A vibrational spectroscopic study of the adsorption and dehydrogenation of cyclic C-6 hydrocarbons on the (1x1) and (5x20) surfaces of Pt{100}

The dehydrogenation of cyclohexane and cyclohexene has been investigated on the (1 x 1) and (5 x 20) surface modifications of Pt{100}. In each case dehydrogenation to adsorbed benzene occurs, although the reaction has a very low probability for cyclohexane adsorbed on the (5 x 20) surface at low temperature, despite the presence of softened C-H stretching modes in the vibrational spectra. The surface electronic structure appears to influence the reaction pathway of the dehydrogenation process. On the (5 x 20) surface a conformational change of the adsorbate appears to occur, while on the (1 x 1) surface a stable intermediate can be isolated. Measurements made on isomers of cyclohexadiene support the suggestion that this intermediate has the formula C6H9. (C) 1997 Elsevier Science B.V.