Kind Of Electrolyte Research Articles

Effect of flame retardant hexafluorocyclotriphosphazene on combustion characteristics of electrolyte for lithium-ion batteries

Hexafluorocyclotriphosphazene (HFPN) is a promising flame retardant to be applied in lithium-ion batteries (LIBs) to decrease the fire risk during the treatment of electrolyte. In this manuscript, the influence of HFPN on the combustion characteristics of LIB electrolyte was investigated, the combustion behaviors and flame retardancy of the electrolyte with or without HFPN were systematically studied by using cone calorimeter, flash point meter and a series of standard equipment, as well as self-made water spray fire extinguishing platform. The flash points of 3 kinds of control group as base solution and 3 kinds of flame-retarded electrolyte were measured and obtained by SCKB3000 closed cup automatic flash point tester. The combustion characteristics of 6 types of electrolytes were analyzed by a cone calorimeter. The heat release rate (HRR), fire growth index (FGI), fire magnitude index (FMI) and other important combustion parameters of the electrolytes were studied. Based on the self-made water mist fire extinguishing platform, the fire extinguishing effect on 6 kinds of electrolytes under the same water mist condition was compared, and the influence of flame retardants in the fire extinguishing process was analyzed. The results showed that the change of flash point was obviously related to the composition of electrolyte. Flame retardant could reduce the peak HRR (pHRR) during electrolyte fire to a large extent, while it could also prolong the combustion duration of electrolyte pool fire. Under the action of fine water mist, the electrolyte pool fire would quickly extinguish, but there would remain a lot of smoke.

All Wood‐Based Water Evaporation‐Induced Electricity Generator

AbstractWater evaporation‐induced electricity generators (WEIGs) are promising as self‐powered electronic devices, as they can harvest green, small‐grade, and ubiquitous hydrovoltaic energy in ambient environment to electricity. Here, biodegradable wood‐based WEIGs with high performance are reported by removing lignin and hemicellulose from balsa wood (BW) with more exposed cellulose nanofibrils. Delignified BW (DBW) and cellulosic BW (CBW) display significant enhance in open circuit potential (Voc) and short circuit current (Isc) due to increased specific surface area, hydrophilicity, and surface charge density. The electricity‐generating performance of CBW‐based WEIG (CBWG) is not stable due to its structural collapse. DBW‐based WEIG (DBWG) shows a steady electricity output and fast responsivity to ambient environments, such as humidity, temperature, light, and wind. Therefore, DBWGs can be employed as self‐powered environmental sensors. The effects of different kinds of electrolytes with varied concentrations on the performance of DBWG are also studied. The DBWG (40 mm × 40 mm × 2 mm) displays a Voc of 0.77 V and Isc of 148 µA in 1.2 m CaCl2 solution. In this study, all wood‐based sustainable WEIGs with high electricity generating performance are facilely prepared and are promising for remote self‐powered environmental sensors and power sources.

Influence of electrical polarization on thrombogenicity of titania nanotubes

AbstractThe development of hemocompatible biomaterials with antithrombogenic surface coatings remains a challenge in cardiovascular applications. There is interest in negatively charged surfaces that inhibit thrombus formation through electrostatic repulsion between the biomaterial surface and negatively charged platelets. Hence, the present study investigated the influence of electrical polarization on the thrombogenicity of titania nanotubes (TNT), which are promising candidates for inhibiting thrombogenicity via surface modification. TNTs were formed on commercially pure titanium plate by the electrochemical anodization technique using platinum as a counter electrode at 60 V for 24 h with two kinds of electrolytes (hydrofluoric acid diluted with dimethyl sulfoxide [D‐TNT] or ethylene glycol [E‐TNT]) followed by an annealing at 540°C for 3 h in air. Both TNTs were mixture of anatase and rutile, and the D‐TNT had a diameter of 108.76 ± 2.55 nm and the E‐TNT, 53.833 ± 2.42 nm. The TNTs were electrically polarized at 100 V of DC field and 400°C for 1 h. Water contact angle measurements showed that the non‐polarized (0‐) TNT surface was hydrophilic whereas the positively (P‐) or negatively (N‐) polarized TNT surfaces showed high‐hydrophilicity. Antithrombogenicity was evaluated using the thrombus coverage area ratio (TCAR) after soaking the TNTs in bovine whole blood. The TCARs for 0‐polarized E‐ and D‐TNTs were 5.30 ± 4.34% and 36.3 ± 5.8% and for P‐polarized E‐TNT and D‐TNT were 1.50 ± 0.77% and 2.76 ± 1.07%, whereas no thrombus formation (0 ± 0%) for N‐polarized E‐TNT and very few thrombus formation (0.12 ± 0.22%) for N‐polarized D‐TNT. The electrostatic repulsion between the N‐polarized E‐TNTs and platelets completely inhibits thrombus formation, which cannot be achieved by the nanomorphology and high‐hydrophilicity of other TNTs. Hence, N‐TNTs formed by electrical polarization are potential candidates for cardiovascular devices, such as artificial heart valves with long‐term hemocompatibility.

