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. Here, we show 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 electroreduction of diluted CO2 without prior carbon capture or purification.