A Mechanistic Study on the Nucleation and Growth of Au on Pd Seeds with a Cubic or Octahedral Shape

摘要

This article reports a systematic study on the seed-mediated growth of PdAu bimetallic nanocrystals with a variety of controlled morphologies. The key to the success of this synthesis is to manipulate the reaction kinetics by controlling a set of experimental parameters, which include the amount of ascorbic acid used as a reductant, the amount of HAuCl4 as a precursor to elemental Au, the reaction temperature, and the type of seeds employed. Starting from Pd nanocubes of 18 nm in edge length, PdAu bimetallic nanocrystals with a number of morphologies, which includes hybrid dimers, coreshell nanocubes with flat faces, and coreshell nanocubes with concave faces could all be obtained by simply speeding up the reduction of HAuCl4. The same synthesis and control could also be extended to seeds based on Pd octahedrons. For the first time, it was possible to generate Pd@Au coreshell nanocubes and octahedrons with concave faces. The Pd@Au coreshell nanocubes with concave faces exhibited enhanced activity in catalyzing the oxidization of ascorbic acid relative to their counterparts with flat faces or the cubic Pd seeds.