Copper sulfide / nickel titanate composite photocatalytic material as well as preparation method and application thereof

Abstract

The invention discloses a copper sulfide / nickel titanate composite photocatalytic material which is composed of a nickel titanate-based catalytic material and copper sulfide introduced to the surface of the nickel titanate-based catalytic material. The invention also discloses a preparation method of the copper sulfide / nickel titanate composite photocatalyst material, which comprises the following steps: preparing NiTiO3 by using Ni (CH3COO) 2.4 H2O and C16H36O4Ti, preparing CuS by using Cu (NO3) 2.5 H2O, CH4N2S and cetyltrimethylammonium bromide, dissolving NiTiO3 and CuS in deionized water, stirring, washing, drying, grinding and sieving to obtain the copper sulfide / nickel titanate composite photocatalyst material. The visible-light response range of the copper sulfide / nickel titanate composite photocatalyst material obtained by the preparation method is suitable for photocatalytic CO2 reduction reaction, the photocatalytic activity is remarkably improved compared with pure nickel titanate, the copper sulfide / nickel titanate composite photocatalyst material can be repeatedly used, and the copper sulfide / nickel titanate composite photocatalyst material is simple in preparation process, low in material price, mild in condition and convenient to operate.

Description

Technical Field

[0001] This invention belongs to the field of industrial catalytic material preparation technology, specifically relating to a method for preparing copper sulfide / nickel titanate composite photocatalytic materials, as well as the copper sulfide / nickel titanate composite photocatalytic materials and their applications. Background Technology

[0002] Photocatalytic reduction of carbon dioxide to high-value-added products based on semiconductor materials has become an effective way to solve environmental and energy problems due to its advantages such as environmental friendliness, low operation difficulty, and low cost. However, the photocatalytic carbon dioxide reduction reaction needs to overcome the high bond energy of activated C=O (≈750 kJ·mol). -1 Therefore, designing suitable semiconductor photocatalytic materials is particularly important. Copper sulfide (CuS), as an environmentally friendly and abundant p-type semiconductor material, stands out due to its good conductivity, controllable band structure, and strong photothermal effect. Meanwhile, perovskite-based NiTiO3, with its good ionic conductivity, exhibits excellent structural elasticity, stability, and environmental friendliness in terms of thermodynamics and chemical stability, and is considered one of the most promising candidates for promoting CO2 emission reduction. Therefore, in the CuS / NiTiO3 S-type heterojunction, a large amount of electrons are transferred to CuS to ensure the stability of Cu... 0 and Cu 2+ Ions stably interconvert, while Cu 0 As a site for CO2 adsorption activation, it exhibits excellent ability to reduce CO2 to CO. Furthermore, compared to Z-type or II-type heterojunction structures, the S-type heterojunction structure utilizes a unique built-in electric field at the interface, thereby improving the efficiency of photocatalytic CO2 reduction. Summary of the Invention

[0003] The first objective of this invention is to provide a method for preparing copper sulfide / nickel titanate composite photocatalytic materials, which solves the problems of slow photogenerated electron-hole transfer and low catalytic reduction activity in visible light of existing nickel titanate-based materials.

[0004] The second objective of this invention is to provide a copper sulfide / nickel titanate composite photocatalytic material.

[0005] The third objective of this invention is to provide the application of copper sulfide / nickel titanate composite photocatalysts in the photocatalytic reduction of carbon dioxide.

[0006] The technical solution adopted in this invention is a method for preparing copper sulfide / nickel titanate composite photocatalytic materials, which is implemented according to the following steps: Step 1: Dissolve Ni(CH3COO)2·4H2O in ethylene glycol and stir for 1-2 hours. Then, add C while stirring. 16 H 36O4Ti was stirred for 1-2 hours, the precipitate was washed with ethanol, dried under vacuum, and calcined to obtain NiTiO3. Step 2: Dissolve Cu(NO3)2·5H2O and CH4N2S in a mixture of ethylene glycol and deionized water. Then, under magnetic stirring, add hexadecyltrimethylammonium bromide and stir for 0.5-1 h. After the reaction is complete, wash with distilled water and ethanol respectively, and dry under vacuum to obtain CuS. Step 3: Dissolve NiTiO3 and CuS in deionized water, stir, then wash the precipitate with deionized water, dry, grind, and sieve to obtain copper sulfide / nickel titanate composite photocatalytic material.

