Size-dependent interfacial interactions in CeO2/Co3O4 catalysts: From single atoms to nanoparticles

Although CeO 2 /Co 3 O 4 composites exhibit excellent catalytic performance in oxidation reactions, the atomic-scale origin of their interfacial interactions remains unclear. In this work, we compare two contrasting catalysts: Co 3 O 4 -supported Ce single atoms and Co 3 O 4 -supported CeO 2 nanoparticles. We reveal that these two forms of Ce promote catalytic performance through different mechanisms. Ce single atoms occupy the octahedral Co 3+ sites within the Co 3 O 4 structure, forming Ce 3+ -Vo-Co active sites and thereby induce local compressive strain and facilitate the formation of point-defective oxygen vacancies. More importantly, Ce 3+ acts as an electron donor, elevating the d -band center of Co and facilitating O 2 activation via enhanced electron transfer to O 2 antibonding orbitals. In contrast, the extensive interfacial contact between CeO 2 nanoparticles and Co 3 O 4 triggers ion migration, which subsequently generates defects or amorphous interfacial domains with high oxygen mobility. The configuration of interfacial defects is highly dependent on the size of CeO 2 nanoparticles. Catalytic tests for the liquid-phase aerobic oxidation of benzyl alcohol confirm the superior performance of the single-atom catalyst, which exhibits 1.5 times higher activity and a 27.7 kJ/mol lower activation energy than its CeO 2 nanoparticle counterpart. Our findings demonstrate that the interaction between Ce species and Co 3 O 4 is dominated by electronic effects when Ce is atomically dispersed, whereas interfacial reconstruction becomes predominant with increasing CeO 2 nanoparticles size.