ZIF-8 induced N, P double doped porous molybdenum phosphide hydrogen evolution catalyst

Molybdenum based phosphides have gradually become the investigation frontier of hydrogen evolution catalysts due to the platinum like electronic structure. In this paper, N, P double-doped graphite carbon layers wrapped with MoP nanoparticles (P–MoP@NPC), is directly compounded by one-step high-temperature carboning PMo12-APP@ZIF-8 precursor. P–MoP@NPC possesses splendid hydrogen production reactive, in two kinds of electrolytes, when the overpotentials of P–MoP@NPC are 132 mV and 161 mV, the slope of current density reaching 10 mA cm−2, Tafel slope are 67 and 79 mV dec−1, respectively. In the bargain, P–MoP@NPC displays satisfactory durability in acid and alkaline mediums and can continue to work for more than 24 h. The wonderful hydrogen production ability of P–MoP@NPC is ascribed to the synergistic effect of MoP nanoparticles, hierarchical porous structure as well as N, P double-doped carbon layers. The confinement effect of ZIF-8 makes most of the synthesized MoP nanoparticles evenly distributed. The hierarchical porous structure caused by the volatilization of Zn atoms with high temperature can expose more active centers. The N, P double-doped graphitic carbon layers not only protect the catalyst but also adjust the electronic structure of MoP, promoting the hydrogen production capacity. This work may provide a general way to study molybdenum phosphide catalysts synthesized by APP as a green phosphorus source for energy conversion.

Formation of zinc selenite nanostructures in SiO2/Si track templates with the use of two kinds of electrolytes

This paper presents studies of zinc selenite nanocrystals obtained by chemical and electrochemical deposition of zinc in a silicon dioxide track template. With the use of two kinds of electrolytes, zinc selenite nanocrystals were prepared by template synthesis and their morphological, structural and photoluminescent properties were investigated. The electrochemical deposition method was shown to be more optimal to create this crystal in comparison to the chemical deposition method. The cell parameters created by us match up with the results of other authors. Photoluminescence spectra were recorded in the spectrum interval from 2 to 4 eV at room temperature at an excitation wavelength of ~ 4 eV.

Mg(TFSI)2-Based Solid-State Eutectic Electrolyte Towards Safer Magnesium Batteries

Magnesium (Mg) batteries are regarded as safer alternatives for Li+-dominated batteries by virtue of the unique dendrite-free property of Mg element. However, traditional liquid electrolytes applied in Mg batteries are mainly based on chloride salts and highly flammable organic solvents, which might cause numerous safety issues such as fire, electrochemical corrosion, and leakage of hazardous chemicals. These kinds of electrolytes seriously violate the original purpose of developing Mg-based batteries. Therefore, exploring non-flammable chloride-free solid-state electrolytes is of significant importance for realizing safer Mg batteries. Here in this work, a novel non-flammable eutectic electrolyte based on chloride-free Mg(TFSI)2 salt is first proposed as a solid electrolyte for safer Mg metal batteries. Our recent results demonstrate that compared with traditional Mg(TFSI)2-based electrolytes which dissolve in flammable organic solvents such as EC, PC, and THF solvent, this Mg(TFSI)2-based eutectic solid electrolyte is non-flammable with robust mechanical structures. When applied in Mg//Mg symmetric batteries, this novel eutectic solid electrolyte could greatly suppress the overpotential phenomenon that occurs in traditional Mg-based electrolytes and achieves stable Mg plating/stripping reversibility with more than 150 h. Furthermore, the practical feasibility of this eutectic solid electrolyte is also demonstrated in Mg//V2O5 full cell, which shows competitive electrochemical performance. We believe that the research on such new electrolytes could provide a new strategy for developing safe and sustainable Mg-based batteries.

