Aqueous Electrolyte Solutions Research Articles

Nanoscale Hydrophobicity of Transport Barriers in the Nuclear Pore Complex as Compared with the Liquid/Liquid Interface by Scanning Electrochemical Microscopy.

The nuclear pore complex (NPC) is the proteinous nanopore that solely regulates molecular transport between the nucleus and cytoplasm of a eukaryotic cell. Hypothetically, the NPC utilizes the hydrophobic barriers based on the repeats of phenylalanine-glycine (FG) units to selectively and efficiently transport macromolecules. Herein, we quantitatively assess the hydrophobicity of transport barriers confined in the nanopore by applying scanning electrochemical microscopy (SECM). The hypothesis deduced from studies of isolated FG-rich nucleoporins is supported quantitatively by investigating the authentic NPC for the first time. Specifically, we employ the n repeats of neurotoxic glycine-arginine dipeptide, GRn, as the molecular probes that engage in hydrophobic interactions with transport barriers in the NPC. We apply ion-transfer voltammetry at a micropipet-supported interface between aqueous and organic electrolyte solutions to confirm that larger GRn among n = 5-25 is more hydrophobic, as expected theoretically. The micropipet also serves as the tip of transient SECM to demonstrate that the NPC interacts more strongly with larger GRn, which supports the hydrophobicity of transport barriers. Kinetically, larger GRn stays in the NPC for longer to clog the nanopore, thereby expressing neurotoxicity. Significantly, this work implies that the efficient and safe nuclear import of genetic therapeutics requires an optimum balance between strong association with and fast dissociation from the NPC. Interestingly, this work represents the unexplored utility of liquid/liquid interfaces as models of hydrophobic protein condensates based on liquid-liquid phase separation as exemplified by nanoscale transport barriers in the NPC.

Transport Numbers and Electroosmosis in Cation-Exchange Membranes with Aqueous Electrolyte Solutions of HCl, LiCl, NaCl, KCl, MgCl2, CaCl2 and NH4Cl.

Electroosmosis reduces the available energy from ion transport arising due to concentration gradients across ion-exchange membranes. This work builds on previous efforts to describe the electroosmosis, the permselectivity and the apparent transport number of a membrane, and we show new measurements of concentration cells with the Selemion CMVN cation-exchange membrane and single-salt solutions of HCl, LiCl, NaCl, MgCl2, CaCl2 and NH4Cl. Ionic transport numbers and electroosmotic water transport relative to the membrane are efficiently obtained from a relatively new permselectivity analysis method. We find that the membrane can be described as perfectly selective towards the migration of the cation, and that Cl- does not contribute to the net electric current. For the investigated salts, we obtained water transference coefficients, tw, of 1.1 ± 0.8 for HCl, 9.2 ± 0.8 for LiCl, 4.9 ± 0.2 for NaCl, 3.7 ± 0.4 for KCl, 8.5 ± 0.5 for MgCl2, 6.2 ± 0.6 for CaCl2 and 3.8 ± 0.5 for NH4Cl. However, as the test compartment concentrations of LiCl, MgCl2 and CaCl2 increased past 3.5, 1.3 and 1.4 mol kg-1, respectively, the water transference coefficients appeared to decrease. The presented methods are generally useful for characterising concentration polarisation phenomena in electrochemistry, and may aid in the design of more efficient electrochemical cells.

CCQM-K170 - electrolytic conductivity at 0.5 S m-1 and 20 S m-1 - final report

Main textThe comparison CCQM-K170 is a subsequent key comparison of CCQM-K36.2016 and CCQM-K92. It aims to demonstrate the capabilities of the participating NMIs/DIs to measure the electrolytic conductivity of aqueous electrolyte solution in the electrolytic conductivity range around 0.5 S m-1 and 20 S m-1. The coordinating institute (NIM) prepared two potassium chloride solutions with the nominal electrolytic conductivity of 0.5 S m-1 and 20 S m-1, and verified their homogeneity and stability. Seventeen and twelve NMIs/DIs, respectively, reported their measurement results of 0.5 S m-1 and 20 S m-1 samples, respectively. The institutes used primary and secondary methods, and commercial instruments. Institutes using non-NMI CRMs as calibrants or CRMs from a participating NMI were excluded from KCRV calculation. The measurement results traceable to CRMs from the same non-participating NMI were combined into one result to be used for KCRV calculation. The results of institutes which have indicated technical problems were also excluded from KCRV calculation. The medians were agreed upon as the KCRVs for 0.5 S m-1 and 20 S m-1 solutions based on CCQM/2013-22 guidance document. Good agreement of the results was observed for the majority of participants. The results of this key comparison are considered representative for electrolytic conductivity measurement of aqueous electrolyte solution in the electrolytic conductivity range 0.15 S m-1 to 1.5 S m-1 and 5 S m-1 to 25 S m-1, respectively. This KC is intended as an updated support for the corresponding calibration and measurement capabilities (CMCs) entries in the key comparison data base of the BIPM.To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/.The final report has been peer-reviewed and approved for publication by the CCQM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Ultrasonic Effect on the Growth of Crystals from Aqueous Electrolyte Solutions on Polymer Substrates: The Role of Isotopic Composition of Liquid.

