Ceria-supported Pd catalysts with different size regimes ranging from single atoms to nanoparticles for the oxidation of CO

Supported metal catalysts are the most widely used in industrial processes and the metal particle size plays a crucial factor in determining the catalytic performance. Herein, CeO2-supported Pd catalysts with different Pd size regimes ranging from single atoms, to nanoclusters (1-2 nm), and to nanoparticles (> 2 nm) were used for both CO oxidation and preferential oxidation of CO in H-2 (CO-PROX). Compared to Pd nanoclusters and nanoparticles, CeO2-supported single Pd atoms (Pd-SA/CeO2) are the most intrinsically active in CO oxidation, with an apparent activation energy of ca. 40 kJ mol(-1). Results of kinetic investigations and in situ diffuse reflectance infrared Fourier transformed spectroscopy demonstrate the CO oxidation proceeding through a Langmuir-Hinshelwood mechanism with the decomposition of formate species acting dominantly as the rate-determining step. The CO reaction rate is exclusively promoted on Pd-SA/CeO2 catalysts for the CO-PROX reaction, which could be ascribed to a stronger H-spillover effect on isolated Pd sites to produce bridged-OH on CeO2 surface, simultaneously facilitating the consumptions of bicarbonate and formate species. There results greatly deepen the fundamental understanding of the Pd size regimes over Pd/CeO2 catalysts for the oxidation of CO. (c) 2022 Elsevier Inc. All rights reserved.

Automated summary

Supported metal catalysts are widely used in industrial processes, and the size of the metal particles is crucial for the catalytic performance. This study investigates CeO2-supported Pd catalysts with different Pd size regimes and reveals that single Pd atoms supported on CeO2 have the highest intrinsic activity in CO oxidation and promote the CO-PROX reaction due to a stronger H-spillover effect.