One-pot green synthesis of graphene oxide/MnO2/polyaniline nanocomposites applied in aqueous and neutral supercapacitors and sensors

Abstract

Different binary and ternary nanocomposites among graphene oxide (GO), manganese dioxide (MnO2) nanoparticles and polyaniline (Pani) were synthesized in aqueous medium and room temperature using KMnO4 as oxidizing agent for aniline and precursor for MnO2 in the presence of GO. The ratio between the constituents was directly dependent on the HCl concentration and aniline amount used in the synthesis. Indeed, the lower the acid concentration, the greater the MnO2 ratio (∼65% using 0.01 mol L−1 HCl). The globular morphology of Pani presented higher degrees of polymerization and larger size of spheres according to the increase of acid concentration. MnO2 nanoparticles exhibited a birnessite structure with a mean size of ∼ 1 nm well spread throughout the polymer matrix. The multifunctionality of the nanocomposites was evaluated in neutral aqueous solutions as supercapacitors and electrochemical sensors to H2O2. In both cases, the nanocomposites with the highest MnO2 proportion exhibited the best performances, reaching capacitances as high as ∼ 150 F g−1 with 68.2% of stability under 500 charge–discharge cycles and limit of detection as low as 3.03 ± 0.22 μmol L−1 for the ternary nanocomposites.