This paper deals with the selective catalytic reduction of NO with the use of toluene as a reducer and in the presence of excess oxygen. The three-function model of HC-SCR of NO has been studied over ceria-zirconia supported copper oxide (CuO/CeZrO2). The particular functions of CuO/CeZrO2 catalyst have been proved by the catalytic runs carried out in temperature-programmed conditions (TPSR) and in situ DRIFTS. On the basis of obtained results it was observed that NO is oxidized by O-2 to NO2, which is subsequently used for toluene activation. Obtained oxygenates (CxHyOz) clean the active sites from oxygen, which was left during NO reduction to N-2. The DRIFTS studies have shown that NO adsorbs on the surface of ceria-zirconia forming (i) the bridging nitrate when the adsorption of NO is carried out in the absence of gaseous O-2 and (ii) both nitrite and nitrate species when the adsorption is carried out in the presence of O-2. Formation of these surface species can be due to the presence of surface peroxide species (O-2(2-)) or superoxide species (O2-). The presence of the latter enhances NO adsorption and influences the evolution of surfaces species during temperature programmed reaction. (c) 2013 Elsevier B.V. All rights reserved.