Effect of Particle Size on the Electrochemical Capacitance of a-Ni(OH)2 in Alkali Solutions

Effect of nanosized particles of α -Ni(OH)2 in enhancing the electrochemical capacitance as against the microsized particles of the same hydroxide is examined. Nanomaterial was synthesized by hydrothermal method while the micromaterial was prepared by the conventional co-precipitation method. Material characterization was done by XRD, TEM and BET surface area. Electrochemical characterization was carried out by cyclic voltammetry in alkali solutions. The BET surface areas of nano- and micro-sized α -Ni(OH)2 were shown to be directly proportional to their specific electrochemical capacitance (both faradic and non-faradic) as evident from the values of 20.9 m2g-1, 289.8 Fg-1 and 9.2 m2g-1, 133.6 Fg-1 respectively. Apart from inter-grain conduction, smaller particles increase the shift of conduction and valence band leading to a greater charge separation. An attempt to understand the particle size effect on the enhancement of electrochemical capacitance based on the volume and surface recombination of oppositely charged particles was made.