CeO2-encapsulated noble metal nanocatalysts: enhanced activity and stability for catalytic application

Encapsulation of small noble metal nanoparticles has received attention owing to the resulting highly increased stability and high catalytic activity and selectivity. Among the types of inert metal oxides, CeO2 is unique. It is inexpensive and highly stable, and, more importantly, the unique electronic configuration gives it a strong capability to provide active oxygen. The method of fabricating CeO2-encapsulated noble metal nanocatalysts is determined by the requirements of the application. In this review, we first describe the various types of encapsulated noble metals and then the current developments of synthesis in detail, including the types of hybrid nanostructures and successful synthetic strategies. The following section, concerning catalytic applications, is divided into three topics: anti-sintering capabilities, catalytic activities and selectivities. We hope that this review of the recent achievements and the proposed strategy for addressing the emerging challenges will inspire further developments in this research area. Encapsulating noble metals inside cerium dioxide (CeO2) nanostructures produces catalysts with longer lives and more pronounced activity. Hongjie Zhang and colleagues from the Chinese Academy of Sciences have reviewed recent synthetic reactions and affirm that CeO2 — a low-cost, oxygen-rich and electroactive coating material — can significantly reduce agglomeration effects that normally deactivate catalytic metals such as platinum, gold and palladium. While several coating types have been identified, an innovative ‘yolk-shell’ arrangement in which a mobile metal core rattles around an outer CeO2 layer is particularly promising for liquid-phase reactions. The researchers caution that symbiotic effects between the outer CeO2 shells and metal nanocatalysts are highly dependent on particle size. They indicate that new methods to optimize nanoparticle nucleation could be used to extend this approach to other valuable metals in the periodic table. The most recent developments in the synthesis and structure engineering of CeO2-encapsulated noble metal hybrids for catalytic applications are critically discussed.