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.