Zincate Anions Research Articles

Iron and Zinc Metallates Supported on Ion Exchange Resins: Synergistic Catalysts for the Solvent‐free Cyclic Carbonate Synthesis from Epoxides and CO2

Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO2 over the last decade, the search for a robust and cost‐effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO2 with high efficiency and low cost. Two polystyrene‐based anion exchange resins, AmberlystTM A26‐Cl (A26‐Cl) and AmberliteTM IRA‐400‐Cl (IRA400‐Cl), were compared. The results demonstrated the catalysts' remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco‐friendly method for cyclic carbonate production using waste CO2. A Design of Experiment approach was implemented to optimize the catalytic cycloaddition of CO2. The reaction scale‐up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost‐effective, scalable method for converting CO2 into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates.

Study on the mechanisms of retardation of cement hydration by zinc and acceleration of hardening by sodium aluminate from crystallographic phase analysis

AbstractZinc was focused on as an element causing hardening retardation due to delayed hydration of Ordinary Portland Cement (OPC), and its hardening inhibitory effect and the mechanism of hardening enhancement by sodium aluminate were analyzed by X-ray diffraction and scanning electron microscopy/energy dispersive X-ray spectroscopy. The addition of zinc hydroxide retarded hardening at more than 0.3 mass%, as previously reported, and zinc produced calcium zincate hydrates (qatranaite) and inhibited the hydration of tricalcium silicate (C3S), the main component of hydration of OPC. After the zinc had been fully consumed in qatranaite formation, C3S started normal hydration. The addition of sodium aluminate caused earlier re-hydration of C3S, which was inhibited by hydration, as the hydrates produced appeared to consume zincate anions. The rapid setting effect of sodium aluminate addition was also delayed by zinc hydroxide, but it was estimated that the addition of the same amount of zinc would ensure initial strength through early formation of hydrocalumite. In the longer term, strength was considered to be more enhanced by the onset of C3S hydration.

Superhalide-Anion-Motivator Reforming-Enabled Bipolar Manipulation toward Longevous Energy-Type Zn||Chalcogen Batteries.

Neutrophilic superhalide-anion-triggered chalcogen conversion-based Zn batteries, despite latent high-energy merit, usually suffer from a short lifespan caused by dendrite growth and shuttle effect. Here, a superhalide-anion-motivator reforming strategy is initiated to simultaneously manipulate the anode interface and Se conversion intermediates, realizing a bipolar regulation toward longevous energy-type Zn batteries. With ZnF2 chaotropic additives, the original large-radii superhalide zincate anion species in ionic liquid (IL) electrolytes are split into small F-containing species, boosting the formation of robust solid electrolyte interphases (SEI) for Zn dendrite inhibition. Simultaneously, ion radius reduced multiple F-containing Se conversion intermediates form, enhancing the interion interaction of charged products to suppress the shuttle effect. Consequently, Zn||Se batteries deliver a ca. 20-fold prolonged lifespan (2000 cycles) at 1 A g-1 and high energy/power density of 416.7 Wh kgSe-1/1.89 kW kgSe-1, outperforming those in F-free counterparts. Pouch cells with distinct plateaus and durable cyclability further substantiate the practicality of this design.

C versus O Protonation in Zincate Anions: A Simple Gas-Phase Model for the Surprising Kinetic Stability of Organometallics.

For better understanding the intrinsic reactivity of organozinc reagents, we have examined the protolysis of the isolated zincate ions Et3 Zn- , Et2 Zn(OH)- , and Et2 Zn(OH)2 Li- by 2,2,2-trifluoroethanol in the gas phase. The protonation of the hydroxy groups and the release of water proceed much more efficiently than the protonation of the ethyl groups and the liberation of ethane. Quantum-chemical computations and statistical-rate theory calculations fully reproduce the experimental findings and attribute the lower reactivity of the more basic ethyl moiety to higher intrinsic barriers, which override the thermodynamic preference for its protonation. Thus, our minimalistic gas-phase model provides evidence for the intrinsically low reactivity of organozinc reagents toward proton donors and helps to explain their remarkable kinetic stability against moisture and even protic media.

