Surface hydroxyl manipulation of BiOCl nanosheets for promoted O2 activation and photocatalytic NO removal

Surface hydroxyl on semiconductors strongly affects their photocatalytic performance by changing the generation of reactive oxygen species (ROSs). However, the intrinsic relationships are still unknown, especially on the aspect of surface atomic configurations of photocatalysts. In this study, we demonstrate that surface hydroxyl manipulation of BiOCl nanosheets can control the surface steric hindrance and the formation energy of oxygen vacancies ( V _O ). Hydroxyl-poor BiOCl ultrathin nanosheets of lower steric hindrance, in contrast to their hydroxyl-rich counterparts, possess the weakened surface Bi–O bond to promote the V _O formation, and also switch the ROSs from superoxide radicals (‧O _2 ^‒ ) to peroxyl anion (O _2 ^2− ) during the photocatalytic O _2 activation. The O _2 ^2− facilitates the complete oxidation of NO into bidentate nitrate and effectively prevents the formation of more hazardous NO _2 and the back reduction of generated nitrate to NO. This study deepens our understanding of surface structure-activity of photocatalysts for selective generation of ROSs and sustainable development.