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 PdO_x subnanometre clusters by CO even at room temperature with excess O₂, resulting in boosted low-temperature CH₄ oxidation. At elevated temperatures, dispersion of PdO_x 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.