Redox and catalytic properties of CuO/CeO2 under CO + O2 + NO: Promoting effect of NO on CO oxidation

A CuO/CeO2 catalyst has been studied with respect to its catalytic activity for CO oxidation under stoichiometric conditions employing either O2 or O2–NO mixture as oxidants. The obtained results are rationalised on the basis of analysis of redox properties upon interaction with CO and O2–NO by EPR as well as by redox/catalytic analysis by operando-DRIFTS. These provide useful insight into the processes involved during NO reduction, for which two well differentiated steps associated to a change in the type of active centres during the course of the reaction are evidenced. Nevertheless, the most interesting result is related to observation of a novel promoting effect of NO on CO oxidation. This is explained mainly on the basis of DRIFTS results and appears to be associated with phenomena of adsorption/desorption of NOx species at interfacial positions which apparently activate such interfacial region allowing formation of greater amounts of active reduced copper centres in the presence of NO.