Reaction Of Anion Research Articles

A SIFT-MS study of positive and negative ion chemistry of the ortho-, meta- and para-isomers of cymene, cresol, and ethylphenol.

Selected Ion Flow Tube Mass Spectrometry (SIFT-MS) is a soft ionisation technique based on gas phase ion-molecule reaction kinetics for the quantification of trace amounts of volatile organic compound vapours. One of its previous limitations is difficulty in resolving isomers, although this can now be overcome using different reactivities of several available reagent cations and anions (H3O+, NO+, O2+˙, O-˙, OH-, O2-˙, NO2-, NO3-). Thus, the ion-molecule reactions of these eight ions with all isomers of the aromatic compounds cymene, cresol and ethylphenol were studied to explore the possibility of their immediate identification and quantification without chromatographic separation. Rate coefficients and product ion branching ratios determined experimentally for the 72 reactions are reported. DFT calculations of their energetics confirmed the feasibility of the suggested reaction pathways. All positive ion reactions proceeded fast but largely did not discriminate between the isomers. The reactivity of the anions was much more varied. In all cases, OH- reacts by proton transfer forming (M-H); NO2- and NO3- were unreactive. The differences observed for product ion branching ratios can be used to identify isomers approximately.

Size-dependent reactivity of chromium oxide cluster anions (CrO3)1−4O− towards alkanes

The reactivity of chromium oxide cluster anions (CrO3)1−4O− towards low carbon (C1−C4) alkanes has been experimentally investigated at 298 K by employing a homemade ship-lock-type reactor coupled with a time-of-flight mass spectrometer. The results demonstrate that while CrO4− and Cr2O7− clusters could abstract a hydrogen atom from C2H6 and CH4, respectively, Cr3O10− and Cr4O13− clusters were found to be inert towards n-C4H10 within the detection limit. Theoretical results reveal that CrO4− and Cr2O7− clusters possess delocalized chromium-bonded oxygen radicals (Cr−O−·), which rationalizes the hydrogen atom abstraction reactions between (CrO3)1,2O− clusters and alkanes. However, the active sites of (CrO3)3,4O− clusters evolve to peroxide species (O22−), which exhibit inferior activity compared to O−· radicals. The increase of Cr-3d orbital energy driven by the more negative charge around CrOy unit formed via downsizing the cluster size has been proposed to account for favorable reduction of O22− and selective generation of reactive O−· radicals in small-sized (CrO3)1,2O− clusters. This study not only enriches the chemistry of metal-bonded O−· radicals toward alkane activation under mild conditions, but also provides a new insight into the conversion between O22− and O−· radicals over metal oxides.

Excited-state chemistry of the nitromethane anion mediated by the dipole-bound states revealed by photofragment action spectroscopy.

We report the first experimental observation of the excited dipole-bound state (DBS) of the cryogenically cooled nitromethane anion (CH3NO2-), where the excess electron is loosely attached to the singlet or triplet neutral-core. Photofragment and photodetachment action spectra have been employed for the dynamic exploration of Feshbach resonances located even far above the electron detachment threshold, giving excitation profiles from the ground anionic state (D0) to the DBSs which match quite well with the spectral structures of the photoelectron spectra. This indicates that the electron transfer from the nonvalence orbital (of DBS) to the valence orbital (of anion) is mainly responsible for the anionic fragmentation channels, giving strong evidence for that the DBS plays a dynamic doorway-role in the anionic fragmentation reactions. Photofragment action spectra have also been obtained for the anionic clusters of (CH3NO2)2-, (CH3NO2)3-, or (CH3NO2·H2O)-, giving the relative yields of various fragments as a function of the excitation energy for each cluster. The absorption profiles of the anionic clusters exhibit substantial blue-shifts compared to the bare nitromethane anion as their ground states are much stabilized by solvation. The anionic fragmentation pattern varies among different clusters, giving essential clues for the thorough understanding of the whole anionic dynamics such as the dynamic role of the short-lived nonvalence-bound states of the clusters.

Chemical compatibility of polymer binders with a reversible anionic redox reaction in lithia-based cathodes

Chemical compatibility of various polymeric binders and solvents with lithia is investigated for improved cycling stability of lithia-based cathodes.

Theoretical study of the rearrangement reaction in bisorbicillinoid biosynthesis: insights into the molecular mechanisms involved.

