The increasing consumption of fossils fuel accompanied by related carbon emissions and complex set of issues associated with the generation and use of electricity has raised an urgent need for reliable, renewable and sustainable energy alternatives [1]. Nanotechnology and the production of nanostructured materials has driven the rapid growth in the research of carbon nanomaterials as energy storage materials for supercapacitor (SCs) applications. Among several carbon nanomaterials explored for SCs, graphene has shown to be the leading carbon nanomaterial, due to its intriguing properties such as highly tunable surface area, outstanding electrical conductivity, good chemical stability and excellent mechanical behavior [2]. Due to challenges in the bulk synthesis of graphene, reduced graphene oxide (rGO) has been opted as the preferred choice for the development of SC devices. Transition metal oxides also gained much interest in various research industries as materials for SCs applications. Among transition metal oxides, manganese oxide, Mn_xO_y, appeared to be the promising electrode material due to its interesting properties such as cost effectiveness, high theoretical specific capacitance, high theoretical surface area (≥ 1370 m² g^-1), and excellent electrochemical reversibility. However, the poor conductivity of manganese oxide restricts its progress in SC applications [2, 3]. Therefore, great attention has been devoted to the improvement of the electronic properties of manganese oxides-based electrode materials by decorating them on highly conductive carbon-based nanomaterials. Although intensive study has been done on carbon nanomaterials integrated with Mn_xO_y for pseudocapacitors, there is still less literature on the use of Mn₃O₄ nanoparticles decorated on carbon materials for application in SCs

This work presents a hydrothermal synthesis of the nitrogen-doped reduced graphene oxide/hausmannite manganese oxide (N-rGO/Mn₃O₄) nanohybrid which showed a great electrochemical performance such as high specific capacitance of 345 F g^-1 and a maximum of specific energy of 12.0 Wh kg^-1 (current density: 0.1 A g⁻¹), and a maximum specific power of 22.5 kW kg^-1 (current density: 10.0 A g⁻¹) in a symmetric configuration. The nanohybrid further showed excellent supercapacitor performance in an asymmetric configuration, with the maximum specific energy and power reaching 34.6 Wh kg⁻¹ (0.1 A g⁻¹) and 14.01 kW kg⁻¹ (10.0 A g⁻¹) respectively. The results obtained affirm the use of N-rGO/Mn₃O₄ as a potential electrode material for high energy and power supercapacitor devices that can be commercially competitive to that of rechargeable batteries.

References

[1] P. Simon, Y. Gogotsi, Materials for electrochemical capacitors., Nat. Mater. 7 (2008) 845

[2] K. Xie, B. Wei, Nanomaterials for stretchable energy storage and conversion devices, Nanosci. Technol. (2016) 159

[3] K. Makgopa, K. Raju, P.M. Ejikeme, K.I. Ozoemena, High-performance Mn3O4/onion-like carbon (OLC) nanohybrid pseudocapacitor: Unravelling the intrinsic properties of OLC against other carbon supports, Carbon 117 (2017) 20