Directional deep oxidation of toluene via phenolized pathway—A review concerning dominant factors involved in photocatalysis

Abstract

Photocatalytic oxidation through semiconductor photocatalysis is an efficient and green technology for pollutant removal, which has been widely applied to degrade volatile organic chemicals under ambient conditions. However, most of reports focus on the reduction of VOCs concentration while ignore the generation of toxic intermediates, as well as the corresponding secondary pollution. Therefore, it is necessary to further explore how to timely achieve efficient and deep oxidation of VOCs. In this review, we undertake a detailed analysis of photocatalytic degradation of toluene, a representative compound of aromatic hydrocarbon VOCs, and identify the most capable phenolized pathway governed by hydroxyl radicals (•OH). With this pathway, no toxic intermediate like benzene is produced during the photocatalysis. The driving factor, oxygen vacancy (OV), for fueling the generation of •OH is highlighted and the specific approaches including doping engineering and co-catalyst loading that can create rich OVs in semiconductor photocatalysts are described. Furthermore, the challenges and opportunities faced by the phenolized pathway in the future development are prospected.

Graphical abstract

Keywords

Toluene degradation / Oxygen vacancy / Photocatalysis / Phenolized pathway

Highlight

	● Phenolized pathway of toluene degradation was summarized for the first time.
	● The role of oxygen vacancies realizing phenolized pathway was elucidated.
	● Strategies for creating oxygen vacancies were summarized.

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