Metal oxides have been tried as substitutes for Pt and Pd catalysts toward NO oxidation.[1-3] Meanwhile,they are the active component of so-called “NOx traps”,which are used to temporarily store NOx.[4] This competition between oxidation and storage makes the reaction of NO oxidation on metal oxides particularly interesting.In this work,the NO oxidation on Cu2O(111)either with molecular and dissociated oxygen or lattice O of the Cu2O(111)surface was studied by using periodic DFT calculations.It was found that NO reacts with molecular or dissociated oxygen,rather than lattice O,to form NO2.The NO oxidation by molecular or dissociated oxygen occurs preferentially through the Elay-Rideal mechanism.In the case of the NO oxidation by molecular oxygen,four atom intermediates(O*ON*O and O*ONO)play an important role in reducing the barrier.In all the routes considered in this case,the most readily is the path(NO+O2*→O*ONO→NO2+O*; NO+O*→NO2*→NO2).For the reaction of the NO oxidation by dissociated oxygen,the highest barrier to be surmounted is 105 kJ/mol and two NO2 molecules produced are likely to desorb from the surface with an energy barrier of 53.3 and 103.2 kJ/mol,respectively.