[0007] The invention is further characterized in that, In step 1, the vacuum drying temperature is 60-80℃, and the vacuum drying time is 12-24h; during calcination, the temperature is increased to 400-600℃ at a rate of 2.5-5℃ / min and held for 2-4h. Ni(CH3COO)2·4H2O reacts with C 16 H 36 The mass ratio of O4Ti is 2.48-7.44:3.45-10.36.

[0008] In step 2, the mass ratio of Cu(NO3)2·5H2O, CH4N2S, and hexadecyltrimethylammonium bromide is 0.2-0.8:0.12-0.48:0.12-0.48. The hydrothermal reaction temperature is 100-140℃, and the hydrothermal reaction time is 16-18 h; the vacuum drying temperature is 60-80℃, and the vacuum drying time is 12-24 h.

[0009] In step 3, the stirring time is 12-24 hours and the stirring speed is 600-1000 rpm; the drying temperature is 60-80℃ and the drying time is 12-24 hours. The mass ratio of NiTiO3 to CuS is 50-100:1-10.

[0010] Another technical solution adopted in this invention is a method for preparing copper sulfide / nickel titanate composite photocatalytic materials.

[0011] The beneficial effects of this invention are: the copper sulfide / nickel titanate composite photocatalyst material obtained by this preparation method is free from agglomeration, has a visible light response range suitable for photocatalytic CO2 reduction reaction, has significantly improved photocatalytic activity compared to pure nickel titanate, can be reused, and has a simple preparation process, low material price, mild conditions, and convenient operation. Attached Figure Description

[0012] Figure 1These are the XRD patterns of CuS, NiTiO3, and 5% CuS / NiTiO3; Figure 2 This is the Zeta potential diagram for CuS and NiTiO3; Figure 3 This is a scanning electron microscope image of NiTiO3; Figure 4 This is a scanning electron microscope image of CuS; Figure 5 This is a scanning electron microscope image of 5% CuS / NiTiO3; Figure 6 This is a transmission electron microscope (TEM) image of 5% CuS / NiTiO3. Figure 7 This is an HRTEM image of 5% CuS / NiTiO3; Figure 8 This is the elemental spectrum of 5% CuS / NiTiO3; Figure 9 This is the high-resolution photoelectron spectrum of Ni 2p in 5% CuS / NiTiO3; Figure 10 This is the high-resolution photoelectron spectrum of Ti 2p for 5% CuS / NiTiO3; Figure 11 This is the O 1s high-resolution photoelectron spectrum of 5% CuS / NiTiO3; Figure 12 This is the Cu 2p high-resolution photoelectron spectrum of 5% CuS / NiTiO3; Figure 13 This is the S 2p high-resolution photoelectron spectrum of 5% CuS / NiTiO3; Figure 14 These are the EPR diagrams for CuS, NiTiO3, and 5% CuS / NiTiO3; Figure 15 The attached diagram shows the N2 adsorption-desorption of CuS, NiTiO3, and 5% CuS / NiTiO3. Figure 16 This is a pore size distribution diagram of CuS, NiTiO3, and 5% CuS / NiTiO3. Figure 17 This is the UV-Vis diffuse reflectance spectrum of 5% CuS / NiTiO3; Figure 18 This is a band gap width diagram of CuS and NiTiO3; Figure 19 This is the Mott-Schottky plot of CuS; Figure 20 This is the Mott-Schottky diagram of NiTiO3; Figure 21 These are the VB-XPS spectra of CuS and NiTiO3; Figure 22 This is the band structure diagram of 5% CuS / NiTiO3; Figure 23 These are graphs showing the photocatalytic CO2 reduction performance of CuS / NiTiO3 with different ratios; Figure 24 This is a graph showing the electron selectivity of CO and H2 for CuS / NiTiO3 with different ratios; Figure 25 These are the photocatalytic CO2 reduction activity graphs of 5% CuS / NiTiO3 under different conditions; Figure 26 This is a long-term stability graph of CuS, NiTiO3, and 5% CuS / NiTiO3; Figure 27 This is a cyclic stability graph of 5% CuS / NiTiO3; Figure 28 The XRD patterns of 5% CuS / NiTiO3 before and after the reaction are shown. Figure 29 These are the EIS spectra of CuS, NiTiO3, and 5% CuS / NiTiO3; Figure 30 These are the PL spectra of CuS, NiTiO3, and 5% CuS / NiTiO3; Figure 31 These are the TRPL spectra of CuS, NiTiO3, and 5% CuS / NiTiO3; Figure 32 This is a KPFM image of CuS under dark illumination and the corresponding line scan surface potential distribution map; Figure 33 These are KPFM images of NiTiO3 under dark illumination and corresponding line scan surface potential distribution maps; Figure 34 These are KPFM images of 5% CuS / NiTiO3 under dark illumination and the corresponding line scan surface potential distribution diagram; Figure 35 These are XPS comparison images before and after the reaction of 5% CuS / NiTiO3; Figure 36 This is the in-situ XPS spectrum of Cu 2p in 5% CuS / NiTiO3; Figure 37 This is the S 2p in-situ XPS spectrum of 5% CuS / NiTiO3; Figure 38 This is the in-situ XPS spectrum of Ni 2p in 5% CuS / NiTiO3; Figure 39 This is the in-situ XPS spectrum of Ti 2p for 5% CuS / NiTiO3; Figure 40 This is the O 1s in-situ XPS spectrum of 5% CuS / NiTiO3; Figure 41 This is a diagram of the electron transfer pathway in the S-type heterojunction for the CuS / NiTiO3 photocatalytic reaction. Figure 42 This is the in-situ DRIFTS spectrum of CuS / NiTiO3 photocatalytic CO2 reduction. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0014] This invention relates to a copper sulfide / nickel titanate composite photocatalyst, which consists of an indium zinc sulfide-based photocatalyst and gallium sulfide introduced onto the surface of the indium zinc sulfide-based photocatalyst. The mass of copper sulfide is 0.5%-30% of the mass of the nickel titanate-based photocatalyst.

