Enhanced photocatalytic activity of g-C 3 N 4 –ZnO/HNT composite heterostructure photocatalysts for degradation of tetracycline under visible light irradiation

• Published in: RSC advances 2015-10, Vol.5 (111), p.91177-91189
• Main Authors: Li, Jinze, Zhou, Mingjun, Ye, Zhefei, Wang, Huiqin, Ma, Changchang, Huo, Pengwei, Yan, Yongsheng
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C5RA17360D

A novel graphitic carbon nitride (g-C 3 N 4 )–ZnO/halloysite nanotube (HNT) nanocomposite photocatalyst was synthesized via a facile calcination method in order to enhance the visible-light photocatalytic activity and stability of pure ZnO photocatalysts for degradation of tetracycline. The network-layered structure of g-C 3 N 4 was formed after compositing with previously prepared ZnO/HNTs and the g-C 3 N 4 –ZnO heterojunction has been formed during the coupling process. Furthermore, the HNTs can efficiently extend the surface area of g-C 3 N 4 , which leads to strengthening of the pathways of charge transfer and prolonging the lifetimes of photoexcited carriers. Electrochemical impedance spectroscopy (EIS) and incident-photon-to-current conversion efficiency (IPCE) measurements showed the improvement of the as-obtained g-C 3 N 4 –ZnO/HNT photocatalysts' performance which can be attributed to enhanced charge transfer as a result of more effective separation of photogenerated electron–hole pairs. Such a notable enhancement of photocatalytic performance was mainly ascribed to the improved charge transfer and separation rate of photogenerated electron–hole pairs by the heterostructure of the g-C 3 N 4 –ZnO/HNT catalyst. The mechanism of photodegradation was systematically analysed by active species trapping test and electron spin resonance (ESR) spin-trap technique with dimethyl pyridine N -oxide (DMPO), which conclude that ˙OH and ˙O 2 − radicals are the major reactive species during the photocatalytic reaction for g-C 3 N 4 –ZnO/HNT composite photocatalysts.