PNNL

Abstract

Scanning tunneling microscopy and density functional theory studies show that oxygen adatoms (Oa), produced during O2 exposure of reduced TiO2(110) surfaces, alter the water dissociation/recombination chemistry through two distinctive pathways. Depending on whether H2O and Oa are on the same or adjacent Ti4+ rows, Oa facilitates H2O dissociation and proton transfer to form a terminal hydroxyl pair, positioned along- or across-Ti row, respectively. The latter process has not been reported previously, and it starts from “pseudo-dissociated” state of water. In both pathways, the subsequent reverse proton transfer results in H2O recombination and statistical oxygen atom scrambling, as manifested by an apparent along- or across-row motion of Oa’s.