Investigation of catalytic activity of Au/Co3O4(001) and Au/Co3O4(111) in the CO oxidation reaction

Abstract

In this study, gold nanoparticles of approximately 2 nm were immobilized onto Co₃O₄ oxides with two morphologies (nanocube and nanoflower) through the simple impregnation of Au:PVA colloids. The gold nanoparticles did not undergo sintering after the PVA removal under the 300 °C annealing conditions (in air), evidenced by the temperature-programmed oxidation and STEM analysis. Both the resulting Au/Co₃O₄–C and Au/Co₃O₄–F catalysts demonstrated significantly enhanced activity compared to their respective Co₃O₄ counterparts in the CO oxidation reaction. The catalytic activity distinctly decreases in the order Au(111)/Co₃O₄–C(001) > Au(111)/Co₃O₄–F(111) in the CO oxidation, which was directly associated with the gold-oxide interfacial perimeter and related to the surface ratios of Co³⁺/Co²⁺ and O_ads/O_latt. These findings underscore the predominant role of the interfacial perimeter between Au NPs and Co₃O₄(001) in driving the CO oxidation reaction. The deactivation of the catalysts during the CO oxidation reaction at room temperature is attributed to the accumulation of CO₂ rather than the sintering of the Au NPs, validated by the CO₂-TPD tests.