MOF-derived hollow double-shelled NiO nanospheres for high-performance supercapacitors

Hollow double-shelled NiO nanospheres have been successfully prepared by the calcination of Ni-based MOF precursor at proper temperatures. The morphology and phase structure of NiO samples were characterized by SEM, TEM, XRD and FTIR. Electrochemical studies indicate that NiO nanospheres obtained under different conditions have distinct electrochemical performances. Hollow double-shelled NiO nanospheres calcined at 400 degrees C (N400) exhibit the best charge storage with a specific capacitance of 473 F g(-1) at the current density of 0.5 A g(-1) and with 94% capacitance retention even after 3000 cycling tests. For this merits, the N400//active carbon (AC) asymmetric supercapacitor (ASC) was assembled to examine the practical application of the N400 sample, which presents high energy density of 21.4 Wh kg(-1) at power density of 375.8 W kg(-1). Particularly, the N400//AC ASC exhibits outstanding cycling stability, and its capacitance retention can still reach up to 92.3% after 3000 cycles. These results indicate that the N400 sample is a promising electroactive candidate for supercapacitors. (C) 2017 Elsevier B. V. All rights reserved.