9/26/2023 0 Comments Mose2 lattice constant![]() The metallic nature of 1T MoS 2 is expected to be responsible for H 2 evolution. 21 This was further improved by using 1T-MoS 2 prepared by the exfoliation of bulk MoS 2 by Li-intercalation. 13,18–21 It has been shown recently that the composite of MoS 2 with heavily nitrogen-doped graphene has an activity of 10.8 mmol h −1 g −1 and a turn over frequency of 2.9 h −1 under a 100 W halogen lamp. 15–17 Nanoparticles of 2H-MoS 2 as well as composites of 2H-MoS 2 with graphene and other materials have been employed as catalysts yielding 0.05–10 mmol h −1 g −1 of H 2 with a turn over frequency anywhere between 0.2 and 6 h −1. 8–10 MoS 2 has been widely used as a catalyst for electrochemical, photoelectrochemical, and photocatalytic H 2 generation from water 11–14 in consequence of having the conduction band minimum well above the H 2O reduction potential. While the 2H forms of these metal dichalcogenides are semiconducting, the 1T forms are metallic. Dichalcogenides of MoS 2 and WS 2 generally occur in the 2H form with the trigonal prismatic arrangement of hexagonal S–M–S (M = Mo/W) triple layers are among the most studied of the layered metal chalcogenides. 6,7 Exfoliation of these materials into single or few-layers often brings about drastic changes in the electronic structure as compared to the bulk species. Transition metal dichalcogenides of lamellar structure have gained attention recently because of their interesting electronic properties and easy availability. Majority of the metal sulfides however undergo photocorrosion during the hydrogen evolution reaction (HER). 4,5 Metal sulfides and selenides, on the other hand, have less positive valence bands making them visible light active. The intrinsic limitation of oxides is that they generally have a highly positive valence band (O 2 p), making it difficult to find a material which has both sufficiently negative conduction band to reduce H 2O to H 2 along with a sufficiently small bandgap to absorb visible light. Semiconducting oxide nanoparticles are one of the most common photocatalysts used for this purpose 2,3 and are preferred because they are chemically robust and stable against photocorrosion during water splitting. 1 Since then several inorganic catalysts have been used for photocatalytic, photoelectrochemical, and electrocatalytic production of H 2 from water. TiO 2 was the first material to be used as the photocatalyst for water-splitting. Various strategies which can be employed for this purpose like dye sensitization of semiconductors or use of light-harvesting semiconducting nanostructures. Artificial photosynthesis has been recognized as a potential means of water splitting.
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