Arrangement Of Ions Research Articles

High-Coercivity Ferrimagnet Co₂FeO₂BO₃: XMCD Insights into Charge-Ordering and Cation Distribution

The multi-sublattice ferrimagnet Co2FeO2BO3, a prominent example of lanthanide-free magnets, was the subject of element-selective studies using X-ray magnetic circular dichroism (XMCD) observations at the L- and K- X-ray absorption edges. Research findings indicate that the distinct magnetic characteristics of Co2FeO2BO3, namely its remarkable high coercivity (which surpasses 7 Tesla at low temperatures), originate from an atypical arrangement of magnetic ions in the crystal structure (sp.gr. Pbam). The antiferromagnetic nature of the Co2+-O-Fe3+ exchange interaction was confirmed by identifying the spin and orbital contributions to the total magnetization from Co (mL = 0.27 ± 0.1 μB/ion and meffS = 0.53 ± 0.1 μB/ion) and Fe (mL = 0.05 ± 0.1 μB/ion and meffS = 0.80 ± 0.1 μB/ion) ions through element-selective XMCD analysis. Additionally, the research explicitly revealed that the strong magnetic anisotropy is a result of the significant unquenched orbital magnetic moment of Co, a feature that is also present in the related compound Co3O2BO3. A complex magnetic structure in Co2FeO2BO3, with infinite Co²⁺O6 layers in the bc-plane and strong antiferromagnetic coupling through Fe3⁺ ions, is suggested by element-selective hysteresis data, which revealed that Co²⁺ ions contribute both antiferromagnetic and ferromagnetic components to the total magnetization. The findings underline the suitability of Co2FeO2BO3 for applications in extreme environments, such as low temperatures and high magnetic fields, where its unique magnetic topology and anisotropy can be harnessed for advanced technologies, including materials for space exploration and quantum devices. This XMCD study opens the door to the production of novel high-coercivity, lanthanide-free magnetic materials by showing that targeted substitution at specific crystallographic sites can significantly enhance the magnetic properties of such materials.

An Atomistic Analysis of the Carpet Growth of KCl Across Step Edges on the Ag(111) Surface.

The carpet growth of alkali halide (AH) layers across step edges of substrates enables the growth of seamless and continuous large domains. Yet, information about how the AH layer adapts continuously to the height difference between the terraces on the two sides of a step is only described by continuum models, which do not give details of the ionic displacements. Here, we present a first study of thin epitaxial KCl(100) layers grown on the Ag(111) surface by scanning tunneling microscopy that provides atomistic details for the first time. Measurements were performed at room temperature. Using a Cl--decorated tip, we resolved the ionic arrangement and hence the KCl lattice distortion in the carpet growth region, in some cases even by imaging both types of ions. Our findings demonstrate the ability of the KCl lattice to distort locally over a short distance of four KCl unit cells as a result of the attractive interaction between the ions and the Ag atoms at and close to the steps. For Ag step edges covered by the KCl carpet, we observe a tendency to straighten along the ⟨110⟩ direction of the KCl layer. In addition, the carpet growth induces the formation of Ag microterraces, i.e., the splitting of higher Ag steps into multiple Ag steps of monatomic height during the KCl deposition at elevated temperatures. These microterraces have a minimum width determined by an energetically preferred fitting to the KCl lattice and allow for the carpet growth, while growth across higher Ag steps is not observed.

Microstructural Analysis of Inversion Degree in Sol-Gel Synthesized Spinel MnCo2O4 Particles

Spinel-type compounds exhibit versatile structural and functional properties, which stems from the unique cation distribution that spans a spectrum from partial to total cell inversion degrees.In this study, we investigated the preparation of MnCo₂O₄ particles synthesized via a modified sol-gel method. The synthesized particles were thoroughly characterized using X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and Rietveld refinements to assess their microstructural properties. The impact of different annealing temperatures (1000, 1100, and 1200 °C) and durations (1 and 8 hours) on the crystal evolution of the synthesized particles was systematically investigated to assess the structural adaptability of the MnCo₂O₄ spinel under these synthesis conditions. The degree of inversion and oxygen positional parameters within the crystalline systems were quantified using the Bertaut method to obtain the specific arrangement of manganese and cobalt ions for inversion degrees from approximately 0.85 (random) to 1.00 (inversion) with the presence of a secondary phase of Co3O4 (20 wt%). The lattice parameter was determined from Rietveld analysis to be 8.2720 and 8.2927 Å for the normal and inverted spinel, respectively. Finally, the I(220)/I(400) and I(400)/I(422) intensity ratios were identified as reliable indicators of inversion degree, with these intensities ratios significantly influenced by the oxygen positional parameter.

