Distant Oxide Surfaces Dominating Catalytic Reaction Kinetics: The Case of Pt/CeO2

One of the main goals of catalysis research is to improve the reaction efficiency by using platinum-group metals (PGMs) more effectively, given their high cost. PGMs are typically dispersed on oxide supports to maximize their surface area, under the assumption that catalytic activity arises primarily from the PGMs and their immediate oxide surroundings, while oxide surfaces located further away from PGMs are often considered catalytically irrelevant. However, a growing body of research on spillover phenomena suggests that PGMs can influence the catalytic properties of oxide surface sites located several nanometers away from PGMs, prompting the question of whether distant oxide surfaces can play a more active, or even dominant, role in catalytic kinetics. A shift in understanding, from viewing the oxide surface as merely a passive support to recognizing it as an active promoter of the rate-limiting step (RLS), would offer an alternative framework for optimizing PGM utilization. In this contribution, we investigated the role of distant oxide surfaces in CO oxidation, using Pt/CeO₂ as a model system. Our findings show that distant CeO₂ surfaces are not inert but can promote the CO oxidation reaction via oxygen spillover. Interestingly, when the CeO₂ content in Pt/CeO₂ is high, the catalytic activity across catalysts with varying distributions of Pt single atoms and clusters is identical. Kinetic analysis reveals that, in CeO₂-rich Pt/CeO₂ catalysts, the RLS is the activation of oxygen on the distant CeO₂ surface. Further investigation indicated that the alignment of CeO₂ grains during reductive treatment facilitates the oxygen supply to Pt, boosting catalytic activity. This study suggests that leveraging the catalytic function of the distant oxide surface offers a promising strategy to enhance the efficiency of PGMs, providing an alternative perspective on catalyst development.