Enhancement on electrochromic properties of WO3-based electrode prepared with hierarchical ZnO nanobricks

Abstract This paper reports the enhancement of the electrochromic properties of a tungsten trioxide (WO3)-based electrode through the synthesis of hierarchical zinc oxide (ZnO) nanobricks (ZnBs). The two-step hydrothermal method and the radio frequency (RF) sputtering were used for the growth of highly conductive ZnBs and the coating of electrochromic WO3 film, respectively. Three different structures were prepared: an electrode without ZnBs, electrode with single-layered and electrode with double-layered ZnBs. The electrochromic properties of the electrode were improved significantly attributing to the preparation of double-layered ZnBs. Compared to the electrode without ZnBs, the electrode with double-layered ZnBs showed a fast response at coloring (response time reduced from 15.9 s to 12.8 s, speeding by 19.5%) with an enhanced coloration efficiency (from 4.33 cm2-C−1 increasing to 18.28 cm2-C−1, improving by 4.2-fold). After repeating the redox for 2000 cycles, the peak current densities of anode and cathode were 60.3% and 52.2%, respectively of their initial densities. Stable electrochromic performance of the electrode was achieved.