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Abstract:
An extended N2O titration method was applied to characterize high-performance, supported Cu catalysts: Cu/ZnO:Al (68/29/3), Cu/ZnO (80/20) and Cu/MgO (80/20). Calculation of the oxygen diffusion coefficients showed significant differences within the series of catalysts, particularly as a function of temperature. The diffusion kinetics follows a parabolic law similar to previous high temperatures studies. The apparent activation energies of the oxygen diffusion correlate inversely with the strength of the metal support interaction. The metal-support-interaction is described by means of complementary techniques as complex interplay between structural and electronic effects located at the Cu-metal oxide interface. The significance of the metal-support-interaction, identified as relevant for the reduction and oxidation of the metallic Cu, correlates with the activity in catalytic CO oxidation. It is evident that the oxygen diffusion coefficient is indicative of the tendency of the Cu catalyst to withstand transformation into the oxides under oxidative reaction conditions controlled by the corresponding Cu-support-interaction.
