Coadsorption of cyclohexanes and CO on Ni(755): promoting effect of CO and increase of decomposition fraction by methyl substituent

Coadsorption of methyl-substituted cyclohexanes and CO has been investigated by temperature-programmed desorption (TPD). Coadsorbed CO promotes decomposition of cyclohexanes. Decomposition fraction (ratio of decomposed molecules to adsorbed ones) of cyclohexanes was determined with changing coverages of CO and cyclohexanes. Decomposition fraction increases sharply when a tertiary CH bond is introduced into a cyclohexane ring by methyl substitution. This is consistent with the fact that dissociation energy of a tertiary CH bond is smaller than those of primary and secondary CH bonds.