Pivotal role of Ce3+ polarons on promoting oxygen reduction reaction activity of Pt1/CeO2 catalysts

Abstract

The Pt1/CeO2 single-atom catalyst excels across catalytic fields, promising applications in the oxygen reduction reactions (ORRs). Here, we employ first-principles calculations to systematically investigate the ORR mechanism catalyzed by Pt1/CeO2 systems and the activity regulated by Ce3+ polarons. We determine the reaction pathways of different Pt1/CeO2 systems by evaluating four critical factors: O2 adsorption energy, O2 dissociation Gibbs barrier, Gibbs free energy change for O2→OOH*, and H2O2 adsorption structure. Notably, most Pt1/CeO2 systems tend to react through the 4e− associative path. Theoretical activity calculations reveal that PtOH/CeO2(110) system show low overpotential of 0.47 V comparable to pure Pt. The excellent ORR activity is attributed to the synergistic mechanism of Pt and surrounding Ce3+ polarons, where the polaron regulation mechanism dominates the reaction. The quantity of Ce3+ polarons not only affects the reaction active sites but also regulates the radical adsorption state. With an elevated Ce3+ polarons concentration, the ORR overpotential in Pt1/CeO2 system can decrease from 0.47 to 0.16 V, leading to a substantial enhancement in activity. This work first underscores the crucial involvement of Ce3+ polarons in catalyzing the ORR, reducing the significance of Pt in catalysis, inspiring a new way to design active non-platinum electrocatalysts for ORR in experiments.