Abstract: The conversion and utilization of CO₂ are not only an important research subject in C₁ chemistry, but also of great significance in pollution control. It is generally accepted that CO₂^- adspecies on metal surfaces as an activated adsorption state of CO₂ is a pivotal intermediate in the process of CO₂ activation. The adsorption energy of CO₂^- and the energy barrier of various pathways of CO₂ activation on Cu(111), Pd(111), Fe(111) and Ni(111) surfaces have been predicted by using the UBI QEP(Unity bond index quadratic exponential potential) method. The theoretical results show that the stability of CO₂^- adsorbed on the above four transition metal surfaces follows the order: Fe(111)>Ni(111)>Cu(111)>Pd(111). CO₂^- surface species can be readily formed on the Fe and Ni surfaces and is liable to dissociate, giving rise to C(a) and O(a) on the Fe surface and CO(a) and O(a) on the Ni surface, respectively. On the Cu surface, though the formation of CO₂^- is less favorable, the hydrogenation of the as formed CO₂^- would be favorable over its direct dissociation which can lead to COand Oadspecies. On the Pd surface, the activation of CO₂ is rather difficult, as the formation of CO₂^- adspecies is thermodynamically quite unfavorable from the view point of activation enthalpies.

Key words: CO₂ activation, UBI QEP method, CO₂^-, Methanol synthesis