Thick porous tungsten trioxide films by anodization of tungsten in fluoride containing phosphoric acid electrolyte

• DOI: 10.1016/j.elecom.2009.08.014
• Publication Date: 2009-08-27T02:43:01Z
• Authors: Min Yang; Nabeen K. Shrestha; Patrik Schmuki
• Keywords: Tungsten trioxide; Anodizing; Phosphoric acid; Orthorhombic crystal system

Abstract In the present work, we report on the formation of mesoporous thick tungsten trioxide films grown on tungsten foil by anodization in fluoride containing concentrated phosphoric acid (85%) electrolyte. Under optimized experimental conditions, mesoporous WO 3 films with a thickness up to approximately 2 μm are formed. SEM shows the films to consist of a connected network with a typical pore and feature diameter of ca 50 nm. These films as formed are amorphous and can be annealed to orthorhombic WO 3 structure. These thick porous films can show significant enhanced electrochromic and improved photocatalytic properties.