Breaking the strong covalent O-H bond of an isolated water (H2O) molecule is the initial reaction step of the molecule splitting. However it is thought to be challenging because of the high bond energy of ∼492 kJ/mol (5.10 eV). Photocatalytic O-H bond breaking on the promising TiO2 photocatalyst can be effectively achieved by transfer of photoexcited holes from the catalyst to H2O molecules. On the widely studied rutile-TiO2(110) surface, photocatalytic dissociation of H2O molecules has been studied extensively. Here, we present recent results on anatase-TiO2(001)-(1×4) surface: Firstly, Hydrogen-bond (H-bond) network promotes water splitting. Weak H-bond is ubiquitous and plays a key role in water chemistry. The formation of a H-bond network is controlled by precisely tuning the coverage of water to above one monolayer. Under ultraviolet (UV) light irradiation, the hydrogen-bond network opens a channel for water splitting with exothermic process. The yielded hydroxyl groups (OHb) provide excess electrons to the TiO2 surface, causing the reduction of Ti4+ to Ti3+ at terrace sites and leading to the emergence of gap states. Secondly, Based on the fact that O-H bond breaking is photo-induced and not the result of spontaneous dissociation, the highly active “ad-molecule” (ADM) model clearly failed to explain our results. We found that fourfold coordinated Ti atoms (Ti4c) at ridge sites of ADM model is highly susceptible to oxidation and propose a mixed oxidation structure of combined ADM and “ad-oxygen” model (AOM) ridges. Surface phase diagram calculations determine rationality of mixed oxidation structures. Our results give systematic photo-induced water splitting on the reconstructed anatase TiO2(001)-(1×4) and provide new insights into the origin of surface reactivity.

Study of photo-activity of H2O on anatase TiO2(001)-(1×4)

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.