Differences in the gas-phase photocatalytic degradation of NH3 and ethanol in the presence of water over two commercial TiO2 materials with different structural characteristics (Evonik's P25 (P25) and Sigma Aldrich's anatase (SA)) were established here using FTIR. The materials were characterized using different techniques including BET, XRD, UV-vis DRS and XPS. The interaction of CO probe molecule with the oxides was evaluated via calorimetry and by in-situ DRIFTS coupled to on-line mass spectrometry. This allowed us to determine differences in the surface properties of the two TiO2 materials. NOx- surface species became evident during the photodegradation of adsorbed NH3 over both SA and P25. However, while surface bidentate nitrate species remained strongly bound to P25, the surface species were fully eliminated from SA. Differences in the photocatalytic degradation of ethanol over P25 and SA were also determined. Ethanol adsorption and its evolution were largely independent of the presence of oxygen for SA, but oxygen affected these processes for P25. (C) 2015 Elsevier B.V. All rights reserved.