Enhancing hydrothermal formation of α-MnO2 nanoneedles over nanographite structures obtained by electrochemical exfoliation

Design and production of α-MnO2 structures over carbonaceous material is considered as potential strategy for improving electrochemical performance of supercapacitors. This study describes the development of a simple method for hydrothermal synthesis of a composite material with directly anchoring α-MnO2 over a nanographite matrix. The nanographite matrix was obtained by electrochemical exfoliation of graphite rods (from depleted Leclanche batteries) and characterized by X-ray diffraction (XRD), Raman spectroscopy and field emission gun-scanning electron microscopy (FEG-SEM). The obtained results indicated that nanographite produced presented low levels of defects with a mild oxidized surface. This nanographite was used as anchoring base for producing MnO2 particles, using the developed hydrothermal procedure. For paralleling, pure MnO2 particles were also produced in same conditions. The prepared materials were characterized by XRD, Raman spectroscopy and FEG-SEM. XRD patterns proved formation of α-MnO2 for pure and composite materials. Morphological characterization indicated the formation of nanoneedles in both situations; however, in the composite the α-MnO2 was produced as smaller nanoneedles homogeneously spread over the nanographite surface. Raman spectra showed that the desired composition was achieved. Electrochemical characterization showed that the adopted strategy was successful in producing materials with improved pseudocapacitive performance, high reversibility, presenting specific capacitance of 279.8 F g−1 and coulombic efficiency of 99.7%.