Core-shell CdS@ZnS nanocomposites are directly grown on indium tin oxide (ITO) substrate without conductive additives and contamination of organic surfactants via a onestep hydrothermal method. Performed CdS@ZnS core-shell nanocomposites are evolved from ZnO nanowires by reacting with CdS precusors at 100 degrees C for 5 h. The shell thickness could be tuned by varying the CdS precursor, and the porous structure with 40 nm shell exhibited improved hydrogen evolution of around 5700 pmol cm(-2), 1.5 times higher than that of structure with 20 nm shell. Protective ZnS shell can effectively passivate the surface trap states of the CdS cores, greatly improving the photocatalytic activities of the CdS@ZnS core-shell architecture. The core-shell heterostructure with the staggered band alignments facilitates the separation and transport of the photoexcited charge carriers, and the localized acceptor states induced by intrinsic defects provide pathway for carriers transport. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.