[0015] The preparation method of the copper sulfide / nickel titanate composite photocatalytic material of the present invention is carried out according to the following steps: Step 1: Dissolve Ni(CH3COO)2·4H2O in ethylene glycol and stir for 1-2 hours. Then, add C while stirring. 16 H 36 O4Ti was stirred for 1-2 hours to obtain a blue precipitate. The precipitate was washed several times with ethanol and dried in a vacuum drying oven at 60-80℃ for 12-24 hours to obtain the NiTiO3 precursor. The NiTiO3 precursor was then calcined to obtain the yellow product NiTiO3. Ni(CH3COO)2·4H2O and C 16 H 36 The mass ratio of O4Ti is 2.48-7.44:3.45-10.36; during calcination, the temperature is raised to 400-600℃ at a rate of 2.5-5℃ / min and held for 2-4 hours. Step 2: Dissolve Cu(NO3)2·5H2O and CH4N2S in a mixture of ethylene glycol and deionized water. Then, under magnetic stirring, add hexadecyltrimethylammonium bromide and stir for 0.5-1 h. Then, place the mixture in a Teflon-lined autoclave for hydrothermal reaction at a temperature of 100-140℃ for 16-18 h. After the reaction is complete, wash three times with distilled water and ethanol respectively, and vacuum dry at 60-80℃ for 12-24 h to obtain the product CuS.

[0016] The mass ratio of Cu(NO3)2·5H2O, CH4N2S, and hexadecyltrimethylammonium bromide is 0.2-0.8:0.12-0.48:0.12-0.48; Step 3: Dissolve NiTiO3 and CuS in deionized water and stir magnetically at room temperature for 12-24 hours at a stirring rate of 600-1000 rpm. Wash the precipitate several times with deionized water, dry it at a temperature of 60-80℃ for 12-24 hours, grind it, and sieve it to obtain copper sulfide / nickel titanate (CuS / NiTiO3) composite photocatalytic material. The mass ratio of NiTiO3 to CuS is 50-100:1-10.

[0017] Nickel titanate exhibits good visible light absorption and effective charge separation capabilities. In the nickel titanate lattice, Ni... 2+ and Ti 4+ Separated by oxygen atoms, photogenerated electrons tend to be localized in Ti. 4+ Site, photogenerated hole localized in Ni 2+ This effectively reduces the recombination of photogenerated charges and holes. Meanwhile, CuS possesses good electrical conductivity, a controllable band structure, and a strong photothermal effect. Therefore, in the CuS / NiTiO3 S-type heterojunction, driven by the Fermi level difference, electrons flow from the high Fermi level to the low Fermi level semiconductor, leading to a redistribution of charges on both sides of the interface. An embedded electric field is formed near the charge accumulation interface, pointing from CuS to NiTiO3. The presence of this embedded electric field drives the rapid transfer of electrons to the CuS surface to participate in the photocatalytic CO2 reduction reaction.

