Facet-Dependent Metal-Support Interactions in Cobalt-Ceria Binary Oxides: Linking Ceria Morphology (rods vs. cubes) to Redox Behaviour and CO Oxidation

Abstract

Ceria-based binary oxides are widely employed in heterogeneous catalysis owing to their versatile applications and the fundamental interest stemming from their distinctive metal–support interactions. However, structural and surface parameters of ceria can significantly influence the redox and structural properties of mixed oxides, thereby affecting their catalytic performance. In this study, we investigate the effect of ceria morphology, i.e. nanorods (NR) and nanocubes (NC), on the intrinsic properties and interfacial interactions of cobalt–ceria catalysts, using CO oxidation as a probe reaction. Both bare ceria and cobalt/ceria samplers were comparatively characterized by various techniques such as N2 physisorption, X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM/TEM), temperature-programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS), Raman analysis and dynamic thermogravimetric analysis (TGA) under reaction conditions, revealing the interrelationship among ceria morphology, metal dispersion, reducibility, and catalytic activity. Specifically, ceria nanorods—predominantly exposing the {100} and {110} facets—exhibit enhanced textural and redox properties, which in turn lead to superior oxidation performance. The incorporation of cobalt further improves the catalytic activity, while still reflecting the performance trend of the bare supports, thereby underscoring the primary role of ceria morphology. Notably, cobalt is highly dispersed as nanoclusters across the surface of ceria nanorods, whereas it preferentially accumulates along the edges and corners of ceria nanocubes. This distinct dispersion behaviour strongly influences metal–support interactions and facilitates the stabilisation of Co2+ active sites over Co/CeO2-NR, enabling complete CO conversion at ca. 160 oC.