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Nguyen HVL, Koziol KJ, Trabelsi T, Khemissi S, Schwell M, Francisco JS, Kleiner I. Discovery of a Missing Link: First Observation of the HONO-Water Complex. J Phys Chem Lett 2022; 13:8648-8652. [PMID: 36083614 DOI: 10.1021/acs.jpclett.2c02081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The still unexplained daytime HONO concentration in the Earth's atmosphere and the impact of water on the HONO chemistry have been a mystery for decades. Several pathways and many modeling methods have failed to reproduce the atmospheric measurements. We reveal in this study the first spectroscopic observation and characterization of the complex of HONO with water observed through its rotational signature. Under the experimental conditions, HONO-water is stable, particularly straightforward to form, and features intense absorption signals. This could explain both the influence of water on the HONO chemistry and the missing HONO sources, as well as the missing contribution of many other molecules of atmospheric relevance that skew the accuracy of field measurements and the full account of partitioning species in the atmosphere.
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Zhang S, Zhang C, Fu Y, Li L, Huang C, Lin Y, Zhu C, Francisco JS, He Z, Zhou X, Wang J. Role of an Ice Surface in the Photoreaction of Coumarins. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:11346-11353. [PMID: 36066243 DOI: 10.1021/acs.langmuir.2c01637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Ice affects many chemical reactions in nature, which greatly influences the atmosphere, climate, and life. However, the exact mechanism of ice in these chemical reactions remains elusive. For example, it is still an open question as to whether ice can act as a catalyst to greatly enhance the reactivity and selectivity, which is essential for the production of some natural compounds in our planet. Here, we discover that ice can lead to high efficiency and stereoselectivity of the [2 + 2] photodimerization of coumarin and its derivatives. The conversion of the [2 + 2] photodimerization of coumarins enhanced by ice is dozens of times higher than that in the unfrozen saturated solution, and the reaction displays a high syn-head-head stereoselectivity (>95%) in comparison with those in the absence of the ice. Note that almost no reaction occurs in the crystal powder and melt of the coumarins, indicating that the role of ice in the photodimerization reaction is not simply due to the usual mechanisms found in the freezing concentration. We further reveal that the reaction rate is found to be proportional to the total area of the ice surface and follows Michaelis-Menten-like kinetics, indicating that the ice surface catalyzes the reaction. Molecular dynamics simulations demonstrate that ice surfaces can induce reactants to form a two-dimensional liquid-crystal-ordered layer with a suitable intermolecular distance and unique side-by-side packing, facilitating stereoselective photodimerization for syn-head-head dimers. These findings give evidence that ice-surface-induced molecular assembly may play an important role in atmospheric heterogeneous photoreaction processes.
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Zhao YC, Long B, Francisco JS. Quantitative Kinetics of the Reaction between CH 2OO and H 2O 2 in the Atmosphere. J Phys Chem A 2022; 126:6742-6750. [DOI: 10.1021/acs.jpca.2c04408] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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54
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trabelsi T, Francisco JS. Ground state spectroscopy and photochemistry of HAlOH. J Chem Phys 2022; 157:124307. [DOI: 10.1063/5.0105814] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ab initio calculations were carried out in order to study the electronic structure and spectroscopy of cis-HAlOH, trans-HAlOH, H2AlO, and AlOH2. The cis structure is more stable than the trans, and both are thermodynamically stable relative to the AlOH + H dissociation limit. A set of spectroscopic constants were generated for the lowest stable isomers to help with their detection in the laboratory and in the interstellar medium. The first excited state absorbs strongly in the visible region (λ = 460 nm), with a predicted transition dipole moment of 2.07 debyes. The electronic structures of the first excited state were calculated, including the lifetime adiabatic excitation energy, rotational constants, and frequencies. We have shown that both isomers may be suitable for laser-induced fluorescence detection. Finally, photodissociation of the cis- and trans-HAlOH isomers is a plausible mechanism for the production of AlOH and H.
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Li B, Kumar M, Zhou C, Li L, Francisco JS. Mechanistic Insights into Criegee Intermediate-Hydroperoxyl Radical Chemistry. J Am Chem Soc 2022; 144:14740-14747. [PMID: 35921588 DOI: 10.1021/jacs.2c05346] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction between a Criegee intermediate and the hydroperoxyl radical (HO2) is believed to play a role in the formation of new particles in the troposphere. Although the reaction has been previously studied in the gas phase, there are several knowledge gaps that still need to be filled. We simulated the reaction of anti-CH3CHOO with HO2 and HO2-H2O radical complexes in the gas phase at 0 K, which exhibited a low-barrier profile for water-containing systems and a barrierless profile for water-free systems. Moreover, the reaction was found to follow a proton-transfer mechanism, which challenges previous assumptions that the gas-phase reaction involves a hydrogen atom transfer. The HO2 radical was found to mediate the Criegee hydration reaction in the gas phase. Metadynamics simulations further confirmed that the expected radical adduct formation between anti-CH3CHOO and the HO2 radical, as well as the HO2- and H2O-mediated reactions in the gas phase, followed a concerted mechanism. By combining constrained ab initio molecular dynamics simulations with thermodynamic integration, we quantitively evaluated the free-energy barriers at high temperatures. The barriers obtained for all three Criegee-HO2 reaction systems were found to be temperature-dependent. We also compared the free-energy barriers of water-free and water-containing systems; the results revealed that water could hinder the reaction between the Criegee and HO2 radical. These results suggest that HO2 radicals may be involved in the formation of tropospheric radical adducts, and water molecules may also play important roles in the reactions of Criegee intermediates.
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Francés-Monerris A, Carmona-García J, Trabelsi T, Saiz-Lopez A, Lyons JR, Francisco JS, Roca-Sanjuán D. Photochemical and thermochemical pathways to S 2 and polysulfur formation in the atmosphere of Venus. Nat Commun 2022; 13:4425. [PMID: 35907911 PMCID: PMC9338966 DOI: 10.1038/s41467-022-32170-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 07/18/2022] [Indexed: 11/25/2022] Open
Abstract
Polysulfur species have been proposed to be the unknown near-UV absorber in the atmosphere of Venus. Recent work argues that photolysis of one of the (SO)2 isomers, cis-OSSO, directly yields S2 with a branching ratio of about 10%. If correct, this pathway dominates polysulfur formation by several orders of magnitude, and by addition reactions yields significant quantities of S3, S4, and S8. We report here the results of high-level ab-initio quantum-chemistry computations that demonstrate that S2 is not a product in cis-OSSO photolysis. Instead, we establish a novel mechanism in which S2 is formed in a two-step process. Firstly, the intermediate S2O is produced by the coupling between the S and Cl atmospheric chemistries (in particular, SO reaction with ClS) and in a lesser extension by O-abstraction reactions from cis-OSSO. Secondly, S2O reacts with SO. This modified chemistry yields S2 and subsequent polysulfur abundances comparable to the photolytic cis-OSSO mechanism through a more plausible pathway. Ab initio quantification of the photodissociations at play fills a critical data void in current atmospheric models of Venus. Polysulfur compounds have been ascribed as the unknown near-UV absorbers in Venusian atmosphere and play a key role in the sulfur chemical cycle of this planet. Here, authors establish their production from (SO)2 on the grounds of quantifications of photochemical and thermal pathways involved in the sulfur chemical cycle of the planet.
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Sun J, Cheng Z, Huang Q, He H, Francisco JS, Du S. Universal Principle for Large-Scale Production of a High-Quality Two-Dimensional Monolayer via Positive Charge-Driven Exfoliation. J Phys Chem Lett 2022; 13:6597-6603. [PMID: 35833746 DOI: 10.1021/acs.jpclett.2c01403] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
On the basis of the intrinsic characteristics of the layered materials, here we report a universal principle for the production of intact monolayers via layer-by-layer exfoliation from their bulk via positive charge doping. At experimental accessible densities (nc) of ∼1014 cm-2, various multilayer crystals, including graphite, hexagonal boron nitride, transition metal dichalcogenides, MXenes, and black phosphorus, can be exfoliated into the corresponding monolayers through ab initio density functional theory stimulations. The carrier critical thresholds for exfoliating are found to be nearly independent of thickness but dependent on surface size. The universality of positive charge-driven exfoliation originates from the common intrinsic characteristics of electronic structures for layered materials. The positively doped charges that preferentially accumulate near the surface induce interlayer repulsion, leading to layer-by-layer exfoliation when repulsion surpasses interlayer van der Waals force. This strategy may open the possibility of producing diverse high-quality two-dimensional monolayers with a small number of defects toward large-scale manufacturing.
