Strong dispersion effect of cobalt spinel active phase spread over ceria for catalytic N2O decomposition: The role of the interface periphery

Abstract

A series of Co3O4/CeO2 catalysts with increasing cobalt spinel loading in the range of 1–20 wt.% was prepared by incipient wetness impregnation of CeO2. The obtained catalysts were thoroughly examined by XRD, XPS, XRF, RS, TEM/EDX/EELS, TPR and BET techniques. The catalytic tests in deN2O reaction revealed that the 10 wt.% of cobalt spinel in supported system is able to reproduce the activity of bare Co3O4 catalyst. However, it was found that the catalyst with the lowest content of Co3O4 equal to 1 wt.% exhibits the highest apparent reaction rate per mass of the spinel active phase. The observed activity was explained basing on the transmission electron microscopy analysis in terms of the dispersion of spinel phase over ceria support. A simple model that accounts for the observed strong dispersion effect is proposed. It consists in a two-step mechanism, where N2O is dissociated on the spinel nanograins and the resultant oxygen species are preferentially recombined at the Co3O4/CeO2 interface periphery.