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Title: Novel chalcogenide nanomaterials production and application
Author: Prabakaran, Arunvinay
ISNI:       0000 0004 6346 4910
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2015
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In this work, chemical vapour deposition (CVD) using chloride precursors has been employed for the synthesis of various nanostructures of tungsten disulphide (WS2). By tuning the synthesis conditions and precursors, the process was successfully employed for synthesis of 3D nanoflowers of WS2, 2D WS2 domains and mixed metal dichalcogenides of Mo and W. The structural evolution of the nanoflowers has been presented along with the composition changes which sheds light on the nucleation and growth mechanism. The presence of few-layered WS2 along the edges of the nanoflowers was revealed using high resolution microscopy. Various exfoliation techniques were employed to isolate these nanosheets from the nanoflower. Solvent exfoliation produced a cluster of nanosheets with increased amount of edge sites which exhibited excellent catalytic activity for hydrogen evolution reaction (HER) when in combination with commercial fuel cell grade carbon black (BP 2000), shown by studies using a electrochemical setup. The growth of 2D WS2 domains was also investigated using a similar CVD strategy, as employed for nanoflowers, to study the influence of various parameters such as sulphur sublimation temperature, synthesis temperature, time period, substrates position and precursors on the final deposit. It was observed that the shape, thickness and size of the domains vary within the substrates depending on the growth condition and parameters. The composition-controlled synthesis of MoxW1-xS2 was achieved by employing the same atmospheric-pressure CVD using Mo and W chloride precursors. By controlling the sublimation temperature of the precursors it was shown that the growth temperature, which was varied from 650 °C to 800 °C, dictates the alloy composition with W dopant composition varied from as little as a few percent (x=0.98), to over 50% (x=0.42). This work shows the versatility of the CVD process to produce different morphologies of WS2- 3D nanoflowers to 2D domains- making it ideal for wide range of applications from catalysis to optoelectronic devices, and could be extended for synthesis of analogous TMD compounds.
Supervisor: Grobert, Nicole ; Dillon, Frank Sponsor: Felix Scholarship ; Royal Society ; European Research Council ; Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available