First-principles study on the adsorption and dissociation of H2O on the ThO2 (111) surface

This study utilizes the DFT + U computational method to explore the adsorption and dissociation behaviors of water molecules on the ThO 2 (111) surface. The results indicate that, for the adsorption of a single water molecule, dissociated water (−0.68 eV) exhibits a stronger adsorption tendency on the substrate compared to molecular water (−0.62 eV), with a dissociation energy barrier of 0.05 eV. As water coverage increases, the optimal adsorption configuration is identified as the 1:1 ratio of molecular to dissociated water, with an average adsorption energy higher than that of a single water molecule (−0.62 eV). This enhancement is attributed to the contribution of the hydrogen-bond network. Moreover, in the dissociation process of multiple water molecules, it is observed that disrupting the hydrogen-bond network of the optimal adsorption configuration requires a higher energy barrier. Specifically, the dissociation energy barrier for the reaction 4OH + 2H 2 O → 6OH + H 2 O is greater than the adsorption energy of a single water molecule, further indicating that the hydrogen-bond network enhances the stability of surface adsorption. Additionally, AIMD simulations at 1 ML coverage verify the thermal stability of the system at different temperatures. At high coverage regimes, water molecules exhibit adsorption and dissociation behavior on the ThO₂(111) surface.