Abstract
Adsorption and thermal decomposition of H 3CSH on Pt(1 1 1) is studied with temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) with synchrotron radiation. A H 3CSH molecule undergoes dehydrogenation via formation of H x CS ( x ⩽ 3) intermediates. The catalytic reactivity of Pt for dehydrogenation, which depends on interaction between the surface and the CH x moiety of H x CS, varies with coverage. At large coverage, H 3CSH decomposes through desorbing hydrogen via stepwise dehydrogenation (H 3CS → H 2CS → HCS → S + C). H 2CS is proposed to be an intermediate for dehydrogenation of H 3CS below 240 K, and subsequently undergoes disproportionation to form HCS with desorption of CH 4 at 400 K. The HCS species further decomposes to desorb hydrogen at 475 K and to form C and S adatoms; these adatoms show a mixed ( 3 × 3 ) R30° and dim c(2 × 2) LEED pattern at saturation exposure. At small coverage, surface Pt exhibits a catalytic effect on dehydrogenation of H x CS via interaction of the CH x moiety with surface Pt atoms. Dehydrogenation of H 3CSH is completed below 370 K and is proposed to form a surface C S species; this species entirely decomposes to form C and S adatoms at 570 K.
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