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Yuan DF, Trabelsi T, Zhang YR, Francisco JS, Wang LS. Probing the Electronic Structure and Bond Dissociation of SO 3 and SO 3- Using High-Resolution Cryogenic Photoelectron Imaging. J Am Chem Soc 2022; 144:13740-13747. [PMID: 35857818 DOI: 10.1021/jacs.2c04698] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The SO3 molecule and its radical anion SO3- are important chemical species atmospherically. However, their thermodynamic properties and electronic structures are not well known experimentally. Using cryogenically cooled anions, we have obtained high-resolution photoelectron images of SO3- and determined accurately the electron affinity (EA) of SO3 and the bond dissociation energy of SO3- → SO2 + O- for the first time. Because of the large geometry changes from the C3v SO3- to the D3h SO3, there is a negligible Franck-Condon factor (FCF) for the 0-0 detachment transition, that defines the EA of SO3. By fitting the high-resolution photoelectron spectra with computed FCFs using structures from high-level ab initio calculations, we have determined the EA of SO3 to be 2.126(6) eV. By monitoring the appearance of the O- signal in the photoelectron images at different photon energies, we are able to measure directly the bond dissociation energy of SO3-(X2A1) → SO2(X1A1) + O-(2P) to be 4.259 ± 0.006 eV, which also allow us to derive the dissociation energy for the spin-forbidden SO3(X1A1') → SO2(X1A1) + O(3P) to be 3.594(6) eV. The excited states of SO3- are calculated using high-level ab initio calculations, which are valuable in aiding the interpretation of autodetachment processes observed at various photon energies. The current study provides valuable information about the fundamental molecular properties of SO3, as well as the radical anion SO3-, which is known in redox reactions involving SO32- and may also play a role in the chemistry of SO2 in the atmosphere.
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Saiz‐Lopez A, Acuña AU, Mahajan AS, Dávalos JZ, Feng W, Roca‐Sanjuán D, Carmona‐García J, Cuevas CA, Kinnison DE, Gómez Martín JC, Francisco JS, Plane JMC. The Chemistry of Mercury in the Stratosphere. GEOPHYSICAL RESEARCH LETTERS 2022; 49:e2022GL097953. [PMID: 35860422 PMCID: PMC9285414 DOI: 10.1029/2022gl097953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 05/23/2022] [Accepted: 05/24/2022] [Indexed: 06/15/2023]
Abstract
Mercury, a global contaminant, enters the stratosphere through convective uplift, but its chemical cycling in the stratosphere is unknown. We report the first model of stratospheric mercury chemistry based on a novel photosensitized oxidation mechanism. We find two very distinct Hg chemical regimes in the stratosphere: in the upper stratosphere, above the ozone maximum concentration, Hg0 oxidation is initiated by photosensitized reactions, followed by second-step chlorine chemistry. In the lower stratosphere, ground-state Hg0 is oxidized by thermal reactions at much slower rates. This dichotomy arises due to the coincidence of the mercury absorption at 253.7 nm with the ozone Hartley band maximum at 254 nm. We also find that stratospheric Hg oxidation, controlled by chlorine and hydroxyl radicals, is much faster than previously assumed, but moderated by efficient photo-reduction of mercury compounds. Mercury lifetime shows a steep increase from hours in the upper-middle stratosphere to years in the lower stratosphere.