Silicon-Containing Anodes for High-Energy Density Lithium-Ion Batteries

Next- Generation Lithium(Li)-based rechargeable battery technologies utilising silicon (Si) and Si-containing (Si/Gr, SiOx/Gr, SiNx etc.) anodes coupled with high-capacity/high-voltage insertion-type cathodes (IC) have gained significant attention from both academic and industrial sectors.1 This originates from their practically achievable high energy density, offering a new possibility towards the large-scale espousal of electric vehicles and effective integration of renewable energy sources. In pursuit of designing such high-energy-density electrical energy storage devices, the anode compartment plays huge role and has accordingly reaped increasing interest. In this regards, Si and Si-containing materials are considered to be the most promising choices to replace state-of-the-art graphite in the construction of Lithium-ion batteries (LIBs). This is attributed to their unparalleled high theoretical capacity, suitable operating voltage, natural abundance, environmental benignity, nontoxicity, high safety, and so forth.However, Si and Si-containing materials are endowed with their own advantages and inherent shortcomings. Colossal volume change, much lower diffusivity (σe-+ and DLi+), unstable and fragile solid electrolyte interphase (SEI) formation, electrode swelling, and electrolyte drying are among the most impending intrinsic challenges that hider the large-scale commercialization of such innovative materials. Moreover, the detailed storage mechanism, electrochemistry, failure mechanism and impact of each component in case of blended/composite anode materials (e.g., Si/Gr and SiOX/Gr) etc. remain to be key loopholes to fully understand and thus enable the systems.In this paper, accounts on the various Si-containing active materials (Si, SiOx, Si/Gr blend/composite, SiOx/Gr blend/composite, SiNx etc) including their pros and cons, recent progresses, detailed storage chemistries and mechanisms, characteristics, possible tailored remedies to evade their challenges and thus improving performances - in hope of facilitating their large-scale deployment in the market, and future prospects and research directions will be presented. Impact of atomic level peculiar properties on the material and battery cells level key performance matrices are thoroughly examined. Moreover, the specific energy (Eg) and energy (Ev) density of various insertion-type cathode materials as a function of a) the weight fraction of Si at a fixed areal capacity, b) areal capacity at various Si contents, c) various kinds of electrolytes (liquid, polymer, glass and ceramic) at a fixed areal capacity, and d) electrolyte thickness are evaluated and analyzed.The approach presented in this paper will spur new concepts and perspectives into the best use of Silicon (Si) and Si-containing anode materials for the development Next-Generation high-energy density LIBs. 1Eshetu, G. G.; Zhang, H.; Judez, X.; Adenusi, H.; Armand, M.; Passerini, S.; Figgemeier, E, “Gebrekidan Gebresilassie Eshetu, Heng Zhang, Xabier Judez, Henry Adenusi, Michel Armand, Stefano Passerini, & Egbert Figgemeier, “Production of high-energy Li-ion batteries comprising silicon-containing anodes and insertion-type cathodes.” Nat. Commun. 2021, 12 (1), 1–14.

Lithium Manganese Sulfates as a New Class of Supercapattery Materials at Elevated Temperatures.

