Composites based on poly(o-toluidine) and reduced graphene oxide: from synthesis to optical characterization and potential applications in the energy storage field

Abstract

Three methods were used to prepare poly(ortho-toluidine)/reduced graphene oxide (POT/RGO) composites: (i) the interaction of the two constituents in the solid state, (ii) the chemical polymerization of ortho-toluidine (OT) in the presence of the RGO sheets, and (iii) the electrochemical polymerization of OT in the presence of the RGO sheets. Combining the results of Raman scattering, FTIR spectroscopy, and X-ray photoelectron spectroscopy, we demonstrated the following: (i) the interaction of POT with RGO in the solid state leads to the non-covalent functionalization of RGO with POT; (ii) the chemical polymerization of OT in the presence of RGO results in the covalent functionalization of RGO with POT in emeraldine base (EB) and leucoemeraldine salt (LS) and (iii) the electrochemical polymerization of OT assisted by RGO sheets leads to the covalent functionalization of RGO with POT-LS and POT-emeraldine salt (ES). The cyclic voltammetry (CV) studies indicated that the values for the voltammetric output currents of the POT/RGO composites are superior to those reported for POT. Electrochemical studies demonstrated a (a) battery-type behavior in the case of the electrodes based on POT-ES and POT/RGO composites prepared by chemical and electrochemical polymerizations and a (b) pseudocapacitive behavior for the electrodes based on POT-EB and composites prepared by the interaction of POT-EB with RGO in the solid state. High capacitance values of up to 1197.23 and 1524.62 mF cm⁻² were obtained for the symmetrical supercapacitors based on the electrodes containing the POT/RGO composites prepared by chemical and electrochemical polymerization, respectively, of OT in the presence of RGO sheets.