Xiaohui Sun,Dong Wang,Wei Wu,Xueying Zhao,Xuyang Zhang,Bo Wang,Xianhui Rong,Guohua Wu,Xiangwei Wang
The dual-band electrochromic smart windows (DESW) can selectively modulate visible (VIS) and near-infrared (NIR) transmittance, which is expected to effectively reduce building energy consumption. However, the complex preparation of dual-band electrochromic materials has restricted the further development of DESW. In this work, amorphous and crystalline Ti-doped WO3·2H2O (TiWH) were synthesized by a simple precipitation method, which does not require strict control of the oxygen content and temperature. Ti doping reduced the crystallinity of WO3·2H2O and increased the specific surface area. 3% TiWH films exhibited excellent dual-band electrochromism with high transmittance modulation (633 nm: 83.8%, 1050 nm: 72.5%), fast response time (bleached/colored time: 14.9/15.3 s at 633 nm, 16.0/3.5 s at 1050 nm), good coloration efficiency (633 nm: 22.8 cm2 C–1, 1050 nm: 90.8 cm2 C–1), and high capacitance of 47.1 mF cm–2 at 0.1 mA cm–2. The electrochromic device can still maintain good dual-band electrochromism (bright, cool, and dark modes). The excellent dual-band electrochromism and energy storage make TiWH have a good application prospect in green buildings.
Lun Yang,Xiaobin Zhu,Shijie Xiong,Xinglong Wu,Yun Shan,Paul K. Chu
Tungsten trioxide dihydrate (WO3·2H2O) nanoplates are prepared by in situ anodic oxidation of tungsten disulfide (WS2) film on carbon fiber paper (CFP). The WO3·2H2O/WS2 hybrid catalyst exhibits excellent synergistic effects which facilitate the kinetics of the hydrogen evolution reaction (HER). The electrochromatic effect takes place via hydrogen intercalation into WO3·2H2O. This process is accelerated by the desirable proton diffusion coefficient in the layered WO3·2H2O. Hydrogen spillover from WO3·2H2O to WS2 occurs via atomic polarization caused by the electric field of the charges on the planar defect or edge active sites of WS2. The optimized hybrid catalyst presents a geometrical current density of 100 mA cm–2 at 152 mV overpotential with a Tafel slope of ∼54 mV per decade, making the materials one of the most active nonprecious metal HER catalysts.
HighlightsWhat are the main findings?WO3·2H2O films exhibit pronounced pH-dependent electrochromism in aqueous electrolytes.Lower-pH LiCl provides the best overall electrochromic performance in the Li+system.ZnCl2shows stronger pH-dependent kinetic limitations than LiCl.What are the implications of the main findings?The pH effect in hydrated WO3depends strongly on the cation involved.Multivalent-ion systems are more sensitive to electrolyte-controlled transport and interfacial conditions.pH control offers a practical route to improving aqueous WO3-based electrochromic systems.Aqueous electrochromic systems based on tungsten oxide (WO3) have attracted increasing attention because of their high ionic conductivity, low cost, and improved safety compared with organic systems. However, the role of electrolyte pH in regulating the electrochromic behavior of hydrated WO3films remains insufficiently understood, particularly across cation systems with different valences. In this work, amorphous WO3·2H2O films were electrodeposited on ITO substrates and systematically evaluated in LiCl and ZnCl2aqueous electrolytes with different pH values, with acidic AlCl3used as a supplementary trivalent system. The results reveal pronounced pH-dependent electrochromic behavior in both the monovalent and divalent systems. In LiCl, acidic conditions, especially pH 2.0, gave the best overall performance, including high optical modulation and improved cycling stability, while the dominant pseudocapacitive charge-storage behavior was largely preserved. In ZnCl2, films tested at pH 1.5–2.0 showed significantly better electrochromic performance than those at higher pH values, indicating a much stronger kinetic sensitivity to pH. Combined experimental and first-principles results show that electrolyte pH influences not only proton availability, but also the cation-dependent interfacial charge-compensation environment in hydrated WO3films.
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