Surface engineering of PdFe ordered intermetallics for efficient oxygen reduction electrocatalysis

The catalytic performance of electrocatalyst is straightforwardly determined by their surface and/or near-surface atomic configuration. Hence, uncovering the relationship between surface structure and catalytic performance at atomic scale is imperative for the rational design of proton exchange membrane fuel cells (PEMFCs) electrocatalysts. In this work, firstly, we present a general method for the preparation of surface clean and structurally ordered PdFe intermetallics (o-PdFe). Subsequently, to further improve their performance towards oxygen reduction reaction (ORR) in acid medium, a mild yet effective surface treatment process is conducted to fabricate ultra-low content of Pt decorated porous PdFe intermetallics (p-o-PdFe@Pt). The p-o-PdFe@Pt are witnessed 28 fold improvement in ORR activity than that on Pt/C and only 15% attenuation after 10,000 cycles. Finally, the promotion mechanism of p-o-PdFe@Pt for ORR is investigated via chemically sensitive 3D tomography technique to visualize their structure and composition evolution. It reveals that the gradual Pt rearrangement on the surface plays a pivotal role in enhancing the ORR performance. This work not only demonstrates a strategy for the fabrication of Pt decorated porous PdFe intermetallics, but also provides a new insight for the promotion mechanism of elctrocatalysts.