A 1-D/2-D hybrid nanostructured manganese cobaltite–graphene nanocomposite for electrochemical energy storage

Abstract

A unique 1-D/2-D hybrid nanostructured manganese cobaltite–graphene nanocomposite (GMC) was synthesized by a facile hydrothermal method. Successful composite formation was determined from a structural study like XRD and chemical analyses like FTIR and XPS. FESEM and TEM observations of the manganese cobaltite compound reveal the flower like architecture formed by the clusters of MnCo₂O_4.5 nanowires. By graphene incorporation a unique hybrid 1-D/2-D nanostructure was developed in the composite material. BET surface area measurement reveals the extremely high surface area of the composite material owing to its distinct morphology. CV measurements reveal the excellent redox reactivity of the prepared electrode materials. GMC exhibited a high specific capacitance of 890 F g⁻¹ which upon activation over cycling increases to 934 F g⁻¹. MnCo₂O_4.5 decorated graphene sheets in the composite provide high interfacial sites for the redox process, exceptional electrical support and mechanical strength during cycling. The manganese cobaltite–graphene composite was able to retain 95% of its original capacitance at the end of 2000 cycles. The small solution resistance value of 1.21 Ω illustrates the superior conductivity of the composite material. A symmetrical cell fabricated using the GMC electrode material exhibited a maximum specific capacitance of 189 F g⁻¹ at 5 mV s⁻¹ scan rate. Fast reaction kinetics displayed by the cell were due to the charge transfer speedway provided by the graphene sheets. The superior performance of the hybrid composite makes it a potential candidate for supercapacitor applications.