WO3 Nanorod Array-Modified Prussian Blue with Long Cycling Stability for High-Performance Dual-Band Electrochromic Materials

Dual-band electrochromic (EC) smart windows are a promising energy-saving technology because they can control indoor temperature by modulating the transmitted light in visible and near-infrared (NIR) regions. The key to smart windows is the preparation of well-performed dual-band EC materials (ECMs). Prussian blue (PB) is a typical anodic ECM with multiple colors, high capacity, and excellent electrochemical activity. However, due to the lattice expansion and low electron density of PB, the poor cycling stability and tedious modulation in the NIR region severely limit its wide application. Herein, we proposed a stabilization strategy to construct a one-dimensional WO3 array-modified PB with porous core–shell structures (named PB@WO3). Because of the porous structure and the heterostructure between WO3 and PB, the PB@WO3 showed excellent stability (the current density did not exhibit obvious changes after 1000 cycles) and high coloring efficiency (62.3 cm2/C). Besides, the modification of WO3 also provided PB@WO3 with a dual-band modulation ability under low voltages (35.14% at 633 nm, 60.55% at 1200 nm, and 67.18% at 1800 nm). Simultaneously, the combination of WO3 and PB rendered PB@WO3 with three colors, i.e., white, blue, and green. Furthermore, the one-dimensional array structure and the interaction between WO3 and PB imparted PB@WO3 with fast switching speed (0.5 and 0.5 s per each coloration and bleaching cycle, respectively).