Enhanced electrocatalytic Activity of NiCoP/Ni₅P₄@NiFe-LDH catalysts via Ir doping and oxygen vacancy engineering

Abstract

Alkaline water electrolysis offers a promising route for large-scale hydrogen production, but its efficiency is limited by the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we designed a hierarchical composite electrocatalyst comprising iridium-doped nickel-cobalt phosphide nanoparticles (Ir-NiCoP/Ni₅P₄) encapsulated within nickel-iron layered double hydroxide nanosheets (NiFe-LDH). Oxygen vacancies (O_V) were engineered on the surface via sodium borohydride reduction, yielding an optimized catalyst denoted as Ir-NiCoP/Ni₅P₄@NiFe-LDH-1-O_V. The optimized catalyst delivers low overpotentials of 52.7 mV for HER and 197.3 mV for OER at 10 mA cm^-2 and maintains remarkable stability over 100 h for overall water splitting. Moreover, the Ir-NiCoP/Ni₅P₄@NiFe-LDH catalyst exhibits overpotentials of 76.7 and 101.3 mV for HER and the ammonia oxidation reaction A in 1 M KOH + NH₃·H₂O, respectively.

Keywords

Element doping / electrocatalyst / overall water splitting / hydrogen evolution reaction / oxygen evolution reaction

References

[1] Pu T.,Ding J.,Zhang F..et al. Dual atom catalysts for energy and environmental applications Angew. Chem. Int. Ed. 2023 62 e202305964

[2] Cao P.,Liu Y.,Zhang Q.,Guo C.,Li J.,Zeng Q.. MXene/MOF composites: synergistic platforms for advanced Energy, catalysis, and environmental applications Coord. Chem. Rev. 2025 545 217018

[3] Zhou H.,Xu S.,Zhang B..et al. In situ reconstructed amorphous MOOH-enhanced NiCoP@NiFe-LDH bifunctional electrocatalyst for long durable seawater electrolysis Inorg. Chem. Front. 2026 13 666 79

[4] Johnson N.,Liebreich M.,Kammen D. M.,Ekins P.,Mckenna R.,Staffell I.. Realistic roles for hydrogen in the future energy transition Nat. Rev. Clean Technol. 2025 1 351 71

[5] Zhang L.,Qi F.,Ren R..et al. Recent advances in green hydrogen production by electrolyzing water with anion-exchange membrane Research 2025 8 0677 PMC12069883

[6] Mao J.,Liang J.,Li Y..et al. Electrochemical lithiation regulates the active hydrogen supply on Ru-Sn nanowires for hydrogen evolution toward the high-performing anion exchange membrane water electrolyzer J. Am. Chem. Soc. 2025 147 7711 20

[7] Zhang X.,Cao C.,Ling T.,Ye C.,Lu J.,Shan J.. Developing practical catalysts for high‐current‐density water electrolysis Adv. Energy Mater. 2024 14 2402633

[8] Gao X.,Chen Y.,Wang Y..et al. Next-generation green hydrogen: progress and perspective from electricity, catalyst to electrolyte in electrocatalytic water splitting Nano Micro Lett. 2024 16 237 PMC11226619

[9] Cao L.,Zhang J.,Ding L.,Du Z.,He C.. Metal-organic frameworks derived transition metal phosphides for electrocatalytic water splitting J Energy Chem. 2022 68 494 520

[10] Geng P.,Ji B.,Guo Y.,Xiao C.,Wan J.,Li C. M.. MOF-derived transition metal phosphides for rechargeable batteries Chem. Eng. J. 2025 516 164033

[11] Zhou Z.,Shi X.,Yin J.,Kong W.,Sun J.,Wen Z.. Symbiotic growth of cobalt phosphides facilitates multiphase synergic function on long-cycling stability Chem. Phys. Lett. 2020 749 137403

[12] Gao Z.,Gao Q.,Liu Z..et al. High-efficiency hydrogen evolution reaction catalyzed by iron phosphide nanocrystals RSC Adv. 2016 6 114430 5

[13] Song L.,Zhang S.. A versatile route to synthesizing bulk and supported nickel phosphides by thermal treatment of a mechanical mixing of nickel chloride and sodium hypophosphite Powder Technol. 2011 208 713 6

[14] Tang D.,Li T.,Li C. M.. Metal and phosphonium-based ionic liquid: a new Co and P dual-source for synthesis of cobalt phosphide toward hydrogen evolution reaction Int. J. Hydrogen Energy 2019 44 1720 6

[15] Galindo-ortega Y.,Infantes-molina A.,Huirache-acuña R..et al. Active ruthenium phosphide as selective sulfur removal catalyst of gasoline model compounds Fuel Process. Technol. 2020 208 106507

[16] Liu D.,Ai H.,Chen M..et al. Multi-phase heterostructure of CoNiP/Co_xP for enhanced hydrogen evolution under alkaline and seawater conditions by promoting H₂O dissociation Small 2021 17 e2007557

