Electronic modulation in a defect-rich high-entropy NiCoFeCu LDH enables accelerated oxygen evolution

Abstract

Accelerating the oxygen evolution reaction (OER) is critical for efficient alkaline water electrolysis in green hydrogen production. Rational regulation of the electronic structure of transition metal (oxy)hydroxides offers a vital route to enhance their OER kinetics under alkaline conditions. Herein, we reported a defect-rich high-entropy layered double hydroxide, D-NiCoFeCu-LDH, constructed via a sequential electrodeposition–electrochemical etching strategy. Selective chromium leaching reconstructs a homogeneous Ni–Co–Fe–Cu high-entropy matrix while introducing abundant vacancies and lattice distortion. Structural characterization confirms uniform elemental distribution and defect-enriched nanosheet arrays, whereas X-ray photoelectron spectroscopy (XPS) analysis reveals pronounced electronic redistribution, manifested by increased high-valence Ni³⁺/Co³⁺ species and positive binding energy shifts. We proposed that highly dispersed Cu⁺/Cu²⁺ species act as electronic modulators, withdrawing electron density from neighboring Ni, Co, and Fe centers, while lattice distortion further promotes electronic reconfiguration. Electrochemical measurements demonstrated enhanced intrinsic activity and accelerated charge-transfer kinetics compared to quaternary counterparts. Importantly, in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) directly verified facilitated *OOH intermediate formation at lower overpotential, establishing a molecular-level link between electronic modulation and improved OER kinetics. In this work, we provide mechanistic insight into how synergistic high-entropy regulation and defect engineering cooperatively enhance intrinsic catalytic activity, offering a framework for designing durable, high-performance OER electrocatalysts.

Keywords

high-entropy materials / layered double hydroxide / electronic structure modulation / defect engineering / oxygen evolution reaction

References

[1] Hoang AL, Balakrishnan S, Hodges A, et al. (2023) High-performing catalysts for energy-efficient commercial alkaline water electrolysis. Sustainable Energy Fuels 7: 31-60. https://doi.org/10.1039/d2se01197b

[2] Tuysuz H (2024) Alkaline water electrolysis for green hydrogen production. Acc Chem Res 57: 558-567. https://doi.org/10.1021/acs.accounts.3c00709

[3] Wang W, Yang B, Zhang H, et al. (2025) Novel synthesis of amorphous/defect-rich NiFe(O)OH nanosheets for alkaline electrolyzers at high current density. Next Mater 9: 101232. https://doi.org/10.1016/j.nxmate.2025.101232

[4] Jia H, Yao N, Zhu J, et al. (2023) Reconstructured electrocatalysts during oxygen evolution reaction under alkaline electrolytes. Chemistry 29: e202203073. https://doi.org/10.1002/chem.202203073

[5] Park H, Park BH, Choi J, et al. (2020) Enhanced electrochemical properties and OER performances by Cu substitution in NiCo₂O₄ spinel structure . Nanomaterials (Basel) 10: 1727. https://doi.org/10.3390/nano10091727

[6] Bai J, Chen C, Lian Y, et al. (2024) Role of amorphous engineering and cerium doping in NiFe oxyhydroxide for electrocatalytic water oxidation. J Colloid Interface Sci 663: 280-286. https://doi.org/10.1016/j.jcis.2024.02.093

[7] Li J, Wei Y, Zou L, et al. (2025) Cu dual-site doping: synergistic enhancement of OER activity through LDH and nickel foam interface engineering. New J Chem 49: 17577-17587. https://doi.org/10.1039/d5nj03068d

[8] Sharma L, Katiyar NK, Parui A, et al. (2021) Low-cost high entropy alloy (HEA) for high-efficiency oxygen evolution reaction (OER). Nano Res 15: 4799-4806. https://doi.org/10.1007/s12274-021-3802-4

[9] Ma Y, Ma Y, Wang Q, et al. (2021) High-entropy energy materials: Challenges and new opportunities. Energy Environ Sci 14: 2883-2905. https://doi.org/10.1039/d1ee00505g

[10] Tomboc GM, Zhang X, Choi S, et al. (2022) Stabilization, characterization, and electrochemical applications of high-entropy oxides: Critical assessment of crystal phase-properties relationship. Adv Funct Mater 32: 2205142. https://doi.org/10.1002/adfm.202205142

[11] Liang J, Cao G, Zeng M, et al. (2024) Controllable synthesis of high-entropy alloys. Chem Soc Rev 53: 6021-6041. https://doi.org/10.1039/d4cs00034j

[12] Ding Y, Wang Z, Liang Z, et al. (2025) A monolayer high-hntropy layered hydroxide frame for efficient oxygen evolution reaction. Adv Mater 37: e2302860. https://doi.org/10.1002/adma.202302860

[13] Jeung Y, Jung H, Kim D, et al. (2021) 2D-structured V-doped Ni(Co, Fe) phosphides with enhanced charge transfer and reactive sites for highly efficient overall water splitting electrocatalysts. J Mater Chem A 9: 12203-12213. https://doi.org/10.1039/d1ta02149d

[14] Yan Y, Li P, Zhang Z, et al. (2024) Interfacial Si-O coordination for inhibiting the graphite phase enables superior SiC/Nb heterostructure joining by AuNi. Composites Part B 282: 111557. https://doi.org/10.1016/j.compositesb.2024.111557