Analysis of Crystal Structure and Phase Transition of Partially Cation Substituted SrFeO3- δ

Transformation of ordered arrangement of oxide ion vacancies in solid oxides to random one is one of the probable methods for development of new oxide ion or mixed conductor. The crystal structures of SrFeO2.875 and SrFeO2.75 at room temperature are tetragonal and orthorhombic distorted perovskite, respectively, with ordered oxide ion vacancies. In this work, partial cation substitution to SrFeO3-δ was examined as a method to transform the crystal structure to cubic perovskite with random distribution of oxide ion vacancies.Two kinds of cations were examined as substituents. One was trivalent ions such as Y and lanthanoid (Ln). The other was Ca2+ or Ba2+ for controlling size of A-site ion resulting in tolerance factor. The samples were prepared by Pechini method. SrCO3 and CaCO3 were dissolved in dilute HNO3. BaCO3 was dissolved in citric acid. Y2O3 and Ln2O3 were dissolved in HNO3 or mixture of HNO3 and H2O2 with heating. As an Fe source, Fe(NO3)3•9H2O, whose purity was verified with mass of Fe2O3 after heating at 800 ºC, was employed and dissolved in distilled H2O. The dissolved raw materials were mixed with nominal composition. After addition of citric acid and ethylene glycol, the solution was heated, resulting in precursor. The precursor was calcined at 750 ºC for more than 17 h in air. The obtained powder was pressed into pellet after pulverization and sintered at 1200 ºC for more than 17 h in air. The phase of the specimens was identified by X-ray diffraction measurements. Some specimens were subjected to Mössbauer spectroscopy and electron diffraction measurement for minute analysis of crystal structure. Thermal analyses such as TG-DTA and DSC were performed to clarify phase transition behavior.X-ray diffraction measurements of the samples with nominal composition of Sr1-x Ln x FeO3-δ and SrFe1-x Ln x O3-δ revealed that La, Nd, Ho, Y, Tm, Yb, and Lu could be substituted for Sr site with x=0.1-0.2 resulting in cubic perovskite structure, whereas only Tm, Yb, and Lu could be substituted for Fe site. This tendency was successfully explained assuming that Ln3+ substituted site with smaller difference of ionic radius. Although spots assigned as long-range order was observed in electron diffraction pattern of Sr0.9Y0.1FeO2.80, they were diffuse ones with small intensity, indicating large randomness of oxide ion distribution. Broad Mössbauer spectrum of Sr0.9Y0.1FeO2.80 and Sr0.9Yb0.1FeO2.80 identified as summation of Fe3.5+ with main intensity and smaller Fe3+ and Fe4+ also indicated random distribution of oxide ion vacancy. No DTA signal was observed between 25-1000 ºC, indicating arrangement of oxide ion vacancies was maintained.X-ray diffraction patterns of Sr1-x Ca x FeO3-δ were not assigned as cubic; whereas those of Sr1-x Ba x FeO3-δ with x=0.1, 0.15, and 0.2 were apparently identified as cubic perovskite. Iodometric titration revealed that Fe valence in Sr1-x Ba x FeO3-δ with x=0.1 and 0.2 was 3.5+. Because tolerance factor approaches 1.0 by partial substitution of Ba if Fe valence is 3.5+, the observed variation of crystal structure to apparently cubic could be explained by using tolerance factor. However, clear spots assigned as long-range order observed in electron diffraction patterns and Mössbauer spectrum showing both Fe3+ in octahedron and Fe4+ in pyramid indicated that crystal structure of Sr0.8Ba0.2FeO2.75 was not cubic but orthorhombic with ordered oxide ion vacancies. The X-ray diffraction pattern identified as apparent cubic could be attributed to small distortion of octahedron, pyramid, and their linkage from cubic perovskite. The endothermic peaks without mass variation were observed in TG-DTA and DSC curves in Sr1-x Ba x FeO2.75, indicating the structural phase transition. The phase transition temperature observed at 420 ºC for SrFeO2.75 decreased to 200 ºC for Sr0.8Ba0.2FeO2.75. The crystal structure at higher temperature than the phase transition temperature was identified as cubic with random oxide ion arrangement because the clear spots assigned as long-range order in electron diffraction patterns at room temperature disappeared or became diffused ones at 250 ºC.The investigation of electrical conductivity of cation substituted SrFeO3-δ is in progress at present.

