Carbon-doped tungsten trioxide (WO3) films were produced using a spray-pyrolysis methodology, with glucose used as the carbon dopant source. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, UV-vis, scanning electron microscopy, and solid-state nuclear magnetic resonance. The photoelectrochemical activity was evaluated under near UV-visible light and visible light only irradiation conditions. The presence of carbonate-type species in the C-doped sample was confirmed by XPS and SSNMR. The C-doped WO3 electrodes exhibited photocurrent densities up to 1.6 mA/cm(2) in 1 M HCl electrolyte and as high as 2.6 mA/cm(2) with the addition of methanol as a sacrificial agent. A high contribution (similar to 50%) of the photocurrent density was observed from visible light. C-doped WO3 produced approximately 50% enhanced photocurrent densities compared with the undoped WO3 electrode synthesized using the same procedures. The photoelectrochemical performance was optimized with respect to several synthetic parameters, including dopant concentration, calcination temperature and film thickness. These results indicate the potential for further development of WO3 photocatalysts by simple wet chemical methods, and provide useful information towards understanding the structure and enhanced photoelectrochemical properties of these materials. (c) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.