Robust CoRuO_x oxide catalysts with broad electrolyte compatibility toward superior hydrogen evolution

Abstract

Developing hydrogen evolution reaction (HER) electrocatalysts that combine high activity with reliable operation in different electrolytes remains important for clean-hydrogen and electrochemical-energy technologies. In this study, CoRu composite oxides with adjustable Co/Ru molar ratios were formed in situ on nickel foam through co-precipitation and subsequent high-temperature calcination, and their HER behavior was examined in alkaline, neutral, and near-neutral media. Co₄Ru₁O_x showed the good activity and durability. In 1 M KOH, current densities of 100, 300, and 700 mA cm^-2 were obtained at overpotentials of 78, 127, and 196 mV, respectively; the corresponding Tafel slope was 21.64 mV dec^-1. The electrode also operated for 200 h in both 1 and 6 M KOH. When incorporated into a membrane electrode assembly electrolyzer, Co₄Ru₁O_x||NF sustained overall water splitting at 100 mA cm^-2 for 200 h. In 1 M phosphate buffer solution, only 16 mV was needed to deliver 10 mA cm^-2, and stable operation was again maintained for 200 h. High-current HER activity was also obtained in saturated KHCO₃, while a Zn-CO₂ cell using this catalyst reached a maximum power density of 9.6 mW cm^-2. Collectively, these findings identify Co₄Ru₁O_x as a multifunctional HER electrode suited to several electrochemical environments.

Keywords

Hydrogen evolution reaction / stability / electrolyte adaptability / overpotential

References

[1] Shi J,Peng L.Engineered Mo-O-Fe active centers for Efficient and stable overall water splitting along the lattice-oxygen mechanism.Green Energy Environ2026;S2468025726000464

[2] Sazali N.Emerging technologies by hydrogen: a review.Int J Hydrogen Energy2020;45:18753-71

[3] Yang X,Zhou Y.Synergistic optimization of pore structure and hydrophilicity for an ultrathin, high-safety composite diaphragm toward high-current, durable alkaline water electrolysis.Sci Bull2026;71:3937-50

[4] He J,Liu X.Beyond oxygen evolution: recent progress in hydrogen production via anodic substitution reactions.Mater Rep Energy2026;6:100426

[5] Zhao C,Li F.Diverging maturity and converging challenges of water and CO₂ electrolysis in 2025.Nat Rev Clean Technol2026;2:8-10

[6] Lee Y,Sahu BK,Shin H.Pulsed laser-engineered single-atom Pt sites on MoC for unprecedented alkaline hydrogen evolution over acidic media.Mater Rep Energy2026;6:100403

[7] Hou L,Gu X.Design strategies of ruthenium‐based materials toward alkaline hydrogen evolution reaction.EcoEnergy2023;1:16-44

[8] Wu L,Li W,An L.Multi-scale modeling of the multi-phase flow in water electrolyzers for green hydrogen production.Mater Rep Energy2025;5:100356

[9] Zhu Y,Gao C.Facilitating alkaline hydrogen evolution reaction on the hetero-interfaced Ru/RuO₂ through Pt single atoms doping.Nat Commun2024;15:1447 PMCID:PMC10873302

[10] Lin B,Niu B,Chen Y.The research progress of ruthenium-based catalysts for the alkaline hydrogen evolution reaction in water electrolysis.Catalysts2024;14:671

[11] Yu X,Zhang L.Ruthenium-cobalt oxide solid solution nanofiber: a robust bifunctional electrocatalyst for overall water splitting with superior ampere-grade-current-density electrocatalytic performance.Acta Mater2025;294:121165

[12] Zhang H,Ren J,Li X.Synergistic engineering of morphology and electronic structure in constructing metal-organic framework-derived Ru doped cobalt-nickel oxide heterostructure towards efficient alkaline hydrogen evolution reaction.Chem Eng J2021;426:131300

[13] Ren F,Feng L.An effective bimetallic oxide catalyst of RuO₂-Co₃O₄ for alkaline overall water splitting.Nano Res2023;17:3785-93

[14] Hu L,Chen Y.Constructing the confined RuCo nanoalloys with modulated d-band centers for efficient pH-robust hydrogen evolution.J Energy Chem2026;116:58-68

