Issue

Vol. 18 (2026)

Entropy-Modulated Oxide–Metal Catalyst Architectures for Direct Ammonia Protonic Ceramic Fuel Cells

https://doi.org/10.1007/s40820-026-02194-9
Dongyeon Kim
KAIST InnoCORE PRISM‑AI Center, KAIST, Daejeon, Republic of Korea
Dong Jae Park
Hydrogen Energy Materials Center, Korea Institute of Ceramic Engineering and Technology (KICET), Jinju‑Si, Gyeongsangnam‑Do, Republic of Korea
Incheol Jeong
Resources Utilization Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea
Seeun Oh
Department of Mechanical Engineering, KAIST, Daejeon, Republic of Korea
Hyeonggeun Kim
Department of Mechanical Engineering, KAIST, Daejeon, Republic of Korea
Mincheol Lee
Department of Mechanical Engineering, KAIST, Daejeon, Republic of Korea
Sang Won Lee
Hydrogen Energy Materials Center, Korea Institute of Ceramic Engineering and Technology (KICET), Jinju‑Si, Gyeongsangnam‑Do, Republic of Korea
Kangyong Lee
Department of Mechanical Engineering, KAIST, Daejeon, Republic of Korea
Daehan Chung
Department of Mechanical Engineering, KAIST, Daejeon, Republic of Korea
Ki‑Min Roh
Resources Utilization Research Center, Korea Institute of Geoscience and Mineral Resources (KIGAM), Daejeon, Republic of Korea
Joongmyeon Bae
Department of Mechanical Engineering, KAIST, Daejeon, Republic of Korea
Tae Ho Shin
Hydrogen Energy Materials Center, Korea Institute of Ceramic Engineering and Technology (KICET), Jinju‑Si, Gyeongsangnam‑Do, Republic of Korea
Kang Taek Lee
KAIST InnoCORE PRISM‑AI Center, KAIST, Daejeon, Republic of Korea

Corresponding Author: Kang Taek Lee

leekt@kaist.ac.kr

Nano-Micro Letters, Vol. 18 (2026), Article Number: 335

Abstract

Protonic ceramic fuel cells (PCFCs) operating on NH3 present a promising carbon-free energy pathway, yet their performance is often constrained by limited catalytic activity and degradation of conventional Ni-based anodes. Here, we report a high-entropy perovskite catalyst, Sr2Fe1Mo0.2Mn0.2Cr0.2Cu0.2Ni0.2O6-δ (SFMMCCN), employed as an anode catalyst layer in direct ammonia-fed PCFCs. Upon reduction, SFMMCCN undergoes in situ exsolution of Ni–Fe–Cu alloy nanoparticles within a stable oxide matrix. This architecture provides synergistic enhancement of NH3 adsorption and decomposition through the combined effects of abundant surface acid sites and catalytically active alloy interfaces. As a result, the SFMMCCN cell achieves a record peak power density of 2.04 W cm⁻2 at 700 °C and demonstrates excellent operational stability for over 255 h at 600 °C under NH3 fuel. Compared to a bare cell, it exhibits significantly reduced polarization resistance and effectively suppresses Ni coarsening. Density functional theory calculations reveal that the high-entropy oxide framework, together with the exsolved Ni–Fe–Cu alloy, lowers the energy barriers for NH3 decomposition, thereby accelerating overall catalytic kinetics. These findings highlight entropy-controlled oxide–metal architectures as a powerful strategy to achieve both high performance and durability in NH3-fueled electrochemical systems, offering a viable pathway toward scalable and efficient hydrogen-based power generation.


