Controlled Activation of Reactive Oxygen Species by Atomic Force Microscopy: Synthesis of Superoxo and Ozone Molecules on Rutile TiO ₂ (110) Surface

Abstract Electron‐hole activation, transforming closed‐ to open‐shell reactive oxygen species on photocatalytic TiO 2 surfaces, is essential for designing effective photocatalysts capable of providing specific functionalities and enhanced performance. However, at atomic level, the activation mechanism of the oxygen species remains murky. To shed light, we used a combination of atomic force microscopy, Kelvin probe force spectroscopy under ultrahigh vacuum conditions with density functional theory simulations to understand the atomic‐scale mechanism of electron and hole injection into the chemisorbed oxygen species supported on the rutile TiO 2 (110) surface. Specifically, the closed‐shell oxygen species, such as the peroxo () molecule​, can be manipulated by applied local electric field to induce its hopping between different adsorption sites or molecular rotation, while the open‐shell oxygen species, such as the superoxo () molecule, can be synthesized by injecting holes into their corresponding closed‐shell form. Combining applied local electric field with hole injection we have been able to activate a tip‐induced Langmuir–Hinshelwood reaction leading to ozone (O 3 ) molecule formation and, for the first time, visualize its synthesis at atomic resolution. The formation of long‐lived superoxo and ozone molecules directly demonstrates their strong oxidative properties, which persist on the timescale of seconds highlighting their prominent role in photocatalysis.