Effects of thermal treatment on the anodic growth of tungsten oxide films

This work reports the investigation of the effects of thermal treatment on anodic growth tungsten oxide (WO3). The increase of the thermal treatment temperature above 400 degrees C significantly influences WO3 film where high porosity structure reduces to more compact film. As-grown film is amorphous, which transforms to monoclinic/orthorhombic phase upon annealing at 300-600 degrees C. With the reducing of porous structure, preferential growth of (002) plane shifts to (020) plane at 600 degrees C with more than twentyfold increase of peak's intensity compared to the film annealed at 500 degrees C. Films annealed at low thermal treatment show better ion intercalation and reversibility during electrochemical measurements; however, it has larger optical band gap. Photoelectrochemical measurement reveals that film annealed at 400 degrees C exhibits the best photocatalytic performance among the films annealed at 300-600 degrees C. (C) 2015 Elsevier B.V. All rights reserved.