Facile synthesis of fibrous, mesoporous Ni.sub.1 - xO nanosponge supported on Ni foam for enhanced pseudocapacitor applications

Fibrous mesoporous Ni.sub.1 - xO nanosponge with excellent pseudocapacitive properties was synthesized by controlled calcination of [Ni(H.sub.2O).sub.4(4-nba).sub.2]·2H.sub.2O; a 4-nitrobenzoate (4-nba) coordinated compound. Control experiments with compounds such as [Ni(H.sub.2O).sub.6](4-nba).sub.2·2H.sub.2O; a non-coordinated 4-nba compound and the [Ni(H.sub.2O).sub.6]Cl.sub.2, without any 4-nba resulted in the formation of only agglomerated NiO nanoparticles.This proved the significance of 4-nba ligation with Ni.sup.2+ in [Ni(H.sub.2O).sub.4(4-nba).sub.2]·2H.sub.2O to produce highly porous, sponge-like nanostructures, without the need of hydrothermal or solvothermal treatment. The detailed structural characterization confirmed the formation of highly crystalline, mesoporous Ni.sub.1 - xO nanosponge.Further, the results obtained from electrochemical investigation by cyclic voltammetry and galvanostatic charge-discharge studies demonstrated that the fibrous, nanosponge-like Ni.sub.1 - xO exhibited good electrochemical properties with a high specific capacitance of 1236.84 Fg.sup.-1 at a current density of 1 Ag.sup.-1 and excellent capacitance retention of ~ 95% even after 10000 charge-discharge cycles at the current density of 6 Ag.sup.-1. The improved pseudocapacitive performance and extremely high cycling stability were attributed to extensive mesoporous network, effective distribution of electroactive sites and an improved electrode-electrolyte interaction due to fibrous and spongy nature of the material.The synthesis process is simple and scalable for industrial applications.