(320a) Density Functional Theory Study of CO2 Electrochemical Reduction on the Fe(100) Surface

Carbon dioxide electroreduction offers the possibility of producing hydrocarbon fuels using energy from renewable sources. In this presentation, we discuss the use of density functional theory to analyze the feasibility of CO₂ electroreduction on a Fe(100) surface. Experimentally, iron is nonselective for hydrocarbon formation, despite being active for Fischer-Tropsch catalysis and thermal carbon dioxide reduction by H₂.  A simplistic analysis of low-coverage reaction intermediate energies for the paths to produce CH₄ and CH₃OH from CO₂ suggests Fe(100) could be more active than Cu(111), currently the only metallic catalyst to show selectivity towards hydrocarbon formation. We consider a series of impediments to CO₂ electroreduction on Fe(100) including O*/OH* (* denotes surface bound species) blockage of active surface sites; competitive adsorption effects of H*, CO* and C*; and iron carbide formation. Our results indicate that under CO₂ electroreduction conditions, Fe(100) is predicted to be covered in C* or CO* species, blocking any C–H bond formation. Further, bulk Fe is predicted to be unstable relative to FeC_x formation at potentials relevant to CO₂ electroreduction conditions.  The analysis of the causes of inactivity of Fe catalysts provides insight into requirements for active and selective CO₂ electroreduction catalysts.