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Oxidative coupling reactions enable biomass-derived oxygenates to serve as sustainable platform molecules for a wide range of high-value chemicals. These catalytic reactions can be selectively triggered over alloys wherein a highly active dopant metal such as Pd is diluted into a sea of highly selective host metal atoms such as Au. Here, a range of supported Pd1Aux (x = 5–200) alloy nanoparticles were synthesized using a sequential reduction method with colloidal Au to achieve a high degree of compositional control and particle size uniformity. The promotional role of Pd was examined in the oxidation of ethanol to yield acetaldehyde and the coupling product ethyl acetate. Reactivity trends indicate that both the overall rate of ethanol oxidation and the selectivity toward coupling increase with Pd doping. Rate order and activation energy trends further suggest that the promotional role of Pd does not likely originate from simple O2 dissociation and spillover but rather from the stabilization of alkoxides at Pd-Au interfaces, disproportionately increasing coupling vs simple oxidation. Infrared spectroscopy and density functional theory calculations offer further insights into Pd microstructures in the presence of various key adsorbates, suggesting that Pd can lend this promotion in an isolated state. While this state is generally unstable in the surface due to preferences for segregation into the bulk, oxygen and pathway intermediates may aid in stabilizing surface structures. These findings lay groundwork to explain selectivity and activity control in a much wider range of oxidative functionalizations and to guide further catalyst development. 

Despite the broad catalytic relevance of metal–support interfaces, controlling their chemical nature, the interfacial contact perimeter (exposed to reactants), and consequently, their contributions to overall catalytic reactivity, remains challenging, as the nanoparticle and support characteristics are interdependent when catalysts are prepared by impregnation. Here, we decoupled both characteristics by using a raspberry-colloid-templating strategy that yields partially embedded PdAu nanoparticles within well-defined SiO₂or TiO₂supports, thereby increasing the metal–support interfacial contact compared to nonembedded catalysts that we prepared by attaching the same nanoparticles onto support surfaces. Between nonembedded PdAu/SiO₂and PdAu/TiO₂, we identified a support effect resulting in a 1.4-fold higher activity of PdAu/TiO₂than PdAu/SiO₂for benzaldehyde hydrogenation. Notably, partial nanoparticle embedding in the TiO₂raspberry-colloid-templated support increased the metal–support interfacial perimeter and consequently, the number of Au/TiO₂interfacial sites by 5.4-fold, which further enhanced the activity of PdAu/TiO₂by an additional 4.1-fold. Theoretical calculations and in situ surface-sensitive desorption analyses reveal facile benzaldehyde binding at the Au/TiO₂interface and at Pd ensembles on the nanoparticle surface, explaining the connection between the number of Au/TiO₂interfacial sites (via the metal–support interfacial perimeter) and catalytic activity. Our results demonstrate partial nanoparticle embedding as a synthetic strategy to produce thermocatalytically stable catalysts and increase the number of catalytically active Au/TiO₂interfacial sites to augment catalytic contributions arising from metal–support interfaces.