Highlights:
1 Entropy-modulated oxide–metal catalyst exsolving Ni–Fe–Cu alloy nanoparticles from a high-entropy perovskite matrix enables efficient and durable ammonia decomposition.
2 Density functional theory calculations reveal that the high-entropy oxide framework facilitates cation exsolution and lowers the kinetic barriers for NH3 decomposition; additionally, the exsolved Ni–Fe–Cu alloy nanoparticles exhibit markedly higher catalytic activity than single-metal surfaces.
3 Direct ammonia protonic ceramic fuel cells (DA-PCFCs) incorporating the Sr2Fe1Mo0.2Mn0.2Cr0.2Cu0.2Ni0.2O6-δ (SFMMCCN) catalyst layer achieve a record-high power density of 2.04 W cm−2 at 700 °C with stable operation for over 255 h under NH3 fuel, demonstrating the effectiveness of the entropy-modulated catalyst in designing durable and high-performance DA-PCFCs for carbon-free ammonia-to-power technologies.

Keywords

Protonic ceramic fuel cells (PCFCs) Ammonia High-entropy perovskite Anode catalyst layer Density functional theory
Kim, Dongyeon, Dong Jae Park, Incheol Jeong, Seeun Oh, Hyeonggeun Kim, Mincheol Lee, Sang Won Lee, Kangyong Lee, Daehan Chung, Ki‑Min Roh, Joongmyeon Bae, Tae Ho Shin, and Kang Taek Lee. 2026. “Entropy-Modulated Oxide–Metal Catalyst Architectures for Direct Ammonia Protonic Ceramic Fuel Cells”. Nano-Micro Letters 18 (April):335. https://doi.org/10.1007/s40820-026-02194-9.
Download Citation
Endnote/Zotero/Mendeley (RIS)
BibTeX
References
  1. I. Staffell, D. Scamman, A. Velazquez Abad, P. Balcombe, P.E. Dodds et al., The role of hydrogen and fuel cells in the global energy system. Energy Environ. Sci. 12(2), 463–491 (2019). https://doi.org/10.1039/c8ee01157e
  2. C. Duan, R.J. Kee, H. Zhu, C. Karakaya, Y. Chen et al., Highly durable, coking and sulfur tolerant, fuel-flexible protonic ceramic fuel cells. Nature 557(7704), 217–222 (2018). https://doi.org/10.1038/s41586-018-0082-6
  3. A.M. Abdalla, S. Hossain, O.B. Nisfindy, A.T. Azad, M. Dawood et al., Hydrogen production, storage, transportation and key challenges with applications: a review. Energy Convers. Manag. 165, 602–627 (2018). https://doi.org/10.1016/j.enconman.2018.03.088
  4. L. Schlapbach, A. Züttel, Hydrogen-storage materials for mobile applications. Nature 414(6861), 353–358 (2001). https://doi.org/10.1038/35104634
  5. D. Ding, Y. Zhang, W. Wu, D. Chen, M. Liu et al., A novel low-thermal-budget approach for the co-production of ethylene and hydrogen via the electrochemical non-oxidative deprotonation of ethane. Energy Environ. Sci. 11(7), 1710–1716 (2018). https://doi.org/10.1039/c8ee00645h
  6. A. Klerke, C.H. Christensen, J.K. Nørskov, T. Vegge, Ammonia for hydrogen storage: challenges and opportunities. J. Mater. Chem. 18(20), 2304 (2008). https://doi.org/10.1039/b720020j
  7. B. Wang, T. Li, F. Gong, M.H.D. Othman, R. Xiao, Ammonia as a green energy carrier: electrochemical synthesis and direct ammonia fuel cell - a comprehensive review. Fuel Process. Technol. 235, 107380 (2022). https://doi.org/10.1016/j.fuproc.2022.107380
  8. D. Kim, J.W. Park, M.S. Chae, I. Jeong, J.H. Park et al., An efficient and robust lanthanum strontium cobalt ferrite catalyst as a bifunctional oxygen electrode for reversible solid oxide cells. J. Mater. Chem. A 9(9), 5507–5521 (2021). https://doi.org/10.1039/d0ta11233j
