Abstract
The interactions of nitrogen dioxide molecule with TiO2-supported Au nanoparticles were investigated using density functional theory. Surface Au atoms on the TiO2-supported Au overlayer were found to be the most favorable binding sites, thus making the adsorption process very strong. Both oxygen and nitrogen atoms of the NO2 molecule can bind to the Au surface by forming strong chemical bonds. The adsorption of NO2 molecule on the considered structures gives rise to significant changes in the bond lengths, bond angles, and adsorption energies of the complex systems. The results indicate that NO2 adsorption on the TiO2-supported Au nanoparticle by its oxygen atoms is energetically more favorable than the NO2 adsorption by its nitrogen atom, indicating the strong binding of NO2 to the TiO2-supported Au through its oxygen atoms. Thus, the bridge configuration of TiO2/Au + NO2 is found to be the most stable configuration. Both oxygen and nitrogen atoms of NO2 move favorably towards the Au surface, as confirmed by significant overlaps in the PDOSs of the atoms that forming chemical bonds. This study not only suggests a theoretical basis for gas-sensing properties of the TiO2-supported Au nanoparticles, but also offers a rational approach to develop nanostructure-based chemical sensors with improved performance.
Highlights
TiO2 is one of the most broadly studied transition metal semiconductors with outstanding properties, such as nontoxicity, high catalytic efficiency, and extensive bandgap [1]
Three possible orientations of the NO2 molecule towards the TiO2-supported Au overlayers were considered, in which the NO2 molecule can bind to the surface of Au atoms either by its nitrogen or by oxygen atoms
Over the TiO2-supported Au nanoparticle, the NO2 molecule preferentially interacts with the Au nanoparticle
Summary
TiO2 is one of the most broadly studied transition metal semiconductors with outstanding properties, such as nontoxicity, high catalytic efficiency, and extensive bandgap [1]. There is not any detailed theoretical investigation on the physical and chemical properties of brookite because of its metastable property. This meta-stability results in some troubles during the synthesis of brookite [7]. Anatase has been extensively studied due to its enhanced activity in some photo-catalysis reactions, such as TiO2-supported metal particle reactions, compared to the rutile and brookite phases [15,16,17]. As a most promising material, the widely application of TiO2based gas sensors is influenced by its wide bandgap (3–3.2 eV). This results in the absorption of a small percentage of the incoming solar light (3–5%). An enormous amount of effort has been invested in enhancing the optical response of TiO2 by nitrogen doping [8]
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