The peculiarities of the crystal formation from supersaturated aqueous solutions of CuSO4 on polymer substrates were studied using X-ray diffractometry. During the crystal formation, the test solutions were irradiated with one or two counter-propagating ultrasonic beams. Test solutions were prepared using natural deionized water with a deuterium content of 157 ± 1 ppm. The other liquid used was deuterium-depleted water with a deuterium content of 3 ppm. It was shown that irradiation with one/two ultrasonic beams resulted in drastic changes in the structure of the crystal deposit formed on the polymer substrate in the case when natural deionized water was chosen for preparing the supersaturated solution of CuSO4.

The process of electrolyte-plasma cathode exfoliation of graphite

We discussed the development of cathodic electrochemical exfoliation of graphite, accompanied by a plasma discharge with a voltage of 200V DC, in an aqueous solution of various electrolytes. The method of cathodic electrochemical exfoliation of graphite has established itself as a promising eco-friendly industrial method for producing nanographite with subsequent grinding by ultrasound into low-layer graphene (FLG). Cathodic exfoliation allows selective doping of nanographite oxygen atoms.

Facile synthesis of CuCo2O4@CdS nanoheterostructure for asymmetric supercapacitor

The abundant active sites, high theoretical capacitance, and cost-effective synthesis of transition metal oxides@sulfides (TMOs@TMSs) have made them a highly desirable choice as active electrode materials for supercapacitors. This study demonstrated the successful fabrication of a CuCo2O4@CdS nanoheterostructure electrode using a simple and economical co-precipitation method The morphology, physicochemical properties, and electrochemical behavior of this electrode were subsequently studied. The synthesized CuCo2O4@CdS nanoheterostructure was characterized using Infrared Fourier-transform spectroscopy, X-ray diffraction, Raman spectroscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, High-resolution transmission electron microscopy, N2 adsorption/desorption isotherms and atomic force microscopy. The electrochemical performance was studied using cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge (GCD) measurements with a 6 Molar KOH aqueous electrolytic solution. Results from powder X-ray diffraction pattern and energy dispersive X-ray revealed the formation of CuCo2O4@CdS nanoheterostructure. Furthermore, SEM images showed the formation of more spherical structures in nanoheterostructure. The results of optical measurements of thin films were analyzed, which showed an increase in the energy gap (Eg) of CuCo2O4 nanoparticles when combined with cadmium sulfide (CdS). Additionally, the intensity of photoluminescence of the CuCo2O4@CdS nanoheterostructure was lower compared to the pure nanoparticles. Moreover, the newly synthesized CuCo2O4@CdS nanoheterostructure showed a specific capacitance of 257.5 F g−1 at a current density of 0.5 A g−1 via a three-electrode galvanostatic charge-discharge system, respectively. In the asymmetric device, the supercapacitor yielded an optimum energy density and power density of 19.6 Wh kg−1 and 700 W kg−1 at 1 A g−1 current density, respectively. Although the capacitance retention was maintained at nearly 85.2 % after 4000 cycles at a current density of 3 A g−1.

Experimental confirmation of the bactericidal action of the domestic antiseptic “Anolit” in surgical practice

Background. Antimicrobial resistance is one of the most serious threats to modern clinical medicine. Despite the significant successes of modern pharmacology, the search for effective antiseptics that can influence wound processes continues. In our study, an experimental study of the effect of Anolit solution on pathogenic microorganisms Pseudomonas aeruginosa and Proteus mirabilis was conducted.The aim. To evaluate the antimicrobial activity of the domestic antiseptic “Anolit” against gram-negative pathogens of nosocomial infections using the example of P. aeruginosa and P. mirabilis.Methods. To assess the quality of the effect of “Anolit” on the studied colonies of microorganisms, experimental studies were performed in vitro. The bacteriological study was carried out in three stages using the Koch method.Results. “Anolit” is a modern antiseptic agent with a pronounced antimicrobial effect based on the electrolysis of aqueous solutions. Its ability to lyse pathogenic microorganisms (P. aeruginosa and P. mirabilis) has been confirmed by experimental research.Conclusion. The bactericidal effect of “Anolit” on the growth of gram-negative bacteria is shown, proving its high antimicrobial efficacy.

