Improving Electrocatalytic CO2 Reduction over Iron Tetraphenylporphyrin with Triethanolamine as a CO2 Shuttle

Delivering CO2 molecules to catalyst sites is a vital step in the CO2 reduction reaction (CO2RR). Achievements have been made to develop efficient catalysts, but few efforts have been dedicated to improving CO2 delivering in solutions. Herein, we report on electrocatalytic CO2-to-CO conversion using Fe tetraphenylporphyrin (FeTPP) as a catalyst and triethanolamine as a CO2 shuttle. Compared to ethanol, the electrocatalytic CO2RR current with triethanolamine increases by more than three times. We show that triethanolamine can effectively capture a CO2 molecule to form a zwitterionic alkylcarbonate through the collaboration between its tripodal alcohol and amine units. This alkylcarbonate can release the bound CO2 molecule for activation at the Fe site upon its interaction with FeTPP. In addition to shuttling CO2, alkylcarbonates can also provide protons to assist the C-O bond cleavage. Therefore, this work is significant to demonstrate a new strategy to improve electrocatalytic CO2RR by shuttling CO2.