Scalable synthesis of an IrO_x/Ir-Co₃O₄ heterostructure for efficient and stable acidic oxygen evolution

Abstract

The deployment of proton exchange membrane water electrolysis (PEMWE) necessitates efficient, stable, and low-Ir electrocatalysts for acidic oxygen evolution reaction (OER) at the anode. Herein, an IrO_x/Ir-Co₃O₄ heterostructure electrocatalyst is developed featuring bulk-doped Ir-Co₃O₄ with surface-anchored IrO_x, synthesized via a facile two-step electrochemical co-deposition process followed by programmed annealing. The IrO_x/Ir-Co₃O₄ catalyst requires an overpotential of only 237 mV to reach 10 mA/cm² and achieves a high mass activity of 230 A/g_Ir at 1.5 V versus RHE. In a 1 cm² membrane electrode assembly electrolyzer (Pt/C||IrO_x/Ir-Co₃O₄), a cell voltage of only 1.773 V delivers 1 A/cm², with stable operation exceeding 160 h at 200 mA/cm². Moreover, a 100 cm² IrO_x/Ir-Co₃O₄ anode was fabricated, exhibiting performance comparable to that of its 1 cm² counterpart. Structural and computational analyses reveal that the synergy between bulk-doped Ir-Co₃O₄ and surface anchored IrO_x optimizes the electronic structure, thereby enhancing both catalytic activity and durability. This work provides a viable and scalable pathway for developing low-Ir electrocatalysts for practical PEMWE applications.

Graphical abstract

Keywords

Acidic OER / Ir-based electrocatalysts / Scalable synthesis / Heterostructure / PEMWE

References

[1] Gunathilake C , Soliman I , Panthi D . et al. A comprehensive review on hydrogen production, storage, and applications. Chemical Society Reviews, 2024, 53(22): 10900–10969

[2] Turner J A . Sustainable hydrogen production. Science, 2004, 305(5686): 972–974

[3] Wang C R , Stansberry J M , Mukundan R . et al. Proton Exchange Membrane (PEM) water electrolysis: Cell-level considerations for gigawatt-scale deployment. Chemical Reviews, 2025, 125(3): 1257–1302

[4] Chen G X , Zhang J H , Zhou K L . et al. MXene supported PtCo bimetallic catalyst for hydrogen evolution in acidic conditions. Frontiers in Energy, 2024, 18(3): 369–377

[5] Li Z L , Sheng H Y , Lin Y C . et al. Rutile-structured Ru_0.48Mn_0.52O₂ solid solution for highly active and stable oxygen evolution at large current density in acidic media. Advanced Functional Materials, 2024, 34(51): 2409714

[6] Cullen D A , Neyerlin K C , Ahluwalia R K . et al. New roads and challenges for fuel cells in heavy-duty transportation. Nature Energy, 2021, 6(5): 462–474

[7] Yu H , Zhang J H , Zhou K L . et al. Acid-stable bimetallic phosphide-silver core-shell nanowires with a seamlessly conductive network for enhanced hydrogen evolution reaction. Frontiers in Energy, 2025, 19(5): 694–702

[8] Wang Y , Yan H J , Fu H G . Recent advances and modulation tactics in Ru- and Ir-based electrocatalysts for PEMWE anodes at large current densities. eScience, 2025, 5(3): 100323

[9] Li H J W , Lin Y , Duan J Y . et al. Stability of electrocatalytic OER: From principle to application. Chemical Society Reviews, 2024, 53(21): 10709–10740

[10] Yuan Y L , Fang H L , Chen K . et al. Engineering high-density grain boundaries in Ru_0.8Ir_0.2O_x solid-solution nanosheets for efficient and durable OER electrocatalysis. Advanced Materials, 2025, 37(18): 2501607

[11] Lun Y F , Chen H X , Wang K . et al. Discovery of efficient acidic oxygen evolution electrocatalyst: High-throughput computational screening of MgIrRu oxide. Advanced Energy Materials, 2025, 15(29): 2405657

[12] Hu H Y , Liu S L , Sun H F . et al. Low-Ir-content Ir_0.10Mn_0.90O₂ solid solution for highly active oxygen evolution in acid media. Small, 2025, 21(21): 2412096

[13] Zhou K F , Wang Y J , Jiang Z Q . et al. Ir/Mn Co-mixing and oxide-support interaction modulation through plasma promoted asymmetric oxygen coupling for stable acidic oxygen evolution. Advanced Materials, 2025, 37(18): 2420159

[14] Liu W B , Long G F , Xiang Z P . et al. Extremely active and robust Ir–Mn dual-atom electrocatalyst for oxygen evolution reaction by oxygen–oxygen radical coupling mechanism. Angewandte Chemie, 2024, 136(43): e202411014

[15] Shi Z P , Li J , Jiang J D . et al. Enhanced acidic water oxidation by dynamic migration of oxygen species at the Ir/Nb₂O_5–x catalyst/support interfaces. Angewandte Chemie International Edition, 2022, 61(52): e202212341

[16] Wang Y N , Zhao Z C , Liang X . et al. Supported IrO₂ nanocatalyst with multilayered structure for proton exchange membrane water electrolysis. Advanced Materials, 2024, 36(39): 2407717

