四硫代钼酸铵合成

Received 24th October 2013 Accepted 14th December 2013 DOI: 10.1039/c3ta14313a www.rsc.org/MaterialsA
Introduction
As a typical transition metal dichalcogenide, molybdenum disulde has been extensively researched as a catalyst1–3 and as a lubricant.4–6 This kind of material comprises layers of molybdenum atoms sandwiched with sulfur atoms, and the layers interact only via van der Waals.7 The adjacent force is so weak that the MoS2 layers are easily exfoliated into so-called MXene like graphene.8,9 Similar to graphene, the two-dimensional inorganic graphene-like material has potential to show unique functions in application elds, such as electronic devices10,11 and gas sensors.12 However, knowledge on the different morphology of molybdenum disulde is still nite at present. Recently, it has been found that molybdenum disulde is efficient as a counter electrode material, replacing platinum in dye-sensitive solar cells (DSSCs).13,14 As an important component, the counter electrode in DSSCs promotes the electron translocation from the external circuit back to the redox electrolyte, and catalyzes the reduction of triiodine ions.15–17 This
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J. Mater. Chem. A, 2014, 2, 3919–3925 | 3919
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process is a necessary step for charge transport in the interior of DSSCs, directly related to the energy conversion efficiency of the solar cells. Therefore, the catalytic activity of the counter electrode materials is crucial for the photoelectrochemical performance of DSSCs.18–20 Usually, the catalytic activity of a certain material is affected by multifarious factors, like the specic surface area, porosity and crystal plane orientation. For a layered material, the number of layers and orientation should be important for the catalytic performance. As reported, monolayered nanosheets of chemically exfoliated tungsten disulde provide an enhanced catalytic activity for hydrogen evolution.21 Thus, it is interesting to understand the catalytic behaviour of molybdenum disulde with different morphologies as a counter electrode for DSSCs. In this work, few-layered MoS2 (FL-MoS2) with a twodimensional feature was prepared by exfoliating multilayered MoS2 (ML-MoS2), and small-sized MoS2 nanoparticles (MoS2NPs) were also synthesized by the decomposition of ammonium tetrathiomolybdate. The molybdenum disuldes with different morphologies were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2-adsorption. As counter electrode materials, the molybdenum disuldes were evaluated by the measurement of the corresponding DSSCs. Based on the electrochemical impedance spectra (EIS), the relationship between the morphology and catalytic activity of the molybdenum disuldes is discussed, and catalytic active sites for the reduction of triiodine ions are proposed.
Cite this: J. Mater. Chem. A, 2014, 2, 3919
MorphoLeabharlann Baiduogy dependence of molybdenum disulfide transparent counter electrode in dye-sensitized solar cells†
B. Lei, G. R. Li* and X. P. Gao
Molybdenum disulfide attracts additional attention due to its layered structure which allows transformation into a two-dimensional morphology, like graphene. In this paper, three kinds of molybdenum disulfides with distinguishable morphologies, i.e. multilayers, a few layers and nanoparticles, are prepared and used as counter electrode materials for dye-sensitized solar cells (DSSCs). The characterization results from X-ray diffraction (XRD) and transmission electron microscopy (TEM) demonstrate that the molybdenum disulfides have an obviously different edge area to basal-plane ratio, with the order: synthesized MoS2 nanoparticles (MoS2-NPs) > multilayered MoS2 (ML-MoS2) > few-layered MoS2 (FL-MoS2). It is interesting that the MoS2 counter electrodes show the same order as above in the energy conversion efficiency measurements of the corresponding DSSCs. Electrochemical impedance spectra (EIS) show that the MoS2-NPs electrode has the minimum charge-transfer resistance, while the FL-MoS2 electrode provides the maximum. Combined with the results from triiodine ion adsorption experiences and N2-adsorption measurements, it is proposed that the catalytically active sites of molybdenum disulfide lie on the edges of the typical layered material, but not on the basal planes. In addition, the transparency of the FL-MoS2 electrode is obviously higher than that of the other MoS2 and Pt electrodes.
Institute of New Energy Material Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin Key Laboratory of Metal and Molecule Based Material Chemistry, Nankai University, Tianjin 300071, China. E-mail: guoranli@nankai.edu.cn; Fax: +86-22-23500876; Tel: +86-22-23500876 † Electronic supplementary 10.1039/c3ta14313a information (ESI) available. See DOI: