Taming the Hydrogen-Mediated Kinetic Switch for Sulfur-Tolerant CO2 Electroreduction.

Direct electrochemical conversion of industrial flue gas offers a promising route to carbon neutrality, but it remains limited by trace sulfur dioxide (SO2, 10-400 ppm) impurities. These impurities cause rapid catalyst deactivation, particularly under the high reaction rates required for industrial application. Here, we introduce a hydrophobic molecular gate strategy to decouple impurity transport from catalyst deactivation. By regulating the interfacial water solvation structure and proton transfer pathways, this design creates a water-deficient regime to lock the kinetic switch. As a result, SO2 is isolated from the hydrogen-mediated reduction, while the transient water required for efficient CO2 conversion is preserved. When paired with a lattice-strained copper catalyst, this architecture allows a scaled-up 100 cm2 membrane electrode assembly (MEA) to operate at a total current of 20 A for over 120 h, maintaining an ethylene (C2H4) Faradaic efficiency (FE) >56% in simulated flue gas.