Influence of hydroxyl groups on the adsorption of HCHO on TiO2-B(100) surface by first-principles study

Abstract

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.

Enhanced Formaldehyde Oxidation Performance of the Mesoporous TiO2(B)-Supported Pt Catalyst: The Role of Hydroxyls

“…Moreover, the hydroxyls on Pt/TiO 2 (B) can also contribute to the transport of CO species due to the weakened interaction between CO and the hydroxylated surface. 71 , 72 …”

Role of acid sites and surface hydroxyl groups in isophthalonitrile hydrogenation catalyzed by supported Ni–Co catalysts

“…It has been well known that the surface hydroxyl groups, which widely existed on oxide supports, played an important role in adsorption and catalytic reaction. [25][26][27][28][29] To understand the possible effect of the surface hydroxyl groups, additional studies were carried out. According to the literature, 44 the concentration of hydroxyl groups on the SiO 2 surface could be modied by treatment at different temperatures without signicant change of other surface properties.…”

“…[25][26][27][28][29] To understand the possible effect of the surface hydroxyl groups, additional studies were carried out. [25][26][27][28][29] To understand the possible effect of the surface hydroxyl groups, additional studies were carried out.…”

“…The bifunctional mechanism 17 reveals that in a nitrile hydrogenation system, the hydrogenation reactions are catalyzed by metal sites while condensation reactions are catalyzed by acid sites. 28,29 However, the acid-basic property of the surface hydroxyl groups highly depends on the environment. The surface acidity favors the conversion of nitrile but decreases the selectivity to primary amines, and the surface basicity shows the opposite effects.…”

“…Actually, oxide surfaces are usually covered by hydroxyl groups, which are potential proton donors or acceptors, [25][26][27] and play an important role in the adsorption property and catalytic performance. 28,29 However, the acid-basic property of the surface hydroxyl groups highly depends on the environment. 30 Unless activated by agents, 31 the surface hydroxyl groups on SiO 2 and g-Al 2 O 3 are very stable and do not show Brønsted acidity and basicity by providing H + or OH À .…”