Reaction Of Anion Research Articles

High-Energy Earth-Abundant Cathodes with Enhanced Cationic/Anionic Redox for Sustainable and Long-Lasting Na-Ion Batteries.

Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na0.67Fe0.3Mn0.5Mg0.1Ti0.1O2 cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210mAhg-1 at 20mAg-1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200mAg-1, even when operated with a high charge cut-off voltage of 4.5V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.

On the Mechanism and Quantum Tunneling of the CO2 + OH Anion Reaction in Ice: A Computational Study

On the Mechanism and Quantum Tunneling of the CO₂ + OH Anion Reaction in Ice: A Computational Study

Aptamer and Electrochemical Aptasensor towards Selenate Ions (SeO42-).

Selenium is an essential inorganic compound in human and animal nutrition, involved in the proper functioning of the body. As a micronutrient, it actively contributes to the regulation of various metabolic activities, i.e., thyroid hormone, and protection against oxidative stress. However, Se exhibits a narrow concentration window between having a positive effect and exerting a toxic effect. In higher doses, it negatively affects living organisms and causes DNA damage through the formation of free radicals. Increased reactivity of Se anions can also disrupt the integrity and function of DNA-repairing proteins. As the permissible concentration of Se in drinking water is 10 µg/L, it is vital to develop sensitive and robust methods of Se detection in aqueous samples. In this study, for the first time, we proposed a selective aptamer for selenate ion detection, chosen following the SELEX process, and its application in the construction of an electrochemical aptasensor towards SeO42- ions. Measurement conditions such as the used redox marker and pH value of the measurement solution were chosen. The proposed aptasensor is characterized by good selectivity and an LOD of 1 nM. Conditions for biosensor regeneration and storage were also investigated in this research.

The Self-Assembly of Cationic Metal Complexes on Gold Nanoparticle Surface.

This work aims to study the interaction between cationic metal complexes (M z +) and gold nanoparticles (AuNPs z- ). The M z + complexes were chosen from previous works described in the literature and were synthesized as defined. For example, they are as follows: 1 = [RuCl(dppb)(bipy)(py)](PF6); 2 = [RuCl(dppb)(bipy)(vpy)](PF6); 3 = [RuCl(dppb)(bipy)(mepy)](PF6); 4 = [RuCl(dppb)(bipy)(tbpy)](PF6); 5 = [RuCl2(dppb)(bipy)](PF6); 6 = [Fe(bipy)3]Cl2; 7 = [Ru(bipy)3](PF6)2; 8 = [TPyP{RuCl(dppb)(bipy)}4](PF6)4; and 9 = [RuCl(p-cymene)(Diipmp)](PF6). The interactions between M z + and AuNPs z- were carried out using conductometry and UV-vis spectroscopy. These experiments allowed determination of kinetic parameters, revealing three different steps in the interaction process: induction time, flocculation, and agglomeration. The self-assembly between M z + and AuNPs z- was investigated using three different models of binding site, namely, Langmuir or direct plot, Benesi-Hildebrand, and Scatchard. These models provide the fraction of total binding sites occupied (θ), the formation constant (K f), which is dependent on the temperature and geometric structure of each group of M z +, and the Gibbs free energy of reaction (ΔG r ), which was negative for each pair of M z + and AuNPs z- , revealing a spontaneous agglomeration process. The Hill coefficient (n) was 1 for almost all complexes, indicating that agglomeration is an independent process, except for 5, where n = 2, suggesting a positive propensity to bind onto the AuNPs z- surface. The models have confirmed a noncovalent interaction between these species. The relative error in site binding does not show any variation with changes in the temperature, but a fine-tuning of the n value to 1.00 was observed with the increase of the temperature. Finally, the reduction reaction of the 4-nitrophenolate anion (4-NP-) by NaBH4 catalyzed by AuNPs z- was used in the presence of M z + as an evaluation test to show how the M z + species will disturb the 4-NP- binding site on the surface of gold nanoparticles.