Electrochemical Evaluation of the Application of Hydrogel Electrolytes to Rechargeable Zn|MnO2 Alkaline Batteries

Zinc-manganese dioxide (Zn|MnO2) alkaline batteries have been widely studied as the active materials exhibit high theoretical capacities (820 mAh/g for Zn and 620 mAh/g for MnO2), low cost, and are inherent safety. Furthermore, the active materials are electrochemically active in aqueous alkaline electrolytes, such as potassium hydroxide (KOH), which is beneficial from a cost and safety perspective. It is widely known that one of the issues with this system is active MnO2 poisoning by zincate anions during the 2nd electron reaction of MnO2. As a result, an electrochemically inert material, ZnMn2O4 (hetaerolite), is formed, which reduces the capacity and cycle life of Zn|MnO2 batteries. Another issue is associated with high depth-of-discharge (DOD) of each material. For example, at high DOD, Zn will undergo shape change, dendritic growth and passivation, while MnO2 will form inactive phases like Mn3O4. Therefore, the 1st electron reaction range of MnO2 is normally accessed in rechargeable Zn|MnO2 batteries with low DOD.We have observed that the use of alkaline-based hydrogel electrolytes can significantly increase the cycle life of Zn|MnO2 batteries. Large-scale Zn|MnO2 cells were tested with either hydrogel or conventional alkaline electrolytes, whose nameplate capacities were 95 Ah based on the 1st electron capacity of MnO2. The hydrogel electrolytes were formed by mixing KOH solution, acrylic acid, and potassium persulfate solution as an initiator. Galvanostatic tests were carried out at cycling rates of C/20 (4.75 A) with 20% DOD of the capacity (19 Ah). The single full discharge performance to 0 V with hydrogels was compared to that with KOH aqueous electrolytes. The cell with the KOH electrolyte showed two sigmoidal curves, which means that two steps of electrochemical reactions were undergone, achieving 131 Ah. After recharging it, the single full discharge was conducted again, but nevertheless it attained less than 4 Ah to 1 V onwards. On the contrary, the cell with the hydrogel presented one sigmoidal curve with 40 Ah to 0 V, and it was continuously able to extract discharge capacities ≥28 Ah to 1 V during 40 cycles. Thus, the hydrogel electrolytes significantly enhanced the electrochemical performance of Zn|MnO2 cells, compared to conventional KOH electrolytes, the reasons for which will be discussed. The results suggest that hydrogels could help preserve active materials without the aforementioned issues and make rechargeable Zn|MnO2 batteries achieve better performance while accessing the 1st electron reaction of MnO2.

Application of Anomalous X-ray Scattering Method to Liquid Electrolytes Used in a Battery: Local Structural Analysis around a Dilute Metallic Ion.

In liquid electrolytes used for a battery, various metal complexes are formed as a result of ion-solvent and ion-ion interactions, which strongly influence the properties of the electrolyte and thus the performance of the battery. Therefore, the structural characterization of such complexes is of great importance. In this study, the anomalous X-ray scattering (AXS) technique was applied to the potassium hydroxide solution including ∼0.3 mol % zinc, which is widely used in various batteries such as the alkaline battery. In spite of the small amount of the metallic ions, we have successfully extracted a local structure around zinc after careful data analysis. The obtained pair distribution function exhibited not only the short-range correlation corresponding to the Zn-O bond within the zincate anion but also a medium-range correlation above 3.5 Å. The present study demonstrates the capability of the AXS technique to detect local structures around dilute metallic ions in liquid electrolytes, which will largely extend the applicable range of this technique, especially to the field related to batteries.

Synthesis and Structural Studies of Three‐Dimensional Supramolecular Motifs Derived from Neutral and Cationic Zinc Alkanesulfonates

AbstractInvited for the cover of this issue is the group of Ravi Shankar from the Indian Institute of Technology Delhi, India, in collaboration with the group of Kieran C. Molloy from the University of Bath, UK. The cover image shows the potential of zincate anions bearing weakly coordinating alkanesulfonate groups as synthons for three‐dimensional supramolecular assemblies.

