Reactions of hydrazoic acid on TiO 2 nanoparticles

An experimental and computational study

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

This article reports the results of a computational and experimental study on the reaction of hydrazoic acid, HN 3 , adsorbed on 15-20 nm TiO 2 particle films. Experimentally, FTIR spectra of HN 3 (a) have been measured by varying HN 3 dosage, UV irradiation time and surface annealing temperature. Three sharp peaks, related to v a (NNN) of HN 3 (a) and N 3 (a) with different configurations in the 2000-2200 cm -1 region, and a broad band absorption, related to associated and isolated HN(a) and HO(a) adsorptions in the 3000-3800 cm -1 region, have been detected. Computationally, molecular structures, vibrational frequencies and adsorption energies of possible adsorbates including HN 3 and its derivatives, N 3 , N 2 , NH, and H, have been predicted by first-principles calculations based on the density functional theory (DFT) and the pseudopotential method. On the basis of the experimental and computational results, the peak appeared at 2075 cm -1 , which increases at a faster rate with HN 3 exposure time, is attributed to a stable adsorbate, N3-Ti(a), with the predicted adsorption energy, E ads = 13 kcal/mol. The peak at 2118 cm -1 , which survives at the highest surface temperature in the heating experiment, is attributable to the most stable adsorbate, Ti-N 2 N(H)-O(a) with E ads = 36 kcal/mol. The peak at 2170 cm -1 , which vanishes most readily in all of the aforementioned experiments, is related to less stable molecular adsorbates, end-on HN 3 -Ti(a) with E ads = 5 kcal/mol and side-on HN(N 2 )-Ti(a) with E ads = 8 kcal/mol. A potential energy diagram for the formation of various absorbates with their transition states has been established for the HN 3 /TiO 2 system. On the basis of the predicted desorption energies, the four most stable products of the HN 3 reaction on TiO 2 are H-O(a), 118 kcal/mol; HN-O(a), 85 kcal/ mol; Ti-N 2 N(H)-O(a), 36 kcal/mol; and N 3 -O(a), 19 kcal/mol.

Original languageEnglish
Pages (from-to)5133-5142
Number of pages10
JournalJournal of Physical Chemistry B
Volume109
Issue number11
DOIs
Publication statusPublished - 2005 Mar 24

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hydrazoic acid
Adsorbates
Nanoparticles
nanoparticles
Acids
Adsorption
adsorption
Vibrational spectra
Potential energy
Molecular structure
surface temperature
pseudopotentials
Density functional theory
energy
Absorption spectra
Desorption
molecular structure
desorption
Experiments
potential energy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

Cite this

Reactions of hydrazoic acid on TiO 2 nanoparticles : An experimental and computational study. / Wang, Jeng-Han; Lin, M. C.; Sun, Ying-Chieh.

In: Journal of Physical Chemistry B, Vol. 109, No. 11, 24.03.2005, p. 5133-5142.

Research output: Contribution to journalArticle

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abstract = "This article reports the results of a computational and experimental study on the reaction of hydrazoic acid, HN 3 , adsorbed on 15-20 nm TiO 2 particle films. Experimentally, FTIR spectra of HN 3 (a) have been measured by varying HN 3 dosage, UV irradiation time and surface annealing temperature. Three sharp peaks, related to v a (NNN) of HN 3 (a) and N 3 (a) with different configurations in the 2000-2200 cm -1 region, and a broad band absorption, related to associated and isolated HN(a) and HO(a) adsorptions in the 3000-3800 cm -1 region, have been detected. Computationally, molecular structures, vibrational frequencies and adsorption energies of possible adsorbates including HN 3 and its derivatives, N 3 , N 2 , NH, and H, have been predicted by first-principles calculations based on the density functional theory (DFT) and the pseudopotential method. On the basis of the experimental and computational results, the peak appeared at 2075 cm -1 , which increases at a faster rate with HN 3 exposure time, is attributed to a stable adsorbate, N3-Ti(a), with the predicted adsorption energy, E ads = 13 kcal/mol. The peak at 2118 cm -1 , which survives at the highest surface temperature in the heating experiment, is attributable to the most stable adsorbate, Ti-N 2 N(H)-O(a) with E ads = 36 kcal/mol. The peak at 2170 cm -1 , which vanishes most readily in all of the aforementioned experiments, is related to less stable molecular adsorbates, end-on HN 3 -Ti(a) with E ads = 5 kcal/mol and side-on HN(N 2 )-Ti(a) with E ads = 8 kcal/mol. A potential energy diagram for the formation of various absorbates with their transition states has been established for the HN 3 /TiO 2 system. On the basis of the predicted desorption energies, the four most stable products of the HN 3 reaction on TiO 2 are H-O(a), 118 kcal/mol; HN-O(a), 85 kcal/ mol; Ti-N 2 N(H)-O(a), 36 kcal/mol; and N 3 -O(a), 19 kcal/mol.",
author = "Jeng-Han Wang and Lin, {M. C.} and Ying-Chieh Sun",
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T2 - An experimental and computational study

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AU - Lin, M. C.

