(320b) Thermochemical Descriptors for Unraveling Molecular Promoted CO2 Conversions

There is substantial interest in the development of renewable energy processes that convert CO₂ into more valuable products such as CO, formate, and other hydrocarbons. Independent reports in the recent literature have shown that heterocycles of nitrogen can promote selective CO₂ conversion into these products. While collaborative efforts involving theory and experiment are reaching consensus regarding some aspects these processes, numerous questions remain, including the precise mechanistic pathway that fundamentally explains the role of the heterocycles. Using first principles quantum chemistry calculations, we focus on individual reaction mechanisms involving non-substituted and substituted pyridinium, imidazolium, and their 1- and 2-electron reduced products with CO₂. Our calculated standard redox potentials, pK_as, and kinetic barrier heights are used to elucidate which chemical species may be present under in situ electrochemical conditions in solution and on metal electrodes. From this work, we rationalize different mechanistic possibilities warranting further scrutiny and give outlook for molecular-promoted (photo-)electrocatalysis.