[0018] Example 1 The preparation method of the copper sulfide / nickel titanate composite photocatalytic material of the present invention is carried out according to the following steps: Step 1: Dissolve 2.48 g of Ni(CH3COO)2·4H2O in 60 mL of ethylene glycol and stir at room temperature for 2 h. During magnetic stirring, add 3.4 mL of C... 16 H 36 O4Ti. Magnetic stirring was continued for 2 h to obtain a blue precipitate. The precipitate was washed several times with ethanol and dried in a vacuum drying oven at 60 °C for 12 h. Then, the NiTiO3 precursor was calcined at 600 °C at a heating rate of 5 °C / min for 4 h to obtain the yellow product NiTiO3.

[0019] Step 2: Dissolve 0.5 g Cu(NO3)2·5H2O and 0.3 g CH4N2S in a solution containing 10 ml ethylene glycol and 30 ml deionized water. Then, under magnetic stirring, dissolve 0.3 g hexadecyltrimethylammonium bromide (CTAB) in the above solution for 30 minutes. Next, place the mixture in a 50 ml Teflon-lined autoclave and heat at 100 °C for 18 hours. After the reaction is complete, wash three times each with distilled water and ethanol, and dry under vacuum at 60 °C for 12 hours. Collect the product CuS.

[0020] Step 3: Weigh 100 mg NiTiO3 and 3 mg CuS and dissolve them in 30 mL of water. Stir vigorously with a magnetic stirrer for 24 h at room temperature. Wash the precipitate several times with water, then dry and grind it to obtain the CuS / NiTiO3 sample.

[0021] Example 2 The preparation method of the copper sulfide / nickel titanate composite photocatalytic material of the present invention is carried out according to the following steps: Step 1: Dissolve 2.48 g of Ni(CH3COO)2·4H2O in 60 mL of ethylene glycol and stir at room temperature for 2 h. During magnetic stirring, add 3.4 mL of C... 16 H 36 O4Ti. Magnetic stirring was continued for 2 h to obtain a blue precipitate. The precipitate was washed several times with ethanol and dried in a vacuum drying oven at 60 ℃ for 12 h. Then, the NiTiO3 precursor was calcined at 600 ℃ with a heating rate of 5 ℃ / min for 4 h to obtain a yellow NiTiO3 product.

[0022] Step 2: Dissolve 0.5 g Cu(NO3)2·5H2O and 0.3 g CH4N2S in a solution containing 10 ml ethylene glycol and 30 ml deionized water. Then, under magnetic stirring, dissolve 0.3 g hexadecyltrimethylammonium bromide (CTAB) in the above solution for 30 minutes. Next, place the mixture in a 50 ml Teflon-lined autoclave and heat at 100 °C for 18 hours. After the reaction is complete, wash three times each with distilled water and ethanol, and collect the product CuS after vacuum drying at 60 °C for 12 hours.

[0023] Step 3: Weigh 100 mg NiTiO3 and 5 mg CuS and dissolve them in 30 mL of water. Stir vigorously with a magnetic stirrer for 24 h at room temperature. Wash the precipitate several times with water, then dry and grind it to obtain the CuS / NiTiO3 sample.

[0024] Example 3 The preparation method of the copper sulfide / nickel titanate composite photocatalytic material of the present invention is carried out according to the following steps: Step 1: Dissolve 2.48 g of Ni(CH3COO)2·4H2O in 60 mL of ethylene glycol and stir at room temperature for 2 h. During magnetic stirring, add approximately 3.4 mL of C... 16 H 36 O4Ti. Magnetic stirring was continued for 2 h to obtain a blue precipitate. The precipitate was washed several times with ethanol and dried in a vacuum drying oven at 60 ℃ for 12 h. Then, the NiTiO3 precursor was calcined at 600 ℃ at a heating rate of 5 ℃ / min for 4 h to obtain the yellow NiTiO3 product.

