Nickel-Hydroxide-Nanohexagon-Based High-Performance Electrodes for Supercapacitors: A Systematic Investigation on the Influence of Six Different Carbon Nanostructures

Transition-metal compounds (TMCs) such as oxides, hydroxides, and sulfides are well-known pseudocapacitive materials whose capacitance has been shown to improve by combining them with different carbon nanostructures (CNSs). Here, we report a systematic investigation on the influence of six different CNSs: single-walled carbon nanotubes (SWCNTs), functionalized and multiwalled carbon nanotubes, graphene oxide (GO), reduced GO (rGO), and graphene nanoplatelets on Ni(OH)(2) nanostructures, focusing on their electrochemical properties for potential use as electrode materials in supercapacitors. Uniformly distributed Ni(OH)(2) nanohexagons (approximately 30-35 nm in size) were found to be well attached to the surfaces of these CNSs. Among the studied CNSs, rGO appeared to be the best as its composite with Ni(OH)(2) exhibited the highest specific capacitance of 2306 F/g at 3 A/g along with 81.4% capacity retention after 5000 cycles. The SWCNT/Ni(OH)(2) composite showed the second best performance, with all other composites showing much lower performances. The lower charge transfer resistance and higher ion diffusion coefficient of the rGO/Ni(OH)(2) composite, compared to those of all other composites of Ni(OH)(2), have been identified as the reason for its improved performance. These results may find far-fetching significance in designing TMC-nanostructure-based electrodes modified with CNSs for supercapacitors.