Desulfurization of benzenethiol on CoMo(110) phases

Abstract

The desulfurization of benzenethiol on Co-covered Mo(110) (θCo = 0.25–1.3 ML) produces benzene, H2 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, ∼ 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.