Journal
ACS NANO
Volume 10, Issue 6, Pages 6345-6353Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.6b02669
Keywords
seed-mediated co-reduction; nanocrystals; electrocatalysis; disorder-order transformation
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Funding
- U.S. Department of Energy (Basic Energy Sciences) [DE-SC0010489]
- Camille Dreyfus Teacher Scholar Program
- IU Siedle Materials Fellowship
- U.S. Department of Energy (DOE) [DE-SC0010489] Funding Source: U.S. Department of Energy (DOE)
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The high performance of Pd-based intermetallic nano catalysts has the potential to replace Pt-containing catalysts for fuel-cell reactions. Conventionally, intermetallic particles are obtained through the annealing of nanoparticles of a random alloy distribution. However, this method inevitably leads to sintering of the nanoparticles and generates polydisperse samples. Here, monodisperse PdCu nanoparticles with the ordered B2 phase were synthesized by seed-mediated co-reduction using PdCu nanoparticle seeds with a random alloy distribution (A1 phase). A time-evolution study suggests that the particles must overcome a size-dependent activation barrier for the ordering process to occur. Characterization of the as-prepared PdCu B2 nanoparticles by electron microscopy techniques revealed surface segregation of Pd as a thin shell over the PdCu core. The ordered nanoparticles exhibit superior activity and durability for the oxygen reduction reaction in comparison with PdCu A1 nanoparticles. This seed-mediated co-reduction strategy produced monodisperse nanoparticles ideally suited for structure-activity studies. Moreover, the study of their growth mechanism provides insights into the size dependence of disorder-order transformations of bimetallic alloys at the nanoscale, which should enable the design of synthetic strategies toward other intermetallic systems.
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