Electrochromic strategy for tungsten oxide/polypyrrole hybrid nanofiber materials

Abstract

High-quality hybrid nanofibers were fabricated with the aim of studying their feasibility as electrochromic systems. Tungsten oxide/polypyrrole films were electrochemically synthesized into four different ionic liquids: 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (BMIMTFSI), and 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl) imide (BMPTFSI), followed by electrospinning deposition. The influence of ionic liquid on the morphology of formed hybrid nanofiber samples was observed by scanning electron microscopy (SEM) measurements. Energy dispersive X-ray spectroscopy (EDX) was also employed to confirm the compositions of nanofibers. Electrochromic devices fashioned from these hybrid nanofiber arrays were found to display remarkable electrochromic performance with reversible color change, fast optical modulation and superior cycling stability. These improvements can be attributed to the high porosity of the nanofibers, their larger accessible surface area and rational combination of two electrochemically active materials. PPy/WO3/BMIMPF6 based device showed marked enhancement of electrochromic contrast and coloration efficiency over other nanofiber based devices: the transmittance change of 47.41% along coloration efficiency of 329.45 cm2/C. These synergistic organic-inorganic nanostructures pave the way for forming new materials to be used in advanced applications.