Triethanolamine Promotes Formate Selectivity in Aqueous CO2 Reduction by Immobilized Mn(bpy)(CO)3Br

Abstract

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. Amines have a range of effects on CO₂ reduction catalysis, depending on how they bind CO₂, interact with the electrolyte, and with the catalyst, among other effects. The homogeneous complex 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 was immobilized on an electrode via supramolecular interactions. The resulting material was studied in electrochemical CO₂ reduction under aqueous conditions with and without triethanolamine (TEOA) present as a CO₂ capturing agent. We demonstrated 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 36% to 60% Faraday efficiency. It showed that TEOA is an excellent additive for such catalytic systems and demonstrated the potential of expanding such catalytic systems to achieve more active and selective for aqueous CO₂ reduction.