Chiral Electrokinetic Phenomena in Single Nanopores

AbstractThe arrangement of solvent molecules and ions at solid–liquid interfaces determines electrochemical properties that are important in separations platforms, sensing technologies, and energy‐storage systems. Here we show that single glass and polymer pores in contact with propylene carbonate (PC) solutions of LiClO4 exhibit an effective surface potential that is modulated by the enantiomeric excess of the solvent. In particular, electrochemical and electrokinetic measurements of ionic transport through glass pipettes and polymer pores reveal that the effective surface potential is significantly lower in solutions prepared using enantiomerically pure PC than in solutions prepared using racemic PC. Both pore systems became positively charged in all racemic solutions examined in the range of LiClO4 concentrations between 1 mM and 100 mM, whereas solutions in (R)‐(+)‐PC induced a positive surface potential only at concentrations above ~5 mM. The effective surface potential is quantified through asymmetry in current–voltage curves and zeta‐potential measurements. Vibrational sum‐frequency‐generation experiments on LiClO4 solutions in racemic and enantiomerically pure PC indicate that the surface lipid‐bilayer‐like region in the former is more strongly organized than in the latter, dictating the favorable positions for lithium and perchlorate ions in each case. The more ordered molecular packing in the racemic liquid leads to accumulation of lithium ions on the outside of the bilayer, creating a higher effective positive charge. Our results highlight the extreme sensitivity of the interfacial potential on molecular organization of the solvent, and the relatively unexplored role that chirality can play in electrokinetic phenomena.

The Ordering and Arrangement of Intercalated Carboxylate Ions in Anion‐Exchangeable Layered Yttrium Hydroxides

AbstractThe intercalation chemistry is essential in the application of anion‐exchangeable layered metal hydroxides. However, much of the key information regarding intercalated anions, such as the degree of ordering and arrangement is still not clear or missing to date, due to the difficulty in probing the local environment of anions by routine characterization techniques. Herein, we employed solid‐state NMR (ssNMR) spectroscopy to offer valuable complementary insights into the ordering and arrangement of a series of monocarboxylate anions (RCOO−: R=HO, H, CH3, C2H5, and C3H7) within the interlayer space of two layered yttrium hydroxides (LYH‐Cl and LYH‐Br). The results imply that the two smaller carboxylate anions (R=HO and H) are disordered after intercalation, while the larger carboxylate anions (R=CH3, C2H5, and C3H7) are relatively ordered. We further explored if the intercalated anions are parallel arranged as those in sodium salts or antiparallel arranged as those predicted in the majority of previous reports. We uncovered that the intercalated anions are antiparallel arranged based on the formation energy obtained in density functional theory calculations and ssNMR data. Our results therefore contribute to a deeper and comprehensive understanding of the intercalation chemistry of layered rare earth hydroxides.

An anionic two dimensional covalent organic framework from tetratopic borate centres pillared by lithium ions

Non-covalent interactions play an important role for the framework formation of two-dimensional covalent organic frameworks. Until now, π–π interactions and hydrogen bonding are the main reported forces facilitating the stacking of framework layers. Here, we present a two-dimensional anionic covalent organic framework based on tetratopic borate linkages, where layers are connected by ionic interactions between the linkage site and counter cations. The crystalline covalent organic framework is accessed through the formation of an amorphous borate-based polymer and subsequent solvothermal treatment. The progress of crystallization is investigated, revealing the crystallite growth and morphological change from agglomerated dense particles to hollow crystallite spheres. Due to the pillared nature, the crystallites can be exfoliated into nanosheets by sonication of the material in the presence of methanol. The crystallization and ordered arrangement of the lithium ions in the interlayer space is shown to benefit the conductivity tenfold compared to the amorphous material.

