NiO nanoparticles on graphene nanosheets at different calcination temperatures as effective electrocatalysts for urea electro-oxidation in alkaline medium.

NiO nanoparticles were supported on graphene nanosheets (NiO/Gr) through coprecipitation step of Ni(OH)2 species, followed by calcination at different temperature values. The formed nanocomposites were characterized by employing X-ray diffraction (XRD) and transmission electron microscopy (TEM) to investigate their crystalline structure and morphology. The effect of varying the calcination temperature during the preparation of NiO/Gr electrocatalyst on some kinetic parameters in 0.5M NaOH solution was studied. The electrocatalytic activity of synthesized electrocatalysts was examined for urea electro-oxidation reaction in alkaline solution using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Among the fabricated NiO/Gr electrocatalysts, the one that was heated at 200°C exhibited the highest urea oxidation current density value with most stable performance for long time.