Dual-site confinement strategy tuning Fe-N-C electronic structure to enhance oxygen reduction performance in PEM fuel cells

doi:10.1016/S1872-2067(25)64804-2

Abstract

Abstract:

Single atomic iron-nitrogen-carbon (Fe-N-C) have emerged as promising catalysts for the oxygen reduction reaction (ORR), however, the insufficient activity and stability hindered their application in proton exchange membrane fuel cells (PEMFCs). Simultaneously regulating the coordination environments and local carbon structures of atomic Fe-N sites is essential to boost Fe-N-C’s ORR performance. In this study, a dual-site confinement strategy is proposed to precisely incorporate Mn single atoms at adjacent Fe sites to form active and stable FeMn-N catalytic structure within a graphitic carbon matrix, which is achieved via heat treatment of MnFe₂O₄ nanoparticles embedded ZIF-8. Experimental and theoretical calculations demonstrate that the incorporation of Mn atoms could effectively modulate the electronic structure of Fe atoms, enhance Fe-N bond stability and reduce Fe site dissolution. Moreover, in-situ Raman and in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy spectra suggest that Mn doping could suppress Fenton reactions by optimizing the ORR pathway through facilitating *OH intermediate desorption and circumventing *OOH intermediate formation. The synthesized FeMn-N-C exhibits better catalytic activity than commercial Pt/C catalysts (E_1/2 of 0.885 vs. 0.855 V) and maintains stable cycling operation over 20000 cycles with a small E_1/2 gap of 95 mV. When applied in PEMFCs, FeMn-N-C achieves a high peak power density of 899.9 mW cm^-2 and retains 66.4% of its initial performance after 20000 square-wave cycles, which is superior to Fe-N-C catalyst. This study provides an innovative design strategy for developing high-performance, long-lasting ORR catalysts for PEMFCs.

Key words: Dual-atom catalyst, Electrocatalysis, Oxygen reduction reaction, Catalytic activity and stability, Proton exchange membrane fuel cell

Wenbo Shi, Kai Zhu, Xiaogang Fu, Chenhong Liu, Yang Yuan, Jialiang Pan, Qing Zhang, Zhengyu Ba. Dual-site confinement strategy tuning Fe-N-C electronic structure to enhance oxygen reduction performance in PEM fuel cells[J]. Chinese Journal of Catalysis, 2026, 80: 293-303.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(25)64804-2

https://www.cjcatal.com/EN/Y2026/V80/I1/293

Figures/Tables 5

Fig. 1. (a) Schematic diagram of the FeMn-N-C catalyst synthesis. SEM (b) and TEM (c) images of FeMn-N-C. (d) HRTEM image of the micro carbon structure. (e) HAADF-STEM atomic image. (f) EDS mapping of FeMn-N-C. (g) XRD patterns.

Fig. 2. High-resolution Fe 2p (a), Mn 2p (b), and N 1s (c) XPS spectra of FeMn-N-C, Fe-N-C and Mn-N-C. (d) Normalized Fe K-edge XANES spectra of FeMn-N-C, Fe-N-C, FePc, Fe2O3, and Fe foil. (e) Normalized Mn K-edge XANES spectra of FeMn-N-C, Mn-N-C, Mn2O3, MnPc, and Mn foil. (f) k3-weighted Fe K-edge EXAFS spectra of FeMn-N-C, Fe-N-C, FePc, Fe2O3, and Fe foil. (g) k3-weighted Mn K-edge EXAFS spectra of FeMn-N-C, Mn-N-C, Mn2O3, MnPc, and Mn foil. (h) EXAFS fitting results in R space of Fe in FeMn-N-C. (i) EXAFS fitting results in R space of Mn in FeMn-N-C. (j) Fe K‐edge wavelet transform of EXAFS for FeMn-N-C, Fe-N-C and FePc.

Fig. 3. (a) LSV curves of FeMn-N-C, Fe-N-C, Mn-N-C, and Pt/C in 0.5 mol L-1 H2SO4. (b) Comparison of J, half-wave potential for different catalysts. (c) Tafel slopes of the synthesized catalysts and Pt/C in 0.5 mol L-1 H2SO4. (d) The H2O2 yield and n for FeMn-N-C and reference samples. (e) LSV curves of FeMn-N-C after different CV cycles. (f) LSV curves of Fe-N-C after different CV cycles. (g) Polarization and power density plots of H2-O2 PEMFCs with FeMn-N-C, Fe-N-C, and Pt/C as cathode catalysts. (h) Polarization and power density plots of H2-O2 PEMFCs with FeMn-N-C as the cathode catalyst after different CV cycles. (i) Polarization and power density plots of H2-O2 PEMFCs with Fe-N-C as the cathode catalyst after different CV cycles.

Fig. 4. (a) In-situ Raman spectra of the FeMn-N-C catalyst. (b) In-situ Raman spectra of the Fe-N-C catalyst. (c) 3D contour plot of in-situ Raman spectra for the FeMn-N-C catalyst. (d) In-situ ATR-SEIRAS spectra of the FeMn-N-C catalyst. (e) In-situ ATR-SEIRAS spectra of the Fe-N-C catalyst. (f) 2D contour plot of in situ ATR-SEIRAS spectra for the FeMn-N-C catalyst.

Fig. 5. (a) Free energy diagrams of ORR on FeMnN6-C and FeN4-C. (b) Charge density distribution (top and side views) of FeMnN6-C and FeN4-C. (c) Structural charge difference between FeMnN6-C and FeN4-C. (d) Electron localization function (ELF) plots of FeMnN6-C and FeN4-C. (e) Crystal Orbital Hamiltonian Population (COHP) spectra of FeMnN6-C and FeN4-C. (f,g) Projected d-band center profiles of the dz2 and dx2?y2 orbitals for FeMnN?-C and FeN4-C.

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