Deciphering the Role of Hydrogen Bonding and Water Dynamics in Hole Transfer on Anatase TiO₂(101): An ab Initio Quantum Dynamics Study

Using time-dependent density functional theory (TD-DFT) and nonadiabatic molecular dynamics (NAMD) simulations, we elucidate how hydrogen bonding and water dynamics regulate hole transfer at the anatase TiO₂(101)/water interface. Compared to low-density water (LW), moderate-density water (MW) enhances hydrogen bonding between surface- and nonsurface-adsorbed water, restricting interfacial water mobility. This suppresses nonadiabatic coupling and slows the hole transfer. Conversely, higher-density water (HW) near the vacuum destabilizes hydrogen bonding networks, freeing interfacial water and amplifying thermal motion. Enhanced disorder strengthens nonadiabatic coupling, accelerating the hole transfer. Temperature-dependent simulations show that thermal energy overcomes hydrogen bonding constraints: elevated temperatures intensify water dynamics and nonadiabatic coupling, accelerating hole transfer. These results establish hydrogen bonding and thermal fluctuations as key regulators of charge dynamics at the semiconductor/liquid interfaces.