Adsorption of Benzene on a Mo(112)−c(2 × 2)-[SiO4] Surface

BTEX adsorption on TiO2 anatase and rutile surfaces: DFT functionals

Benzene, toluene, ethylbenzene, and xylenes are volatile hydrocarbons known as BTEX, which present concerns about environmental problems. Density functional theory (DFT) functionals were used for the BTEX gas phase adsorption on TiO₂ (110) of rutile and (101) of anatase surfaces. Dispersion terms have shown the importance to treat weak interactions and were used to study these adsorptions using plane wave DFT calculations. All BTEX molecules have the same trend for the adsorption on rutile and anatase surfaces. The inclusion of dispersion terms has a significant contribution for the interaction energy. Density of states results suggest the hybridization between the d state of pentacoordinated titanium atoms (Ti_5C) and carbon p states of benzene. The adsorption energy values indicate an effective interaction between the BTEX and surfaces, mainly due to the aromatic π interaction, which is present in all adsorbates. However, for p-xylene the methyl hydrogen directs the second major influence. Graphical abstract Charge difference showing the system with the smallest interaction and the one with the largest interaction.

Ultrathin, ordered oxide films on metal surfaces

Metal oxides and oxide thin films are extensively used as active catalysts and catalytic supports, as well as in many other important technical applications. Unlike TiO(2), which is a semiconductor and can be investigated using a variety of surface science techniques, most metal oxides are insulators, which seriously restricts their use as model surfaces with modern surface science techniques. This difficulty can be circumvented by synthesizing ultrathin oxide films a few nanometers in thickness with well-defined structures, that mimic the corresponding bulk oxides yet are thin enough to be sufficiently conducting. In this review, preparations, structures, electronic and chemical properties of four representative oxides, alumina, magnesium oxide, silica, and titania, are addressed. Of these MgO is found to grow in a layer-by-layer fashion, allowing preparation of crystalline thin film structures with varying thicknesses. Crystalline TiO(2) and Ti(2)O(3) can also be synthesized, whereas SiO(2) and Al(2)O(3), although amenable to synthesis as well-defined monolayer structures, have only been grown to date as amorphous multilayers.