Direct evidence for hydrated protons as the active species in artificial photocatalytic water reduction into hydrogen

Abstract

Photocatalytic water reduction to hydrogen over oxide semiconductors is one of the most extensively investigated artificial photocatalytic reactions, but the nature of the active species has not yet been elucidated. Here, we successfully prepared Pt/rutile TiO2(110) surfaces with hydrated proton species via co-adsorption of hydrogen and water and observed the photocatalytic reduction of hydrated protons to H2 upon UV light illumination. These results provide experimental evidence to prove hydrated protons as the active species for photocatalytic water reduction to hydrogen and demonstrate the occurrence of photocatalytic reduction of hydrated protons to H2 within the H-bonding network on the catalyst surface instead of directly on the catalyst surface. The Pt-TiO2 interface is capable of dissociating water to form hydroxyl groups that facilitate the formation of H-bonding network on the catalyst surface to enhance the photocatalytic H2 production. Our results greatly advance fundamental understanding of artificial photocatalytic water reduction.