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 WO 3 nanowire/Cu composite electrode was synthesized as an electrochromic cathode via hydrothermal and electrodeposition. Meanwhile, a TiO 2 nanorod/NiO composite electrode was also prepared as an electrochromic anode via hydrothermal and electrodeposition. The Schottky junction structure formed between the Cu and WO 3 film interface increases the rate of Li + injection and extraction. In addition, the TiO 2 /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 cm 2 C –1 ), and fast switching speed (3.1/1.6 s for coloration/bleaching). These characteristics make the WO 3 /Cu-TiO 2 /NiO electrochromic device a very promising smart window candidate for lighting control and energy-saving applications.