In-situ growth of novel CNTs-graphene hybrid structure on Ni-silica nanocomposites by CVD method for oxygen evolution reaction

Carbon nanostructures are ideal materials for electrochemical reactions like oxygen evolution reaction (OER) due to excellent electrical conductivity, resistance to strong acidic as well as basic conditions and conductive support material for transition metals. In this work we have synthesized multiwalled carbon nanotubes MWCNTs along with graphene growth in-situ by CVD method at 650 °C on nickel-silica nanocomposites for OER in alkaline medium. After removal of silica, our material exhibited comparable OER performance with that of commercial Iridium supported carbon i.e. Ir/C (20 wt % Ir) electrocatalyst. The OER performance is attributed to the defective nature of MWCNTs in the form of surface discontinuities found on rolled graphene layers of carbon nanotubes along with MWCNTs-graphene interfaces which presumably contain dangling bonds as active sites for OER. The overpotential at current density of 10 mA/cm² exhibited by MWCNTs-graphene hybrid carbon nanostructured material was 310 mV in 1 M KOH solution at scan rate of 5 mV/s while commercial Ir/C material revealed overpotential of 305 mV under similar conditions.