Alternating substrate/ligand-metal coordination enables a low-energy pathway for C-O bond cleavage in the electrocatalytic reduction of carbon dioxide

21 May 2021, Version 2
This content is a preprint and has not undergone peer review at the time of posting.


Molecular electrocatalysts for CO2-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO2 reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO2 to form [Ru-CO2]0, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [Ru-CO2CO2]0,c, by intramolecular cyclization of a linear [Ru-CO2CO2]0 species that is formed from [Ru-CO2]0 and a second equivalent of CO2. [Ru-CO2CO2]0,c is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex Ru2+. The calculated activation barrier for C-O bond cleavage in [Ru-CO2CO2]-1,c is dramatically decreased to 10.5 kcal mol-1 from 60 kcal mol-1, the latter required for C-O bond cleavage in the linear intermediate [Ru-CO2CO2]0. The intermediates are characterized experimentally by FT-IR and 13C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).


Molecular Electrocatalysis
catalytic mechanism
ruthenium polypyridyl complexes
metallacyclic intermediates
spectroscopy characterization
DFT Calculations
Small molecule activation
CO2 reduction

Supplementary materials

Agarwala et al ESI v2


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