Monodispersed plum candy-like MnO2 nanosheets-decorated NiO nanostructures for supercapacitors

Abstract

A simple, template-free strategy without organic dispersant or capping agent is developed to synthesize a novel monodispersed NiO@MnO2 nanostructure as powdery electrode for supercapacitors. The first step in the synthesis involves the NaOH mediated evolution of Ni(OH)2 nanosheets, further leading to the formation of NiO structure with different features. After calcination in air, via self-decomposition of KMnO4 solution in a lower concentration, MnO2 nanoflakes are elaborately grafted along the petal of NiO microspheres to form core–shell nanostructures, enhancing specific surface area and homogenizing pore-size distribution of NiO@MnO2. Owing to the hierarchical core–shell heterostructure configuration with rich mesoporous and synergetic contribution from the NiO core and MnO2 shell, NiO@MnO2 exhibits relatively high specific capacitance and good rate capability, which are better than those of the individual NiO structure. The enhanced performance of the NiO@MnO2 core–shell structure demonstrates that integrated spherical structure constructed by two high capacitance materials is a rational design, which holds definite potential in supercapacitors and other kinds of energy storage systems.