Exploring the Non-Innocence of Inorganic Complex Ligands in (photo-) Electrochemical CO2 Reductions

Carbon neutral energy cycles necessitate the conversion of CO₂ into other compounds.¹ However, the unfavorable thermodynamics and slow kinetics of multiple proton and electron transfers makes CO₂ conversion difficult. Improved insight into these processes would help elucidate reaction mechanisms that guide the development of improved and versatile photo- and electro-catalysts.² Recent experiments have demonstrated that inorganic Ru complexes can catalyze the photo- and electro-chemical reduction of CO2 into methanol.³ These reactions involve aqueous phase aromatic N-heterocycles (ANH) in addition to complexes that contain ANH ligands themselves (e.g. phenanthroline). We previously developed⁴ a set of thermodynamic descriptors from quantum chemistry calculations to describe electrochemical conditions at which ANH molecules participate in energetically efficient proton and electron transfers. In this study, we report our latest efforts to provide insight into the mechanism of Ru catalyzed CO2 reduction using Pourbaix diagram descriptors. Although transition metal complexes are normally assumed to be electrochemically stable, our calculations indicate that certain environments may result in hydride transfers facilitated via the ligands of the inorganic complexes.

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