With a new set-up for in situ EXAFS spectroscopy the state of a carbon-supported platinum catalyst during aqueous alcohol oxidation has been observed. The catalyst deactivation during platinum-catalysed cyclohexanol oxidation is caused by platinum surface oxide formation. The detected Pt-O co-ordination at 2.10 Angstrom during exposure to nitrogen-saturated cyctohexanol solution is different from what is observed for the pure oxidised platinum surface (2.06 Angstrom).