Density functional theory study of α-cyanoacrylic acid adsorbed on rutile TiO2(1 1 0) surface

Abstract

The investigation of adsorption properties of anchor group on photo-anode is foundation in the optimization of dye sensitizers (DS) for solar cells. α-cyanoacrylic acid (CAA) is the typical anchor moiety coupled electronic acceptor in DS. To understand the interaction between rutile TiO2 photo-anode and DS based upon CAA in dye sensitized solar cells, the atomic configurations, energies and electronic properties of CAA adsorbed on rutile TiO2(110) surface were studied by using density functional theory calculations. The results indicate CAA prefers to dissociatively adsorb on rutile TiO2(110) surface as bidentate configuration in which the O atoms of CAA bind with two adjacent surface five-coordinate Ti atoms along [001] direction, and the H atom in hydroxyl of CAA adhere to the nearest neighbor surface O atom at bridge site, generating a hydroxyl species. The corresponding adsorption energy is 1.480eV. The analysis of geometrical parameters, density of states and electron density suggests the bonds between rutile TiO2(110) surface and CAA are formed. The density of states and orbital character at the gamma-point in reciprocal space support that the adsorption of CAA on the surface provides feasible mode for photo-induced electron injection.