Exploring oxygen depolarized cathodes for zero-gap CO2 electrolysis

The electrochemical reduction of CO₂ to CO represents a pivotal step towards electrification of industries and Power-to-X strategies, however, industrial implementation remains limited by electrode flooding, salt accumulation, and unstable operation at high current densities. Herein, we demonstrate the use of oxygen depolarised cathodes (ODC), that are established and well-proven in chlor-alkali electrolysis, as a robust alternative electrode for CO₂ electroreduction under industrially relevant conditions. Notably, ODC exhibits superior mechanical durability, electrical conductivity, and flooding resistance enabling stable operation in membrane electrode assembly configuration over a wide current density range. By conducting a systematic tuning of both reactor temperature and CO₂ humidification, we identify that a delicate balance of water management and cation transport is critical for sustained performance. Stable operation was achieved at 100 mA/cm² and 200 mA/cm² with CO Faradaic efficiencies of 97% and 95% respectively over 24 h using a 0.1 M KHCO₃ anolyte. At 300 mA/cm², an intermittent electrolysis strategy with periodic current relaxation extended operation to 100 h maintaining 70% CO selectivity. These findings demonstrate the feasibility of using ODC as scalable and durable cathode for CO₂ electrolysis to CO and adapting operational conditions to achieve the industrially relevant deployment.