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 CO (CORR) 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 CO, while the available real sources of CO are gases coming out from industrial plants and containing a low share of CO, 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 CORR to formic acid using a quasi-flue gas (5-10% CO and 100 ppm NO or 50 ppm SO) with substantial selectivity. This is made possible thanks to the modification of the cathode surface with a positively charged imidazolium layer, which greatly favors CORR over competing reactions, proton, NO, and SO reductions. These results highlight the potential of combining molecular catalysis and electrode surface modification for the electroreduction of diluted CO without prior carbon capture or purification.