Tailoring Kirkendall Effect of the KCu7S4 Microwires towards CuO@MnO2 Core-Shell Nanostructures for Supercapacitors

Abstract We construct uniform hierarchical CuO@MnO 2 core-shell structure via Kirkendall effect of KCu 7 S 4 microwires without any surfactants. KCu 7 S 4 microwires are synthesized by a hydrothermal method. Subsequently, MnO 2 nanosheets are grown on the CuO microtubes to form core–shell structures in the hydrothermal conditions. Based on time-dependent observation, a possible evolution mechanism for the hollow-core-shell structure is proposed. And the application of as-prepared CuO@MnO 2 as the electrode for supercapacitor has been investigated, the core-shell structure enable the electrode with relatively high capacitance (252.6 F g −1 (capacity: 70.2 mAh g −1 ) at the current density of 0.1 A g −1 , based on the total mass of CuO and MnO 2 ) and good stability (90.8% capacitance retention at 1 A g −1 after 1000 charge–discharge cycles).