(Invited) Solid/Electrolyte Interface Under Confinement in Divalent Water-in-Salt Electrolytes

Concentrated aqueous electrolytes (water-in-salt electrolytes, WiSEs) have gained increasing attention in the last few years because they display much wider electrochemical stability windows (upwards of 3V) than the thermodynamic limit of water (1.23V), making them exciting candidates for a variety of electrochemical systems including aqueous batteries. Importantly, it is the ions directly at the electrode/electrolyte interface that are key to explaining this unexpected reactivity. The electrode/electrolyte interface is classically thought of as the electrical double layer (EDL), or the ion arrangement at an interface that builds up to neutralize the surface potential. WiSEs present very different EDL structures than do classical dilute electrolytes. However, most work has focused on monovalent WiSEs, primarily motivated by Li-battery applications using lithium bis(trifluoromethylsulphonyl)imide (LiTFSI).In this work, we aim to understand how divalent ions within the WiSE regime alter both the short-range and long-range signatures of the EDL under confinement. For most of the above applications, reactions occur within the pore-space of a porous electrode, which exhibit confined, overlapping EDLs. Therefore, we use confinement as a tool to probe both the short-range layering structure (<10 nm) and electrostatic decay length (~10-100 nm) away from a charged interface with Surface Forces Apparatus (SFA) measurements.Using WiSEs comprising LiTFSI, Zn(TFSI)2, and mixtures of the two salts, we first establish the bulk structure of these electrolytes using Wide Angle X-Ray Scattering and Raman Spectroscopy, which reveal that the anion and cation are closely associated in all electrolytes, regardless of cation valency. Additionally, clusters of ions are formed in all electrolytes, however, the clusters are suppressed with increasing divalent ion fraction. Under confinement, SFA results demonstrate that the thickness of the adsorbed layer of ions at a solid/electrolyte interface grows with increasing divalent ion fraction. Multiple interfacial layers are formed following this adlayer, and these layers seem dependent on anion size, rather than cation. Importantly, all electrolytes exhibit very long electrostatic decay lengths that are insensitive to valency. This work contributes significant fundamental understanding regarding the structure and charge-neutralization mechanism in this class of electrolytes both in the bulk and under confinement at an interface.

Unveiling the Structural and Dynamic Characteristics of Concentrated LiNO3 Aqueous Solutions through Ultrafast Infrared Spectroscopy and Molecular Dynamics Simulations.

Highly concentrated aqueous electrolytes have attracted a significant amount of attention for their potential applications in lithium-ion batteries. Nevertheless, a comprehensive understanding of the Li+ solvation structure and its migration within electrolyte solutions remains elusive. This study employs linear vibrational spectroscopy, ultrafast infrared spectroscopy, and molecular dynamics (MD) simulations to elucidate the structural dynamics in LiNO3 solutions by using intrinsic and extrinsic vibrational probes. The N-O stretching vibrations of NO3- exhibit a distinct spectral splitting, attributed to its asymmetric interaction with the surrounding solvation structure. Analysis of the vibrational relaxation dynamics of intrinsic and extrinsic probes, in combination with MD simulations, reveals cage-like networks formed through electrostatic interactions between Li+ and NO3-. This microscopic heterogeneity is reflected in the intertwined arrangement of ions and water molecules. Furthermore, both vehicular transport and structural diffusion assisted by solvent rearrangement for Li+ were analyzed, which are closely linked with the bulk concentration.

Ferritin at different iron loading: From biological to nanotechnological applications

The characterization of the structure of ferritin in solution and the arrangement of iron stored in its cavity are intriguing subjects for both cell biology and applied science, since the protein structure, stability, and easiness of production make it an ideal tool for biomedical applications. We characterized the ferritin structure over a wide range of iron loadings by visible light, X-ray, and neutron scattering techniques. We found that the arrangement of iron ions inside the protein cage resulted in a more disposable arrangement at lower loading factors and then in a crystalline structure. At very high iron content the inner core is composed of magnetite more than ferrihydrite, and the shell of the protein is elastically deformed by the iron crystal growth in an ellipsoidal arrangement. The application of an external radiofrequency (RF) magnetic field affected ferritins at low iron loading factors. Notably the RF modified the iron disposition towards a more dispersed arrangement. The structural characterization of the ferritin at different LFs and in presence of magnetic fields provides useful insights into their physiological behaviour and can help in the design and fine-tuning of ferritin-based nanosystems for biotechnological applications.

