Photoelectrochemical anodization for the preparation of a thick tungsten oxide film

Nanoporous WO3 with a thickness of about 2.6 μm was achieved by photoelectrochemical anodization; this thickness was around twice the thickness possible with normal (photo-absent) anodic film. The thickness increase is ascribed to the much formation of a protective crystalline oxide on the surface and acceleration of dissolution at the tip by holes generated during illumination. The nanoporous WO3 film prepared by photoelectrochemical anodization shows photocurrents of 1.85 mA/cm2 in 0.33 M H3PO4 under AM 1.5 illumination, a value nearly four times higher than that for film prepared with normal anodization.

► Photoelectrochemical anodization produces nanoporous WO3 with twice the thickness.
► The thickness increase is ascribed to the formation of a protective crystalline oxide.
► Dissolution at the tip is accelerated by holes generated during illumination.