Synergy between Metallic and Oxidized Pt Sites Unravelled during Room Temperature CO Oxidation on Pt/Ceria

Pt‐based materials are widely used as heterogeneous catalysts, in particular for pollutant removal applications. The state of Pt has often been proposed to differ depending on experimental conditions, for example, metallic Pt poisoned with CO being present at lower temperature before light‐off, while an oxidized Pt surface prevails above light‐off temperature. In stark contrast to all previous reports, we show herein that both metallic and oxidized Pt are present in similar proportions under reaction conditions at the surface of ca. 1 nm nanoparticles showing high activity at 30 °C. The simultaneous presence of metallic and oxidized Pt enables a synergy between these phases. The main role of the metallic Pt phase is to provide strong adsorption sites for CO, while that of oxidized Pt supposedly supplies reactive oxygen. Our results emphasize the complex dual oxidic–metallic nature of supported Pt catalysts and platinum's evolving nature under reaction conditions. Platinum‐based materials are widely used as heterogeneous catalysts, in particular for pollutant removal applications. Room temperature CO oxidation on ceria is shown to involve both oxidized and reduced platinum nanoparticles. These results emphasize the complex dual oxidic–metallic nature of supported platinum catalysts and their evolving nature under reaction conditions.