Enhancement effect of transition metal cations on the electrochromic properties of nanostructure tiron doped polypyrrole film

• PPy–tiron film is uniform, stable and adherent on FTO electrode.
• Electrochromic properties have been studied in different supporting electrolytes.
• Electrochromic properties of film enhanced by choosing tiron as chelating dopant.
• Transition metal cation as electrolyte greatly enhances ΔT% and stability of film.

Herein, the electrochemical polymerization of pyrrole on the surface of FTO electrode is described in the presence of tiron as doping anion with the aim of producing uniform, adherent, conducting and electroactive films. The use of tiron promoted charge transfer during electropolymerization and allowed reduced electropolymerization potential of polypyrrole (PPy). The resultant polymer was characterized via scanning electron microscopy (SEM), electrochemical and spectroelectrochemical methods. SEM study indicates that the PPy–tiron has a spherical morphology with primary particles size of 40–60 nm. The spectroelectrochemical analysis revealed the PPy–tiron has distinct electrochromic properties in the presence of different transition metal salts (CoCl2, NiCl2, CuCl2, FeCl2, MnCl2 and ZnCl2) as supporting electrolyte compared to conventional electrolyte solutions. Results showed that the electrochromic properties of PPy–tiron such as optical contrast, switching time, film stability and coloration efficiency were greatly enhanced in the presence of transition metal cations. PPy–tiron exhibited a switching time of 1.5 s and the maximum transmittance contrast (ΔT%) and coloration efficiency calculated 62% and 136.7 cm2 C−1 at 800 nm in the presence of Ni2+ ion, respectively.

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