Structure of the Electric Double Layer in Non-Aqueous Electrolytes for Lithium Metal Batteries

The electric double layer (EDL) plays a crucial role in electrochemistry as it controls the orientation and movement of ions and solvent molecules at the electrode-electrolyte interface. Ever since the concept of the EDL was first introduced by Helmholtz in 1879, there has been a proliferation of research studies in electrocatalysis and electrochemical energy storage dedicated to the structure of the EDL in aqueous electrolyte solutions [1, 2]. In recent years, probing the structure of the EDL in non-aqueous electrolyte solutions has gained more attention, predominantly in EDL capacitors (EDLCs) [3, 4]. Meanwhile, despite its contribution to the formation of solid electrolyte interphase (SEI) in lithium-metal batteries (LMBs), the comprehension of the EDL in LMBs is still very limited [5, 6]. Compared to EDLCs, it is more challenging to accurately capture the structure of the EDL in LMBs due to the complexity of Faradaic processes and chemical reactions at the interface. Furthermore, with the formation of SEI in LMBs after charge/discharge cycling, it becomes a formidable task to analyze the structure of the EDL because the length scales of SEI and EDL are comparable (approximately 10 nm), coupling with the complicated structure of the SEI. For these reasons, it is important to thoroughly examine the structure of the EDL in non-aqueous electrolytes with the presence of SEI in LMBs, which will provide insight to the interfacial chemistry as well as help design electrolytes for better battery performance.In this work, the structure of the EDL in non-aqueous electrolyte solutions in LMBs was experimentally investigated. Specifically, by using electrochemical impedance spectroscopy (EIS), we performed the differential capacitance measurements for varied concentrations of LiPF6 in varied ratios of EC:EMC solvent. Due to the complexity of interfacial chemistry in LMBs, we developed a rigorous equivalent circuit to precisely extract the differential capacitance from EIS measurements. We then applied thin crosslinked polymer and inorganic layers to the electrode to study how the EDL capacitance changes in the presence of these model SEIs. This work serves as an important step towards understanding the evolution of the EDL structure in LMBs after charge/discharge cycling with the interference of SEI at the electrode-electrolyte interface.

Suppression of the Leidenfrost Effect By Controlling the Nanostructure of Aluminum Surfaces

The Leidenfrost effect is a phenomenon in which a liquid droplet forms a thin film of its vapor on a substrate hotter than the boiling point, causing the droplet to float above the hot substrate. The vapor film inhibits heat transfer between the droplet and the substrate, which reduces the cooling efficiency when the droplet cools the high-temperature substrate. It has been known that the Leidenfrost effect can be suppressed by forming nano- and micro-scale pillars and spikes on the substrate surface [1, 2]; however, conventional methods of constructing nano- and micro-structures require expensive equipment and the process is complicated. Anodic porous alumina films with self-ordered cylindrical nanopore channels can be fabricated on aluminum substrate simply by anodizing in appropriate aqueous electrolyte solutions. The structure parameters of porous alumina, such as pore size, interpore distance, and pore length, can be easily controlled by anodizing voltage and time. This study demonstrates that the anodic porous alumina films can be applied to control the Leidenfrost effect.Ultrasonically cleaned and electropolished Al plates (99.999%, 1.0-mm thick) were used as specimens. The specimens were immersed in 0.3 M sodium tetraborate solution (343 K) and anodized at 10-200 V for 60 min. The nanostructure of the anodic porous alumina was observed by SEM. The static contact angle of the specimen was measured with a contact angle meter. The behavior of water droplets on the specimen at 473 K was captured by a high-speed camera. The temperature of the specimen was measured using a thermal imaging camera.Constant voltage anodizing of Al resulted in the formation of porous alumina films with numerous pores. As the anodizing voltage was increased, the pore size increased, with an average pore size of 294 nm at 200 V (Fig. 1a). The static contact angle of the anodized surface became smaller as the pore size increased.Fig. 1b shows snapshots of the behavior of a water droplet (6 μL) on a smooth aluminum surface at 473 K. The water droplet bounced after dropping and took a long time to evaporate due to the Leidenfrost effect. On the other hand, when the same experiment was performed on the surface of an anodized specimen, the water droplets wetted and spread immediately after contact with the substrate and evaporated in about 50 ms while splitting into fine droplets (Fig. 1c). The surface temperature after dropping the water droplet (12 μL) decreased significantly on the porous alumina with large pores. Therefore, the formation of anodic porous alumina film on the substrate surface effectively suppresses the Leidenfrost effect, suggesting that increasing the pore size can improve the substrate cooling efficiency.[1] H. Kim, B. Truong, J. Buongiorno, L. W. Hu, Applied Physics Letters, 98, 083121 (2011).[2] C. Kruse, T. Anderson, C. Wilson, C. Zuhlke, D. Alexander, G. Gogos, S. Ndao, Langmuir, 29, 9798-9806 (2013). Figure 1

