Time resolved measurements of methanol decomposition on Ni(100) utilizing laser induced desorption

A new method utilizing laser induced desorption (LID) is used to study the decomposition of methanol on Ni(100) in real time. The dependence of the rate of decompositition on surface coverage and on surface temperature is measured. The decomposition rate decreases during reaction in a manner characteristic of a self-poisoned reaction. The rate data are fit to a model in which the energy barrier to reaction increases in proportion to the coverage of the CH₃O product. The energy barrier obtained is 9 kcal mol^?1 plus 4 kcal mol^?1 monolayer^?1 of CH₃O. The frequency factor of 2 × 10⁹ s^?1 suggests there is significant entropy barrier to decomposition. Substitution of deuterium for the alcoholic hydrogen alters de decomposition rate appreciably and identifies the breaking of the OH bond as the rate determining step.