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.