  9. H. Zhang, Y. Zhou, K. Pei, Y. Pan, K. Xu et al., An efficient and durable anode for ammonia protonic ceramic fuel cells. Energy Environ. Sci. 15(1), 287–295 (2022). https://doi.org/10.1039/d1ee02158c
  10. M. Liang, Y. Song, B. Xiong, D. Liu, D. Xue et al., In situ exsolved CoFeRu alloy decorated perovskite as an anode catalyst layer for high-performance direct-ammonia protonic ceramic fuel cells. Adv. Funct. Mater. 34(48), 2408756 (2024). https://doi.org/10.1002/adfm.202408756
  11. J. Yang, A.F.S. Molouk, T. Okanishi, H. Muroyama, T. Matsui et al., A stability study of Ni/yttria-stabilized zirconia anode for direct ammonia solid oxide fuel cells. ACS Appl. Mater. Interfaces 7(51), 28701–28707 (2015). https://doi.org/10.1021/acsami.5b11122
  12. Z. Wan, Y. Tao, J. Shao, Y. Zhang, H. You, Ammonia as an effective hydrogen carrier and a clean fuel for solid oxide fuel cells. Energy Convers. Manag. 228, 113729 (2021). https://doi.org/10.1016/j.enconman.2020.113729
  13. M. Liang, J. Kim, X. Xu, H. Sun, Y. Song et al., Electricity-to-ammonia interconversion in protonic ceramic cells: advances, challenges and perspectives. Energy Environ. Sci. 18(8), 3526–3552 (2025). https://doi.org/10.1039/D4EE06100D
  14. M.Z. Khan, R.-H. Song, A. Hussain, S.-B. Lee, T.-H. Lim et al., Effect of applied current density on the degradation behavior of anode-supported flat-tubular solid oxide fuel cells. J. Eur. Ceram. Soc. 40(4), 1407–1417 (2020). https://doi.org/10.1016/j.jeurceramsoc.2019.11.017
  15. Z. Liu, H. Di, D. Liu, G. Yang, Y. Zhu et al., Boosting ammonia-fueled protonic ceramic fuel cells with RuFe nanop exsolution: enhanced performance via secondary redox treatment. Adv. Funct. Mater. 35(15), 2420214 (2025). https://doi.org/10.1002/adfm.202420214
  16. F. He, Q. Gao, Z. Liu, M. Yang, R. Ran et al., A new Pd doped proton conducting perovskite oxide with multiple functionalities for efficient and stable power generation from ammonia at reduced temperatures. Adv. Energy Mater. 11(19), 2003916 (2021). https://doi.org/10.1002/aenm.202003916
  17. H. Zhang, K. Xu, Y. Xu, F. He, F. Zhu et al., In situ formed catalysts for active, durable, and thermally stable ammonia protonic ceramic fuel cells at 550 °C. Energy Environ. Sci. 17(10), 3433–3442 (2024). https://doi.org/10.1039/d4ee00219a
  18. F. Schüth, R. Palkovits, R. Schlögl, D.S. Su, Ammonia as a possible element in an energy infrastructure: catalysts for ammonia decomposition. Energy Environ. Sci. 5(4), 6278–6289 (2012). https://doi.org/10.1039/c2ee02865d
  19. H. Zhang, R. Xiong, Z. Chen, Z. Cheng, J. Huang et al., Efficient and robust nanocomposite cermet anode with strong metal–oxide interaction for direct ammonia solid oxide fuel cells. Adv. Funct. Mater. 35(38), 2501223 (2025). https://doi.org/10.1002/adfm.202501223
  20. H. Zhang, K. Xu, F. He, F. Zhu, Y. Zhou et al., Challenges and advancements in the electrochemical utilization of ammonia using solid oxide fuel cells. Adv. Mater. 36(33), 2313966 (2024). https://doi.org/10.1002/adma.202313966
