A modified photoetching process is found to significantly improve the photocatalytic activity of Pt/CdS photocatalyst for solar hydrogen production. The photoetching process was carried out by dispersing Pt/CdS photocatalyst particles in an aqueous ammonium sulfite ((NH4)(2)SO3)solution under a vacuum-degassed condition. The Pt/CdS particles were then exposed to photo-radiation (350-800 nm) for 20 h. The rate of hydrogen production via visible light photooxidation of aqueous (NH4)(2)SO3 solution over the photochemically treated Pt/CdS is about 130 times higher than that of untreated Pt/CdS samples. Effects of platinum loading technologies on the photocatalytic activity of Pt/CdS photocatalyst for hydrogen production are also investigated in this paper. Photochemically deposited Pt/CdS photocatalyst in an aqueous ammonium sulfite solution has shown a 100% increase in hydrogen production rate over that of photocatalysts traditionally photo-platinized in an aqueous glacial acetic acid solution. The prepared catalysts are characterized using XRD, FESEM, TEM, BET and XPS techniques and the changes of Pt particle size and surface elementary states of Cd and S are observed before and after the photoetching process. (C) 2012 Elsevier B.V. All rights reserved.