Electrochemical CO₂ Reduction to Formic Acid with High Carbon Efficiency

While much of the current research in electrochemical CO2 reduction reaction (CO2RR) identified the CO2 single-pass conversion efficiency (SPCE) as a key performance metric for the technology practical deployment, recently reported high SPCEs in CO2RR are typically at the expense of higher cell voltages or compromised product selectivity. In this work, we use the porous solid electrolyte (PSE) reactor to achieve high CO2 SPCE to high-purity formic acid (HCOOH) while preserving the cell voltage and HCOOH Faradaic efficiency. We successfully recovered the carbon losses in the PSE system to reach a 95.1 ± 1.7% CO2 SPCE to HCOOH at 100 mA cm–2 and demonstrated a stable operation for 100 h. To widen the applicability of the CO2RR technology, we demonstrate a continuous simulated flue gas (10% CO2, 10% O2, balance N2) conversion to high-purity formic acid with CO2 SPCE reaching more than 80% through an electrochemical sequential CO2 capture–CO2 reduction system.