Supervisors: Prof. R.E. Palmer, Dr B.G.Pollet, Prof. G. Li Puma
DTC Project - Towards Photocatalytic Water-Splitting by Size-Selected MoS2 Nanoclusters
Martin’s research project is to design and characterize the band-gap of molybdenum disulphide nanoparticles with regards to maximizing solar absorption and achieving chemical potential for splitting water using a high mass resolution nanocluster source and spectroscopic techniques. Once results in UHV indicate a successful nanocluster size and morphology he will chemically test the catalyst to confirm its real-world performance.
Production of hydrogen by photocatalytic splitting of water molecules requires a semiconductor material with a band structure that can supply excited carriers of the correct energy to split water as well as to absorb solar photons. One candidate material consists of size-selected nanoclusters of MoS2. The accurate size control will enable a study of the change in band-gap due to quantum confinement effects.
The nanoclusters are created by magnetron sputtering of a MoS2 disc to produce small cluster seeds, then by cryo-cooling in helium gas these seeds condense into larger nanoclusters. A novel lateral time-of-flight mass selector then disperses the nanoclusters so that only those of a certain size will be deposited on the final substrate. The morphology of the clusters can also be controlled to some extent by the deposition energy on the substrate, from soft-landing which retains their equilibrium shape to higher energy deposition to flatten them into oblate spheroids. The various cluster sizes can be characterised with spectroscopic techniques to identify the absorption characteristics. Microscopy by aberration-corrected Scanning Transmission Electron Microscopy (STEM) can provide structural information on the atomic scale. High Resolution Electron Energy Loss Spectroscopy (HREELS) provides analysis of surface molecular features and Scanning Probe Energy Loss Spectrometry (SPELS), using Scanning Tunneling Microscopy (STM) as an electron source for Electron Energy Loss Spectroscopy (EELS), can also provide spatially resolved spectroscopic data.
The results of this study highlight the size and structure dependence of this new material for hydrogen production and provide a detailed basis for the comparison with other candidate materials in current photocatalyst research.
Conferences and Events Attended:
Summer School “Reactivity of nanoparticles for more efficient and sustainable energy production” 2009 (Denmark)
6th International Hydrogen and Fuel Cell Conference (NEC, Birmingham)
7th International Hydrogen and Fuel Cell Conference (NEC, Birmingham)
Gordon Research Conference “Clusters, Nanocrystals & Nanostructures” (Mt. Holyoke College, MA, USA)
Impact of Research:
Presentation to Prof. Gianluca Li Puma (Loughborough University)
International collaboration with Catalysis for Sustainable Energy (CASE) group, producing catalysts by hydrothermal synthesis (DTU, Denmark)