Crystal Symmetry-Inspired Algorithm for Optimal Design of Contemporary Mono Passivated Emitter and Rear Cell Solar Photovoltaic Modules

A metaheuristic algorithm named the Crystal Structure Algorithm (CrSA), which is inspired by the symmetric arrangement of atoms, molecules, or ions in crystalline minerals, has been used for the accurate modeling of Mono Passivated Emitter and Rear Cell (PERC) WSMD-545 and CS7L-590 MS solar photovoltaic (PV) modules. The suggested algorithm is a concise and parameter-free approach that does not need the identification of any intrinsic parameter during the optimization stage. It is based on crystal structure generation by combining the basis and lattice point. The proposed algorithm is adopted to minimize the sum of the squares of the errors at the maximum power point, as well as the short circuit and open circuit points. Several runs are carried out to examine the V-I characteristics of the PV panels under consideration and the nature of the derived parameters. The parameters generated by the proposed technique offer the lowest error over several executions, indicating that it should be implemented in the present scenario. To validate the performance of the proposed approach, convergence curves of Mono PERC WSMD-545 and CS7L-590 MS PV modules obtained using the CrSA are compared with the convergence curves obtained using the recent optimization algorithms (OAs) in the literature. It has been observed that the proposed approach exhibited the fastest rate of convergence on each of the PV panels.

Unraveling the energy storage mechanism in graphene-based nonaqueous electrochemical capacitors by gap-enhanced Raman spectroscopy

Graphene has been extensively utilized as an electrode material for nonaqueous electrochemical capacitors. However, a comprehensive understanding of the charging mechanism and ion arrangement at the graphene/electrolyte interface remain elusive. Herein, a gap-enhanced Raman spectroscopic strategy is designed to characterize the dynamic interfacial process of graphene with an adjustable number of layers, which is based on synergistic enhancement of localized surface plasmons from shell-isolated nanoparticles and a metal substrate. By employing such a strategy combined with complementary characterization techniques, we study the potential-dependent configuration of adsorbed ions and capacitance curves for graphene based on the number of layers. As the number of layers increases, the properties of graphene transform from a metalloid nature to graphite-like behavior. The charging mechanism shifts from co-ion desorption in single-layer graphene to ion exchange domination in few-layer graphene. The increase in area specific capacitance from 64 to 145 µF cm–2 is attributed to the influence on ion packing, thereby impacting the electrochemical performance. Furthermore, the potential-dependent coordination structure of lithium bis(fluorosulfonyl) imide in tetraglyme ([Li(G4)][FSI]) at graphene/electrolyte interface is revealed. This work adds to the understanding of graphene interfaces with distinct properties, offering insights for optimization of electrochemical capacitors.

Renewing Fundamental Understanding of Ionic Transport in Inorganic Crystalline Solid‐State Electrolytes from the Perspective of Lattice Dynamics

AbstractLattice dynamics has been widely employed to study various properties of crystalline materials, by revealing the atomic vibration rules with phonon dispersion curves. Modulating lattice‐dynamics‐related factors is an emerging trend in the design of inorganic crystalline solid‐state electrolytes (ICSSEs) with promoted ionic conductivity. Nevertheless, due to complicated interplay of these enormous factors, fundamental understanding of lattice‐dynamics‐influenced ionic transport is still limited. In this review, all related factors are classified into lattice static and dynamic ones based on their variability in ionic transport process, facilitating a methodological evaluation of their individual and interrelated influences. The previous efforts are affirmed to design ICSSEs by constructing potential energy surfaces for ionic transport based on lattice static factors (e.g., ionic arrangement, time‐scale dependent ionic concentration, and lattice softening). As for lattice dynamic factors, the possibility to quantify ionic transport activation energy and to screen the type of migration ions by phonon frequency and amplitude, respectively is validated. Specifically, it is highlighted that the optimization of specific phonon mode and the coupling of both lattice static and dynamic factors are essential to achieve superior ionic transport in ICSSEs. Finally, challenges and opportunities are pointed out in this field, which can potentially guide the future development of ICSSEs.

