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oai:figshare.com:article/34034143 2026-09-30T17:06:23Z category_1 category_4 category_12 category_19 category_21 category_272 category_873 category_64 portal_63 item_type_6 month_year_09_2026

Pseudo-Jahn–Teller Effect-Mediated Medium-Spin (S = 3/2) Fe for Robust Fe–N Bonds in Acidic Oxygen Reduction and Fuel Cells Yan Yan (208529) Dongping Xue (11524843) Mingkai Liu (1829086) Jiawei Duan (12436465) Tianyu Gong (6410594) Yue Yu (260119) Song Xue (316115) Xinduo Wei (21253599) Lintao Jiang (21983352) Su Jiang (5315156) Guohong Fan (23814763) Hongliang Li (122229) Jia-Nan Zhang (3341624) Jie Zeng (315334) Biophysics Biochemistry Cell Biology Pharmacology Biotechnology Environmental Sciences not elsewhere classified Chemical Sciences not elsewhere classified Cancer structural stability translates shortened bond length peak power density oxygen reduction reaction new chemical strategy jahn – teller acidic oxygen reduction acidic operating conditions 720 mw cm fuel cells proton 4 </ sub 2 </ sub suppressing proton vs 26 require efficient rapid demetalation promising candidates practical application pair electrons orr ). nitrogen ligands motif triggers induced demetalation findings establish durable platinum current retention cathode catalysts 99 å 96 å 7 %). 60 v 000 cycles Proton-exchange membrane fuel cells (PEMFCs) require efficient and durable platinum-group-metal-free (PGM-free) cathode catalysts for the oxygen reduction reaction (ORR). Iron–nitrogen–carbon (Fe–N–C) materials are promising candidates, but their practical application is hindered by rapid demetalation of Fe sites under acidic operating conditions. Here, we show that introducing a <i>p-</i>block metal (Bi) adjacent to the FeN₄ motif triggers a pseudo-Jahn–Teller (p-J-T) distortion. This distortion stabilizes a medium-spin Fe(III) configuration (S = 3/2) with an empty <i>d</i>_x²–y² orbital. This empty orbital accepts lone-pair electrons from the nitrogen ligands, strengthening the Fe–N bond and suppressing proton-induced demetalation. The resulting FeBi–N–C catalyst exhibits a dramatically strengthened Fe–N bond, as evidenced by a shortened bond length (from 1.99 Å to 1.96 Å) and a 3-fold higher Fe retention after 20,000 cycles (78.8% vs 26.7%). This structural stability translates into a peak power density of 720 mW cm^–2 in H₂–O₂ PEMFCs and 90% current retention after 150 h at 0.60 V. Our findings establish the p-J-T effect as a new chemical strategy to stabilize metal–nitrogen bonds against acid-induced demetalation. 2026-09-30T00:00:00Z Text Journal contribution 10.1021/jacs.6c09985.s001 https://figshare.com/articles/journal_contribution/Pseudo-Jahn_Teller_Effect-Mediated_Medium-Spin_S_3_2_Fe_for_Robust_Fe_N_Bonds_in_Acidic_Oxygen_Reduction_and_Fuel_Cells/34034143 CC BY-NC 4.0