Preparation method and application of sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst

Abstract

The invention relates to a preparation method and application of a sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, and belongs to the technical field of photocatalytic materials. The preparation method comprises the following steps: preparing ZnTiO3 by adopting a sol-gel method, preparing g-C3N4 by adopting a calcination method, uniformly stirring ZnTiO3, g-C3N4 and a sulfur-rich precursor, and carrying out hydrothermal treatment to obtain the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst which can be applied to the field of photocatalytic hydrogen evolution. Compared with an existing photocatalyst, the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst disclosed by the invention is good in controllability and high in stability, has a good light absorption characteristic, is beneficial to preventing photogenerated electrons and hole recombination, and further improves the separation efficiency of current carriers. The method is green and environment-friendly, simple, convenient to operate and low in material preparation cost, conforms to the green and environment-friendly concept advocated at present, and has a wide application market prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic materials, and specifically relates to a preparation method and application of a sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst. Background Art

[0002] Photocatalytic hydrogen evolution technology, as a clean and efficient method for generating hydrogen energy, has attracted extensive attention from researchers around the world in recent years. With the increasing depletion of fossil fuels and the intensification of environmental pollution problems, seeking new energy sources for sustainable development has become an urgent task. Hydrogen energy, with its high energy density and zero emissions (only water production) and environmental protection characteristics, is regarded as an ideal clean energy carrier. However, traditional hydrogen production methods such as water electrolysis and natural gas reforming generally have problems of high energy consumption and high cost, which limits the large-scale application of hydrogen energy. Although there are still some challenges, with the advancement of science and technology, photocatalytic hydrogen evolution is expected to play a key role in the future clean energy system and provide strong support for solving the energy crisis and environmental protection.

[0003] Thiourea can improve the separation efficiency of photogenerated electrons and holes in photocatalysts, thereby enhancing photocatalytic activity. As an electron transfer mediator, thiourea can promote photoexcited redox reactions. At the same time, the introduction of thiourea can improve the stability of photocatalytic materials, making them more durable during the photocatalytic process. Zinc titanate (ZnTiO3) is a narrow bandgap (~3.29eV) semiconductor with excellent photoexcitation performance. Carbon nitride (g-C3N4) is a non-metallic semiconductor material with a unique two-dimensional layered structure that can effectively capture visible light and exhibits a high light absorption efficiency even in the low-energy region of the solar spectrum, making it a popular candidate material in solar energy conversion and storage systems. The present invention constructs a sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalytic material that can effectively inhibit the recombination of photogenerated electrons and holes, thereby improving photocatalytic activity. There have been no reports on the role of sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalysts in decomposing hydrogen from water. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a preparation method and application of a sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst.

[0005] The technical solution adopted by the present invention is: a sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, the preparation method of which comprises the following steps:

[0006] ZnTiO3 nanoparticles, g-C3N4 nanosheets and sulfur-rich precursors are dispersed in deionized water, fully stirred, and then transferred to a hydrothermal synthesis reactor lined with polytetrafluoroethylene for high temperature and high pressure treatment. After natural cooling, the product is washed several times, dried and ground to finally obtain the target product S-ZnTiO3 / g-C3N4 nanoparticle photocatalyst.

[0007] The above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst has a mass ratio of ZnTiO3 nanoparticles: g-C3N4 nanosheets: sulfur-rich precursor of 20:7:20.

[0008] In the above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, the sulfur-rich precursor is thiourea.

[0009] The above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst has a high-temperature treatment temperature of 160°C and a holding time of 12 hours.

[0010] The above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, the preparation method of ZnTiO3 nanoparticles is as follows:

[0011] 1) Disperse zinc acetate dihydrate in anhydrous ethanol, then add a small amount of nitric acid solution, stir thoroughly until dissolved, and record it as solution A; disperse tetrabutyl titanate in anhydrous ethanol, stir thoroughly until dissolved, and record it as solution B;

[0012] 2) Solution A was added dropwise to solution B and the mixture was stirred for 1 hour, and then the mixture was transferred to an oven for drying overnight. The obtained dry sample was ground and placed in a muffle furnace for calcination. After naturally cooling to room temperature, the obtained product was fully ground to obtain the product ZnTiO3 nanoparticles.

[0013] In the above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, in step 2), the calcination temperature is 600°C, the calcination time is 4h, and the heating rate is 5°C / min.