Bisorbibutenolide and bisorbicillinolide are polyketide compounds with complex skeletons that are formed by the dimerization of sorbicillin. These compounds have long been of interest, with several reports of their biosynthesis, biological activity, and total synthesis. In this study, we theoretically investigated the detailed biosynthetic mechanism of the rearrangement reaction to form bisorbicillinolide. We showed that the presence of water molecules facilitates the intramolecular aldol reaction, determined the rate-limiting steps, and revealed that a cyclopropane intermediate is formed during the rearrangement process. Although computational chemistry has been widely applied to the carbocation chemistry present in terpene biosynthesis, it has seldom been used to investigate the carbonyl chemistry responsible for polyketide biosynthesis. This study shows that computational chemistry is a useful tool for studying anionic skeletal rearrangement reactions.

Engineering of surface oxygen vacancies in Co-free concentration-gradient Li-rich cathodes for high-capacity batteries

Li-rich layered oxides (LLOs) are the most promising high-capacity materials in the Li-ion batteries owing to their cumulative oxygen anionic and cationic redox reactions. However, irreversible oxygen evolution and transition-metal migration aggravate structural rearrangement and capacity fading. Although Co-containing LLO possesses practical capacity and stability for commercial purposes, it suffers from scarcity, toxicity, and high cost of cobalt. To ameliorate these bottlenecks, we improved the reversibility of anionic and cationic redox in Co-free concentration-gradient LLO by integrating oxygen vacancies and high Ni/Mn ratio on LLO's surface. We found that surface oxygen vacancies suppress oxygen release from the surface, reduce the interfacial resistance that arises from electrolyte decomposition, and increase the ionic diffusion; thereby, enhancing the cathode's capacity. Concentration-gradient LLO cathode with an appropriate Mn/Ni ratio improved cation migration's structural stability and reversibility in the layered and spinel-layered Li-rich materials. As a result, the charge transfer and interfacial resistance decreased during the gradual de-lithiation and Ni redox reaction. The Co-free LLO with surface Mn/Ni∼1.5 delivered a reversible capacity of 250 mAh/g, with 99% capacity retention after 85 cycles at 0.1 C. This work provided a practical approach for resolving the capacity decay of the Co-free LLOs by engineering the cathode/electrolyte interface and structure.

Unveiling the High-valence Oxygen Degradation Across the Delithiated Cathode Surface.

Charge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high-valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X-ray photoelectron spectroscopy (APXPS) on a model LiCoO2 cathode. The mRAS verified that no high-valence oxygen can sustain at cathode surfaces, while APXPS proves that cathode electrolyte interphase (CEI) layer evolves and oxidizes upon oxygen gas contact. This work provides valuable insights into the high-valence oxygen degradation mode across the interface. Oxygen stabilization from surface architecture is proven a prerequisite to the practical development of ARR active cathodes.

Unveiling the High‐valence Oxygen Degradation Across the Delithiated Cathode Surface

AbstractCharge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high‐valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X‐ray photoelectron spectroscopy (APXPS) on a model LiCoO2 cathode. The mRAS verified that no high‐valence oxygen can sustain at cathode surfaces, while APXPS proves that cathode electrolyte interphase (CEI) layer evolves and oxidizes upon oxygen gas contact. This work provides valuable insights into the high‐valence oxygen degradation mode across the interface. Oxygen stabilization from surface architecture is proven a prerequisite to the practical development of ARR active cathodes.

Suppressing the Dynamic Oxygen Evolution of Sodium Layered Cathodes through Synergistic Surface Dielectric Polarization and Bulk Site-Selective Co-Doping.

Utilizing anionic redox activity within layered oxide cathode materials represents a transformational avenue for enabling high-energy-density rechargeable batteries. However, the anionic oxygen redox reaction is often accompanied with irreversible dynamic oxygen evolution, leading to unfavorable structural distortion and thus severe voltage decay and rapid capacity fading. Herein, it is proposed and validated that the dynamic oxygen evolution can be effectively suppressed through the synergistic surface CaTiO3 dielectric coating and bulk site-selective Ca/Ti co-doping for layered Na2/3 Ni1/3 Mn2/3 O2 . The surface dielectric coating layer not only suppresses the surface oxygen release but more importantly inhibits the bulk oxygen migration by creating a reverse electric field through dielectric polarization. Meanwhile, the site-selective doping of oxygen-affinity Ca into Na layers and Ti into transition metal layers effectively stabilizes the bulk oxygen through modulating the O 2p band center and the oxygen migration barrier. Such a strategy also leads to a reversible structural evolution with a low volume change because of the enhanced structural integrality and improved oxygen rigidity. Because of these synergistic advantages, the designed electrode exhibits greatly suppressed voltage decay and capacity fading upon long-term cycling. This study affords a promising strategy for regulating the dynamic oxygen evolution to achieve high-capacity layered cathode materials.

