Research Fellows Directory
Dr David Payne
Imperial College London
The amount of energy in sunlight striking the Earth in one hour is roughly equivalent to the amount of energy consumed on the planet in an entire year! A major challenge, therefore, is to be able to convert a source of practically limitless energy (i.e. the sun) into chemical energy (i.e. hydrogen) with very little or no carbon footprint. The current aim of this research is to try to develop materials that can split water using sunlight, generating hydrogen and oxygen, so called photoelectrochemical (PEC) water splitting. It was first discovered in 1971, by Fujishima and Honda, with TiO2. The basis of PEC is that a photon is absorbed by a material, which excites an electron from a bonding state, to an anti-bonding state at higher energy, leaving behind a ''hole'' in the process. This electron-hole pair are free to diffuse through the solid, and if they reach the surface they can respectively reduce and oxidize water giving H2 and O2. Since this work in 1971, there have been extensive studies to try to develop materials with high QEs, making the process commercially viable. While it is possible for materials to show QEs above 90% in UV light, this constitutes only 5% of the terrestrial solar spectrum. The greatest goal is to develop high QE materials that split water efficiently in visible light. Unfortunately, the materials most suitable for photocatalytic water splitting, oxides, absorb mainly in the UV region. One focus of my research is to design and synthesize materials that combine the photo-stability of oxides with the visible light absorbance of nitrides/sulphides.
The benefits to society if a clean, renewable and cheap source of energy can be discovered is immeasurable. Solar water splitting has the potential to revolutionise society, enabling a reduction CO2 emissions and associated climate change, as well as limiting the social and economic instabilities associated with global (limited) fossil fuel reserves.
Interests and expertise (Subject groups)