Electrochromic Smart Windows Based on Nanometer-Thick Films of WO3 Nanowire/Cu and TiO2/NiO as Composite Electrodes

The application of electrochromic devices (ECDs) in smart windows provides a solution for energy savings and environmental protection. Here, a WO3 nanowire/Cu composite electrode was synthesized as an electrochromic cathode via hydrothermal and electrodeposition. Meanwhile, a TiO2 nanorod/NiO composite electrode was also prepared as an electrochromic anode via hydrothermal and electrodeposition. The Schottky junction structure formed between the Cu and WO3 film interface increases the rate of Li+ injection and extraction. In addition, the TiO2/NiO heterostructure can enhance the separation of the electrons and protons. The designed ECD exhibited properties of large optical modulation (74.5% at 633 nm), high coloration efficiency (94.1 cm2 C–1), and fast switching speed (3.1/1.6 s for coloration/bleaching). These characteristics make the WO3/Cu-TiO2/NiO electrochromic device a very promising smart window candidate for lighting control and energy-saving applications.