Sub-second electrochromic switching and ultra-high coloration efficiency in halloysite nanoclay incorporated metallo-supramolecular polymer nano-hybrid based electrochromic device

摘要

Herein, we have synthesized a series of polymer nano-hybrids (polyFe-hHNT-2, polyFe-hHNT-5, and polyFe-hHNT-10) of an electrochromic metallo-supramolecular polymer (polyFe) with a modified tubular hydroxylated halloysite nanoclay (hHNT) by effective electrostatic interaction through ion exchange. The spectroscopic studies exhibit the operative interaction and composite formation between hHNT and polyFe while the structural characterizations through X-ray diffraction reveal the intercalation of polymer chains into rolled hHNT layers. The morphological investigations manifest the significant decrement of the diameter of hHNT tubes after nanocomposite formation by intercalation induced exfoliation of rolled hHNT nanotubes through interaction with polyFe polymer chains in inner and outer surfaces. The incorporated hHNTs enhance the thermal stability and ionic conductivity in the nanocomposite. The composite based electrochromic devices (ECDs) exhibit a fairly stable EC color change from purple to transparent under a controlled potential switching from -2 V to +3 V. The electrochromic switching times are considerably improved by 82% for bleaching (2.95 s -> 0.53 s) and 47.2% for coloring (0.72 s -> 0.38 s) in polyFe-hHNT-5 composite compare to pristine polyFe based ECD. The chronoamperometric study confirms the charge required to change the color is also significantly decreased in the composites due to swift counter ion diffusion, better ionic conductivity and effective charge neutralization by the anionic sites of hHNTs in composites. Hence, the coloration efficiency is also enhanced in composite ECDs to provide similar to 117.8% raise of coloration efficiency (263.05 -> 572.77 cm(2)C(-1)) compared to pristine polyFe. Therefore, the present work can provide a viable strategy to improve the electrochromic parameters of an electrochromic polymer.