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He G, Ma J, Chu B, Hu R, Li H, Gao M, Liu Y, Wang Y, Ma Q, Xie P, Zhang G, Zeng XC, Francisco JS, He H. Inside Cover: Generation and Release of OH Radicals from the Reaction of H
2
O with O
2
over Soot (Angew. Chem. Int. Ed. 21/2022). Angew Chem Int Ed Engl 2022. [DOI: 10.1002/anie.202204829] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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61
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Long B, Xia Y, Bao JL, Carmona-García J, Gómez Martín JC, Plane JMC, Saiz-Lopez A, Roca-Sanjuán D, Francisco JS. Reaction of SO 3 with HONO 2 and Implications for Sulfur Partitioning in the Atmosphere. J Am Chem Soc 2022; 144:9172-9177. [PMID: 35576167 DOI: 10.1021/jacs.2c03499] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sulfur trioxide is a critical intermediate for the sulfur cycle and the formation of sulfuric acid in the atmosphere. The traditional view is that sulfur trioxide is removed by water vapor in the troposphere. However, the concentration of water vapor decreases significantly with increasing altitude, leading to longer atmospheric lifetimes of sulfur trioxide. Here, we utilize a dual-level strategy that combines transition state theory calculated at the W2X//DF-CCSD(T)-F12b/jun'-cc-pVDZ level, with variational transition state theory with small-curvature tunneling from direct dynamics calculations at the M08-HX/MG3S level. We also report the pressure-dependent rate constants calculated using the system-specific quantum Rice-Ramsperger-Kassel (SS-QRRK) theory. The present findings show that falloff effects in the SO3 + HONO2 reaction are pronounced below 1 bar. The SO3 + HONO2 reaction can be a potential removal reaction for SO3 in the stratosphere and for HONO2 in the troposphere, because the reaction can potentially compete well with the SO3 + 2H2O reaction between 25 and 35 km, as well as the OH + HONO2 reaction. The present findings also suggest an unexpected new product from the SO3 + HONO2 reaction, which, although very short-lived, would have broad implications for understanding the partitioning of sulfur in the stratosphere and the potential for the SO3 reaction with organic acids to generate organosulfates without the need for heterogeneous chemistry.
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He G, Ma J, Chu B, Hu R, Li H, Gao M, Liu Y, Wang Y, Ma Q, Xie P, Zhang G, Zeng XC, Francisco JS, He H. Generation and Release of OH Radicals from the Reaction of H
2
O with O
2
over Soot. Angew Chem Int Ed Engl 2022; 61:e202201638. [DOI: 10.1002/anie.202201638] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Indexed: 11/08/2022]
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63
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Wan Z, Zhu C, Francisco JS. Microscopic Insight into Water Desalination through Nanoporous Graphene: The Influence of the Dipole Moment. J Phys Chem Lett 2022; 13:4029-4035. [PMID: 35486452 DOI: 10.1021/acs.jpclett.2c00935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Nanoporous graphene membranes with controllable pore size and chemical functionality may be one of the most desirable materials for water desalination. Herein, we investigate desalination performance of hydrogen-functionalized nanoporous graphene membranes. The charge values on hydrogen atoms (qH) and carbon atoms at the pore rim are systematically adjusted. For qH > 0, the flow rate decreases as qH increases, whereas for qH < 0, the flow rate tends to increase first and then decrease with increasing qH, yielding a peak at ∼ -0.2 e. Moreover, nanopores with large dipole moments at the rim have little effect on the salt rejection. The calculated oxygen and hydrogen density maps, the potential of mean force for water molecule and salt ion passage through the nanopores, and the coordination number unveil the mechanisms underlying water desalination in nanoporous graphene. This work may inspire the design and improvement of two-dimensional membranes for water desalination.
