Facile synthesis and catalytic performance of Co3O4 nanosheets in situ formed on reduced graphene oxide modified Ni foam

A three-dimensional (3D) catalyst electrode of Co₃O₄ nanosheets in situ formed on reduced graphene oxide modified Ni foam (Co₃O₄/rGO@Ni foam) for H₂O₂ 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 Co₃O₄ nanosheets are synthesized intermixed with the rGO sheets through the second step. The Co₃O₄ nanosheets are made up of plentiful nanoparticles and there are many nanoholes among these nanoparticles which are beneficial for the sufficient contact between H₂O₂ and the catalyst. The morphology and phase composition of the Co₃O₄/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^-1 NaOH and 0.5 mol L^-1 H₂O₂, the reduction current density of H₂O₂ on the Co₃O₄/rGO@Ni foam electrode is 450 mA cm^-2 at -0.8 V which is much higher than that on Co₃O₄ 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 Co₃O₄ nanosheets improves the electron and ion transport ability of the electrode which leads to a good electrocatalytic activity and stability of the Co₃O₄/rGO@Ni foam electrode.

Oxidation of SO2 and NO by epoxy groups on graphene oxides: the role of the hydroxyl group

Hydroxyl groups facilitate the oxidation of SO₂ and NO by epoxy groups on carbon materials.