Ultrafast Charge Transfer Coupled to Quantum Proton Motion at Molecule/Metal Oxide Interface

Abstract

Understanding the ultrafast dynamics of photoexcited carriers at the semiconductor/molecule interface is essential for improving the solar energy conversion efficiency. At such interfaces, the hydrogen bond (H-bond) network is often formed, and the quantum proton motion is expected. However, how the nuclear quantum effects (NQEs) will influence the photoexcited charge transfer is still unknown. By combining two kinds of emerging molecular dynamics methods at the ab initio level - the path-integral based molecular dynamics and time-dependent nonadiabatic molecular dynamics, and choosing CH3OH/TiO as a prototypical system to study, we find that the quantum proton motion in the H-bond network is strongly coupled with the ultrafast photoexcited charge dynamics at the interface. The hole trapping ability of adsorbed CH3OH molecule is then notably enhanced by the NQEs, and thus, it behaves as a hole scavenger on TiO2. It is concluded that the quantum proton motion in the H-bond network may play a critical role in enhancing the energy conversion efficiency based on photoexcitation.