Chlorine‐Doped SnO2 Nanoflowers on Nickel Hollow Fiber for Enhanced CO2 Electroreduction at Ampere‐level Current Densities

Renewable energy‐driven electrochemical CO2 reduction has emerged as a promising technology for a sustainable future. However, achieving efficient production of storable liquid fuels at ampere‐level current densities remains a significant hurdle in the large‐scale implementation of CO2 electroreduction. Here we report a novel catalytic electrode comprising chlorine‐doped SnO2 nanoflowers arrayed on the exterior of three‐dimensional nickel hollow fibers. This electrode demonstrates exceptional electrocatalytic performance for converting CO2 to formate, achieving a remarkable formate selectivity of 99% and a CO2 single‐pass conversion rate of 93% at 2 A cm‐2. Furthermore, it exhibits excellent stability, maintaining a formate selectivity of above 94% for 520 h at a current density of 3 A cm‐2. Experimental results combined with theoretical calculations confirm that the enhanced mass transfer facilitated by the hollow fiber penetration effect, coupled with the well‐retained Sn4+ species and Sn‐Cl bonds, synergistically elevates the activity of CO2 conversion. The incorporation of chlorine into SnO2 enhances electron transport and CO2 adsorption, substantially lowering the reaction energy barrier for the crucial intermediate *OCHO formation, and boosting the formate production.