Synthesis of one-dimensional tubular In2O3 / ZnIn2S4 composite materials and their application in photocatalytic reduction of CO2

Abstract

This invention discloses a method for synthesizing one-dimensional tubular In2O3 / ZnIn2S4 composite materials and their application in photocatalytic reduction of CO2. Using In-MIF-68 as a template, hollow In2O3 microtubes are first calcined to form them. Then, sheet-like ZnIn2S4 structures are in situ grown on the In2O3 surfaces via a low-temperature hydrothermal method. The synthesis method is simple and employs mild reaction conditions. The resulting hollow In2O3 / ZnIn2S4 microtubes exhibit significant catalytic activity and can be used in reactions involving the oxidation of aromatic alcohols coupled to the reduction of CO2.

Description

Technical Field

[0001] The present invention belongs to the field of nanomaterial preparation and photocatalysis technology, and specifically relates to a synthesis method of In2O3 / ZnIn2S4 (IO / ZIS) composite materials and their application in the field of energy photocatalysis. Background Art

[0002] While hydrocarbon fuels such as coal, oil and natural gas provide indispensable energy for social development, their mining, refining and use also bring about a series of environmental problems such as greenhouse gases (the main component is CO2). Effectively converting CO2 into hydrocarbon fuels through artificial photosynthesis is one of the effective ways to simultaneously solve the greenhouse effect and energy crisis. Although photocatalytic reduction technology is of great significance for CO2 emission reduction and the production of organic compounds, its efficiency is low and the products are complex. How to improve the reduction activity and selectivity of the catalyst remains a difficult problem to be solved. Therefore, the design and construction of visible light responsive, efficient and stable catalysts for CO2 reduction is of great significance.

[0003] Metal sulfides (CdS, ZnIn2S4, and Zn3In2S6) have been widely studied due to their excellent visible light response, suitable band structures, and promising photocatalytic activity. Two-dimensional sheets of ZnIn2S4, a typical example, hold great promise for photocatalytic degradation of pollutants, selective oxidation of aromatic alcohols, water decomposition to produce hydrogen, and CO2 reduction. However, the catalytic activity of ZnIn2S4 is unsatisfactory due to slow charge carrier separation and migration. Heterogeneous composites and morphology manipulation are effective approaches to improve photocatalytic performance. Summary of the Invention

[0004] The object of the present invention is to provide a method for synthesizing a one-dimensional tubular In2O3 / ZnIn2S4 composite material to enhance visible light CO2 reduction under mild reaction conditions.

[0005] In order to achieve the purpose, the present invention adopts the following technical solutions:

[0006] The synthesis method of one-dimensional tubular In2O3 / ZnIn2S4 composite materials includes two steps: using MOF (MIL-68) hexagonal prisms as a precursor, a calcination process is performed to obtain hierarchical In2O3 microtubes; and flake ZnIn2S4 is in situ grown on the In2O3 tubular microstructures. The specific steps are:

[0007] (1) Preparation of precursor In-MIL-68: In(NO3)2·xH2O and terephthalic acid were used as raw materials and N,N-dimethylformamide (DMF) was used as solvent to synthesize the precursor In-MIL-68 in an oil bath.

[0008] (2) Preparation of In2O3 microtubes: In-MIL-68 precursor was placed in a muffle furnace for calcination to obtain In2O3 microtubes;

[0009] (3) Preparation of one-dimensional tubular In2O3 / ZnIn2S4 composite material: The In2O3 microtubes were added to a round-bottom flask containing an aqueous solution and stirred for 30 min. ZnCl2, InCl3 and thioacetamide were then added in sequence. A one-dimensional tubular x% In2O3 / ZnIn2S4 composite material (abbreviated as x%IO / ZIS) was obtained by low-temperature oil bath reaction, where x represents the mass ratio of In2O3 in the composite material.

[0010] Furthermore, the specific method of step (1) is as follows: 1.20 g of In(NO3)2·xH2O and 1.20 g of terephthalic acid are dissolved in 100 mL of DMF, stirred for 10 min, and then the formed solution is reacted in an oil bath at 120°C for 2 h. After the solution is cooled to room temperature, the white precipitate is collected and washed three times with C2H5OH, and the product is vacuum dried at 60°C for 10 h to obtain the precursor In-MIL-68.

[0011] Furthermore, the specific method of step (2) is: placing the precursor In-MIL-68 in a muffle furnace, in an air atmosphere, first heating it to 120°C at a heating rate of 5°C / min and keeping it warm for 2 hours, then heating it to 500°C and further calcining it for 2 hours, and finally cooling it to room temperature to obtain In2O3 microtubes.

