Amalgamation of MnWO4 nanorods with amorphous carbon nanotubes for highly stabilized energy efficient supercapacitor electrodes

Abstract

Enhanced electrochemical performance of supercapacitors can be achieved through optimal hybridization of electroactive nanomaterials, as it effectively increases the overall surface area and ensures greater electrolyte–electrode interaction. This work reports the realization of a manganese tungstate and amorphous carbon nanotube (MnWO₄–aCNT) hybrid and its utilization as the electrodes for a solid-state asymmetric supercapacitor. Large-scale synthesis of aCNTs was carried out via an economical solid-state reaction at low temperature and the walls of these nanotubes were decorated with MnWO₄ nanorods via a surfactant-free in situ hydrothermal process. The as-fabricated electrode based on this hybrid over nickel foam delivered a high specific capacitance of 542.18 F g⁻¹ at a scan rate of 2 mV s⁻¹, which is much superior to the values of the structural units separately. This MnWO₄-aCNT based electrode showed a high-rate capacity with ∼100% capacitance retention and a coulombic efficiency of ∼100% even after operation for 15 000 cycles. A solid-state asymmetric supercapacitor based on this hybrid attained an energy density of 5.6 W h kg⁻¹ and a power density as high as 893.6 W kg⁻¹. Significantly enhanced electrochemical behaviour registered from the hybrid sample is accounted for by its enhanced surface area and thereby greater number of redox reaction sites along with the positive synergetic effect of the building blocks. This study unlocks further exploration possibilities with other types of aCNT-based hybrid materials for the development of highly stable, non-toxic and cost-effective sustainable energy storage systems.