Our current research topics cover a broad range of interests and activities, from Metal-Insulator Transitions (MITs) to sustainable and renewable chemistry for energy. A brief summary of areas of interest are presented below:
1. Turning Insulators into Metals
There are numerous systems and materials for which small changes in temperature, pressure or composition can transform a non-metallic (insulating) material into a highly conducting metallic state. C.N.R. Rao of Bangalore has drawn a graphic analogy, noting this process is akin to "Turning Wood into Copper". A detailed understanding of this remarkable electronic phase transition is one of our major interests.
2. Hydrogen Storage in Solids
One of the most extensive research interests in the group is into the storage of hydrogen in solids, in conjunction with Prof. Bill David and the Rutherford-Appleton Laboratory. Hydrogen is widely regarded as the most promising alternative to carbon-based fuels since it will help alleviate the inevitable environmental and energy supply concerns when fossil fuels become scarce and/or unsustainable, due to ecological and energy/security reasons. Hydrogen is ideal as a synthetic fuel; it is light weight, highly abundant -recall, hydrogen is the most abundant element in the universe- and when used as an energy carrier it generates no emissions other than normally benign water molecules.
This research theme encompasses Carbon Materials, Metal Hydrides, Borohydrides, Amidoboranes, Amide Systems, Alanates and Metal Borohydride/Halide Ammines for Hydrogen Storage. At the heart of the activity is an attempt to understand -and hence control- the micro-, meso-, and nano-structure of low atomic number hydrogen storage materials. To achieve a breakthrough requires a suitable storage material of 6-7 weight percent hydrogen!
3. Turning Carbon Dioxide into Fuel
A major initiative with Dr. Tiancun Xiao has been formed between Oxford and the King Abdulaziz City for Science and Technology (KACST), which aims to promote frontier scientific and technological challenges associated with clean energy from fossil fuels. These include:
- Development of new-generation catalysts based on meso-porous solids;
- Fuel economy materials
- Tri-reforming techniques for CO2 conversion
This project is part of an global initiative to implement the ‘hydrogen economy’ in a pragmatic sense, whereby hydrogen is placed in the fuel rather than used as the fuel.
4. Transparent, but Highly Conducting Metal Oxides
Transparent conductors (TC) are extremely important functional materials, with applications in many industries. The most important TC is indium tin oxide (ITO), as it possesses the ideal
combination of optical transparency and high conductivity. However, indium is extremely costly and thus it would be beneficial if indium free or reduced-indium TCs, with similar or better electrical properties, could be produced. To that end our research encapsulates:
- Increased electron mobility, and hence conductivity of ITO materials. Enhanced conductivity would lead to reduced film thickness, and thus reduced indium usage.
- Increased number of charge carriers (electrons). Similarly, increasing the number of charge carriers in ITO enhances conductivity.
- Synthesis and processing of new transparent conductor materials.
5. Bandgap Tuning for Photovoltaic and Photocatalytic Devices
The group focuses on two main areas of photo-active semiconductor research: the tuning of bandgaps in doped ZnO systems for photovoltaics, and p-n heterojunction systems for photocatalysis.
Doping of ZnO with sulphur to produce single crystal, orientated thin films is being investigated for application in the photovoltaic splitting of water to release hydrogen. Spray pyrolysis techniques are being developed to produce films of S/ZnO and the optical, crystallographic and defect properties of the films are examined.
We have also developed composite catalysts based around the n-type ZnFe2O4 and p-type BiOBr semiconductors for the purification of water by photodegradation of organic dyes such as Rhodamine B.
6. Metals in Ammonia: Solvated Electrons to Liquid Metals
Familiar from undergraduate courses (and all the way back to to the work of sir HumphryDavy in 1808!) are the beautiful blue and bronze colours of alkali metal-ammonia solutions. A thorough understanding of these complex systems, and the fascinating nature of their compositional metal-insulator transitions, is pursued in our group, whereby we study the chemistry and physics of alkali metals as solutes in ammonia/primary amines and associated systems.
- Detailed investigations of the nature of the solvated electron in alkali metal ammonia solutions using both ESR and NMR spetroscopies.
- The study of metal mixed solvent systems by ESR and NMR spetroscopies.
- The close examination of the phase separation boundary region of the sodium ammonia solution using various spectroscopic techniques.
- ESR measurements are carried out in conjunction with the Center for Advanced Electron Spin Resonance (CAESR) in Oxford.
7. Neutron Spectroscopy for Inorganic Systems
Neutron spectroscopy can be utilised in the study of the dynamics of proton-containing systems. We incorporate a variety of neutron techniques into the research of inorganic systems, as diverse as Li(NH3)4, NH3 coordinated within silicates, and metal hydrides. These techniques include quasielastic neutron scattering (QENS), inelastic neutron scattering (INS) and neutron Compton scattering (NCS), probing dynamics from nanosecond through to attosecond timescales.
8. The Continuing Challenge of High-Temperature Superconductivity
The observation, in 1987, of high-temperature superconductivity by J.G. Bednorz and K.A. Muller represents one of the greatest experimental discoveries of the last century. The phenomenon is simply not yet understood. Our project has the ultimate goal of a deep understanding of this fascinating natural phenomenon. We try to synthesize materials which we believe might be new superconductors. One recent example is a collaboration with Wojciech Grochala (Warsaw) and centres on fluoroargenates.