Herein, cobalt oxide (Co₃O₄)-decorated reduced graphene oxide (rGO)-based nanoelectrodes were fabricated by the chemical reduction method using hydrazine hydrate. It showed enhanced electrocatalytic activity for oxygen evolution (water oxidation) reactions (OER) in an alkaline medium. These as-synthesized materials were characterized by X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, energy dispersive analysis of X-ray (EDAX), Raman spectroscopy and transmission electron microscopy (TEM). The XRD studies confirmed that Co₃O₄ had a cubic spinal structure and morphological studies based on TEM analysis showed that Co₃O₄ existed with ∼5 nm-thick chain-like nanostructures that decorated rGO. This Co₃O₄-modified reduced graphene oxide (Co₃O₄–rGO) electrocatalyst was found to be extraordinarily active towards oxygen evolution reactions (OER) and is one of the complex reactions of water splitting technique. This was further confirmed by an ultra-low onset potential of 1.38 V vs. RHE with a high current density of 10 mA mg⁻¹ of Co₃O₄ loading (calculated from TGA) at the constant potential of 1.50 V vs. RHE. The enhancement factor of Co₃O₄–rGO = 2000 was almost 3.25 times higher compared with that of Co₃O₄ = 600 under similar electrolytic conditions probably due to the synergetic co-operative interactions at modified interfaces. Chronoamperometric (i–t) and electrochemical impedance spectroscopic (EIS) measurements demonstrated higher current/potential stability and lower charge transfer resistance, respectively, for Co₃O₄–rGO compared with those of rGO and Co₃O₄ towards the water oxidation reaction.