Water dehydrogenation reaction at the anatase TiO₂–water interface under photocatalytic operating conditions

We investigate the water dehydrogenation process at the anatase TiO₂(101)–water interface in the presence of an electron hole. We obtain the free-energy landscape by combining machine learning potentials at the hybrid functional level of accuracy and on-the-fly probability-enhanced sampling [1]. Our scheme reveals that dehydrogenation occurs through indirect proton transfer to a twofold coordinated surface O atom. Our results give a free-energy barrier of 0.25±0.05 eV and a reaction free-energy of 0.10±0.04 eV. The direct mechanism is found to have a higher reaction barrier of 0.45±0.06 eV. In this way, this methodology allows us to distinguish in an unbiased fashion competing mechanisms at play under photocatalytic operating conditions.

[1] Y.-B. Zhuang, A. Pasquarello, Angew. Chem. Int. Ed., 2025, e202507071.