A new series of ZnmIn2S3+m (m = 1-5, integer) photocatalysts was synthesized via a simple hydrothermal method. X-ray diffraction (XRD), Raman spectra, UV-vis-near-IR diffuse reflectance spectra (UV-vis), X-ray fluorescence (XRF) and scanning electron microscope (FESEM) were used to characterize these photocatalysts. These ZnmIn2S3+m, photocatalysts had a similar layered crystal structure. The absorption edge of ZnmIn2S3+m shifted to shorter wavelength as the atomic ratio of Zn/In in the synthetic solution was increased (i.e. m increased from 1 to 5). Additionally, the morphology of ZnmIn2S3+m greatly depended on the atomic ratio of Zn/In. The photocatalytic activity of ZnmIn2S3+m was evaluated by photocatalytic hydrogen production from water under visible light. The Zn2In2S5 product, with quantum yield at 420 nm determined to be 11.1%, had the highest photocatalytic activity among these ZnmIn2S3+m (m = 1-5, integer) photocatalysts. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.