CO2 Reduction on Transition Metal (Fe, Co, Ni, and Cu) Surfaces: In Comparison with Homogeneous Catalysis

Abstract

Reduction of CO2 to CO on Fe, Co, Ni, and Cu surfaces has been studied using density functional theory (DFT) methods. Three reaction steps were studied: (a) adsorption of CO2 (M + CO2 = CO2/M) (M = transition metal surface), (b) decomposition of CO2 (CO2/M = (CO + O)/M), and (c) desorption of CO ((CO + O)/M = O/M + CO). Binding energies and reaction energies were calculated using the generalized gradient approximation (GGA) via the Perdew–Burke–Ernzerhof (PBE) functional. Calculations show an interesting trend for reaction energies and total reaction barriers, as a function of metal: from Fe to Cu, reactions tend to be less exergonic; the metals earlier in the 3d series have lower total barriers for CO2 reduction. However, “overbinding” of CO2 on Fe causes a thermodynamic sink on the reaction coordinate, and Co and Ni are more favorable in terms of a smaller fluctuation in reaction energies/barriers for these elementary catalytic steps. A Bronsted–Evans–Polanyi (BEP) relationship was analyzed for C–O bond...