Nonadiabatic Dynamics of Polaron Hopping and Coupling with Water on Reduced TiO2

By interplay between first-principles molecular dynamics and nonadiabatic molecular dynamics simulations based on the decoherence-induced surface-hopping approach, we investigate and quantify the mechanisms through which different electron polaron hopping regimes in the reduced anatase TiO2(101) surface influence recombination of photogenerated charge carriers, also in the presence of adsorbed water (H2O) molecules. The simulations reveal that fast hopping regimes promote ultrafast recombination of photogenerated charge-carriers. Conversely, charge recombination is delayed in the presence of slower polaron hopping and even more so if the polaron is pinned at one Ti-site, as typical following adsorption of H2O on the anatase(101) surface. These trends are related to the observed enhancement of the space and energy overlap between conduction band minimum and polaron band gap states, and the ensuing nonadiabatic couplings (NAC) strengths, during a polaronic hop. We expect these insights on the beneficial role of polaron diffusion pinning for the extended lifetime of photoexcitations in TiO2 to sustain ongoing developments of photocatalytic strategies based on this substrate.

Automated summary

By simulating the interplay between different electron polaron hopping regimes, this study investigates the influence of these regimes on the recombination of photogenerated charge carriers in TiO2(101) surface and reveals that fast hopping promotes ultrafast recombination while slower hopping and polaron pinning delay the recombination process. These findings provide insights into the development of photocatalytic strategies based on TiO2.