基于Cu3(HHTP)2薄膜的离子液体电致变色电极

室温离子液体具有宽电化学窗口和良好的环境稳定性, 是电致变色器件的理想电解质。然而传统电致变色材料的晶格间隙较窄, 限制了离子液体中大尺寸离子的扩散, 且大离子反复脱/嵌会破坏传统电致变色材料的结构, 导致性能衰减。金属有机框架材料(MOFs)是一种具有拓扑结构的多孔晶态材料, 有望为离子液体中大尺寸离子的传输提供通道。本工作在导电玻璃表面制备了三亚苯类Cu₃(HHTP)₂ (HHTP=2,3,6,7,10,11-六羟基三苯并菲) MOF薄膜, 并研究了Cu₃(HHTP)₂薄膜在离子液体电解质中电化学和电致变色行为和性能。结果表明, 相对于传统的LiClO₄/PC和NaClO₄/PC电解质, Cu₃(HHTP)₂薄膜在离子液体[EMIm]BF₄中表现出更低的接触电阻和更高的离子扩散效率, 电极的着色/褪色速度得到了显著提高(着色时间由10.3 s缩短至8.0 s, 褪色时间由23.6 s缩短至5.2 s)。同时, Cu₃(HHTP)₂薄膜在[EMIm]BF₄中也具有更高的光调制范围和着色效率。这项工作展现出MOFs/离子液体电化学体系在电致变色领域中的潜在应用价值。

Cu3(HHTP)2 Film-based Ionic-liquid Electrochromic Electrode

Room temperature ionic liquid shows wide electrochemical windows and good environmental stability, which is expected as an ideal electrolyte for electrochromic devices. However, the small crystal spacing of traditional electrochromic materials limits the diffusion of large ions in ionic liquid. Repeated deintercalation/ intercalation of large ions could also destroy the structure of traditional electrochromic materials, resulting in performance degradation. Metal-organic frameworks (MOFs) are topologically porous materials with a large intrinsic nano to microporous structure in crystalline, which are expected to provide channels for transporting large-sized ions in ionic liquids. In present work, triphenylene-based MOFs Cu₃(HHTP)₂ films were prepared on the surface of the conductive glass. Electrochemical and electrochromic behavior of Cu₃(HHTP)₂ films were studied in traditional propylene carbonate (PC)-based electrolyte and ionic liquid-based electrolytes. The results show that, compared with the traditional LiClO₄/PC or NaClO₄/PC electrolyte, Cu₃(HHTP)₂ film displays low contact resistance and high ion diffusion efficiency in the ionic liquid [EMIm]BF₄ electrolyte. Switch speed of the electrochromic electrode is significantly improved with coloring time being reduced from 10.3 s to 8.0 s, and bleaching time being reduced from 23.6 s to 5.2 s. Meanwhile, Cu₃(HHTP)₂/[EMIm]BF₄ electrochromic system also shows a larger light modulation range and coloring efficiency. This work demonstrates the potential of MOFs/ionic liquid electrochemical system in the field of electrochromic device.