Adsorption Orientation-Induced Selectivity Control of Reactions of Benzyl Alcohol on Pd(111)

Temperature-programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) experiments were performed to determine the surface chemistry of benzyl alcohol on Pd(111) at varying initial surface coverage. At low coverage, benzyl alcohol adopts a flat lying structure where both the alcohol and phenyl ring are close to the surface. This structure decomposes through a benzaldehyde intermediate and undergoes decarbonylation to produce benzene and carbon monoxide. At high coverage, benzyl alcohol adopts an upright structure where only the alcohol function is bound to the surface and the phenyl ring extends into vacuum. The orientation of this structure is correlated with deoxygenation to produce toluene and water. These results have important implications in designing catalysts with modified surfaces and reaction conditions to have high selectivity toward a given process.