Facile ethanol/water solvothermal synthesis of {001} facet oriented WO3 architectures with superior simulated sunlight photocatalytic activities

Abstract

Flower shaped WO₃ architectures weaved up of ultrathin nanorods with oriented {001} facets were successfully prepared via a facile ethanol/water solvothermal strategy, at a low temperature of 100 °C for 4 h. Characterizations of phase, morphology, microstructure, optical absorption, BET surface area, photoluminescence, photoelectrochemical properties and photocatalytic behavior were systematically explored. The volume ratio of ethanol and water was confirmed to be a key parameter in regulating the morphology and microstructure of WO₃ by tuning the dielectric properties of the mixed solvent. The {001} faceted WO₃ structures exhibit improved photocatalytic activity for the degradation of methyl orange with the reaction rate constant k enhanced by 2.1 fold, compared to the hydrothermal counterpart assembled by thick, individual WO₃ nanorods. The active {001} facets with faster charge migration and enhanced surface area with more adsorption sites account for the excellent photocatalytic behavior. In addition, the active species in the photocatalytic reaction were investigated in detail, using terephthalic acid capture, ESR and radical scavengers. Combining the band edge positions of WO₃ and the redox potentials of the active species, a possible migration mechanism of photogenerated e⁻/h⁺ pairs on the surface of WO₃ is proposed. This work provides some new insights into the rational design and synthesis of facet-dependent 3D semiconductor photocatalysts.