To make supercapattery devices feasible, there is an urgent need to find electrode materials that exhibit a hybrid mechanism of energy storage. Herein, we provide a first report on the capability of lithium manganese sulfates to be used as supercapattery materials at elevated temperatures. Two compositions are studied: monoclinic Li2Mn(SO4)2 and orthorhombic Li2Mn2(SO4)3, which are prepared by a freeze-drying method followed by heat treatment at 500 °C. The electrochemical performance of sulfate electrodes is evaluated in lithium-ion cells using two types of electrolytes: conventional carbonate-based electrolytes and ionic liquid IL ones. The electrochemical measurements are carried out in the temperature range of 20-60 °C. The stability of sulfate electrodes after cycling is monitored by in-situ Raman spectroscopy and ex-situ XRD and TEM analysis. It is found that sulfate salts store Li+ by a hybrid mechanism that depends on the kind of electrolyte used and the recording temperature. Li2Mn(SO4)2 outperforms Li2Mn2(SO4)3 and displays excellent electrochemical properties at elevated temperatures: at 60 °C, the energy density reaches 280 Wh/kg at a power density of 11,000 W/kg. During cell cycling, there is a transformation of the Li-rich salt, Li2Mn(SO4)2, into a defective Li-poor one, Li2Mn2(SO4)3, which appears to be responsible for the improved storage properties. The data reveals that Li2Mn(SO4)2 is a prospective candidate for supercapacitor electrode materials at elevated temperatures.

Nanoporous Copper Ribbons Prepared By Chemical Dealloying of a Melt-Spun Zn-Cu Alloy

Dealloying process is a powerful and versatile method to fabricate three-dimensional nanoporous (np) materials for applications in electrochemical synthesis, sensors, and catalysis. In the last years, several morphologies of np-copper and their dealloying mechanisms have been reported in alkaline and acidic media.[1-4] For instance, the nature of anions such as chloride and phosphate strongly influence the ligament size of np-Cu. The effects of several experimental parameters to control the structural and chemical properties of np-Cu materials via dealloying are not fully understood to date.In our work, Zn80Cu20 alloy ribbons prepared by melt-spinning were dealloyed by free corrosion in 0.1 M HCl and 1.3 M NaOH solutions. Both the surface and cross-section of the obtained np-Cu ribbons were comprehensively characterized by SEM, EDX, STEM, XRD, and XPS. Our results show a clear relation between dealloying conditions (pH, kind of electrolyte and reaction time) and structural parameters (ligament size and chemical composition) for np-Cu ribbons. The ligament size is strongly coupled with the residual Zn content prepared by dealloying in acidic environment. In contrast, the ligaments produced in alkaline media are much smaller, whereas the residual Zn content can be tuned in a broad range without changes in ligament size. For the first time, we point out the distribution of residual Zn within single ligaments of np-Cu. We suggest that the Cu surface atoms diffuse and capture the Zn atoms which are located in the near-subsurface during dealloying. Therefore, the Zn-rich regions seem to be relicts of the master alloy. We have also evaluated the time-resolved evolution of porosity within the ribbons via cross-section analysis. Despite the relatively thick melt-spun ribbons (35 ± 3 μm), kinetics of a bicontinuous ligament-pore structure are controlled by the interfacial process instead of the diffusion of corrosive electrolyte solution in and out of the porous layers, referred to as long-range mass transport. Surface diffusivities of Cu at 25 °C were determined to be 1.4 × 10−18 and 9.4 × 10−21 m2 s−1 in 0.1 M HCl and 1.3 M NaOH, respectively. Therefore, the high Cu surface diffusion rate in the presence of chloride ions enables an enhanced dealloying front propagation into the ribbons, and also coarsening of the ligaments to form larger ligament. On the contrary, the slow surface diffusion rate of Cu (hydr)oxide in 1.3 M NaOH solution strongly limits the dealloying process and forms smaller ligaments. Moreover, dealloying temperature strongly influences the surface diffusivity of Cu, leading to a strong relationship between dealloying temperature and the np-Cu structure. The electrochemically active surface area of np-Cu ribbons was determined by double layer capacity method. The catalytic properties of the np-Cu ribbons were then evaluated for organic electro-synthesis of cyclic carbonates from CO2 and epoxide. The yield of cyclic carbonate could be improved by using np-Cu ribbons for the activation of CO2.Based on our results, we provide deeper insights to the formation processes of np-Cu ribbons with tunable ligament size and Zn content in various electrolyte environments and its application as electrode material for electro-synthesis of cyclic carbonates formation from CO2 and epoxide.

