Unique role of silica in MOF-Derived High-Loading Palladium-on-Ceria single atom catalysts with excellent efficiency and durability

In most cases, the sintering tendency of supported metal single atoms could be attributed to the unstable structural characteristics of supports in demanding operating conditions, particularly for high-loading single-atom catalysts (SACs), ultimately resulting in deactivation. To address this issue, SiO2 is employed to enhance the structural stability of both supports and the supported Pd single atoms. SiO2 serves not only to prevent the collapse of support structures but also to promote the activation of surface oxygen species by facilitating electron transfer with the supports. This, in turn, establishes strong metal-support interactions (MSIs) to stabilize and activate atomically dispersed Pd species. Additionally, the electrons donated from Ce-O and Si-O to Pd atoms further catalyze the formation of oxygen vacancies, ultimately leading to significantly improved activity and durability in CO oxidation. Without SiO2, the instability of support structure, coupled with the weak MSIs, promotes the aggregation of Pd atoms, resulting in relatively lower catalytic activity and durability.