Coadsorption and Reaction of CO2, CO, and H2 on Ni-Fe(111) Surface

Here we compared the results of density functional theory (DFT) modeling of adsorption on Ni-Fe(111) model surface and thermoprogrammed desorption studies of species adsorbed onto Ni-Fe catalysts during hydrogenation of the carbon dioxide (CO
2
). The DFT study showed that Fe atoms are not clustered in an environment of Ni atoms and are situated randomly far from each other. We have shown that CO
2
adsorbs slightly stronger on the Ni-Fe alloy than on pure nickel. We suggest that the optimal composition of bimetallic Ni-Fe catalysts should be about 8–10 at% of Fe in Ni. This statement is confirmed by our experimental data on the thermodesorption and catalytic activity of the Ni-Fe alloys in the methanation reaction. According to the data of thermal programmed desorption mass spectroscopy, the CO
2
molecule adsorbed on the surface of the Ni
75
Fe
25
and Ni
80
Fe
20
catalysts splits into CO* and O*. Resulting strongly chemisorbed CO prevents further hydrogenation reactions on the surface of the catalyst. The modeling does not answer the question of how iron influences the methanation reaction activity and selectivity.