In this paper, Pt/TiO2 and Pt-Ga/TiO2 catalysts with similar Pt dispersion and similar structural and morphological characteristics were compared in the H-2 production from the phototransformation of aqueous solutions of ethanol. Catalysts were characterized by means of N-2 adsorption-desorption, XRD, Raman, H-2-TPR, UV-Vis diffuse reflectance spectroscopy, XPS and CO chemisorption. The photocatalytic reaction was carried out in liquid and vapour phase. The photocatalytic transformation of ethanol((aq)) vapour over Pt/TiO2 and Pt-Ga/TiO2 catalysts was studied by in situ DRIFTS-MS. Differences in the photocatalytic transformation of ethanol((aq)) over Pt/TiO2 and Pt-Ga/TiO2 were determined. The effect of Ga is analysed in the light of the evolution of surface species under photocatalytic reaction conditions. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.