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Pt‐based alloy nanocrystals have shown great success in oxygen reduction electrocatalysis owing to their unique surface and electronic structures. However, they suffer from severe stability issues due to the dissolution of non‐noble metal elements, leading to the "trade‐off" between activity and stability. In this work, targeting the stability issue of a PtxCuy‐based alloy, Pt2CuW0.25 ternary alloy nanoparticles are synthesized by thermal reduction strategy based on wet‐chemical method using W(CO)6 as a reductant. Apart from the competitive activity, the obtained Pt2CuW0.25/C shows remarkable stability, whereby the area specific activity and mass activity maintain 89.5% and 95.9% of the initial values, respectively, after 30 000 cycles of accelerated polarization between 0.6 and 1.1 V (vs reversible hydrogen electrode). By using vacancy formation energy of surface Pt as the descriptor, it is found that the enhanced stability of Pt2CuW0.25/C originates mainly from the stronger bonding between W and Pt/Cu atoms, acting as an "adhesive" to stabilize the atoms from dissolution, which is further verified by chemical stability experiments. This work demonstrates a rational design strategy for ternary alloy nano‐electrocatalyst that has high thermodynamic stability while maintaining high activity by employing high‐melting‐point metal. [ABSTRACT FROM AUTHOR]

Bimetallic PtCu nanocrystals (NCs) with well-defined hexa-pod morphology were synthesized via a wet chemistry approach. The as-synthesized convex NCs with dimensions of around 20 nm show exposed low-index (111) facets on the seeds and various high-index facets on the pods. The growth mechanism involved preferred growth along the <100> crystallographic direction on cuboctahedral seeds. The synthetic protocol could be applied to the synthesis of PtCu NCs with various Cu/Pt ratios. The electro-catalytic activity of the hexa-pod PtxCuy NCs supported on carbon black towards the oxygen reduction reaction (ORR) was studied. The hexa-pod PtCu/C catalysts exhibit the highest specific activity (3.7 mA/cm) and mass activity (2.4 A/mg) reported to date for PtCu. Comparison with other morphological forms of PtCu indicated that the enhanced activity originated from morphological factors. The existence of high-index facets as well as abundant edges and steps on the pods could reasonably explain the enhanced catalytic activity. The hexa-pod PtCu/C catalysts also show high morphological stability and activity after accelerated durability tests. The as-synthesized hexa-pod PtCu NCs have high potential as cathode electro-catalysts for proton exchange membrane fuel cells. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]