Sulfur‐Doped Bi ₂ O ₃ Nanorods with Asymmetric S−Bi−O Active Sites for Highly Efficient Electrosynthesis of Formic Acid

ABSTRACT The increasing atmospheric CO 2 concentration, primarily due to the overuse of fossil fuels, has emerged as a critical climate concern. Bismuth oxide (Bi 2 O 3 )‐based catalysts have shown promise in selectively converting CO 2 to formic acid (HCOOH), attributed to their active Bi─O bonds. Herein, we present a sulfur‐doped Bi 2 O 3 catalyst synthesized via a facile solvothermal and annealing approach. The incorporation of sulfur heteroatoms introduces asymmetric S─Bi─O active sites, which effectively stabilize the Bi─O bonds, thereby significantly enhancing catalytic activity and stability. The optimal Bi 2 O 3 ‐S‐2 catalyst exhibits a high faradaic efficiency of 91.8% for HCOOH at −0.7 V vs. RHE in H‐type cell. Moreover, Bi 2 O 3 ‐S‐2 maintains a high selectivity of 95% across a wide potential range from −0.7 to −1.1 V vs. RHE, with a peak current density reaching approximately −300 mA cm −2 in flow cell. Furthermore, in situ spectroscopy and theoretical calculations reveal that sulfur incorporation modulates the adsorption of CO 2 * and OCHO*, thus accelerating the CO 2 reduction kinetics. This work paves the way for the rational design of element‐doped metal‐based electrocatalysts for efficient CO 2 reduction.