In this study, the morphologically uniform Co3O4 cubes (c-Co3O4), hexagonal plates (h-Co3O4) and tetrakaidecahedrons (t-Co3O4) were carefully synthesized and the crystalline facets of (001), (111), and (112) were identified. Au nanoparticles (3.1-3.3 nm) were deposited on the three Co3O4 entities, which were achieved to obtain specific Au-Co3O4 interfaces. A detailed comparison was made on the basis of their unique interfacial structures and catalytic behaviors. H2-TPR and XPS investigations revealed the important variations in reactivity of surface oxygen, surface Co3+/Co2+ ratio, evolution of surface oxygen vacancies as well as Au oxidation state upon Au loading and pretreatments. The enhanced CO oxidation by Au deposition, and particularly He- and in situ-pretreatments, has been elucidated in light of the structural specialties associated with the three facets of Co3O4 substrates and the corresponding Au-Co3O4 interfaces. The consequent activity enhancement for Co3O4 substrate and Au-Co3O4 interface was verified: (001) > (112) > (111), and Au/(112) > Au/(001) > Au/(111). The results of Au/h-Co3O4 also suggest that both Au cluster and Co3O4 structural feature can have a profound effect on the catalytic behaviour of generated interface. The present study extends the insights into the interface-dependent CO oxidation over the controllably prepared Au-Co3O4 interfacial structures.
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