Inelastic neutron scattering has been used to study adsorbed species on catalysts for more than 30 years. All of this work has one feature in common: they are all ¿snapshots¿ of the catalyst in that reaction is carried out at elevated temperature (300 K or above) and either the adsorbate is stable on the catalyst or a working catalyst is quenched and the spectra are recorded at low temperature. The aim of this proposal is to exploit the ability of MAPS to access low Q to minmise the effect of temperature on the Debye-Waller factor in order to carry out the first INS in operando study of a working catalyst at room temperature. The reaction chosen is the low temperature catalytic oxidation of carbon monoxide over hydrous palladium oxide powder. The key species are surface hydroxyls which give either adsorbed bicarbonate or formate intermediates, all of which have distinct INS spectra.