Au Nanowires@Pd-Polyethylenimine Nanohybrids as Highly Active and Methanol-Tolerant Electrocatalysts toward Oxygen Reduction Reaction in Alkaline Media

Optimizing the shape, structure, and interface of noble metal bimetallic nanostructures significantly improves their catalytic properties. Recently, Au@Pd core-shell bimetallic nanostructures have attracted considerable interest for fuel cell applications. Regrettably, most of the research mainly focuses on the morphological and structural control whereas interfacial control is neglected. In this work, polyethylenimine (PEI) functionalized Au nanowires@Pd core-shell bimetallic nanohybrids (Au-NWs@Pd@PEI) are synthesized by a chemical reduction method using Au nanowires (Au-NWs) as seeds in the presence of PEI and demonstrate their application toward oxygen reduction reaction (ORR) in an alkaline solution. Electrochemical results display that Au-NWs@Pd@PEI with optimal component shows enhanced ORR activity, selectivity, and durability compared to Pt/C electrocatalyst. Physical characterizations demonstrate that the electronic property of Pd shell mainly is affected by PEI polymer rather than Au-NWs core. Relative to PEI functionalized Pd nanowires without Au core, ORR activity enhancement of Au-NWs@Pd@PEI is exclusively ascribed to the surface strain effect. Meanwhile, loose-packed PEI polymer on the Pd surface can work as barrier nanosieves to exclusively prevent the access of methanol to Pd sites, which imparts Au-NWs@Pd@PEI with enhanced methanol tolerance toward ORR in an alkaline solution.