Heterogeneous chemistry of NO₂ on mineral oxide particles: Spectroscopic evidence for oxide‐coordinated and water‐solvated surface nitrate

In situ DRIFTS study of hygroscopic behavior of mineral aerosol

“…After this process, the oxides surfaces were covered with nitrate species. When the RH increased from 2% to 95%, these peaks disappeared while the peak at 1650 cm −1 due to the bending mode of water as well as two peaks at 1415 and 1350 cm −1 which were due to watersolvated nitrate (Miller and Grassian, 1998;Goodman et al, 2001) were observed (Fig. 7b).…”

“…These peaks are assigned to bridging, monodentate, bidentate, and isolated nitrate (Underwood et al, 1999;Zhang et al, 2008). The mechanism of nitrate species formation on mineral oxides surfaces were studied thoroughly (Miller and Grassian, 1998;Underwood et al, 1999). Nitrite was observed as the intermediate which was then to form nitrate species by the reactions with gas-phase NO 2 in an Eley-Rideal type mechanism or with another surface nitrite in a LangmuirHinshelwood type mechanism (Underwood et al, 1999).…”

Experimental and theoretical studies of surface nitrate species on Ag/Al2O3 using DRIFTS and DFT

“…3), and the simulated IR spectrum and frequency were shown in Fig. 4d and [15]. Therefore, the model d for the watersolvated nitrate was not fit for our experimental condition because the gas mixture was dry and the catalyst was pretreated at 873 K for 60 min before collecting the spectra.…”

“…Grassian and coworkers [15,16] proposed that the adsorption peak of the free solvated nitrate aqueous ion over Al 2 O 3 at 298 K was also around 1302 cm −1 and the addition of water promoted the formation of free nitrate. Accordingly, we calculated the uncoordinated nitrate ions as shown in model d (Fig.…”

“…Although the surface nitrate species have been discussed and the structures were proposed in the literatures, the interpretations of the infrared spectra proposed by researchers were quite contradictory. A typical example is the band observed around 1300 cm −1 , which has been attributed to monodentate nitrate [9], bidentate nitrate [10,12] or solvated nitrate [15,16], and so on. As a result, the assignment and structures of the nitrates species on Ag/Al 2 O 3 and Al 2 O 3 were still not clear.…”