| The adsorption and reaction of various molecules have been studied experimentally on oxidized Pd(111) surface under ultra-high vacuum conditions. Hydrogen, methanol, methane, ethane, propane, n-butane and n-pentane have been studied extensively as well as isotopes of hydrogen, propane and n-butane on the palladium oxide surfaces. Using UHV measurement techniques, the kinetics and physics of the interactions between these molecules and the PdO surface has been investigated.;When the hydrogen molecule is adsorbed on PdO(101) on cus-Pd site at low temperatures, it dissociates. During the temperature programmed desorption (TPD) experiment, it desorbs molecularly and recombinatively, additionally, it reacts with the surface and produces water. However, when deuterium is adsorbed under the same experimental conditions, the reaction products decrease significantly due to the effect of tunneling in hydrogen reactivity.;Methanol molecule is also adsorbed on the cus-Pd site as methoxy and reacts during TPD producing hydrogen, formaldehyde, methyl formate, water and carbon dioxide depending on the coverage. As the coverage increases, the coupling reaction takes place more dominantly.;Methane, ethane, propane, n-butane and n-pentane (alkanes studied) are also adsorbed on to the cus-Pd site creating alkane sigma complexes. This alkane sigma complex results in a more strongly bound adsorbed species and it is the precursor for the reaction of the alkanes longer than ethane. Although methane and ethane both form the sigma complex, the kinetics favor desorption over reaction. Since the alkanes that react have both primary and secondary C-H bonds, selectivity analysis towards these bonds during the reaction on PdO(101) surface has also been investigated. The selectivity of C-H bond cleavage favors the primary bond in the case of propane activation on PdO(101) surface. n-Butane activation does not have preference to primary or secondary C-H bonds at high coverages, however at the limit of zero coverage, the reaction occur through the primary bond cleavage. |
