ADSORPTION AND OXIDATION OF CARBON MONOXIDE ON PLATINIZED PLATINUM ELECTRODES

Carbon monoxide is adsorbed at open circuit on platinized platinum as two types that are oxidized in different potential regions in acid and alkaline electrolytes. The different mechanisms of the anodic oxidation of the two types of COad are discussed. The saturation coverage of H atoms decreases in a linear fashion with the COad coverage. The isotherms of hydrogen adsorption degenerate to Temkin-type isotherms with increasing coverage of COad. The COad coverage is equal to 1 between 0.1 and 0.4 V under potentiostatic or galvanostatic conditions in acid solutions stirred with carbon monoxide. The beginning of the rapid decrease of COad with potential depends upon the experimental conditions. The oxidation of dissolved carbon monoxide under steady-state conditions appears to involve the one type of COad as intermediate between 0.2 and 0.4 V and the other type above 0.4 V. Adsorption of the one type is the rate-determining step between 0.2 and 0.4 V. Diffusion of CO and adsorption of the other type are rate determining above 0.4 V.