Bridging the temperature and pressure gaps: Close-packed transition metal surfaces in an oxygen environment

An understanding of the interaction of atoms and molecules with solid surfaces on the microscopic level is of crucial importance to many, if not most, modern high-tech materials applications. Obtaining such accurate, quantitative information has traditionally been the realm of surface science experiments, carried out under ultra-high vacuum conditions. Over recent years scientists have realized the importance of obtaining such knowledge also under the high pressure and temperature conditions under which many industrial processes take place, e.g. heterogeneous catalysis, since the material under these conditions may be quite different to that under the conditions of typical surface science experiments. Theoretical studies too have been aimed at bridging the so-called pressure and temperature gaps, and great strides have been made in recent years, often in conjunction with experiment. Here we review recent progress in the understanding of the hexagonal close-packed surfaces of late transition and noble metals in an oxygen environment, which is of relevance to many heterogeneous catalytic reactions. In many cases it is found that, on exposure to high oxygen pressures and elevated temperatures, thin oxide-like structures form which may or may not be stable, and which may have little similarity to the bulk oxides, and thus possess unique chemical and physical properties.