[0025] Step 2: Dissolve 0.5 g Cu(NO3)2·5H2O and 0.3 g CH4N2S in a solution containing 10 ml ethylene glycol and 30 ml deionized water. Then, under magnetic stirring, dissolve 0.3 g hexadecyltrimethylammonium bromide (CTAB) in the above solution for 30 minutes. Next, place the mixture in a 50 ml Teflon-lined autoclave and heat at 100 °C for 18 hours. After the reaction is complete, wash three times each with distilled water and ethanol, and collect the product CuS after vacuum drying at 60 °C for 12 hours.

[0026] Step 3: Weigh 100 mg NiTiO3 and 7 mg CuS and dissolve them in 30 mL of water. Stir vigorously with a magnetic stirrer for 24 h at room temperature. Wash the precipitate several times with water, then dry and grind it to obtain the CuS / NiTiO3 sample.

[0027] Example 4 The preparation method of the copper sulfide / nickel titanate composite photocatalytic material of the present invention is carried out according to the following steps: Step 1: Dissolve Ni(CH3COO)2·4H2O in ethylene glycol and stir for 2 hours. Then, add C while stirring. 16 H 36 O4Ti was stirred for 1 hour to obtain a blue precipitate. The precipitate was washed several times with ethanol and dried in a vacuum drying oven at 60°C for 20 hours to obtain the NiTiO3 precursor. The NiTiO3 precursor was then calcined to obtain the yellow product NiTiO3. Ni(CH3COO)2·4H2O and C 16 H 36 The mass ratio of O4Ti is 2.48:3.45; During calcination, the temperature is increased to 400℃ at a rate of 2.5℃ / min and held for 4 hours. Step 2: Dissolve Cu(NO3)2·5H2O and CH4N2S in a mixture of ethylene glycol and deionized water. Then, under magnetic stirring, add hexadecyltrimethylammonium bromide and stir for 1 hour. Then, place the mixture in a Teflon-lined autoclave for hydrothermal reaction at a temperature of 140°C for 16 hours. After the reaction is complete, wash three times with distilled water and ethanol respectively, and dry under vacuum at 60°C for 24 hours to obtain the product CuS.

[0028] The mass ratio of Cu(NO3)2·5H2O, CH4N2S, and hexadecyltrimethylammonium bromide is 0.2:0.12:0.12; Step 3: Dissolve NiTiO3 and CuS in deionized water and stir magnetically for 12 hours at room temperature at a stirring speed of 600 rpm; wash the precipitate several times with deionized water, dry it at 60℃ for 12 hours, grind it, and sieve it to obtain copper sulfide / nickel titanate (CuS / NiTiO3) composite photocatalytic material; the mass ratio of NiTiO3 to CuS is 50:1.

[0029] Example 5 The preparation method of the copper sulfide / nickel titanate composite photocatalytic material of the present invention is carried out according to the following steps: Step 1: Dissolve Ni(CH3COO)2·4H2O in ethylene glycol and stir for 1 hour. Then, add C while stirring. 16 H 36 O4Ti was stirred for 1 hour to obtain a blue precipitate. The precipitate was washed several times with ethanol and dried in a vacuum drying oven at 80°C for 12 hours to obtain the NiTiO3 precursor. The NiTiO3 precursor was then calcined to obtain the yellow product NiTiO3. Ni(CH3COO)2·4H2O and C 16 H 36 The mass ratio of O4Ti is 7.44:10.36; During calcination, the temperature is increased to 500℃ at a rate of 4℃ / min and held for 2.5 hours. Step 2: Dissolve Cu(NO3)2·5H2O and CH4N2S in a mixture of ethylene glycol and deionized water. Then, under magnetic stirring, add hexadecyltrimethylammonium bromide and stir for 0.5 h. Then, place the mixture in a Teflon-lined autoclave for hydrothermal reaction at 100 °C for 16 h. After the reaction is complete, wash three times with distilled water and ethanol respectively, and dry under vacuum at 65 °C for 18 h to obtain the product CuS.

[0030] The mass ratio of Cu(NO3)2·5H2O, CH4N2S, and hexadecyltrimethylammonium bromide is 0.8:0.3:0.4; Step 3: Dissolve NiTiO3 and CuS in deionized water and stir magnetically for 12 hours at room temperature at a stirring speed of 1000 rpm; wash the precipitate several times with deionized water, dry it at 80℃ for 24 hours, grind it, and sieve it to obtain copper sulfide / nickel titanate (CuS / NiTiO3) composite photocatalytic material; the mass ratio of NiTiO3 to CuS is 100:9.

