Mechanocatalysis of CO to CO₂ on TiO₂ surface controlled at atomic scale

The common ways to activate a chemical reaction are by heat, electric current, or light. However, mechanochemistry, where the chemical reaction is activated by applied mechanical force, is less common and only poorly understood at the atomic scale. Here we report a tip-induced activation of chemical reaction of carbon monoxide to dioxide on oxidized rutile TiO₂ (110) surface. The activation is studied by atomic force microscopy, Kelvin probe force microscopy under ultrahigh-vacuum and liquid nitrogen temperature conditions, and density functional theory (DFT) modeling. The reaction is inferred from hysteretic behavior of frequency shift signal further supported by vector force mapping of vertical and lateral forces needed to trigger the chemical reaction with torque motion of carbon monoxide towards an oxygen adatom. The reaction is found to proceed stochastically at very small tip-sample distances. Furthermore, the local contact potential difference reveals the atomic-scale charge redistribution in the reactants required to unlock the reaction. Our results open up new insights into the mechanochemistry on metal oxide surfaces at the atomic scale.