Photocatalytic degradation of oxalic acid adsorbed on the Ag/P25 TiO2 composite nanoparticle films were investigated using ATR-FTIR technique under UV irradiation. Ag/P25 TiO2 composite nanoparticle films with various Ag content were tested. Topography and chemical structure/composition of the composite nanoparticle films were analyzed by AFM and XPS respectively. It was found that in the degradation reaction of the oxalic acid, the presence of only 2% Ag nanoparticles leads to six times more oxalic acid degradation compared to that degraded in the presence of pure P25 TiO2 nanoparticles. The degradation rate of the oxalic acid is three times higher in the case of Ag/TiO2 composite nanoparticle film than in the case of pure TiO2 nanoparticles. It was observed that both the rate of oxalic acid degradation and the degraded amount of the oxalic acid were significantly affected by Ag incorporation. (C) 2014 Elsevier B.V. All rights reserved.