[0012] Furthermore, the specific method of step (3) is as follows: weigh a certain amount of In2O3, add it to a round-bottom flask with 100mL of pH = 2 (adjusted with hydrochloric acid) aqueous solution, stir for 30 minutes, then add 0.272gZnCl2, 0.442gInCl3 and 0.300g of thioacetamide in sequence, stir for 5 minutes, and then move the resulting mixture to an 80°C oil bath to react for 2 hours; after the reaction is completed, cool to room temperature, wash the product three times with ethanol, and vacuum dry it at 60°C for 10 hours to obtain a one-dimensional tubular x% In2O3 / ZnIn2S4 composite material.

[0013] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0014] 1. This invention forms a composite structure of In2O3 and ZnIn2S4 by in situ growing flaky ZnIn2S4 on hollow In2O3 microtubes. This creates an asymmetric electron and hole barrier, helping to suppress the recombination of photogenerated electrons and holes. The hollow structure also enhances the material's light absorption, CO2 adsorption and desorption properties, and charge transfer. As a visible-light photocatalyst for CO2 reduction, the optimized IO / ZIS heterostructure exhibits high activity and excellent stability, enabling the selective reduction of CO2 to CO without the aid of any precious metal co-catalyst.

[0015] 2. The present invention provides an in-situ synthesis method for hollow nanomaterials and their energy photocatalytic application, and obtains IO / ZIS nanomaterials in a controllable manner, providing a simple new strategy for reference for the surface regulation of other nanomaterials.

[0016] 3. The preparation method of the present invention is simple, the reaction conditions are mild, and the yield is high. The morphology of the IO / ZIS obtained by the method of the present invention has obvious catalytic activity and can be used for photocatalytic CO2 reduction, effectively protecting the environment and providing a guarantee for people's lives. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 SEM (a) and TEM (b) images of In-MIL-68 synthesized in Example 1;

[0018] Figure 2 SEM images of In2O3 synthesized in Example 2, where (a) and (b) correspond to different magnifications;

[0019] Figure 3 This is the SEM image of ZnIn2S4 synthesized in Example 3;

[0020] Figure 4 SEM images of the 30% IO / ZIS composite material synthesized in Example 4, where (a) and (b) correspond to different magnifications;

[0021] Figure 5 (a) and (b) are XRD patterns of In2O3, ZnIn2S4 and x%IO / ZIS nanomaterials synthesized in Examples 2, 3 and 4;

[0022] Figure 6 Activity diagrams for the photocatalytic reduction of CO2 by In2O3, ZnIn2S4 and x%IO / ZIS synthesized in Examples 2, 3 and 4;

[0023] Figure 7 This is a graph showing the CO2 reduction activity of 30% IO / ZIS synthesized in Example 4 at different reaction times;

[0024] Figure 8 This is a graph showing the CO2 reduction activity of 30% IO / ZIS synthesized in Example 4 at different wavelengths;

[0025] Figure 9 This is a diagram of the CO2 reduction activity of 30% IO / ZIS synthesized in Example 4 with different substituents. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to specific embodiments. The description of the specific embodiments is essentially merely an example. The following embodiments are implemented based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0027] Example 1

[0028] 1.20 g of In(NO₃)₂·xH₂O and 1.20 g of terephthalic acid were dissolved in 100 mL of DMF and stirred for 10 minutes. The resulting solution was then reacted in an oil bath at 120°C for 2 hours. After the solution cooled to room temperature, the white precipitate was collected and washed three times with C₂H₅OH. Finally, the product was vacuum dried at 60°C for 10 hours to obtain the precursor In-MIL-68.

[0029] Example 2

[0030] The precursor In-MIL-68 obtained in Example 1 was placed in a muffle furnace. In an air atmosphere, the temperature was first raised to 120°C at a heating rate of 5°C / min and kept warm for 2 hours. The temperature was then raised to 500°C and further calcined for 2 hours. Finally, the temperature was cooled to room temperature to obtain In2O3 microtubes.

[0031] Example 3

[0032] 0.272 g ZnCl2, 0.442 g InCl3, and 0.300 g thioacetamide were weighed and added to a 100 mL aqueous solution (adjusted to pH 2 with hydrochloric acid) in a round-bottom flask. The mixture was stirred for 5 minutes and then moved to an 80°C oil bath for 2 hours. After the reaction was completed, the mixture was cooled to room temperature and washed three times with ethanol. Finally, the product was vacuum-dried at 60°C for 10 hours to obtain a ZnIn2S4 sample.

