The chemical inertness of the defect-free basal plane confers environmental stability to MoS2 single layers, but it also limits their chemical versatility and catalytic activity. The stability of pristine MoS2 basal plane against oxidation under ambient conditions is a widely accepted assumption however, here we report single-atom-level structural investigations that reveal that oxygen atoms spontaneously incorporate into the basal plane of MoS2 single layers during ambient exposure. The use of scanning tunnelling microscopy reveals a slow oxygen-substitution reaction, during which individual sulfur atoms are replaced one by one by oxygen, giving rise to solid-solution-type 2D MoS2−xOx crystals. Oxygen substitution sites present all over the basal plane act as single-atom reaction centres, substantially increasing the catalytic activity of the entire MoS2 basal plane for the electrochemical H2 evolution reaction.
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This work was performed in the framework of a NanoFab2D ERC starting grant, H2020 Graphene Core2 project no. 785219 and the Korea Hungary Joint Laboratory for Nanosciences. L.T. acknowledges OTKA grant K108753 and the ‘Lendület’ programme. The work was also supported by a VEKOP-2.3.2-16-2016-00011 grant, supported by the European Structural and Investment Funds. Z.I.P. and P.B.S. acknowledge financial support from the Ministry of Education and Science of the Russian Federation in the framework of the Increase Competitiveness Program of NUST ‘MISIS’ (no. K2-2017-001). Z.I.P. and P.B.S. acknowledge the supercomputer cluster provided by the Materials Modelling and Development Laboratory at NUST “MISIS” (supported via a grant from the Ministry of Education and Science of the Russian Federation no. 14.Y26.31.0005), and the Information Technology Centre of Novosibirsk State University for providing access to the cluster computational resources. Z.I.P. acknowledges the financial support of the Russian Scientific Foundation according to research project no. 18-73-10135 for stability calculations. P.V. acknowledges the Plateforme Technologique de Calcul Intensif (PTCI), which was supported by the FRS-FNRS under convention no. 2.5020.11. P.B.S. acknowledges financial support from the RFBR, via research project no. 16-32-60138 mol_а_dk. The authors thank J. S. Pap for useful discussions on electrochemistry.
Supplementary Figures 1–15, Supplementary Methods, Supplementary Characterization
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Microscopic insights into the catalytic mechanisms of monolayer MoS2 and its heterostructures in hydrogen evolution reaction
Nano Research (2019)
Nature Reviews Chemistry (2018)