DECOMPOSITION OF METHANETHIOL ON NI(111) - A TPD AND SSIMS STUDY

The adsorption and decomposition of methanethiol on Ni(111) is studied using temperature-programmed desorption (TPD), static secondary ion mass spectroscopy (SSIMS) and Auger electron spectroscopy (AES). CH3SH adsorption is mostly molecular at 100 K. Thermal decomposition occurs below 150 K by S-H bond cleavage to form H(a) and CH3S(a). For low thiol coverages, complete decomposition to desorbing hydrogen and residual sulfur and carbon is observed. At higher coverages, desorption of CH4, C2H6 and H2 is observed in TPD. 0.25 ML of preadsorbed sulfur inhibits thiol desulfurization and dehydrogenation. A simple mechanism that accounts for the observed results is discussed.