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<p>The
synthesis of alloys with long range atomic scale ordering (ordered intermetallics)
is an emerging field of nanochemistry. Ordered intermetallic nanoparticles are
useful for a wide variety of applications such as catalysis, superconductors,
and magnetic devices. However, the preparation of nanostructured ordered
intermetallics is challenging in comparison to disordered alloys, hindering
progress in materials development. We report a process for converting
colloidally synthesized ordered intermetallic PdBi<sub>2</sub> to ordered
intermetallic Pd<sub>3</sub>Bi nanoparticles under ambient conditions by an
electrochemically induced phase transition. The low melting point of PdBi<sub>2</sub>
corresponds to low vacancy formation energies which enables the facile removal
of the Bi from the surface, while simultaneously enabling interdiffusion of the
constituent atoms via a vacancy diffusion mechanism under ambient conditions.
The resulting phase-converted ordered intermetallic Pd<sub>3</sub>Bi exhibits
11x and 3.5x higher mass activty and high methanol tolerance for the oxygen
reduction reaction compared to Pt/C and Pd/C, respectively,which is the highest
reported for a Pd-based catalyst, to the best of our knowledge. These results
establish a key development in the synthesis of noble metal rich ordered
intermetallic phases with high catalytic activity, and sets forth guidelines
for the design of ordered intermetallic compounds under ambient conditions.</p>
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