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He G, Ma J, Chu B, Hu R, Li H, Gao M, Liu Y, Wang Y, Ma Q, Xie P, Zhang G, Zeng XC, Francisco JS, He H. Innentitelbild: Generation and Release of OH Radicals from the Reaction of H
2
O with O
2
over Soot (Angew. Chem. 21/2022). Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202204829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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65
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Hansen AS, Qian Y, Sojdak CA, Kozlowski MC, Esposito VJ, Francisco JS, Klippenstein SJ, Lester MI. Rapid Allylic 1,6 H-Atom Transfer in an Unsaturated Criegee Intermediate. J Am Chem Soc 2022; 144:5945-5955. [PMID: 35344666 DOI: 10.1021/jacs.2c00055] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A novel allylic 1,6 hydrogen-atom-transfer mechanism is established through infrared activation of the 2-butenal oxide Criegee intermediate, resulting in very rapid unimolecular decay to hydroxyl (OH) radical products. A new precursor, Z/E-1,3-diiodobut-1-ene, is synthesized and photolyzed in the presence of oxygen to generate a new four-carbon Criegee intermediate with extended conjugation across the vinyl and carbonyl oxide groups that facilitates rapid allylic 1,6 H-atom transfer. A low-energy reaction pathway involving isomerization of 2-butenal oxide from a lower-energy (tZZ) conformer to a higher-energy (cZZ) conformer followed by 1,6 hydrogen transfer via a seven-membered ring transition state is predicted theoretically and shown experimentally to yield OH products. The low-lying (tZZ) conformer of 2-butenal oxide is identified based on computed anharmonic frequencies and intensities of its conformers. Experimental IR action spectra recorded in the fundamental CH stretch region with OH product detection by UV laser-induced fluorescence reveal a distinctive IR transition of the low-lying (tZZ) conformer at 2996 cm-1 that results in rapid unimolecular decay to OH products. Statistical RRKM calculations involving a combination of conformational isomerization and unimolecular decay via 1,6 H-transfer yield an effective decay rate keff(E) on the order of 108 s-1 at ca. 3000 cm-1 in good accord with the experiment. Unimolecular decay proceeds with significant enhancement due to quantum mechanical tunneling. A rapid thermal decay rate of ca. 106 s-1 is predicted by master-equation modeling of 2-butenal oxide at 298 K, 1 bar. This novel unimolecular decay pathway is expected to increase the nonphotolytic production of OH radicals upon alkene ozonolysis in the troposphere.
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Zhong J, Li L, Kumar M, Zeng XC, Zhang J, Francisco JS. Solvation and Hydrolysis Reaction of Isocyanic Acid at the Air-Water Interface: A Computational Study. J Am Chem Soc 2022; 144:5315-5322. [PMID: 35290046 DOI: 10.1021/jacs.1c10703] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Isocyanic acid (HNCO) is known to be inert to strong oxidants and photolysis in the atmosphere but often appears in different forms of smoke; therefore, it is linked to various smoke-related illnesses due to tobacco usage or wildfire events. To date, the major loss pathway of HNCO is believed to be through its uptake on aerosol droplets. However, the molecular mechanisms underlying such an uptake process are still incompletely understood. Herein, we use the Born-Oppenheimer molecular dynamics (BOMD) simulations to study solvation and hydrolysis reactions of HNCO on water droplets at ambient temperature. The BOMD simulations indicate that the scavenging of HNCO by water droplets is largely attributed to the preferential adsorption of HNCO at the air-water interface, rather than inside bulk water. Specifically, the H atom of HNCO interacts with the O atom of interfacial water, leading to the formation of a hydrogen bond (H-bond) of (HNCO)H···O(H2O), which prevents HNCO from evaporating. Moreover, the interfacial water can act as H-bond acceptors/donors to promote the proton transfer during the HNCO hydrolysis reaction. Compared to the gas phase, the activation barrier is lowered from 45 to 14 kcal·mol-1 on the water surface, which facilitates the formation of the key intermediate of NH2COOH. This intermediate eventually decomposes into NH3 and CO2, consistent with the previous study [ Atmos. Chem. Phys. 2016, 16, 703-714]. The new molecular insight into HNCO solvation and reaction on the water surface improves our understanding of the uptake of HNCO on aerosols.
