Adsorption and Decomposition of Phenol on Pd(110) Surface

Adsorption and decomposition of phenol on Pd(110) surface have been investigated with XPS, UPS, AES, LEED and TDS. Both thermal desorption and photoelectron spetroscopies suggest the following decomposition process of phenol on Pd(110):At 300K, phenol undergoes a O-H bond cleavage to form the phenoxy. Heating the phenol saturated surface causes the C-C bond breaking of phenyl ring to yield the surface hydrocarbon fragments and CO which desorbs into gas phase at 400K. With decreasing of phenol coverage, the CO evolves at higher temperature due to less site-blocking of phenoxy species on the surface. The C-H bond cleavage occurs at higher temperature of 450K.
During the composition of phenol on Pd(110), the C-O bond never breaks, and only surface carbon remains on surface at high temperature as observed with XPS. The UPS spectra demonstrate that the phenol adsorption on Pd(110) induces the stabilization of the π-bands and the O lone pair electrons, suggesting the coordination to metal surface via the aromatic rings and the O atoms.