A Computational Study on Adsorption Configurations and Dissociative Reactions of the HN₃ Molecule on the TiO₂ Anatase (101) Surface

Abstract

This study investigates the adsorption configurations and the dissociative reactions of HN 3 on the TiO 2 anatase (101) surface by first-principles calculations. The results show that there are six different adsorption configurations of HN 3 adsorbed on the surface. Among those adsorption configurations, the most stable adsorbate configuration is side-on HN(N 2 )-Ti(a), with an adsorption energy of 10.2 kcal/mol. In addition, for the HN 3 fragments, the most stable adsorbate is Ti-(H)N-O(a), with an adsorption energy of 69.8 kcal/ mol. The effect of the H present in the coadsorbed configuration significantly increases the adsorption energy by 46.4, 44.2, and 49.2 kcal/mol for the adsorbates of N 3 -Ti(a), Ti-N 3 -O(a), and Ti-N 3 -Ti(a), respectively. The lowest two energy levels for dissociative adsorbates are Ti-(H)N-O(a) + N 2 -Ti(a) and N 3 -Ti(a) a + H-O(a), and their energies are 5.7 and -12.8 kcal/mol, respectively. In addition, for the latter dissociative adsorbates, the two lowest energy barriers for these adsorbates that transit from their initial end-to-end Ti-N 3 H • • • O*(a) and end-to-end Ti-N 3 H-O(a) are approximately 2.6 kcal/mol. The comparison made between HN 3 on both anatase and rutile surfaces shows that the reactions of dissociative adsorptions of HN 3 are endothermic for Ti-(H)N-O(a) + N 2 -Ti(a) and exothermic for N 3 -Ti(a) a + O-H(a) on the anatase (101) surface, while both are exothermic on the rutile (110) surface.

Role of Hydroxyl Groups in the NHx (x = 1−3) Adsorption on the TiO2 Anatase (101) Surface Determined by a First-Principles Study

“…Both of them pointed out that surface properties might be significantly modified by the hydroxyl groups; even only one OH can facilitate O 2 adsorption on the TiO 2 rutile surface. This phenomenon also has been confirmed by other recent publications that examine the hydroxyl’s effect on reaction pathways on the anatase surface such that the hydroxyl group’s presence on the surface might influence the adsorption of other molecules, such as CH 3 OH, B(OH) 3 , HN 3 , NH 3 , H 2 S, and HNO 3 on the TiO 2 anatase surface. In addition, Zapol and co-worker also reported that the morphology of TiO 2 nanocrystals is affected by the presence of water and the consideration of hydrated nanocrystal surfaces is necessary to accurately predict the correct size dependence of the anatase-to-rutile phase transition.…”

“…To achieve better device functionality of dye-sensitizer solar cells, − different kinds of gas-phase molecules have been reacted with the TiO 2 surface at the Ti cation site (or O anion site) to form specific adsorbates that functionalize the TiO 2 surface. The adsorbates may then act as precursors − that allow gas molecules to subsequently react, anchoring groups − that provide better electron transfer or doping molecules − that narrow the band gap or band shift , to increase the photovoltaic efficiency. Thus, understanding the reactivity of gas molecules and the reaction mechanism is not only of fundamental scientific interest but also of use in anticipating the success of an engineering process.…”

Adsorption and dissociation of NH3 on clean and hydroxylated TiO2 rutile (110) surfaces: A computational study

“…A recent publication23 has pointed out that surface properties might be significantly altered by the presence of the hydroxyl group—it was found that the hydroxyl group can facilitate O 2 adsorption on the metal oxide surface not only on the nearby metal cation but also the distant metal cation. This phenomenon also has been confirmed by other recent publications, for example, HN 3 ,7, 24 B(OH) 3 ,25, 26 NH 3 ,27 HNO 3 ,28a and H 2 S28b Therefore, realistic modeling of the reactivity of the gas phase molecule on the TiO 2 surface must simultaneously consider the presence of hydroxyl groups due to the pervasiveness of the defects.…”

A Model DMMP/TiO2 (110) Intermolecular Potential Energy Function Developed from ab Initio Calculations

“…A number of experimental studies have examined the reaction of gas-phase DMMP with TiO 2 and the DMMP–TiO 2 surface interaction. − The DMMP molecule interacts through the electron-rich phosphoryl oxygen with surface-bound hydroxyl groups and with Lewis acid sites of the TiO 2 by donating a lone pair of electrons to the Ti n + ( n = 3, 4) . There have been a number of theoretical studies of molecular interactions on the surface of TiO 2 such as O( 3 P)–TiO 2 , O 2 –TiO 2 , H 2 O–TiO 2 , ,− CH 3 OH–TiO 2 , NH 3 –TiO 2 , pyridine–TiO 2 , peptide–TiO 2 , poly(ethylene oxide)–TiO 2 , catechol–TiO 2 , , and lipid–TiO 2 , which have provided detailed insight concerning the adsorption and decomposition processes.…”