Facet Dependence of Photocatalytic Activity in Anatase TiO2: Combined Experimental and DFT Study

For enhancing the photocatalytic performance of anatase TiO2, proper control of the reactive facets and its molecular-level understanding are crucial. This experimental and theoretical study clarifies the facet dependence of the photocatalytic reaction at the anatase TiO2 surface. The 〈112〉-oriented anatase TiO2 layer is deposited on a Ru(0001) substrate at 360 °C by low-pressure chemical vapor deposition. The deposition rate is three times higher than that of the multi-orientation layer on the Pyrex glass. The photocatalytic activity induced by ultraviolet (UV) irradiation around 365 nm in methylene blue aqueous solutions is significantly high, and the rate constant is 6.1 × 10−1 min−1, which is two orders of magnitude greater than that on the multi-orientation TiO2. The density functional theory (DFT) calculations using the constrained DFT method and the hybrid functionals show that the (112) surface stabilizes the adsorbed water molecule most strongly. The photogenerated hole is stably trapped not at the bare surface but at the hydroxylated surface, especially at the hydroxyl group of the hydroxylated (112) and (001) surfaces. The experimental and theoretical findings consistently indicate the high photocatalytic activity at the anatase TiO2(112) surface.