Hierarchical structures composed of MnCo2O4@MnO2 core–shell nanowire arrays with enhanced supercapacitor properties

Abstract

In this paper, hierarchical MnCo₂O₄@MnO₂ core–shell nanowire arrays (MnCo₂O₄@MnO₂ NWAs) with mesoporous and large surface area are synthesized on 3D nickel foam via a facile, two-step hydrothermal approach without any adscititious surfactant and binder. The electrode architecture takes advantage of the synergistic effects contributed from both the porous MnCo₂O₄ nanowire core and the MnO₂ shell layer. The fabricated MnCo₂O₄@MnO₂ NWA electrode for supercapacitors in aqueous electrolyte exhibits a significantly enhanced specific capacitance (858 F g⁻¹ at 1 A g⁻¹), high energy density (36.0 Wh kg⁻¹ at 252 W kg⁻¹) and long-life cycling stability (retaining 88% of the initial capacitance after 5000 cycles). Then, a symmetrical supercapacitor is fabricated by assembling two MnCo₂O₄@MnO₂ NWA-based electrodes, which shows a high specific capacitance of 678 F g⁻¹ at 1 A g⁻¹ and a high energy density of 135.6 Wh kg⁻¹ at 513 W kg⁻¹. Thereby, the hierarchical core–shell MnCo₂O₄@MnO₂ NWAs are very promising as next generation high-performance long-life cycling supercapacitors.