Structural, Optical, Electrical and Electrochemical Studies of Transitional Metal Oxides Doped PIn/PCz Copolymer Composites

Two sets of nanocomposites made of Polyindole-carbazole co-polymer doped with NiO and MoO₃ were synthesized by in situ method using APS (Ammonium persulfate) as an oxidizing agent. The composites were prepared by mixing different wt% of NiO and MoO₃. Crystalline phases were noted from XRD (X-Ray Diffraction) patterns of both the samples. FTIR (Fourier Transform Infrared Spectroscopy) indicated strong interaction between pure copolymer and nano fillers. The optical absorption studies were carried out in a UV–Visible spectrometer. Addition of NiO or MoO₃ affected direct and indirect band gaps of copolymer composites. DC conductivity of the composites has been measured in the temperature range from 300 to 423 K. The conductivity of these nanocomposites is found to be less than the pure copolymer and it is increased with increase of concentration of NiO and MoO₃. The activation energy for conductivity has been determined by fitting Arrhenius expression to the conductivity data at high temperature. The activation energy of pure copolymer is determined to be less than that of the composites. In both the series of composites, activation energy decreased and conductivity increased with the increase of dopant content. Present composites are found to be highly conducting and have small activation energy compared to similar copolymers and their composites reported in the literature. The electrochemical behavior of the composites was studied using cyclic voltammetry and galvanostatic charge–discharge measurements in 1 M KOH electrolyte. Cyclic voltammogram (CV) studies confirmed synergic effect of the PInCz/NiO and PInCz/MoO₃ electrode. The maximum specific capacitance observed at the scan rate of 5 mV per second in 1 M KOH electrolyte was 155.19 Fg⁻¹ for PInCz-NiO 30 and 120 Fg⁻¹ for PInCz-Mo 15 which is higher than that of pure copolymer (15.45 Fg⁻¹). The parameters such as specific energy, specific power and columbic efficiency were determined. All the evaluated parameters indicated that the present copolymer composites are suitable for supercapacitor and electrode applications.