Diebold, Ulrike

Surface Science Reports (2003), 48(5-8), 53-229 CODEN: SSREDI; ISSN: 0167-5729. English.

A review. TiO2 is the most investigated single-crystalline system in the surface science of metal oxides, and the literature on rutile (1 1 0), (1 0 0), (0 0 1), and anatase surfaces is discussed. This paper starts with a summary of the wide variety of tech. fields where TiO2 is of importance. The bulk structure and bulk defects (as far as relevant to the surface properties) are briefly reviewed. Rules to predict stable oxide surfaces are exemplified on rutile (1 1 0). The surface structure of rutile (1 1 0) is discussed in some detail. Theor. predicted and exptl. determined relaxations of surface geometries are compared, and defects (step edge orientations, point and line defects, impurities, surface manifestations of crystallog. shear planes-CSPs) are discussed, as well as the image contrast in scanning tunneling microscopy (STM). The controversy about the correct model for the (1.times.2) reconstruction appears to be settled. Different surface preparation methods, such as reoxidn. of reduced crystals, can cause a drastic effect on surface geometries and morphol., and recommendations for preparing different TiO2(1 1 0) surfaces are given. The structure of the TiO2(1 0 0)-(1.times.1) surface is discussed and the proposed models for the (1.times.3) reconstruction are critically reviewed. Very recent results on anatase (1 0 0) and (1 0 1) surfaces are included. The electronic structure of stoichiometric TiO2 surfaces is now well understood. Surface defects can be detected with a variety of surface spectroscopies. The vibrational structure is dominated by strong Fuchs-Kliewer phonons, and high-resolution electron energy loss spectra often need to be deconvoluted to render useful information about adsorbed mols. The growth of metals (Li, Na, K, Cs, Ca, Al, Ti, V, Nb, Cr, Mo, Mn, Fe, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au) as well as some metal oxides on TiO2 is reviewed. The tendency to wet' the overlayer, the growth morphol., the epitaxial relationship, and the strength of the interfacial oxidation/reduction reaction all follow clear trends across the periodic table, with the reactivity of the overlayer metal towards O being the most decisive factor. Alkali atoms form ordered superstructures at low coverages. Recent progress in understanding the surface structure of metals in the strong-metal support interaction' (SMSI) state is summarized.Literature is reviewed on the adsorption and reaction of a wide variety of inorg. mols. (H2, O2, H2O, CO, CO2, N2, NH3, NOx, sulfur- and halogen-containing mols., rare gases) as well as organic mols. (carboxylic acids, alcs., aldehydes and ketones, alkynes, pyridine and its derivates, silanes, Me halides). The application of TiO2-based systems in photo-active devices is discussed, and the results on UHV-based photocatalytic studies are summarized. The review ends with a brief conclusion and outlook of TiO2-based surface science for the future.