[17] Todoroki N , Kudo R , Hayashi K . et al. Improving the oxygen evolution activity and stability of Nb-doped TiO₂-supported RuO₂ by a SnO₂ interlayer: A model catalyst study on single-crystal oxide heterostructures. ACS Catalysis, 2023, 13(17): 11433–11440

[18] Gao H M , Xiao Z H , Du S Q . et al. Reducing the Ir–O coordination number in anodic catalysts based on IrO_x nanoparticles towards enhanced proton-exchange-membrane water electrolysis. Angewandte Chemie International Edition, 2023, 62(49): e202313954

[19] Luo F , Guo L , Xie Y H . et al. Iridium nanorods as a robust and stable bifunctional electrocatalyst for pH-universal water splitting. Applied Catalysis B: Environmental, 2020, 279: 119394

[20] Blasco-Ahicart M , Soriano-López J , Carbó J J . et al. Polyoxometalate electrocatalysts based on earth-abundant metals for efficient water oxidation in acidic media. Nature Chemistry, 2018, 10(1): 24–30

[21] Li A L , Kong S , Guo C X . et al. Enhancing the stability of cobalt spinel oxide towards sustainable oxygen evolution in acid. Nature Catalysis, 2022, 5(2): 109–118

[22] Jia W Q , Miao L C , Cao X J . et al. Manganese-containing electrocatalysts for sustainable acidic oxygen evolution. eScience, 2026, 6(1): 100427

[23] Seh Z W , Kibsgaard J , Dickens C F . et al. Combining theory and experiment in electrocatalysis: Insights into materials design. Science, 2017, 355(6321): eaad4998

[24] Zhu Y M , Wang J A , Koketsu T . et al. Iridium single atoms incorporated in Co₃O₄ efficiently catalyze the oxygen evolution in acidic conditions. Nature Communications, 2022, 13: 7754

[25] Shan J Q , Ye C , Chen S M . et al. Short-range ordered iridium single atoms integrated into cobalt oxide spinel structure for highly efficient electrocatalytic water oxidation. Journal of the American Chemical Society, 2021, 143(13): 5201–5211

[26] Hua K , Li X K , Rui Z Y . et al. Integrating atomically dispersed Ir sites in MnCo₂O_4.5 for highly stable acidic oxygen evolution reaction. ACS Catalysis, 2024, 14(5): 3712–3724

[27] Liu Y , Chen Y W , Mu X L . et al. Spinel-anchored iridium single atoms enable efficient acidic water oxidation via intermediate stabilization effect. ACS Catalysis, 2023, 13(6): 3757–3767

[28] Zhang Z R , Jia C Y , Ma P Y . et al. Distance effect of single atoms on stability of cobalt oxide catalysts for acidic oxygen evolution. Nature Communications, 2024, 15(1): 1767

[29] Li G N , Priyadarsini A , Xie Z H . et al. Achieving higher activity of acidic oxygen evolution reaction using an atomically thin layer of IrO_x over Co₃O₄. Journal of the American Chemical Society, 2025, 147(8): 7008–7016

[30] Kresse G , Furthmüller J . Efficiency of ab initio total energy calculations for metals and semiconductors using a plane-wave basis set. Computational Materials Science, 1996, 6(1): 15–50

[31] Kresse G , Hafner J . Ab initio molecular-dynamics simulation of the liquid-metal-amorphous-semiconductor transition in germanium. Physical Review B, 1994, 49(20): 14251–14269

[32] Kresse G , Hafner J . Ab initio molecular dynamics for open-shell transition metals. Physical Review B, 1993, 48(17): 13115–13118

[33] Perdew J P , Burke K , Ernzerhof M . Generalized gradient approximation made simple. Physical Review Letters, 1996, 77(18): 3865–3868

[34] Blöchl P E . Projector augmented-wave method. Physical Review B, 1994, 50(24): 17953–17979

[35] Žutić I , Fabian J , Das Sarma S . Spintronics: Fundamentals and applications. Reviews of Modern Physics, 2004, 76(2): 323–410

[36] Grimme S , Antony J , Ehrlich S . et al. A consistent and accurate ab initio parametrization of density functional dispersion correction (DFT-D) for the 94 elements H-Pu. The Journal of Chemical Physics, 2010, 132(15): 154104

[37] Dudarev S L , Botton G A , Savrasov S Y . et al. Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study. Physical Review B, 1998, 57(3): 1505–1509

[38] Wang L , Maxisch T , Ceder G . Oxidation energies of transition metal oxides within the GGA+ U framework. Physical Review B, 2006, 73(19): 195107

[39] Bianchetti E , Perilli D , Di Valentin C . Improving the oxygen evolution reaction on Fe₃O₄(001) with single-atom catalysts. ACS catalysis, 2023, 13(7): 4811–4823

[40] Li W R , Lv J N , Chen X C . et al. Support-accelerated proton transfer for enhanced oxygen evolution catalysis. Journal of the American Chemical Society, 2025, 147(32): 29505–29516

[41] Sun S G , Wan Z Q , Xu Y Y . et al. Phase engineering modulates the electronic structure of the IrO₂/MoS₂ heterojunction for efficient and stable water splitting. ACS Nano, 2025, 19(12): 12090–12101

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