Template-free synthesis of hierarchical hollow NiSX microspheres for supercapacitor

Hierarchical nickel sulfide (NiSX) hollow microspheres can be successfully synthesized with a template free method using alpha-Ni(OH)(2) microspheres as a precursor by calcination and sulfidation. The intermediate Ni hollow spheres, formed at different calcination temperatures (300 degrees C and 400 degrees C) under H-2/N-2 atmosphere, can be easily transformed into NiSX with similar morphology and mixed phases of Ni3S2 and NiS during the followed sulfidation process. The formation processes for the hollow structure of NiSX are also discussed in this work. Particularly, the NiSX prepared from Ni intermediate spheres at 300 degrees C show a high specific capacity of 153.6 mAh g(-1) at 0.5 A g(-1) at high mass loading due to its small crystal size, hierarchically porous structure and high electrical conductivity. A hybrid capacitor was assembled by using it as positive electrode and activated carbon as negative electrode to examine their practical applications in a full-cell configuration. The hybrid capacitor exhibited excellent comprehensive performances in 1.6 V. The hybrid capacitor also showed good cycling stability, with 81.25% of the initial specific capacitance after 1000 cycles at 2 A g(-1). Above results indicate the great potential of the NiSX hollow spheres as a promising electrode material for supercapacitor applications. (C) 2017 Elsevier Inc. All rights reserved.