Direct Electrochemical Conversion of CO₂ Sorbent Solution to Formate by a Molecular Iron Catalyst

The reactive capture of CO2 (RCC) is the direct conversion of CO2 to a product that is performed in a sorbent where CO2 has been captured and stored. Here, we report that the molecular cluster electrocatalyst [Fe4N(CO)12]− (1–) can be used for RCC to produce formate with 89% faradaic efficiency. In this integrated process, a solution of monoethanolamine (MEA) and water in a ratio of 30:70 with added 0.1 M KHCO3 serves a dual purpose as the CO2 capture sorbent and the reaction solution for the electrochemical reduction of CO2. Under 1 atm of CO2, this reaction solution is buffered at pH = 7.9 as HCO3–/CO32–, and the CO2 loading is 2.67 M. Mechanistic studies performed using cyclic voltammetry indicate that the CO2 dissolved in solution serves as the substrate. Mechanistic insights into heterogeneous RCC processes are also discussed.