A facile template-free synthetic strategy was proposed to prepare ultrathin mesoporous NiO nanosheets with a thickness of ca. 10 nm: precipitating hydroxides followed by calcinating process. Electrochemical data demonstrated that the ultrathin mesoporous NiO delivered a specific capacitance (SC) of 168 F g(-1) at 1 A g(-1), and a SC degradation of ca. 8% after 1000 continuous cycling at 4 A g(-1), which indicated that the ultrathin mesoporous NiO nanosheets were good candidates for supercapacitors application. (C) 2012 Elsevier Ltd. All rights reserved.