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He G, Ma J, Chu B, Hu R, Li H, Gao M, Liu Y, Wang Y, Ma Q, Xie P, Zhang G, Zeng XC, Francisco JS, He H. Generation and release of OH radicals from the reaction of H2O with O2 over soot. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202201638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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68
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Zhang P, Han B, Yang X, Zou Y, Lu X, Liu X, Zhu Y, Wu D, Shen S, Li L, Zhao Y, Francisco JS, Gu M. Revealing the Intrinsic Atomic Structure and Chemistry of Amorphous LiO 2-Containing Products in Li-O 2 Batteries Using Cryogenic Electron Microscopy. J Am Chem Soc 2022; 144:2129-2136. [PMID: 35075901 DOI: 10.1021/jacs.1c10146] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aprotic lithium-oxygen batteries (LOBs) are promising energy storage systems characterized by ultrahigh theoretical energy density. Extensive research has been devoted to this battery technology, yet the detailed operational mechanisms involved, particularly unambiguous identification of various discharge products and their specific distributions, are still unknown or are subjects of controversy. This is partly because of the intrinsic complexity of the battery chemistry but also because of the lack of atomic-level insight into the oxygen electrodes acquired via reliable techniques. In the current study, it is demonstrated that electron beam irradiation could induce crystallization of amorphous discharge products. Cryogenic conditions and a low beam dosage have to be used for reliable transmission electron microscopy (TEM) characterization. High-resolution cryo-TEM and electron energy loss spectroscopy (EELS) analysis of toroidal discharge particles unambiguously identified the discharge products as a dominating amorphous LiO2 phase with only a small amount of nanocrystalline Li2O2 islands dispersed in it. In addition, uniform mixing of carbon-containing byproducts is identified in the discharge particles with cryo-EELS, which leads to a slightly higher charging potential. The discharge products can be reversibly cycled, with no visible residue after full recharge. We believe that the amorphous superoxide dominating discharge particles can lead researchers to reconsider the chemistry of LOBs and pay special attention to exclude beam-induced artifacts in traditional TEM characterizations.
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Qu M, Huang G, Liu X, Nie X, Qi C, Wang H, Hu J, Fang H, Gao Y, Liu WT, Francisco JS, Wang C. Room temperature bilayer water structures on a rutile TiO 2(110) surface: hydrophobic or hydrophilic? Chem Sci 2022; 13:10546-10554. [PMID: 36277652 PMCID: PMC9473646 DOI: 10.1039/d2sc02047e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 08/15/2022] [Indexed: 11/21/2022] Open
Abstract
The lack of understanding of the molecular-scale water adsorbed on TiO2 surfaces under ambient conditions has become a major obstacle for solving the long-time scientific and applications issues, such as the photo-induced wetting phenomenon and designing novel advanced TiO2-based materials. Here, with the molecular dynamics simulation, we identified an ordered water bilayer structure with a two-dimensional hydrogen bonding network on a rutile TiO2(110) surface at ambient temperature, corroborated by vibrational sum-frequency generation spectroscopy. The reduced number of hydrogen bonds between the water bilayer and water droplet results in a notable water contact angle (25 ± 5°) of the pristine TiO2 surface. This surface hydrophobicity can be enhanced by the adsorption of the formate/acetate molecules, and diminishes with dissociated H2O molecules. Our new physical framework well explained the long-time controversy on the origin of the hydrophobicity/hydrophilicity of the TiO2 surface, thus help understanding the efficiency of TiO2 devices in producing electrical energy of solar cells and the photo-oxidation of organic pollutants. An ordered water bilayer structure was identified on a rutile TiO2(110) surface at ambient temperature by combining VSFG experiments and MD simulations, which well explained the long-time controversy on the wetting behaviors of the TiO2 surface.![]()
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Martins-Costa MTC, Anglada JM, Francisco JS, Ruiz-López MF. Photosensitization mechanisms at the air-water interface of aqueous aerosols. Chem Sci 2022; 13:2624-2631. [PMID: 35340860 PMCID: PMC8890110 DOI: 10.1039/d1sc06866k] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 02/04/2022] [Indexed: 11/24/2022] Open
Abstract
