Density functional studies of the adsorption and dissociation of CO ₂ molecule on Fe(111) surface

Spin-polarized density functional theory calculation was carried out to characterize the adsorption and dissociation of CO₂ molecule on the Fe(111) surface. It was shown that the barriers for the stepwise CO₂ dissociation reaction, CO_2(g) →C_(a) + 2O _(a), are 21.73 kcal/mol (for OC-O bond activation) and 23.87 kcal/mol (for C-O bond activation), and the entire process is 35.73 kcal/mol exothermic. The rate constants for the dissociative adsorption of CO₂ have been predicted with variational RRKM theory, and the predicted rate constants, k _CO2 (in unit of cm³ molecule^-1 s^-1), can be represented by the equations 2.12 x 10^-8T^-0.842 exp(-0.258 kcal mol^-1/RT) at T = 100-1000 K. To gain insights into high catalytic activity of the Fe(111) surface, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis.