Catalysts of copper (1 wt.%) supported on a CeO2/MgAl2O4 mixed support have been prepared by using different pH values (pH similar to 4, 8 and 10) in the impregnating solution of copper with the aim of favoring different situations of interaction between copper and the two support components. The catalysts have been characterized in detail by XRD, S-BET measurement, HREM and associated techniques, XPS, H-2-TPR and EPR which allows establishing a model of structural characteristics of the catalysts. The characterization results have been correlated with analysis of the catalytic properties of the samples for preferential oxidation of CO in a H-2-rich stream (CO-PROX) complemented by operando-DRIFTS. Important structural/chemical/catalytic differences as a function of the pH of the impregnating solution are revealed. These are explained on the basis of the characteristics of the interfaces formed between the different components present in each catalyst which basically determine the catalytic properties in each case. (C) 2016 Elsevier B.V. All rights reserved.