Binary Polyazides of Zinc

Herein, we report on the synthesis, isolation and comprehensive characterization (M.p., ATR-IR/Raman, elemental analysis, 14N NMR) of tetraazido zincate anions [Zn(N3)4]2− in a series of [Ph4P]+ and [PNP]+ (PNP = bis(triphenylphosphine)iminium) salts. The phase polymorphism in [Ph4P]2[Zn(N3)4] was investigated by temperature dependent Raman, powder and single crystal X-ray diffraction experiments, which indicate the occurrence of five room-temperature stable, and one common high-temperature phase, besides two polymorphs of the acetonitrile solvate [Ph4P]2[Zn(N3)4] · MeCN. Moreover, the synthesis of zinc azide solvates Zn(N3)2 · n solvent (solvent = DMSO, n = 1, 3/2, 3; MeCN, n = 2/3) is presented for the first time. Single crystal X-ray structures of all new compounds were determined. For a better understanding of structure and bonding in E(N3)2, [E(N3)3]− and [E(N3)4]2− (E = Zn, Cd, Hg), theoretical calculations at the M06-2X/aug-cc-pVDZ level were carried out.

Zinc Electrodes in Water-Organics Electrolytes: In Situ Analysis of Suppressed Shape Change

Introduction Zinc-based secondary batteries are promising power sources as inexpensive and high energy density systems, however, they have not fully been established due to the insufficient lifetime of the zinc electrode, mainly caused by the dendrite growth and shape change [1]. To elucidate how the deterioration proceeds, many trials have been made. We have employed operando X-ray diffraction (XRD) [2] and X-ray fluorescence (XRF) imaging [3] to find that the zinc species formed during discharging is dissolved in the electrolyte at least for several minutes before it is precipitated as ZnO even if the electrolyte is preliminarily saturated with ZnO, implying supersaturation of the zinc species. Such dissolved zinc species can induce undesirable morphology change during cycling to cause deterioration. To suppress the dissolution of the zinc species, we have proposed water activity control by using hydrophilic organic compounds dissolved in the alkaline electrolyte [4]. Namely, the formation of the soluble zincate anions Zn(OH)4 2- formed by the electrochemical reaction (1) can be suppressed by moving the equilibrium in the chemical reaction (2) to the right hand side if the water activity is decreased. It has been shown that the addition of the organic compounds decrease the vapor pressure (water activity) and ZnO solubility, leading to long lifetime of the zinc electrode without dendrite growth.Zn + 4OH- = Zn(OH)4 2- + 2e- (1) Zn(OH)4 2- = ZnO + H2O + 2OH- (2) In this study we examine in situ X-ray diffraction (XRD) mapping to show how the addition of the organic compound affects the shape change behavior of the zinc electrode. Experimental Porous ZnO composite electrodes were formed on the copper current collectors and were sandwiched by two NiOOH counter electrodes, inserted with non-woven separators in the experimental cells. They were cycled with 50% utilization in aqueous KOH solutions saturated with ZnO. Organic compounds were occasionally added to the electrolyte. Attention was paid to undesirable oxidation of the organic compound at the counter electrode not to occur. The ZnO and metallic zinc distribution in the zinc electrode of a rectangle shape was evaluated in a non-destructive manner by XRD mapping with ca. 900 pixels per electrode in a transmission mode at synchrotron beamline BL28XU, SPring-8 (Hyogo, Japan). Such non-destructive analysis can prevent undesirable composition changes (metallic zinc oxidation) that can occur when the electrode is exposed to air. Results and Discussion The addition of the organic compound in the alkaline electrolyte was proved by enhance cycle performance. The porosity of the ZnO composite electrode was maintained when the organic compound was added, suggesting that ZnO oxidation and reduction take place without morphology changes. The formation of metallic zinc and ZnO on reduction and oxidation of the zinc electrode, respectively, was monitored by the XRD mapping. On reduction, it was found that metallic zinc was preferentially formed at the periphery of the rectangle. This is probably because of good supply of ions and electrons there. On the other hand, ZnO growth was observed mainly in the center of the electrode, typical of shape change. If metallic zinc formed at the periphery of the electrode is oxidized on the spot, such shape change is unlikely to occur. This implies that zinc transportation through the electrolyte results in the shape change. The shape change can lead to the formation of inactive ZnO in the center of the electrode with insufficient electrical contact with the current collector and finally to the capacity loss.The shape change was suppressed with the addition of the organic compound in the electrolyte; more uniform formation of metallic zinc and ZnO was observed. It is thus expected that the organic compound reducing the water activity contributes to suppression of the zinc dissolution and fixation of the zinc species at the electrode for better rechargeability. Acknowledgment This work was supported by RISING of NEDO. Reference [1] F.R. McLarnon and E.J. Cairns, J. Electrochem. Soc., 138, 645-664 (1991).[2] A. Nakata et al., Electrochim. Acta, 166, 82-87 (2015).[3] A. Nakata et al., Electrochemistry, 83, 849-851 (2015).[4] A. Nakata et al., J. Electrochem. Soc., 163, A50-A56 (2016).

