Synthesis and electrochromic properties of mesoporous tungsten oxide

The electrochromic properties of mesoporous tungsten oxide are described and compared to standard sol-gel films of WO3. The block copolymer template used in the synthesis was removed by solvent extraction and calcination methods, leading to mesoporous tungsten oxides which range from amorphous to crystalline depending on the removal treatment. The pores are not ordered but do exhibit a fairly regular diameter with an average size of 4 to 5 nm. The mesoporous tungsten oxides exhibit a well behaved electrochromic response and their electrochemical and optical reversibilities are better than those of the analogous sol-gel film. In addition, the mesoporous films exhibit higher rates for coloration and bleaching. The high surface area of these materials is responsible for this behavior and also leads to multiple peaks in the voltammetric scans.