ACTIVATED ADSORPTION OF METHANE ON CLEAN AND OXYGEN-MODIFIED PT(111) AND PD(110)

Activated adsorption of CH4 on clean and oxygen modified Pt{111} and P d{110} has been studied using molecular beam surface scattering. The a bsolute dissociation probability of CH4 was measured as a function of the incident normal energy (E) and the surface temperature (T-g). The results from clean Pt{111} and Pd{110} are consistent with a direct di ssociation mechanism. The dissociative chemisorption dynamics of CH4 i s addressed by using quantum mechanical and statistical models. The in fluence of adsorbed oxygen on the dissociative adsorption of CH4 on bo th Pt{111} and Pd{110} shows that the dissociation probability decreas es linearly with increasing oxygen coverage.