Achieving a Deeply Desodiated Stabilized Cathode Material by the High Entropy Strategy for Sodium-ion Batteries.

Manganese-based layered oxides are currently of significant interest as cathode materials for sodium-ion batteries due to their low toxicity and high specific capacity. However, the practical applications are impeded by sluggish intrinsic Na+ migration and poor structure stability as a result of Jahn-Teller distortion and complicated phase transition. In this study, a high-entropy strategy is proposed to enhance the high-voltage capacity and cycling stability. The designed P2-Na0.67Mn0.6Cu0.08Ni0.09Fe0.18Ti0.05O2 achieves a deeply desodiation and delivers charging capacity of 158.1 mAh g-1 corresponding to 0.61 Na with a high initial Coulombic efficiency of 98.2 %. The charge compensation is attributed to the cationic and anionic redox reactions conjunctively. Moreover, the crystal structure is effectively stabilized, leading to a slight variation of lattice parameters. This research carries implications for the expedited development of low-cost, high-energy-density cathode materials for sodium-ion batteries.

Achieving a Deeply Desodiated Stabilized Cathode Material by the High Entropy Strategy for Sodium‐ion Batteries

AbstractManganese‐based layered oxides are currently of significant interest as cathode materials for sodium‐ion batteries due to their low toxicity and high specific capacity. However, the practical applications are impeded by sluggish intrinsic Na+ migration and poor structure stability as a result of Jahn–Teller distortion and complicated phase transition. In this study, a high‐entropy strategy is proposed to enhance the high‐voltage capacity and cycling stability. The designed P2‐Na0.67Mn0.6Cu0.08Ni0.09Fe0.18Ti0.05O2 achieves a deeply desodiation and delivers charging capacity of 158.1 mAh g−1 corresponding to 0.61 Na with a high initial Coulombic efficiency of 98.2 %. The charge compensation is attributed to the cationic and anionic redox reactions conjunctively. Moreover, the crystal structure is effectively stabilized, leading to a slight variation of lattice parameters. This research carries implications for the expedited development of low‐cost, high‐energy‐density cathode materials for sodium‐ion batteries.

In Situ Formed Organic Ion-Associate Liquid-Phase Microextraction without Centrifugation from Aqueous Solutions Using Thymol Blue and Estrogens

In this study, we present a method for ion-associated liquid phase (IALP) separation and concentration of analytes from an aqueous matrix into an IALP formed in situ by the charge neutralization reaction of organic cations and anions, without centrifugation. The effects of various factors on the extraction efficiency and other parameters are investigated, whereas no instrumental stirring, such as vortexing or ultrasonics, is required because the solvent (IALP) is formed in situ. The organic cation and anion used are ethylhexyloxypropylammonium and dodecyl sulfate, respectively. The developed in situ IALP microextraction method for phase separation without centrifugation is tested using the thymol blue dye and several endocrine disruptors. The tested endocrine disruptors (bisphenol A, 17β-estradiol, 17α-ethinylestradiol, and estrone) are analyzed via high-performance liquid chromatography/fluorescence detection, with respective detection limits of 0.02, 0.02, 0.02, and 0.4 μg L−1, and the corresponding enrichment factor ranging from 47 to 71. This IALP microextraction method can be used to separate and concentrate environmental water samples of different matrices. The employed IALP is fast and easy to use, enables an approximately 100-fold analyte concentration, and has a high affinity for estrogens, thus holding promise for the separation, concentration, and quantitation of diverse trace analytes.

