Hydrogen production from the photocatalytic reforming of methanol has been conducted on TiO2 with a range of transition metal co-catalysts. The noble metals Pt, Pd and Au catalysts showed much higher activity than non-noble metal catalysts, and this conforms to the general trend of hydrogen production being linked to the ease of reduction of the corresponding transition metal oxides. Metal oxides such as NiO and Fe2O3, with a positive enthalpy of reduction show negligible amounts of hydrogen production. However, when the NiO nanoparticles were carefully pre-reduced, the resulting Ni-NiO/TiO2 showed a big enhancement in catalytic activity. The reducibility trends observed in the study should provide insight into the development of potential catalysts for the photocatalytic splitting of water. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.