Single-atom catalysts (SACs) exhibit excellent performance for various catalytic reactions but it is still challenging to have adequate total activity for practical applications. Here we report the high-valence, square planar Pt1-O4as an active site that enables significantly to increase the total activity of the Pt1/Fe2O3SAC with a Pt loading of only ∼30 ppm, which is similar to that of a 1.0 wt% nano-Pt/Fe2O3, for CO oxidation at 350 °C. Density functional theory calculations reveal that Pt1-O4catalyzes CO oxidation through a non-classical Mars-van Krevelen mechanism. The adsorbed O2on Pt1atoms activates the coordination oxygen in the Pt1-O4configuration, and then a barrierless O2dissociation occurs on the Pt1-Fe2triangle to replenish the consumed coordination oxygen by the cooperative action of Pt 5d and Fe 3d electrons. This work provides a new fundamental understanding of oxidation catalysis on stable and active SACs, providing guidance for rationally designing future heterogeneous catalysts.
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