Catalyst-Free Nitrogen Fixation by Microdroplets through a Radical-Mediated Disproportionation Mechanism under Ambient Conditions.

Nitrogen fixation is essential for the sustainable development of both human society and the environment. Due to the chemical inertness of the N≡N bond, the traditional Haber-Bosch process operates under extreme conditions, making nitrogen fixation under ambient conditions highly desirable but challenging. In this study, we present an ultrasonic atomizing microdroplet method that achieves nitrogen fixation using water and air under ambient conditions in a rationally designed sealed device, without the need for any catalyst.

Spontaneous Generation of Alkoxide Radical from Alcohols on Microdroplets Surface.

Water microdroplets have been demonstrated to exhibit extraordinary chemical behaviors, including the abilities to accelerate chemical reactions by several orders of magnitude and to trigger reactions that cannot occur in bulk water. One of the most striking examples is the spontaneous generation of hydroxyl radical from hydroxide ions. Alcohols and alkoxide ions, being structurally similar to water and hydroxide ions, might exhibit similar behavior on microdroplets.

Neighboring Catalytic Sites Are Essential for Electrochemical Dechlorination of 2-Chlorophenol.

The electrocatalytic reduction process is a promising technology for decomposing chlorinated organic pollutants in water but is limited by the lack of low-cost catalysts that can achieve high activity and selectivity. In studying electrochemical dechlorination of 2-chlorophenol (2-CP) in aqueous media, we find that cobalt phthalocyanine molecules supported on carbon nanotubes (CoPc/CNT), which is a highly effective electrocatalyst for breaking the aliphatic C-Cl bonds in 1,2-dichloroethane (DCA) and trichloroethylene (TCE), are completely inactive for reducing the aromatic C-Cl bond in 2-CP. Detailed mechanistic investigation, including volcano plot correlation between dechlorination rate and atomic hydrogen adsorption energy on various transition metal surfaces, kinetic measurements, in situ Raman spectroscopy, and density functional theory calculations, reveals that the reduction of the aromatic C-Cl bond in 2-CP goes through a hydrodechlorination mechanism featuring a bimolecular reaction between adsorbed atomic hydrogen and 2-CP on the catalyst surface, which requires neighboring catalytic sites, whereas the aliphatic C-Cl bonds in DCA and TCE are cleaved by direct electron transfer from the catalyst, which can occur on isolated single sites.

Barrierless reactions of C2 Criegee intermediates with HSO and their implication to oligomers and new particle formation.

The formation of oligomeric hydrogen peroxide triggered by Criegee intermediate maybe contributes significantly to the formation and growth of secondary organic aerosol (SOA). However, to date, the reactivity of C2 Criegee intermediates (CHCHOO) in areas contaminated with acidic gas remains poorly understood. Herein, high-level quantum chemical calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations are used to explore the reaction of CHCHOO and HSO both in the gas phase and at the air-water interface.

Dynamic-to-static switch of hydrogen bonds induces a metal-insulator transition in an organic-inorganic superlattice.

Hydrogen bonds profoundly influence the fundamental chemical, physical and biological properties of molecules and materials. Owing to their relatively weaker interactions compared to other chemical bonds, hydrogen bonds alone are generally insufficient to induce substantial changes in electrical properties, thus imposing severe constraints on their applications in related devices. Here we report a metal-insulator transition controlled by hydrogen bonds for an organic-inorganic (1,3-diaminopropane)SnSe superlattice that exhibits a colossal on-off ratio of 10 in electrical resistivity.

Mechanistic Insights into NO-Halide Ions Chemistry at the Air-Water Interface.

The activation of halogens (X = Cl, Br, I) by NO is linked to NO sources, ozone concentrations, NO reactivity, and the chemistry of halide-containing aerosol particles. However, a detailed chemical mechanism is still lacking. Herein, we explored the chemistry of the NO···X systems at the air-water interface.

Mechanistic Insights into Chloric Acid Production by Hydrolysis of Chlorine Trioxide at an Air-Water Interface.

