Facet-Dependent Interfacial Charge Transfer in Fe(III)-Grafted TiO<sub>2</sub> Nanostructures Activated by Visible Light

Interface engineering in heterogeneous catalysis is fascinating because of the modulation of charge-transfer processes and catalytic activity. Herein, by constructing Fe­(III)–TiO<sub>2</sub> systems with different interfacial contact facets, {101} and {001} facets, we demonstrate the facet-dependent interfacial charge transfer properties of TiO<sub>2</sub>/Fe­(III) system activated by visible light. Although the photoreactivity of the {001} facet is documented to be higher than that of the {101} facet under UV light, phenol photodegradation experiments reveal that under visible light {101} TiO<sub>2</sub>/Fe­(III) exhibits significantly higher photocatalytic activity than {001} TiO<sub>2</sub>/Fe­(III). Photoelectrochemical measurements and computational calculations suggest that the {101} TiO<sub>2</sub>/Fe­(III) interface significantly promotes interfacial electron transfer compared with the {001} TiO<sub>2</sub>/Fe­(III) interface owing to the facet-specific electron–hole transport properties of the {101} and {001} facets in the TiO<sub>2</sub> crystals. The reduced Fe­(III) nanoclusters on the {101} TiO<sub>2</sub> surface facilitate the reduction of adsorbed O<sub>2</sub> molecules to H<sub>2</sub>O<sub>2</sub> via multielectron transfer processes and simultaneously promote hole generation in VB­(TiO<sub>2</sub>) to oxidize organic contaminants. These findings demonstrate the crucial roles of the facet in determining interfacial charge transfer processes and will be applicable for designing high-performance catalysts.