XIE Peng, HUANG Wei, QIN Junhao, SUN Jiajie, WEI Zhishun

(College of Materials and Chemical Engineering, Hubei University of Technology, Wuhan 430068, Hubei, China)

Extended abstract:[Background and purposes] With the continuous development of industry, environmental problems are becoming increasingly serious. As a new means of green and clean strategy, photocatalysis has been widely explored. Bismuth oxychloride (BiOCl) has attracted much attention in many fields due to its unique layered structure, adjustable band gap (~3.4 eV) and excellent photochemical stability. However, the BiOCl materials synthesized by using the traditional methods have problems, such as limited specific surface area, high recombination rate of electrons and holes and insufficient surface active sites. In order to solve these problems, BiOCl powders with different morphologies were prepared by using ethanol and water, with their structure and photocatalytic performance to be analyzed to explore the influence of solvents on performance of the BiOCl photocatalysts.[Method] Three BiOCl photocatalytic samples were prepared by using water, alcohol and alcohol-water as solvents. Specifically, 0.2 mmol Bi(NO₃)₃·5H₂O was weighed and dissolved into a mixed solution with a total volume of 60 mL (ethylene glycol∶water=x∶60−x; x=0, 30, 60), followed by ultrasonic dispersion for 30 min. 0.2 mmol KCl was added to the above solution, with vigorous stirring with magnetic stirring for 1 h to trigger full reaction. Finally, the solution was transferred to a stainless steel high-pressure reactor and reacted at 160 ℃ for 12 h. After the reaction was finished, the product was washed twice with anhydrous ethanol and deionized water, and then dried with a freeze dryer. Morphology and structural characteristics of BiOCl synthesized at different solvent conditions were analyzed by using SEM, XPS and XRD. Photocatalytic performance of BiOCl was studied through the degradation of acetic acid and CIP in two different systems, while the difference in photocatalytic performance and internal mechanism of the BiOCl were also discussed[Results] The samples synthesized with three different solvents had very different morphologies. When water was used as the solvent, BiOCl tended to grow into a flake structure. When alcohol-water was used as solvent, its size decreased and became nanosheet. When glycol was used as a solvent, it self-assembled into flower spheres. XRD results suggested that BiOCl has a higher (001) and the same crystal face direction, when water is used as the solvent. According to XPS results, the oxygen vacancy (OVs) ratio was higher, when alcohol and water acted together. With the photocatalytic degradation performances, it was found that the BiOCl prepared in alcohol-water had the highest degradation rate for acetic acid, with degradation rate of 6.425 min⁻¹. In the ciprofloxacin (CIP) degradation system, the flower-like BiOCl prepared in ethylene glycol had the highest photodegradation efficiency, while the degradation efficiency was 87.2% and the degradation rate was about 0.02954 min⁻¹.[Conclusions] In this paper, morphology and structure of BiOCl photocatalytic materials were adjusted by using ethanol and water as a double solvent system. The prepared BiOCl samples were characterized by using SEM, XRD and XPS. The addition of ethylene glycol played a linking effect on the BiOCl photocatalyst and inhibited the growth of (001) and crystal faces in the same direction of BiOCl crystals. The addition of ethylene glycol can promote the formation of OVs, with proportion to be highest when ethylene glycol and water were used together. Through the degradation of acetic acid and ciprofloxacin (CIP) in two different systems, it was found that BiOCl containing oxygen vacancy had higher photodegradation activity in the acetic acid degradation system, while BiOCl with unique three-dimensional flower structure had higher degradation activity in the CIP degradation system.

Key words: dual solvent; BiOCl; synergistic effect; photocatalysis