The effect of coadsorbed water on the stability, configuration and interconversion of formyl (HCO) and hydroxymethylidyne (COH) on platinum (1 1 1)

Two forms of the methanol electro-oxidation intermediate with stoichiometry C:H:O, COH (hydroxymethylidyne) and HCO (formyl), on Pt (1 1 1) with and without coadsorbed water were studied using density functional theory calculations. The structure, adsorption energy and stability with respect to dissociation were calculated. Both HCO and C–OH were stable on clean Pt (1 1 1) and with a single coadsorbed water molecule, while only the HCO configuration was stable in the presence of a whole water layer. The vibrational modes of HCO on a bridge site showed no mode around 1700 cm−1 characteristic of CO stretch making it hard to distinguish it from C–OH.