CO adsorption on W(100) during temperature-programmed desorption: A combined density functional theory and kinetic Monte Carlo study

摘要

Using a combined density functional theory (DFT) and kinetic Monte Carlo (KMC) simulations, we study the adsorption at 800 K and subsequent desorption of CO on W(100) at higher temperatures. The resulting TPD profiles are known experimentally to exhibit three desorption peaks beta(1), beta(2), and beta(3) at 930 K, 1070 K, and 1375 K, respectively. Unlike more recent theoretical studies that propose that all three aforementioned peaks are molecularly rather than associatively desorbed, our KMC analyses are in support of the latter, since at 800 K dissociation is facile and that CO exists as dissociation fragments C and O. We show that these peaks arise from desorption from the same adsorption site but whose binding energy varies depending on local environment, that is, the presence of CO as well as dissociation fragments C and O nearby. Furthermore we show that several key parameters, such as desorption, dissociation and recombination barriers all play a key role in the TPD spectra these parameter effectively controls not only the location of the TPD peaks but the shape and width of the desorption peaks as well. Moreover, our KMC simulations reveal that varying the heating rate shifts the peaks but leaves their shape intact. (C) 2016 Elsevier B.V. All rights reserved.