Growing highly capacitive nano-Ni(OH)2 on freshly cut graphite electrode by electrochemically enhanced self-assembly

•Nano-Ni(OH)2 grows spontaneously on a freshly cut graphite electrode.•The composite shows a specific capacitance of 1850 F g−1 in aqueous solution.•The self-assembly process is supposedly due to the special interfacial property.•The growth of Ni(OH)2 can be enhanced by cathodic polarization.

Highly capacitive nano-Ni(OH)2 spontaneously grows on the surface of a freshly cut graphite electrode (FGE) dipped in a NiCl2 aqueous solution. The obtained nano-Ni(OH)2/FGE composite electrode, free of binders and other additives, shows a high specific capacitance of ~1850 F g−1 in 30 wt% KOH solution. Both capacity and cycling stability of the Ni(OH)2/FGE can be improved by electrochemical (cathodic) polarization enhanced self-assembling. The nano-Ni(OH)2 was supposed to be self-assembled on FGE, where a doped nano-scale active water film incurs the formation of Ni(OH)2. The results described here provide a facile and low-cost pathway to produce highly capacitive Ni(OH)2 and Ni(OH)2/FGE composite electrode used for energy storage.