Electrochemical CO₂ Reduction to Formic Acid with High Carbon Efficiency

While much of the current research in electrochemical CO 2 reduction reaction (CO 2 RR) identified the CO 2 single-pass conversion efficiency (SPCE) as a key performance metric for the technology practical deployment, recently reported high SPCEs in CO 2 RR 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 CO 2 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% CO 2 SPCE to HCOOH at 100 mA cm –2 and demonstrated a stable operation for 100 h. To widen the applicability of the CO 2 RR technology, we demonstrate a continuous simulated flue gas (10% CO 2, 10% O 2, balance N 2 ) conversion to high-purity formic acid with CO 2 SPCE reaching more than 80% through an electrochemical sequential CO 2 capture–CO 2 reduction system.