Electrochemical behaviors and electrochemical performances of lithium-selenium battery using selenium/carbon as cathode in different electrolytes

Lithium-selenium (Li-Se) battery with high theoretical volume energy density (3253 mA h cm -3 ) is a very promising next-generation energy storge system, however, it still faces the problems of polyselenide generation and dissolution, as well as low active material utilization. Herein, electrochemical performance of Se/carbon cathode for Li-Se battery in three kinds of electrolytes, e.g. , ether-based, ester-based and solvate electrolyte, were studied to discuss the possibility of capacity as well as cycle life regulation. The Se/carbon cathode showed significant overcharging in the ether-based electrolyte owing to a severe polyselenide shuttle problem, and displayed a moderate electrochemical performance in ester-based electrolyte. Due to the no free solvent property of the solvate electrolyte, the Se/carbon cathode obtained extremely high Se utilization with an initial specific capacity of 621 mA h g -1 and a reversible capacity of 516 mA h g -1 at 1.0 C current rate after 200 cycles.

Elucidating the performance variations and critical issues of Zn electrodes in different types of aqueous electrolytes for Zn-based rechargeable batteries

Zn-based batteries attract extensive attention as the next-generation energy storage devices for both electronics and large power grids due to the high capacity, energy density, low cost, and safety derived from the inherent properties of metallic Zn and the safety of aqueous electrolytes. Herein, the performance variations and critical issues of the Zn electrodes in the alkaline and neutral/slightly acid electrolytes are systematically investigated by evaluating the cycle stability, electrode reaction kinetics, and stripping/plating reversibility in three kinds of electrolytes, including ZnSO4, Zn(CF3SO3)2, and KOH+Zn(CH3COO)2. The lifespan of the Zn electrode in the neutral/slightly acid electrolytes is >1400% higher than the one in the alkaline electrolyte at a current density of 1 mA cm−2. However, the Zn electrode in the alkaline solution exhibits better reaction kinetics and low polarization. Besides, in the neutral/slightly acid electrolytes, higher coulombic efficiency is obtained, corresponding to better stripping/plating reversibility. Therefore, research in neutral/slightly acid electrolytes should focus on elevating the electrode kinetics and reducing polarization, while in alkaline electrolytes, the dendrite, hydrogen evolution, and self-discharge should be treated to elevate the calendar life and reversibility. This work provides a guideline for further construction of high-performance Zn electrodes in different electrolyte systems.

Electropolymerization of thiazole derivatives bearing thiophene and selenophene and the potential application in capacitors

• Three thiazole derivatives bearing thiophene and selenophene were used as monomers for electropolymerization. • Pseudocapacitor performance of deposited polymer layers was investigated on macroelectrode and ultramicroelectrode. • Pseudocapacitor behavior is related to the anion intercalation/deintercalation processes by faradaic reactions of oligomer chains. • The approximate molecular weight of the solvated anion and the number of solvent molecules surrounding a solvated anion were analyzed. Three thiazole derivatives bearing thiophene and selenophene are synthesized and used as monomers for electropolymerization. The electropolymerization process is studied using cyclic voltammetry (CV) and electrochemical quartz crystal microbalance (EQCM) techniques. Deep understanding is obtained regarding the pseudocapacitor performance of deposited polymer layers by subjecting the macroelectrode and ultramicroelectrode to CV and galvanostatic charging–discharging experiments in three kinds of electrolytes. Notably, the highest specific capacitance is observed in the derivative bearing selenopheno[3,4- d ]thiazole and selenophene in a solution of tetrabutylammonium tetrafluoroborate. Furthermore, the electropolymerization rate is influenced by the kind of chalcogenophene and the CV scan rate. A spectroelectrochemistry experiment reveals the optical and electrochromic behavior of the deposited polymer layers. From these results, the pseudocapacitor performance of the deposited polymer layers is related to anion intercalation/deintercalation processes by faradaic reactions of oligomer chains. The EQCM experiments also reveal these processes during electropolymerization and anion intercalation/deintercalation into the deposited polymer layers. Finally, the approximate molecular weight of the solvated anion and the number of solvent molecules surrounding a solvated anion are analyzed using the EQCM data.

