Cl−making overall water splitting possible on TiO2-based photocatalysts

Overall water splitting on a TiO2-based photocatalyst has been extensively investigated. However, in most cases, the products are not in a stoichiometric ratio, thus the reaction is not really overall water splitting. In this work, we found that in the presence of Cl−, the evolution of O2 and H2 over Pt/TiO2 can be successfully achieved, and the activity can be enhanced up to 3 times compared to having no Cl− present. Furthermore, the H2 : O2 ratio can be close to 2.0, i.e. the stoichiometric ratio of overall water splitting. It is proposed that the Cl− ion is involved with the reaction intermediate of O2 evolution from water oxidation. Our work not only reported overall water splitting on a TiO2-based photocatalyst, but also provided experimental evidence for understanding the possible reaction process and the mechanism of photocatalytic water splitting.