Tungsten trioxide (WO3) films with nanoporous morphology were prepared by a facile and simple method utilizing commercially available WO3 nanopowder with polyethylene glycol to guide porosity of a nanostructure, and the resulted photoanode was working efficiently for visible-light-driven water oxidation. The SEM observation and XRD measurement revealed formation of interparticulate nanopores between the well-connected WO3 crystaline particles of dimension ca. 100-200 nm. The nanoporous WO3 electrode generated a significant photoanodic current density of 1.8 mA cm(-2) due to water oxidation at 1.0 V versus Ag/AgCl on visible light irradiation (lambda>390 nm, 100 mW cm(-2)). The onset potential of the WO3 electrode was 0.67 V versus a reversible hydrogen electrode (RHE), being lower by 0.56 V than the theoretical potential for water oxidation (1.23 V versus RHE). The incident photon to current conversion efficiency (IPCE) reached 45% at 400 nm of light wavelength and 1.04 V versus Ag/AgCl of an applied potential. The photoanodic current and photostability of the WO3 electrode were improved by addition of Co2+ ions in the electrolyte solution during photoelectrocatalysis. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.