ATR-FTIR measurements and quantum chemical calculations concerning the adsorption and photoreaction of oxalic acid on TiO2

The adsorption and photoreaction of oxalic acid on the surface of anatase and rutile TiO2 nanoparticles have been studied using a combined experimental and theoretical approach. In the dark, the experimental adsorption reaches an equilibrium state that can be described as a mixture of adsorbed water and oxalic acid molecules, with the latter forming two different surface complexes on anatase and one on rutile particles. When the system is subsequently illuminated with UV(A) light, the surface becomes enriched with absorbed oxalic acid, which replaces photo-desorbed water molecules, and one of the adsorbed oxalic acid structures on anatase is favoured over the other.