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

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 degrees 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.