One-step cathodic electrodeposition of a cobalt hydroxide-graphene nanocomposite and its use as a high performance supercapacitor electrode material.

In this study, Co(OH)-reduced graphene oxide has been synthesized using a simple and rapid one-step cathodic electrodeposition method in a two electrode system at a constant current density on a stainless steel plate, and then characterized as a supercapacitive material on Ni foam. The composites were characterized by FT-IR, X-ray diffraction, scanning electron microscopy, and cyclic voltammetry using a galvanostatic charge/discharge test. The feeding ratios of the initial components for electrodeposition had a significant effect on the structure and electrochemical performance of the Co(OH)-reduced graphene oxide composite. The results show that the 1 : 4 (w/w) ratio of GO : CoCl·6HO was optimum and produced an intertwined composite structure with impressive supercapacitive behavior. The specific capacitance of the composite was measured to be 734 F g at a current density of 1 A g. Its rate capability was ∼78% at 20 A g and its capacitance retention was 95% after 1000 cycles of charge-discharge. Moreover, its average energy density and power density were calculated to be 60.6 W h kg and 3208 W kg, respectively. This green synthesis method enables a rapid and low-cost route for the large scale production of Co(OH)-reduced graphene oxide nanocomposite as an efficient supercapacitor material.