Hot-electron capture at the TiO2/O2 interface: The role of functional dependence and interfacial dynamics

The trapping of hot electrons by molecular oxygen at TiO2 surfaces plays a central role in photocatalytic charge separation and interfacial redox chemistry. Using ab initio nonadiabatic molecular dynamics simulations, electron capture by the O2 molecule at the rutile TiO2(110)/O2 interface was investigated. A pronounced dependence on the exchange-correlation functional was identified: in DFT+U, the O2 LUMO lies below the conduction band minimum (CBM), leading to nearly complete electron trapping, whereas in the HSE, the LUMO is shifted above the CBM, resulting in much weaker capture. Importantly, electron trapping was found to be intimately coupled to the molecular dynamics of O2 at the surface, with both the distance and orientation of the adsorbate strongly modulating the probability of electron transfer dynamically. Comparisons with experiments indicate lower trapping efficiencies in theory, and possible origins of this discrepancy are discussed. These findings establish a microscopic framework in which interfacial level alignment and molecular dynamics jointly determine electron capture at semiconductor-molecule interfaces.