Theoretical Study of the Dissociation of Nitric Acid at a Model Aqueous Surface

Bianco, Roberto; Wang, Shuzhi; Hynes, James T.

doi:10.1021/jp075054a

Cited by 45 publications

(91 citation statements)

References 74 publications

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“…43,50 Indeed, NO3 -adsorption on aqueous interfaces was studied previously using electronic structure methods and their asym-NOstr. splittings were shown to be strongly correlated with their intramolecular distortion 49,60 and to be of the same magnitude as those reported herein. Interestingly, splittings as large as 200-250 cm -1 are observed for the most distorted nitrates as can be gleaned from Figure 1.…”

Section: Resultssupporting

confidence: 80%

Surface-Enhanced Nitrate Photolysis on Ice

et al. 2015

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Abstract:Heterogeneous nitrates photolysis is the trigger for many chemical processes occurring in the polar boundary layer and is widely believed to occur in a quasiliquid layer (QLL) at the surface of ice. The dipole forbidden character of the electronic transition relevant to boundary layer atmospheric chemistry and the small photolysis/photoproducts quantum yields in ice (and in water) may confer a significant enhancement and interfacial specificity to this important photochemical reaction at the surface of ice. Using amorphous solid water films at cryogenic temperatures as models for the disordered interstitial air/ice interface within the snowpack suppresses the diffusive uptake kinetics thereby prolonging the residence time of nitrate anions at the surface of ice. This approach allows their slow heterogeneous photolysis kinetics to be studied providing the first direct evidence that nitrates adsorbed onto the first molecular layer at the surface of ice are photolyzed more effectively than those dissolved within the bulk. Vibrational spectroscopy allows the ~3-fold enhancement in photolysis rates to be correlated with the nitrates' distorted intramolecular geometry thereby hinting at the role played by the greater chemical heterogeneity in their solvation environment at the surface of ice than in the bulk. A simple 1D kinetic model suggests 1-that a 3(6)-fold enhancement in photolysis rate for nitrates adsorbed onto the ice surface could increase the photochemical NO2 emissions from a 5(8) nm thick photochemically active interfacial layer by 30%(60)%, and 2-that 25%(40%) of the NO2 photochemical emissions to the snowpack interstitial air are released from the top-most molecularly thin surface layer on ice. These findings may provide a new paradigm for heterogeneous (photo)chemistry at temperatures below those required for a QLL to form at the ice surface.

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Section: Resultssupporting

confidence: 80%

Surface-Enhanced Nitrate Photolysis on Ice

et al. 2015

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“…Furthermore, the calculated partial charges on these 2 moieties increase dramatically from ␦(NO In separate experiments ( (54); in those cases, Cl Ϫ from the dissociation of solvated HCl is the reactive species (35,41,42). However, acids at the top of the air-water interface are largely undissociated (34,40,(43)(44)(45). Given this and the fact that water adsorbed on solid substrates at room temperature does not behave like water in the bulk (46)(47)(48), it is likely that the reactant in the surface-mediated reaction reported here is molecular HCl.…”

Section: Nomentioning

confidence: 98%

Chlorine activation indoors and outdoors via surface-mediated reactions of nitrogen oxides with hydrogen chloride

Raff

Njegic

Chang

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

113

182

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Gaseous HCl generated from a variety of sources is ubiquitous in both outdoor and indoor air. Oxides of nitrogen (NO y ) are also globally distributed, because NO formed in combustion processes is oxidized to NO 2 , HNO 3 , N 2 O 5 and a variety of other nitrogen oxides during transport. Deposition of HCl and NO y onto surfaces is commonly regarded as providing permanent removal mechanisms. However, we show here a new surface-mediated coupling of nitrogen oxide and halogen activation cycles in which uptake of gaseous NO 2 or N 2 O 5 on solid substrates generates adsorbed intermediates that react with HCl to generate gaseous nitrosyl chloride (ClNO) and nitryl chloride (ClNO 2 ), respectively. These are potentially harmful gases that photolyze to form highly reactive chlorine atoms. The reactions are shown both experimentally and theoretically to be enhanced by water, a surprising result given the availability of competing hydrolysis reaction pathways. Airshed modeling incorporating HCl generated from sea salt shows that in coastal urban regions, this heterogeneous chemistry increases surface-level ozone, a criteria air pollutant, greenhouse gas and source of atmospheric oxidants. In addition, it may contribute to recently measured high levels of ClNO 2 in the polluted coastal marine boundary layer. This work also suggests the potential for chlorine atom chemistry to occur indoors where significant concentrations of oxides of nitrogen and HCl coexist.

