阅读说明：本技术 一种溴化铅铯/二氧化钛复合光催化剂材料的制备方法 (Preparation method of lead cesium bromide/titanium dioxide composite photocatalyst material ) 是由 陈智 钱笑笑 魏其艳 杨秀茹 赵婉 刘纯希 于 2020-06-15 设计创作，主要内容包括：本发明公开一种溴化铅铯/二氧化钛复合光催化剂材料的制备方法,包括一、通过溶剂法制备溴化铅铯纳米颗粒；二、通过溶剂热法制备溴化铅铯/二氧化钛复合光催化剂材料。本发明通过简单的溶剂热法制备出了溴化铅铯/二氧化钛复合光催化剂材料,得到的复合光催化剂材料具有良好的水稳定性,使其能在可见光照射下高效的降解盐酸四环素,说明其在水中具有优良的光催化性能。(The invention discloses a preparation method of a lead cesium bromide/titanium dioxide composite photocatalyst material, which comprises the steps of preparing lead cesium bromide nano-particles by a solvent method; secondly, preparing the lead cesium bromide/titanium dioxide composite photocatalyst material by a solvothermal method. The lead cesium bromide/titanium dioxide composite photocatalyst material is prepared by a simple solvothermal method, and the obtained composite photocatalyst material has good water stability, so that tetracycline hydrochloride can be efficiently degraded under the irradiation of visible light, and the excellent photocatalytic performance of the composite photocatalyst material in water is proved.)

1. A preparation method of a lead cesium bromide/titanium dioxide composite photocatalyst material is characterized by comprising the following steps:

1) adding 0.1-0.3 mmol of cesium carbonate and 0.4-1.2 mmol of lead bromide into a beaker containing 18-60 mL of octadecene, 2-6 mL of oleic acid and 1-3 mL of oleylamine, and stirring for a certain time at a certain temperature until the cesium carbonate and the lead bromide are dissolved. Then transferring the mixture into a high-pressure reaction kettle with a polytetrafluoroethylene lining, putting the reaction kettle into an oven, and reacting for 240 minutes at 120 ℃. Naturally cooling to room temperature and centrifuging, adding 5-15 mL of hexane into the product, centrifuging at 8000rpm for 5 minutes, repeatedly washing for 3 times, centrifuging to collect the product, adding 5-15 mL of isopropanol, washing for 3 times in the same step, removing residual reactants, and collecting the product to obtain the lead cesium bromide nano-particles.

2) Weighing a certain amount of the lead cesium bromide nano-particles prepared in the step 1), and adding the nano-particles into 42-60 mL of isopropanol. After stirring the solution for a few minutes, a certain amount of isopropyl titanate was added separately. Then the reaction solution was transferred to a high pressure autoclave lined with polytetrafluoroethylene and placed in an oven and kept at 200 ℃ for 24 hours. And cooling to room temperature, collecting the product by centrifugation, repeatedly washing the product with ethanol for a plurality of times, drying the product at a certain temperature for a certain time, heating all the products to 400 ℃ at a speed of 1 ℃/min, calcining the products for 2 hours, and grinding the products for 30 to 40 minutes to obtain the highly-crystallized lead cesium bromide/titanium dioxide composite photocatalyst material.

2. The method according to claim 1, wherein in the step 1), the certain temperature is 25 to 35 ℃ and the certain time is 20 to 30 minutes.

3. The preparation method of claim 1, wherein in the step 2), the amount of the cesium lead bromide nanoparticles is 0.2-0.3 g, and the amount of isopropyl titanate is 0.5mL, 1mL, 1.5mL, 2 mL.

4. The method according to claim 1, wherein the ethanol is repeatedly washed 3 to 5 times in the step 2).

5. The preparation method according to claim 1, wherein in the step 2), the drying is performed at a certain temperature of 60 ℃ for a certain time of 10 to 12 hours.

Technical Field

The invention relates to a preparation method of a lead cesium bromide/titanium dioxide composite photocatalyst material, belonging to the technical field of photocatalytic environment-friendly nano materials.

Background

With the rapid development of urban industrialization and the increasing demand of human beings for energy, environmental pollution and energy crisis become increasingly serious problems, and a photocatalytic technology taking sunlight as energy comes along. Compared with the traditional method, the photocatalysis technology has the advantages of low cost, simple and convenient operation, environmental protection and recyclable catalyst (Waterresearch,2010,44(10): 2997-. However, the existing photocatalytic technology still has the challenges of narrow light absorption range and easy recombination of photo-generated electrons and holes, and the factors cause low solar energy utilization rate of the photocatalyst material, so that the large-scale application of the technology is difficult to realize. Aiming at the problems, on one hand, a novel narrow-band gap material which can be applied to photocatalysis is searched, and on the other hand, the existing catalyst is modified to improve the light absorption range of the photocatalyst material and inhibit the recombination of photo-generated electrons and holes. The method is a core problem facing the existing photocatalytic technology and urgently needed to be solved, and is a new research hotspot in the technical field of photocatalysis.

