Rational synthesis of hierarchically porous NiO hollow spheres and their supercapacitor application

Hierarchically porous-structured hollow spheres with the shell composed of nanosized building blocks are of great importance to the next-generation of electrochemical devices. We present a powerful chemical bath deposition method for the fabrication of hierarchically porous NiO hollow spheres composed of nanoflakes with thicknesses of similar to 10 nm. A plausible mechanism is proposed to explain the formation of the NiO hollow spheres. Supercapacitor electrodes based on the NiO hollow spheres are characterized. The NiO hollow spheres exhibit a specific capacitance of 346 F g(-1) at 1 A g(-1) after 2000 cycles and an excellent cycling stability, owing to the unique hollow-sphere architecture providing fast ion/electron transfer. Our growth approach may offer a new strategy for the synthesis of other transition metal oxides hollow spheres for applications in electrochemical energy storage, catalysis, and gas sensing. (C) 2012 Elsevier B.V. All rights reserved.