Chlorine oxides play crucial roles in ozone depletion, and the final oxidation steps of chlorine oxide potentially result in the formation of chloric acid (HClO) or perchloric acid (HClO). Herein, the solvation and reactive uptake of three stable isomers of chlorine trioxide (ClO), namely, ClOCl(O)O, ClClO, and ClOOOCl, at the air-water interface were investigated using classical and hybrid quantum mechanics/molecular mechanics (QM/MM) molecular dynamics (MD) coupled with advanced free energy methods. Two distinct mechanisms were revealed for the hydrolysis of ClOCl(O)O and ClClO: molecular and ionic mechanisms.

Two-dimensional ice-like water adlayers on a mica surface with and without a graphene coating under ambient conditions.

Water tends to wet all hydrophilic surfaces under ambient conditions, and the first water adlayers on solids are important for a broad range of physicochemical phenomena and technological processes, including corrosion, wetting, lubrication, anti-icing, catalysis, and electrochemistry. Unfortunately, challenges in characterizing the first water adlayer in the laboratory have hampered molecular-level understanding of the contact water structure. Herein, we present the first molecular dynamics simulation evidence of a previously unreported ice-like adlayer structure (named as Ice-AL-II) on a prototype mica surface under ambient conditions.

Tuning hydrogen bond network connectivity in the electric double layer with cations.

Hydrogen bond (H-bond) network connectivity in electric double layers (EDLs) is of paramount importance for interfacial HER/HOR electrocatalytic processes. However, it remains unclear whether the cation-specific effect on H-bond network connectivity in EDLs exists. Herein, we report simulation evidence from molecular dynamics that cations at Pt(111)/water interfaces can tune the structure and the connectivity of H-bond networks in EDLs.

Formation of a two-dimensional helical square tube ice in hydrophobic nanoslit using the TIP5P water model.

In extreme and nanoconfinement conditions, the tetrahedral arrangement of water molecules is challenged, resulting in a rich and new phase behavior unseen in bulk phases. The unique phase behavior of water confined in hydrophobic nanoslits has been previously observed, such as the formation of a variety of two-dimensional (2D) ices below the freezing temperature. The primary identified 2D ice phase, termed square tube ice (STI), represents a unique arrangement of water molecules in 2D ice, which can be viewed as an array of 1D ice nanotubes stacked in the direction parallel to the confinement plane.

The performance of OPC and OPC3 water models in predictions of 2D structures under nanoconfinement.

Nanoconfined water plays an important role in broad fields of science and engineering. Classical molecular dynamics (MD) simulations have been widely used to investigate water phases under nanoconfinement. The key ingredient of MD is the force field.

Growth of millimeter-sized 2D metal iodide crystals induced by ion-specific preference at water-air interfaces.

Conventional liquid-phase methods lack precise control in synthesizing and processing materials with macroscopic sizes and atomic thicknesses. Water interfaces are ubiquitous and unique in catalyzing many chemical reactions. However, investigations on two-dimensional (2D) materials related to water interfaces remain limited.

Mechanistic insight into the competition between interfacial and bulk reactions in microdroplets through NO ammonolysis and hydrolysis.

Reactive uptake of dinitrogen pentaoxide (NO) into aqueous aerosols is a major loss channel for NO in the troposphere; however, a quantitative understanding of the uptake mechanism is lacking. Herein, a computational chemistry strategy is developed employing high-level quantum chemical methods; the method offers detailed molecular insight into the hydrolysis and ammonolysis mechanisms of NO in microdroplets. Specifically, our calculations estimate the bulk and interfacial hydrolysis rates to be (2.

Assisted Self-Assembly of Nanoporous Ices via Carbon Nanomaterial Templates.

Self-assembly is a widely used synthetic method in nanoscience to assemble well-organized structures. Self-assembly processes usually occur in a water solvent environment. However, the self-assembly of water molecules is rarely studied.

Enhanced CO Electroreduction Selectivity toward Ethylene on Pyrazolate-Stabilized Asymmetric Ni-Cu Hybrid Sites.

Metal-organic frameworks (MOFs) possess well-defined, designable structures, holding great potential in enhancing product selectivity for electrochemical CO reduction (COR) through active site engineering. Here, we report a novel MOF catalyst featuring pyrazolate-stabilized asymmetric Ni/Cu sites, which not only maintains structural stability under harsh electrochemical conditions but also exhibits extraordinarily high ethylene (CH) selectivity during COR. At a cathode potential of -1.

