Vacancy-engineered Ru-based CNT electrocatalysts for ampere-level water splitting in alkaline and anion-exchange membrane water electrolyzers

doi:10.1016/S1872-2067(26)65116-9

Abstract

Abstract:

Robust metal-support interactions are crucial for designing efficient and corrosion-resistant electrocatalysts, as they significantly enhance charge separation and catalytic activity while also improving the stability and atomic utilization of metal catalysts. Here, we reported a temperature-regulated synthesis strategy to fabricate a self-supporting Ru/B,N co-doped MoO₂ electrocatalyst on a CNT framework (RBNM/CNTs₅₀₀), designed to simultaneously enhance catalytic activity and durability under practical electrolyzer conditions. The RBNM/CNTs₅₀₀ featured a unique nanostructure with excellent conductivity and strong chemical stability, while oxygen-vacancy-rich MoO₂ units at the interface reinforced metal-support interactions. This architecture stabilized Ru species during the OER and facilitated proton transfer, thus accelerating HER kinetics as confirmed by density functional theory calculations. As a result, RBNM/CNTs₅₀₀ exhibited outstanding bifunctional electrocatalytic performance, achieving exceptionally low overpotentials of 9 mV for the HER and 166 mV for the OER at 10 mA cm^‒2, along with superior overall water-splitting activity characterized by a low cell voltage of 1.42 V and stable ampere-level operation at 10, 1000, and 2000 mA cm^‒2 in alkaline media. When integrated into an anion-exchange membrane water electrolyzer, RBNM/CNTs₅₀₀ demonstrated exceptional durability and surpassed benchmark electrocatalysts in performance. This study offers mechanistic insights into defect engineering and underscores a rational design approach for next-generation energy conversion devices.

Key words: Vacancy engineering, Ruthenium-based electrocatalysts, Ampere level overall water splitting, Anion exchange membrane water electrolyzer

Bashir Adegbemiga Yusuf, Hennayaka Mudiyanselage Charitha Madusanka Jayawardana, Waleed Yaseen, Jimin Xie, Yilin Deng, Suci Meng, Yongming Li, Abdussamad Mukhtar Mohammed, Aminu Magaji, Min Chen, Meng Xie, Yuanguo Xu. Vacancy-engineered Ru-based CNT electrocatalysts for ampere-level water splitting in alkaline and anion-exchange membrane water electrolyzers[J]. Chinese Journal of Catalysis, 2026, 88: 279-294.

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URL: https://www.cjcatal.com/EN/10.1016/S1872-2067(26)65116-9

https://www.cjcatal.com/EN/Y2026/V88/I9/279

Figures/Tables 8

Scheme 1. A schematic illustration of the synthesis pathway of the standard RBNM/CNTsx.

Fig. 1. Morphology and structural characterization of the electrocatalysts. SEM images of RBNM/CNTs500 (a,b), RBNM/CNTs400 (c), RBNM/CNTs450 (d), RBNM/CNTs550 (e), and RBNM/CNTs600 (f). TEM image (g), HRTEM images (h,i), SAED pattern (j), HAADF line scan (k,l), and HAADF-STEM elemental mapping (m) of RBNM/CNTs500.

Fig. 2. Phase and surface chemical characterization of RBNM/CNTsx. PXRD patterns (a), Raman spectra (b), N2 adsorption-desorption isotherms (c), and high resolution XPS spectra of Ni 2p (d), Mo 3d (e), Ru 3p (f), N 1s (g), B 1s (h), O 1s (i), C 1s + Ru 3d (j), and water contact angle measurements (k) for RBNM/CNTs500.

Fig. 3. Evaluation of HER performance and durability in 1.0 mol L?1 KOH electrolyte. (a) LSV curves. (b) Corresponding overpotential values with error bars from multiple repeated experiments. (c) Comparison of η10 for RBNM/CNTs500 in HER with recently reported NF-based electrocatalysts (references in the Supporting Information). (d) Tafel plots. (e) CV curves. (f) Cdl values. (g) EIS data for synthesis catalyst. (h) Multistep CP test at current densities from 10 to 50 mA cm?2. (i) Long-term CA test of RBNM/CNTs500 at 100 mA cm?2 (inset: LSV curves before and after the 100-h stability test).

Fig. 4. Evaluation of OER performance and durability in 1.0 mol L?1 KOH electrolyte. (a) LSV curves. (b) Corresponding overpotential values with error bars from multiple repeated experiments. (c) Comparison of η10 for RBNM/CNTs500 in HER with recently reported NF-based electrocatalysts (references in the Supporting Information). (d) Tafel plots. (e) CV curves. (f) Cdl values. (g) EIS data for synthesis catalyst. (h) Multistep CP test at current densities from 10 to 50 mA cm?2. (i) Long-term CA test of RBNM/CNTs500 at 100 mA cm?2 (inset: LSV curves before and after the 100-h stability test).

Fig. 5. Overall water splitting results. (a) Schematic of the electrolytic water electrolyzer. (b) LSV curves of the two electrode electrolyzer. (c) Photograph of the RBNM/CNTs500‖RBNM/CNTs500 electrolyzer powered by a single commercial 1.5 V battery. (d) LSV curve under simulated industrial conditions. (e) Cell voltage comparison with recently reported noble-metal-based catalysts at 1 A cm?2. (f) Gas collection in an H-type cell: measured gas volumes and corresponding Faradaic efficiencies. (g) Long-term chronopotentiometry test at 1 A cm?2 for 120 h under simulated industrial conditions.

Fig. 6. DFT calculations. (a) Gibbs free energy diagram for the HER. (b) Gibbs free energy diagram for H2O dissociation. (c) Gibbs free energy diagram for the OER. (d) Top and side views of the optimized structures of Ru, Ru/B,N-MoO2@CNTs, and Ru/B,N-MoO2@CNTs-Ov. (e) Charge density difference plots (top and side views) of Ru/B,N-MoO2@CNTs and Ru/B,N-MoO2@CNTs-Ov, where yellow and blue regions denote electron accumulation and electron depletion, respectively. (f) Bader charge analysis of Ru, Mo, O, B, N, and neighboring C atoms in Ru/B,N-MoO2@CNTs and Ru/B,N-MoO2@CNTs-Ov.

Fig. 7. Electrochemical performance of the water-splitting cells. (a) Schematic illustration of the AEMWE setup. Polarization curves of RBNM/CNTs500 in 1.0 and 6.0 mol L?1 KOH at 25 and 60 °C (without iR correction). (b) LSV curves for HER. (c) Summary of HER overpotentials. (d) LSV curves for OER. (e) Summary of OER overpotentials. (f) OWS performance of the RBNM/CNTs500(+)‖RBNM/CNTs500(-) configuration. (g) Summary of cell voltages required for overall water splitting. (h) Durability measurements of the AEMWE cell in 6.0 mol L?1 KOH at 60 °C.

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