Electroreduction of oxygen on sputter-deposited Pd nanolayers on multi-walled carbon nanotubes

The electrochemical reduction of oxygen on Pd nanoparticle/multi-walled carbon nanotube (PdNP/MWCNT) catalysts was studied in acid and alkaline solutions using the rotating disk electrode (RDE) method. The PdNP/MWCNT nanocomposites were prepared by sputter-deposition of palladium onto the surface of MWCNTs. The surface morphology of the PdNP/MWCNT composites was characterised by scanning electron microscopy (SEM). The SEM images showed the formation of Pd nanolayers around MWCNTs. The RDE results revealed a high electrocatalytic activity of PdNP/MWCNT catalysts towards the oxygen reduction reaction (ORR) in alkaline media. Two Tafel regions with different slope can be distinguished. At low overpotentials the Tafel slope is close to −60 mV dec−1 and at higher current densities the slope is approximately −100 mV dec−1. The PdNP/MWCNT composite is a promising material to be used as a cathode catalyst for alkaline membrane fuel cells.