  21. N. Tsvetkov, D. Kim, I. Jeong, J.H. Kim, S. Ahn et al., Advances in materials and interface understanding in protonic ceramic fuel cells. Adv. Mater. Technol. 8(20), 2201075 (2023). https://doi.org/10.1002/admt.202201075
  22. Y. Pan, H. Zhang, K. Xu, Y. Zhou, B. Zhao et al., A high-performance and durable direct NH3 tubular protonic ceramic fuel cell integrated with an internal catalyst layer. Appl. Catal. B Environ. 306, 121071 (2022). https://doi.org/10.1016/j.apcatb.2022.121071
  23. Y.-F. Sun, Y.-Q. Zhang, B. Hua, Y. Behnamian, J. Li et al., Molybdenum doped Pr0.5Ba0.5MnO3−δ (Mo-PBMO) double perovskite as a potential solid oxide fuel cell anode material. J. Power. Sources 301, 237–241 (2016). https://doi.org/10.1016/j.jpowsour.2015.09.127
  24. F. He, M. Hou, Z. Du, F. Zhu, X. Cao et al., Self-construction of efficient interfaces ensures high-performance direct ammonia protonic ceramic fuel cells. Adv. Mater. 35(42), 2304957 (2023). https://doi.org/10.1002/adma.202304957
  25. S. Oh, D. Kim, H.J. Ryu, K.T. Lee, A novel high-entropy perovskite electrolyte with improved proton conductivity and stability for reversible protonic ceramic electrochemical cells. Adv. Funct. Mater. 34(17), 2311426 (2024). https://doi.org/10.1002/adfm.202311426
  26. Y. Wang, M.J. Robson, A. Manzotti, F. Ciucci, High-entropy perovskites materials for next-generation energy applications. Joule 7(5), 848–854 (2023). https://doi.org/10.1016/j.joule.2023.03.020
  27. D. Kim, I. Jeong, S. Ahn, S. Oh, H.-N. Im et al., On the role of bimetal-doped BaCoO3−δ perovskites as highly active oxygen electrodes of protonic ceramic electrochemical cells. Adv. Energy Mater. 14(14), 2304059 (2024). https://doi.org/10.1002/aenm.202304059
  28. K. Okura, T. Okanishi, H. Muroyama, T. Matsui, K. Eguchi, Ammonia decomposition over nickel catalysts supported on rare-earth oxides for the on-site generation of hydrogen. ChemCatChem 8(18), 2988–2995 (2016). https://doi.org/10.1002/cctc.201600610
  29. G. Kresse, J. Furthmüller, Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. Phys. Rev. B 54(16), 11169–11186 (1996). https://doi.org/10.1103/physrevb.54.11169
  30. H.J. Monkhorst, J.D. Pack, Special points for Brillouin-zone integrations. Phys. Rev. B 13(12), 5188–5192 (1976). https://doi.org/10.1103/physrevb.13.5188
  31. D. Marrocchelli, N.H. Perry, S.R. Bishop, Understanding chemical expansion in perovskite-structured oxides. Phys. Chem. Chem. Phys. 17(15), 10028–10039 (2015). https://doi.org/10.1039/c4cp05885b
  32. H. Lv, L. Lin, X. Zhang, Y. Song, H. Matsumoto et al., In situ investigation of reversible exsolution/dissolution of CoFe alloy nanops in a Co-doped Sr2Fe1.5Mo0.5O6−δ cathode for CO2 electrolysis. Adv. Mater. 32(6), 1906193 (2020). https://doi.org/10.1002/adma.201906193
  33. K.J. Kim, C. Lim, K.T. Bae, J.J. Lee, M.Y. Oh et al., Concurrent promotion of phase transition and bimetallic nanocatalyst exsolution in perovskite oxides driven by Pd doping to achieve highly active bifunctional fuel electrodes for reversible solid oxide electrochemical cells. Appl. Catal. B Environ. 314, 121517 (2022). https://doi.org/10.1016/j.apcatb.2022.121517
  34. J. Kudrnovský, V. Drchal, P. Bruno, Magnetic properties of FCC Ni-based transition metal alloys. Phys. Rev. B 77(22), 224422 (2008). https://doi.org/10.1103/physrevb.77.224422