[15] Zhou Y,Ye C.Ru single atoms anchored on Co₃O₄ nanorods for efficient overall water splitting under pH‐universal conditions.Adv Energy Mater2025;15:2500700

[16] Kityk A,Pavlik V,Balog M.Unveiling structure-performance relationships in HER catalysts for sustainable and scalable hydrogen production.Mater Rep Energy2026;6:100407

[17] Luo J,Wu M.Local microenvironment reactive zone engineering promotes water activation.Mater Rep Energy2025;5:100327

[18] Zhang Y,Tian J.Lattice-hydrogen cycling mechanism enables pH-universal hydrogen evolution at ampere-level current densities.Nat Commun2025;16:10863 PMCID:PMC12675675

[19] Gupta D,Guo Z.Bifunctional catalysts for CO₂ reduction and O₂ evolution: a pivotal for aqueous rechargeable Zn-CO₂ batteries.Adv Mater2024;36:2407099

[20] Kim C,Joo S.Highly efficient CO₂ utilization via aqueous zinc- or aluminum-CO₂ systems for hydrogen gas evolution and electricity production.Angew Chem Int Ed2019;58:9506-11

[21] Kawashima K,Son YJ.Accurate potentials of Hg/HgO electrodes: practical parameters for reporting alkaline water electrolysis overpotentials.ACS Catal2023;13:1893-8

[22] Li Y,Yuan M.Piezoelectric activation of dual lattice-oxygen mechanism through OH- Grotthuss transport in water electrolysis‏.Nat Commun2026;17:4346 PMCID:PMC13172304

[23] Mccrory CCL,Peters JC.Benchmarking heterogeneous electrocatalysts for the oxygen evolution reaction.J Am Chem Soc2013;135:16977-87

[24] Yao R,Zhang K.Stable hydrogen evolution reaction at high current densities via designing the Ni single atoms and Ru nanoparticles linked by carbon bridges.Nat Commun2024;15:2218 PMCID:PMC10933429

[25] Der Zalm JM, Quintal J, Hira SA, Chen S, Chen A. Recent trends in electrochemical catalyst design for hydrogen evolution, oxygen evolution, and overall water splitting.Electrochim Acta2023;439:141715

[26] Deng L,Yang L.Bubble evolution dynamics in alkaline water electrolysis.eScience2025;5:100353

[27] Araújo F,Moita AS.Alkaline water electrolysis: ultrasonic field and hydrogen bubble formation.Int J Hydrogen Energy2024;78:594-603

[28] Chang B,Zuo S.Dynamic construction of a durable epitaxial catalytic layer for industrial alkaline water splitting.Nat Commun2025;16:7959 PMCID:PMC12381035

[29] Zhou S,Shang L.Facilitating alkaline hydrogen evolution kinetics via interfacial modulation of hydrogen-bond networks by porous amine cages.Nat Commun2025;16:1849 PMCID:PMC11845474

[30] Jiang X,Song C.A novel multi-channel porous structure facilitating mass transport towards highly efficient alkaline water electrolysis.J Energy Chem2024;93:511-8

[31] Ping X,Zheng L.Locking the lattice oxygen in RuO₂ to stabilize highly active Ru sites in acidic water oxidation.Nat Commun2024;15:2501 PMCID:PMC10954744

[32] Yao T,Qin S.Effect of rGO coating on interconnected Co₃O₄ nanosheets and improved supercapacitive behavior of Co₃O₄/rGO/NF architecture.Nano Micro Lett2017;9:38 PMCID:PMC6199030

[33] Laïk B,Emery N.XPS investigation of Co-Ni oxidized compounds surface using peak-on-satellite ratio. Application to Co₂₀Ni₈₀ passive layer structure and composition.ACS Omega2024;9:40707-22 PMCID:PMC11447992

[34] Thomas B,Huang X.Improving the electrocatalytic activity of cobalt oxide with bismuth for acidic oxygen evolution reaction.J Mater Chem A2024;12:22528-38

[35] Yang Y,Liu H.Unraveling the modulation essence of p bands in Co-based oxide stability on acidic oxygen evolution reaction.Nano Res2024;17:5922-9

[36] Wang Z,Shen H,Li G.RuO_x quantum dots loaded on graphdiyne for high‐performance lithium-sulfur batteries.Adv Mater2023;36:2307786