Revisiting Zinc Air Batteries: Solutions for Longer Lifetime

1. Introduction Zinc air batteries are safe and inexpensive aqueous systems with a high theoretical energy density of 1350 Wh/kg (based on zinc mass). The primary zinc air cells have been long used as power sources for hearing aid. Attemps have been made for more than 40 years to use them as electrically rechargeable (secondary) systems, however, the insufficient lifetime of both zinc and air electrodes are still unsolved issues. Recent progress on the air electrode shows promise for better rechargeability. This study focuses on the improvement of the zinc electrode cyclability to show the possibility of “beyond lithium ion batteries”. 2. Results and Discussion Morphology changes such as dendrite formation and shape changes have been indicated as the primary origin of zinc electrode deterioration [1]. Here we apply synchrotron-beam assisted analytical methods, which are currently used for lithium ion systems, to the zinc electrode system to clarify the underlying mechanism. Operando X-ray diffraction [2] and operando X-ray fluorescence imaging [3] suggests that the soluble zincate is the origin of the morphology changes. Namely, zincate anions Zn(OH)4 2-formed by the electrochemical reaction (1) diffuse away from the electrode during discharging before they are decomposed by the following chemical reaction (2) to form the final product zinc oxide ZnO. Zn + 4OH- = Zn(OH)4 2-+ 2e- (1) Zn(OH)4 2- = ZnO + H2O+ 2OH- (2) To restrict the zinc solubility by moving the equilibrium of reaction (2) to the right hand side, H2O activity control was applied by adding organic solvents in alkaline electrolytes [4]. The effect of propylene glycol (PG) was intensively examined as follows. Figures 1(a) and 1(b) show that the addition of PG effectively limits the thermodynamic solubility of ZnO and also kinetically assists the decomposition of supersaturated zinc species in the alkaline solution. The zinc electrode with PG mixed solvents exhibited long cycle life as shown in Fig. 1(c) at a high zinc utilization rate of 75%, revealing the possibility of attaining both long cycle life and high energy density. The vulnerability of PG to oxidation at the air electrode can be evaded by using organic solvents with higher molecular weights. In addition, surface coating of the zinc particles are also effective in enhancing the rechargeability, owing to the zinc oxidation/reduction processes inside the shell of the coat. Acknowledgment This work was supported by the Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING) project of NEDO (Japan).

