Enhancement of hole capture and water dissociation on rutile TiO2(110) by intermolecular hydrogen bonding: time-domain ab initio study

Photocatalytic water splitting has been a focal point of research to solve energy and environmental issues. However, the understanding of photocatalytic water splitting and coupled dynamics of photogenerated charge carriers at molecule/semiconductor interfaces is still limited. We have combined ab initio molecular dynamics, real-time time-dependent density functional theory, and nonadiabatic molecular dynamics to study the dissociation of water and capture of photogenerated holes on the pristine rutile TiO2(110) surface. Our simulations indicate that intermolecular hydrogen bonding (IHB) between water molecules facilitates water dissociation. The dissociation energy of water molecules in a pristine, non-dissociated structure is reduced by 15%, from 0.26 eV to 0.21 eV, due to IHB. In the semi-dissociated structure, the dissociation energy of a water molecule is only 0.13 eV, owing to proton transfer induced by IHB. In the semi-dissociated structure, IHB between H2O and terminal hydroxyl (OtH) stabilizes the dissociated structure. Furthermore, IHB promotes spatial isolation of OtH and bridging hydroxyl (ObrH) and inhibits their recombination. The stabilized dissociated structure activates high-frequency vibrational modes that increase the nonadiabatic coupling and promote hole capture on a femtosecond timescale, accelerating the capture rate by 36%. The findings provide important insights into photo-dissociation of water on rutile TiO2(110), particularly shedding light on the impact of key intermediates on the photocatalytic process.