Structural Selectivity of CO Oxidation on Fe/N/C Catalysts

Fe/N/C electrocatalysts are attractive for electrocatalytical applications in fuel cells due to their low cost and high electrocatalytic activity. Because of its complex nature, the mechanism of CO oxidation on Fe/N/C electrocatalysts remains largely unknown. Aiming to provide insight into the mechanism of CO oxidation, we have performed extensive density functional theory calculations for the elementary steps in CO oxidation on Fe/N/C active sites, including Fe-N4 and Fe-N3 porphyrin-like carbon nanotube (T-FeN4 and T-FeN3), Fe-N4 porphyrin-like graphene (G-FeN4), and Fe-N2 nanoribbon (R-FeN2). It is found that CO adsorption and oxidation are very sensitive to the active site structures. CO adsorption is energetically more favorable than O-nu, and CO oxidation to CO2 hardly occurs on T-FeN4 and G-FeN4. In comparison, O-2 prefers to adsorb and CO can easily be oxidized on T-FeN3 and R-FeN2, suggesting the CO tolerant property of T-FeN3 and R-FeN2.