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

Authors: 
Bernstein, N., Pennsylvania State University
Janik, M. J., Pennsylvania State University

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 FeCx 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.
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