Abstract
Phase control plays an important role in the precise synthesis of inorganic materials, as the phase structure has a profound influence on properties such as conductivity and chemical stability. Phase-controlled preparation has been challenging for the metallic-phase group-VI transition metal dichalcogenides (the transition metals are Mo and W, and the chalcogens are S, Se and Te), which show better performance in electrocatalysis than their semiconducting counterparts. Here, we report the large-scale preparation of micrometre-sized metallic-phase 1T′-MoX2 (X = S, Se)-layered bulk crystals in high purity. We reveal that 1T′-MoS2 crystals feature a distorted octahedral coordination structure and are convertible to 2H-MoS2 following thermal annealing or laser irradiation. Electrochemical measurements show that the basal plane of 1T′-MoS2 is much more active than that of 2H-MoS2 for the electrocatalytic hydrogen evolution reaction in an acidic medium.
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Acknowledgements
This work was supported by MOE under AcRF Tier 2 (ARC 19/15, nos. MOE2014-T2-2-093, MOE2015-T2-2-057 and MOE2016-T2-2-103) and AcRF Tier 1 (2016-T1-001-147 and 2016-T1-002-051), and NTU under a Start-Up Grant (M4081296.070.500000) in Singapore. It was also supported by the Joint Research Fund for Overseas Chinese, Hong Kong and Macao Scholars (grant no. 51528201). Q.X. acknowledges support from the Singapore National Research Foundation via an NRF Investigatorship Award (NRF-NRFI2015-03), Singapore MOE AcRF Tier2 grant (MOE2015-T2-1-047) and Tier1 grant (RG 113/16). Z.L. acknowledges support from the Singapore National Research Foundation under NRF RF award no. NRF-RF2013-08. The authors acknowledge the Facility for Analysis, Characterization, Testing and Simulation at Nanyang Technological University, Singapore, for use of their electron microscope (and/or X-ray) facilities.
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H.Z. proposed the research direction and guided the project. Y.Y., G.-H.N., Q.H. and X.-J.W. conceived the idea, designed the experiments and drafted the manuscript with H.Z., synthesized the materials, fabricated the devices, and analysed the data. K.Z. and Q.Z. helped with Raman and photoluminescence mapping measurements. X.W. and Q.X. conducted the temperature-dependent electrical property measurements. Z.Y. and L.G. carried out the STEM characterization. J.C., Q.M., M.Z. and Z.L. helped draft the manuscript. B.L. carried out XPS characterization. F.-R.R. and H.L. carried out AFM characterization. Y.D. analysed the XAFS results. Z.L., X.H. and W.H. helped revise the manuscript. All authors read the manuscript and agreed with its content.
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Supplementary synthesis, characterization details, electrochemical measurements and analysis; Supplementary Figures 1–17 and Supplementary Tables 1 & 2
Supplementary Video
In situ Raman observation of the phase transformation process from 1T’-MoS2 to 2H-MoS2 under laser irradiation
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Yu, Y., Nam, GH., He, Q. et al. High phase-purity 1T′-MoS2- and 1T′-MoSe2-layered crystals. Nature Chem 10, 638–643 (2018). https://doi.org/10.1038/s41557-018-0035-6
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DOI: https://doi.org/10.1038/s41557-018-0035-6
