Triethanolamine promotes formate selectivity in aqueous CO2 reduction by immobilized Mn(bpy)(CO)3Br catalyst

CO2 capture and electrochemical conversion is a sustainable and circular process to produce carbon-based chemicals. Capture of CO2 can be achieved with amine based capturing agents, which have been reported in combination with homogeneous catalysts in solution. The amines can have a range of effects on the CO2 reduction catalysis, depending on how they bind CO2, interact with the protic environment and with the catalyst, among other effects. Among the homogeneous catalysts, Mn(bpy)(CO)3Br is a well-studied catalyst that can selectively produce carbon monoxide (CO) or formate (HCOO-), depending on the conditions. It has been demonstrated that the presence of amines can promote the selective formation of formic acid. In this work, Mn(bpy)(CO)3Br is immobilized on an electrode via supramolecular interactions. The resulting material was studied in electrochemical CO2 reduction under aqueous conditions with and without triethanolamine present as a CO2 capturing agent. We demonstrate that the presence of TEOA causes two effects: (1) a two-fold increased catalytic activity in TON and (2) an increased selectivity for formate, from 25% to 60% Faraday efficiency. It shows that TEOA is an excellent additive for such catalytic systems and demonstrates the potential of expanding such catalytic systems to become even more active and selectivity for aqueous CO2 reduction.