In-situ hydrothermal synthesis of δ-MnO2/soybean pod carbon and its high performance application on supercapacitor

Abstract

Manganese dioxide, with large theoretical capacitance, is a promising electrode material of supercapacitors, while the poor cyclic stability limits its practical application. Traditional carbon loading using graphene or carbon nanotube is still unsatisfactory due to high cost. In this study, renewable waste of soybean pod was utilized as the precursor of carbon matrix. The MnO2/soybean pod carbon composite material was synthesized by a one-step in-situ hydrothermal method. The composite material displayed natural tube structure, and its surface was sheathed with numerous δ-MnO2 nanorods. After carbon loading, the MnO2/soybean pod carbon delivered a superior specific capacitance of 530 F g–1 in Na2SO4 electrolyte as the three-electrode system, 46% higher than 362 F g–1 of pristine MnO2. Using the symmetrical two-electrode system, such the composite electrode further revealed high capacitance retention of 91% and reversible capacitance of 189 F g–1 after 6000 charge/discharge cycles. It demonstrates that this work develops a scalable strategy to obtain high-performance and cost-effective electrode material of next-generation supercapacitors.