NiCoS@NiMoO Core-Shell Heterostructure Nanotube Arrays Grown on Ni Foam as a Binder-Free Electrode Displayed High Electrochemical Performance with High Capacity.

Core-shell-structured system has been proved as one of the best architecture for clean energy products owing to its inherited superiorities from both the core and the shell part, which can provide better conductivity and high surface area. Herein, a hierarchical core-shell NiCoS@NiMoO heterostructure nanotube array on Ni foam (NF) (NiCoS@NiMoO/NF) has been successfully fabricated. Because of its novel heterostructure, the capacitive performance has been enhanced. A specific capacitance up to 2006 F g was obtained at a current density of 5 mA cm, which was far higher than that of pristine NiCoS nanotube arrays (about 1264 F g). More importantly, NiCoS@NiMoO/NF and active carbon (AC) were congregated as positive electrode and negative electrode in an asymmetric supercapacitor. As-fabricated NiCoS@NiMoO/NF//AC device has a good cyclic behavior with 78% capacitance retention over 2000 cycles, and exhibits a high energy density of 21.4 Wh kg and power density of 58 W kg at 2 mA cm. As displayed, the NiCoS@NiMoO/NF core-shell herterostructure holds great promise for supercapacitors in energy storage.