Innovative approach for the synthesis of graphene/MnO₂ nanocomposites and their electrochemical behavior

Abstract

Graphene-manganese dioxide composites were prepared using a simple one step method consisting of the electrochemical exfoliation of graphite in the presence of KMnO 4 in 0.1 м H 2 SO 4 at low temperature . In these conditions, the freshly exfoliated graphene sheets (EG) spontaneously reduce the permanganate ions and EG sheets decorated with MnO 2 nanoparticles are obtained. This was confirmed by scanning electron microscopy coupled with energy dispersive Xray spectroscopy, transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopies and thermogravimetric analysis. The electrochemical properties of EG@MnO 2 material were investigated and discussed. Electrodes based on the composite material exhibited enhanced capacitive performances compared to those made from pure graphene sheets. This was attributed to the synergic effect between the two components (graphene sheets and manganese dioxide nanoparticles) and to a larger porosity of the EG@MnO 2 electrode compared to the EG electrode. Additionally, over 91.6% of original capacitance was retained after 4000 cycles, indicating a very good cycling capability of the composite material. Remarkably, the composite electrode showed promising properties in aqueous medium by exhibiting a large and stable operating voltage up 2 V. The results presented in this article could serve as a guide for improving the energy density of supercapacitors in aqueous media.

One-Step Synthesis of Aminobenzoic Acid Functionalized Graphene Oxide by Electrochemical Exfoliation of Graphite for Oxygen Reduction to Hydrogen Peroxide and Supercapacitors

“…The electrochemical studies were carried out in 6 M KOH electrolyte and the scan rate varied between 5 and 100 mV s −1 [ 65 ]. The specific capacitance (Cs) of EGO/NF and EGO-COOHs/NF was evaluated from the cyclic voltammograms using the cathodic voltammetric charge (Q) integrated in the 0 to −1.15 V vs. SCE potential window by using Equation (5) [ 37 ]: where Cs is the specific capacitance (in F g −1 ), Q is the charge (in C), Δ V is the potential window (in V), and m is the mass of active material (in g).…”

“…Compared to the chemical methods (e.g., Hummers’ method: C/O ≈ 2) [ 29 ], the EGO materials obtained this way have a lower density of oxygenated functional groups (C/O > 4) [ 35 ] which could be of advantage for electrochemical applications [ 19 , 36 ]. In addition, the method also allows the preparation of EGO-based composites [ 37 , 38 ] or the surface modification of EGO with other molecules in a one-step process [ 39 , 40 ].…”