The role of steps in the dynamics of hydrogen dissociation on Pt(533)

The dissociative adsorption of H2 and D2 on Pt(533) (Pt{4(111)×(100)}) has been investigated using temperature programmed desorption and supersonic molecular beams. Associative desorption of D2 from (100) step sites is observed at lowest exposures in TPD (assigned β3) at 375 K. Saturation of this peak at ΘH=0.14 corresponds to the filling of half of the available four-fold sites at the (100) step edge. At higher coverages, additional desorption takes place from the (111) terraces in a broad peak below 300 K similar to that observed (assigned β1 and β2) for the Pt(111) surface. The incident kinetic energy (Ei), surface temperature (Ts), coverage (ΘD), and incident angle (Φ) dependence of the dissociative sticking probability (S) was also measured. The initial dissociative sticking probability (S0) first decreases with increasing kinetic energy over the range 0<Ei(meV)<150 (low energy component), and subsequently increases (high energy component). Comparison with D2 dissociation on Pt(111), where (S0) incre...

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