Potential-Dependent Structural
Memory Effects in Au–Pd Nanoalloys
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Abstract
Alloying of metals offers great opportunities for directing
reactivity
of catalytic reactions. For nanoalloys, this is critically dependent
on near-surface composition, which is determined by the segregation
energies of alloy components. Here Au–Pd surface composition
and distribution of Pd within a Au<sub>0.7</sub>Pd<sub>0.3</sub> nanoalloy
were investigated by monitoring the electrocatalytic
behavior for the oxygen reduction reaction used as a sensitive surface
ensemble probe. A time-dependent selectivity toward the formation
of H<sub>2</sub>O<sub>2</sub> as the main oxygen reduction
product has been observed, demonstrating that the applied potential
history determines surface composition. DFT modeling suggests that
these changes can result both from Pd surface diffusion and from exchange
of Pd between the shell and the core. Importantly, it is shown that
these reorganizations are controlled by surface adsorbate population,
which results in a potential-dependent Au–Pd surface composition
and in remarkable structural memory effects
