Preparation and electrochemical analysis of graphene nanosheets/nickel hydroxide composite electrodes containing carbon nanotubes

A set of graphene nanosheets (GNS)/nickel hydroxide ($Ni(OH)_2$) composites were successfully synthesized by adding single-walled carbon nanotubes (SWCNT) to the composites with various weight contents. The mixed composites were prepared by ultrasonication and chemical precipitation. It is postulated that the SWCNT act as additives in the composites, preventing the aggregation of the graphene sheets. The structural characterization indicated that the $Ni(OH)_2$ nanoparticles were deposited on the surface of GNS, and the SWCNT were dispersed between or onto the graphene sheets. The electrochemical performance of the composites was investigated by changing the contents of the added SWCNT. The prepared $GNS/SWCNT/Ni(OH)_2$ composites exhibited the superior electrochemical performance, indicated by the large specific capacitance over $1000Fg^{-1}$ and excellent cycle performance over 2000 cycles. Among the prepared composites, the $GNS/Ni(OH)_2$ composite containing 20 wt.% SWCNT displayed the maximum specific capacitance with a value of $1149Fg^{-1}$ at a in 6 M KOH electrolyte. Moreover, 92% of the initial specific capacitance of the composite was maintained after 2000-cycle test. Based on these results, the composite is thought to be suitable candidate for supercapacitor electrode materials.