Partial Hydrogenation of 1, 3-Butadiene Adsorbed on Pd (110) : The Activation of Reactant by the Template Effect

Partial hydrogenation of 1, 3-butadiene (C4H6) to butene (C4H8) on hydrogen precovered Pd (110) has been investigated using temperature-programmed desorption (TPD), scanning tunneling microscopy (STM) and high resolution electron energy loss spectroscopy (HREELS). Below room temperature, C4H6 was molecularly chemisorbed on a hydrogen precovered Pd (110) surface, and was in π-bonded chemisorption states. The hydrogenation of C4H6 did not occur in the sparse domains less than 0.25 ML (c (4×2)). With increasing the C4H6 coverage, C4H6formed dense domains and the π-bond was weakened. Only the weakly π-bonded C4H6was hydrogenated to C4H8 at about 200 K. We propose that c (4×2) structure of 1, 3-butadiene acts as the template for the activation of hydrogenation.