Insight into reactive species-dependent photocatalytic toluene mineralization and deactivation pathways via modifying hydroxyl groups and oxygen vacancies on BiOCl

Hydroxyl radicals always play important role in the photocatalytic degradation of pollutants and thus lots of efforts have been made to enlarge their amount. Herein, BiOCl photocatalysts with different surface hydroxyl groups amount are synthesized using ionic liquid self-combustion (C-BiOCl) and hydrothermal method (H-BiOCl) to deep understand the roles of hydroxyl radicals in toluene mineralization. It is found that hydroxyl radicals in H-BiOCl have reverse inhibitory effect on the ring-opening reaction in the photocatalytic mineralization process of toluene and C-BiOCl exhibits more excellent ability and stability in mineralizing toluene. The reason is that C-BiOCl lacking hydroxyl groups can selectively generate benzoic acid by holes and superoxide anion radicals; while H-BiOCl with large number of hydroxyl groups will lead to the production of hydroxyl radicals and phenolic intermediates, which will preferentially cover active sites such as oxygen vacancies, thereby reducing the performance and stability of the catalyst.