Desulfurization of benzenethiol on Co-Mo(110) phases

The desulfurization of benzenethiol on Co-covered Mo(110) (theta(Co) = 0.25-1.3 ML) produces benzene, H-2 and adsorbed carbon and sulfur. Benzene is formed via adsorbed phenyl thiolate, which is identified by X-ray photoelectron and electron energy loss spectroscopies. Benzene production is attributed to reaction on Co, since it is evolved at a temperature well below that required for sulfur-induced aggregation of Co. The reaction products and mechanisms are qualitatively similar on Co-covered Mo(110) and a range of other transition metal surfaces. The selectivity for benzene production on the 1.3 ML Co overlayer, similar to 65%, is higher than on many surfaces. Furthermore. benzene evolution occurs at a very low temperature, 125 K, on the 1.3 ML Co film. Notably, we did not observe any new products or a dramatic change in reaction temperature or selectivity as a result of Co-Mo interactions or of structural changes in the Co layer. Comparison of the benzene evolution temperature for benzenethiol reaction with that of methane from methanethiol reaction on the close-packed Co overlays indicates that homolytic C-S bond scissions do not control the hydrogenolysis rate, in contrast to reaction on Mo(110) but similar to Ni(111). This difference may be due to hydrogen-induced structural transformations of the Co layer or to hydrogen-assisted C-S bond breaking. (C) 1998 Elsevier Science B.V.