Investigation of Au/Co3O4 nanocomposites in glycol oxidation by tailoring Co3O4 morphology

Abstract

The interfacial perimeter of nanogold and supports is often deemed as the catalytically active site for multiple reactions while the geometrical configuration of the interfacial perimeter at atomic scale is less studied. Herein, gold nanoparticles (NPs) of ca. 2.0 nm are dispersed on Co₃O₄ support in the shape of nanocubes (dominant Co₃O₄(001) facet) and nanoplates (Co₃O₄(111)), which forms different Au–Co₃O₄ interfaces with respect to the specific facet of the oxide support. A comparison is made on the basis of the interfacial structures and catalytic behavior of ethylene glycol oxidation. STEM analysis identifies that these metallic Au NPs interact with Co₃O₄ with an orientation relationship of Au/Co₃O₄(001) and Au/Co₃O₄(111). XPS and Raman spectroscopy investigations reveal the important variations in the reactivity of surface oxygen, surface O_ads/O_L ratio, and evolution of surface oxygen vacancies upon variation of the Co₃O₄ shape. Au/Co₃O₄-P exhibits much better catalytic activity than the Au/Co₃O₄-C counterpart in the aerobic oxidation of ethylene glycol, which is promoted by surface oxygen vacancies and intrinsic defects. It has been revealed that the surface oxygen vacancies participate in activating O₂, thus making Co₃O₄-P a superior support for Au NPs in the catalysis of ethylene glycol oxidation.