Wilson J N, Idriss H
Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand.
Langmuir. 2004 Dec 7;20(25):10956-61. doi: 10.1021/la0484422.
The reaction of NH(3) on the surface of the 011-faceted structure of the TiO(2)(001) single crystal is studied and compared to that on the O-defected surface. Temperature-programmed desorption (TPD) conducted after NH(3) adsorption at 300 K shows only molecular desorption at 340 K. Modeling of TPD signals as a function of surface coverage indicated that the activation energy, E(d), and pre-exponential factor, v(eff), decrease with increasing coverage. Near zero surface coverage, E(d) was found to be equal to 92 kJ/mol and v(eff) to be close to 10(13) /s. Both parameters decreased to approximately 52 kJ/mol and approximately 10(7) /s at saturation coverage. The decrease is due to a repulsive interaction of adsorbed NH(3) molecules on the surface. Computing of the TPD results show that saturation is obtained at 1/2 monolayer coverage (referred to Ti atoms). Both the amount and shape of NH(3) peak change on the reduced (Ar(+)-sputtered) surfaces. The desorption peak at 340 K is considerably attenuated on mildly reduced surfaces (TiO( approximately )(1.9)) and has totally disappeared on the heavily reduced surfaces (TiO(1.6)(-)(1.7)), where the main desorption peak is found at 440 K. This 440-K desorption is most likely due to NH(x) + H recombination resulting from ammonia dissociation upon adsorption on Ti atoms in low oxidation states.
研究了NH₃在TiO₂(001)单晶011面结构表面上的反应，并将其与氧缺陷表面上的反应进行了比较。在300 K吸附NH₃后进行的程序升温脱附(TPD)显示，仅在340 K有分子脱附。将TPD信号作为表面覆盖度的函数进行建模表明，活化能E(d)和指前因子v(eff)随覆盖度增加而降低。在接近零表面覆盖度时，发现E(d)等于92 kJ/mol，v(eff)接近10¹³ /s。在饱和覆盖度时，这两个参数均降至约52 kJ/mol和约10⁷ /s。这种降低是由于表面吸附的NH₃分子之间的排斥相互作用。TPD结果的计算表明，在1/2单层覆盖度(相对于Ti原子)时达到饱和。在还原(Ar⁺溅射)表面上，NH₃峰的数量和形状都会发生变化。在轻度还原的表面(TiO(约)(1.9))上，340 K处的脱附峰明显减弱，而在严重还原的表面(TiO(1.6)( - )(1.7))上则完全消失，在该表面上主要脱附峰出现在440 K。这种440 K的脱附很可能是由于NH(x)+H复合，这是由于氨在低氧化态的Ti原子上吸附时发生解离所致。
