Chemisorption of H 2 O on the surface of Ti 2 O 3 : Role of d electrons and ligand geometry

摘要: The interaction of ${\mathrm{H}}_{2}$O with both nearly perfect and defect ${\mathrm{Ti}}_{2}$${\mathrm{O}}_{3}$ surfaces has been studied by ultraviolet photoemission spectroscopy. Perfect (047) surfaces, which contain fivefold O-coordinated ${\mathrm{Ti}}^{3+}$ cations, rapidly chemisorb molecular ${\mathrm{H}}_{2}$O, an accompanying transfer electrons from the Ti ${a}_{1g}$ band to molecule-surface complex. Saturation coverage adsorbed is less than one-half monolayer. extramolecular relaxation-polarization shift for molecularly 1.0 eV, O-lone-pair orbital dominant in bonding surface. There no evidence dissociative chemisorption on (047). On containing a high density defects, adsorption observed; chemisorbed species believed be O${\mathrm{H}}^{\ensuremath{-}}$ radicals. Some may also occur larger exposures. These results indicate that presence surface ions alone not sufficient catalyze dissociation contrast previous interpretations data Ti${\mathrm{O}}_{2}$ SrTi${\mathrm{O}}_{3}$. Presumably other valence states or more complicated ligand structure sites are required ${\mathrm{H}}_{2}$O.