Bonding and Electron Energy-Level Alignment at Metal/TiO2 Interfaces: A Density Functional Theory Study

Metal/TiO2 interfaces have been extensively studied because of their importance in electronic devices, electrochemical cells, and photocatalysis. In this article, we present our studies on electronic structures for anatase TiO2(001)/fcc-metal(001) (metal = Pt, Pd, or Au) interfaces using first-principles calculations. It is demonstrated that the Schottky barrier height depends on the metal work function and significantly decreases at an interface with strong adhesion between the metal and TiO2. The sizable reduction of the barrier height is a consequence of dipole formation at the interface due to electron transfer from TiO2 to the metal. The formation of dipoles at the Pt/TiO2 interface is supported by our experimental results for a core-level binding-energy shift in Pt clusters loaded on the surface of TiO2. Differences in the bonding and antibonding characters of metal–O bonds for the three metals are discussed based on the projected densities of states given by our density-functional theory calculations.