To investigate the role of metal sulfides as co-catalyst for photocatalytic hydrogen production under visible light irradiation, we have loaded small amounts of transition-metal sulfides (MS), such as NiS, CoS and CuS, onto the surface of CdxZn1-xS solid solution. It can be found that the rate of H-2 evolution over the MS/Cd0.4Zn0.6S was 5 times higher than that of the pure Cd-0.4Zn0.6S, and is comparable to the Cd0.4Zn0.6S modified with 1 wt% platinum (Pt) co-catalysts. The MS/Cd0.4Zn0.6S photocatalysts were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), UV-visible spectrophotometer (UV-vis), and photoluminescence (PL) spectroscopy. It can be speculated that the MS provided active sites for H-2 production and caused the migration of excited electrons from Cd0.4Zn0.6S toward MS, leading to the enhancement of photocatalytic activity. (C) 2012 Elsevier B. V. All rights reserved.