In this work, graphite-like C3N4 (g-C3N4) is deposited on the surface of ZnO nanowires (NWs) and a nanocomposite g-C3N4/ZnO photoanode is made for the photoelectrochemical (PEC) water splitting under air mass 1.5 (AM 1.5) simulated sunlight illumination. Pt nanoclusters are further incorporated at the g-C3N4/ZnO interface and a tricomponent C3N4/Pt/ZnO photoanode is adapted. Both g-C3N4 and ZnO act as the light absorber to create electron hole pairs, while the Pt nanoclusters serve as the cocatalyst to facilitate the transfer of the photogenerated electrons. The g-C3N4/Pt/ZnO photoanode generates a photocurrent density of 120 mu A cm(-2) at 0.5 V vs. Ag/AgCl in a 0.5 M Na2SO4 solution, which is 9 times higher than that of the anode made of ZnO and 4.5 times higher than that of the g-C3N4/ZnO anode. Furthermore, with the visible light absorption of g-C3N4, the g-C3N4/Pt/ZnO photoanode gives a photocurrent density of 32 mu A cm(-2) at 0.5 V vs. Ag/AgCl under visible light (lambda > 420 nm) illumination. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.