Oxygen Electroreduction Activity and X-Ray Photoelectron Spectroscopy of Platinum and Early Transition Metal Alloys

The oxygen reduction reaction (ORR) was studied experimentally on sputter-cleaned, polycrystalline electrodes of Pt3Y, Pt5Y, Pt2Y, Pt3Sc, Pt3Hf, Pt3Zr and Pt under conditions relevant for low-temperature fuel cells. The surfaces were characterised in situ by means of electrochemical methods and ex situ under ultrahigh vacuum conditions. The ORR activity was established in an electrochemical cell containing 0.1 M HClO4 by use of a rotating ring disk electrode assembly. The surface composition was characterised before and after the electrochemical measurements by using angle-resolved X-ray photoelectron spectroscopy. The ORR activity of the electrodes increased in the following order: Pt2Y approximate to Pt3Zr approximate to Pt approximate to<< Pt5Y