AU - Sun, Ying-Chieh

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N2 - This article reports the results of a computational and experimental study on the reaction of hydrazoic acid, HN 3 , adsorbed on 15-20 nm TiO 2 particle films. Experimentally, FTIR spectra of HN 3 (a) have been measured by varying HN 3 dosage, UV irradiation time and surface annealing temperature. Three sharp peaks, related to v a (NNN) of HN 3 (a) and N 3 (a) with different configurations in the 2000-2200 cm -1 region, and a broad band absorption, related to associated and isolated HN(a) and HO(a) adsorptions in the 3000-3800 cm -1 region, have been detected. Computationally, molecular structures, vibrational frequencies and adsorption energies of possible adsorbates including HN 3 and its derivatives, N 3 , N 2 , NH, and H, have been predicted by first-principles calculations based on the density functional theory (DFT) and the pseudopotential method. On the basis of the experimental and computational results, the peak appeared at 2075 cm -1 , which increases at a faster rate with HN 3 exposure time, is attributed to a stable adsorbate, N3-Ti(a), with the predicted adsorption energy, E ads = 13 kcal/mol. The peak at 2118 cm -1 , which survives at the highest surface temperature in the heating experiment, is attributable to the most stable adsorbate, Ti-N 2 N(H)-O(a) with E ads = 36 kcal/mol. The peak at 2170 cm -1 , which vanishes most readily in all of the aforementioned experiments, is related to less stable molecular adsorbates, end-on HN 3 -Ti(a) with E ads = 5 kcal/mol and side-on HN(N 2 )-Ti(a) with E ads = 8 kcal/mol. A potential energy diagram for the formation of various absorbates with their transition states has been established for the HN 3 /TiO 2 system. On the basis of the predicted desorption energies, the four most stable products of the HN 3 reaction on TiO 2 are H-O(a), 118 kcal/mol; HN-O(a), 85 kcal/ mol; Ti-N 2 N(H)-O(a), 36 kcal/mol; and N 3 -O(a), 19 kcal/mol.

AB - This article reports the results of a computational and experimental study on the reaction of hydrazoic acid, HN 3 , adsorbed on 15-20 nm TiO 2 particle films. Experimentally, FTIR spectra of HN 3 (a) have been measured by varying HN 3 dosage, UV irradiation time and surface annealing temperature. Three sharp peaks, related to v a (NNN) of HN 3 (a) and N 3 (a) with different configurations in the 2000-2200 cm -1 region, and a broad band absorption, related to associated and isolated HN(a) and HO(a) adsorptions in the 3000-3800 cm -1 region, have been detected. Computationally, molecular structures, vibrational frequencies and adsorption energies of possible adsorbates including HN 3 and its derivatives, N 3 , N 2 , NH, and H, have been predicted by first-principles calculations based on the density functional theory (DFT) and the pseudopotential method. On the basis of the experimental and computational results, the peak appeared at 2075 cm -1 , which increases at a faster rate with HN 3 exposure time, is attributed to a stable adsorbate, N3-Ti(a), with the predicted adsorption energy, E ads = 13 kcal/mol. The peak at 2118 cm -1 , which survives at the highest surface temperature in the heating experiment, is attributable to the most stable adsorbate, Ti-N 2 N(H)-O(a) with E ads = 36 kcal/mol. The peak at 2170 cm -1 , which vanishes most readily in all of the aforementioned experiments, is related to less stable molecular adsorbates, end-on HN 3 -Ti(a) with E ads = 5 kcal/mol and side-on HN(N 2 )-Ti(a) with E ads = 8 kcal/mol. A potential energy diagram for the formation of various absorbates with their transition states has been established for the HN 3 /TiO 2 system. On the basis of the predicted desorption energies, the four most stable products of the HN 3 reaction on TiO 2 are H-O(a), 118 kcal/mol; HN-O(a), 85 kcal/ mol; Ti-N 2 N(H)-O(a), 36 kcal/mol; and N 3 -O(a), 19 kcal/mol.

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