Roles of (001) and (101) Facets of Anatase TiO<sub>2</sub> in Photocatalytic Reactions

Abstract

Single crystals of anatase TiO2 with exposed (001) and (101) facets were synthesized by a hydrothermal method. We carried out photocatalytic reduction reactions to deposit noble metals (Au, Ag, and Pt) and photocatalytic oxidation reactions to deposit metal oxides (PbO2 and MnOx) on the surface of TiO2. The deposited anatase TiO2 samples were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) to study the roles of the two facets of anatase TiO2 in photocatalytic reactions. The noble metals were selectively deposited on the exposed (101) facet, while metal oxides were selectively deposited on the exposed (001) facet. This result indicated that photogenerated electrons and holes mainly accumulated on the (101) and (001) facets, and then took part in photocatalytic reduction and oxidation reactions, respectively. These results also suggested that the simultaneous exposure of the two facets could facilitate charge separation. Therefore, it was proposed that the simultaneous exposure of two facets with different functions will be a new strategy to effectively promote photocatalytic reaction.