Cuddy, Martin (2014). Size-selected molybdenum disulfide clusters for hydrogen evolution. University of Birmingham. Ph.D.
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Cuddy14PhD.pdf
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Abstract
In this work, size-selected molybdenum disulfide (MoS2) nanoclusters were produced using a magnetron sputter source and time-of-flight mass filter. Magnetron sputtering is a common industrial method for preparation of MoS2 thin films. The combination of this technology with accurate size control allows us to produce, in high vacuum, lab-scale quantities of size-selected clusters. The strong spatial confinement effects in MoS2 suggests that such control will modify the catalytic properties. This method also has potential to enhance MoS2 performance in areas such as hydrodesulfurisation, intercalation batteries and tribology; as well as elucidating the dynamics of compound formation in the gas-phase.
Structural properties of these MoS2 clusters are studied using aberration-corrected STEM. The optimum catalytic size range of 1-5nm has not previously been studied in detail for gas phase synthesis. This work bridges the gap in the cluster beam literature between small, few atom clusters and the production of large MoS2 fullerenes and monolayers.
It has been found that MoS2 clusters display a characteristic layered structure down to the smallest studied cluster, 50 units of MoS2. Growth of clusters is indicative of anisotropic growth from the reactive edge sites, proceeds by subsequent addition of van der Waals bound layers and finally coalescence of smaller units in the case of large clusters. The electrocatalytic properties of these clusters are explored by cyclic voltammetry and show good activity for the Hydrogen Evolution Reaction despite the presence of surface oxides. The reaction current normalised matches to loading matches some of the best catalysts produced to date.
| Type of Work: | Thesis (Doctorates > Ph.D.) | |||||||||
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| Award Type: | Doctorates > Ph.D. | |||||||||
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| College/Faculty: | Colleges (2008 onwards) > College of Engineering & Physical Sciences | |||||||||
| School or Department: | School of Chemical Engineering | |||||||||
| Funders: | None/not applicable | |||||||||
| Subjects: | T Technology > TP Chemical technology | |||||||||
| URI: | http://etheses.bham.ac.uk/id/eprint/5210 |
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