Synthesis and Characterization of Template-Free VS4 Nanostructured ...

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Synthesis and Characterization of Template-Free VS4 Nanostructured Materials with Potential Application in Photocatalysis Gregory Lui,† Gaopeng Jiang,† Aoshu Duan,‡ Josh Broughton,† Jason Zhang,‡ Michael W. Fowler,*,† Aiping Yu*,† †

Department of Chemical Engineering, University of Waterloo, Canada; ‡Department of

Chemical Engineering, University of Ottawa, Canada.

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Figure S1. SEM image of VS4 material after UV irradiation (a) and XRD spectra showing minimal crystallinity change of VS4 material before and after UV irradiation (reference VS4 spectra [JCPDS: 01-072-1294] is also included) (b).

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Figure S2. EDX spectra of VS4 material before (a) and after (b) UV irradiation. EDX shows near stoichiometric V:S ratio for VS4. After UV irradiation, amount of vanadium increases, which can be an indication of sulfur reduction.

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Possible Reaction Pathways for VS4 In a highly reducing environment, orthovanadate and hydrogen sulfide can react together to form both V2S3 and elemental sulfur. These products can then react together to form VS4. 2VO43– + 5HS– + 3H2O → V2S3 + S + 11OH–

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V2S3 + 5S → 2VS4

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Thioacetamide can be hydrolyzed in both acidic and alkaline conditions to form acetate, ammonium and hydrogen sulfide (H2S, HS–).1 It is therefore suggested that under alkaline conditions the oxidation of HS– to HS• can lead to the formation of S22– via the dimerization of S•– or the formation and decomposition of H2S2.2 This phenomenon is especially true in alkaline conditions, however it is also possible in acidic conditions. H2S can be oxidized to form H2S•+, which immediately dissociates to form a HS• radical – and this radical can proceed to form S22– as in alkaline conditions. Radical formation in alkaline solution: H2S + H2O → H3O+ + HS–

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HS– → HS• + e–

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Radical formation in acidic solution: H2S → H2S•+ + e–

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H2S•+ + H2O → H3O+ + HS•

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Disulfur dianion formation:

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HS• ↔ S•– + H+

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2S•– → S22–

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A basic precipitation test using BaCl2 revealed that sulphate ions exist in the product solution as sulphate(IV), which is in agreement with Feng and coworkers.3 Therefore, a simplified reaction pathway for the formation of VS4 may be described by the following reaction: 10VO43– + 21S22– + 34H2O → 10VS4 + 2SO32– + 68OH–

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REFERENCES (1)

Lehrman, L., Thioacetamide as a source of hydrogen sulfide in qualitative

analysis. J. Chem. Educ. 1955, 32, 474. (2)

Steudel, R., Mechanism for the Formation of Elemental Sulfur from Aqueous

Sulfide in Chemical and Microbiological Desulfurization Processes. Ind. Eng. Chem. Res. 1996, 35, 1417. (3)

Feng, J.; Sun, X.; Wu, C.; Peng, L.; Lin, C.; Hu, S.; Yang, J.; Xie, Y., Metallic

Few-Layered VS2 Ultrathin Nanosheets: High Two-Dimensional Conductivity for In-Plane Supercapacitors. J. Am. Chem. Soc. 2011, 133, 17832.

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