An Advanced Methodology for Crystal System Detection in Li-ion Batteries

Detecting the crystal system of lithium-ion batteries is crucial for optimizing their performance and safety. Understanding the arrangement of atoms or ions within the battery’s electrodes and electrolyte allows for improvements in energy density, cycling stability, and safety features. This knowledge also guides material design and fabrication techniques, driving advancements in battery technology for various applications. In this paper, a publicly available dataset was utilized to develop mathematical equations (MEs) using a genetic programming symbolic classifier (GPSC) to determine the type of crystal structure in Li-ion batteries with a high classification performance. The dataset consists of three different classes transformed into three binary classification datasets using a one-versus-rest approach. Since the target variable of each dataset variation is imbalanced, several oversampling techniques were employed to achieve balanced dataset variations. The GPSC was trained on these balanced dataset variations using a five-fold cross-validation (5FCV) process, and the optimal GPSC hyperparameter values were searched for using a random hyperparameter value search (RHVS) method. The goal was to find the optimal combination of GPSC hyperparameter values to achieve the highest classification performance. After obtaining MEs using the GPSC with the highest classification performance, they were combined and tested on initial binary classification dataset variations. Based on the conducted investigation, the ensemble of MEs could detect the crystal system of Li-ion batteries with a high classification accuracy (1.0).

Elevating both capacity and voltage tolerance of P2-type layered cathodes with cooperative Al cation/F anion co-doping for advanced sodium-ion batteries

The single ionic doping helps suppress the detrimental phase transition when P2-type layered cathodes are charged to a high voltage above 4.0 V (vs. Na+/Na). However, this is realized at the sacrifice of their electrochemical redox centers and output capacities. To achieve both high voltage tolerance and capacity, we herein propose a cooperative Al cation and F anion co-doping strategy. The XANES detections affirm that substituting Ni/O with Al/F intends to augment the amount of highly active Mn3+ cations in cathodes, making more contributions on specific capacities for sodium-ion batteries (SIBs). Besides, this co-doping treatment would disorder the transition metal ionic arrangements of cathodes, disrupting long-range Jahn-Teller effects and impeding other undesired phases generation. As a proof-of-concept demonstration, our designed Na2/3Ni0.23Al0.1Mn2/3O1.95F0.05 (NAF) cathodes show a delivered capacity as high as 142.0 mAh g−1 (0.2C), and an impressive capacity retention of 86.7 % after all cycling. The in-situ XRD detections reveal no apparent O2 phase peaks emerge until 4.23 V upon deep Na+ extraction from NAF. This work provides a key understanding toward cation/anion co-doping effects, opening up a useful avenue for rational design of practical P2-type cathodes for SIBs.

Synthesis of Fe2＋-based 18H-type ferrite, Ba5Fe[formula omitted]Fe[formula omitted]Ti[formula omitted]O31

To obtain Fe2＋-based 18H-type ferrite (Ba5Fe2−x2+Fe12+2x3+Ti3−xO31), we synthesized a series of samples in the composition range of 0≤x≤1.5 at sintering temperatures ranging from 1000 to 1200 °C. The observed phases were identified, revealing the formation of single-phase samples in the composition range of 0.2≤x≤0.8 at sintering temperatures between 1150 and 1185 °C. The Curie temperatures of the Fe2＋-based 18H-type ferrites were approximately 360 °C, exhibiting an increasing tendency as x increased. The saturation magnetizations of samples sintered at 1170 °C were found to range from 25.2 emu/g to 29.3 emu/g within the range of 0.3≤x≤1.0, displaying an increasing trend with increasing x. Additionally, a plausible arrangement of ions within the crystal structure of 18H-type ferrite crystal was proposed.

Synchrotron small-angle X-ray scattering study of flame retardants based on ammonium sulfate and disubstituted ammonium phosphate

The use of wood in structural and finishing materials can significantly reduce the time of building construction, but the high flammability of wood limits its use in the building industry. To increase fire resistance, wooden structures are impregnated with flame retardants and the penetrating ability depends on their structure. We present the results of a small-angle X-ray scattering study of the structure of flame retardants based on ammonium sulfate and phosphate. The radii of inertia of hydrated complexes formed when flame retardants are dissolved in water, their shape and type of chains along which hydrated ions are located are determined. It is revealed that the presence of diffraction maxima indicates the presence of an ordering in the arrangement of hydrated ions. Aqueous solutions of ammonium sulfate and disubstituted ammonium phosphate contain two types of hydrated complexes of the same shape but different radius of inertia. At the same time, hydrated ions in complexes are located along persistent chains, and ordering revealed in the arrangement of ions, depended on their type. The results obtained can be used in developing flame retardants with a reduced radius of inertia, which will increase the penetrating capacity of the processing solution and increase the fire safety of wooden structures.