Since Loredana (Nano Letters,2015,15(6): 3692-. Of these all-inorganic halide perovskites, lead cesium bromide, which has a band gap of only 2.26eV, has the advantages of unique optical and electrical properties, high absorption coefficient and wide absorption range and excellent charge carrier mobility (Advanced Energy Materials,2018, 8(26):1702073), received particular attention. Based on the excellent photoelectrochemical properties of cesium lead bromide, researchers are gradually paying attention to the application of cesium lead bromide in photoelectric conversion, and the cesium lead bromide is currently one of the most promising Materials for the photoelectric conversion field (Small,2017,13(9): 1603996; Advanced Materials,2016,28(45): 10088-. However, the main obstacle affecting the widespread use of all-inorganic perovskite nanomaterials is the poor stability due to their unique ionic structure (Science Bulletin,2017, 62(5): 369-. When perovskite nanomaterials are exposed to moisture, oxygen, high temperature or ultraviolet light, the crystal structure is easily destroyed, making material storage difficult (Nature Materials,2014,13(9): 838-. Among these external factors, moisture is one of the major problems in environmental stability of perovskite nanomaterials, and severely limits their application in the field of photoelectric conversion, especially in the field of water-mediated photocatalysis. Therefore, the problem to be solved urgently is to improve the stability of the perovskite nano material in water in the application of the perovskite nano material in the field of photocatalysis.

Currently, research has been conducted to improve the stability of lead cesium bromide, thereby solving the problem of instability of all-inorganic perovskite nanomaterials including lead cesium bromide. For example, the surface modification of the all-inorganic perovskite nanocrystal with waterproof capping ligands (Nanoscale,2017,9(2):631-636), or the encapsulation with silica (Advanced Materials,2016,28(45):10088-10094), etc. Although these organic ligands or polymers can passivate the surface and thus enhance the stability of the perovskite nanomaterials, these insulating outer layers impede charge transport, limiting their application in the photoelectric or catalytic direction. In addition, most of the inorganic shell layers such as silica are synthesized by low-temperature hydrolysis, and the obtained outer layer is amorphous, so that the stability and charge transfer properties in water are limited (Advanced Materials,2016,28(45): 10088-10094). Therefore, development of a perovskite nano material with water stability and good charge transfer characteristics is imperative, and is of great importance for practical application of a perovskite material in the field of photocatalysis.

Titanium dioxide has the advantages of low cost, no environmental pollution, good stability, excellent photoelectric property and good charge transfer property (Chemical Society Reviews,2018,47:8203-8237), and is the most widely researched metal oxide photocatalyst material in recent decades. According to the invention, the all-inorganic perovskite lead cesium bromide nano particles are compounded with titanium dioxide with good stability and high photocatalytic activity by a simple method, so that the advantages of the two are effectively combined, the stability of the lead cesium bromide in water is improved, and the separation of photoproduction electrons and holes is enhanced, thereby improving the visible light catalysis efficiency and realizing the photocatalytic application in a water system. Furthermore, a stable and efficient novel material of the all-inorganic halide perovskite visible-light-driven photocatalyst can be prepared, and the method is expected to be applied to other fields.

Disclosure of Invention

The invention provides a simple preparation method of a lead cesium bromide/titanium dioxide composite photocatalyst material, aiming at the problems that single lead cesium bromide nanoparticles are poor in stability in water and photo-generated electron holes are easy to compound, so that photocatalysis is inactivated in water. The composite material of lead cesium bromide and titanium dioxide can be prepared by a simple solvothermal method, the preparation method is simple and easy to operate, and the prepared composite photocatalyst material has good stability and photocatalytic efficiency in water and has an obvious effect on photocatalytic degradation of antibiotics in water.

The technical scheme of the invention is as follows:

1) adding 0.1-0.3 mmol of cesium carbonate and 0.4-1.2 mmol of lead bromide into a beaker containing 18-54 mL of octadecene, 2-6 mL of oleic acid and 1-3 mL of oleylamine, and stirring for a certain time at a certain temperature until the cesium carbonate and the lead bromide are dissolved. Then transferring the mixture into a high-pressure reaction kettle with a polytetrafluoroethylene lining, putting the reaction kettle into an oven, and reacting for 240 minutes at 120 ℃. Naturally cooling to room temperature and centrifuging, adding 5-15 mL of hexane into the product, centrifuging at 8000rpm for 5 minutes, repeatedly washing for 3 times, centrifuging to collect the product, adding 5-15 mL of isopropanol, synchronously washing for 3 times, removing residual reactants, and collecting the product to obtain the lead cesium bromide nano-particles.

2) Weighing a certain amount of the lead cesium bromide nano-particles prepared in the step 1), and adding the nano-particles into 42-60 mL of isopropanol. After stirring the solution for a few minutes, a certain amount of isopropyl titanate was added separately. Then the reaction solution was transferred to a high pressure autoclave lined with polytetrafluoroethylene and placed in an oven and kept at 200 ℃ for 24 hours. And cooling to room temperature, collecting the product by centrifugation, repeatedly washing the product with ethanol for a plurality of times, drying the product at a certain temperature for a certain time, heating all the products to 400 ℃ at a speed of 1 ℃/min, calcining the products for 2 hours, and grinding the products for 30 to 40 minutes to obtain the highly-crystallized lead cesium bromide/titanium dioxide composite photocatalyst material.

