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The density functional theory(DFT)method has been performed to study the effects of CO and CO2 on the desulfurization of H2S over a ZnO sorbent.It shows that COS is inevitably formed on the ZnO(10-10)surface,which tends to be adsorbed onto the surface via a S–C bond binding with either a long or a short Zn–O bond.Potential energy profiles for the COS formation via reactions between H2S and CO,and H2S and CO2 on the ZnO(10-10)surface have been constructed.In the presence of CO,the dissociated active S of H2S reacting with CO leads to the formation of COS,and the activation energy of the ratedetermining step is 87.7 kJ mol-1.When CO2 is present,the linear CO2 is first transferred to active CO2 in a triplet state,and then combines with active S to form COS with the highest energy barrier of 142.4 kJ mol-1.Rate constants at different temperatures show that the formation of COS via the reaction of CO and H2S is easier than that of CO2 and H2S over the ZnO surface.