Intrinsic defects of TiO2(110): Interaction with chemisorbedO2,H2, CO, and CO2

Abstract

The interaction of Ti${\mathrm{O}}_{2}$(110) with ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, and C${\mathrm{O}}_{2}$ was studied by means of low-energy electron diffraction, x-ray photoelectron spectroscopy, electron energy-loss spectroscopy, thermal desorption, electron paramagnetic resonance, and measurements of changes in surface conductivities, $\ensuremath{\Delta}\ensuremath{\sigma}$, and work functions, $\ensuremath{\Delta}\ensuremath{\phi}$, for $300\ensuremath{\le}T\ensuremath{\le}1000$ K with particular emphasis on surface reactions involving intrinsic surface defects $2{\mathrm{Ti}}^{3+}\ifmmode\cdot\else\textperiodcentered\fi{}V_{O}^{}{}_{}{}^{(+)}$. The defects are thermodynamically stable at high temperatures and act as donors and specific adsorption sites for ${\mathrm{H}}_{2}$ and CO. Surface and subsurface reactions involving ${\mathrm{O}}_{2}$, ${\mathrm{H}}_{2}$, CO, and C${\mathrm{O}}_{2}$ can be separated from each other by analyzing the $\ensuremath{\Delta}\ensuremath{\sigma}$ and $\ensuremath{\Delta}\ensuremath{\phi}$ effects in a charge-transfer model, which takes into account surface and bulk electronic states in the band gap attributed to the different defects formed during the interaction.