Facile Synthesis of Three Dimensional NiCo2O4@MnO2 Core-Shell Nanosheet Arrays and its Supercapacitive Performance

A novel hierarchical NiCo2O4@MnO2 core-shell nanosheet arrays hybrid composite/nickel foam integrated electrode for supercapacitors was designed and synthesized via a facile two-step hydrothermal method. XRD, SEM, EDS and TEM were carried out to investigate the composition and structure. The characterizations illustrated that the as-synthesized materials possessed hybrid "coreshell" nanostructure, the "core", which is the NiCo2O4 nanosheet with a thickness of 10 nm, was grown on the Ni foam via the first hydrothermal step; the "shell", which is the MnO2 nanosheets with a size of 40-70 nm and a thickness of 2 nm, was grown on the NiCo2O4 "core" nanosheet. Electrochemical characterizations indicated that the unique nano-architecture possesses excellent electrochemical properties, exhibiting a capacitance of 2.39 F cm(-2) as well as high cycling stability (7.4% loss after 2000 cycles), which is superior to the pristine NiCo2O4 nanosheet arrays. Our results clearly demonstrated that growing MnO2 nanosheets on NiCo2O4 nanosheets can substantially improve the capacitive performance of materials and ultimately increase the cycling stability of supercapacitors. (C) 2015 Elsevier Ltd. All rights reserved.