[0031] Figure 1 The X-ray diffraction patterns of NiTiO3, CuS, and 5% CuS / NiTiO3 from Example 2 show the successful preparation of NiTiO3 (JCPDS#033-0960) and CuS (JCPDS#06-0464). Characteristic peaks belonging to the CuS crystalline phase were observed in 5% CuS / NiTiO3, proving the successful synthesis of the CuS / NiTiO3 S-type heterojunction.

[0032] Figure 2 The Zeta potential measurements for CuS and NiTiO3 show that the surface potential of CuS is 41.38 mV, while that of NiTiO3 is -39.77 mV. This demonstrates that the electrostatic self-assembly of CuS / NiTiO3 can be successfully achieved.

[0033] Figures 3-5 The scanning electron microscope (SEM) images of NiTiO3, CuS, and 5% CuS / NiTiO3 show that NiTiO3 and CuS are nanoflowers composed of nanorods and nanosheets, respectively, with a diameter of approximately 1-2 micrometers. Figure 6 This is a TEM image of 5% CuS / NiTiO3, which is formed by stacking CuS nanosheets on NiTiO3. Figure 7 The image shows the HRTEM image of 5% CuS / NiTiO3, with the interplanar spacings of CuS and NiTiO3 measured to be 0.3 nm and 0.25 nm, respectively. The material composition and chemical state of NiTiO3 and CuS / NiTiO3 were displayed by high-resolution photoelectron spectroscopy, and peak calibration was performed in the C1s (284.80 eV) background to verify the electron transfer pathway in the catalyst. Figure 8 The image shows the total elemental spectrum of the 5% CuS / NiTiO3 sample, proving the successful synthesis of the S-type heterojunction. Figure 9 For the Ni 2p spectrum, Ni 2p 3 / 2 and Ni 2p 1 / 2The peak at the point shifts towards higher binding energy after the reaction, indicating that electrons in the catalyst may be transferred from NiTiO3 to CuS at the heterogeneous interface via the built-in electric field. Figure 10 and Figure 11 These are the spectra of Ti 2p and O 1s, respectively. Figure 12 shows the Cu 2p spectrum, specifically the spectrum of Cu 2p. 3 / 2 (931.5 eV) and Cu 2p 1 / 2 The two peaks at (951.6 eV) represent Cu. 0 and Cu 2+ The presence of Cu. Comparing the Cu 2p spectra before and after, the 2p orbital peaks of Cu are shifted towards lower binding energies, indicating that during the reaction, electrons are transferred from NiTiO3 to CuS, and Cu... 2+ It accepts electrons and becomes Cu 0 Cu 0 The sites may partially recover to their original valence state after reacting with CO2. Figure 13 shows the S 2p spectrum, which exhibits two different S 2p peaks. The peak at 162.0 eV belongs to a fully coordinated S atom, while the peak at 164.1 eV belongs to an incompletely coordinated S single atom, which may be exposed at the catalyst edge and have photocatalytic activity.

[0034] Figure 14 The image shows the EPR of CuS / NiTiO3, indicating that the synthesis of 5% CuS / NiTiO3 led to the generation of sulfur and oxygen vacancies.

[0035] Figure 15 and Figure 16 The results, measured by BET and pore size distribution, indicate that the specific surface area of ​​CuS / NiTiO3 increases compared to pure NiTiO3 after the introduction of CuS, with a pore size distribution ranging from 20 to 40 nm. This suggests that the increased adsorption area of ​​CuS / NiTiO3 for CO2 enhances its ability to adsorb and activate CO2.

[0036] Figure 17 The UV-Vis diffuse reflectance spectra of NiTiO3 and CuS and Figure 18 It is the band gap width calculated using the Tauc diagram. Figure 19 The surface area test of the catalyst showed that the specific surface area increased significantly after the introduction of CuS. Figure 20 and Figure 21 The calculated CB values ​​for CuS and NiTiO3 are -0.72 eV and -0.53 eV, respectively. Figure 22 These are the VB-XPS spectra of NiTiO3 and CuS. It can be seen that the valence bands of NiTiO3 and CuS are 1.86 eV and 0.49 eV, respectively.