[17] Wu L.,Yu L.,Mcelhenny B..et al. Rational design of core-shell-structured CoP_x@FeOOH for efficient seawater electrolysis Appl. Catal. B Environ. 2021 294 120256

[18] Liu Y.,Hu H.,Wang K.,Huang J.,Wang D.. Advancing seawater electrolysis: NiFe‐LDH‐based electrocatalysts for the oxygen evolution reaction Adv. Energy Mater. 2025 16 e04101

[19] Li J.,Naren G.,Tang C..et al. Asymmetric ruthenium-iron dipole enabling fast alkaline water splitting on ruthenium-doped iron-nickel layered double hydroxides Mater. Rep. Energy 2025 5 100359

[20] Abdelghafar F.,Xu X.,Guan D..et al. New nanocomposites derived from cation-nonstoichiometric Ba_x(Co, Fe, Zr, Y)O_3-δ as efficient electrocatalysts for water oxidation in alkaline solution ACS Mater. Lett. 2024 6 2985 94

[21] Fan M.,Cui J.,Wu J.,Vajtai R.,Sun D.,Ajayan P. M.. Improving the catalytic activity of carbon-supported single atom catalysts by polynary metal or heteroatom doping Small 2020 16 e1906782

[22] Wang S.,Chen Z.,Sun L..et al. Synergistic mechanism of disparate surface hydroxyls and oxygen vacancies towards peroxymonosulfate activation for durable water decontamination Chem. Eng. J. 2025 503 158259

[23] Xue N.,Lin Z.,Li P.,Diao P.,Zhang Q.. Sulfur-doped CoSe₂ porous nanosheets as efficient electrocatalysts for the hydrogen evolution reaction ACS Appl. Mater. Interfaces 2020 12 28288 97

[24] Yang Y.,Hao J.,Lyu C..et al. Electron islands-induced interface engineering in FeP@NiCoP/Mo₄P₃ for efficient hydrogen evolution catalysis Adv. Funct. Mater. 2025 35 2507225

[25] Sial M. A. Z. G.,Liu S.,Zou J..et al. NiCoFe alloy multishell hollow spheres with lattice distortion to trigger efficient hydrogen evolution in acidic medium Sustain. Energy Fuels 2019 3 3310 7

[26] Li X.,Wu T.,Li N..et al. Vertically staggered porous Ni₂P/Fe₂P nanosheets with trace Ru doping as bifunctional electrocatalyst for alkaline seawater splitting Adv. Funct. Mater. 2024 34 2400734

[27] Gao L.,Yang Z.,Sun T..et al. Autocatalytic surface reduction‐assisted synthesis of PtW ultrathin alloy nanowires for highly efficient hydrogen evolution reaction Adv. Energy Mater. 2022 12 2103943

[28] Su P.,Huang W.,Zhang J..et al. Fe atoms anchored on defective nitrogen doped hollow carbon spheres as efficient electrocatalysts for oxygen reduction reaction Nano Res. 2020 14 1069 77

[29] Ma F.,Chen H.,Wu H..et al. Phase transition during sintering of layered transition metal oxide sodium cathodes Nano Lett. 2025 25 9293 301

[30] Luo J.,Deng J.,Wang H..et al. High-performance FeCoNiMo bifunctional catalysts with hierarchical porosity for water splitting Tungsten 2025 8 242 54

[31] Zhang P.,Wu Q.,Wang H..et al. Z-scheme heterojunction Zn₃(OH)₂(V₂O₇)(H₂O)₂/V-Zn(O,S) for enhanced visible-light photocatalytic N₂ fixation via synergistic heterovalent vanadium states and oxygen vacancy defects Chin. J. Catal. 2025 74 279 93

[32] Ma W.,Zhang Y.,Wang B..et al. Significantly enhanced OER and HER performance of NiCo-LDH and NiCoP under industrial water splitting conditions through Ru and Mn bimetallic co-doping strategy Chem. Eng. J. 2024 494 153212

[33] Feng J.,Wang X.,Pan H.. In-situ reconstruction of catalyst in electrocatalysis Adv. Mater. 2024 36 e2411688

[34] Wang M.,Tan H.,Liu X.,Yan X.,Liang J.. Energy and resource generation via electrochemical ammonia oxidation: from materials design to system integration Adv. Energy Mater. 2025 15 e03846

[35] Yu T.,Tan K.,Wu J.,Zou Y.,Yin S.. Bifunctional interstitial phosphorous doping strategy boosts platinum-zinc alloy for efficient ammonia oxidation reaction and hydrogen evolution reaction Nano Res. 2023 17 1182 9

[36] Huan Y.,He Y.,Liu S..et al. Electrochemical ammonia oxidation reaction on nickel‐based non‐noble metal electrocatalysts: from mechanistic understanding to practical applications Adv. Energy Mater. 2025 15 e03815

[37] Du L.,Xing L.,Zhang G.,Liu X.,Rawach D.,Sun S.. Engineering of electrocatalyst/electrolyte interface for ambient ammonia synthesis SusMat 2021 1 150 73