A binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst and its preparation and application

Abstract

The present invention relates to a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst and its preparation method and application. In the present invention, flaky In2O3 is first prepared by a method of water bath heating and high-temperature calcination; then the flaky In2O3 powder is dissolved in deionized water to obtain an In2O3 suspension; then FeCl3·6H2O and FeCl2·4H2O are dissolved in the In2O3 suspension, and an appropriate amount of NH3·H2O is added, and ultrasonic stirring is carried out to obtain a uniformly dispersed liquid; the obtained dispersed liquid is placed in a water bath pot for heating; after cooling to room temperature, the solid product is collected, washed and dried. By adding Fe3O4 to flaky In2O3 in the present invention, the effect of In2O3 in reducing CO2 to CO and CH4 can be significantly improved. The Fe3O4 particles are loaded on the upper surface of the layered In2O3, which is more conducive to the full contact with carbon dioxide gas, and at the same time can improve the stability of the catalyst. By introducing magnetic Fe3O4 into the catalyst in the present invention, it is beneficial to the secondary recycling of the catalyst, and is more energy-saving and environmentally friendly. The process of the present invention is simple and the preparation cost is low; it is conducive to large-scale industrial production and application.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalysts, and particularly relates to a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst, a preparation method thereof and an application thereof. Background Art

[0002] Nowadays, with the continuous consumption of fossil energy, the content of carbon dioxide in the atmosphere is getting higher and higher, and the resulting energy problems and the impact of the greenhouse effect are becoming more and more significant. Therefore, solving the global energy crisis and addressing global climate change issues are important tasks in the current scientific community. As is well known, carbon dioxide is the most important greenhouse gas in the atmosphere. The Intergovernmental Panel on Climate Change (IPCC) has made predictions for the situation in 2100. By then, the global average temperature will rise by 1.9 °C, and the CO2 concentration will reach 590 ppm. Due to the greenhouse effect causing global warming, a series of impacts are likely to occur. For example, the impact on terrestrial ecosystems; the impact on agriculture: it may be due to sea-level rise, seawater intrusion into groundwater, or flooding of farmland in coastal areas, as well as the impact on fisheries; in the face of the above problems, if solar energy can be used to chemically reduce CO2 to higher-energy compounds such as methane and methanol, then this can not only reduce the content of CO2 in the atmosphere, but also alleviate or solve the energy crisis. That is, using photocatalytic technology to convert these "waste gases" into organic fuel products is undoubtedly a better way.

[0003] CO2 reduction can be driven by different energy forms, such as photocatalysis, electrocatalysis, thermocatalysis, and photoelectrocatalysis, etc. They all reduce CO2 to corresponding products under specific circumstances. However, photocatalytic conversion can directly use light energy as an energy source, consumes less energy than other catalytic methods and is environmentally friendly, and is more in line with the development direction of future research from the perspective of green energy. Moreover, the CO2 molecule itself has good optical stability in the ultraviolet-visible light region, and it is necessary to use a suitable photocatalyst to transfer photoelectrons to CO2 to complete the entire reduction process. The reduction of single-electron CO2 is very difficult, and its redox potential is very high (Eθ = -1.9 V vs NHE, pH = 7), while the multi-electron reduction system assisted by protons is more likely to achieve the reduction of CO2. According to the number of electrons transferred during the reduction process, there are many reduction products of CO2, such as HCOOH, CO, HCHO, CH3OH, CH4, etc.

[0004] Indium(III) oxide (In2O3) is an important n-type semiconductor metal oxide with a band gap of 2.6 eV. According to research, the surface defects of In2O3 lead to low separation rate, high recombination rate, and low quantum efficiency of photogenerated electron-hole pairs, making it difficult to separate. Therefore, it is necessary to load other substances to improve its performance to meet market demands. Summary of the Invention

[0005] The object of the present invention is to provide a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst and its preparation method and application, so as to solve the existing technical problems.

[0006] A preparation method of a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst includes the following steps:

[0007] (1) Prepare flaky In2O3 powder;

[0008] (2) Dissolve the flaky In2O3 powder in deionized water to obtain an In2O3 suspension;

[0009] (3) Dissolve FeCl3·6H2O and FeCl2·4H2O in the In2O3 suspension prepared in step (2), and add an appropriate amount of NH3·H2O, and ultrasonically stir to obtain a uniformly dispersed solution;

[0010] (4) Put the obtained dispersed solution into a water bath for heating;

[0011] (5) After cooling to room temperature, collect the solid product, wash and dry it to obtain a Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores.

