Reactions of CO, H2O, CO2, and H2 on the Clean and Precovered Fe(110) Surfaces – A DFT Investigation

Abstract

The reactions of CO and H2O on the clean Fe(110) surface as well as surfaces with 0.25 monolayer O, OH, and H precoverage have been computed on the basis of density functional theory (GGA-PBE). Under the considerations of the reductive nature of CO as reactant and H2 as product as well as the oxidative nature of CO2 and H2O, we have studied the potential activity of metallic iron in the water-gas shift reaction. On the clean surface, CO oxidation following the redox mechanism has a similar barrier as CO dissociation; however, CO dissociation is much more favorable thermodynamically. Furthermore, surfaces with 0.25 monolayer O, OH, and H precoverage promote CO hydrogenation, while they suppress CO oxidation and dissociation. On the surfaces with different CO and H2O ratios, CO hydrogenation is promoted. On all of these surfaces, COOH formation is not favorable. Considering the reverse reaction, CO2 dissociation is much favorable kinetically and thermodynamically on all of these surfaces, and CO2 hydrogenat...