Influence of spilt-over hydrogen on the electrical properties of H-ZSM-5

In this work the effect of H-2 on the electrical properties of H-ZSM-5 and Pt/H-ZSM-5 has been studied applying impedance spectroscopy in order to cla rify the nature of migrating H* species (charged or uncharged, atomic or mo lecular) in the spillover process. The observed drop of the resistive part of a charge carrier relaxation process is attributed to the increase of mob ile charges in the zeolite. This can be explained in terms of the dissociat ion of hydrogen on the Pt nanoparticles, the subsequent diffusion onto the zeolitic support and the formation of H+ as migrating species. (C) 2000 Els evier Science B.V. ALI rights reserved.