Hierarchical design enables sufficient activated CO2 for efficient electrolysis of bicarbonate to CO

Bicarbonate electrolyzers (BCEs) offer a promising approach to reducing the energy cost of CO2 reduction by integrating upstream carbon capture and downstream electrochemical utilization. However, the faradaic efficiency of CO2 electrolysis in BCEs has been limited by insufficient activated CO2 on the catalyst surface. We report a hierarchical design strategy combining molecular and system-level innovations to ensure that there is sufficient activated CO2 on the catalyst in BCEs. At the molecular scale, we introduce a single-atom catalyst CoPc@CNT with strong CO2 adsorption to prevent CO2 desorption from the catalyst surface. Systemically, a cathodic electrolyte cross-flow strategy further enhances CO2 mass transfer. This approach achieves a faradaic efficiency exceeding 96.2% for CO at 50–300 mA cm−2, with a 36.0% and 35.3% reduction in overall energy cost compared with conventional BCEs and CO2 gas-fed electrolyzers, respectively. This innovative strategy represents a significant advancement in low-energy-consumption exhaust conversion technologies for carbon neutrality.