The effects of HF treatment on the activity of TiO2 thin films for the photocatalytic watersplitting reaction have been investigated. TiO2 thin films treated with HF solution (HF-TiO2) werefound to exhibit a remarkable enhancement of the photocatalytic activity for H2 evolution from amethanol aqueous solution, as well as efficient photoelectrochemical performance under UV lightirradiation as compared with the untreated TiO2. Moreover, Pt-loaded HF-TiO2 thin films were foundto act as efficient and stable photocatalysts for the decomposition of water under UV light irradiation.The mechanistic insights obtained in the present study will be useful in the design of highly efficientphotocatalysts for the decomposition of water.