Keys Unlocking Redispersion of Reactive PdO Nanoclusters on Ce-Functionalized Perovskite Oxides for Methane Activation.

Nowadays, trace CH emitted from vehicle exhausts severely threaten the balance of the ecology system of our earth. Thereby, the development of active and stable catalysts capable of methane conversion under mild conditions is critical. Here, we present a convenient method to redisperse catalytically inert PdO nanoparticles (NPs) (>10 nm) into reactive PdO nanoclusters (∼2 nm) anchored on a Ce-doped LaFeO parent. Isothermally activated in an N flow, the redispersed catalyst achieved a CH conversion of 90% at 400 °C, which is significantly higher than the fresh and H- and O-treated counterparts (625, 616, and 641 °C, respectively), indicating the importance of the gas atmosphere in the redispersion of PdO NPs. In addition, the comprehensive catalyst characterizations demonstrated that the isolated Ce ions in the perovskite lattice play an irreplaceable role in the redispersion of reactive sites and the reduction of the energy barrier for C-H scission. More importantly, the Ce additive helps to stabilize the PdO species by reducing overoxidation, resulting in significant lifetime extension. Through a thorough understanding of structural manipulation, this study sheds light on the design of highly performing supported catalysts for methane oxidation.