NO reduction by CO over a c-ZrO2(110) ultrathin film covering a Cu(110) surface (ZrO2/Cu) has been examined by means of density-functional theory calculations. Spontaneous transfer of electronic charge from Cu to zirconia gives the latter an ability to reduce oxidants. Gaining this excess charge, NO adsorbs and activates on the cationic Zr site of the oxide surface. Thus activated, two NO on adjacent Zr sites can react to form ONNO with an activation energy of 0.39 eV (8.9 kcal/mol), which readily decomposes into N2O and an O adatom. N2O also decomposes into N-2 and an O adatom with negligible activation energy of 0.06 eV (1.4 kcal/mol). CO reacts off the O adatoms left on the surface as CO2 with an activation energy of 0.36 eV (8.2 kcal/mol), completing a redox cycle. These results indicate high potentials of oxide-covered metal catalysts (metal@oxide) for NOx abatement.