Chlorine‐Doped SnO 2 Nanoflowers on Nickel Hollow Fiber for Enhanced CO 2 Electroreduction at Ampere‐Level Current Densities

Abstract Renewable energy‐driven electrochemical CO 2 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 CO 2 electroreduction. Here we report a novel catalytic electrode comprising chlorine‐doped SnO 2 nanoflowers arrayed on the exterior of three‐dimensional nickel hollow fibers. This electrode demonstrates exceptional electrocatalytic performance for converting CO 2 to formate, achieving a remarkable formate selectivity of 99 % and a CO 2 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 Sn 4+ species and Sn−Cl bonds, synergistically elevates the activity of CO 2 conversion. The incorporation of chlorine into SnO 2 enhances electron transport and CO 2 adsorption, substantially lowering the reaction energy barrier for the crucial intermediate *OCHO formation, and boosting the formate production.