Controllable synthesis of graphene/NiCo2O4 three-dimensional mesoporous electrocatalysts for efficient methanol oxidation reaction

A series of graphene (GE)/NiCo2O4 electrocatalysts with different morphological structures were controllably prepared in this study and their methanol oxidation electrocatalytic properties were also detailedly investigated. The morphology, structure and composition of GE/NiCo2O4 wese investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrocatalytic properties of GE/NiCo2O4 were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The testing results show that the GE/NiCo2O4 has a very high electrocatalytic activity and stability for methanol oxidation reaction. At a scanning rate of 50 mV/s, the current density at 1.45 V of GE/NiCo2O4 is 239 A/g, which is much higher than that (34 A/g) of NiCo2O4. The GE/NiCo2O4 also shows a better electrochemical stability compared with the NiCo2O4. The excellent electrochemical properties of GE/NiCo2O4 can be attributed to its three-dimensional structure with high surface area, mesoporous structure, high conductivity as well as the fast ion/electron transport rates. (C) 2017 Elsevier Ltd. All rights reserved.