Hexagonal nanoplates of Ni(OH)(2) with a thickness of similar to 11 nm were synthesized by a simple hydrothermal method. The formation of Ni(OH)(2) phase was confirmed by XRD technique. TEM images revealed a stack of hexagonal nanosheets with average nanoplates size of similar to 62 nm. XPS results confirm the elemental compositions at the surface of Ni(OH)(2) which are in good agreement with XRD results. As we know, the properties of electrolyte affect the performance of supercapacitors. Therefore, the electrochemical performance of Ni(OH)(2) electrodes were investigated in various aqueous electrolyte solutions including 1M NaOH, 2M KOH, and 1M KOH mixed with 0.5M Na2SO4. The electrochemical results show that the Ni(OH)(2) electrode in 1M NaOH electrolyte reached the highest specific capacitance of 447 F/g at a current density of 1 A/g that was nearly two times higher than that in the 2M KOH electrolyte. This can be attributed to the smaller ionic radius of the Na+ ion and a higher intercalation/deintercalation rate of Na+ ions into the surface of the Ni(OH)(2) electrode. In addition, a coulombic efficiency of 94% was found in 1M NaOH at a current density of 10 A/g. The capacitance retention of the Ni(OH)(2) electrode in 1M NaOH was maintained at about 100% after 1000 cycles. The present work proves that the best performance of Ni(OH)(2) nanoplates was performed in the 1M NaOH electrolyte. (C) 2018 Elsevier B.V. All rights reserved.