Electrochromism in mesoporous nanowall cobalt oxide thin films prepared via lyotropic liquid crystal media with electrodeposition

Mesoporous nanowall cobalt oxide (Co3O4) thin films were prepared by a liquid crystal templated electrodeposition method. The as-prepared Co3O4 thin films exhibited a highly porous nanowall structure composed of many interconnected nanoflakes with a thickness of 10–25 nm. The nanoflakes showed continuous mesopores ranging from 4 to 15 nm and formed a net-like structure leaving pores of 20–250 nm. The electrochromic performances of the Co3O4 thin films were characterized by means of transmittance, cyclic voltammetry (CV) and chronoamperometry (CA) measurements. The Co3O4 thin film annealed at lower temperature exhibited better electrochromic performance. The film annealed at 200 °C exhibited a transmittance modulation of 40% at 633 nm with a coloration efficiency of 31 cm2 C−1, and fast response times with 2.5 s for coloration and 2 s for bleaching. The high porosity and big surface area were responsible for the enhanced electrochromic properties.