[0033] Example 4

[0034] A certain amount of In2O3 was weighed and added to a 100mL aqueous solution (adjusted to pH 2 with hydrochloric acid) in a round-bottom flask and stirred for 30 minutes. 0.272g of ZnCl2, 0.442g of InCl3, and 0.300g of thioacetamide were then added in sequence. The mixture was stirred for 5 minutes and then transferred to an 80°C oil bath for 2 hours. After the reaction was complete, the mixture was cooled to room temperature, washed three times with ethanol, and finally dried under vacuum at 60°C for 10 hours to obtain a sample with x% IO / ZIS.

[0035] By adjusting the amount of In2O3 to 0.0941g~0.847g, samples with x=10~90 were obtained respectively.

[0036] Example 5

[0037] The In2O3, ZnIn2S4, and x%IO / ZIS catalysts prepared in the above examples were tested for their activity in the synergistic CO2 reduction and aromatic alcohol selective oxidation reactions in an online photocatalytic CO2 reaction system (MC-SCO2II-AG, Beijing Magnesium Technology Co., Ltd.). 50 mg of catalyst, 10 mL of aromatic alcohol, and 90 mL of DMF were added to a quartz reactor and mixed thoroughly. The reactor was then connected to the photocatalytic reaction system and evacuated. After the air in the system was completely evacuated, 300 mL of CO2 (99.999% purity) was injected as the reaction gas. The reaction solution was first stirred in the dark for half an hour to achieve dynamic gas solution equilibrium. A xenon lamp (λ > 400 nm) was then used for illumination, and the photocatalytic reaction system was simultaneously started. Throughout the photocatalytic process, the reactor temperature was controlled by a circulating condenser and maintained at 5°C. CH4 and CO were detected using an FID, and H2 was detected using a TCD on an online gas chromatograph (GC9790II, FULI). After 4 hours of reaction, the solution was collected and the amount of liquid products such as aromatic alcohol was determined by another gas chromatography method (GC9790Ⅱ, FULI). The amount of aromatic alcohol and aromatic aldehyde after the reaction was calculated.

[0038] Characterization and catalytic activity testing of nanomaterials IO / ZIS:

[0039] The microstructure of the sample was characterized by SEM and TEM techniques, and it can be clearly seen that the morphology of the precursor In-MIL-68 is a solid hexagonal prism ( Figure 1 The microscopic morphology of the In2O3 monomer obtained after calcination is a hollow hexagonal tube with a rough surface ( Figure 2 ), and the diameter of the tube mouth is about 1-2μm. ZnIn2S4 is a flake material ( Figure 3), the thickness of the sheet is about 10nm. The x% In2O3 / ZnIn2S4 sample is a sheet of ZnIn2S4 growing inside and outside the hollow tubular body of In2O3 ( Figure 4 ).

[0040] The crystal structure and phase composition of the prepared IO / ZIS catalyst were studied by X-ray powder diffraction (XRD). Figure 5 As shown in (a), in the prepared x%IO / ZIS sample, except for the diffraction peaks of In2O3 and ZnIn2S4, no other impurity peaks appear. When x≤30, the characteristic diffraction peak of the (110) crystal plane of ZnIn2S4 can be seen, but as the In2O3 loading increases, the ZnIn2S4 diffraction peak gradually weakens; it can also be seen that as the loading increases, the characteristic diffraction peak of In2O3 is also continuously enhanced. This shows that the x%IO / ZIS sample was successfully prepared. In the prepared x%IO / ZIS sample ( Figure 5 (b)) all showed diffraction peaks belonging to the In2O3 monomer (JCPDS Card No. 71-2195), corresponding to the (222), (400), (440), and (622) crystal planes of In2O3 at 2θ = 30.59°, 35.46°, 51.02°, and 60.67°, respectively. In addition, no other impurity peaks appeared in the prepared ZnIn2S4 (JCPDS Card No. 65-2023) monomer, and characteristic diffraction peaks corresponding to the (006), (102), and (110) crystal planes appeared at 2θ of 21.59°, 27.69°, and 47.18°.

[0041] The photocatalytic activity of the x%IO / ZIS sample was tested by the synergistic reaction of photocatalytic CO2 reduction and selective oxidation of aromatic alcohols. Figure 6 As shown in Figure 2, the CO2 reduction activity also shows a regular change with the increase of In2O3 content in x%IO / ZIS. The CO2 generation rate shows a trend of increasing first and then decreasing. When x=30, the CO2 generation rate reaches a maximum of 84.09 μmol·g -1 ·h -1, which are 64.19 and 84.09 times that of the monomers ZnIn2S4 and In2O3, respectively. Some H2 is also produced during the photocatalytic process. When 10≦x≦50 in the x%IO / ZIS sample, the H2 generation rate shows a trend of first decreasing and then increasing, forming a competitive reaction with the generation of CO. When x>50 in the x%IO / ZIS sample, both the H2 production rate and the CO generation rate show a decreasing trend. Further analysis of the liquid after the reaction revealed that benzyl alcohol was selectively oxidized to benzaldehyde during the photocatalytic process, with a selectivity of 93.98%. The generation rate of benzaldehyde is basically consistent with the generation rate of the reduction products CO and H2. The slight difference may be due to the dissolution of some gases in DMF.

