A trifluoroacetate-functionalized task-specific ionic liquid has been introduced for the synthesis of β-Ni(OH)2 microspheres composed of nanowires. The cation C16mim+ and the anion CF3COO− played synergetic roles on the formation of β-Ni(OH)2 microspheres composed of nanowires. The hydrolysis of anion CF3COO− provides controlled quantities of OH− ions for the formation of β-Ni(OH)2 microspheres composed of nanosheets. While the OH− supplies the precipitation of β-Ni(OH)2, the CF3COOH of the system increases continually. CF3COOH is responsible for the etching of β-Ni(OH)2 nanosheets. The conjunction of microsheets and nanowires, which are the intermediates during the ionic liquid etching process, present the obvious detail for the etching process. Via the ionic liquid etching process, β-Ni(OH)2 microspheres composed of nanosheets evolved into β-Ni(OH)2 microspheres composed of nanowires. With the morphologies changed from nanosheets to nanowires, the BET surface areas of β-Ni(OH)2 have been significantly increased from 53 m2 g−1 to 249 m2 g−1 and the specific capacitance of β-Ni(OH)2 have also been increased from 412 F g−1 to 1250 F g−1.