Water-In-Salt Environment Reduces the Overpotential for Reduction of CO2 to CO2– in Ionic Liquid/Water Mixtures

We report a combined computational and experimental work aimed at estimating the equilibrium potential for the electroreduction of CO2 to CO2– (widely accepted to be a crucial and overpotential-determining step) and at providing an alternative view on the reason behind the lower overpotential for CO2 reduction in imidazolium-based ionic liquid/water mixtures. To begin with, we obtained an 80 ps ab-initio molecular dynamics trajectory of the CO2– solvation structures in an 18% EMIM–BF4/water mixture, which delivered no evidence of interaction between EMIM+ and CO2–. Next, using the Fc+/Fc couple as the non-aqueous reference, we calculated the equilibrium potential of the CO2/CO2– couple in the mixture and aligned it with the aqueous SHE scale, proving that the equilibrium potential of CO2/CO2– in the mixture is about 0.3 V less negative than in the aqueous medium. We then looked for the origin of this catalytic effect by comparing the computed vibrational spectra with experimental Fourier transform infrared spectra. This revealed the presence of two water populations in the mixture, namely, bulk-like water and water in the vicinity of EMIM–BF4. Finally, we compared the hydrogen bonding interactions between the CO2– radical and H2O molecules in water and in the mixture, which showed that stabilization of CO2– by water molecules in the EMIM–BF4/water mixture is stronger than in the aqueous medium. This suggests that water in EMIM–BF4/water mixtures could be responsible for the low overpotential reported in these kinds of electrolytes.

Boosting Photoresponse of Self-Powered InSe-Based Photoelectrochemical Photodetectors via Suppression of Interface Doping.

Two-dimensional (2D) InSe is a good candidate for high-performance photodetectors due to its good light absorption and electrical transport properties. However, 2D InSe photodetectors usually endure a large driving voltage, and 2D InSe-based heterojunction photodetectors require complex fabrication processes. Here, we demonstrate high-performance self-powered InSe-based photoelectrochemical (PEC) photodetectors using electrochemical intercalated ultrathin InSe nanosheets. The ultrathin InSe nanosheets have good crystallinity with a uniform thickness of 1.4-2.1 nm, lateral size up to 18 μm, and yield of 82%. The self-powered InSe-based PEC photodetectors show broadband photoresponse ranging from 365 to 850 nm. The photoresponse of InSe-based PEC photodetectors is boosted by suppressing p-type doping of the intercalator with annealing, which improves the electrical properties and facilitates electron transport from InSe to the electrode. The self-powered annealed InSe (A-InSe) PEC photodetectors show a high responsivity of 10.14 mA/W and fast response speed of 2/37 ms. Moreover, the self-powered PEC photodetectors have good stability under UV-NIR irradiation. Furthermore, the photoresponse can be effectively tuned by the concentration and kind of electrolyte. The facile large-scale fabrication and good photoresponse demonstrate that 2D ultrathin InSe can be applied in high-performance optoelectronic devices.

Deeper Understanding of Ternary Eutectic Carbonates/Ceria-Based Oxide Composite Electrolyte through Thermal Cycling

Due to a high conductivity of about 0.1 S·cm−1, Li-Na-K carbonate eutectic and Sm-doped ceria composite material is a good electrolyte candidate for hybrid fuel cells operating between 500 °C and 600 °C. The present paper aims at a deeper understanding of the species and mechanisms involved in the ionic transport through impedance spectroscopy and thermal analyses, in oxidizing and reducing atmospheres, wet and dry, and during two heating/cooling cycles. Complementary structural analyses of post-mortem phases allowed us to evidence the irreversible partial transformation of molten carbonates into hydrogenated species, when water and/or hydrogen are added in the surrounding atmospheres. Furthermore, this modification was avoided by adding CO2 in anodic and/or cathodic compartments. Finally, a mechanistic model of such composite electrical behavior is suggested, according to the surrounding atmospheres used. It leads to the conclusions that cells based on this kind of electrolyte would preferably operate in molten carbonate fuel cell conditions, than in solid oxide fuel cell conditions, and confirms the name of “Hybrid Fuel Cells” instead of Intermediate Temperature (or even Low Temperature) Solid Oxide Fuel Cells.