Structural evolution of Na-rich spinel oxides involving anionic redox reaction for Na-ion batteries

Two sodium-rich transition metal (TM) oxides with the same spinel structure, Na2MoO4 and Na2WO4 have been investigated as cathode materials for Na-ion batteries for the first time. Although the oxidation state of TMs in the compounds are already at its highest value of 6+, both of them can be activated by anionic redox reaction during initial charge, as revealed by X-ray photoelectron spectroscopy, to give considerable reversible capacity between 1.2 and 4.7 V. In addition, ex-situ X-ray diffractometry (XRD) shows that both cathode materials undergo insignificant structural evolution during Na extraction/insertion, suggesting that the Mo-O4 and W-O4 tetrahedral framework are stable even when more than 1 Na is removed from the materials. Overall, Na2WO4 shows larger amount of Na extraction/insertion and better cycle stability than Na2MoO4. This is likely due to better structural integrity and better stability of Na2WO4 against oxygen loss from ex-situ XRD and differential electrochemical mass spectrometry results.

Novel bleach activator compounds derived from the reaction of isocyanic acid with selected nucleophiles

AbstractLaundry detergents commonly contain bleach activators that react with the perhydroxy anion produced from perborate or percarbonate anions to form activated peroxy compounds; these enhance bleaching and stain removal capacity especially at lower temperatures, hydrogen peroxide being an inefficient bleach below 60°C. The most commonly used activators are N, N, N′, N′‐tetraacetylethylenediamine (TAED) and sodium nonanoyloxybenzenesulphonate (SNOBS) the former being used across Europe whereas the latter is used widely in the United States and Japan. This research studies the preparation of novel activator compounds which are carbamylated derivatives of selected nucleophiles using either solid or aqueous reactions of nucleophilic carboxylate anions with the highly reactive isocyanic acid entity derived from the acidification of sodium cyanate. The novel activator compounds were then assessed as bleach activators by testing against tea and bilberry‐stained cotton reference fabrics at 40°C in the presence of hydrogen peroxide at pH values ranging from 4 to 10; bleaching efficiency was assessed visually and colorimetrically. Results showed that all of the synthesised compounds were more effective bleach activators across the pH range tested than the standard TAED system.

Titration Mass Spectroscopy (TMS): A Quantitative Analytical Technology for Rechargeable Batteries.

Development of high-energy-density rechargeable battery systems not only needs advanced qualitative characterizations for mechanism exploration but also requires accurate quantification technology to quantitatively elucidate products and fairly assess numerous modification strategies. Herein, as a reliable quantification technology, titration mass spectroscopy (TMS) is developed to accurately quantify O-related anionic redox reactions (Li-O2 battery and nickel-cobalt-manganese (NCM)/Li-rich cathodes), parasitic carbonate deposition and decomposition (derived from air-exposure degradation and electrolyte oxidation), and dead Li0 formation (Li-metal battery and over-discharged graphite anode). TMS technology can harvest key information on products (e.g., quantification of oxidized lattice oxygen and solid electrolyte interphase (SEI)/cathode electrolyte interphase (CEI) components) and guide corresponding design strategy by enhancing understanding of the mechanism (e.g., clearly distinguish the catalytic target of highly oxidative Ni4+ on the NCM cathode). Not limited as a rigid quantification tool for widely known products/mechanisms, TMS technology has been demonstrated as a powerful and versatile tool for the investigations of advanced batteries.

One-step constructed oxygen vacancies and Fe-doping to improve the electrochemical performance of Li-rich Mn-based cathode

Layered Li-rich (LLR) oxide electrodes are expected to be strong contenders for next-generation lithium-ion battery materials. However, irreversible anionic redox reactions during cycling lead to oxygen loss and capacity and voltage fading. Here, One-step synthesis strategy with Fe(NH4)2·(SO4)2 has been proposed to achieve Fe-ion replacement and induce the generation of oxygen vacancies. Oxygen vacancies can inhibit the irreversible O release and alleviate the corrosion of the surface and interior of the material by electrolysis. The doping of Fe ions can further stabilize the structure and improve the cycle stability of the material. Owing to this "one stone two birds" modification strategy, the modified materials exhibit significantly reduced interfacial impedance and enhanced cycling stability. Therefore, compared 183.9 mAh g−1 and 69.78% for the original materials, the discharge-specific capacities of 223.1 mAh g−1 at 1 C (1 C = 250 mA g−1) with 81.8% capacity retentions after 300 cycles for the modified materials. Furthermore, the voltage decay is significantly suppressed to 0.002 V/cycle. This work provides a novel idea for manipulating structural stability to enhance the electrochemical performance of Li-rich materials.

