Self-Diffusion of Individual Adsorbed Water Molecules at Rutile (110) and Anatase (101) TiO2 Interfaces from Molecular Dynamics

The distribution of individual water molecules' self-diffusivities in adsorbed layers at TiO2 surfaces anatase (101) and rutile (110) have been determined at 300 K for inner and outer adsorbed layers, via classical molecular-dynamics methods. The layered-water structure has been identified and classified in layers making use of local order parameters, which proved to be an equally valid method of self-ordering molecules in layers. Significant distinctness was observed between anatase and rutile in disturbing these molecular distributions, more specifically in the adsorbed outer layer. Anatase (101) presented significantly higher values of self-diffusivity, presumably due to its corrugated structure that allows more hydrogen bonding interaction with adsorbed molecules beyond the first hydration layer. On the contrary, rutile (110) has adsorbed water molecules more securely trapped in the region between Ob atoms, resulting in less mobile adsorbed layers.

Automated summary

The distribution of water molecules' self-diffusivities in adsorbed layers at TiO2 surfaces with anatase (101) and rutile (110) crystal structures has been determined using classical molecular-dynamics methods. The layered-water structure was identified and classified into layers using local order parameters, which was found to be a valid method for organizing molecules in layers. The results showed significant differences in the molecular distributions between anatase and rutile, particularly in the adsorbed outer layer. Anatase (101) had significantly higher self-diffusivity values, possibly due to its corrugated structure allowing for more hydrogen bonding interactions with adsorbed molecules beyond the first hydration layer. In contrast, rutile (110) trapped the adsorbed water molecules more securely between Ob atoms, resulting in less mobile adsorbed layers.