(Invited) application of Organic Frameworks for the Control of Electrochemical Processes and Electrocatalytic Properties

Electrochemical processes including electrocatalysis often take place in aqueous electrolyte solutions. Their performances are influenced greatly by the structure of electrolyte-electrocatalyst interface, which may regulate mass transfer that is important in controlling surface reactions through altering the overall reaction kinetics. We recently designed and synthesized amine-based covalent organic frameworks (COFs) from triformylphloroglucinol and 2-nitro-p-phenylenediamine precursors through Schiff base reaction. In this presentation, I will present our recent results on the effects of these COFs on proton transfer at electrocatalyst-organic frameworks/electrolyte interfaces and their impacts on the electrocatalytic activity. In the experimental design, these organic frameworks were functionalized with amine (NH2), nitro (NO2) sulfonic (SO3) and other functional groups. We found these COFs exhibited excellent stability across a wide potential window under acidic conditions. We observed the use of functionalized amine-based COFs can act as a good modifier to facilitate proton transfer for hydrogen evolution reaction (HER). Results from the electrochemical solid-liquid interface (ESLI)-based density functional theory (DFT) calculations suggest that functionalized COFs increase the local hydrogen concentration at the COF-electrocatalyst interface. Our simulation data also suggests the enhancement in HER activity is achieved partially through the protonation of amine of the COFs, suggesting a new mode of interfacial control for enhancing the electrocatalytic kinetics.

A Low-Cost Zn-Ion Hybrid Supercapacitors with High Energy Density

In recent years, hybrid supercapacitors with greater potential and improved energy density have been completed by combining some battery and supercapacitor type electrodes. According to some researchers’ research, “hybrid” supercapacitor systems are technically “asymmetric” supercapacitor systems since they are built on two separate supercapacitor type electrodes. The primary aim behind the development of a hybrid capacitor (HC) is to improve the energy density or specific energy of the device, which will significantly boost the storage property. Moreover, the use of an electrical double layer capacitor type electrode provides a large surface area, improving the electrode/electrolyte interaction region, and helps in the fast ion-adsorption process, which prevents the degradation of the battery-type electrode due to repeated charge-discharge cycles. A suitable combination of specific power (due to the EDLC electrode) and specific energy (due to the faradic electrode) could drastically enhance the stability and longevity of the hybrid supercapacitor device. The di/tri-valent metal ion (Mg2+, Zn2+, Ca2+, Al3+, etc.) hybrid capacitors have garnered considerable attention in recent years owing to their potential cost benefit and application in stationary storage systems, whose development is crucial for the mass-scale penetration of renewable energy technologies.Zinc‐ion hybrid supercapacitors (ZIHSs) may be the most promising energy storage device alternatives for portable and large‐scale electronic devices, as they combine the benefits of both supercapacitors and zinc‐ion batteries. ZIHSs are mostly based on battery-type Zn metal as an anode and physical adsorption-based carbon materials as the cathode. Porous carbon materials with high surface area, good electrochemical stability, low cost, high electronic conductivity and tuneable surface structure are deemed as promising cathode materials for ZIHSs. It is generally recognized that the micropores facilitate electrochemical energy storage, and mesopores can effectively reduce the ion diffusion distance and transport resistance. Therefore, the adjustment and optimization of porous carbons electrodes are of great significance to ZIHSs.This work provides some insight into the strategy for designing effective non-aqueous and aqueous Zn-ion hybrid supercapacitors. Electrochemical characteristics of Zn-ion hybrid supercapacitor cells based on non-aqueous 1 M acetonitrile (AN) or propylene carbonate (PC) electrolytes with addition Zn(BF4)2, zinc di[bis(trifluoromethylsulfonyl)imide] (Zn(TFSI)2) and zinc trifluoromethanesulfonate (Zn(OTf)2) have been studied. Very high energy and power densities (80 Wh kg−1 and 21.2 kW kg−1) have been measured for 1 M Zn(BF4)2/AN based Zn-ion based hybrid supercapacitors (Fig. 1a). Very good stability during 3,000 cycles of cells has been achieved demonstrating reasonably high energy efficiency value (66.8%) for Zn(TFSI)2/AN based ZIHS cell, decreasing in the order of electrolytes: Zn(TFSI)2/AN > Zn(BF4)2/PC > Zn(TFSI)2/PC > Zn(OTf)2/AN > Zn(BF4)2/AN. Some assembled ZIHSs had shown excellent cycling and energy stability over 20,000 cycles [1].Electrochemical behaviour of Zn cation based salts in various aqueous electrolytes (ZnSO4, Zn(BF4)2, Zn(TFSI)2, and Zn(OTf)2) has been studied in thin ZIHS cell and compared with Zn(ClO4)2 aqueous electrolyte based cell electrochemical characteristics. At moderate specific power value (10 kW kg− 1) noticeable decrease of specific energy has been established in the order of aqueous electrolytes: Zn(ClO4)2 ⩾ Zn(BF4)2 > Zn(OTf)2 > Zn(TFSI)2 > ZnSO4 (Fig. 1b). The stability of Zn-ion hybrid supercapacitor cells under study in aqueous electrolyte solutions has been tested using the long lasting (up to 10,000 cycles) constant current charge/discharge method and very good stability for Zn(OTf)2, Zn(ClO4)2 and ZnSO4 has been observed [2,3].Taking into account the cheap and environmental friendliness electrodes and electrolyte used, the results can be applied for assembling of the cheap high energy density hybrid supercapacitors for sustainable energy storage/recuperation complexes, combined with photovoltaic fields and/or wind electricity generating systems. Acknowledgements This work was supported by the Estonian Ministry of Education and Research (TK210, Centre of Excellence in Sustainable Green Hydrogen and Energy Technologies), Personal Research Grant PRG676 and R&D project EAG228. The experimental part of the research was partially co-funded by the Feasibility Fund of the University of Tartu Development Fund.

