Diffusion and reaction pathways of water near fully hydrated TiO2 surfaces from ab initio molecular dynamics

Lorenzo Agosta; Erik G Brandt; Alexander P Lyubartsev

doi:10.1063/1.4991381

Diffusion and reaction pathways of water near fully hydrated TiO₂ surfaces from ab initio molecular dynamics

J Chem Phys. 2017 Jul 14;147(2):024704. doi: 10.1063/1.4991381.

Authors

Lorenzo Agosta¹, Erik G Brandt¹, Alexander P Lyubartsev¹

Affiliation

¹ Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.

PMID: 28711052
DOI: 10.1063/1.4991381

Abstract

Ab initio molecular dynamics simulations are reported for water-embedded TiO₂ surfaces to determine the diffusive and reactive behavior at full hydration. A three-domain model is developed for six surfaces [rutile (110), (100), and (001), and anatase (101), (100), and (001)] which describes waters as "hard" (irreversibly bound to the surface), "soft" (with reduced mobility but orientation freedom near the surface), or "bulk." The model explains previous experimental data and provides a detailed picture of water diffusion near TiO₂ surfaces. Water reactivity is analyzed with a graph-theoretic approach that reveals a number of reaction pathways on TiO₂ which occur at full hydration, in addition to direct water splitting. Hydronium (H₃O⁺) is identified to be a key intermediate state, which facilitates water dissociation by proton hopping between intact and dissociated waters near the surfaces. These discoveries significantly improve the understanding of nanoscale water dynamics and reactivity at TiO₂ interfaces under ambient conditions.