[0012] Further, the preparation of the flaky In2O3 powder in step (1) includes: dissolving In(NO3)3·xH2O in deionized water, then adding NH3·H2O, putting it into a water bath at 80-100 °C and heating for 60-120 min, collecting the solid substance in the solution, washing and drying, and then putting the sample into a crucible, and reacting in a muffle furnace at 350-400 °C for 3-6 h.

[0013] Further, 0.1-0.2 g of In(NO3)3·xH2O is added to every 100 μL of NH3·H2O with a mass fraction of 25%.

[0014] Further, 0.25-0.30 g of flaky In2O3 powder is added to every 1 mL of deionized water in step (2).

[0015] Further, the dosage ratio of In2O3, FeCl3·6H2O, FeCl2·4H2O to NH3·H2O in step (3) is 0.25-0.35 g: 1-4 mmol: 0.5-2 mmol: 7.5-30 mL. Reasonably controlling the ratio of FeCl3·6H2O and FeCl2·4H2O is beneficial to obtaining a higher content of Fe3O4. The addition ratio of NH3·H2O also has a great influence on the final product.

[0016] Further, in step (4), the heating temperature in the water bath is 80 - 100 °C, and the heating time is 30 - 60 min.

[0017] The binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared by the above method.

[0018] Further, the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst has a binary lamellar mesoporous structure, and Fe3O4 particles are loaded on the upper surface of layered In2O3, which is more conducive to sufficient contact with carbon dioxide gas. Moreover, the introduction of magnetic Fe3O4 makes the composite photocatalyst more conducive to secondary utilization and reduces costs.

[0019] The application of the above binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst as a photocatalyst.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) The present invention uses a method of water bath heating and high-temperature calcination to prepare flaky In2O3, with a simple process and low preparation cost;

[0022] (2) The present invention adds Fe3O4 to flaky In2O3, solving the problems of low separation rate, high recombination rate, low quantum efficiency, and difficult separation of photogenerated electron-hole pairs caused by surface defects of In2O3; improving the photocatalytic activity of In2O3 towards CO2, the Fe3O4 / In2O3 composite photocatalyst of the present invention has a significant improvement in the effects of reducing CO2 to CO and CH4 compared with monomeric In2O3;

[0023] (3) The Fe3O4 / In2O3 composite photocatalyst prepared by the present invention has a novel structure, and Fe3O4 particles are loaded on the upper surface of layered In2O3, which is more conducive to sufficient contact with carbon dioxide gas and can improve the stability of the catalyst at the same time;

[0024] (4) The present invention introduces magnetic Fe3O4 into the catalyst, which is conducive to the secondary recovery and utilization of the catalyst, and is more energy-saving and environmentally friendly. Description of the Drawings

[0025] Figure 1 is the XRD pattern of the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared in Example 1 of the present invention;

[0026] Figure 2 is the TEM image of the flaky In2O3 prepared in Example 1 of the present invention;

[0027] Figure 3 is the TEM image of the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared in Example 1 of the present invention;

[0028] Figure 4 It is the infrared spectrum effect diagram of the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared in Example 1 of the present invention;

[0029] Figure 5 It is the effect diagram of the reduction of CO2 to CO by the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared in Example 1 of the present invention;

[0030] Figure 6 It is the effect diagram of the reduction of CO2 to CH4 by the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared in Example 1 of the present invention. Detailed implementation manners

[0031] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] A preparation method of a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst includes the following steps:

[0034] (1) Prepare In2O3 sample: Dissolve 0.308 g of In(NO3)3·xH2O in deionized water, then add 300 μL of NH3·H2O (25%), put the obtained suspension into a water bath at 80 °C, heat for 60 min, collect the solid substance in the solution, wash and dry it, then put the sample into a crucible, and use a muffle furnace at 350 °C with a heating rate of 5 °C / min -1 , react for 3 h to obtain the In2O3 sample.

[0035] (2) Add the prepared In2O3 to deionized water at 0.25 g / mL to obtain a suspension of In2O3;

[0036] (3) Add FeCl3·6H2O, FeCl2·4H2O to the suspension of In2O3, and add an appropriate amount of NH3·H2O, and ultrasonically stir to obtain a uniformly dispersed liquid. The dosage ratio of In2O3, FeCl3·6H2O, FeCl2·4H2O to NH3·H2O is 0.308 g: 0.045 g: 0.0165 g: 15 mL.

