Constructing Intermediate Encapsulation on Ru/CeO 2 Nanocatalysts to Enhance Ammonia Synthesis

ABSTRACT Engineering the metal‐support interfacial structure in supported heterogeneous catalysts opens wide opportunities to tailor catalytic performance, particularly by exploiting strong metal‐support interactions (SMSI) that modify active‐site electronic and geometric properties to tune adsorption energetics, activity and stability. However, designing SMSI that simultaneously meets the geometric requirement of sufficient active site exposure, and the electronic requirement remains challenging. Here, we achieved an intermediate encapsulation by forming crystallographically defined CeO x overlayers on Ru/CeO 2 via a Ru‐precursor‐mediated route. Using Ru 3 (CO) 12 as the precursors creates a locally reducing environment on CeO 2 {100}, inducing localized surface modification and formation of truncated‐pyramid‐shaped SMSI overlayers on Ru with a height of ∼2–3 atomic layers (Ru/CeO 2 ─CO). By contrast, catalysts prepared from Ru(NO)(NO 3 ) 3 (Ru/CeO 2 ─NO 3 ) show no SMSI encapsulation. Ru/CeO 2 ─CO exhibits significantly higher oxygen‐vacancy concentrations both overall and within the SMSI layer, which promotes electron transfer from the interface and overlayer to the Ru nanoparticles. The formation of electron‐rich Ru species, without blocking a significant number of active sites, facilitates nitrogen activation and enhances catalytic ammonia synthesis. This work presents a novel strategy to construct intermediate SMSI encapsulation and also provides mechanistic insight into precursor‐dependent activity at the nanoscale.