Compositional and Morphological Changes of Ordered PtxFey/C Oxygen Electroreduction Catalysts

Changes in the O2 reduction activity (ORR) and structure of carbon-supported catalysts upon electrochemical stress testing are investigated. Focus is placed on two alloy catalysts of nominal Pt3Fe/C and Pt3Fe2/C compositions. Energy dispersive X-ray spectroscopy (EDXS) spot and line analyses reveal a dependence of the Fe composition on the particle size, particularly for the two as-prepared catalysts. The catalyst particles are shown to have a Pt-enriched shell and a PtxFey alloy core. Larger (>approximate to 10nm) particles are shown to have a higher Fe content that approaches the nominal composition, which suggests that the smaller (