Ultra-high specific capacitance of β-Ni(OH)2 monolayer nanosheets synthesized by an exfoliation-free sol-gel route

In this work, beta-Ni(OH)(2) monolayer nanosheets were prepared in benzyl alcohol by a facile exfoliation-free sol-gel route. The hydrolysis reaction of metal ions was started with the ring-opening reaction of epoxide. The in situ modification of benzyl alcohol molecules on the surface of secondary growth unit of hydroxide allowed the formation of beta-Ni(OH)(2) monolayer nanosheets and 100 % monolayer state of beta-Ni(OH)(2) in the resultant suspension. As proven in the electrochemical measurement, the maximum specific capacitance of 1735 F g(-1) was obtained at scan rate of 5 mV s(-1) within potential window of 0.6 V in 6 mol l(-1) KOH aqueous solution, which is equal to the theoretical value of beta-Ni(OH)(2). This high electrochemical performance is attributed to the complete exposure of every structure unit of beta-Ni(OH)(2) to electrolyte. This work demonstrates that monolayer nanosheets can generate from the brucite-type nickel hydroxide through this bottom-up strategy although it had been theoretically considered to be impossible.