Research Visit to Lawrence Berkeley Laboratory for Metal Oxide/Liquid Interfaces at the Advanced Light Source

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There is currently a large research effort associated with alternative energy technologies. Light harvesting is one avenue that is being vigorously pursued, where the aim is to convert energy from the sun into either electrical power or to generate hydrogen as a portable fuel. Both routes require a catalyst to harvest the light, with titanium dioxide being a key model system. Near UV-light is absorbed in a process where electrons are promoted across the band gap of this semiconductor. The electrons and holes then travel to surfaces where they create electrical current and do some chemistry, such as reduce water to hydrogen. In the photovoltaic application, a dye at the surface of TiO2 also absorbs visible light, which leads to an increase in efficiency. The photovoltaics market is estimated to be worth US$600 billion by 2030, building from about US$20 billion in 2010. This is one reason why research on Energy, including solar is an EPSRC priority area. Although the phenomenologies of light harvesting processes are well known, the details of the surface reactions are only now being revealed. What is known has been determined from experiments in the highly idealised conditions of ultra high vacuum. Experiments carried out in this project would examine the geometry of molecules related to dyes on the surface of TiO2, where the molecules are deposited from solution. The effect of the molecules on the electronic structure would also be monitored. These measurements are made possible by special instruments that employ synchrotron radiation to examine surfaces under liquid.