Improved oxygen reduction activity on Pt3Ni(111) via increased surface site availability

The slow rate of the oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cell ( PEMFC) is the main limitation for automotive applications. We demonstrated that the Pt3Ni( 111) surface is 10-fold more active for the ORR than the corresponding Pt(111) surface and 90-fold more active than the current state-of-the- art Pt/C catalysts for PEMFC. The Pt3Ni( 111) surface has an unusual electronic structure (d-band center position) and arrangement of surface atoms in the near-surface region. Under operating conditions relevant to fuel cells, its near-surface layer exhibits a highly structured compositional oscillation in the outermost and third layers, which are Pt-rich, and in the second atomic layer, which is Ni-rich. The weak interaction between the Pt surface atoms and nonreactive oxygenated species increases the number of active sites for O-2 adsorption.