[0037] (4) Put the obtained dispersion into a water bath at 80 °C for 30 min

[0038] (5) After cooling to room temperature, collect the solid product, wash and dry it to obtain a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst.

[0039] Example 2

[0040] A preparation method of a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst, comprising the following steps:

[0041] (1) Preparation of In2O3 sample: Dissolve 0.308 g of In(NO3)3·xH2O in deionized water, then add 300 μL of NH3·H2O (25%), put the obtained suspension into an 80°C water bath, heat for 60 min, collect the solid substance in the solution, wash and dry, then put the sample into a crucible, and use a muffle furnace at 350°C with a heating rate of 5°C / min -1 , react for 3 h to obtain the In2O3 sample.

[0042] (2) Add the prepared In2O3 to deionized water at 0.25 g / mL to obtain a suspension of In2O3;

[0043] (3) Dissolve FeCl3·6H2O and FeCl2·4H2O in the suspension of In2O3, and add an appropriate amount of NH3·H2O, and ultrasonically stir to obtain a uniformly dispersed solution. The dosage ratio of In2O3, FeCl3·6H2O, FeCl2·4H2O to NH3·H2O is 0.308 g:0.1351 g:0.0495:15 mL.

[0044] (4) Put the obtained dispersion into a water bath at 80°C for 30 min

[0045] (5) After cooling to room temperature, collect the solid product, wash and dry to obtain a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst.

[0046] Example 3

[0047] A preparation method of a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst, comprising the following steps:

[0048] (1) Preparation of In2O3 sample: Dissolve 0.308 g of In(NO3)3·xH2O in deionized water, then add 300 μL of NH3·H2O (25%), put the obtained suspension into an 80°C water bath, heat for 60 min, collect the solid substance in the solution, wash and dry, then put the sample into a crucible, and use a muffle furnace at 350°C with a heating rate of 5°C / min -1 , react for 3 h to obtain the In2O3 sample.

[0049] (2) Add the prepared In2O3 to deionized water at 0.25 g / mL to obtain a suspension of In2O3;

[0050] (3) Dissolve FeCl3·6H2O and FeCl2·4H2O in the suspension of In2O3, and add an appropriate amount of NH3·H2O. Stir ultrasonically to obtain a uniformly dispersed solution. The dosage ratio of In2O3, FeCl3·6H2O, FeCl2·4H2O to NH3·H2O is 0.308 g:0.2703 g:0.099 g:15 mL.

[0051] (4) Put the obtained dispersed solution into a water bath at 80 °C for 30 min of heating time.

[0052] (5) After cooling to room temperature, collect the solid product, wash and dry it to obtain the Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores.

[0053] Experimental results

[0054] 1. XRD

[0055] Perform XRD tests on the Fe3O4 / In2O3 composite photocatalysts with binary lamellar mesopores prepared in Examples 1 - 3. The XRD pattern of the Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores prepared in Example 1 is as Figure 1 shown. It can be seen that the binary composite photocatalyst Fe3O4 / In2O3, In2O3 and Fe3O4 are successfully prepared. The XRD patterns of the Fe3O4 / In2O3 composite photocatalysts with binary lamellar mesopores prepared in Example 2 and Example 3 are similar to that in Example 1.

[0056] 2. TEM

[0057] The flaky In2O3 prepared in Example 1 is as Figure 2 shown. It can be seen that In2O3 presents an irregular flaky structure with uneven pore distribution on the surface. The TEM image of the Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores prepared in Example 1 is as Figure 3 shown. It can be seen that small Fe3O4 particles are loaded on In2O3. And it has a regular lamellar mesoporous structure, further indicating that Fe3O4 / In2O3 constitutes a lamellar mesoporous structure. The TEM images of the Fe3O4 / In2O3 composite photocatalysts with binary lamellar mesopores prepared in Example 2 and Example 3 are similar to that in Example 1.

