1 | Page Supporting Information Enhancing photocatalytic efficiency of TiO 2 nanopowder for H 2 production by using non-noble transition metal co-catalysts Phong D. Tran a*, Lifei Xi b , Sudip K. Batabyal a , Lydia H. Wong b* , James Barber b,c,d , Joachim Say Chye Loo b* a Energy Research Institute@NTU, Research TechnoPlaza, 5th Storey, 50 Nanyang Drive, Singapore 637553. Fax: +6567906748; Tel: +6567904626; E-mail: dptran@ntu.edu.sg b Solar Fuel Laboratory, School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798. Fax: +6567909081; Tel: +6567904603; E-mail: JoachimLoo@ntu.edu.sg and LydiaWong@ntu.edu.sg c Division of Molecular Biosciences, Imperial College London, London SW7 2AZ, UK d BioSolar Laboratory, Department of Material Sciences and Chemical Engineering, Polytechnic of Torino, Corso Duca degli Abruzzi, 24, 10129 Torino, Italy Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics This journal is © The Owner Societies 2012