Coordination of lanthanides in the inverted cucurbituril supramolecular assemblies formed in the presence of tetrachloride zincate anion: Potential applications for isolation of lighter lanthanides

Coordination of supramolecular assemblies was investigated by reacting a series of lanthanide cations (Ln3+) with an inverted cucurbituril (iQ[6]) in the presence of tetrachloride zincate anion [ZnCl4]2−, as an structure directing agent in aqueous HCl (3.0mol/L). Single crystal X-ray diffraction analysis revealed that the coordination of iQ[6] with Ln3+ gave rise to different interaction products and isomorphous groups with increasing atomic number. The interaction of iQ[6] with La3+ and Ce3+ immediately yielded precipitations and single crystal solids containing Pr3+ and Nd3+. No solids resulted from coordination of iQ[6] with Sm3+ and Eu3+, whereas single crystals solids were obtained from coordination of iQ[6] with heavy Ln3+, such as Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+ and Lu3+. Such coordination characteristics may offer a strategy for isolating a series of Ln3+ cations in patches.

Crystal structure of trans-di-fluoridotetra-kis(pyridine-κN)chromium(III) tri-chlorido-(pyridine-κN)zincate monohydrate from synchrotron data.

In the asymmetric unit of the title compound, [CrF2(C5H5N)4][ZnCl3(C5H5N)]·H2O, there are two independent complex cations, one tri-chlorido-(pyridine-κN)zincate anion and one solvent water mol-ecule. The cations lie on inversion centers. The Cr(III) ions are coordinated by four pyridine (py) N atoms in the equatorial plane and two F atoms in a trans axial arrangement, displaying a slightly distorted octa-hedral geometry. The Cr-N(py) bond lengths are in the range 2.0873 (14) to 2.0926 (17) Å while the Cr-F bond lengths are 1.8609 (10) and 1.8645 (10) Å. The [ZnCl3(C5H5N)](-) anion has a distorted tetra-hedral geometry. The Cl atoms of the anion were refined as disordered over two sets of sites in a 0.631 (9):0.369 (9) ratio. In the crystal, two anions and two water mol-ecules are linked via O-H⋯Cl hydrogen bonds, forming centrosymmetric aggregates. In addition, weak C-H⋯Cl, C-H⋯π and π-π stacking inter-actions [centroid-centroid distances = 3.712 (2) and 3.780 (2)Å] link the components of the structure into a three-dimensional network.

1,8-Diazabicyclo[5.4.0]undec-7-en-8-ium bromido(phthalocyaninato)zincate

The title compound, (C9H17N2)[ZnBr(C32H16N8)], contains a bromido­(phthalocyaninato)zincate anion and a protonated 1,8-di­aza­bicyclo­[5.4.0]undece-7-ene cation, [DBUH]+. The central ZnII atom has a distorted square-pyramidal geometry, with four iso­indole N atoms of the macrocycle in equatorial positions and a bromide ion in the axial position. The latter has a relatively high displacement parameter, but no evidence for disorder was obtained. The central ZnII atom is displaced by 0.488 (3) Å from the mean plane defined by the four iso­indole N atoms. The [DBUH]+ cation is involved in an almost linear N—H⋯Br hydrogen bond. In the crystal, π–π inter­actions lead to a relatively short distance of 3.366 (3) Å between the phthalocyaninate rings.

Assembly of ethylzincate compounds into supramolecular structures

Sodium and potassium triethylzincate were isolated by Wanklyn in 1858, and are corner stones in the history of organometallic chemistry. Crystallisation of organozincates from neat dialkylzinc, in the absence of a coordinating solvent, can be expected to result in assembly of supramolecular structures, rather than formation of discrete molecules in the crystalline state. This inspired us to reinvestigate Wanklyn’s classical compounds. Crystallisation of sodium triethylzincate from benzene led to metallation of benzene and the formation of diethylphenylzincate anions. The compound is a two-dimensional network where Na + ions link the zincate anions by coordination to both ethyl- and phenyl groups. We have also, accidently, isolated crystals of the two-dimensional coordination network [K 2(ZnEt 2) 4O] n, displaying a rare oxo-centred core with an octahedral oxide ion surrounded by four zinc atoms and two potassium atoms.

Bis[(4-chlorobenzyl)triphenylphosphonium] tetrachloridozincate(II) trihydrate

The crystal structure of the title compound, (C25H21ClP)2[ZnCl4]·3H2O, consists of tetra­hedral phosphonium cations and tetra­hedral zincate anions; the water mol­ecules form weak hydrogen bonds to the anions. Two of the water mol­ecules are disordered over three sites in a 0.68:0.55:0.77 ratio.