Anti-siting for stabilizing structure and modulating cationic/anionic redox reactions

The layered Mn-rich oxide cathode materials with oxygen redox activity are highly appealing in sodium-ion (Na-ion) batteries because of their high energy density and low cost. However, the applications of such materials are hindered by issues such as low Mn redox potential and irreversible phase transformation. Rational modulation of the ordering of the transition metal (TM) layer can inhibit the constraints and stabilize the anionic redox reactions. Herein we introduce stable Li/Mn anti-siting in the TM layer of P2-type Na0.6Li0.2Mn0.8O2 as a strategy to create abundant Mn sites and O sites that are inequivalent to the counterpart of each in the lattice, and thus to prompt the diverse Mn and O redox. The self-locking of the anti-siting energetically inhibits the P2-O2 phase transformation and the resultant structural degradations. In addition, such modulation activates more Mn in charge compensation at high potentials. As a result, this regulation increases the reversible capacity from 104.2 mAh g−1 to 153.7 mAh g−1 and enhances the cycling stability of Na0.6Li0.2Mn0.8O2. This anti-siting strategy offers a new solution to designing cathode materials with high structural stability and high energy density.

Syntheses of 7a-Substituted Pyrrolizidine Derivatives via Stereocontrolled Anionic Cyclization

AbstractStarting from inexpensive proline and epichlorohydrin, a pivotal stereocontrolled anionic cyclization reaction paves the way for a robust and adaptable methodology to produce stereoisomers of 7a-substituted pyrrolizidine derivatives. This process yields intriguing 7a-hydroxymethyl pyrrolizidine derivatives, among them valuable trans-(2-fluorohexahydro-1H-pyrrolizin-7a-yl)methanol, which is attainable through multiple steps.

Overcoming Electrostatic Interaction via Pulsed Electroreduction for Boosting the Electrocatalytic Urea Synthesis

AbstractElectrocatalytic urea synthesis under ambient conditions offers a promising alternative strategy to the traditional energy‐intensive urea industry protocol. Limited by the electrostatic interaction, the reduction reaction of anions at the cathode in the electrocatalytic system is not easily achievable. Here, we propose a novel strategy to overcome electrostatic interaction via pulsed electroreduction. We found that the reconstruction‐resistant CuSiOx nanotube, with abundant atomic Cu−O−Si interfacial sites, exhibits ultrastability in the electrosynthesis of urea from nitrate and CO2. Under a pulsed potential approach with optimal operating conditions, the Cu−O−Si interfaces achieve a superior urea production rate (1606.1 μg h−1 mgcat.−1) with high selectivity (79.01 %) and stability (the Faradaic efficiency is retained at 80 % even after 80 h of testing), outperforming most reported electrocatalytic synthesis urea catalysts. We believe our strategy will incite further investigation into pulsed electroreduction increasing substrate transport, which may guide the design of ambient urea electrosynthesis and other energy conversion systems.

Overcoming Electrostatic Interaction via Pulsed Electroreduction for Boosting the Electrocatalytic Urea Synthesis.

Electrocatalytic urea synthesis under ambient conditions offers a promising alternative strategy to the traditional energy-intensive urea industry protocol. Limited by the electrostatic interaction, the reduction reaction of anions at the cathode in the electrocatalytic system is not easily achievable. Here, we propose a novel strategy to overcome electrostatic interaction via pulsed electroreduction. We found that the reconstruction-resistant CuSiOx nanotube, with abundant atomic Cu-O-Si interfacial sites, exhibits ultrastability in the electrosynthesis of urea from nitrate and CO2. Under a pulsed potential approach with optimal operating conditions, the Cu-O-Si interfaces achieve a superior urea production rate (1606.1 μg h-1 mgcat. -1) with high selectivity (79.01 %) and stability (the Faradaic efficiency is retained at 80 % even after 80 h of testing), outperforming most reported electrocatalytic synthesis urea catalysts. We believe our strategy will incite further investigation into pulsed electroreduction increasing substrate transport, which may guide the design of ambient urea electrosynthesis and other energy conversion systems.

Perspective on High-Stability Single-Crystal Li-Rich Cathode Materials for Li-Ion Batteries.

