The effect of carbon nanotubes on TiO2, for the photocatalytic H-2 gas production from water/alcohol mixtures, was investigated. The drastic synergy effect was found with an increase in the amount of H-2 gas by a factor of ca. 400 simply by mixing single walled carbon nanotubes (SWNTs) with TiO2. A comparison between SWNTs/TiO2 and Pt/TiO2 mixtures was made for the amount of H-2 gas produced. Based on the observed results, a plausible mechanism was proposed. (C) 2007 Elsevier B.V. All rights reserved.