Effect of DMPO on the Formation of Hydroxyl Radicals on the Rutile TiO2(110) Surface

Unraveling the formation mechanism of hydroxyl radical (OH•) is one of the outstanding issues in photocatalytic reactions, where 5,5-dimethyl-1-pyrroline N-oxide (DMPO) is widely utilized as a trapping agent to detect OH• radicals in experiments. In this work, we carry out density functional theory calculations to reveal the origin and formation process of OH• radicals by investigating the interaction of water with DMPO on the rutile TiO2(110) surface. Our results clearly show that the OH• 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 inspire new frontiers in photocatalytic research.