Formation of Porous Anodic Aluminum Oxide with a Thick Barrier Layer and High Porosity By Anodizing Aluminum in Sodium Metaborate Solutions

Porous-type anodic aluminum oxide (AAO) can be fabricated by anodizing an aluminum substrate in suitable aqueous electrolyte solutions. The morphological properties of the AAO, including the interpore distance, pore size, and thickness, are controlled by various operating parameters, such as the applied voltage, temperature, and anodizing time. However, their structural controllability is limited because the fabrication process is based on the typical anodizing method in acidic solutions. The authors previously found that AAO with a novel nanostructure can be fabricated by anodizing using alkaline ammonium carbonate and sodium tetraborate. Therefore, further research on aluminum anodizing using various alkaline solutions opens the possibility of novel AAO fabrication. Herein, we report the fabrication of a new AAO film, which is different from the typical nanostructure formed in acidic solutions, by anodizing in alkaline sodium metaborate (NaBO2).Electropolished aluminum specimens were anodized at a constant voltage of 0.1-200 V in a 0.3 M sodium metaborate electrolyte solution (pH = 11.9) at 278 K. The surface and cross-section of the anodized specimens were examined by field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and Cs-corrected scanning transmission electron microscopy (STEM). The elemental depth profile of the specimens was analyzed by radiofrequency glow discharge optical emission spectroscopy (rf-GDOES).An AAO film consisting of an outer porous layer and an inner hemispherical cap barrier layer, similar to typical AAO films formed in acidic solutions, was formed at lower voltages below 50 V. In contrast, an AAO film with a flat barrier layer, deviating from the typical Keller-Hunter-Robinson model, was obtained at voltages above 100 V. The porosities of the porous layer obtained above 20 V were almost constant (0.16-0.19). However, there was a significant increase in the porosity at lower voltages (0.93 at 0.1 V). The AAO formed in sodium metaborate was composed of amorphous, anion-free aluminum oxide. Figure 1

Liquid Structure of Super-Concentrated Aqueous Electrolyte Solutions with Various Alkali Metal Salts and Its Effect on Battery Performance

