Formate Production from Simulated Quasi-Flue Gas Combining a Molecular Catalyst and a Modified Electrode

Molecular metal complexes form an important class of catalysts for the electroreduction of CO₂ (CO₂RR) to carbon monoxide (CO) or formic acid (HCOOH), key processes in the context of the requested exploration of novel sources of carbon, alternative to fossil fuels. Research studies are most generally carried out with pure gas streams of CO₂, while the available real sources of CO₂ are gases coming out from industrial plants and containing a low share of CO₂, and a great diversity of impurities including nitrogen and sulfur oxides. Herein, it is shown that a molecular catalyst, [Rh(bpy)(Cp*)Cl]Cl (bpy = bipyridine, Cp* = pentamethylcyclopentadienyl), catalyzes CO₂RR to formic acid using a quasi-flue gas (5-10% CO₂ and 100 ppm NO₂ or 50 ppm SO₂) with substantial selectivity. This is made possible thanks to the modification of the cathode surface with a positively charged imidazolium layer, which greatly favors CO₂RR over competing reactions, proton, NO₂, and SO₂ reductions. These results highlight the potential of combining molecular catalysis and electrode surface modification for the electroreduction of diluted CO₂ without prior carbon capture or purification.