Investigation of interfacial proton transport is necessary to elucidate biological systems. As commonly found in biomaterials, the carboxylic acid group was proven to act as a proton-conducting group. This study investigated the influence of carboxylic acid concentration on both interfacial and internal proton transport. Several styrene-based polymers containing the carboxylic acid group were synthesized. The amount of carboxylic acid group in the polymer chain was varied to explore the effects of weak acid concentration on polymer thin films’ electrical properties. The IR p-polarized multiple-angle incidence resolution spectrometry (pMAIR) spectra show the higher ratio of the free carboxylic acid groups rather than cyclic dimers in polymers with a higher concentration of carboxylic acid group, facilitating the more hydrogen bonding networks in films. The water uptake results reveal the similar number of adsorbed water molecules per carboxylic acid group in all thin films. Remarkably, polymer thin films with high carboxylic acid concentration provide internal proton conduction because of the relative increase in the amount of the free carboxylic acid group. In contrast, interfacial proton conduction was found in low carboxylic acid concentration polymers because of the relatively large amount of cyclic dimer carboxylic acid group and poor amount of free carboxylic acid group. This study provides insight into interfacial proton transport behavior according to the weak acid concentration, which might explain proton transport in biological systems.

In this work, we report a simple electrochemical sensor that detects proteinuria upon immersion into a sample. We immobilized peptidases in conjunction with glutamate oxidase (GluOx) on a Prussian blue-modified glassy carbon (PB-GC) electrode. In the sensor, albumin, which is a major protein in urine, was degraded by peptidases to produce glutamate that was detected by GluOx on PB-GC. Initially, we validated the strategy for the detection of proteinuria using glutamate sensing. We quantified the amount of glutamate produced by degrading human serum albumin with HCl and carboxypeptidase A (CPA). The results indicated that an increase in the enzyme degradation rate was necessary for daily proteinuria sensing that needs to be completed within 1 h. Therefore, we investigated the use of endopeptidase in conjunction with CPA. The combination of proteinase K and CPA liberated glutamate from albumin at 17.5 times higher comparing to solely CPA. The subsequent glutamate assay using peptidase-modified GluOx-PB-GC electrode did not exhibit changes in the electrochemical signal with increases in the glutamate concentration, because peptidase degraded the GluOx on the modified electrode. To prevent this, GluOx was encapsulated in ZIF-8. Glutamate was successfully detected using peptidase and GluOx encapsulated in the ZIF-8-modified PB-GC (peptidase-ZIF-8/GluOx-PB-GC) electrode. Finally, an albumin assay was performed using the peptidase-ZIF-8/GluOx-PB-GC electrode, wherein albumin was detected with a sensitivity of 0.1 mg/mL within 30 min. Our simple and easy-to-use method for albumin detection provides a viable sensor for daily urinalysis.

A safe and low-cost aqueous electrolyte, in which maximum amount of sodium trifluoroacetate (NaTFA) is dissolved (26 mol kg⁻¹), showed high ionic conductivity of 23 mS cm⁻¹ and provided wide electrochemical stability window of 3.1 V. These attractive features may originate from so-called “water-in-salt” effect of the highly concentrated electrolyte in addition to a robust fluoride layer formed on anode thereof. This novel electrolyte enabled reversible operation of NASICON-type Na₂VTi(PO₄)₃ as symmetrical operation based on V^3+/4+ at cathode and Ti^3+/4+ and V^2+/3+ at anode, respectively.

The aim of this study is to observe the spatial inhomogeneity of a rechargeable battery’s electric conductivity distribution. Therefore, we have developed a system that uses the measurement results of a minute magnetic field that leaks from the cell to visualize, in real time, the cell’s electric conductivity distribution. This system has a magnetic detection capability of 30 pT/Hz^0.5 (at 1 Hz); it measures the magnetic field distribution in the 240 × 240-mm range. This system has the ability to detect the 500-µA electric current that flows in a rechargeable battery 5 mm away from the sensor module. Because the magnetic signals are detected at the frequency synchronized with the alternating current flowing in the cell, this system is not affected by environmental magnetic field noise. Using this system, we have successfully visualized the short-circuit spot in a cell with significant self-discharge. Furthermore, we observe that the magnetic field distribution changes continually when the short circuit is being generated. The coordinate where the magnetic field distribution changed and the coordinate where metal precipitates were confirmed significant agreement.