Super-concentrated electrolyte aqueous solution (SCES) has been attracting attention as an electrolyte solution for aqueous lithium-ion secondary battery (ALIB) because of its wide potential window. However, further improvement is needed in the currently reported SCES because the SCES contains several tens of percent of bulk water that is not coordinated with Li ions1). It is known that Alkali metal ions with a large ionic radius interact with surrounding water molecules to destroy the hydrogen bonding network in water, which may promote the coordination of free water molecules to Li ions. In the present work, to improve the battery performance, we developed new SCESs with alkali metal ions with a large ionic radius as additives. SCES (aqueous SCES + X+) was prepared by mixing LiTFSA (TFSA- : (CF3SO2)2N-), XTFSA (X = Cs, K, Li) and H2O. Raman and attenuated total reflectance infrared spectroscopy (ATR-IR) were performed using a laser Raman spectrophotometer NRS-4500 and Fourier transform infrared spectrophotometer FT/IR-6000, respectively. Linear sweep voltammetry (LSV) measurements were conducted using Pt (anodic scan) and Al (cathodic scan) electrodes as working electrodes. Pt wire and saturated KCl silver chloride silver electrode (SSE) were used as a counter electrode and a reference electrode, respectively. The surface of the Al electrode after the measurement was observed with X-ray photoelectron spectroscopy (XPS). ALIB charge-discharge tests were performed by the in-situ electrochemical impedance spectroscopy2)3). LCO and LTO electrodes (16 mmφ) were used as positive and negative electrodes, respectively. The CR2032 coin cells were assembled with these electrode, GA-55 glass separator (17 mmφ) and the electrolyte solution. The in-situ EIS measurements were carried out at 45°C. The DC current was 1.6 mA (C-rate of 0.5C) and a small AC current was superimposed on DC current adjusted so that the response voltage amplitude was less than 5 mV. Electrochemical measurements were performed using an electrochemical measurement system (SP-150, Bio-Logic). According to the previous study4), Aqueous SCES has a unique liquid structure that coordinates not only water but also TFSA- coordinates to Li ions, which improves the oxidation resistance of water and widens the potential window on the reducing side due to SEI film formation. This indicates that the liquid structure plays a key role in driving ALIB. The broad OH stretching bands of water appeared at approximately 3500 cm-1 with the small shoulder at 3200 cm-1 in IR spectra for these aqueous SCES + X+. The intensity at 3200 cm-1 decreased with the addition of alkali salt, suggesting that the hydration structure and hydrogen bonding changed despite the addition of a small amount of alkali salt. The Raman band of TFSA- at 752 cm-1 was shifted to lower wavenumber as the Cs or K salt were added, suggesting that the addition of Cs+ and K+ metal salts changes not only the water molecules but also the structure around TFSA-. According to the LSV measurement results, there is no difference in oxidation stability among these aqueous SCES + X+. In contrast, the peaks assigned to SEI formation were observed in the cathodic polarization, and their peak positions differed depending on the sample. KF and CsF were formed on the Al electrode surface after the polarization measurements in the aqueous SCES + K+ and Cs+, respectively. In addition, a C-C bond peak was observed on the Al electrode surface measured in the aqueous SCES + Cs+, suggesting that a carbon-derived film is also formed. We believe that the difference in these films affects the battery performance. The coulombic efficiency of ALIB using the aqueous SCES with alkali metal ions after 50 cycles was higher than that of ALIB using the aqueous SCES, remaining above 70%. References1) N. Arai, H. Watanabe, E. Nozaki, et. al. J. Phys. Chem. Lett. 11, 4517−4523 (2020).2) Z. B. Stoynov, B. S. Savova-Stoynov, J. Electroanal. Chem., 183, 133 (1985).3) M. Itagaki, N. Kobari, S. Yotsuda, et, al. J. Power Sources, 135, 255 (2004).4) L. Suo, O. Borodin, T. Gao, et, al. Science. 350, 938-943, (2015).

Positive Electrode Behavior of Manganese Dioxide in Alkaline Aqueous Electrolyte Solution

Aqueous secondary batteries that use zinc as the negative electrode are considered suitable for automotive batteries, which require high safety, high energy density, and low cost. An aqueous battery using zinc for the negative electrode has long been put into practical use as a manganese primary battery using manganese dioxide (MnO2) for the positive electrode. Since MnO2 can reduce Mn4+ to Mn2+ in an aqueous electrolyte, if this reaction can be reversibly used, it may be a promising candidate material for the high-energy-density positive electrode of aqueous zinc secondary batteries. In this presentation, we report the results of a study of charge-discharge behavior of MnO2 positive electrode in alkaline aqueous electrolyte solutions used in primary manganese batteries. In this research, positive electrode performance was measured using a three-electrode method. A mixture of commercially available electrolytic manganese dioxide (EMD), acetylene black (AB) and Polytetrafluoroethylene (PTFE) was used as the working electrode. Zinc or Platinum plate was used as counter electrode, and Hg | HgO electrode was used as the reference electrode. The structural changes of the EMD and the identification of the reaction products were investigated by ex-situ XRD measurements. From the evaluation results of several samples, it was found that the EMD with a larger amount of structural water shows a higher electrochemical capacity. Furthermore, among the EMDs evaluated, it was found that the two-electron redox reaction of Mn proceeds reversibly in EMDs with a large amount of structural water. In the presentation, we will report on changes in the crystal structure of MnO2 due to Mn redox, changes in electrolyte composition, and the effects of electrolyte composition on performance.Acknowledgments： This research was conducted under the project "Development of Innovative Storage Batteries for Electric Vehicles (RISING3)" (JPNP21006) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). We would like to express our gratitude to all parties involved.