[0014] The preparation method of the above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, g-C3N4 nanosheets is as follows: melamine is placed in a muffle furnace for calcination, and after naturally cooling to room temperature, the obtained product is fully ground to obtain the product g-C3N4 nanosheets.

[0015] The above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst has a calcination temperature of 520°C, a calcination time of 2h, and a heating rate of 2°C / min.

[0016] Application of the above-mentioned sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst in photocatalytic hydrogen evolution.

[0017] The above application method is as follows: the above sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst is placed in a reactor containing a mixed solution of deionized water, triethanolamine and chloroplatinic acid; argon gas is introduced to exhaust the air; and photocatalytic hydrogen evolution is carried out under visible light irradiation.

[0018] The beneficial effects of the present invention are:

[0019] 1. The present invention uses a sol-gel method, a calcination method and a hydrothermal method to prepare a sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, and realizes efficient separation of photogenerated carriers.

[0020] 2. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared by the present invention has good photocatalytic hydrogen evolution performance, and the method is simple, convenient, low-cost, mild in conditions, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 X-ray diffraction patterns of the ZnTiO3 catalyst prepared in Example 1, the g-C3N4 catalyst prepared in Example 2, and the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared in Example 3.

[0022] Figure 2 Fourier transform infrared spectrum of the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared in Example 3.

[0023] Figure 3 The photocatalytic hydrogen evolution activity of the ZnTiO3 catalyst prepared in Example 1, the g-C3N4 catalyst prepared in Example 2 and the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared in Example 3. DETAILED DESCRIPTION

[0024] Example 1

[0025] The preparation method of ZnTiO3 catalyst is as follows:

[0026] Disperse 2.19g zinc acetate dihydrate in a beaker containing 10mL of anhydrous ethanol, then add 3mL of nitric acid solution, stir thoroughly with a magnetic stirrer until dissolved, and obtain zinc acetate solution; disperse 3mL of tetrabutyl titanate in a beaker containing 10mL of anhydrous ethanol, stir thoroughly to dissolve, and obtain tetrabutyl titanate solution. Add zinc acetate solution dropwise to tetrabutyl titanate solution, stir with a magnetic stirrer for 1h, then transfer the mixed solution to an oven and dry overnight, grind the obtained dry sample and evenly distribute it on the bottom of the porcelain ark, seal the porcelain ark with two layers of aluminum foil, transfer to a muffle furnace and heat to 600℃ at a rate of 5℃ / min, and keep at 600℃ for 4h, and after cooling naturally to room temperature, grind the obtained product thoroughly to obtain the product ZnTiO3 nanoparticle photocatalyst.

[0027] Example 2

[0028] The preparation method of g-C3N4 catalyst is as follows:

[0029] 2 g of melamine was evenly distributed on the bottom of the porcelain ark, which was sealed with two layers of aluminum foil and transferred to a muffle furnace and heated to 520 °C at a rate of 2 °C / min and maintained at 520 °C for 2 h. After naturally cooling to room temperature, the product was fully ground to obtain the product g-C3N4 nanosheet photocatalyst.

[0030] Example 3

[0031] Take 0.2 g of ZnTiO3 nanoparticles in Example 1, 0.1 g of g-C3N4 nanosheets in Example 2, and 0.1 g of thiourea, place them in a beaker filled with 50 mL of deionized water, stir them thoroughly, and then place them in a hydrothermal synthesis reactor lined with polytetrafluoroethylene for high temperature and high pressure treatment, keep them at 160°C for 12 hours, and after natural cooling, wash the product several times, dry it, and then grind it to finally obtain the target product S-ZnTiO3 / g-C3N4 nanophotocatalyst.

[0032] Example 4

[0033] Figure 1 X-ray diffraction patterns of the ZnTiO3 catalyst prepared in Example 1, the g-C3N4 prepared in Example 2, and the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared in Example 3. Figure 1The characteristic diffraction peak at 2θ=23.5° corresponds to the (002) crystal plane of g-C3N4. No characteristic diffraction peak of sulfur was detected in the composite sample S-ZnTiO3 / g-C3N4 photocatalyst, which is due to the weak peak and low content intensity of sulfur. The characteristic peaks of g-C3N4 and ZnTiO3 can be observed in the composite sample sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, indicating that the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst was successfully prepared.

