PNNL

Abstract

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 active site and support. This provides the catalysts with an ability to activate either lattice or adatom oxygen atoms, accessing additional reaction channels depending on the reaction conditions. Such adaptability allows dynamic response of 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 from high temperature synthesis that exist even when Cu oxidation state varies, which retards 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 around the active sites. The experimental effort (catalyst synthesis and characterization via TEM and DRIFTS, etc.) was supported by the DOE/BES Catalysis Science Program, Grant DE-FG02-05ER15712. Theory effort was supported by the US Department of Energy (US-DOE) Basic Energy Sciences, Chemical Sciences, Geosciences and Biosciences Division, Catalysis Program (FWP 47319). C.E.G.-V., X.I.P.-H., and D.J. thank the funding support from US-DOE Energy Efficiency and Renewable Energy Vehicle Technology Office. C.E.G.-V. and X.I.P.-H thank Fulbright Colombia and Colciencias for the financial support provided to pursue their Ph.D. The computer resources were provided by the PNNL Research Computing facility and the National Energy Research Center (NERSC) located at LBNL. The authors thank Libor Kovarik for the help in the acquisition of the STEM/EDS images at EMSL facilities.