This study investigates the detailed mechanism of CO_(2) conversion to CO using the manganese(I) diimine electrocatalyst [Mn(pyrox)(CO)3Br], synthesized by Christoph Steinlechner and coworkers. Employing density funct...This study investigates the detailed mechanism of CO_(2) conversion to CO using the manganese(I) diimine electrocatalyst [Mn(pyrox)(CO)3Br], synthesized by Christoph Steinlechner and coworkers. Employing density functional theory calculations, we thoroughly explore the electrocatalytic pathway of CO_(2) reduction alongside the competing hydrogen evolution reaction. Our analysis reveals the significant role of diimine nitrogen coordination in enhancing the electron density of the Mn center, thereby favoring both CO_(2) reduction and hydrogen evolution reaction thermodynamically. Furthermore, we observe that triethanolamine (TEOA) stabilizes transition states, aiding in CO_(2) fixation and reduction. The critical steps influencing the reaction rate involve breaking the MnC(O)–OH bond during CO_(2) reduction and cleaving the MnH–H–TEOA bond in the hydrogen evolution reaction. We explain the preference for CO_(2) conversion to CO over H_(2) evolution due to the higher energy barrier in forming the Mn-H_(2) species during H_(2) production. Our findings suggest the potential for tuning the electron density of the Mn center to enhance reactivity and selectivity in CO_(2) reduction. Additionally, we analyze potential competing reactions, focusing on electrocatalytic processes for CO_(2) reduction and evaluating “protonation-first” and “reduction-first” pathways through density functional theory calculations of redox potentials and Gibbs free energies. This analysis indicates the predominance of the “reduction-first” pathway in CO production, especially under high applied potential conditions. Moreover, our research highlights the selectivity of [Mn(pyrox)(CO)3Br] toward CO production over HCOO– and H_(2) formation, proposing avenues for future research to expand upon these findings by using larger basis sets and exploring additional functionalized ligands.展开更多
文摘This study investigates the detailed mechanism of CO_(2) conversion to CO using the manganese(I) diimine electrocatalyst [Mn(pyrox)(CO)3Br], synthesized by Christoph Steinlechner and coworkers. Employing density functional theory calculations, we thoroughly explore the electrocatalytic pathway of CO_(2) reduction alongside the competing hydrogen evolution reaction. Our analysis reveals the significant role of diimine nitrogen coordination in enhancing the electron density of the Mn center, thereby favoring both CO_(2) reduction and hydrogen evolution reaction thermodynamically. Furthermore, we observe that triethanolamine (TEOA) stabilizes transition states, aiding in CO_(2) fixation and reduction. The critical steps influencing the reaction rate involve breaking the MnC(O)–OH bond during CO_(2) reduction and cleaving the MnH–H–TEOA bond in the hydrogen evolution reaction. We explain the preference for CO_(2) conversion to CO over H_(2) evolution due to the higher energy barrier in forming the Mn-H_(2) species during H_(2) production. Our findings suggest the potential for tuning the electron density of the Mn center to enhance reactivity and selectivity in CO_(2) reduction. Additionally, we analyze potential competing reactions, focusing on electrocatalytic processes for CO_(2) reduction and evaluating “protonation-first” and “reduction-first” pathways through density functional theory calculations of redox potentials and Gibbs free energies. This analysis indicates the predominance of the “reduction-first” pathway in CO production, especially under high applied potential conditions. Moreover, our research highlights the selectivity of [Mn(pyrox)(CO)3Br] toward CO production over HCOO– and H_(2) formation, proposing avenues for future research to expand upon these findings by using larger basis sets and exploring additional functionalized ligands.
