Spin‐State Modulation of Atomic Iron Sites Enables Efficient CO 2 Electroreduction in Acid Medium

作者：Shanhe Gong, Yanjie Zhai, Qing Xia, Xiaohong Han, Weisong Li, Ying, J. S. Wu, Yingying Zhou, Xiaojie She, Zheng Wang, Chao Wu, Xiaomeng Lv, Xiao Zhang, Shu Ping Lau · 发表于：Angewandte Chemie International Edition · 年份：2026 · DOI：10.1002/anie.9239759 · 被引用次数：1 · 研究领域：CO2 Reduction Techniques and Catalysts、Metalloenzymes and iron-sulfur proteins、Electrocatalysts for Energy Conversion

ABSTRACT Electrochemical carbon dioxide (CO 2 ) reduction (CO 2 RR) in acidic conditions not only enables high CO 2 utilization but also reduces the formation of interfacial (bi)carbonate. However, the acidic environment tends to favor the competing hydrogen evolution reaction (HER), which lowers the overall energy efficiency of CO 2 reduction. Here, we use axial oxygen coordination to tune the spin state of iron‐nitrogen‐carbon sites, shifting from the low‐spin (LS, t 2g 5 e g 0 ) to the medium‐spin (MS, t 2g 4 e g 1 ) state. Experimental results and theoretical simulations show that this medium‐spin structure results in spin‐electron filling of the 𝜎∗ orbital, weakening the interfacial attraction of H 3 O + , significantly inhibiting HER, and reducing the *CO desorption energy; thus, CO 2 RR performance in acidic media is greatly improved. The designed Fe−N 4 O structure achieves a mass activity of 76.17 A mg Fe −1 and CO current densities of approximately 335 mA cm −2 in acidic conditions, far exceeding those of Fe−N 4 (7.86 mA cm −2 ). Meanwhile, the catalyst reaches a high j CO of 324.55 mA cm −2 , 80.97% CO 2 utilization efficiency, and an energy efficiency of 36.89% in a self‐designed proton‐exchange‐membrane porous‐solid‐electrolyte reactor. This work highlights the spin‐manipulation mechanism for enhancing acidic CO 2 RR performance.