(327b) First-Principles Modeling of Single-Atom Catalysis: CO Oxidation over Atomically Dispersed Pt on CeO2

Supported metal catalysts are widely applied. Ceria is extensively used in exhaust gas clean-up due to the excellent oxygen storage capability and the pronounced ability to disperse the metal nanoparticles. Pt and Pd nanoparticles supported on ceria are critical in automobile three-way catalysts for pollution abatement and urban air quality control. The size of the supported metal particles is decisive for the catalytic performance. Due to the highly under-coordinated nature, single-atom catalysts (SACs) can lead to more efficient atom utilization and have the potential to enhance reactivity and selectivity. Recent advancements in experimental techniques have facilitated the synthesis and characterization of highly dispersed single metal atoms on ceria.^1-3 Single atoms on the ceria are prone to agglomeration when heated at elevated temperatures. However, surface defects of ceria are good candidates to trap Pt SAs owing to their strong interaction with low-coordination surface oxygen. The possible active sites of Pt-Ceria are still in debate. In this work, we develop a general methodology to investigate the relative stability of single-atoms on support in the presence of adsorbates at given temperature and pressure of adsorbates (e.g. CO). By combining density functional theory calculations and graph-theoretical kinetic Monte-Carlo simulations, we consider various Pt SAs and nanoparticles dispersed on ceria to investigate their CO oxidation activity, and propose that the Pt dopant has a comparable activity for CO oxidation as well as the Pt(111) facet under varying reaction conditions. The Pt atoms on terrace and steps of CeO₂ are nonactive because of the determined strong or weak CO binding, respectively. Through sensitivity analysis, the dominant surface species and the rate-determining steps are identified.

Reference:

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