Hydrothermally synthesized reduced graphene oxide and Sn doped manganese dioxide nanocomposites for supercapacitors and dopamine sensors

Abstract

?-MnO<inf>2</inf> nanowires and its nanocomposites (rGO-MnO<inf>2</inf> and Sn@rGO-MnO<inf>2</inf>) were synthesized by a facile hydrothermal technique. Two important electrochemical applications of nanocomposites, viz, electrodes for supercapacitor and sensors for a biomolecule, dopamine are reported. The prepared nanowires have been characterized by XRD, which reveals smaller crystallite size of rGO- MnO<inf>2</inf> composites compared to pristine MnO<inf>2</inf> and the trend is supported by BET analysis. The wrapping of MnO<inf>2</inf> NWs with rGO sheets increases the surface area, as well as, creates more dislocations at the interfaces. The correlation between physicochemical properties leads to an enhancement in the electrochemical performance of the materials. The as-fabricated Sn@rGO-MnO<inf>2</inf> supercapacitor electrode reveals superior performance. The specific capacitance of 139.05, 309.7 and 460.9 F/g at a scanning rate of 20 mV/s, in an aqueous Na<inf>2</inf>SO<inf>4</inf> solution (1 M) is obtained for MnO<inf>2</inf>, rGO-MnO<inf>2</inf> and Sn@rGO-MnO<inf>2</inf> respectively. Also, the reported nanocomposites show excellent performance towards detection of dopamine. Among ?-MnO<inf>2</inf>/GCE, rGO-MnO<inf>2</inf>/GCE and Sn@rGO-MnO<inf>2</inf>/GCE based sensors for Dopamine detection, rGO-MnO<inf>2</inf>/GCE sensor exhibits the highest sensitivity of 433.6 ?A/mM and broad linear range, whereas Sn@rGO-MnO<inf>2</inf> exhibits lower detection limit of 0.13 ?M. © 2017 Elsevier Ltd