Oxygen redox chemistry in lithium-rich cathode materials for Li-ion batteries: Understanding from atomic structure to nano-engineering

Lithium-rich oxide compounds have been recognized as promising cathode materials for high performance Li-ion batteries, owing to their high specific capacity. However, it remains a great challenge to achieve the fully reversible anionic redox reactions to realize high capacity, high stability, and low voltage hysteresis for lithium-rich cathode materials. Therefore, it is critically important to comprehensively understand and control the anionic redox chemistry of lithium-rich cathode materials, including atomic structure design, and nano-scale materials engineering technologies. Herein, we summarize the recent research progress of lithium-rich cathode materials with a focus on redox chemistry. Particularly, we highlight the oxygen-based redox reactions in lithium-rich metal oxides, with critical views of designing next generation oxygen redox lithium cathode materials. Furthermore, we purposed the most promising strategies for improving the performances of lithium-rich cathode materials with a technology-spectrum from the atomic scale to nano-scale.

NiCo2S4 nano composite structure with high electrochemical performance in band gap

Synthesize NiCo2S4 and its application to find out electrochemical performance of anionic reaction in nano chemistry. Because of binary transition metal sulfide NiCo2S4 are prepared by using a Chemical precipitation to find out anionic movement within the compound. But the electrochemical were used as a conductive network for the NiCo2S4 hexagonal nano plates. Hence hexagonal nano plates have an average crystalline size of the particles 38.34nm and 20.06nm. Nickel and cobalt sulfides with various stoichiometries have been synthesized from Ni(CH3COO)2.2H2O, CoCl2.6H2O with different sulfur precursors using as a direct method. The morphological composite were characterized by (scanning electron microscopy) SEM, XRD (X-ray diffraction), EDX, UV-visible, FTIR spectrum and optical band-gap energy were evaluated. Optical band-gap energies in the range 4.7 eV−5.1 eV were observed.

Role of oxide support in electrocatalytic nitrate reduction on Cu

AbstractThe electrochemical nitrate reduction reaction (NO3RR) has the potential for distributed water treatment and renewable chemical synthesis. Cu is an active monometallic electrocatalyst for the NO3RR in acidic and alkaline electrolytes, where activity is limited by the reduction of adsorbed nitrate to nitrite. Oxygen‐vacancy forming metal‐oxide supports provide sites for N‐O bond activation in thermal reduction, impacting product distribution as well. Here we compare the electrochemical NO3RR activity of Cu deposited on two metal‐oxide supports (cerium dioxide [Cu/CeO2‐δ] and fluorine‐doped tin dioxide [Cu/FTO]) to a Cu foil benchmark. Considering activity in phosphate‐buffered neutral media, nitrate and adsorbed hydrogen compete for surface sites under NO3RR conditions. The less‐cathodic overpotential on Cu/CeO2‐δ compared to Cu/FTO is attributed to stronger nitrate adsorption, similar to thermal nitrate reduction. Utilization of CeO2‐δ as an electrocatalyst support slightly shifting product distribution toward more oxidized products, either by enhancing nitrate affinity or by a more dynamic process involving the formation and healing of oxygen vacancies (𝑣O••). These results suggest supporting catalysts on metal oxides may enhance activity by promoting the adsorption of anionic reactants on cathodic electrocatalysts.

Pharmaceutical Functionalization of Monomeric Ionic Liquid for the Preparation of Ionic Graft Polymer Conjugates

