2, adding Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2, TiO2, oleylamine, n-dodecanethiol, and 1-octadecene into a reaction container, heating the reaction liquid to 90-120°C for preheating, and evacuating the reaction liquid at the preheating temperature for 10-30 minutes; then heating the reaction liquid to 200-280°C, reacting the reaction liquid in an N2 atmosphere for 0.5-1.5 hours, cooling the reaction liquid, ultrasonically washing the reaction liquid with n-hexane, and drying the reaction liquid to obtain a sulfur gallium zinc copper / titanium dioxide composite photocatalyst.

2. The preparation method according to claim 1, characterized in that The preparation method of Cu(dedtc)2 in step 1 is: dissolving sodium diethyldithiocarbamate in deionized water to obtain a ligand sodium salt solution; dissolving copper nitrate trihydrate in deionized water to obtain a copper nitrate solution; dropping the copper nitrate solution into the ligand sodium salt solution, stirring for a period of time, and after the reaction is completed, centrifuging and collecting the precipitated product, washing, and drying to obtain Cu(dedtc)2.

3. The preparation method according to claim 2, characterized in that In the preparation method of Cu(dedtc)2, the molar ratio of sodium diethyldithiocarbamate and copper nitrate trihydrate is (15-200): (10-50).

4. The preparation method according to claim 2, characterized in that In the preparation method of Cu(dedtc)2: when the copper nitrate solution is dropped into the ligand sodium salt solution, a constant pressure dropping funnel is used for dropwise addition; the stirring method is magnetic stirring, and the stirring time is 1-1.5 hours; the drying temperature is 60°C, and the drying time is 10-20 hours.

5. The preparation method according to claim 1, characterized in that In step 2, the usage ratio of Cu(dedtc)2, Ga(dedtc)3, Zn(dedtc)2, TiO2, oleylamine, n-dodecanethiol, and 1-octadecene is (0.25-1.00) mmol: (0.25-1.00) mmol: (1.00-5.00) mmol: (9-90) mg: (8-40) mL: (8-40) mL: (4-20) mL.

6. The preparation method according to claim 1, characterized in that In step 2, the drying temperature is 60° C. and the drying time is 10-20 hours.

7. A sulfur gallium zinc copper / titanium dioxide composite photocatalyst prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the sulfur gallium zinc copper / titanium dioxide composite photocatalyst according to claim 7 in the photocatalytic decomposition of water to produce hydrogen.

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