[0037] In summary, this demonstrates that CuS has been successfully introduced onto the surface of NiTiO3, ultimately yielding a copper sulfide / nickel titanate composite photocatalyst and an electron-hole transfer pathway in the S-type heterojunction.

[0038] Example 6 The copper sulfide / nickel titanate composite photocatalyst material prepared by this invention can be used for photocatalytic CO2 reduction.

[0039] The experimental conditions were as follows: Photocatalytic CO2 reduction was carried out in a 100 mL micro high-pressure photocatalytic reactor. A solution containing 1 mL of [Ru(bpy)3]Cl2·6H2O and 5 mg of photocatalyst was added to the 100 mL micro high-pressure photocatalytic reactor. The reactor was repeatedly evacuated to completely remove air, and then filled with 1.0 atm of carbon dioxide. A 300 W xenon lamp with a 420 nm cutoff filter was used as the light source, and the incident light intensity during the reaction was measured to be 150 mW·cm. -2 The reaction system was stirred at 900 r / min, and cooling water was circulated to maintain the temperature at 25 °C. After the reaction, the gaseous products were analyzed using a gas chromatograph equipped with a thermal conductivity detector and a flame ionization detector. The experiment was repeated three times, and the average value of the data was taken. The generation rate was estimated based on the amount of gas generated, and the photocatalytic CO2 reduction activity was detected.

[0040] The photocatalytic CO2 reduction performance of the samples was investigated. The photocatalytic CO2 reduction test was conducted in a gas-liquid-solid system with a sacrificial agent. Figure 23 This indicates that adjusting the mass ratio of the co-catalyst CuS can improve the photocatalytic CO2RR performance of NiTiO3. Comparative analysis shows that the sample exhibits optimal activity when the CuS content is 5%, with a CO generation rate reaching 490 μmol·g⁻¹. -1 ·h -1 . Figure 24 The electron selectivity of the photocatalytic CO2RR products was demonstrated. It can be seen that the highest electron percentage for CO (89.7%) was observed in the 5% CuS / NiTiO3 sample. A control experiment was conducted to verify the carbon source for CO formation. Figure 25 As shown, no CO was detected under CO2-free conditions, proving that the carbon source of CO came from the introduced high-purity CO2. Therefore, experimental comparison confirms that CO formation only occurs when a light source, CO2, sacrificial agent, and catalyst are present simultaneously. Figure 26 The results showed that the amount of CO generated increased with increasing reaction time. After 2 hours of reaction, the CO yield of 5% CuS / NiTiO3 was 690 μmol·g. -1 It is significantly higher than that of CuS and NiTiO3. Figure 27The cycling stability of the 5% CuS / NiTiO3 sample was evaluated. After five cycles, the performance decreased slightly, indicating excellent cycling stability. Meanwhile, the XRD pattern after the reaction (…) Figure 28 No significant changes were observed, demonstrating the stability of the catalyst.

[0041] Figure 29 The electrochemical impedance spectroscopy (EIS) results show that the 5% CuS / NiTiO3 composite material has a smaller resistivity semicircle compared to CuS and NiTiO3, indicating that it has a faster electron transfer rate. Figure 30 It can be seen that the steady-state fluorescence peak intensity of 5% CuS / NiTiO3 is the lowest, indicating that the composite sample exhibits a highly efficient charge carrier separation capability. Figure 31 The average lifetime of charge carriers in 5% CuS / NiTiO3 was measured to be 2.47 ns in the transient fluorescence spectrum, which is significantly longer than that of CuS and NiTiO3. This indicates that the S-type heterojunction structure can effectively delay charge-hole recombination.

[0042] Figures 32-34 The images show KPFM images of NiTiO3, CuS, and 5% CuS / NiTiO3 under illumination and darkness conditions, consistent with SEM and TEM observations. They also show contact potential differences of 4.34 mV, 14.6 mV, and 30.9 mV for NiTiO3, CuS, and 5% CuS / NiTiO3, respectively. Compared to CuS and NiTiO3, CuS / NiTiO3 exhibits a significantly higher ΔCPD, attributed to the accumulation of photogenerated holes, indicating that the S-type heterojunction in CuS / NiTiO3 can more effectively transfer photogenerated electrons / holes. This result provides direct evidence for the existence of an interfacial electric field from NiTiO3 to CuS, which significantly enhances the separation and transfer of photogenerated carriers.

