Hydrogen dissociation on Pt{100}: Nonlinear power law in hydrogen induced restructuring

Abstract

Using molecular beam sticking probability measurements at desorption temperatures we have made a dynamical measurement of the (1×1) island growth rate and the simultaneous D coverage on the rotated quasihexagonal reconstructed phase (hex-R) during the D-induced hex-R→(1×1) phase transformation on Pt{100}. The island growth rate (rg) is described by a strongly nonlinear power law with respect to the local D coverage on the hex-R phase (θ Dhex) at surface temperatures in the range 150–250 K. The apparent rate is given by rg∝(θ Dhex)4.0±0.5. These kinetics are shown to be consistent with the dependence of the temperature programmed desorption spectra on the surface temperature and rate of D2 impingement during adsorption at ∼245 K. In particular the intensity of the α3 desorption peak is markedly sensitive to these parameters, consistent with its assignment to associative desorption from the (1×1) phase.