NiMoO4-modified MnO2 hybrid nanostructures on nickel foam: electrochemical performance and supercapacitor applications

Abstract

A novel self-supported electrode of NiMoO₄-modified MnO₂ hybrid nanostructures on nickel foam has been designed and synthesized using a combination of hydrothermal syntheses. Based on the morphology, a possible mechanism that the surface modification of NiMoO₄ not only prevents the MnO₂ from dissolving in an alkaline electrolyte of KOH but also improves the capacity is proposed. Therefore, this electrode manifests a satisfying capacitance of 2525 F g⁻¹ (within a potential range of −0.2–0.6 V at a current density of 0.5 A g⁻¹), outstanding rate capability and excellent cycling stability. The reason that the hybrid NiMoO₄-modified MnO₂ electrode has excellent comprehensive performance is not only the coupling effect which between NiMoO₄ and MnO₂ but also the semiconductor surface recombination effect which improved the electrical conductivity. Moreover, an asymmetric supercapacitor has been assembled, where the hybrid NiMoO₄-modified MnO₂ and activated carbon act as the positive and negative electrodes, respectively, and a maximum specific capacitance of 135 F g⁻¹ is demonstrated within a cell voltage between 0 and 1.6 V at a current density of 0.5 A g⁻¹; thus, the supercapacitor exhibits a high energy density and stable power characteristics.