Oxygen Evolution Reaction Activity of Highly Crystalline Hydrated Cobalt Oxyhydroxide Synthesized with Soft Chemistry

Introduction Zinc-air secondary batteries are expected to have high energy density because oxygen in ambient air can be used as the active material. They are also expected to satisfy high safety standards owing to the aqueous electrolyte solutions and open structure. In addition, low cost is expected since zinc is a relatively cheap metal compared to lithium. Because of these features, Zinc-air secondary batteries are attracting attention as a next-generation large-scale energy storage device. One of the challenges for commercializing this battery system is the low energy conversion efficiency caused by the large overvoltage of the air electrode. To solve this problem, oxygen evolution reaction (OER) catalysts have been intensively researched, and Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and Ca2FeCoO5 (CFCO) have been developed as OER catalysts having higher activity than conventional noble metal oxide catalysts. Since the active sites of BSCF and CFCO are reported as partially Fe-substituted CoOOH phases1,2, it is essential to understand OER characteristics of partially Fe-substituted CoOOH phases. However, the effects of the crystallinity and Fe-substitution ratio on OER activity have not been clarified. This is mainly because metastable hydrated CoOOH is conventionally synthesized at relatively low temperatures. On the other hand, we have successfully synthesized highly crystalline hydrated NixFe1–xOOH using soft chemistry and clarified the effect of crystallinity and Fe-substitution ratio on the OER activity3. In this study, we synthesized highly crystalline hydrated CoOOH using soft chemistry and evaluate its OER activity to elucidate factors controlling it. Experimental Hydrated CoOOH was synthesized with two-step soft chemistry following the report by Sakurai et al. 4. First, Na0.74CoO2 was obtained by calcination of Co3O4:Na2CO3 =40:60 mol% at 900 °C for 12 h. Then, synthesized Na0.74CoO2 was stirred in 7.8 mmol dm–3 Br2 / CH3CN to obtain Na0.358CoO2 by extracting Na. Finally, Na0.358CoO2 was hydrated by refluxing with ultra-pure water at 100 °C for 24 h. The synthesized samples were characterized with powder X-ray diffraction (XRD). Results and discussion Figure 1 shows a XRD pattern of the synthesized sample. Though relatively broad unidentified peak is observed at around 8 °, the diffraction pattern of hydrated CoOOH is observed as a main phase. Its OER performance in an aqueous solution of KOH will be presented at the site.References1) K. J. May, C. E. Carlton, K. A. Stoerzinger, M. Risch, J. Suntivich, Y. L. Lee, A. Grimaud, Y. S. Horn, J. Phys. Chem. Lett., 3, 3264 (2012).2) E. Tsuji, T. Motohashi, H. Noda, D. Kowalski, Y. Aoki, H. Tanida, J. Niikura, Y. Koyama,M. Mori,H. Arai,T. Ioroi,N. Fujiwara,Y. Uchimoto,Z. Ogumi, H. Habazaki., ChemSusChem., 10, 2864 (2017).3) A. Ikezawa, S. Koito, H. Arai, Abs.#1I23, The 90th ECSJ Annual Meeting (2023).4) H. Sakurai, K. Takada, T. Sasaki, F. Izumi, R. A. Dilanian, E. Takayama-Muromachi, J Phys. Soc. Jpn., 73, 2590 (2004).This work was partially supported by JRP-LEAD with DFG (JPJSJRP20221602) Figure 1

Fundamentals and Implication of Point of Zero Charge (PZC) Determination for Activated Carbons in Aqueous Electrolytes.

The point of zero charge (PZC) is a crucial parameter for investigating the charge storage mechanisms in energy storage systems at the molecular level. This paper presents findings from three different electrochemical techniques, compared for the first time: cyclic voltammetry (CV), staircase potentio electrochemical impedance spectroscopy (SPEIS), and step potential electrochemical spectroscopy (SPECS), for two activated carbons (ACs) with 0.1molL-1 aqueous solution of LiNO3, Li2SO4, and KI. The charging process of AC operating in aqueous electrolytes appears as a complex phenomenon - all ionic species take an active part in electric double-layer formation and the ion-mixing zone covers a wide potential region. Therefore, the so-called PZC should not be considered as an absolute one-point potential value, but rather as a range of zero charge (RZC). SPECS technique is found to be a universal and fast method for determining RZC, as applied here together with the EQCM. In most cases, the RZC covers a potential range from ≈100 to ≈200mV and the correlation of the range with the carbon microtexture is clear, highlighting the role of the ion-sieving effect. It is postulated that PZC for porous materials in aqueous electrolytic solutions should be considered instead as RZC.

