Highly active nitrogen-doped few-layer graphene/carbon nanotube composite electrocatalyst for oxygen reduction reaction in alkaline media

In this work the electrocatalysis of oxygen reduction on nitrogen-doped few-layer graphene/multi-walled carbon nanotube (FLG/MWCNT) composite catalyst has been investigated. These composite materials were prepared from different nitrogen precursors, acid-treated MWCNTs and graphene oxide (GO), which was synthesised from graphite by the modified Hummers' method. Urea and dicyandiamide were used as nitrogen precursors and the doping was achieved by pyrolysing the mixture of GO and MWCNTs in the presence of these nitrogen-containing compounds at 800 °C. The N-doped composite catalyst samples were characterised by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, the latter method revealed successful nitrogen doping. The oxygen reduction reaction (ORR) was studied in 0.1 M KOH on glassy carbon electrodes modified with N-doped FLG/MWCNT electrocatalysts employing the rotating disk electrode (RDE) method. The RDE results indicated that these metal-free nitrogen-doped nanocarbon catalysts possess remarkable electrocatalytic activity towards the ORR in alkaline media similar to that of commercial Pt/C catalyst. The results obtained in this work are particularly important for the development of non-Pt cathode catalysts for alkaline membrane fuel cells.