Hiroshi Inaba

Electrochromic display device of tungsten trioxide and prussian blue films using polymer gel electrolyte of methacrylate

Abstract The electrochemical redox behaviors and electrochromic characteristics of tungsten trioxide (WO 3 ) and Prussian Blue (PB) thin films have been examined in two- and three-electrode systems using polymer gel electrolyte ( pge ), which is based on composites of copolymer of 2-hydroxyethylmethacrylate and neopentylglycoldimethacrylate containing lithium perchlorate in the mixture solution of butylene carbonate and propylene carbonate. The conductivity of the pge prepared was ca . 10 −3 S cm −1 at 30 °C. A reversible color change between blue and colorless was observed when an appropriate potential was applied repeatedly to the WO 3 - and PB-based electrochromic device ( ecd ). With the potential cycling more than 10 5 times less than 10% of the electrochromic characteristics were lost. The response time of the bleaching process of ecd using pge is higher than that using a solution electrolyte and the response time of coloration using pge is analogous to that using a solution electrolyte. The ecd properties characterized provide the optimum feature of the practical device.

Electrochemical intercalation of cations into an amorphous WO3 film and accompanying changes in mass and surface properties

Abstract The electrochemistry of electrodes coated with amorphous WO3 film in propylenc carbonate containing 0.1 M LiClO4, NaClO4, KPF6 or tetraethylammonium (TEA) perchlorate was examined. The surface density of redox-active sites on the WO3 film coated electrode is larger for smaller cations (Li+ > Na+ > K+). The charge transfer rate was also faster for smaller cations. In the KPF6 solution, the solvophilicity of the film surface increased with potential cycling, while no significant changes were observed in the LiClO4 solution and NaClO4 solution. In the LiClO4 solution, an apparent mass increase during cation intercalation, estimated using an AT-cut quartz crystal resonator, was roughly in agreement with the mass number of Li+. However, in the NaClO4 solution, an apparent mass increase was significantly larger than the mass number of Na+; this may be caused by stress generated by intercalation of the massive cation. Electrochemistry was not observed in the TEAClO4 solution. Proton intercalation was not observed in the TEAClO4 solution even in the presence of water (1.5 wt%), but was observed in the presence of CF3COOH (10 mM).