[0042] The photocatalytic activity test results of the prepared x% IO / ZIS samples showed that the 30% IO / ZIS sample exhibited the best catalytic activity. Therefore, the stability of the sample was studied by extending the reaction time in Example 5 using the 30% IO / ZIS photocatalyst. The results are shown in Figure 5. Figure 7 As shown in the figure, when the reaction time is extended to 20h, the amount of CO, H2 and Ph-CHO produced is 1031.39μmol·g -1 , 1157.87 μmol·g -1 and 2273.20 μmol·g -1 Due to the photocorrosion of sulfides, the generation rates of oxidation and reduction products decreased slightly with increasing reaction time, but eventually the reaction rate stabilized. Therefore, IO / ZIS has good photostability in this reaction system.

[0043] In addition, the apparent quantum efficiency of 30% IO / ZIS sample was investigated under the photocatalytic reaction conditions. Figure 8 As shown in Figure 2, the apparent quantum efficiency of the sample gradually decreases with the increase of λ. The maximum value appears at λ = 400 nm (CO: 1.33%, H2: 0.70%, benzaldehyde: 2.53%).

[0044] To explore the versatility of the x%IO / ZIS sample, the photocatalytic activity of the 30%IO / ZIS sample was tested in different aromatic alcohol systems using the same method as in Example 5. In addition to benzyl alcohol, 4-chlorobenzyl alcohol, 4-fluorobenzyl alcohol, 4-methoxybenzyl alcohol, and 4-nitrobenzyl alcohol were also selected. The production rates of the oxidation product X-PhCHO and the reduction products CO and H2 were as follows: Figure 9 As shown, benzyl alcohol was found to be the most active.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of a one-dimensional tubular In2O3 / ZnIn2S4 composite material in the synergistic reaction of photocatalytic CO2 reduction and selective oxidation of benzyl alcohol, characterized in that: The synthesis method of the one-dimensional tubular In2O3 / ZnIn2S4 composite material comprises the following steps: (1) Preparation of precursor In-MIL-68: In(NO3)2·xH2O and terephthalic acid were used as raw materials and N,N-dimethylformamide (DMF) was used as solvent to synthesize the precursor In-MIL-68 in an oil bath. (2) Preparation of In2O3 microtubes: In-MIL-68 precursor was placed in a muffle furnace for calcination to obtain In2O3 microtubes; (3) Preparation of one-dimensional tubular In2O3 / ZnIn2S4 composite material: The In2O3 microtubes were added to a round-bottom flask containing an aqueous solution and stirred for 30 min. ZnCl2, InCl3 and thioacetamide were then added in sequence. A one-dimensional tubular x% In2O3 / ZnIn2S4 composite material was obtained by low-temperature oil bath reaction, where x represents the mass ratio of In2O3 in the composite material; x is 30.

2. The use according to claim 1, characterized in that The specific method of step (1) is as follows: 1.20 g of In(NO3)2·xH2O and 1.20 g of terephthalic acid are dissolved in 100 mL of DMF, stirred for 10 min, and then the formed solution is reacted in an oil bath at 120 °C for 2 h. After the solution is cooled to room temperature, the white precipitate is collected and washed three times with C2H5OH. The product is vacuum dried at 60 °C for 10 h to obtain the precursor In-MIL-68.

3. The use according to claim 1, characterized in that The specific method of step (2) is as follows: the precursor In-MIL-68 is placed in a muffle furnace, first heated to 120 ° C in an air atmosphere and kept annealed for 2 h, then heated to 500 ° C and further calcined for 2 h, and finally cooled to room temperature to obtain In2O3 microtubes.

4. The use according to claim 1, characterized in that The specific method of step (3) is as follows: weigh a certain amount of In2O3, add it to a round-bottom flask with 100 mL of pH=2 aqueous solution, stir for 30 min, then add 0.272 g ZnCl2, 0.442 g InCl3 and 0.300 g thioacetamide in sequence, stir for 5 min, and then transfer the resulting mixture to an 80°C oil bath to react for 2 h; after the reaction is completed, cool to room temperature, wash the product with ethanol three times, and vacuum dry at 60°C for 10 h to obtain a one-dimensional tubular x% In2O3 / ZnIn2S4 composite material.

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