Enhanced electrochromic porous cobalt oxides nanowall electrodes: A new way for fast modulation of yellow-brown light

Abstract Construction of high-efficiency electrochromic electrodes with large and fast optical modulation is important for development of advanced smart windows. In this work, we report highly porous metal oxide (Co 3 O 4 ) nanowall arrays via solvothermal method. Noticeable porous structure and cross-linked network are realized in the interconnected Co 3 O 4 nanowalls. Improved porosity and faster ion/electrons transportation are combined in this unique nanowall architecture. The electrochromic properties of Co 3 O 4 nanowall arrays are characterized via optical-electrochemical measurements. Cyclic voltammetry and transmittance tests demonstrate that the interconnected Co 3 O 4 nanowall arrays show larger (52% at 632 nm) and faster (0.8–0.9 s) modulation of yellow-brown light, and higher electrochemical reactivity and smaller polarization as compared to the common Co 3 O 4 nanowall arrays (31% at 632 nm with 1.3–1.5 s). The enhanced optical modulation is owing to the porous cross-linked nanowall structure with more active sites and shorter diffusion paths for ions/electrons.