Studying electron transfer at electrochromic tungsten oxide sol-gel films with scanning electrochemical microscopy (SECM)

Electron transfer processes at tungsten oxide films prepared by the sol-gel method were investigated and characterized by scanning electrochemical microscopy (SECM) and cyclic voltammetry. The feedback mode of the SECM was used for studying the localization and mechanism of the heterogeneous charge transfer at tungsten oxide thin films, which were deposited on conducting, i.e., tin oxide, and insulating substrates. Investigating the feedback current as a function of the mediator concentration, thickness of the tungsten oxide film and the nature and concentration of the electrolyte, allow determination of the rate limiting step and conductivity of the film.