A new protocol for the distribution of MnO₂ nanoparticles on rGO sheets and the resulting electrochemical performance

Highlights: • The role of KMnO₄ for the deposition of MnO₂ on rGO was studied. • The as-synthesized rGM-1 shows good stability and a high specific capacitance value (366 F/g). • rGM-1 effectively detects dopamine with a detection limit of 2.3 × 10⁻⁷ M. - Abstract: Herein, reduced graphene oxide (rGO)/MnO₂ hybrid materials were prepared via a direct redox reaction between MnCl₂ and KMnO₄ on reduced graphene oxide (rGO)_. A systematic study was carried out to understand the role of KMnO₄. The morphology and microstructure of the as-prepared composite was characterized using field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman Spectroscopy. Results indicate that the concentrations of KMnO₄ have a detrimental effect on the distribution of MnO₂ nanoparticles on rGO sheets and hence on electrochemical properties. The electrochemical capacitive behavior of the as-prepared composite was investigated using cyclic voltammetry (CV), galvanostatic charge discharge, and electrochemical impedance spectroscopy (EIS) in 1 M Na₂SO₄ aqueous electrolyte solution. At the optimum concentration of KMnO₄, the as-prepared rGM-1 composite shows a high specific capacitance of 366 F/g at a scan rate of 10 mV/s. The composite also exhibits good electrocatalytic activity towards the oxidation of dopamine (DA), exhibiting a low detection limit of 2.3 × 10⁻⁷ M with a wide linear range between 2.5 × 10⁻⁷ M and 2.30 × 10⁻⁴ M. Hence, the use of rGO/MnO₂ at an optimized concentration of KMnO₄ is a potential competitive candidate in supercapacitor and biosensor applications.