Wherein the certain temperature in the step 1) is 25-35 ℃, and the certain time is 20-30 minutes.

In the step 2), a certain amount of lead cesium bromide nanoparticles is 0.2-0.3 g, and a certain amount of isopropyl titanate is 0.5mL, 1mL, 1.5mL, and 2mL, respectively.

Preferably, the ethanol in the step 2) is repeatedly washed for 3-5 times; the drying temperature is 60 ℃, and the drying time is 10-12 hours.

Compared with the prior art, the invention has the beneficial effects that: the preparation method is simple, and the lead cesium bromide/titanium dioxide composite photocatalyst material can be prepared by a simple solvothermal method; compared with pure lead cesium bromide nano-particles, the titanium dioxide microspheres can effectively protect the lead cesium bromide nano-particles, remarkably improve the stability and photocatalytic performance of the lead cesium bromide/titanium dioxide composite material in water, and can efficiently degrade tetracycline hydrochloride which is a pollutant in water. The prepared lead cesium bromide/titanium dioxide composite photocatalyst material is stable in water, overcomes the environmental instability of all-inorganic perovskite lead cesium bromide to a certain extent, and opens up a new way for further developing research and application of water-resistant perovskite composite materials and novel photocatalytic composite materials.

Drawings

Fig. 1 is a scanning electron microscope image of the cesium lead bromide/titanium dioxide composite photocatalyst material prepared in the second embodiment, wherein a titanium dioxide sample is microspherical, and microspheres are uniformly distributed and have a size of about 2 to 8 μm. It can be clearly seen that more small particles are gathered on the surface of the microsphere, and are lead cesium bromide nanoparticles. The successful compound preparation of the lead cesium bromide and the titanium dioxide is preliminarily proved.

Fig. 2 is a transmission electron microscope image of the cesium lead bromide/titanium dioxide composite photocatalyst material prepared in the third embodiment, in which smaller particles of cesium lead bromide are enriched around a titanium dioxide microsphere, and a high-resolution transmission electron microscope corresponding to the microsphere is shown in the right image, it can be seen that lattice fringes with a spacing of 0.34nm correspond to a cesium lead bromide (111) crystal plane, and lattice fringes with a spacing of 0.23nm and a spacing of 0.19nm correspond to a titanium dioxide (004) crystal plane and a titanium dioxide (200) crystal plane, respectively. Further proves the successful preparation of the lead cesium bromide/titanium dioxide composite material photocatalyst.

Fig. 3 is a graph comparing X-ray diffraction patterns of cesium lead bromide, titanium dioxide, and cesium lead bromide/titanium dioxide composites prepared from comparative example one, comparative example two, and example two, respectively. As shown in the figure, the cesium lead bromide/titanium dioxide composite material contains diffraction peaks of cesium lead bromide and titanium dioxide, wherein the diffraction peaks of 15.2 degrees, 21.6 degrees, 30.7 degrees, 34.3 degrees, 37.6 degrees and 43.7 degrees respectively correspond to the crystal planes of cesium lead bromide (100), (-110), (-200), (-201) and (121), (-202), and the diffraction peaks of 25.3 degrees, 37.8 degrees, 48.0 degrees, 53.9 degrees, 62.7 degrees and 75.0 degrees respectively correspond to the crystal planes of titanium dioxide (101), (004), (200), (105), (204) and (215). This further demonstrates the successful synthesis of the cesium lead bromide/titanium dioxide composite.

FIG. 4 is a graph showing the degradation effect of the cesium lead bromide/titanium dioxide composite material prepared by the present invention in photocatalytic degradation of tetracycline hydrochloride in water. It can be seen that when the dark reaction reaches the adsorption-desorption equilibrium one hour before the lamp is turned on, the adsorption effects of the mono-pure cesium lead bromide nanoparticles and the titanium dioxide microspheres on the tetracycline hydrochloride are relatively small, respectively 4% and 17%, when the amount of the isopropyl titanate in the example is 0.5mL, the adsorption amount of the catalyst on the tetracycline hydrochloride is the largest, and reaches 64%, and the adsorption effect gradually decreases with the increase of the content of the isopropyl titanate as a titanium dioxide precursor in the example. When the amount of the lead cesium bromide in the composite material is fixed, the smaller the amount of the titanium dioxide microspheres, that is, the more lead cesium bromide nanoparticles on the surfaces of the titanium dioxide microspheres, the better the adsorption effect of the catalyst on tetracycline hydrochloride. The photocatalytic degradation process after the lamp is turned on shows that the degradation effect of the composite material on the tetracycline hydrochloride is better than that of lead cesium bromide nano-particles and titanium dioxide microspheres, and when the amount of isopropyl dititanate in the embodiment is 1mL, the highest total degradation rate can reach 94%. The addition of the titanium dioxide microspheres in the lead cesium bromide/titanium dioxide composite material can effectively protect lead cesium bromide nano particles and remarkably improve the photocatalytic performance of the material.

Detailed Description

The present invention will be further described with reference to the following specific embodiments, but the present invention is not limited thereto.