In situ Raman spectroscopy, temperature programmed desorption (TPD) and scanning electron microscopy (SEM) were used to study the interaction of an electrolytic silver catalyst with O-2 at atmospheric pressure and temperatures between 300 and 923 K. Raman spectroscopy and TPD were applied to characterise the chemisorbed oxygen species formed during catalyst exposure to O-2 under these conditions. SEM was used to examine changes in catalyst morphology caused by high temperature oxygen treatment. The silver catalyst chemisorbed oxygen in a variety of distinct states over the temperature range examined. Oxygen species, identified on the basis of their vibrational and thermal desorption spectra, were a molecular superoxo species, weakly chemisorbed surface atomic oxygen (O-alpha), strongly chemisorbed surface atomic oxygen (O-gamma) and subsurface oxygen (O-beta). The thermal stability and formation conditions of each species were established through a combination of in situ Raman and TPD data. With heating in O-2 at 923 K, the silver catalyst restructured to form well-defined surface facets of dimension 1-2 mum. The influence of the restructuring on the oxygen chemisorptive properties of the silver catalyst is discussed. The results of these studies were used to develop a scheme for the interaction of O-2 with silver surfaces at 923 K. (C) 2003 Elsevier Science B.V. All rights reserved.