Photosensitization reactions are believed to provide a key contribution to the overall oxidation chemistry of the Earth's atmosphere. Generally, these processes take place on the surface of aqueous aerosols, where organic surfactants accumulate and react, either directly or indirectly, with the activated photosensitizer. However, the mechanisms involved in these important interfacial phenomena are still poorly known. This work sheds light on the reaction mechanisms of the photosensitizer imidazole-2-carboxaldehyde through ab initio (QM/MM) molecular dynamics simulations and high-level ab initio calculations. The nature of the lowest excited states of the system (singlets and triplets) is described in detail for the first time in the gas phase, in bulk water, and at the air–water interface, and possible intersystem crossing mechanisms leading to the reactive triplet state are analyzed. Moreover, the reactive triplet state is shown to be unstable at the air–water surface in a pure water aerosol. The combination of this finding with the results obtained for simple surfactant-photosensitizer models, together with experimental data from the literature, suggests that photosensitization reactions assisted by imidazole-2-carboxaldehyde at the surface of aqueous droplets can only occur in the presence of surfactant species, such as fatty acids, that stabilize the photoactivated triplet at the interface. These findings should help the interpretation of field measurements and the design of new laboratory experiments to better understand atmospheric photosensitization processes. First-principles molecular dynamics simulations of imidazole-2-carboxaldehyde at the air–water interface highlight the role of surfactants in stabilising the reactive triplet state involved in photosensitisation reactions in aqueous aerosols.![]()
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Lu B, Trabelsi T, Esposito VJ, Fortenberry RC, Francisco JS, Zeng X. Spectroscopic Characterization of HSO 2• and HOSO • Intermediates Involved in SO 2 Geoengineering. J Phys Chem A 2021; 125:10615-10621. [PMID: 34890193 DOI: 10.1021/acs.jpca.1c09311] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Sulfur-containing radicals HSO2• and HOSO• are key intermediates involved in stratospheric sulfur geoengineering by SO2 injection. The spectroscopic characterization and photochemistry of both radicals are crucial to understanding the chemical impact of SO2 chemistry in the stratosphere. On the basis of the efficient generation of HOSO• by flash pyrolysis of gaseous sulfinic acid, CHF2S(O)OH, a strong absorption is observed at 270 nm along with a shoulder up to 350 nm for HOSO• isolated in low-temperature noble gas matrixes (Ar and Ne). These mainly arise from the excitations from the ground state (X2A) to the C2A/D2A and A2A/B2A states, respectively. Upon a 266 nm laser irradiation, the broad absorption band in the range 320-500 nm for HSO2• appears, and it corresponds to the combination of three excitations from the X2A state to the first (A2A), second (B2A), and third (C2A) excited states. Assignment of the UV-vis spectra is consistent with the photochemistry of HOSO• and HSO2• as observed by matrix-isolation IR spectroscopy and also by the agreement with high-level ab initio calculations.
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Gladich I, Lin C, Sinopoli A, Francisco JS. Uptake and hydration of sulfur dioxide on dry and wet hydroxylated silica surfaces: a computational study. Phys Chem Chem Phys 2021; 24:172-179. [PMID: 34878450 DOI: 10.1039/d1cp04747g] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We present a first-principles molecular dynamics study on the uptake and hydration of sulfur dioxide on the dry and wet fully hydroxylated surfaces of (0001) α-quartz, which are a proxy for suspended silica dust in the atmosphere. The average adsorption energy for SO2 is about -10 kcal mol-1 on both dry and wet surfaces. The adsorption is driven by hydrogen bond formation between SO2 and the interfacial hydroxyl groups (on dry silica), or with water molecules (in the wet case). In the dry system, we report an additional electrostatic interaction between the interfacial hydroxyl oxygen and the sulfur atom, which further stabilizes the adsorbate. On dry silica, the interfacial hydroxyl group coordinates to SO2 yielding a surface bound bisulfite (Si-SO3H) complex. On the wet surface, SO2 reacts with water forming bisulfite (HSO3-), and the latter remains solvated inside the adsorbed water layer. The hydration barrier for sulfur dioxide is 1 kcal mol-1 and 3 kcal mol-1 on dry and wet silica, respectively, while for the backward reaction (i.e., bisulfite to SO2) the barrier is 6 kcal mol-1 on both surfaces. The modest backward barrier rationalizes earlier experimental findings showing no SO2 uptake on silica. These results underline the importance of the surface hydroxylation and/or adsorbed water layers for the SO2 uptake and its hydration on silica. Moreover, the hydration to bisulfite may prevent direct SO2 photochemistry and be an additional source of sulfate; this is especially relevant in atmospheres subject to a high level of suspended mineral dust, intense solar radiation and atmospheric oxidizers.
