Oxygen Reduction Reaction Activity on Pt{111} Surface Alloys

Abstract

Abstract PtM overlayers (where M=Fe, Co or Ni) supported on Pt{111} are prepared via thermal annealing in either a nitrogen/water or hydrogen ambient of dilute aqueous droplets containing M Z+ cations directly attached to the electrode. Two different PtM phases are detected depending on the nature of the post‐annealing cooling environment. The first of these consists of small (<20 nm), closely packed microcrystals comprised of a central metallic core and a shell (several monolayers thick) of mixed metal oxides/hydroxides. The second type of PtM phase is prepared by cooling in a stream of hydrogen gas. Although this second phase also consists of numerous microcrystals covering the Pt{111} electrode surface, these are both flatter than before and moreover are entirely metallic in character. A positive shift in the onset of PtM oxide formation correlates with increased activity towards the oxygen reduction reaction (ORR), which we ascribe to the greater availability of platinum metallic sites under ORR conditions.