Reversible ultrasmall CeO2 decomposition enhances sintering-resistance in Cu single-atom catalysts

Single-atom catalysts (SACs) have shown exceptional performance in heterogeneous catalysis, yet their practical application remains hindered largely due to their susceptibility to sintering and subsequent deactivation under harsh reaction conditions. To address the instability, we focused on Cu SACs/Al 2 O 3 and developed a novel dynamic thermostability system by introducing the functional CeO 2 oxide that serves as oxygen reservoir to suppress the sintering. High stability of the Cu SACs was directly observed through in situ aberration-corrected environmental scanning transmission electron microscopy under both thermal oxidation and reduction conditions. Combining first-principles calculations, we revealed that the ultra-stable Cu SACs was achieved by the sustained lattice oxygen supply from reversible ultrasmall CeO 2 (2.25 nm) decomposition to form mobile O x -Cu species, which establishes a dynamic equilibrium between the catalytically active O-Cu and sintering-resistant O 2 -Cu monomers. We found this stabilization strategy by introducing the CeO 2 oxide as oxygen reservoir can be effectively extended to a broad range of SACs (Ag, Co, Pt, Fe, Ni) on 3 different oxide supports (ZnO, TiO 2 , SiO 2 ). We anticipate this strategy and insights can be helpful in designing highly active and stable SACs toward industrialization.