Cobalt Oxide Ordered Bowl-Like Array Films Prepared by Electrodeposition through Monolayer Polystyrene Sphere Template and Electrochromic Properties

In this paper, we report a facile method to produce large-area periodical bowl-like cobalt oxide (Co3O4) array films based on a self-assembled monolayer polystyrene sphere template and electrodeposition. After the template is removed, the resulting Co3O4 films consist of periodic, interconnected networks of monodisperse submicrometer pores With a diameter of I pm. Moreover, the individual bowl contains a large number of pores with a diameter of 50 +/- 20 nm and the interstices between bowls are filled with Co3O4 nanoflakes. As a preliminary test, the electrochromic properties of the Co3O4 macrobowl arrays have been investigated and it is found that the him annealed at lower temperature exhibits better electrochromic performance. The Co3O4 array film annealed at 200 degrees C exhibits good electrochromism with color changes from dark gray to pale yellow and fast response times. The coloration efficiency is calculated to be 29 cm(2) C-1 at 633 nm, with a variation of transmittance up to 33 %.