Size-Dependent Disorder-Order Transformation in the Synthesis of Monodisperse Intermetallic PdCu Nanocatalysts

作者：Wang, Chenyu; Chen, Dennis P.; Sang, Xiahan; Unocic, Raymond R.; Skrabalak, Sara E.^*

来源：ACS Nano, 2016, 10(6): 6345-6353.

DOI：10.1021/acsnano.6b02669

• seed-mediated co-reduction
• nanocrystals
• electrocatalysis
• disorder-order transformation

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.

• 出版日期2016-6