Colossal Ferroelectric Photovoltaic Effect in Inequivalent Double-Perovskite Bi2FeMnO6 Thin Films.

Double perovskite films have been extensively studied for ferroelectric order, ferromagnetic order, and photovoltaic effects. The customized ion combinations and ordered ionic arrangements provide unique opportunities for bandgap engineering. Here, a synergistic strategy to induce chemical strain and charge compensation through inequivalent element substitution is proposed. A-site substitution of the barium ion is used to modify the chemical valence and defect density of the two B-site elements in Bi2FeMnO6 double perovskite epitaxial thin films. We dramatically increased the ferroelectric photovoltaic effect to ∼135.67 μA/cm2 from 30.62 μA/cm2, which is the highest in ferroelectric thin films with a thickness of less than 100 nm under white-light LED irradiation. More importantly, the ferroelectric polarization can effectively improve the photovoltaic efficiency of more than 5 times. High-resolution HAADF-STEM, synchrotron-based X-ray diffraction and absorption spectroscopy, and DFT calculations collectively demonstrate that inequivalent ion plays a dual role of chemical strain (+1.92 and -1.04 GPa) and charge balance, thereby introducing lattice distortion effects. The reduction of the oxygen vacancy density and the competing Jahn-Teller distortion of the oxygen octahedron are the main phenomena of the change in electron-orbital hybridization, which also leads to enhanced ferroelectric polarization values and optical absorption. The inequivalent strategy can be extended to other double perovskite systems and applied to other functional materials, such as photocatalysis for efficient defect control.

Sub-nanopores enabling optimized ion storage performance of carbon cathodes for Zn-ion hybrid supercapacitors

Aqueous Zn-ion hybrid supercapacitors (ZHSs) are attracting significant attention as a promising electrochemical energy storage system. However, carbon cathodes of ZHSs exhibit unsatisfactory ion storage performance due to the large size of hydrated Zn-ions (e.g., [Zn(H2O)6]2+), which encumbers compact ion arrangement and rapid ion transport at the carbon-electrolyte interfaces. Herein, a porous carbon material (HMFC) with abundant sub-nanopores is synthesized to optimize the ion storage performance of the carbon cathode in ZHSs, in which the sub-nanopores effectively promote the dehydration of hydrated Zn-ions and thus optimize the ion storage performance of the carbon cathode in ZHSs. A novel strategy is proposed to study the dehydration behaviors of hydrated Zn-ions in carbon cathodes, including quantitatively determining the desolvation activation energy of hydrated Zn-ions and in-situ monitoring active water content at the carbon-electrolyte interface. The sub-nanopores-induced desolvation effect is verified, and its coupling with large specific surface area and hierarchically porous structure endows the HMFC cathode with improved electrochemical performance, including a 53 % capacity increase compared to the carbon cathode counterpart without sub-nanopores, fast charge/discharge ability that can output 46.0 Wh/kg energy within only 4.4 s, and 98.2 % capacity retention over 20,000 charge/discharge cycles. This work provides new insights into the rational design of porous carbon cathode materials toward high-performance ZHSs.

Multiple Representations Analysis of Chemical Bonding Concepts in General Chemistry Books

This research aimed to analyze the use of the concept of the three levels of chemical representation in eight general chemistry books. It was qualitative research with an evaluative descriptive design. The concepts analyzed included the concepts of ionic, covalent, and metallic bonds. The analysis focused on two main criteria: the use of macroscopic, sub-microscopic, and symbolic levels of representation and the relationship between the three levels. The results of the analysis showed that in the concept of ionic bonding, there were pictures of some salts or reactions for the formation of ionic compounds from their elements at the macroscopic level, explanations at the sub-microscopic level, and models of the arrangement of ions in the ionic crystal lattice for the symbolic level. In the concept of covalent bonds, there were images of gasses or covalent compounds at the macroscopic level, explanations at the sub-microscopic level, and models of electron density shifts at the symbolic level. In the concept of metallic bonds, there were pictures of some metals at the macroscopic level, explanations at the sub-microscopic level, and electron cloud models at the symbolic level. The relationship between the levels of representation was found in five of the eight general chemistry books analyzed. General chemistry books present the relationship between the three levels of representation in images that include energy level diagrams, atomic or ionic arrangement models, reaction equations, and explanations of the molecular level. Keywords: concept, chemical representation, general chemistry, books