Temperature dependent photocatalysis of g-C3N4, TiO2 and ZnO: Differences in photoactive mechanism

Fanpeng Meng; Yazi Liu; Jun Wang; Xiaoyao Tan; Hongqi Sun; Shaomin Liu; Shaobin Wang

doi:10.1016/j.jcis.2018.07.131

Temperature dependent photocatalysis of g-C₃N₄, TiO₂ and ZnO: Differences in photoactive mechanism

J Colloid Interface Sci. 2018 Dec 15:532:321-330. doi: 10.1016/j.jcis.2018.07.131. Epub 2018 Jul 31.

Authors

Fanpeng Meng¹, Yazi Liu², Jun Wang¹, Xiaoyao Tan³, Hongqi Sun⁴, Shaomin Liu², Shaobin Wang⁵

Affiliations

¹ State Key Laboratory of Separation Membranes and Membrane Processes/National Center for International Joint Research on Separation Membranes, Department of Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China.
² Department of Chemical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia.
³ State Key Laboratory of Separation Membranes and Membrane Processes/National Center for International Joint Research on Separation Membranes, Department of Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China. Electronic address: tanxiaoyao@tjpu.edu.cn.
⁴ School of Engineering, Edith Cowan University, Joondalup, WA 6027, Australia.
⁵ Department of Chemical Engineering, Curtin University, GPO Box U1987, Perth, WA 6845, Australia. Electronic address: shaobin.wang@curtin.edu.au.

PMID: 30096526
DOI: 10.1016/j.jcis.2018.07.131

Abstract

Photocatalysis has been believed as one of the green and sustainable avenues to address energy and environmental crises by converting solar energy to chemical energy via reactions. Temperature is usually a vital factor controlling kinetics and thermodynamics of a reaction, but it has been less investigated in photocatalysis. In this work, the effect of reaction temperature on photocatalysis was investigated in a simple process, photocatalytic degradation of Congo Red (CR) on three typical catalysts, g-C₃N₄, TiO₂ and ZnO, to differentiate the interfacial radical generation and reaction mechanism. The results showed that the temperature has a positive effect on the photocatalytic activity of the three catalysts. The scavenger experiments at various temperatures indicated that the generation of reactive species from the three photocatalysts is different and that the free radicals can be produced more quickly at higher temperatures, causing improved activities in photocatalysis. However, photocurrent analysis and EIS at various temperatures showed that the temperature had a different effect on recombination rate and transfer barriers of the charge carriers from each catalyst. Therefore, the dramatic enhancement in photodegradation activities probably originated from a novel mechanism of the photothermocatalytic oxidation. The interfacial reaction and mechanism from the influence of reaction temperature on the photocatalytic process was proposed.

Keywords: Free radical; Interfacial reaction and mechanism; Photocatalysis; Reaction temperature.