Abstract
Electrochemical carbon capture offers a sustainable route to mitigate CO2 emissions, but practical deployment is often limited by modest capture rates and system complexity. Here we report a saline-water electrolysis strategy that simultaneously captures CO2 and converts it to sodium bicarbonate (NaHCO3 ) without external chemical additives. Hydroxide ions (OH-) generated in situ at the cathode via the hydrogen-evolution reaction (HER) enable rapid CO2 absorption and selective conversion to NaHCO3 by maintaining the catholyte at pH 8-9, consistent with thermodynamic speciation. In simulated flue gas, the system delivers a CO2 capture rate of 5.27 CO2 cm(-2) h(-1) (55.6 kg(CO2) m(-2) day(-1)) at 300 mA cm(-2), >99.5% capture efficiency, >90% faradaic efficiency, and energy consumption as low as 87 kJ mol CO2 -1 (1.98 GJ CO2 (-1)). The process is tolerant to sulfur dioxide (SO2), maintaining similar to 85% NaHCO3 conversion for >240 h with 1.0% SO(2)in the feed. Using pure water as the catholyte enables direct production of high-purity NaHCO3 , enhancing operational flexibility. Techno-economic analysis indicates capture costs with US$90.3 per t(CO2 )when co-located with a desalination facility and low-cost electricity, while considering the revenues from products NaHCO3 , H-2 and Cl-2 can further improve the economics. This multifunctional, impurity-resistant, and renewable-compatible approach offers a practical, scalable pathway for industrial CO2 capture and mineralization.