Department of Civil and Architectural Engineering, City University of Hong Kong, Kowloon, Hong Kong.
Phys Chem Chem Phys. 2013 Mar 21;15(11):3866-80. doi: 10.1039/c3cp43549k.
The adsorption of formaldehyde (HCHO) on both clean and hydroxylated TiO(2)-B(100) surfaces with terminal and bridging hydroxyl groups is systematically investigated by using first principles density functional theory calculations. The discussion is mainly focused on the two different chemical adsorption configurations of HCHO in periodicity (2 × 2), in which the C atom of HCHO is bonded with two coordinated O atoms on a step (Structure I) or on a terrace (Structure II). The study indicates that bridging hydroxyl groups on most of the adsorption sites near to HCHO will weaken the adsorption of HCHO, while terminal hydroxyl groups on most of adsorption sites will facilitate it. The investigation of the effects of hydroxyl groups and H(2)O molecule on HCHO in different periodicities shows that the terminal hydroxyl groups or H(2)O molecules have significantly facilitated the adsorption of H(2)O at larger periodicities, while bridging hydroxyl groups do not have this trend. The analysis of the adsorption mechanisms of HCHO molecules on both clean and hydroxylated surfaces indicate that the terminal hydroxyl groups can extract electrons from the surface and facilitate adsorption of HCHO due to the adsorption energy being higher than that on the clean surface, while the bridging hydroxyl groups donate electrons to the surface and weaken the adsorption. In all chemical adsorption configurations, HCHO acts as an electron acceptor. Interestingly, though the adsorptions are weaker, HCHO in Structure II gains more electrons on both the clean and hydroxylated surfaces than in Structure I. This unique mechanism provides a novel angle to understand the interaction of HCHO with the hydroxylated TiO(2) surface.
采用第一性原理密度泛函理论计算系统地研究了甲醛（HCHO）在具有末端和桥接羟基的清洁和羟基化 TiO(2)-B(100)表面上的吸附。讨论主要集中在 HCHO 在周期性（2×2）中的两种不同化学吸附构型上，其中 HCHO 的 C 原子与台阶上的两个配位 O 原子（结构 I）或平台上的两个配位 O 原子（结构 II）键合。研究表明，大多数靠近 HCHO 的吸附位上的桥接羟基基团会削弱 HCHO 的吸附，而大多数吸附位上的末端羟基基团会促进 HCHO 的吸附。对不同周期性中羟基和 H2O 分子对 HCHO 的影响的研究表明，末端羟基基团或 H2O 分子在较大周期性下显著促进了 H2O 的吸附，而桥接羟基基团则没有这种趋势。对 HCHO 分子在清洁和羟基化表面上的吸附机制的分析表明，末端羟基基团可以从表面提取电子，并由于吸附能高于清洁表面而促进 HCHO 的吸附，而桥接羟基基团则向表面提供电子并削弱吸附。在所有化学吸附构型中，HCHO 充当电子受体。有趣的是，尽管吸附较弱，但在清洁和羟基化表面上，结构 II 中的 HCHO 比结构 I 获得更多的电子。这种独特的机制为理解 HCHO 与羟基化 TiO(2)表面的相互作用提供了一个新的角度。
