Galvanic
displacement reaction has been considered a simple method
for fabricating hollow nanoparticles. However, the formation of hollow
interiors in nanoparticles is not easily achieved owing to the easy
oxidization of transition metals, which results in mixed morphologies,
and the presence of surfactants on the nanoparticle surface, which
severely deteriorates the catalytic activity. In this study, we developed
a facile gram-scale methodology for the one-pot preparation of carbon-supported
PtNi hollow nanoparticles as an efficient and durable oxygen reduction
electrocatalyst without using stabilizing agents or additional processes.
The hollow structures were evolved from sacrificial Ni nanoparticles
via an in situ galvanic displacement reaction with a Pt precursor,
directly following a preannealing process. By sampling the PtNi/C
hollow nanoparticles at various reaction times, the structural formation
mechanism was investigated using transmission electron microscopy
with energy-dispersive X-ray spectroscopy mapping/line-scan profiling.
We found out that the structure and morphology of the PtNi hollow
nanoparticles were controlled by the acidity of the metal precursor
solution and the nanoparticle core size. The synthesized PtNi hollow
nanoparticles acted as an oxygen reduction electrocatalyst, with a
catalytic activity superior to that of a commercial Pt catalyst. Even
after 10 000 cycles of harsh accelerated durability testing,
the PtNi/C hollow electrocatalyst showed high performance and durability.
We concluded that the Pt-rich layers on the PtNi hollow nanoparticles
improved the catalytic activity and durability considerably
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