Activation of Lattice and Adatom Oxygen by Highly Stable Ceria-Supported Cu Single Atoms

Requiring catalysts to be both active yet stable over long periods of time under variable reaction conditions including high and low temperatures is a daunting challenge due to the almost mutual exclusivity of these constraints. Using CO oxidation as a probe reaction, we demonstrate that thermally stable single-atom copper catalysts prepared by high-temperature synthesis (atom trapping) on ceria can achieve this feat by allowing modulation of the Cu charge state through facile charge transfer between the active site and the support. This provides the catalysts with an ability to activate either lattice or adatom oxygen atoms, accessing additional reaction channels as the catalyst environment changes. Such adaptability allows dynamic response of such catalysts, enabling them to remain active under variable reaction conditions. The inherent stability of the catalyst arises from the enhanced strength of the Cu-O interactions established by high-temperature synthesis and remains stable even as the Cu oxidation state varies, effectively halting sintering and deactivation. As we show here, one can circumvent the dilemma of designing catalysts that are simultaneously active and stable by matching the redox properties of the active site and support and establishing an environmental adaptability into the active sites.