Structurally Defined Reactions of Sodium TMP–Zincate with Nitrile Compounds: Synthesis of a Salt‐Like Sodium Sodiumdizincate and Other Unexpected Ion‐Pair Products

Zany zincation: Seemingly simple zincation reactions of aromatic or aliphatic nitriles are in reality highly complicated affairs involving separated ion pairs (see X-ray structure; yellow Na, blue N, green Zn; left cation, right anion) or joined ion pairs. The results also show that the free zincate anions can engage in complicated dismutation processes.

Sonochemical Fabrication and Electrochemical Performance of Electrode Materials Containing Rare Earth Yttrium

In order to improve the electrochemical performance of zinc electrodes in alkaline batteries, several sonochemically modified zinc powders were successfully prepared in different concentrations of Y(NO3)3 solutions by means of ultrasonic immersion. Moreover, the formation of Y(OH)3/Y2O3 on modified zinc powder, the corrosion inhibition and cyclic performance of corresponding zinc electrodes were investigated through scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical and other techniques. The results showed that Y(OH)3/Y2O3 particles were uniformly distributed on sonochemically modified zinc powder with 0.036 mol·L-1 Y(NO3)3 solution. Simultaneously, the yttrium compounds grew preferentially on the defect sites of zinc powder surface, and prevented the dissolution and diffusion of zincate anions into alkaline electrolyte during the electrochemical process. All these results contributed to the facts that the inhibition efficiency of zinc electrode achieved 79.6%, and differential value between anodic and cathodic peak potentials decreased by 285 mV at the 20th cyclic voltammogram. Simulated silver-zinc batteries were assembled using bare zinc powder and the zinc powder modified with 0.036 mol·L-1 Y(NO3)3 solution. According to the detections of the batteries at a high discharge current density of 250 mA·cm-2, capacity loss of zinc electrode containing the modified zinc powder reached only 62.7 mAh·g-1 from the 1st to 30th cycles, and discharge capacity of 322.6 mAh·g-1 was still reserved after 50 cycles. Therefore, a conclusion was drawn that discharge capacity and cycle life of zinc electrodes were obviously enhanced owing to the application of sonochemically modified zinc powder.

Bis(tetraphenylphosphonium) bis(2-oxo-1,3-dithiole-4,5-dithiolato)zincate(II)

The asymmetric unit of the title compound, (Ph4P)[Zn(C3OS4)2], comprises six crystallographically independent entities, viz. two zincate anions and four counter-cations. Only the complex anions are of interest, noting in particular the tetrahedral coordination of the Zn atoms distorted primarily by the bite angles and asymmetric chelation of the ligands, and the non-linear nature of and departures from planarity in the anions themselves.

Synthesis and Structure of a Dimeric Alkyldibariumtriszincate with a Tetraanionic Triszincate Ligand and a Unique Central Ba4 Zn2 C6 Moiety.

Transmetalations of zincates succeed only after activation of the barium metal. Dialkylbarium, the initial product, metalates the zincate anions which are still present in solution and leads to the formation of tetraanionic tris(zincate) ligands, which sterically shield the Ba-C bonds of a Ba4 Zn2 C6 cage.

`Atomic' X-ray absorption fine structure: a new tool for examining electronic and ionic polarization effects

The Zn K-edge X-ray absorption fine structure (XAFS) of Zn(OH) 4 2− ions in basic solution are analyzed. Atomic XAFS (AXAFS) arises from photoelectron scattering off electrons in bonds on the periphery of the absorber. Interactions of the zincate ion with hydrated cations (H 2O) n M + (M=Li +, Na +, K +, and Rb +) are shown to produce significant changes in the AXAFS intensity that result from polarization of the zincate anion by the cation. Both the `through space field' and `through bond inductive' polarization mechanisms are considered; with the inductive mechanism found to dominate in this case.