2015 Tabor Medal and Prize

Professor Geoffrey Thornton, University College London, for his contributions to understanding the physics and chemistry of oxide surfaces, using both scanned-probe and reciprocal-space techniques.

Professor Geoffrey Thornton

Geoff Thornton’s work on the surface chemical physics of metal oxides has played a significant role in establishing the field, pioneering the link between a surface’s electronic and atomic structure and its reactivity. In so doing he has consistently been at the forefront of instrument developments, most notably those involving synchrotron radiation techniques and scanning probes, particularly Scanning Tunnelling Microscopy (STM) and Non-Contact Atomic Force Microscopy. Indeed, it has been the combination of these two approaches that has been so very powerful.

The breakthrough came with the first representative atomically resolved images of a metal oxide surface. These were of ordered O vacancies on the (100) surface of TiO2. His group’s seminal paper in 1995 on what has become the model oxide surface, TiO2 (110), described all the major elements present on that surface as a function of O vacancy density. Defects on oxide surfaces have long been thought to be involved in determining their reactivity; by monitoring the reaction of H2O with TiO2 (110), Thornton’s group was able to observe, for the first time, bridging OH species being formed by dissociation of water molecules at O vacancies. In a form of single-molecule chemistry, his group observed individual vacancies being transformed into OH as a water molecule dissociated in the vacancy.

More recently, in another significant breakthrough, they distinguished vacancies and OH groups (which appear similar in STM images) from one another. They also associated these species with electron trapping centres that give rise to a bandgap electronic state – a discovery that transforms the understanding of the surface’s reactivity.

Taken together, this body of work is a cornerstone of our modern understanding of the role of defects in the reactivity of the model photocatalyst TiO2, with wide implications for general models of catalysis and for potential future energy conversion technologies.