Understanding Competitive Photo-Induced Molecular OxygenDissociation and Desorption Dynamics atop a Reduced RutileTiO2(110) Surface: A Time-Domain Ab Initio Study

Photochemical O2activation is the key to many photo-oxidationchemical reactions where the efficiency and chemical processes are significantlyaffected by the substrate-adsorbate interactions. However, the underlyingmechanisms of the reactions are still unclear. Focusing on the reduced rutileTiO2(110) surface with an adsorbed O2, we perform time-domain densityfunctional theory and nonadiabatic molecular dynamics simulations to investigatephoto-induced O2dissociation and desorption processes. The simulationsdemonstrate that O2exhibits three distinct adsorption positions atop a reducedTiO2(110) surface where it prefers to adsorb at a bridge oxygen vacancy (OV)site, followed by two metastablefivefold-coordinated Ti (Ti5c) sites, leading to theformation of peroxide O22-by accepting two excess electrons of Ti3+ions inducedby the OV. The adsorbed O2at an OVsite creates no midgap states for capturingphoto-excited holes and favors facile O2dissociation instead of desorption due toa small dissociation energy barrier, leaving the charge carrier lifetime up to overhalf a nanosecond. In contrast, midgap states composed of O2 pi*antibonding orbitals present in the two Ti5cadsorptionconfigurations are able to rapidly trap photoexcitation holes in the range of several to tens of picoseconds, which cause theelongation of the interfacial O-Ti bond length and drive O2desorption. The two Ti5cadsorption configurations are switchablebetween each other and occur at Ti5csites due to the minute energy barriers, consolidating the experimental results. A good choiceof a transition metal can enhance p-d polarization to manipulate the positions of O2antibonding orbitals and control O2chemicalreactions. The reported results provide a fundamental understanding of the influence of the interplay between photoexcitation holesand the adsorbate-substrate interaction on O2dissociation and desorption. The study shows how electronic and charge propertiescan be controlled by dopants, allowing one to design high-performance transition metal oxide catalysts.

Automated summary

This study investigates the photo-induced dissociation and desorption processes of O2 on the reduced rutile TiO2(110) surface using time-domain density functional theory and nonadiabatic molecular dynamics simulations. The results show that O2 exhibits three distinct adsorption positions on the surface, with O2 adsorbed at a bridge oxygen vacancy site being the most favorable for dissociation. The other two adsorption positions result in O2 desorption. By selecting appropriate transition metals, the positions of O2 antibonding orbitals can be manipulated to control O2 chemical reactions, allowing for the design of high-performance transition metal oxide catalysts.