DEUTERIUM AND DEUTERIUM SULFIDE ADSORPTION ON MOS2(0001)

The adsorption of deuterium and deuterium sulfide was studied on the M oS2(0001) basal surface using temperature programmed desorption (TPD) and four-point surface conductivity measurements. Deuterium did not di ssociatively adsorb to tile basal MoS2(0001) surface upon exposure, an d thus was dissociated with a platinum wire during dosing. D-2 and D2S were both observed as products following adsorption of dissociated D on the MoS2(0001) surface. The presence of D2S as a desorption product demonstrates that lattice sulfur was removed to form anion vacancies on the MoS2(0001) surface. D2S TPD experiments on an MoS2 surface with anion vacancies showed both D2S and D-2 as desorption products. The p resence of D-2 in the D2S TPD shows that some deuterium sulfide dissoc iatively adsorbs. Further, the amount of D-2 desorbing was found to de crease as a function of exposure. suggesting that D2S was leaving sulf ur behind to ''heal'' anion vacancies. The desorption traces resulting from both deuterium and deuterium sulfide exposures were very broad, and are thought to occur via the recombination of two different desorp tion states. The possible implications of these experiments to HDS cat alytic systems are also discussed. (C) 1998 Elsevier Science B.V.