The development of improved catalysts for electrochemical CO2 reduction is needed for building the renewable energy economy of the future. The multicenter iron carbonyl complex Fe4N(CO)12- has been shown experimentally to electrochemically reduce CO2 to formate ion (HCO2-) by transferring hydride (H-) to CO2, but many aspects of the fundamental mechanism are still unknown. Atomistic understanding of the CO2 reduction mechanism could provide answers to questions of fundamental and practical importance, such as the origin of the selectivity of the catalyst for reducing CO2 vs. H2, and the strong dependence of selectivity on the choice of solvent. Using an ab initio nanoreactor - a first-principles molecular dynamics (MD) simulation method for discovering reaction pathways - we show new mechanistic hypotheses for hydride transfer to CO2, including evidence for the chemical participation of a CO ligand that significantly reduces the activation barrier. The origin of strong dependence of the reaction thermodynamics on choice of solvent is explored using explicit-solvent ab initio MD. The simulations were made possible using a new hybrid Born-Oppenheimer / extended Lagrangian simulation method to circumvent difficulties associated with self consistent field convergence that would otherwise cause simulations to prematurely terminate. The development and validation of the method will be described.

Revealing the pathway of CO2 reduction in a multicenter iron carbonyl catalyst using an ab initio nanoreactor

253rd National Meeting (2017)

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