Adsorption, desorption, and dissociation of benzene onTiO2(110)andPd∕TiO2(110): Experimental characterization and first-principles calculations

Abstract

Adsorption and reaction of benzene molecules on clean ${\mathrm{TiO}}_{2}(110)$ and on ${\mathrm{TiO}}_{2}(110)$ with deposited Pd nanoparticles are investigated using a combination of scanning tunneling microscopy (STM), temperature-programmed desorption, and first-principles calculations. Above $\ensuremath{\sim}50\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, the one-dimensional motion of benzene between bridging oxygen rows is shown to be too fast for STM imaging. At $40\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ benzene molecules form chains on top of titanium rows, with calculations indicating every other benzene is rotated $30\ifmmode^\circ\else\textdegree\fi{}$. Both experimental and theoretical studies find no dissociative reactivity of benzene on the clean ${\mathrm{TiO}}_{2}(110)$ surface, due to little hybridization between ${\mathrm{TiO}}_{2}$ 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 $800\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, benzene fully breaks down into its atomic constituents in a multistep decomposition process.