Partial PdAu nanoparticle embedding into TiO2 support accentuates catalytic contributions from the Au/TiO2 interface

Most supported catalysts are produced by forming or attaching nanoparticles onto surfaces of supports. However, controlling the interfacial contact between the nanoparticles and support?which has been reported to be the active site for many catalytic reactions?remains synthetically challenging. Here, we employ a colloidal templating approach to derive catalysts comprising PdAu nanoparticles partially embedded within SiO2 or TiO2 supports. Compared to a conventional catalyst prepared by attaching PdAu nanoparticles onto TiO2 surfaces, partial entrenchment of nanoparticles into TiO2 increased the nanoparticle?support interfacial perimeter and enhanced the catalytic activity by 4.1-fold. Our results illustrate partial nanoparticle embedding as a synthetic strategy to increase the number of Au/TiO2 interfacial sites and amplify their catalytic contributions, while enhancing catalyst stability. 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 SiO2 or TiO2 supports, 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/SiO2 and PdAu/TiO2, we identified a support effect resulting in a 1.4-fold higher activity of PdAu/TiO2 than PdAu/SiO2 for benzaldehyde hydrogenation. Notably, partial nanoparticle embedding in the TiO2 raspberry-colloid-templated support increased the metal?support interfacial perimeter and consequently, the number of Au/TiO2 interfacial sites by 5.4-fold, which further enhanced the activity of PdAu/TiO2 by an additional 4.1-fold. Theoretical calculations and in situ surface-sensitive desorption analyses reveal facile benzaldehyde binding at the Au/TiO2 interface and at Pd ensembles on the nanoparticle surface, explaining the connection between the number of Au/TiO2 interfacial 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/TiO2 interfacial sites to augment catalytic contributions arising from metal?support interfaces.