SnS 2 nanoplate-like products were fabricated via a facile hydrothermal process of a mixed solution containing SnCl 4 and thiourea (SC(NH 2 ) 2 ) without organic capping agent, and their composition, crystallinity, and morphology can be adjusted by varying the SC(NH 2 ) 2 /SnCl 4 molar ratio. In particular, regular hexagon-shaped SnS 2 nanoplates with an average size of ∼275 nm and thickness of ∼56 nm were attained when the SC(NH 2 ) 2 / (SnCl 4 ) molar ratio is 6:1. The obtained SnS 2 nanoplates exhibit layered structures with exposed {001} facets and a single-crystalline feature, and its growth mechanism was proposed according to the hydrothermal time-dependent experimental results. The regular hexagon-shaped SnS 2 nanoplates achieve high photocatalytic H 2 production activity of 356 μmol h −1 under visible light (λ ≥ 420 nm) irradiation, much better than that of the irregular nanoplate-like products. The higher crystallinity and fewer defects of the regular hexagon-shaped SnS 2 nanoplates compared to the irregular ones can more efficiently retard the photogenerated charge recombination, while the S atoms with higher density in the exposed {001} facets might be beneficial for the formation of H bonds with H 2 O molecules, which then cause good dispersity and photocatalytic activity for H 2 production of the SnS 2 nanoplates. These results demonstrate the potential application of SnS 2 nanoplates in the photocatalytic H 2 production field, and might provide guidance to the controllable syntheses of the family of MS 2 photocatalysts with a highly efficient H 2 production property.
Magnetocaloric materials can be useful in magnetic refrigeration applications, but to be practical the magneto-refrigerant needs to have a very large magnetocaloric effect (MCE) near room temperature for modest applied fields (<2 Tesla) with small hysteresis and magnetostriction, and should have a complete magnetic transition, be inexpensive, and environmentally friendly. One system that may fulfill these requirements is Mn x Fe 2-x P 1-y Ge y , where a combined first-order structural and magnetic transition occurs between the high temperature paramagnetic and low temperature ferromagnetic phase. We have used neutron diffraction, differential scanning calorimetry, and magnetization measurements to study the effects of Mn and Ge location in the structure on the ordered magnetic moment, MCE, and hysteresis for a series of compositions of the system near optimal doping. The diffraction results indicate that the Mn ions located on the 3f site enhance the desirable properties, while those located on the 3g sites are detrimental. The entropy changes measured directly by calorimetry can exceed 40 J/kg·K. The phase fraction that transforms, hysteresis of the transition, and entropy change can be controlled by both the compositional homogeneity and the particle size, and an annealing procedure has been developed that substantially improves the performance of all three properties of the material. On the basis of these results we have identified a pathway to optimize the MCE properties of this system for magnetic refrigeration applications.
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