Anodic formation of a thick three-dimensional nanoporous WO3 film and its photocatalytic property

We report an efficient solar-light-driven photocatalyst based on three-dimensional nanoporous tungsten trioxide (WO3) films. These films are obtained by anodizing W foils in fluoride-containing electrolytes at room temperature and under low applied voltages with an efficient growth rate of 2 μm h− 1. The maximum thickness of the films is ~ 3 μm that exceeds those of previously reported anodized WO3 films in fluoride-containing electrolytes. By investigating the photocatalytic properties of the films with thicknesses ranging from ~ 0.5 to ~ 3 μm, the optimum thickness of the nanoporous film is found to be ~ 1 μm, which demonstrates an impressive 120% improvement in the photocatalytic performance compared to that of a RF-sputtered nanotextured film with similar weights. We mainly ascribe this to large surface area and smaller bandgap.

► Anodized 3D nanoporous WO3 films were prepared at room temperature and under a low applied voltage.
► The thicknesses of the nanoporous WO3 films were up to ~ 3 μm with a growth rate of ~ 2 μm h− 1.
► Field-assisted dissolution was the dominate mechanism to the formation of this 3D nanostructure.
► The crystal phase of the nanoporous film is orthorhombic with a relatively small bandgap of 2.73 eV.
► The photocatalytic property of the nanoporous film shows 120% improvement compared to a sputtered film.