Guidelines for optimization of catalytic activity of 3d transition metal oxide catalysts in N2O decomposition by potassium promotion

The effect of potassium promotion on deN2O activity of various 3d electron spinels (Mn3O4, Fe3O4, Co3O4) was investigated by TPSR in conjunction with parallel work function measurements. The results were interpreted in terms of a surface dipole model (Kδ+–Osurfδ−) supported by DFT molecular modelling. The substantial enhancement of deN2O reactivity of Co3O4 and Mn3O4 upon K addition (decrease of ΔT50% by 150 °C) was observed, whereas for Fe3O4 the promotional effect was unexpectedly small. The maximum deN2O activity was found for potassium surface coverage of 2, 6, 8 K atoms/nm2 for cobalt, iron and manganese spinels, respectively. In each case the optimal level of doping was found for the minimum of the measured work function indicating that this parameter can be use for optimization of the catalyst deN2O reactivity.