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MXenes with ordered triatomic-layer borate polyanion terminations


Surface terminations profoundly influence the intrinsic properties of MXenes, but existing terminations are limited to monoatomic layers or simple groups, showing disordered arrangements and inferior stability. Here we present the synthesis of MXenes with triatomic-layer borate polyanion terminations (OBO terminations) through a flux-assisted eutectic molten etching approach. During the synthesis, Lewis acidic salts act as the etching agent to obtain the MXene backbone, while borax generates BO2 species, which cap the MXene surface with an O–B–O configuration. In contrast to conventional chlorine/oxygen-terminated Nb2C with localized charge transport, OBO-terminated Nb2C features band transport described by the Drude model, exhibiting a 15-fold increase in electrical conductivity and a 10-fold improvement in charge mobility at the d.c. limit. This transition is attributed to surface ordering that effectively mitigates charge carrier backscattering and trapping. Additionally, OBO terminations provide Ti3C2 MXene with substantially enriched Li+-hosting sites and thereby a large charge-storage capacity of 420 mAh g−1. Our findings illustrate the potential of intricate termination configurations in MXenes and their applications for (opto)electronics and energy storage.

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Fig. 1: Synthesis of OBO-MXenes by the flux-assisted eutectic molten etching approach.
Fig. 2: Synthesis mechanism and characterizations of OBO-MXenes.
Fig. 3: Structural characterizations of OBO-MXenes.
Fig. 4: Charge-transport properties of OBO-MXenes.
Fig. 5: Charge-storage properties of OBO-Ti3C2.

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All data are available in the main text or the Supplementary Information. Source data are provided with this paper.


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We acknowledge support from European Union’s Horizon 2020 Research and Innovation programme (GrapheneCore3 881603, LIGHT-CAP 101017821, GREENCAP 101091572, X.F.), M-ERA.NET and Sächsisches Staatsministerium für Wissenschaft und Kunst (HYSUCAP 100478697, E.Z., T.Š., X.F.), and the German Research Foundation (DFG, CRC1415, grant number 417590517, E.B., M.Y., X.F.). TAČR EPSILON project (number TH71020004, T.Š.), GAČR project (number 23-07617 S, T.Š.) and CzechNanoLab project (number LM2023051, T.Š.) funded by MEYS CR are gratefully acknowledged for the financial support of the measurements in the CEITEC Nano Research Infrastructure. D.B. acknowledges support of computational resources in Mons by the FNRS ‘Consortium des Equipements de Calcul Intensif−CECI’ programme (grant number 2.5020.11) and by the Walloon Region (ZENOBE Tier-1 supercomputer, 1117545). D.L. acknowledges support from the China Scholarships Council (CSC). P.P.M. was supported by the National Science Centre (project number 2018/31/D/ST5/00399) and the National Centre for Research and Development (project number LIDER/8/0055/L-12/20/NCBR/2021). The authors acknowledge the use of the facilities at the Dresden Center for Nanoanalysis (DCN), Technische Universität Dresden, the Gemeinsamen Wissenschaftskonferenz (GWK) support for providing computing time through the Center for Information Services and High-Performance Computing (ZIH) at TU Dresden, and beam-time allocation at beamline P65 of the PETRA III synchrotron (DESY, Hamburg, Germany) and beamline BL04 of the ALBA synchrotron (Barcelona, Spain). We specially thank S. Voborný, P. Jadhao and P. Chen for helpful discussions.

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Authors and Affiliations



M.Y. and X.F. conceived and supervised the research. D.L. performed most of the experiments and analysis. W.Z., H.I.W. and M.B. performed the THz spectra test and analysis. S.M.G. and D.B. implemented the theoretical calculations. K.S., M.H., M.D., E.Z. and T.Š. conducted the transmission electron microscopy test and analysis. J.P. performed the XPS test. P.P.M. carried out the SIMS test. N.L. and E.B. conducted the solid-state NMR test. Z.L. and S.Z. carried out the electrical conductivity test. J.Z. assisted with XAS experiment. D.S. assisted with electrochemical experiments. D.L. prepared the paper under the supervision of M.Y. and X.F. All the authors read and revised the paper.

Corresponding authors

Correspondence to Hai I. Wang, David Beljonne, Minghao Yu or Xinliang Feng.

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Nature Materials thanks Michel Barsoum, Qing Huang and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Figs. 1–41 and Tables 1–9.

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Analysed data used to plot Fig. 2b–h.

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Analysed data used to plot Fig. 3e–h.

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Analysed data used to plot Fig. 5a,b,d–f.

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Li, D., Zheng, W., Gali, S.M. et al. MXenes with ordered triatomic-layer borate polyanion terminations. Nat. Mater. (2024).

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