[37] Yang Y,Ma M.Synergistic interface engineering of RuO₂/Co₃O₄ heterostructures for enhanced overall water splitting in acidic media.Adv Energy Sustain Res2023;4:2300057

[38] Tan L,Liu Z.Nanostructured RuO₂-Co₃O₄@RuCo-EO with low Ru loading as a high-efficiency electrochemical oxygen evolution catalyst.RSC Adv2021;11:11779-85 PMCID:PMC8696486

[39] Jiao J,Zhang C.Doping ruthenium into metal matrix for promoted pH‐universal hydrogen evolution.Adv Sci2022;9:2200010 PMCID:PMC9130909

[40] Lee JK,Lim J,Jang HW.Best practices in membrane electrode assembly for water electrolysis.ACS Mater Lett2024;6:2757-86

[41] Jeon SS,Jeon H.Developing catalysts for membrane electrode assemblies in high performance polymer electrolyte membrane water electrolyzers.ChemSusChem2024;17:e202301827 PMCID:PMC11587686

[42] Liu Y,Zhu J.Integrated energy storage and CO₂ conversion using an aqueous battery with tamed asymmetric reactions.Nat Commun2024;15:977 PMCID:PMC10834454

[43] Wang H,Nie Z.Dual‐anion regulation for reversible and energetic aqueous Zn-CO₂ batteries.Small Methods2023;8:2300867

[44] Xing M,Yuan W.Realization of electron-deficient Ru sites via Co₄N coupling for synergistically enhanced alkaline hydrogen evolution.J Mater Chem A2023;11:22147-53

[45] Kutyła D,Lačnjevac UČ,Elezović NR.Ru-Co alloy coatings electrodeposited on a MAX phase substrate as efficient catalysts for the hydrogen evolution reaction.Int J Hydrogen Energy2024;56:28-40

[46] Liu D,Li S.Atomically precise Ru-O-Ru clusters for enhanced water dissociation in alkaline hydrogen evolution.Nano Res2024;17:6993-7000

[47] Xu N,Sun H.Atmosphere-driven oriental regulation of Ru valence for boosting alkaline water electrolysis.Chem Eng J2024;502:158051

[48] Liu Z,Wang Q,Feng L.Overall water-splitting reaction efficiently catalyzed by a novel bi-functional Ru/Ni₃ N-Ni electrode.Chem Commun2020;56:2352-5

[49] Chen Y,Chu W.Trace Ru-tuned NiO/CNT electrocatalysts outperform benchmark Pt for alkaline hydrogen evolution with superior mass activity.Chem Eng J2023;472:144922

[50] Zhang Y,Yu Z.Ruthenium oxide nanoparticles immobilized on Ti₃C₂ MXene nanosheets for boosting seawater electrolysis.ACS Appl Mater Interfaces2023;15:58345-55

[51] Zhu J,Shi W.Epitaxially grown Ru clusters-nickel nitride heterostructure advances water electrolysis kinetics in alkaline and seawater media.Energy Environ Mater2022;6:e12318

[52] Liu Y,Zhao Y.Ru-doped 3D porous Ni₃N sphere as efficient Bi-functional electrocatalysts toward urea assisted water-splitting.Int J Hydrogen Energy2022;47:25081-9

[53] Yang Y,Li R.Engineering the strong metal support interaction of titanium nitride and ruthenium nanorods for effective hydrogen evolution reaction.Appl Catal B Environ2022;317:121796

[54] Chen J,Qin M.Reversible hydrogen spillover in Ru-WO_3-x enhances hydrogen evolution activity in neutral pH water splitting.Nat Commun2022;13:5382 PMCID:PMC9474501

[55] Yao R,Zhang K.Construction of a CoRu/CoRuP heterogeneous electrocatalyst for efficient pH-universal hydrogen production.ACS Sustain Chem Eng2023;12:291-9

[56] Wu Q,Xiao M,Cui C.Bicarbonate-mediated proton transfer requires cations.Nat Commun2024;15:9145 PMCID:PMC11500353

[57] Zhang Y,Li Y.Electrochemical pH‐swing CO₂ capture facilitated by suppressed bubble accumulation at electrode/electrolyte interfaces.Angew Chem Int Ed2025;65:e13456

[58] Sun K,Zhuang Z.Interfacial water engineering boosts neutral water reduction.Nat Commun2022;13:6260 PMCID:PMC9587018