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 923K. 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 α ), strongly chemisorbed surface atomic oxygen (O γ ) and subsurface oxygen (O β ). 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 923K, the silver catalyst restructured to form well-defined surface facets of dimension 1-2μm. 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 923K.