Structure and decomposition pathways of vinyl acetate on Pd(1 1 1)

The surface chemistry of vinyl acetate on clean Pd(1 1 1) is explored experimentally in ultrahigh vacuum using reflection absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) combined with density functional theory (DFT) calculations. The relative intensities of the vibrational features of a vinyl acetate overlayer are in good agreement with the structure calculated by DFT. Furthermore, the calculated heat of adsorption of vinyl acetate (63.4 kJ/mol) is in excellent agreement with the measured desorption activation energy (65 ± 7 kJ/mol). The thermal decomposition pathways of adsorbed vinyl acetate are relatively complex involving initial cleavage of the O-acetyl or O-vinyl bonds to form either vinyloxy and acetyl, or acetate and vinyl species, respectively on the surface. The acetate thermally decomposes to desorb methane at ∼260 K, while the acetyl and vinyloxy species isomerize and react to form acetaldehyde or methane. Ethylidyne is formed, and adsorbed CO either desorbs or oxidizes to CO2 at ∼450 K.