The effect of DMPO on the formation of hydroxyl radicals on the rutile TiO2(110) surface

Unraveling the formation mechanism of hydroxyl radicals (OH& x2d9;) is one of the outstanding issues in photocatalytic reactions, where 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) is widely utilized as a trapping agent to detect OH& x2d9; radicals in experiments. In this study, we carry out density functional theory calculations to reveal the origin and formation process of OH& x2d9; radicals by investigating the interaction of water with DMPO on a rutile TiO2(110) surface. Our results clearly show that the OH& x2d9; radicals trapped by DMPO stem from water upon illumination. The charge compensation mechanism dominates the formation of DMPO-OH from the reaction between DMPO and water on the rutile TiO2(110) surface. These findings provide new insights into the photocatalytic mechanism and may achieve new frontiers in photocatalytic research.