Nanoporous and nanoflakes tungsten oxide (WO3) films were produced on metallic W foil via one-step potentiostatic anodization method. The effect of annealing temperature on the morphological, structural and optical properties of the materials was studied. The nanoflakes films conserved their topology under different annealing temperatures (up to 500 degrees C) with particle sizes in the range of 46 nm. However, the nanoporous films showed a gradual deterioration in the porous structure upon annealing up to 500 degrees C. X-ray diffraction and Raman spectroscopy measurements were done to investigate the structural properties of the materials. The photoelectrochemical activity tests reveal that nanoflakes annealed at 500 degrees C exhibited a superior photocatalytic performance among all other samples, achieving a photocurrent density of 1.17 mA cm(-2) at 1.2 V-SCE under AM 1.5 illumination. The UV Vis absorption and incident photon-to-current efficiency measurements are used to explain the activity morphology relationship in such nanostructured films. Also, the stability of the films was investigated under light on/off conditions. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.