  35. S.A. Theofanidis, V.V. Galvita, M. Sabbe, H. Poelman, C. Detavernier et al., Controlling the stability of a Fe–Ni reforming catalyst: structural organization of the active components. Appl. Catal. B Environ. 209, 405–416 (2017). https://doi.org/10.1016/j.apcatb.2017.03.025
  36. S.S. Aamlid, M. Oudah, J. Rottler, A.M. Hallas, Understanding the role of entropy in high entropy oxides. J. Am. Chem. Soc. 145(11), 5991–6006 (2023). https://doi.org/10.1021/jacs.2c11608
  37. X. Chen, Y. Tan, Z. Li, T. Liu, Y. Song et al., Advanced air electrodes for reversible protonic ceramic electrochemical cells: a comprehensive review. Adv. Mater. 37(48), 2418620 (2025). https://doi.org/10.1002/adma.202418620
  38. A. Hu, C. Yang, Y. Li, K. Xia, Y. Tian et al., High-entropy driven self-assembled dual-phase composite air electrodes with enhanced performance and stability for reversible protonic ceramic cells. Adv. Energy Mater. 15(22), 2405466 (2025). https://doi.org/10.1002/aenm.202405466
  39. J. Qiao, H. Chen, Z. Wang, W. Sun, H. Li et al., Enhancing the catalytic activity of Y0.08Sr0.92TiO3–δ anodes through in situ Cu exsolution for direct carbon solid oxide fuel cells. Ind. Eng. Chem. Res. 59(29), 13105–13112 (2020). https://doi.org/10.1021/acs.iecr.0c02203
  40. Z. Li, C. Wang, I.T. Bello, M. Guo, N. Yu et al., Direct ammonia protonic ceramic fuel cell: a modelling study based on elementary reaction kinetics. J. Power. Sources 556, 232505 (2023). https://doi.org/10.1016/j.jpowsour.2022.232505
  41. Z. Liu, M. Tao, M. Xiao, J. Li, R. Xu et al., Direct ammonia protonic ceramic fuel cells through heterogeneous interface engineering. Chem. Catal. 5(7), 101365 (2025). https://doi.org/10.1016/j.checat.2025.101365
  42. Y. Song, J. Chen, M. Yang, M. Xu, D. Liu et al., Realizing simultaneous detrimental reactions suppression and multiple benefits generation from nickel doping toward improved protonic ceramic fuel cell performance. Small 18(16), 2200450 (2022). https://doi.org/10.1002/smll.202200450
  43. H.J. Jeong, W. Chang, B.G. Seo, Y.S. Choi, K.H. Kim et al., High-performance ammonia protonic ceramic fuel cells using a Pd inter-catalyst. Small 19(22), e2208149 (2023). https://doi.org/10.1002/smll.202208149
  44. D. Feng, T. Zhu, M. Li, V.K. Peterson, H. Rabiee et al., K and Mg Co-doped perovskite oxide for enhanced anode of direct ammonia protonic ceramic fuel cell. Int. J. Hydrogen Energy 88, 272–278 (2024). https://doi.org/10.1016/j.ijhydene.2024.09.186
  45. W. Sheng, M. Fei, W. Chen, Z. Chen, D. Liu et al., A new efficient and anti-sintering perovskite oxide-based internal catalyst for tubular direct-ammonia protonic ceramic fuel cells. J. Power. Sources 642, 237008 (2025). https://doi.org/10.1016/j.jpowsour.2025.237008
  46. B. Wu, X. Yu, Z. Zhao, B. He, Z. Jin et al., Improving the catalytic activity and sintering resistance of Ni-BaCe0.7Zr0.1Y0.1Yb0.1O3–cermet anode for ammonia-fueled protonic ceramic fuel cells via cobalt addition. Chem. Eng. J. 507, 160757 (2025). https://doi.org/10.1016/j.cej.2025.160757
Read More
Author biographies are not available.
Download this PDF file
PDF SUPPLEMENTARY FILE

Most read articles by the same author(s)