Controlling the aspect ratio and electrocatalytic properties of nickel cobaltite nanorods

Abstract

NiCo₂O₄ nanorods (assembled with small nanoparticles) with different aspect ratios were synthesized through a surfactant mediated reverse micellar route. Anisotropy of the nickel cobaltite nanorods was retained after calcination of nickel cobalt oxalate precursors. A high aspect ratio (∼12) of the NiCo₂O₄ nanorods was obtained by using a cationic surfactant (CTAB) while a non-ionic surfactant (Tergitol) led to the formation of a much lower aspect ratio (∼5) of the nanorods. These nanorods could potentially be used as anodic electrocatalysts for the oxygen evolution reaction. Due to having a high surface roughness, nanorods assembled with the smallest particles, ∼5–10 nm in diameter (surface area ∼158 m² g⁻¹), show a high current density of ∼140 mA cm⁻² with a low onset potential of ∼0.31 V (at 0.9 V) towards the oxygen evolution reaction and the values of current density is significantly higher than earlier reports.