Benefiting from anionic and cationic redox reactions, Li-rich materials have been regarded as next-generation cathodes to overcome the bottleneck of energy density. However, they always suffer from cracking of polycrystalline (PC) secondary particles and lattice oxygen release, resulting in severe structural deterioration and capacity decay upon cycling. Single-crystal (SC) design has been proven as an effective strategy to relieve these issues in traditional Li-rich cathodes with PC morphology. Herein, we first reviewed the main synthesis routes of SC Li-rich materials including solid-state reaction, molten salt-assisted, and hydrothermal/solvothermal methods, in which the differences in grain morphology, electrochemical behaviors, and other properties induced by various routes were analyzed and discussed. Furthermore, the distinct characteristics were compared between SC and PC cathodes from the aspects of irreversible capacity, structural stability, capacity/voltage degradation, and gas release. Besides, recent advances in layered SC Li-rich oxide cathodes were summarized in detail, where the unique structural designs and modification strategies could greatly promote their structural/electrochemical stability. At last, challenges and perspectives for the emerging SC Li-rich cathodes were proposed, which provided an exceptional opportunity to achieve high-energy-density and high-stability Li-ion/metal batteries.

Highly efficient anionic ring-opening reactions of epoxide triggered by phosphide

Highly efficient anionic ring-opening reactions of epoxide triggered by phosphide

P2-type layered oxide cathode with honeycomb-ordered superstructure for sodium-ion batteries

Sodium-ion batteries (SIBs) have been proved as one of the most alternative to Lithium-ion batteries (LIBs) by the virtue of the abundant resources of Na. Among the cathodes, layered oxides stand out owing to their high energy density. The Jahn–Teller distortion, structural phase transition and oxygen release are main drawbacks of Mn/Ni based layered oxides. Hence, Li-Ni-Cu co-substituted Na0.67Li0.1(Mn0.7Ni0.2Cu0.1)0.9O2 (NLMNC) sample was prepared. The NLMNC sample exhibits the honeycomb-ordered superstructure at about 22° which is ascribed to cation ordering. By virtue of the Li-Ni-Cu co-substitute, the Jahn–Teller distortion of Mn is suppressed. Attributed to Li+ migrating from the metal oxide layer to the interlayer and the Li+ can play the part of pillar in the interlayer, NLMNC cathode displays the capacity retention rate of 82.5 % at 200 mA g−1 after 100 cycles. The anionic redox reaction of NLMNC is related to the addition of Li ions and O 2p non-bonding which is different from the anionic redox reaction of electrons removing from O 2p in the eg* (Ni–O) states of Na2/3Ni1/3Mn2/3O2. During charge process, peroxo O− emerges with the oxidation of lattice oxygen. During discharge process, the intensity of peroxo O− gradually decreases. DFT calculations were also carried out to reveal the reaction mechanism of NLMNC. The DFT results showed that the anionic redox reaction occurs near Mn ions, while the Ni ions are stable which is corresponding with our results. It is proven that such Li-Ni-Cu co-substituted NLMNC presents a promising cathode material for SIBs.

Proposal and application of a novel isothermal model for the thermodynamic study of ion exchange reactions

Ion exchange is a separation and purification technique widely employed in chemistry, environment and metallurgy. Commonly, the isotherm models used for thermodynamic study are the Langmuir model and the Freundlich model. However, these two models are initially used to study the adsorption of gas molecules onto solids, and there are some limitations if they are applied to ion exchange reactions. In this paper, a novel isotherm model (NIM) for ion exchange reactions was derived based on the process of ion exchange, the principle of electroneutrality and the law of conservation of mass. The NIM was utilized to study the reactions of anions (F-, WO42-, MoO42-, PO43-, AsO43-, MoS2O22-, MoS42-) with chloride-form strongly basic anion exchange resins. Moreover, the reactions of cations (K+, Ca2+) with sodium-form cation exchange resins were also explored. The results indicated that the calculation data based on the NIM matched up well with the experiments, even though the ions have various valences and different affinities for the resin, which proved the reliability of the model. In addition, the compatibility of the NIM with the Langmuir and Freundlich models was theoretically analyzed, and the conclusions were also verified by the experimental data. By contrast, the physical meaning of the parameters involved in the NIM was clear and had a good generality, which can be applicable to various situations of ion exchange reactions. Therefore, the NIM proposed in this work can effectively obtain the thermodynamic parameters of ion exchange reactions, and is expected to provide theoretical basis for the design, optimization and control of ion exchange processes.

