Highly crystalline multi-layered WO3 sheets for photodegradation of Congo red under visible light irradiation

Abstract

We report a simple synthetic method for few- to multi-layered tungsten oxide (WO3) sheets through complexation of a sodium tungstate dihydrate precursor by 1-propanol, sulfuric acid and urea. The formation of tungsten oxo-clusters and their organized transformation into few-to-multi-layered WO3 sheets occurs during the hydrolysis stage, and crystallization occurs during the post-sintering process. XRD results exhibited a phase transformation from monoclinic to orthorhombic beta-WO3 due to post sintering effects. The as-prepared material appears as self-organized few- to multi-layered WO3 sheets. The as-prepared and sintered samples are used for the photodegradation of Congo red (CR) under visible light irradiation. A sample sintered at 300 degrees C (S-300) shows much higher photocatalytic activity than the as-prepared WO3 and those sintered at 180 degrees C and 400 degrees C. The S-300 photocatalyst has the optimal performance in the removal of CR, which is due to high specific surface area and patches of crystalline sites on the photocatalyst surface. These sites can suppress the recombination of electrons and holes by accelerating the charge carrier transformation within the photocatalyst.