[0058] 3. Infrared spectrum

[0059] Figure 4 The middle one is the infrared spectrum of In2O3 and the Fe3O4 / In2O3 composite photocatalyst prepared in Example 1. It can be seen from the figure that at 800 cm -1The following region is the vibration region of In-O-In; and four sharp peaks appear at 604, 565, 538, and 436 cm -1 This further indicates the successful preparation of In2O3. The infrared spectrum of the Fe3O4 / In2O3 composite photocatalyst shows the successful preparation of the binary composite catalyst. The infrared spectra of the Fe3O4 / In2O3 composite photocatalysts with binary lamellar mesopores prepared in Example 2 and Example 3 are similar to that in Example 1.

[0060] 4. CO2 reduction performance

[0061] Evaluation of CO2 reduction performance: It is carried out in a carbon dioxide reduction instrument. Add 0.05 g of photocatalyst, as well as a certain proportion of triethanolamine, acetonitrile, and sodium hydroxide into the reaction kettle. After introducing CO2 for a period of time, open the valves of the required carrier gas source and the light source for dynamic adsorption. Start the hydrogen generator to control the reaction system temperature at 60 °C. After reaching the adsorption equilibrium, quickly add a quantitative gas sample to the upper end of the chromatographic column, and take samples every 1 hour. Detect the reduction effect of CO2 through the detector of the detection system.

[0062] Figure 5 This is the effect diagram of the Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores in Example 1 for reducing CO2 to CO. By comparing the effects of In2O3 and Fe3O4 / In2O3 on the photocatalytic reduction of carbon dioxide system, it can be seen that the binary Fe3O4 / In2O3 composite photocatalyst has a significant improvement in the effect of reducing CO2 to CO compared with the monomer In2O3.

[0063] Figure 6 This is the effect diagram of the Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores in Example 1 for reducing CO2 to CH4. By comparing the effects of In2O3 and Fe3O4 / In2O3 on the photocatalytic reduction of carbon dioxide system, it can be seen that the binary Fe3O4 / In2O3 composite photocatalyst has a significant improvement in the effect of reducing CO2 to CH4 compared with the monomer In2O3.

[0064] 5. Stability

[0065] The Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores in Example 1 was subjected to 5 cyclic experiments, and the change in the photocatalytic degradation rate was very small, indicating that the prepared Fe3O4 / In2O3 composite photocatalyst with binary lamellar mesopores has good photochemical stability.

Claims

1. A preparation method of a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst, characterized in that, It includes the following steps: (1) Prepare flaky In2O3 powder: Dissolve In(NO3)3·xH2O in deionized water, then add NH3·H2O, place it in a water bath at 80 - 100 °C and heat for 60 - 120 min. Collect the solid substance in the solution, wash and dry it, then put the sample into a crucible and react in a muffle furnace at 350 - 400 °C for 3 - 6 h; (2) Dissolve the flaky In2O3 powder in deionized water to obtain an In2O3 suspension; (3) Dissolve FeCl3·6H2O and FeCl2·4H2O in the In2O3 suspension prepared in step (2), and add an appropriate amount of NH3·H2O, and ultrasonically stir to obtain a uniformly dispersed liquid; (4) Put the obtained dispersed liquid into a water bath and heat; (5) After cooling to room temperature, collect the solid product, wash and dry it to obtain a binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst.

2. The preparation method according to claim 1, characterized in that, In step (1), 100 μL of NH3·H2O with a mass fraction of 25% is added to every 0.1 - 0.2 g of In(NO3)3·xH2O.

3. The preparation method according to claim 1, characterized in that, In step (2), 0.25 - 0.30 g of flaky In2O3 powder is added to every 1 mL of deionized water.

4. The preparation method according to claim 1, characterized in that, In step (3), the dosage ratio of In2O3 suspension, FeCl3·6H2O, FeCl2·4H2O and NH3·H2O is 0.25 - 0.35 g : 1 - 4 mmol : 0.5 - 2 mmol : 7.5 - 30 mL.

5. The preparation method according to claim 1, characterized in that, In step (4), the heating temperature in the water bath is 80 - 100 °C and the heating time is 30 - 60 min.

6. The binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst prepared by the method according to any one of claims 1 - 5.

7. The binary sheet-like mesoporous Fe3O4 / In2O3 composite photocatalyst according to claim 6, characterized in that, It has a binary lamellar mesoporous structure, and Fe3O4 particles are loaded on the upper surface of layered In2O3.

8. Use of the binary lamellar mesoporous Fe3O4 / In2O3 composite photocatalyst according to claim 7, characterized in that, As a photocatalyst.

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