[0043] Figures 35-40 The image shows the in-situ XPS spectra of CuS / NiTiO3. The binding energies in the in-situ XPS spectra of Cu 2p and Ni 2p shift towards higher and lower directions, respectively. This indicates that electrons move from NiTiO3 to CuS through the built-in electric field formed by the S-type heterojunction and accumulate there, resulting in a photocatalytic CO2 reduction reaction. Figure 41 It is an S-type heterojunction electron transfer pathway, in which electrons in the CuS / NiTiO3 S-type heterojunction transition from the CB of NiTiO3 to CuS to carry out the photocatalytic CO2 reduction reaction.

[0044] Figure 42 This is a detailed in-situ DRIFTS spectrum of photocatalytic CO2 reduction, which revealed the presence of several adsorbed carbonate substances at 1507 cm⁻¹. -1 1364 cm -1and 1186 cm -1 1258cm -1 1339 cm -1 They belong to m-CO3, an important intermediate in the reduction pathway. 2- and b-CO3 2- 1455 cm -1 and 1412 cm -1 They are HCO3 - When the adsorbed hydrohydroxyl groups react with CO2, carbonate substances are generated on the surface of the photocatalyst. These represent different CO2 adsorption modes on the photocatalyst surface and demonstrate the generation of intermediates in the photocatalytic CO2 reduction pathway.

Claims

1. A method for preparing a copper sulfide / nickel titanate composite photocatalytic material, characterized in that, Specifically, the following steps are implemented: Step 1, dissolve Ni(CH3COO)2-4H2O in ethylene glycol, stir for 1-2 h, then add C 16 H 36 O4Ti under stirring, continue stirring for 1-2 h, wash the precipitate with ethanol, dry in vacuum, calcine to obtain NiTiO3; Step 2, Cu(NO3)2·5H2O and CH4N2S are dissolved in a mixture of ethylene glycol and deionized water, then under magnetic stirring, cetyltrimethylammonium bromide is added, and stirring is performed for 0.5-1h, after which a hydrothermal reaction is performed, and after the reaction is completed, washing is performed with distilled water and ethanol, and vacuum drying is performed to obtain CuS; Step 3, NiTiO3 and CuS are dissolved in deionized water, stirring is performed, then the precipitate is washed with deionized water, dried, ground, sieved, and a copper sulfide / nickel titanate composite photocatalytic material is obtained.

2. The method for preparing the copper sulfide / nickel titanate composite photocatalytic material according to claim 1, characterized in that, In the step 1, the vacuum drying temperature is 60-80℃, and the vacuum drying time is 12-24h; during calcination, the temperature is increased to 400-600℃ at a rate of 2.5-5℃ / min, and the temperature is maintained for 2-4h.

3. The preparation method of the copper sulfide / nickel titanate composite photocatalytic material as described in claim 1, characterized in that, In the step 1, Ni(CH3COO)2·4H2O and C 16 H 36 The mass ratio of Ni to TiO4 is 2.48-7.44:3.45-10.

36.

4. The preparation method of the copper sulfide / nickel titanate composite photocatalytic material as described in claim 1, characterized in that, In the step 2, the mass ratio of Cu(NO3)2·5H2O, CH4N2S and cetyltrimethylammonium bromide is 0.2-0.8:0.12-0.48:0.12-0.

48.

5. The preparation method of the copper sulfide / nickel titanate composite photocatalytic material as described in claim 1, characterized in that, In the step 2, the hydrothermal reaction temperature is 100-140℃, and the hydrothermal reaction time is 16-18h; the vacuum drying temperature is 60-80℃, and the vacuum drying time is 12-24h.

6. The preparation method of the copper sulfide / nickel titanate composite photocatalytic material as described in claim 1, characterized in that, In the step 3, the mass ratio of NiTiO3 and CuS is 50-100:1-10.

7. The preparation method of the copper sulfide / nickel titanate composite photocatalytic material as described in claim 1, characterized in that, In the step 3, the stirring time is 12-24h, and the stirring rate is 600-1000rpm; the drying temperature is 60-80℃, and the drying time is 12-24h.

8. The copper sulfide / nickel titanate composite photocatalytic material prepared by the preparation method of the copper sulfide / nickel titanate composite photocatalytic material according to any one of claims 1-7.

9. The application of the copper sulfide / nickel titanate composite photocatalytic material according to any one of claims 1-7 in photocatalytic reduction of carbon dioxide.

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