Chelating agent- and surfactant-assisted synthesis of manganese oxide/carbon nanotube composite for electrochemical capacitors

Different morphologies of manganese oxide/carbon nanotube (MnO2/CNT) composites were prepared using ethylenediaminetetraacetic acid (EDTA) or sodium dodecyl sulfate (SDS) as soft templates. Using EDTA, the resulting composite showed hierarchical structure, while an assembly of rod-like structures was obtained when SDS was used. The surface of CNT in the composites was covered with a layer of manganese oxide of 2–3 nm in thickness. The surface area was higher when EDTA was used in the synthesis (246 m2/g for EDTA route compared with 227 m2/g for SDS route), as is also the case for the specific capacitance (154 F/g based on cyclic voltammetry and 115 F/g based on galvanostatic charge/discharge for 95% MnO2 loading of EDTA route compared with 80.3 F/g based on cyclic voltammetry and 79.2 F/g based on galvanostatic charge/discharge for 80% MnO2 loading of SDS route). Overall, the MnO2/CNT composites showed good charge/discharge reversibility. Given these favorable properties along with the simplicity of the preparation, the MnO2/CNT/Ni-foam electrode can potentially be used in future large-scale development of the electrochemical capacitors.