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Open AccessArticle

Structure of Nanocrystalline, Partially Disordered MoS2+δ Derived from HRTEM—An Abundant Material for Efficient HER Catalysis

1
Institute of Materials Physics, University of Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
2
Institute for Inorganic and Analytical Chemistry and Freiburg Material Research Center (FMF), University of Freiburg, Albertstraße 21, 79104 Freiburg, Germany
3
GZG Crystallography University of Göttingen, Goldschmidtstr. 1, 37077 Göttingen, Germany
4
International Center for Advanced Studies of Energy Conversion (ICASEC), University of Göttingen, D-37077 Göttingen, Germany
*
Authors to whom correspondence should be addressed.
Catalysts 2020, 10(8), 856; https://doi.org/10.3390/catal10080856
Received: 5 June 2020 / Revised: 23 July 2020 / Accepted: 28 July 2020 / Published: 1 August 2020
(This article belongs to the Section Electrocatalysis)
Molybdenum sulfides (MoSx, x > 2) are promising catalysts for the hydrogen evolution reaction (HER) that show high hydrogen evolution rates and potentially represent an abundant alternative to platinum. However, a complete understanding of the structure of the most active variants is still lacking. Nanocrystalline MoS2+δ was prepared by a solvothermal method and immobilized on graphene. The obtained electrodes exhibit stable HER current densities of 3 mA cm−2 at an overpotential of ~200 mV for at least 7 h. A structural analysis of the material by high-resolution transmission electron microscopy (HRTEM) show partially disordered nanocrystals of a size between 5–10 nm. Both X-ray and electron diffraction reveal large fluctuations in lattice spacing, where the average c-axis stacking is increased and the in-plane lattice parameter is locally reduced in comparison to the layered structure of crystalline MoS2. A three-dimensional structural model of MoS2+δ could be derived from the experiments, in which [Mo2S12]2− and [Mo3S13]2− clusters as well as disclinations represent the typical defects in the ideal MoS2 structure. It is suggested that the partially disordered nanostructure leads to a high density of coordinatively modified Mo sites with lower Mo–Mo distances representing the active sites for HER catalysis, and, that these structural features are more important than the S:Mo ratio for the activity. View Full-Text
Keywords: hydrogen evolution catalysis; molybdenum sulfides; nanocrystalline materials hydrogen evolution catalysis; molybdenum sulfides; nanocrystalline materials
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Ronge, E.; Hildebrandt, S.; Grutza, M.-L.; Klein, H.; Kurz, P.; Jooss, C. Structure of Nanocrystalline, Partially Disordered MoS2+δ Derived from HRTEM—An Abundant Material for Efficient HER Catalysis. Catalysts 2020, 10, 856.

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