Facile synthesis of fibrous, mesoporous Ni sub(1-x)O nanosponge supported on Ni foam for enhanced pseudocapacitor applications

Abstract

Fibrous mesoporous Ni sub(1-x)O nanosponge with excellent pseudocapacitive properties was synthesized by controlled calcination of [Ni(H sub(2)O) sub(4) (4-nba) sub(2)].2H sub(2)O; a 4-nitrobenzoate (4-nba) coordinated compound. Control experiments with compounds such as [Ni(H sub(2)O) sub(6)](4-nba) sub(2).2H sub(2)O; a non-coordinated 4-nba compound and the [Ni(H sub(2)O) 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(2)O) sub(4)(4-nba) sib(2)].2H sub(2)O 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-x) O 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-x)O 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?approx.?95 percent 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.