A two-compartment photoelectrochemical cell consisting of a CdS photoanode immersed in aqueous sulfide solution, Nafion membrane, platinum cathode and sulfuric acid solution as the dark-compartment electrolyte was constructed. The effects of the concentrations of the electrolytes, membrane surface and cathode materials on the performance of the cell were studied to reach high quantum yield of hydrogen production. Under optimized conditions, light to hydrogen conversion efficiency up to 12% was observed under sun light illumination. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.