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Zhu B, Wu Z, Wang L, Lu B, Trabelsi T, Francisco JS, Zeng X. Matrix-isolated trifluoromethylthiyl radical: sulfur atom transfer, isomerization and oxidation reactions. Chem Commun (Camb) 2021; 57:12143-12146. [PMID: 34724519 DOI: 10.1039/d1cc04654c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
By high-vacuum flash pyrolysis of bis(trifluoromethyl)disulfane oxide (CF3S(O)SCF3) at 400 °C, the elusive trifluoromethylthiyl radical (CF3S˙) has been efficiently generated in the gas phase. Subsequent isolation of CF3S˙ in cryogenic matrixes (Ne, Ar, and N2) allows a first time characterization with IR and UV-vis spectroscopy by combining with computations at the CCSD(T)/aug-cc-pV(T + d)Z level. In addition to the photo-induced sulfur atom transfer (SAT) from CF3S˙ to N2 and CO and the isomerization to ˙CF2SF, the O2-oxidation via the intermediacy of the novel thiylperoxy radical CF3SOO˙ has been observed.
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Carmona-García J, Trabelsi T, Francés-Monerris A, Cuevas CA, Saiz-Lopez A, Roca-Sanjuán D, Francisco JS. Photochemistry of HOSO 2 and SO 3 and Implications for the Production of Sulfuric Acid. J Am Chem Soc 2021; 143:18794-18802. [PMID: 34726419 DOI: 10.1021/jacs.1c10153] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Sulfur trioxide (SO3) and the hydroxysulfonyl radical (HOSO2) are two key intermediates in the production of sulfuric acid (H2SO4) on Earth's atmosphere, one of the major components of acid rain. Here, the photochemical properties of these species are determined by means of high-level quantum chemical methodologies, and the potential impact of their light-induced reactivity is assessed within the context of the conventional acid rain generation mechanism. Results reveal that the photodissociation of HOSO2 occurs primarily in the stratosphere through the ejection of hydroxyl radicals (•OH) and sulfur dioxide (SO2). This may decrease the production rate of H2SO4 in atmospheric regions with low O2 concentration. In contrast, the photostability of SO3 under stratospheric conditions suggests that its removal efficiency, still poorly understood, is key to assess the H2SO4 formation in the upper atmosphere.
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Wei B, Fu Z, Legut D, Germann TC, Du S, Zhang H, Francisco JS, Zhang R. Rational Design of Highly Stable and Active MXene-Based Bifunctional ORR/OER Double-Atom Catalysts. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2021; 33:e2102595. [PMID: 34342921 DOI: 10.1002/adma.202102595] [Citation(s) in RCA: 52] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/13/2021] [Indexed: 05/14/2023]
Abstract
Designing highly active and bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts has attracted great interest toward metal-air batteries. Herein, an efficient solution to the search for MXene-based bifunctional catalysts is proposed by introducing non-noble metals such as Fe/Co/Ni at the surfaces. These results indicate that the ultrahigh activities in Ni1/Ni2- and Fe1/Ni2-modified MXene-based double-atom catalysts (DACs) for bifunctional ORR/OER are better than those of well-known unifunctional catalysts with low overpotentials, such as Pt(111) for the ORR and IrO2 (110) for the OER. Strain can profoundly regulate the catalytic activities of MXene-based DACs, providing a novel pathway for tunable catalytic behavior in flexible MXenes. An electrochemical model, based on density functional theory and theoretical polarization curves, is proposed to reveal the underlying mechanisms, in agreement with experimental results. Electronic structure analyses indicate that the excellent catalytic activities in the MXene-based DACs are attributed to the electron-capturing capability and synergistic interactions between Fe/Co/Ni adsorbents and MXene substrate. These findings not only reveal promising candidates for MXene-based bifunctional ORR/OER catalysts but also provide new theoretical insights into rationally designing noble-metal-free bifunctional DACs.
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