An oxide-ion-conductor-based oxygen pumping system can serve as an on-site oxygen separation system. Herein, we present the oxygen permeation capability of a Pt electrode/La-Sm-doped CeO₂ (L-SDC) intermediate layer/c-axis-oriented La_9.66Si_5.3B_0.7O_26.14 (c-LSBO) solid electrolyte cell. A significant increase in the oxygen permeation flux is observed on applying a DC voltage of ≥4 V at temperatures <600 °C. A remarkably high flux of 5.2 mL cm⁻² min⁻¹ is obtained even at 500 °C. Furthermore, in situ X-ray diffraction studies under applied voltages reveal an increase in the lattice constant of L-SDC, accompanied by a drastic increase in the oxygen permeation flux, indicating the reduction of Ce⁴⁺ and formation of oxygen vacancies. These results suggest that the observed change in L-SDC under the applied voltage results in the in situ formation of a mixed electron- and oxide-ion-conducting L-SDC electrode, indicating that the oxygen reduction reaction and incorporation is significantly enhanced.

An effect of crystallinity of graphite on formation of graphite intercalation compounds (GICs) and reversibility in K cells was studied by comparing that in Li cells. Though high reversible capacities and coulombic efficiencies of graphite electrodes in K cells were achieved during initial cycles regardless of the crystallinity, high crystallinity graphite demonstrated less potential-hysteresis and superior capacity retention to low crystallinity graphite. Operando XRD measurement confirmed similar staging process of K-GICs for both graphite, however, high crystallinity graphite transformed into higher crystallinity of K-GIC as well as higher reversibility of potassium de-/intercalation than low crystallinity graphite. A turbostratic disorder in low crystallinity graphite led to redox-potential split and lower crystalline K-GIC and potassium-extracted graphite. Thus, the crystallinity of graphite, which includes coherence length and the degree of random stacking, is found to be a predominant factor for highly reversible potassium intercalation, which differs from the lithium case. We concluded that the high crystallinity is of importance for the application of graphite to long-life potassium-ion batteries.

In this study, we experimentally measure the viscosity, η, and ionic conductivity, σ, of 1 mol kg⁻¹ LiPF₆ dissolved in a binary solvent of ethylene carbonate (EC) and propylene carbonate (PC) by varying the EC content from 0 to 60 vol%. Replacing EC with PC does not significantly influence on the mechanism of flow and ionic conduction. The state of solvent solvating to Li⁺ is analyzed using Raman spectra and ¹³C-NMR; the quantitative analysis suggests that the preference of EC in the Li⁺ solvation shell is almost similar to that of PC. The diffusion coefficient, D, of each species, Li⁺, PF₆⁻, EC, and PC, is determined by pulse-gradient spin-echo NMR. In the electrolyte system dealt in this study, the molar conductivity is dominated by only the D of the charge carriers. The hydrodynamic Stokes radius of all constituent species is expressed in terms of D and η using the Stokes–Einstein relation. As for coordinated-Li⁺, a comparison between the Stokes radius and the van der Waals radius or the radius considering the free volume suggests that Li⁺ diffuses while dragging not only a coordination shell that can be spectroscopically detected but also an outer shell that binds loosely to Li⁺.

Given the problems of high energy consumption, low resource utilization, and severe environmental pollution in traditional electrolytic manganese or manganese dioxide, this study puts forth a single-membrane double-chamber electrolysis method for the cathodic electrodeposition of manganese. Anode co-production of electrolytic manganese dioxide and recovery of sulfuric acid in the anode chamber enable efficient recovery and utilization of resources. The effects of Mn²⁺ concentration, current density, electrolysis temperature, cathode (NH₄)₂SO₄, and anode H₂SO₄ concentration on electrodeposition were investigated. At the cathode concentration of 40 g/L Mn²⁺, initial pH = 7.0, 120 g/L (NH₄)₂SO₄, current density 400 A/m²; and anode concentration of 40 g/L Mn²⁺, 0.6 mol/L H₂SO₄, current density 800 A/m², 60 mm plate spacing, electrolysis temperature of 40 °C, and electrolysis time of 6 h; the yield of manganese dioxide reached 75.1 %, electrolytic manganese dioxide yield was 23.6 %, acid recovery was 62.3 %, and the energy consumption was 5701 kW h t⁻¹. The surface of metal manganese produced at the cathode was smooth and dense, with a silver-white metallic luster and uniform growth of each phase. The electrolytic manganese dioxide (EMD) of the anode product was α-MnO₂, and its microstructure was characterized by a spherical particle structure. The particle size was uniform and showed a honeycomb structure. Thus, the application of a single-membrane double-chamber manganese production system can effectively solve the environmental pollution caused by heavy metal wastewater and provide efficient recovery and utilization of resources, which has good economic and social benefits.