Polymerizable choline-based ionic liquid (IL), i.e., [2-(methacryloyloxy)ethyl]-trimethylammonium (TMAMA/Cl¯), was functionalized by an ion exchange reaction with pharmaceutical anions, i.e., cloxacillin (CLX¯) and fusidate (FUS¯), as the antibacterial agents. The modified biocompatible IL monomers (TMAMA/CLX¯, TMAMA/FUS¯) were copolymerized with methyl methacrylate (MMA) to prepare the graft copolymers (19-50 mol% of TMAMA units) serving as the drug (co)delivery systems. The in vitro drug release, which was driven by the exchange reaction of the pharmaceutical anions to phosphate ones in PBS medium, was observed for 44% of CLX¯ (2.7 μg/mL) and 53% of FUS¯ (3.6 μg/mL) in the single systems. Similar amounts of released drugs were detected for the dual system, i.e., 41% of CLX¯ (2.2 μg/mL) and 33% of FUS¯ (2.0 μg/mL). The investigated drug ionic polymer conjugates were examined for their cytotoxicity by MTT test, showing a low toxic effect against human bronchial epithelial cells (BEAS-2B) and normal human dermal fibroblasts (NHDF) as the normal cell lines. The satisfactory drug contents and the release profiles attained for the well-defined graft polymers with ionically bonded pharmaceuticals in the side chains make them promising drug carriers in both separate and combined drug delivery systems.

Kinetic study of graphene oxide synthesis by electrochemical exfoliation of graphite

A kinetic study of graphene oxide (GO) synthesis using electrochemical exfoliation of graphite in the acidic and alkaline electrolyte has been carried out. The effects of temperature (301–333 K), sulfuric acid concentration (0.3–0.6 M), pH (0.3–11.2), current density (12–40 mA/cm2), and graphite density (1.72–1.92 g/cc) on the rate of GO formation have been examined. The GO exfoliation rate was found to be unaffected by graphite density; therefore, all the kinetic was studied with the graphite density of 1.82 g/cc. The GO exfoliation rate increased with a sulfuric acid concentration in the electrolyte. The temperature was seen to enhance the rate of GO synthesis. The activation energy of GO exfoliation was found to be 33.53 kJ/mol in a temperature range of 301–333 K. Based on the findings the mechanism was proposed and the rate law was deduced.. The surface reaction of anions during intercalation and de-intercalation in the interstices of graphite has been found to be the rate-controlling step. Synthesized GO was characterized with transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The kinetic model has been developed to fit the GO exfoliation rate within a pH range of 0.3–1.1.

Eliminating interfacial O-involving degradation in Li-rich Mn-based cathodes for all-solid-state lithium batteries.

In the pursuit of energy-dense all-solid-state lithium batteries (ASSBs), Li-rich Mn-based oxide (LRMO) cathodes provide an exciting path forward with unexpectedly high capacity, low cost, and excellent processibility. However, the cause for LRMO|solid electrolyte interfacial degradation remains a mystery, hindering the application of LRMO-based ASSBs. Here, we first reveal that the surface oxygen instability of LRMO is the driving force for interfacial degradation, which severely blocks the interfacial Li-ion transport and triggers fast battery failure. By replacing the charge compensation of surface oxygen with sulfite, the overoxidation and interfacial degradation can be effectively prevented, therefore achieving a high specific capacity (~248 mAh g-1, 1.1 mAh cm-2; ~225 mAh g-1, 2.9 mAh cm-2) and excellent long-term cycling stability of >300 cycles with 81.2% capacity retention at room temperature. These findings emphasize the importance of irreversible anion reactions in interfacial failure and provide fresh insights into constructing stable interfaces in LRMO-based ASSBs.

Enabling robust anionic redox structure via tuning the symmetry of locally ordered lattice in Li-rich Li-Mn-O cathodes

Li-rich Li-Mn-O (LR-LMO) oxides are promising cathodes for low-lost and high-energy–density Li-ion batteries owing to their accessible anionic redox reaction (ARR) chemistry. However, the unstable ARR structure can result in inferior electrochemical properties, restricting practical applications of LR-LMO oxides. In this study, we demonstrate that the symmetry of locally ordered lattice can be tuned to enable robust ARR structure in LR-LMO cathodes. By employing a twofold symmetry locally ordered lattice in the LR-LMO oxide (denoted as tLR-LMO), a reversible capacity of 260 mAh/g at 0.1C and capacity retention of 78 % after 100 cycles at 1C were observed. The tLR-LMO has retarded cationic migrations during the ARR process when compared to this with a sixfold symmetry locally ordered lattice (denoted as sLR-LMO), as indicated by in-situ X-ray diffraction and ex-situ scanning transmission electron microscopy studies. The tLR-LMO also shows superior stability in its ARR structure as revealed by ex-situ X-ray absorption spectra and neutron pair distribution function results and supported by theoretical calculations. More broadly, this work highlights the role of local-structure symmetry in designing high-performance Li-rich cathodes with ARR activity.