Dynamic and reversible transformations of subnanometre-sized palladium on ceria for efficient methane removal

Reversibly adjusting the active structures of supported metal catalysts in response to dynamic working conditions has long been pursued. Here we report the reaction-environment-modulated transformations of subnanometre-sized Pd on CeO2 for efficient methane removal, leveraging the reaction environments at different stages of automotive exhaust aftertreatment. During the cold start of vehicles, inactive Pd1 single atoms are readily transformed into PdOx subnanometre clusters by CO even at room temperature with excess O2, resulting in boosted low-temperature CH4 oxidation. At elevated temperatures, dispersion of PdOx cluster into Pd1 against metal sintering renders outstanding hydrothermal stability to the catalyst, to be activated during the next vehicle start. Combined experimental and computational studies elucidate the dynamically evolved Pd speciation on CeO2 at an atomic level. Modulating the reversible nature of supported metals helps overcome the long-existing trade-off between low-temperature activity and high-temperature stability, also providing a new paradigm for designing intelligent catalysts that brings single-atom/cluster catalysts closer to real applications. Reversibly modulating the structure of supported metals in response to dynamic working conditions is a desirable feature for catalysts. Now, the reversible transformation between single atoms and subnanometre clusters of Pd on CeO2 is demonstrated during automotive exhaust aftertreatment, achieving high methane oxidation activity and stability.