Casarin Maurizio, Ferrigato Francesca, Maccato Chiara, Vittadini Andrea
Dipartimento di Scienze Chimiche, Università di Padova, and Istituto di Scienze e Tecnologie Molecolari, C.N.R. di Padova, Padova, Italy.
J Phys Chem B. 2005 Jun 30;109(25):12596-602. doi: 10.1021/jp050314e.
Density functional molecular cluster calculations have been used to investigate the interaction of SO(2) with defect-free TiO(2)(110) and Ti(2)O(3)(102) surfaces. Adsorbate geometries and chemisorption enthalpies have been computed and discussed. Several local minima have been found for TiO(2)(110), but only one seems to be relevant for the catalytic conversion of SO(2) to S. In agreement with experiment, the bonding of SO(2) to Ti(2)O(3)(102) is much stronger than that on TiO(2)(110). Moreover, our results are consistent with the surface oxidation and the formation of strong Ti-O and Ti-S bonds. On both substrates, the bonding is characterized by a two-way electron flow involving a donation from the SO(2) HOMO into virtual orbitals of surface Lewis acid sites (), assisted by a back-donation from surface states into the SO(2) LUMO. However, the localization of surface states and the strength of back-donation are very different on the two surfaces. On TiO(2)(110), back-donation is weaker, and it involves unsaturated bridging O atoms, while on Ti(2)O(3)(102), it implies the -based valence band maximum and significantly weakens the S-O bond.
密度泛函分子簇计算已被用于研究SO(2)与无缺陷的TiO(2)(110)和Ti(2)O(3)(102)表面之间的相互作用。已计算并讨论了吸附质的几何结构和化学吸附焓。在TiO(2)(110)上发现了几个局部极小值，但似乎只有一个与SO(2)催化转化为S有关。与实验一致，SO(2)与Ti(2)O(3)(102)的键合比在TiO(2)(110)上强得多。此外，我们的结果与表面氧化以及强Ti-O和Ti-S键的形成一致。在两种基底上，键合的特征是双向电子流动，包括从SO(2)的最高占据分子轨道（HOMO）向表面路易斯酸位点的虚轨道的电子给予，并伴随着从表面态向SO(2)的最低未占分子轨道（LUMO）的反馈。然而，两种表面上表面态的定位和反馈的强度非常不同。在TiO(2)(110)上，反馈较弱，涉及不饱和桥连O原子，而在Ti(2)O(3)(102)上，它涉及基于的价带最大值并显著削弱S-O键。
