Platinum-germanium catalysts supported on carbon were synthesised from organometallic precursors using surface organometallic chemistry (SOMC). The catalysts were characterised using chemisorption, X-ray absorption spectroscopy, transmission electron microscopy, energy dispersive X-ray analysis, X-ray diffraction and cyclic voltammetry. Physical characterisation provided evidence for the selective deposition of the germanium with the platinum using SOMC, existing mainly as platinum metal in association with GeO2. From anodic stripping cyclic voltammetry it can be inferred that the presence of GeO2, at the platinum sites changes the CO oxidation profile of strongly adsorbed CO, increasing its oxidation at 0.68 V versus RHE relative to the main oxidation at 0.85 V versus RHE. The peak potentials appear to be independent of the germanium loading; however, significant changes were observed in the peak current densities, with an increased promotional effect at higher germanium content. We believe the change in the relative distribution between these sites is mainly due to changes in the surface structure of the platinum on addition of GeO2. Further promotional activity is seen, with a limited oxidation activity evident at an onset of 0.35 V versus RHE. (C) 2001 Elsevier Science Ltd. All rights reserved.