Accelerated Photolysis of HO at the Air-Water Interface of a Microdroplet.

Photochemical homolysis of hydrogen peroxide (HO) occurs widely in nature and is a key source of hydroxyl radicals (·OH). The kinetics of HO photolysis play a pivotal role in determining the efficiency of ·OH production, which is currently mainly investigated in bulk systems. Here, we report considerably accelerated HO photolysis at the air-water interface of microdroplets, with a rate 1.

Puckered Zigzag Monolayer Ice: Does a Confined Flat Four-Coordinated Monolayer Ice Always Have a Corresponding Puckered Phase?

We note that a flat, four-coordinated monolayer ice under confinement always has a corresponding puckered phase. Recently, a monolayer ice consisting of an array of zigzag water chains (ZZMI) predicted by first-principles calculations of water under confinement is a flat four-coordinated monolayer ice. Herein, to investigate whether puckered ZZMI exists stably, we perform molecular dynamics simulations of two-dimensional (2D) ice formation for water constrained in graphene nanocapillaries.

Molecular Insights into the Spontaneous Generation of ClO in the Reaction of ClONO and HOCl at the Air-Water Interface.

Chemical processes involving chlorine nitrate (ClONO) at the surface of stratospheric aerosols are crucial to ozone depletion. Herein, we show a reaction route for the formation of ClO, which is a source of stratospheric chlorine, in the ClONO + HOCl reaction at the air-water interface. Our molecular dynamics (AIMD) simulations show that the (ClONO)Cl···O(HOCl) halogen bond plays a key role in the reaction and is the main interaction between ClONO and HOCl both at the air-water interface and in the bulk liquid water.

Spontaneous Oxidation of Thiols and Thioether at the Air-Water Interface of a Sea Spray Microdroplet.

The transport of dissolved organic sulfur, including thiols and thioethers, from the ocean surface to the atmosphere through sea spray aerosol (SSA) is of great importance for the global sulfur cycle. Thiol/thioether in SSA undergoes rapid oxidation that is historically linked to photochemical processes. Here, we report the discovery of a non-photochemical, spontaneous path of thiol/thioether oxidation in SSA.

Water Charge Transfer Accelerates Criegee Intermediate Reaction with HO Radical Anion at the Aqueous Interface.

Criegee intermediates (CIs) are important carbonyl oxides that may react with atmospheric trace chemicals and impact the global climate. The CI reaction with water has been widely studied and is a main channel for trapping CIs in the troposphere. Previous experimental and computational reports have largely focused on reaction kinetic processes in various CI-water reactions.

Excessive Iodine Enabled Ultrathin Inorganic Perovskite Growth at the Liquid-Air Interface.

The liquid-air interface offers a platform for the in-plane growth of free-standing materials. However, it is rarely used for inorganic perovskites and ultrathin non-layered perovskites. Herein the liquid-air interfacial synthesis of inorganic perovskite nanosheets (Cs Bi I , Cs Sb I ) is achieved simply by drop-casting the precursor solution with only the addition of iodine.

Mechanistic Insights into the Reactive Uptake of Chlorine Nitrate at the Air-Water Interface.

It is well-known that the aqueous-phase processing of chlorine nitrate (ClONO) plays a crucial role in ozone depletion. However, many of the physical and chemical properties of ClONO at the air-water interface or in bulk water are unknown or not understood on a microscopic scale. Here, the solvation and hydrolysis of ClONO at the air-water interface and in bulk water at 300 K were investigated by classical and molecular dynamics (AIMD) simulations combined with free energy methods.

Anomalous water transport in narrow-diameter carbon nanotubes.

Carbon nanotubes (CNTs) mimicking the structure of aquaporins support fast water transport, making them strong candidates for building next-generation high-performance membranes for water treatment. The diffusion and transport behavior of water through CNTs or nanoporous graphene can be fundamentally different from those of bulk water through a macroscopic tube. To date, the nanotube-length-dependent physical transport behavior of water is still largely unexplored.