Mengtao Sun,Likun Wang,Guohua Shi,Qiying Liu,Gang Xu,Yong Liu,Gaorong Han
Dual-band electrochromic (EC) smart windows, capable of selectively regulating visible (VIS) and near-infrared (NIR) light, are one of the most attractive candidates for significantly reducing the energy consumption of buildings. Niobium-tungsten bimetallic oxides exhibit a fast ion exchange rate and high cycle stability in the electrochemical field because of various structural chemistry in the pseudobinary system Nb2O5/WO3, showing excellent dual-band EC potential. Herein, we employ a facile hydrothermal technique to synthesize Nb18W16O93 (NWO) films with low temperature and facile procedure. The obtained NWO films exhibit impressive dual-band electrochromic performances, including high optical regulation (radiation blocking rates of 33.1% and 77.5% in the VIS and NIR band) and short coloring/bleaching time (12 s/2.6 s at 633 nm and 6.5 s/6.1 s at 1600 nm). These results demonstrate that NWO is a high-performance dual-band EC material and provide a practical strategy to synthesize the NWO electrodes with nanorod stacking architectures in a facile and low-cost way.
It is reported that by introducing structural water into amorphous tungsten oxide and using multivalent Al 3+ as electrolyte ions, the tungsten oxide hydrate films exhibit dramatically enhanced dual-band EC performance. The structural water triggers the surface reduction of tungsten at a relatively low reduction potential, which governs the selective regulation of NIR light. The fast electrochemical kinetics and negligible structural destruction during the surface redox process enable fast and ultrastable NIR regulation. Increasing the reduction potentials, the Al 3+ intercalates into the lattice, accompanied by injection of electrons, resulting in the formation of polaron absorbing visible light. The high charges and small radius of Al 3+ , and the enlarged ion diffusion channels by structural water synergistically facilitate the ion insertion/extraction, leading to enhanced EC performance in the visible light region. The tungsten oxide hydrate film is used as a working electrode to pair with an electrocatalytic counter electrode, with the presence of redox couples in Al 3+ based electrolyte, to form a full EC device that exhibits NIR selectivity of 0.66, and cycling stability of 20 000 cycles in NIR region and 8000 cycles in visible region, which enables to design and fabricate large-size high-performance dual-band EC smart window for controllable management of solar heat and light.
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