Dynamic Anion Enables Self‐Healing Single‐Ion Conductor Polymer Electrolyte for Lithium‐Metal Batteries

AbstractLithium‐metal batteries (LMBs) are regarded as a promising option for high‐energy‐density storage systems. However, lithium dendrite growth in LMBs can damage electrolytes and cause short circuits, which severely limits the practical application of LMBs. It is highly desired to develop an advanced polymer electrolyte with self‐healing capability and the ability to inhibit the growth of lithium dendrites for enhancing safety and prolonging the cycle life of the LMBs. Herein, sp3 boron‐based single‐ion conductor polymer electrolytes (B‐SIPEs) with excellent self‐healing capability and interfacial stability are constructed. The rapid bond exchange reactions of dynamic borate anions enable B‐SIPE to fast self‐heal in mild conditions, with a high self‐healing efficiency of 87% within 30 min at an ambient temperature. In particular, B‐SIPE displays a high Li+ transference number (0.88) and excellent lithium dendrite inhibition ability. The Li|B‐SIPE|Li cells exhibit a stable overpotential over 2000 h without short‐circuit. Additionally, the LiFePO4||Li cells with B‐SIPE exhibit superior long‐term cycling performance, with 93.5% capacity retention for 500 cycles. Significantly, B‐SIPE is capable of self‐healing the fracture in LiFePO4||Li cells and recovering the battery performance. These results demonstrate that the advanced self‐healing single‐ion conductor polymer electrolytes effectively promote the reliability and safety of LMBs.

Imaging the Ion-Molecule Reaction Dynamics of O- + CD4.

While neutral reactions involved in methane oxidation have been intensively studied, much less information is known about the reaction dynamics of the oxygen radical anion with methane. Here, we study the scattering dynamics of this anion-molecule reaction using crossed-beam velocity map imaging with deuterated methane. Differential scattering cross sections for the deuterium abstraction channel have been determined at relative collision energies between 0.2 and 1.5 eV and ab initio calculations of the important stationary points along the reaction pathway have been performed. At lower collision energies, direct backscattering and indirect complex-mediated reaction dynamics are observed, whereas at higher energies, sideways deuterium stripping dominates the reaction. Above 0.7 eV collision energy, a suppressed cross section is observed at low product ion velocities, which is likely caused by the endoergic pathway of combined deuteron/deuterium transfer, forming heavy water. The measured product internal energy is attributed mainly to the low-lying deformation and out-of-plane bending vibrations of the methyl radical product. The results are compared with a previous crossed-beam result for the reaction of oxygen anions with nondeuterated ̧methane and with the related neutral-neutral reactions, showing similar dynamics and qualitative agreement.

Improved Performance of High‐Entropy Disordered Rocksalt Oxyfluoride Cathode by Atomic Layer Deposition Coating for Li‐Ion Batteries

Lithium‐excess cation‐disordered rocksalt materials are a promising class of transition metal‐based cathodes that exhibit high specific capacity and energy density. The exceptional performance is achieved through participation of anionic redox in addition to cationic redox reactions in the electrochemistry. However, anionic redox reactions accompanied by oxygen evolution, accelerated electrolyte breakdown, and structural evolution lead to voltage hysteresis and low initial Coulombic efficiency. Herein, an Al2O3 layer with varying thickness has been coated onto a high‐entropy disordered rocksalt oxyfluoride cathode through atomic layer deposition to enhance battery performance. The results indicate that the utilization of a uniform Al2O3 coating improves the capacity retention and rate capability of the cathode, with the performance being strongly dependent on the layer thickness. Further investigation into cathode–electrolyte interfacial reactions reveals that the thin protecting Al2O3 coating can reduce the decomposition of electrolyte on the cathode surface but cannot prevent bulk phase degradation during prolonged cycling. These findings highlight the need for optimized coating design on the disordered rocksalt cathode to improve battery performance.

