Adsorption, desorption, and dissociation of benzene on TiO_2(110) and Pd/TiO_2(110): Experimental characterization and first-principles calculations

摘要

Adsorption and reaction of benzene molecules on clean TiO_2(110) and on TiO_2(110) with deposited Pd nanoparticles are investigated using a combination of scanning tunneling microscopy (STM), temperature-programmed desorption, and first-principles calculations. Above ～50 K, the one-dimensional motion of benzene between bridging oxygen rows is shown to be too fast for STM imaging. At 40 K benzene molecules form chains on top of titanium rows, with calculations indicating every other benzene is rotated 30°. Both experimental and theoretical studies find no dissociative reactivity of benzene on the clean TiO_2(110) surface, due to little hybridization between TiO_2 and benzene electronic states. After deposition of Pd nanoparticles, molecular benzene is observed with STM both on the substrate and adjacent to metallic particles. Upon heating to 800 K, benzene fully breaks down into its atomic constituents in a multistep decomposition process.