Hierarchical NiCo2S4@NiCoP core-shell nanocolumn arrays on nickel foam as a binder-free supercapacitor electrode with enhanced electrochemical performance

A novel hierarchical core-shell nanocolumn array, with NiCo2S4 hollow nanowire (NiCo2S4 H-NW) as the core and NiCoP nanosheet (NiCoP NS) as the shell, has been directly synthesized on nickel foam (NF) as self-supported, binder-free electrode for high-performance supercapacitors. The morphological characterizations reveal that the diameter of NiCo2S4 H-NW core is similar to 100 nm and the diameter of single NiCo2S4@NiCoP core-shell nanocolumn is similar to 250 nm. Through a series of electrochemical tests and the analysis of charge storage kinetics, hierarchical NiCo2S4@NiCoP/NF electrode presents high areal specific capacitance of 5.98 F/cm(2) at 1 mA/cm(2), outstanding rate capability (70.29% capacitance retention with the current density increased from 1 to 50 mA/cm(2)) and superior cycling stability (92.94% of original capacity is retained after 5000 cycles at 10 mA/cm(2)). The prominent performance of NiCo2S4@NiCoP/NF electrode could be resulted from their unique hierarchical core-shell nanocolumn structure, which could offer abundant active sites near the interface for fast electrochemical reaction, and validly avoid the collapse of internal structure for the stability of whole structure in the repeated electrochemical measurement. The novel NiCo2S4@NiCoP/NF electrode offers a new method for future electrochemical energy storage devices with high-stability. (C) 2018 Elsevier Inc. All rights reserved.