Effect of La3+ on the Formation of Endohedral Zintl Clusters Featuring In/Bi Shells.

Investigating the interactions of f-block metal ions with p-block polyanions in multinary cluster compounds is becoming increasingly attractive but remains a challenge in terms of both the synthetic approach and the control of the structures that are formed during the syntheses. So far, two types of reactions were dominant for the formation of corresponding clusters: the reaction of binary anions of p-block elements in 1,2-diamino-ethane (en) solutions or the reaction of organobismuth compounds with corresponding f-block metal complexes in THF. Herein, we report the synthesis of [La@In2Bi11]4- (1) and its doubly μ-Bi-bridged analogue in the doubly [K(crypt-222)]+-coordinated {[K(crypt-222)]2[La@In2Bi11](μ-Bi)2[La@In2Bi11]}4- (2) as their [K(crypt-222)]+ salts [K(crypt-222)]41 and [K(crypt-222)]42, respectively, achieved by reactions of [InMes3] and [La(C5Me4H)3] (Mes = mesityl, C5Me4H = tetramethylcyclopentadienyl) with K10Ga3Bi6.65/crypt-222 (crypt-222 = 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane) in en. In the absence of [La(C5Me4H)3], the otherwise unchanged reactions afford the anions [Bi6(InMes)(InMes2)]3- (3) and [Mes3In-InMes3]2- (4) instead, which can be isolated as their [K(crypt-222)]+ salts [K(crypt-222)]33 and [K(crypt-222)]24·tol (tol = toluene), respectively. The {Bi6} fragment observed in anion 3 is assumed to be one of the key intermediates not only toward the formation of 1 and 2 but also on the way to more general bismuth rich compounds.

Adsorption of Pb (II) ions on variable charge oxidic calcined substrates with chemically modified surface.

The paper describes lead ion adsorption on variable charge oxidic calcined substrates with chemically modified surfaces. Amphoteric oxides of iron, aluminum, titanium, and manganese, change their surface electric charge after acid or alkaline treatment, letting cationic or anionic adsorption reactions from aqueous solutions. This property allows using them as adsorbing substrate for heavy metals retention in water treatment systems. Substrate was prepared by extruding cylindrical strips from a saturate paste of the oxidic lithological material-OLM; dries it up and thermally treated by calcination. The study was performed by triplicated trial, on batch mode, using 2 grams samples of treated with NaOH 0.1N and non-treated substrate. Lead analysis was performed by AAS-GF. Freundlich and Langmuir models were used to fit results. Comparing differential behavior between treated and non-treated substrates showed the variable charge nature of the OLM. Results show L-type isotherms for the adsorption of Pb(II) ions on the activated substrate, suggesting good affinity between Pb(II) ions and OLM's surface. Average value of adsorption capacity ( K) for activated substrate (1791.73±13.06), is around four times greater than the non-activated substrate (491.54±31.97), during the adsorption reaction, 0.35 and 0.26 mmolH + of proton are produced on the activated and non-activated substrate respectively using a 1 mM Pb(II) solution and 72.2 and 15.6 mmolH + using a 10 mM Pb(II) solution. This acidification agrees with the theoretic model of transitional metals chemisorption on amphoteric oxides, present in lithological material used for the preparation of adsorbent substrates, confirming the information given by the L-type isotherms. Results suggest that these variable charge oxidic adsorbent substrate show great potential as an alternative technique for water treatment at small and medium scale using granular filtration system. The easiness and low price make them suitable to apply in rural media where no treating water systems is available.