This article reports a novel scalable method to prepare ultrathin and uniform Pd@Pt nanowires (NWs) with controllable composition and shell thickness, high aspect ratio, and smooth surface, triggered by bromide ions via a galvanic replacement reaction between PtCl6(2-) and Pd NWs. It was found that bromide ions played a vital role in initiating and promoting the galvanic reaction. The bromide ions served as capping and oxidized etching agents, counterbalancing the Pt deposition and Pd etching on the surface to give final Pd@Pt core-shell nanostructures. Such a counterbalance and the formation PtBr6(2-) with lower redox potential could lower the reaction rate and be responsible for full coverage of a smooth Pt shell. The full coverage of Pt deposited on Pd NWs is important for the enhancement of the activity and stability, which depend strongly on the Pt content and Pt shell thickness. Significantly, the Pd@Pt NWs with Pt content of 21.2% (atomic ratio) exhibited the highest mass activity (810 mA mg(-1)(Pt)) and specific activity (0.4 mA cm(-2)). Interestingly, the mass activity (1560 mA mg(-1)(Pt)) and specific activity (0.98 mA cm(-2)) of Pd@Pt (21.2%) NWs increased to 2.45 and 1.95 times the initial values after 60k cycles tests, 8.5 and 9.0 times greater than those of Pt/C catalysts. In addition, these ultrathin NW electrocatalysts with large aspect ratio are easy to form into a freestanding film, which improves the mass transport, electrical conductivity, and structure stability.

We report the enhanced activity and stability of CuPt bimetallic tubular electrocatalysts through potential cycling in acidic electrolyte. A series of CuPt tubular electrocatalysts with sequential increased lattice ordering and surface atomic fraction of Pt were designed and synthesized by thermal annealing to reveal their improved electrocatalytic properties. These low-Pt-content electrocatalysts with Pt shell are formed through the thermal annealing and following potential cycling treatment. The catalysts (C1) with a low atomic fraction of Pt on the surface and low lattice ordering in the bulk are treated in acidic electrolyte, resulting in the formation of a Pt shell with relatively low activity and stability. However, the catalysts (C2) with a Pt-rich surface and high lattice ordering have a highly enhanced electrochemical surface area after potential cycling via surface roughing. The rough Pt shell of the C2 catalysts is achieved by leaching of surface Cu and the concomitant morphology restructuring. The C2 Pt surface demonstrated highly improved specific and mass activities of 0.8 mA cm Pt −2 and 0.232 A mg Pt −1 at 0.9 V for oxygen reduction reaction (ORR), and after 10 000 cycles, the C2 catalysts display almost no loss of the initial electrochemical active surface area (ECSA). Meanwhile, the stability of these CuPt catalysts shows regular change. Moreover, after a long-term stability measurement, the ECSA of C2 catalysts can be restored to the initial value after another potential cycling treatment, and thus, this kind of electrocatalyst may be developed as next-generation restorable cathode fuel cell catalysts.

Pt-Ni alloy nanocrystals with controlled architectures (multi-arms and flowers) have been synthesized via a simple colloid chemistry method. The crystal surfaces possess abundant low-coordination defect sites, where the reaction kinetics of methanol oxidation can be improved, resulting in the catalysts exhibiting better stability and higher resistance to poisoning.

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