Multilayer growth and chemisorbate reactivity of methanol on Pd{110}

The development of a methanol multilayer on Pd{110} at 124 K has been examined with reflection–absorption infrared spectroscopy (RAIRS). The spectra indicate that a crystalline multilayer grows in which hydrogen-bonded chains of molecules are parallel to the substrate. A “sandwich” phase is identified and consists of several physisorbed layers in between the chemisorbed layer and the crystalline phase. Methanol desorption and decomposition on heating have been followed with simultaneous temperature-programmed RAIRS and TPD measurements. Desorption of chemisorbed methanol is observed at 214 K, whereas the decomposition reaction yielding adsorbed CO and H proceeds at ∼295 K on heating at 2 K s−1. Spectral bands observed on adsorption at 180 K to low exposure, which precede the appearance of the CO signal, are tentatively attributed to chemisorbed methanol. No conclusive evidence for a methoxy intermediate in the decomposition reaction is found.