Sorption-desorption of rare earth metal cations by ferromanganese crusts of Govorov’s guyote of the Magellanic Mountains of the Pacific Ocean

The article presents the results of experimental studies on the sorption and desorption of rare earth metal (REM) cations by cobalt-rich ferromanganese crusts (CMC) of Govorov’s guyot. It has been established that the sorption of REM cations occurs on the ore minerals KMK – Fe-vernadite, vernadite, Mn-feroxygite, goethite. The crusts are characterized by a high exchange capacity – 1.78–3.57 mg-eq/g, which increases in a series: (Dy Gd Lu Sm Nd Y, La Eu) Ce. The sorption of REM cations proceeds by an ion exchange equivalent irreversible mechanism. The exchange complex of ore minerals consists of Na+, K+, Ca2+, Mg2+ cations, which contribute 97‒98% to their total capacity. The crusts are characterized by the group sorption of REM cations from multicomponent aqueous solutions of metal salts. The selectivity of ore manganese and ferruginous minerals of crusts to REM cations is significantly higher than to the main cations of ocean water. From experimental data on the desorption of sorbed REM cations with NaCl solution, their irreversible absorption by ore minerals follows, and the strengthening of the chemical bond of sorbed REM cations with the main structural elements of these minerals over time. An important property of ore minerals, primarily manganese minerals, is their chemical and structural stability in aqueous solutions of electrolytes. This suggests the repeated use of ferromanganese crusts as sorbents of REM cations.

Modified Debye-Hückel-Onsager theory for electrical conductivity in aqueous electrolyte solutions: Account of ionic charge nonlocality.

This paper presents a mean field theory of electrolyte solutions, extending the classical Debye-Hückel-Onsager theory to provide a detailed description of the electrical conductivity in strong electrolyte solutions. The theory systematically incorporates the effects of ion specificity, such as steric interactions, hydration of ions, and their spatial charge distributions, into the mean-field framework. This allows for the calculation of ion mobility and electrical conductivity, while accounting for relaxation and hydrodynamic phenomena. At low concentrations, the model reproduces the well-known Kohlrausch's limiting law. Using the exponential (Slater-type) charge distribution function for solvated ions, we demonstrate that experimental data on the electrical conductivity of aqueous 1:1, 2:1, and 3:1 electrolyte solutions can be approximated over a broad concentration range by adjusting a single free parameter representing the spatial scale of the nonlocal ion charge distribution. Using the fitted value of this parameter at 298.15K, we obtain good agreement with the available experimental data when calculating electrical conductivity across different temperatures. We also analyze the effects of temperature and electrolyte concentration on the relaxation and electrophoretic contributions to total electrical conductivity, explaining the underlying physical mechanisms responsible for the observed behavior.

Ion-Specific Surface Tension of Aqueous Electrolyte Solutions: Analytical Insights from a Restricted Primitive Model.

The ion-specific surface tension of aqueous electrolyte solutions is of fundamental importance in physical chemistry, solution chemistry, electrochemistry, and biochemistry, yet it remains a challenge to be qualitatively predicted. In this work, an analytical theory of ion-specific surface tension is developed. By modeling the solution to a restricted primitive model (RPM), the surface tension increment of the electrolyte solution reduces to the surface tension of the RPM, which is further determined analytically by using the integral equation theory and the morphological thermodynamics theory. According to our formula, the surface tension increment of the electrolyte solution consists of a dominant and positive hard sphere contribution, which depends on the salt concentration, and a secondary electrostatic contribution, which depends on the inverse Debye length and the salt concentration. Our theory is applied to 1:1, 2:2, 1:2, 2:1, 3:1, and 3:2 electrolyte solutions with typical salt concentrations up to several mol/L and compared with experimental data. Without introducing any adjustable parameters, our theory leads to a good prediction of the surface tension increment of more than 50 kinds of aqueous solutions. Such a good agreement demonstrates the great potential of our theory for a fundamental understanding of specific ion effects in a variety of electrolyte solutions.

Derivation of the General Equation of State for a Doped Semiconductor. The Equation is Solved Concerning the Electron Concentration in the Conduction Band for Different Concentrations and Properties of Doping Substances

The paper examines the state of a system consisting of a crystalline semiconductor doped with donor and acceptor impurities. The General Equation of State of the system is derived. Methods are proposed to solve the general equation for the concentration of electrons or holes in a semiconductor. The identity of the General Equations of State of semiconductors and aqueous solutions of electrolytes is discussed. An assumption is made about the practical application of the found relationships.