Improving photocatalytic H₂ evolution of TiO₂ via formation of {001}-{010} quasi-heterojunctions

The coexistence of low-index facets with a highly photoactive {001} facet in anatase TiO₂ nanocrystals has been recently found beneficial to enhance the photocatalytic performance of TiO₂ via a synergistic effect. In this paper, this synergistic effect has been further extended from a single crystal to interconnected nanocrystals with dominating {001} or {010} facet in intact hierarchical TiO₂ nanostrucutre. The particles synthesized at the optimal condition showed outstanding photocatalytic hydrogen production of 364.2 μmol·g^-1·h^-1, which is about four times as much as that of commercial P25 (96.5 μmol· g^-1·h^-1). Femtosecond transient spectroscopy and density functional theory (DFT) study indicates that effective electron-hole separation takes place within these nanostructures. This new prototype of synergy, which we denote as quasi-heterojunctions, shows that enhanced photocatalytic performance could be derived in the same anatase phase by synthesizing appropriate faceted nanostructures. This work provides a new dimension to facet engineering of TiO₂ and other semiconductor photocatalysts.