Adsorption, desorption, and dissociation of benzene on TiO2 (110) and Pd TiO2 (110): Experimental characterization and first-principles calculations

Adsorption and reaction of benzene molecules on clean TiO2 (110) and on TiO2 (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 TiO2 (110) surface, due to little hybridization between TiO2 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.