The UBI-QEP study of CO2 activation on the metal surfaces

The conversion and utilization of CO2 are not only an important research subject in C, 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), Fc(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 COT 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 0(a) on the Fe surface and COW and 0(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 CO and 0 adspecies. 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.