One-dimensional β-Ni(OH)2 nanostructures: Ionic liquid etching synthesis, formation mechanism, and application for electrochemical capacitors

A trifluoroacetate-functionalized task-specific ionic liquid has been introduced for the synthesis of beta-Ni (OH)(2) microspheres composed of nanowires. The cation C(16)mim(+) and the anion CF3COO- played synergetic roles on the formation of beta-Ni(OH)(2) microspheres composed of nanowires. The hydrolysis of anion CF3COO- provides controlled quantities of OH- ions for the formation of beta-Ni(OH)(2) microspheres composed of nanosheets. While the OH- supplies the precipitation of beta-Ni(OH)(2), the CF3COOH of the system increases continually. CF3COOH is responsible for the etching of beta-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, beta-Ni(OH)(2) microspheres composed of nanosheets evolved into beta-Ni(OH)(2) microspheres composed of nanowires. With the morphologies changed from nanosheets to nanowires, the BET surface areas of beta-Ni(OH)(2) have been significantly increased from 53 m(2) g(-1) to 249 m(2) g(-1) and the specific capacitance of beta-Ni(OH)(2) have also been increased from 412 F g(-1) to 1250 F g(-1).