NiCo<inf>2</inf>O<inf>4</inf> hexagonal nanoplates anchored on reduced graphene oxide sheets with enhanced electrocatalytic activity and stability for methanol and water oxidation

We have synthesized highly active NiCo2O4-reduced graphene oxide (NiCo2O4- rGO) hybrid material as non-precious bi-functional electrocatalyst for effective oxidation of methanol and water. The hexagonal nanoplates of NiCo2O4 are grown on rGO sheets by two-step solution phase method. The physiochemical properties of NiCo2O4-rGO hybrid composite have been evaluated by powder X-ray diffraction, Raman spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and nitrogen sorption measurements. The electrocatalytic activity for methanol and water oxidation on NiCo2O4-rGO, NiCo2O4 and rGO electrodes is tested under alkaline conditions. Results show that the NiCo2O4-rGO hybrid shows higher methanol oxidation peak current density of 16.6 mA cm−2 and lower onset potential (∼256 mV) in methanol oxidation. Likewise, in water oxidation it shows earlier onset overpotential (∼300 mV) and high current density (∼75 mA cm−2) as well as smaller overpotential of ∼390 mV is required to reach a current density of 10 mA cm−2. In addition, the hybrid NiCo2O4-rGO electrode shows excellent catalytic stability in both methanol and water oxidation reactions. The improved electrocatalytic activity of NiCo2O4-rGO is attributed to resilient synergistic effects between NiCo2O4 and rGO sheets.