Niobium doped tungsten oxide mesoporous film with enhanced electrochromic and electrochemical energy storage properties.

Exploring high performance cathode materials is of great means for the development of bi-functional electrochromic energy storage devices. Herein, Nb-doped WO ₃ mesoporous films as integrated high-quality cathode are successfully constructed via a facile sol-gel method. Chemical state and crystallinity of the WO ₃ based films are significantly influenced by doping concentration. Compared with the pure WO ₃ , the optimal Nb-doped film shows improved optical-electrochemical properties with high specific capacity (74.4 mAh g ^-1 at 2 A g ^-1 ), excellent high-rate capability, large optical contrast (61.7% at 633 nm), and ultra-fast switching speed (3.6 s and 2.1 s for coloring and bleaching process, respectively). These positive features suggest the potential application of Nb-doped WO ₃ mesoporous cathode. Our research paves the way for the development of multifunctional photoelectrochemical energy devices.
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