The field of electrocatalytic CO2 reduction is increasingly vital due to the challenges posed by climate change and the excessive release of CO2 into the atmosphere. This approach offers promising solutions for mitigating carbon emissions by producing valuable carbon-based feed chemicals. In 2016, C. Duboc and colleagues synthesized a bioinorganic complex inspired by [NiFe] hydrogenase, [NiIIFeIIL]+. This complex demonstrated remarkable efficiency in catalyzing proton reduction and converting CO2 exclusively to methane upon adsorption on a graphite surface in aqueous acidic solution. The process of physisorption preserves the structural integrity of molecules, while water plays a pivotal role as a proton source. The objective of this PhD work was to gain insight into the selective conversion of CO2 to methane using Density Functional Theory (DFT) to investigate the mechanisms at play in such chemical processes. The modelling studies provided detailed mechanistic features about how [NiFe] complex activates and converts CO2 under experimental conditions. The findings highlight the role of sulfur atoms, together with the presence of two metal atoms that help in the modulation of protonation and reduction steps and thermodynamics and preclude the formation of by-products until the end of the 8e-8 proton transfers. The work also demonstrates the influence of the graphite layer, in decreasing the CO2 insertion energy and facilitating electron transfers to the complex. Additionally, this work elucidated the details of the competing H2 evolution reaction and the mechanism of proton relay via a modified NiIIFeIICp complex, which was found to enhance the system's reactivity for H2 production.The outcomes of the present work underscore the significance of these inorganic complexes in achieving high selectivity in CO2 reduction opening the way to further improve their efficacy.​
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