Facile
Synthesis of Iridium Nanocrystals with Well-Controlled
Facets Using Seed-Mediated Growth
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Abstract
Iridium
nanoparticles have only been reported with roughly spherical
shapes and sizes of 1–5 nm, making it impossible to investigate
their facet-dependent catalytic properties. Here we report for the
first time a simple method based on seed-mediated growth for the facile
synthesis of Ir nanocrystals with well-controlled facets. The essence
of this approach is to coat an ultrathin conformal shell of Ir on
a Pd seed with a well-defined shape at a relatively high temperature
to ensure fast surface diffusion. In this way, the facets on the initial
Pd seed are faithfully replicated in the resultant Pd@Ir core–shell
nanocrystal. With 6 nm Pd cubes and octahedra encased by {100} and
{111} facets, respectively, as the seeds, we have successfully generated
Pd@Ir cubes and octahedra covered by Ir{100} and Ir{111} facets. The
Pd@Ir cubes showed higher H<sub>2</sub> selectivity (31.8% vs 8.9%)
toward the decomposition of hydrazine compared with Pd@Ir octahedra
with roughly the same size