Investigating CO2 electro-reduction mechanisms: DFT insight into earth-abundant Mn diimine catalysts for CO2 conversions over hydrogen evolution reaction, feasibility, and selectivity considerations
Murugesan Panneerselvam, Marcelo Albuquerque, Iuri Soter Viana Segtovich, Frederico W. Tavares, Luciano T. Costa
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引用次数: 0
Abstract
This study investigates the detailed mechanism of CO2 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 CO2 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 CO2 reduction and hydrogen evolution reaction thermodynamically. Furthermore, we observe that triethanolamine (TEOA) stabilizes transition states, aiding in CO2 fixation and reduction. The critical steps influencing the reaction rate involve breaking the MnC(O)–OH bond during CO2 reduction and cleaving the MnH–H–TEOA bond in the hydrogen evolution reaction. We explain the preference for CO2 conversion to CO over H2 evolution due to the higher energy barrier in forming the Mn-H2 species during H2 production. Our findings suggest the potential for tuning the electron density of the Mn center to enhance reactivity and selectivity in CO2 reduction. Additionally, we analyze potential competing reactions, focusing on electrocatalytic processes for CO2 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 H2 formation, proposing avenues for future research to expand upon these findings by using larger basis sets and exploring additional functionalized ligands.
期刊介绍:
Frontiers of Chemical Science and Engineering presents the latest developments in chemical science and engineering, emphasizing emerging and multidisciplinary fields and international trends in research and development. The journal promotes communication and exchange between scientists all over the world. The contents include original reviews, research papers and short communications. Coverage includes catalysis and reaction engineering, clean energy, functional material, nanotechnology and nanoscience, biomaterials and biotechnology, particle technology and multiphase processing, separation science and technology, sustainable technologies and green processing.