Revealing the photocatalytic dissociation of water molecules on rutile TiO2 surface via hybrid functional based linear response time-dependent density functional theory

Abstract

Rutile TiO₂ shows great potential for photocatalytic water (H₂O) splitting into oxygen (O₂) and hydrogen peroxide (H₂O₂). However, the mechanism of surface water oxidation on rutile TiO₂ remains unclear, involving complex ground-state thermal catalysis and excited-state photocatalysis processes. Here, by using linear response time-dependent density functional theory (LR-TDDFT), we investigate H₂O oxidation at both the ground-state and excited-state levels. Our results show that O₂ formation is thermocatalytic and occurs at room temperature, while H₂O₂ desorption is driven by photogenerated holes, requiring light to overcome a high-energy barrier, which agrees with experiments showing O₂ formation is more favorable. Furthermore, comparing the computational results obtained using the local PBE and nonlocal HSE functionals, we find the HSE provides a more accurate description of the electronic interactions between TiO₂ and the adsorbates, and the reaction pathways, especially under excited-state conditions. Our work provides a pathway for understanding TiO₂ water oxidation mechanisms.