STABILIZATION EFFECTS IN THE DECOMPOSITION OF FORMATE ON RU(001)

Both the transient and the isothermal decomposition of formate on Ru(001) have been studied using thermal desorption mass spectrometry. The formate decomposition rate, measured by monitoring the production rate of CO2, exhibits ''stabilization'' in both thermal desorption and isothermal desorption measurements. At a constant heating rate, the thermal desorption spectrum of CO2 shifts up in peak temperature and becomes progressively more narrow with increasing initial coverage of surface formate. The isothermal decomposition rate reveals a convex parabolic curve with time prior to passing through a maximum. A simple mean-field kinetic model is used to describe both the transient thermal desorption and the isothermal desorption spectra. The stabilization kinetics are attributed both to attractive interactions between formates as well as between a formate and its chemisorbed decomposition product, CO. Calculations using the mean-field model quantitatively reproduce the experimentally observed kinetic behavior.