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Over the last 80 years, chlorine (Cl) has been the primary promoter of the ethylene epoxidation reaction valued at ~40 billion USD per year, providing a ~25% selectivity increase over unpromoted silver (Ag) (~55%). Promoters such as cesium, rhenium, and molybdenum each add a few percent of selectivity enhancements to achieve 90% overall, but their codependence on Cl makes optimizing and understanding their function complex. We took a theory-guided, single-atom alloy approach to identify nickel (Ni) as a dopant in Ag that can facilitate selective oxidation by activating molecular oxygen (O₂) without binding oxygen (O) too strongly. Surface science experiments confirmed the facile adsorption/desorption of O₂on NiAg, as well as demonstrating that Ni serves to stabilize unselective nucleophilic oxygen. Supported Ag catalyst studies revealed that the addition of Ni in a 1:200 Ni to Ag atomic ratio provides a ~25% selectivity increase without the need for Cl co-flow and acts cooperatively with Cl, resulting in a further 10% initial increase in selectivity. 

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. 

If a critical acetylene surface coverage threshold above one monolayer is attained, acetylene conversion to benzene occurs with 100% selectivity on Ag(111). The presence of multiple monolayers has the unforeseen effect of increasing benzene production while maintaining selectivity. 

We leveraged Bayesian optimization (BO) to search for potential high-performing catalysts. Our BO workflow can be initialized with as few as 2 to 8 data points, and often identifies the optimal single-atom alloy surface in just a few iterations.