An Electrostatically Strong Polyviologen-Reduced Graphene Composite Film for Highly Stable Electrochromic Systems

Polyviologen (PV)-reduced graphene oxide (rGO) nanocomposite films were fabricated by simple, one step reductive electropolymerization of cyanopyridinium based precursor monomer in an aqueous dispersion of graphene oxide (GO). Since the polymer formation and reduction of GO occurs at the same potential window, electrocodeposition technique was chosen for obtaining nanostructured PV-rGO film. The cyclic voltammetry experiments of PV-rGO displayed two well resolved, highly stable one-electron redox processes typical of viologen. Being a redox polymer, incorporation of rGO further enhances the electroactivity of the PV in the composite films. FTIR, Raman, XRD and XPS analysis revealed structural changes occurred after composite formation.  The PV-rGO nanostructured film exhibits a conspicuous electrochromism with low driving voltage and striking color changes. It was found that the PV-rGO film exhibit high coloration efficiency, fast response times and better cycling stability compared to pristine PV thin film. This performance can be attributed to the high stability of the electrochrome in the composite assembly induced by electrostatically driven non-covalent interactions between redox PV and rGO, high electrical conductivity and enlarged surface area through reinforced nanostructured graphene sheets for tethering PV molecules.