Different binding sites for methanol dehydrogenation and deoxygenation on stoichiometric and defective TiO2(110) surfaces

被引:95
作者
Farfan-Arribas, E [1 ]
Madix, RJ [1 ]
机构
[1] Stanford Univ, Dept Chem Engn, Stanford, CA 94305 USA
基金
美国国家科学基金会;
关键词
X-ray photoelectron spectroscopy; thermal desorption spectroscopy; electron bombardment; surface chemical reactions; titanium oxide; alcohols; low index single crystal surfaces; surface defects;
D O I
10.1016/j.susc.2003.08.025
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Methanol adsorption on stoichiometric and defective TiO2(1 1 0) surfaces was studied by means of TPRS and XPS. Anion vacancy defects were created by electron bombardment in order to minimize the structural damage inflicted to the surface. Methanol adsorbed dissociatively on the TiO2(1 1 0) surfaces at room temperature, forming methoxide and hydroxide groups. On the stoichiometric surface most methoxide groups recombined at low temperature (320 K) to form methanol, while a small fraction (similar to15%) converted to formaldehyde and methanol at high temperature (630 K). On the electron-irradiated (defective) surfaces, a significant fraction of methoxy groups (28-36%) reacted to form methane above 450 K. The activation energy for methane desorption decreased with increasing number of anion vacancy defects. Methane formation from methoxy is favored in the presence of defects because the oxygen released is returned to the surface, healing the anion vacancy defects. Two different binding sites for the methoxy species (Ti4+ cations and anion vacancy defects) are proposed to be responsible for the different reaction products. Oxygen post-dosed after methanol onto the defective surfaces results in the formation of methanol and formaldehyde at high temperature, as on the stoichiometric surface. (C) 2003 Published by Elsevier B.V.
引用
收藏
页码:241 / 260
页数:20
相关论文
共 49 条
[1]   ORIGINS AND OBJECTIVES [J].
BOND, GC ;
VEDRINE, JC .
CATALYSIS TODAY, 1994, 20 (01) :1-6
[2]   VANADIUM-OXIDE MONOLAYER CATALYSTS - PREPARATION, CHARACTERIZATION AND CATALYTIC ACTIVITY [J].
BOND, GC ;
TAHIR, SF .
APPLIED CATALYSIS, 1991, 71 (01) :1-31
[3]   Evidence for structure sensitivity in the thermally activated and photocatalytic dehydrogenation of 2-propanol on TiO2 [J].
Brinkley, D ;
Engel, T .
JOURNAL OF PHYSICAL CHEMISTRY B, 2000, 104 (42) :9836-9841
[4]   Photocatalytic dehydrogenation of 2-propanol on TiO2(110) [J].
Brinkley, D ;
Engel, T .
JOURNAL OF PHYSICAL CHEMISTRY B, 1998, 102 (39) :7596-7605
[5]   ESDIAD studies of the structure of TiO2(110) (1x1) and (1x2) surfaces and interfaces in conjunction with LEED and STM [J].
Cocks, ID ;
Guo, Q ;
Williams, EM .
SURFACE SCIENCE, 1997, 390 (1-3) :119-125
[6]  
DEO G, 1994, CRIT REV SURF CHEM, V4, P141
[7]   The surface science of titanium dioxide [J].
Diebold, U .
SURFACE SCIENCE REPORTS, 2003, 48 (5-8) :53-229
[8]   Intrinsic defects on a TiO2(110)(1x1) surface and their reaction with oxygen:: a scanning tunneling microscopy study [J].
Diebold, U ;
Lehman, J ;
Mahmoud, T ;
Kuhn, M ;
Leonardelli, G ;
Hebenstreit, W ;
Schmid, M ;
Varga, P .
SURFACE SCIENCE, 1998, 411 (1-2) :137-153
[9]   Evidence for oxygen adatoms on TiO2(110) resulting from O2 dissociation at vacancy sites [J].
Epling, WS ;
Peden, CHF ;
Henderson, MA ;
Diebold, U .
SURFACE SCIENCE, 1998, 412-13 :333-343
[10]   ELECTRONIC EXCITATIONS AT OXYGEN DEFICIENT TIO2(110) SURFACES - A STUDY BY EELS [J].
ERIKSEN, S ;
EGDELL, RG .
SURFACE SCIENCE, 1987, 180 (01) :263-278