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.