[0034] Example 5

[0035] Figure 2 Fourier transform infrared spectrum of sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared in Example 3. -1 The characteristic peak at 3419 cm -1 The characteristic peaks at 1637 and 1417 cm correspond to the stretching and bending vibrations of absorbed water molecules. -1 The characteristic peak at 1358cm corresponds to the CN and C=N bond stretching vibrations on the carbon nitrogen heterocycle. -1 The stretching vibration peak of NC=S was found at 3250cm -1 The broad absorption band at can be attributed to the NH bond.

[0036] Example 6

[0037] Application of sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst in catalytic water decomposition and hydrogen evolution under light:

[0038] 1) Under normal temperature and pressure conditions, 25 mg of the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst is placed in a reactor containing a mixed solution of 18 mL of deionized water, 2 mL of triethanolamine and 25 μL of chloroplatinic acid; argon is introduced into the reactor at a rate of 40 mL / min for 40 min to exhaust the air; under visible light irradiation, 1000 μL of the gas in the reactor is extracted every 30 min, and the collected catalytic products are quantitatively analyzed using a gas chromatograph.

[0039] 2) Follow the operation of step 1), except that the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst prepared in Example 3 is replaced by the ZnTiO3 catalyst prepared in Example 1 and the g-C3N4 catalyst prepared in Example 2, respectively, and other conditions remain unchanged. Take their gases respectively and measure the hydrogen production efficiency.

[0040] Figure 3The graph is the relationship between hydrogen content and irradiation time. The peak area of ​​the extracted gas is measured by gas chromatograph and then converted into the amount of substance by calculation, such as Figure 3 As shown, after 3 hours, the H2 yield of the ZnTiO3 catalyst was 2047.42 μmol / g, and the H2 yield of the g-C3N4 catalyst was 2832.91 μmol / g, both of which had low activity; the H2 yield of the composite sample S-ZnTiO3 photocatalyst was 8241.20 μmol / g, which was higher than that of the ZnTiO3 catalyst and the g-C3N4 catalyst, indicating that constructing heterogeneous structures and heteroatom doping can effectively improve the hydrogen evolution performance.

Claims

1. A sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst, characterized in that: The preparation method comprises the following steps: ZnTiO3 nanoparticles, g-C3N4 nanosheets and sulfur-rich precursors are dispersed in deionized water, fully stirred, and then transferred to a hydrothermal synthesis reactor lined with polytetrafluoroethylene for high temperature and high pressure treatment. After natural cooling, the product is washed several times, dried and ground to finally obtain the target product S-ZnTiO3 / g-C3N4 nanoparticle photocatalyst.

2. A sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 1, characterized in that: By mass ratio, ZnTiO3 nanoparticles: g-C3N4 nanosheets: sulfur-rich precursor is 20:7:

20.

3. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 1, characterized in that: The sulfur-rich precursor is thiourea.

4. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 1, characterized in that: The high temperature treatment temperature is 160° C. and the holding time is 12 hours.

5. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 1, characterized in that: The preparation method of ZnTiO3 nanoparticles is as follows: 1) Disperse zinc acetate dihydrate in anhydrous ethanol, then add a small amount of nitric acid solution, stir thoroughly until dissolved, and record it as solution A; disperse tetrabutyl titanate in anhydrous ethanol, stir thoroughly until dissolved, and record it as solution B; 2) Solution A was added dropwise to solution B and the mixture was stirred for 1 hour, and then the mixture was transferred to an oven for drying overnight. The obtained dry sample was ground and placed in a muffle furnace for calcination. After naturally cooling to room temperature, the obtained product was fully ground to obtain the product ZnTiO3 nanoparticles.

6. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 5, characterized in that: In step 2), the calcination temperature is 600° C., the calcination time is 4 hours, and the heating rate is 5° C. / min.

7. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 1, characterized in that: The preparation method of g-C3N4 nanosheets is as follows: melamine is placed in a muffle furnace for calcination, and after naturally cooling to room temperature, the obtained product is fully ground to obtain the product g-C3N4 nanosheets.

8. The sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to claim 7, characterized in that: The calcination temperature is 520°C, the calcination time is 2h, and the heating rate is 2°C / min.

9. Use of the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst according to any one of claims 1 to 8 in photocatalytic hydrogen evolution.

10. The use according to claim 9, characterized in that: The method is as follows: placing the sulfur-doped ZnTiO3 / g-C3N4 heterojunction photocatalyst described in any one of claims 1 to 8 into a reactor containing a mixed solution of deionized water, triethanolamine and chloroplatinic acid; introducing argon gas to exhaust air; and performing photocatalytic hydrogen evolution under visible light irradiation.

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