KINETIC STUDIES ON THE CO OXIDATION OVER PLATINUM BY MEANS OF C-13 TRACER

The kinetics of the CO oxidation over polycrystalline platinum was investigated with a transient isotope tracer method. Transient CO2 production was generated by a dosage of various gas mixtures of 12CO and O2 to the surface precovered by various ratios of 13CO to 12CO. The initial ratio of 13CO2 to 12CO2 in the CO2 produced transiently equaled that of 13CO to 12CO in the CO preadsorbed for all the conditions studied; CO must be chemisorbed before being oxidized, i.e. a Langmuir-Hinshelwood mechanism is operative. The ratio of 13CO2 to 12CO2 in CO2 decreased more rapid than the average ratio of 13CO(a) to 12CO(a) in CO(a). This apparent inhomogeneity in the reactivity of CO(a) was explained in terms of the boundary reaction model, in which the reaction took place predominantly outside or near the boundary of the CO(a) island. © 1979.