Band-Gap States of TiO2(110): Major Contribution from Surface Defects

Many physical and chemical processes on TiO2 surface are linked to the excess electrons originated from band gap states. However, the sources (surface and/or subsurface defects) of these states are controversial. We present quantitative ultraviolet photoelectron spectroscopy (UPS) measurements on the band gap states of TiO2(110) with constant subsurface defect density and varied surface bridging hydroxyls (ObrH) prepared through photocatalyzed splitting of methanol, in combination with density functional theory (DFT) calculations. Our results clearly suggest both surface and subsurface defects contribute to the band gap states, whereas the contribution of subsurface defects corresponds to that of only 1.9% monolayer ObrH at the current bulk reduction level. As the surface defect concentration is usually much larger than 1.9% monolayer in real studies and applications, our work demonstrates the importance of surface defects in changing the electronic structure of TiO2, which dictates the surface chemistry.

[1]  Zhibo Ma,et al.  Stepwise photocatalytic dissociation of methanol and water on TiO2(110). , 2012, Journal of the American Chemical Society.

[2]  Zhibo Ma,et al.  Surface photochemistry probed by two-photon photoemission spectroscopy , 2012 .

[3]  K. Mitsuhara,et al.  The source of the Ti 3d defect state in the band gap of rutile titania (110) surfaces. , 2012, The Journal of chemical physics.

[4]  A. Verdini,et al.  Intrinsic nature of the excess electron distribution at the TiO2(110) surface. , 2012, Physical review letters.

[5]  B. Hammer,et al.  Ethanol Diffusion on Rutile TiO2(110) Mediated by H Adatoms. , 2012, The journal of physical chemistry letters.

[6]  Zhibo Ma,et al.  Effect of defects on photocatalytic dissociation of methanol on TiO2(110) , 2011 .

[7]  E. Kaxiras,et al.  The role of surface and subsurface point defects for chemical model studies on TiO2: a first-principles theoretical study of formaldehyde bonding on rutile TiO2(110). , 2011, Chemistry.

[8]  Jinlong Yang,et al.  Site-specific photocatalytic splitting of methanol on TiO2(110) , 2010 .

[9]  G. Kimmel,et al.  Off-normal CO2 desorption from the photooxidation of CO on reduced TiO2(110) , 2010 .

[10]  Zhibo Ma,et al.  A Surface Femtosecond Two-Photon Photoemission Spectrometer for Excited Electron Dynamics and Time-Dependent Photochemical Kinetics , 2010 .

[11]  G. Thornton,et al.  Yim, Pang, and Thornton Reply: , 2010 .

[12]  G. Thornton,et al.  Comment on "Oxygen Vacancy Origin of the Surface Band-Gap State of TiO2(110)" Reply , 2010 .

[13]  B. Hammer,et al.  Comment on "Oxygen vacancy origin of the surface band-gap state of TiO2(110)". , 2010, Physical review letters.

[14]  Xue-qing Gong,et al.  Hydrogen Bonding Controls the Dynamics of Catechol Adsorbed on a TiO2(110) Surface , 2010, Science.

[15]  N. A. Deskins,et al.  Defining the Role of Excess Electrons in the Surface Chemistry of TiO2 , 2010 .

[16]  G. Thornton,et al.  Oxygen vacancy origin of the surface band-gap state of TiO2(110). , 2010, Physical review letters.

[17]  Z. Dohnálek,et al.  Chemical Reactivity of Reduced TiO2(110): The Dominant Role of Surface Defects in Oxygen Chemisorption , 2009 .

[18]  B. Hammer,et al.  The Role of Interstitial Sites in the Ti3d Defect State in the Band Gap of Titania , 2008, Science.

[19]  C. Calzado,et al.  Effect of on-site Coulomb repulsion term U on the band-gap states of the reduced rutile (110) TiO2 surface , 2008 .

[20]  G. Watson,et al.  A DFT+U description of oxygen vacancies at the TiO2 rutile (110) surface , 2007 .

[21]  D. Matthey,et al.  Enhanced Bonding of Gold Nanoparticles on Oxidized TiO2(110) , 2007, Science.

[22]  Annabella Selloni,et al.  Electronic structure of defect states in hydroxylated and reduced rutile TiO2(110) surfaces. , 2006, Physical review letters.

[23]  B. D. Kay,et al.  Imaging water dissociation on TiO2(110): Evidence for inequivalent geminate OH groups. , 2006, The journal of physical chemistry. B.

[24]  P Hu,et al.  Identifying an O2 supply pathway in CO oxidation on Au/TiO2(110): a density functional theory study on the intrinsic role of water. , 2006, Journal of the American Chemical Society.

[25]  B. D. Kay,et al.  Imaging adsorbate O-H bond cleavage: methanol on TiO2(110). , 2006, Journal of the American Chemical Society.

[26]  Hiroshi Onishi,et al.  Direct visualization of defect-mediated dissociation of water on TiO2(110) , 2006 .

[27]  B. Hammer,et al.  Oxygen vacancies on TiO2(110) and their interaction with H2O and O2: A combined high-resolution STM and DFT study , 2005 .

[28]  Bin Li,et al.  Two-photon photoemission spectroscopy of TiO2(110) surfaces modified by defects and O2 or H2O adsorbates , 2004 .

[29]  C. Peden,et al.  Insights into Photoexcited Electron Scavenging Processes on TiO2 Obtained from Studies of the Reaction of O2 with OH Groups Adsorbed at Electronic Defects on TiO2 (110) , 2003 .

[30]  Ulrike Diebold,et al.  The surface science of titanium dioxide , 2003 .

[31]  Michael A. Henderson,et al.  The Interaction of Water with Solid Surfaces: Fundamental Aspects Revisited , 2002 .

[32]  J. Nørskov,et al.  Oxygen vacancies as active sites for water dissociation on rutile TiO(2)(110). , 2001, Physical review letters.

[33]  G. Thornton,et al.  Imaging Water Dissociation on TiO(2)(110). , 2001, Physical review letters.

[34]  Michael R. Hoffmann,et al.  Infrared Spectra of Photoinduced Species on Hydroxylated Titania Surfaces , 2000 .

[35]  C. Humphreys,et al.  Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study , 1998 .

[36]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[37]  Kresse,et al.  Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set. , 1996, Physical review. B, Condensed matter.

[38]  S. Martin,et al.  Environmental Applications of Semiconductor Photocatalysis , 1995 .

[39]  Andrew Mills,et al.  WATER-PURIFICATION BY SEMICONDUCTOR PHOTOCATALYSIS , 1993 .

[40]  Richard L. Kurtz,et al.  Synchrotron radiation studies of H2O adsorption on TiO2(110) , 1989 .

[41]  Hiroshi Sano,et al.  Novel Gold Catalysts for the Oxidation of Carbon Monoxide at a Temperature far Below 0 °C , 1987 .

[42]  G. Dresselhaus,et al.  Observation of two-dimensional phases associated with defect states on the surface of TiO/sub 2/. [Ar ion bombardment] , 1976 .

[43]  S. Ito,et al.  HELIX-COIL TRANSITION OF POLY-α,L-GLUTAMIC ACID IN AQUEOUS SOLUTION STUDIED BY THE DISSOCIATION FIELD EFFECT RELAXATION METHOD , 1973 .