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“…25 Both theory and experiment suggest that nitric acid is not fully dissociated at the interface of aqueous solutions. [26][27][28][29][30][31][32][33][34] Indeed, recent results suggest that undissociated HNO 3 interacts very weakly with water. 33,34 Because of the presence of significant concentrations of water vapor in the lower atmosphere, there is an abundance of water available on surfaces such as roads, buildings, etc., as well as in airborne particles.…”

Section: Introductionmentioning

confidence: 99%

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

Moussa

Stern

Raff

et al. 2013

Phys. Chem. Chem. Phys.

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Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer surface of a germanium infrared-transmitting attenuated total reflectance (ATR) crystal that was coated with a thin layer of silicon oxide (SiO x ). The SAM was exposed at 298 AE 2 K to dry HNO 3 in a flow of N 2 , followed by HNO 3 in humid N 2 at a controlled relative humidity (RH) between 20-90%. For comparison, similar studies were carried out using a similar crystal without the SAM coating. Changes in the surface were followed using Fourier transform infared spectroscopy (FTIR). In the case of the SAMcoated crystal, molecular HNO 3 and smaller amounts of NO 3 À ions were observed on the surface upon exposure to dry HNO 3 . Addition of water vapor led to less molecular HNO 3 and more H 3 O + and NO 3 À complexed to water, but surprisingly, molecular HNO 3 was still evident in the spectra up to 70% RH.This suggests that part of the HNO 3 observed was initially trapped in pockets within the SAM and shielded from water vapor. After increasing the RH to 90% and then exposing the film to a flow of dry N 2 , molecular nitric acid was regenerated, as expected from recombination of protons and nitrate ions as water evaporated. The nitric acid ultimately evaporated from the film. On the other hand, exposure of the SAM to HNO 3 and H 2 O simultaneously gave only hydronium and nitrate ions. Molecular dynamics simulations of defective SAMs in the presence of HNO 3 and water predict that nitric acid intercalates in defects as a complex with a single water molecule that is protected by alkyl chains from interacting with additional water molecules. These studies are consistent with the recently proposed hydrophobic nature of HNO 3 . Under atmospheric conditions, if HNO 3 is formed in organic layers on surfaces in the boundary layer, e.g. through NO 3 or N 2 O 5 reactions, it may exist to a significant extent in its molecular form rather than fully dissociated to nitrate ions. IntroductionNitric acid is considered to be the end-product of oxidation of oxides of nitrogen in the atmosphere. 1 This acid reacts with ammonia and amines to form solid or aqueous phase nitrate particles, and can also be taken up into other types of atmospheric particles. Removal of gaseous HNO 3 and particulate nitrates takes place primarily through wet and dry deposition, in what were once considered to be terminal removal processes. However, there are now a number of laboratory and field studies that suggest that nitric acid can be converted back into gaseous oxides of nitrogen such as NO, NO 2 and HONO. 2-8Nitric acid is a strong acid, but it requires a cluster of at least four water molecules to dissociate in the gas phase. [9][10][11] In bulk aqueous solutions and on ice, nitric acid can form hydrates with 1, 2 or 3 water molecules, depending on the concentration. 12-24 Such hydrates, as well as the HNO 3 dimer, have also been seen on solid surfaces during the hydrolysis of NO 2 at

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Theoretical Study of the Dissociation of Nitric Acid at a Model Aqueous Surface

Cited by 45 publications

References 74 publications

Surface-Enhanced Nitrate Photolysis on Ice

Surface-Enhanced Nitrate Photolysis on Ice

Chlorine activation indoors and outdoors via surface-mediated reactions of nitrogen oxides with hydrogen chloride

Experimental and theoretical studies of the interaction of gas phase nitric acid and water with a self-assembled monolayer

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