FTIR and TPD Study of the Room Temperature Interaction of a NO–Oxygen Mixture and of NO₂ with Titanium Dioxide

Abstract

In the present paper, kinetics and mechanism of NO and oxygen coadsorption on TiO2 at room temperature, which is the key step of the catalytic removal of NOx pollutants from air, were studied. NO adsorption on TiO2 in the absence of oxygen is weak and reversible, but it is found to strongly increase in the presence of oxygen. The ratio between the amount of adsorbed NO and O2 in the course of adsorption is constant and close to three. A FTIR spectroscopic study reveals that the amount and composition of N-containing species on the TiO2 surface strongly depend on the contact time with the initial NO–O2 mixture and on its composition. At relatively small exposures, IR bands assigned to NO– and nitrosyl complexes Ti n+ –NO (n = 3–4) are predominant in the spectra. With increasing contact time, NO– disappears, and IR bands of NO3 – and possibly NO2 – appear and grow. The thermal stability of surface nitrates and nitrites correlates with their structure. IR spectra observed upon NO2 adsorption are similar to those after exposure to NO–O2 mixtures. Exposure of the sample with preadsorbed 14NO2 to gaseous 15NO results in a change in the IR spectra that suggests isotopic replacement of 14N with 15N in the adsorbed species. In the TPD profiles, after adsorption of NO–O2 and NO2, desorption peaks of NO and NO2 dominate which presumably arise from the thermal decomposition of NO3 – (NO2 –) and nitrosyls Ti n+ –NO. A multistep scheme for the interaction of NO and O2 with TiO2 is suggested which accounts for the results of both techniques applied.

Influence of External Gaseous Environments on the Electrical Properties of ZnO Nanostructures Obtained by a Hydrothermal Method

“…At RT, NO 2 is absorbed by ZnO nanostructures mainly in the form of NO 3 − ions with evacuation of gaseous NO [8,44]. At the elevated temperature, the absorbed NO 3 − undergoes decomposition to gaseous NO 2 and adsorbed O − .…”

A new strategy for utilization of NIR from solar energy—Promotion effect generated from photothermal effect of Fe3O4@SiO2 for photocatalytic oxidation of NO

“…In the initial of the photocatalytic process, HNO 3 and NO 2 were the main products for both P25 and P25/Fe 3 O 4 @SiO 2 [40], and the NO 3 − coated on the photocatalyst could be detected in the in-situ FTIR spectra in Fig. S7 (peaks at 1538, 1419, 1330 and 1290 cm −1 ) [41][42][43]. With the reaction time increased, NO 2 gradually became the only product, which could be verified by the NO 2 selectivity of the composed samples in Fig.…”

Stability and Surface Reactivity of Anatase TiO2Films

“…41,49 In fact, all peaks in the 1950-1700 cm −1 interval can be assigned to NO stretching vibrations on Ti 4+ and Ti 3+ . 37,40 Films annealed at 900…”