In Situ Correlation of Dealloying and Oxygen Reduction Activity in Single Au@Ag Nanoparticles

Electrochemical dealloying is a potent postsynthetic strategy for enhancing the activity of catalysts by selectively removing components and restructuring the surface composition, but quantitative dealloying-activity relationships are obscured by ensemble averaging and separating transformation from electrocatalysis. Here we report an in situ, correlated anodic-cathodic single-nanoparticle collision electrochemical strategy that directly links electrochemical dealloying with electrocatalytic activity for the same Au@Ag nanoparticle (NP). Individual core-shell Au@Ag NPs undergo programmed anodic pulses to oxidatively dissolve Ag, followed immediately by a cathodic step to quantify oxygen reduction reaction (ORR) activity, yielding a one-to-one composition-activity correlation from correlated current transients. By employing a nitrogen-functionalized carbon ultramicroelectrode to expand the accessible dealloying window, we resolve a volcano-type dependence of ORR activity on the Ag/Au ratio and identify an optimal composition of Ag/Au of 2.5:1. This platform enables rapid, single-particle screening of dealloyed electrocatalysts and provides quantitative guidance for composition-optimized catalyst design beyond ensemble averaging.