Adsorption and reaction of thiophene on α-Mo2C(0001)

Thiophene adsorbs reversibly and irreversibly on alpha-Mo2C(0001). Irreversible thiophene adsorption results in decomposition to surface C, surface S, and gaseous dihydrogen. The chemical states of the carbon and sulfur as identified by X-ray photoelectron spectroscopy are carbidic and sulfidic, respectively, implying that the surface decomposition products are bound to metal sites. The H-2 is evolved in two features during thermal desorption spectroscopy experiments, a low temperature desorption-limited peak and a high temperature reaction-limited peak. The reaction-limited peak is likely due to the decomposition of a surface hydrocarbon species that results from thiophene decomposition. Photoemission results indicate that C-S bond scission occurs by 170 K and possibly as low as 105 K. (C) 2002 Elsevier Science B.V. All rights reserved.