[15] Yang T, Yan Y, Liu R, et al. (2025) Engineering twins within lattice-matched Co/CoO heterostructure enables efficient hydrogen evolution reactions. Nano Lett 25: 7707-7715. https://doi.org/10.1021/acs.nanolett.5c00472

[16] Wang R, Yang Y, Xu X, et al. (2023) Interface engineering and heterometal-doped FeOOH/Ga-Ni₃S₂ nanosheet arrays for efficient electrocatalytic oxygen evolution . Inorg Chem Front 10: 1348-1356. https://doi.org/10.1039/d2qi02081e

[17] Ma H, Chen Z, Wang Z, et al. (2022) Interface engineering of Co/CoMoN/NF heterostructures for high-performance electrochemical overall water splitting. Adv Sci (Weinh) 9: e2105313. https://doi.org/10.1002/advs.202105313

[18] Hou J, Sun Y, Wu Y, et al. (2018) Promoting active sites in core-shell nanowire array as mott-schottky electrocatalysts for efficient and stable overall water splitting. Adv Funct Mater 28: 1704447. https://doi.org/10.1002/adfm.201704447

[19] Yu L, Zhou H, Sun J, et al. (2017) Cu nanowires shelled with NiFe layered double hydroxide nanosheets as bifunctional electrocatalysts for overall water splitting. Energy Environ Sci 10: 1820-1827. https://doi.org/10.1039/c7ee01571b

[20] Wu Y, Xu L, Xin W, et al. (2021) Rational construction of 3D MoNi/NiMoOx@NiFe LDH with rapid electron transfer for efficient overall water splitting. Electrochim Acta 369: 137680. https://doi.org/10.1016/j.electacta.2020.137680

[21] Sang Y, Cao X, Wang L, et al. (2020) Facile synthesis of three-dimensional spherical Ni(OH)₂/NiCo₂O₄ heterojunctions as efficient bifunctional electrocatalysts for water splitting . Int J Hydrogen Energy 45: 30601-30610. https://doi.org/10.1016/j.ijhydene.2020.08.097

[22] Yuan F, Wei J, Qin G, et al. (2020) Carbon cloth supported hierarchical core-shell NiCo₂S₄@CoNi-LDH nanoarrays as catalysts for efficient oxygen evolution reaction in alkaline solution . J Alloys Compd 830: 154658. https://doi.org/10.1016/j.jallcom.2020.154658

[23] Niu Y, Li W, Wu X, et al. (2019) Amorphous nickel sulfide nanosheets with embedded vanadium oxide nanocrystals on nickel foam for efficient electrochemical water oxidation. J Mater Chem A 7: 10534-10542. https://doi.org/10.1039/c8ta12483c

[24] Huo M, Liang Y, Qin K, et al. (2024) Hexavalent iridium boosts oxygen evolution performance. Green Carbon 2: 403-404. https://doi.org/10.1016/j.greenca.2024.07.003

[25] Shu W, Sun Q, Huang K, et al. (2024) V-Doping induced surface electron modulation and nanostructure design for Ni(OH)₂/GO towards efficient urea electro-oxidation . Chem Commun (Camb) 60: 13267-13270. https://doi.org/10.1039/d4cc04157g

[26] Zhang L, Cai W, Bao N (2021) Top-level design strategy to construct an advanced high-entropy Co-Cu-Fe-Mo (oxy)hydroxide electrocatalyst for the oxygen evolution reaction. Adv Mater 33: e2100745. https://doi.org/10.1002/adma.202100745

[27] Zhang W, He X, Pan P, et al. (2025) Cr-enhanced selective dealloying and sequential electrochemical reconstruction to tailor NiFe-based integrated catalysts for industrial-level water oxidation. Energy Environ Sci 18: 8697-8707. https://doi.org/10.1039/d5ee03448e

[28] Wang L, Gao Z, Su K, et al. (2024) Stacked high‐entropy hydroxides promote charge transfer kinetics for photoelectrochemical water splitting. Adv Funct Mater 34: 2403948. https://doi.org/10.1002/adfm.202403948

[29] Zhong X, Wang HY, Zhang C, et al. (2025) High‐valence metal modulating lattice oxygen in high‐entropy layered double hydroxides for enhanced oxygen evolution reaction. Adv Funct Mater 35: e18240. https://doi.org/10.1002/adfm.202518240

[30] Li X, Wang J, Xue H, et al. (2025) Tuning α‐MnOOH formation via atomic‐level Fe introduction for superior OER performance. Adv Funct Mater 35: 2503360. https://doi.org/10.1002/adfm.202503360

[31] Chang R, Pang Y, Yang Q, et al. (2025) High entropy hydroxide with a hollow nanocage structure promotes efficient and stable water/seawater electro-oxidation. Chem Sci 16: 11961-11969. https://doi.org/10.1039/d5sc01961c

[32] Wang F, Feng L, Zhang M, et al. (2025) Engineering oxygen nonbonding states in high entropy hydroxides for scalable water oxidation. Nat Commun 16: 6624. https://doi.org/10.1038/s41467-025-61766-2

[33] Yang H, Li F, Zhan S, et al. (2026) Metal-hydroxyls mediate intramolecular proton transfer in heterogeneous O-O bond formation. Nat Chem 18: 335-344. https://doi.org/10.1038/s41557-025-01993-8

[34] Zhang Y, Zheng T, Dai H, et al. (2025) Lattice oxygen-mediated water oxidation on reconstructed Ni₃S₂/NiFeOOH heterointerfaces . Chemistry, e03063. https://doi.org/10.1002/chem.202503063