Ionic liquids (ILs) possess low volatility and low flammability and are promising electrolytes for thermally stable Li-ion batteries (LIBs). Among ILs, bis(fluorosulfonyl)imide (FSI⁻) anion-based ILs have low viscosity and high ionic conductivity and FSI-based electrolytes are useful for achieving a high power density LIB. In this study, we investigated the effects of LiFSI concentration in IL electrolytes on the performance of LIBs. We prepared electrolytes composed of 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl)imide (EMImFSI) and LiFSI. The ionic conductivity of the electrolyte decreased with increasing LiFSI concentration due to an increase in viscosity; however, the Li⁺ transference number increased with increasing LiFSI concentration. The IL electrolyte was tested in a LiNi_0.5Mn_0.3Co_0.2O₂/graphite pouch cell. The discharge rate capability of the cell was improved by increasing the LiFSI concentration. The higher LiFSI concentration was effective in suppressing the depletion of Li⁺ in the vicinity of the cathode during the high current discharge. Furthermore, we demonstrated that cells with IL electrolytes can be stably operated over 500 charge-discharge cycles at 25 °C and 60 °C.

The properties exhibited by Ni-rich cathode materials were enhanced through the mixed coating layers of Li₃PO₄ and boric acid. The scanning electron microscopy (SEM), the transmission electron microscope (TEM), the differential scanning calorimetry (DSC), the Electrochemical Impedance Spectroscopy (EIS), as well as the half-cell and full-cell charge-discharge tests were adopted for characterizing the structure and electrochemical properties exhibited by the cathode materials. As revealed by results, the Li₃PO₄ and boric mixed coating layers can effectively reduce the surface area and protect the direct contact between cathode material particle surface and electrolyte, meanwhile improving the structural stability and cycle performance. The coating of fast ionic conductor contributes to enhance the specific capacity possessed by the Ni-rich cathode materials accordingly.

Salinity gradient energy generated by the contact between seawater and river water is one of the promising renewable energies. In the reverse electrodialysis (RED), salinity gradient energy is directly translated into the electricity. The representative problem is a large electrical resistance of river water or dilute solutions. The dilute solutions are poor electrically conductive. This results in a huge energy loss when an electrical current passes through it.

In this study, sodium chloride (NaCl) or poly(sodium 4-styrenesulfonate) (NaPSS) was added to the dilute solutions to increase the conductivities and enhance the power outputs of the RED cells. When NaCl was added, the power output reached 11.4 ± 0.6 µW. On the other hand, when NaPSS was added, the power output increased up to 19.6 ± 0.6 µW.

Potential barrier plays a key role in ionic transport through nanoporous membranes. We numerically study the contribution of the potential barrier to the ionic current through a cylindrical Si₃N₄ nanopore using molecular dynamics simulations. We extract the height of the potential barrier from the best fit using a simple polynomial model of the ionic current. We reveal that the surface atoms make a contribution to the potential barrier. This study provides the height of the potential barrier so that it is valuable information about the underlying mechanism of ionic transport through nanopores.

Electrochemical fluorination of triphenylmethane derivatives and bis(phenylthio)diphenylmethane derivatives by using a split bipolar electrode is described. The reaction conditions for the fluorination of triphenylmethane were further optimized from the previous report to obtain the desired product in quantitative yields. Fluorination reaction cleanly proceeded under a wide range of voltage applied between the driving electrodes, from 25 to 100 V. Use of lower voltage is preferable in terms of energy efficiency, whereas higher voltage shortened the reaction time. The optimized conditions were applicable to the fluorination of other triphenylmethane derivatives and bis(phenylthio)diphenylmethane derivatives to give the corresponding fluorinated products.

We have previously reported that a three-fold increase in lithium-ion conduction can be achieved on LATP (Li_1.3Al_0.3Ti_1.7(PO₄)₃) by dispersing LaPO₄ particles through the co-sintering of LATP with 4 wt% of LLTO (Li_0.348La_0.55TiO₃). However, the LaPO₄ formation during sintering has been detected only by means of XRD and back-scattered SEM, and precise morphology of LaPO₄ particles as well as LATP/LaPO₄ interface have still been uncertain. In the present study, we carried out TEM experiments on the LaPO₄-dispersed LATP composite to investigate the detailed microstructure and compositions of the dispersed LaPO₄ particles and surrounding LATP matrix. HR-TEM coupled with EDS reveals that LaPO₄ particle attains an intimate contact with the LATP matrix, which would allow the formation of space charge layer at the interface to enhance the conductivity.