Facile synthesis and catalytic performance of CoO nanosheets in situ formed on reduced graphene oxide modified Ni foam.

A three-dimensional (3D) catalyst electrode of CoO nanosheets in situ formed on reduced graphene oxide modified Ni foam (CoO/rGO@Ni foam) for HO electroreduction is prepared by a two-step hydrothermal method. In the first step, graphene oxide sheets are reduced and formed on the skeleton of Ni foam and CoO nanosheets are synthesized intermixed with the rGO sheets through the second step. The CoO nanosheets are made up of plentiful nanoparticles and there are many nanoholes among these nanoparticles which are beneficial for the sufficient contact between HO and the catalyst. The morphology and phase composition of the CoO/rGO@Ni foam electrode are studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of the as-prepared electrode is investigated by cyclic voltammetry (CV) and chronoamperometry (CA). From the results, it can be seen that in 2 mol L NaOH and 0.5 mol L HO, the reduction current density of HO on the CoO/rGO@Ni foam electrode is 450 mA cm at -0.8 V which is much higher than that on CoO directly supported on Ni foam. This obvious increase of the current density can be attributed to the increase of the surface area of the electrode after the addition of rGO. Also, the interpenetration of rGO and CoO nanosheets improves the electron and ion transport ability of the electrode which leads to a good electrocatalytic activity and stability of the CoO/rGO@Ni foam electrode.