Two mechanisms of H+/OH− ion generation in anion-exchange membrane systems with polybasic acid salt solutions

Electrodialysis are increasingly used in hybrid membrane technologies for the recovery and separation of weak polybasic acids from municipal and industrial wastewater and other solutions. It is known that the rate of generation of H+ and OH− ions at ion-exchange membrane boundaries during the treatment of such solutions is greater than that in the case of strong electrolytes, such as NaCl. One of the mechanisms of this generation, water splitting involving catalytic participation of functional groups, is relatively well understood. However, the second possible mechanism, where H+ ions are generated during acid dissociation at the depleted solution/anion-exchange membrane interface, is not sufficiently clear. Current-voltage characteristics (CVCs) of a Neosepta AMX anion-exchange membrane in 0.02 M NaH2PO4, NaH2Cit, KHT, and NaCl solutions are recorded. The effective transport number of H+ ion in the depleted boundary solution is measured to quantify the rate of the H+ ion generation. While the “water splitting” mechanism takes place in any kind of electrolytes, the “acid dissociation” mechanism is characteristic only for weak polybasic acids and other ampholytes, the electric charge of which depends on the pH. With that, the first mechanism occurs only at overlimiting currents, and the second occurs both in the underlimiting and overlimiting current modes. The dissociation of acid species at an AEM interface is caused by Donnan exclusion of protons as co-ions from the membrane. The rate of this reaction increases in the order KHT < NaH2PO4<NaH2Cit. This order is determined by the values of equilibrium acid dissociation constants pKai for the first and second ionization steps as well as by the dissociation rate constants for acid anions. The contribution of each of the H+/OH− ion generation mechanisms depends on the current density, more precisely, on the interval between the 1st, 2nd or 3rd limiting currents, recorded on the I–V characteristic. At relatively low currents, the contribution of “water splitting” in the studied weakly acidic systems is insignificant. At i > 2.6 ilimLev, there is a competition between both mechanisms of H+ ion generation. The obtained results give new insight into the understanding of the kinetics of H+/OH− ion generation and the impact of this process on the efficiency of electrodialysis of solutions containing polybasic acid species.

High-Performance Broadband Photoelectrochemical Photodetectors Based on Ultrathin Bi2O2S Nanosheets.

Two-dimensional (2D) bismuth oxychalcogenide (Bi2O2X, X refers to S, Se, and Te) is one type of rising semiconductor with excellent electrical transport properties, high photoresponse, and good air stability. However, the research on 2D Bi2O2S is limited. In this work, ultrathin Bi2O2S nanosheets are synthesized by a facile and eco-friendly chemical synthesis method at room temperature. The thickness and lateral sizes are 2-4 nm and 20-40 nm, respectively. The 2D ultrathin Bi2O2S nanosheets have a broad absorption spectrum from ultraviolet (UV) to near-infrared (NIR). Photoelectrochemical (PEC) photodetectors based on 2D Bi2O2S nanosheets are fabricated by a simple drop-casting method. The 2D Bi2O2S-based PEC photodetectors show excellent photodetection performance with a broad photoresponse spectrum from 365 to 850 nm, a high responsivity of 13.0 mA/W, ultrafast response times of 10/45 ms, and good long-term stability at a bias voltage of 0.6 V, which are superior to most 2D material-based PEC photodetectors. Further, the 2D Bi2O2S PEC photodetector can function as a high-performance self-powered broadband photodetector. Moreover, the photoresponse performance can be effectively tuned by the concentration and the kind of electrolyte. Our results demonstrate that 2D Bi2O2S nanosheets hold great promise for application in high-performance optoelectronic devices.

Debunking the formation mechanism of nanopores in four kinds of electrolytes without fluoride ion

A highly controversial topic, the mechanism of the anodization of the formation of porous structures of metals is still believed by many researchers to be field-assisted dissolution by fluoride ions. In this paper, evidence against this mechanism is provided. Using SEM images of titanium oxides anodized in four fluoride-free electrolytes—NaNO3, KNO3, H2SO4, and H3PO4 solutions—and the corresponding current−time curves, this paper supports the newly grown oxides growing upward around the oxygen bubble mold in a viscous flow mode to form nanotubes. The electronic current is high enough to ensure the continuous release of oxygen gas, which is necessary to form nanotubes, such as in NaNO3 and KNO3 solutions. When the electronic current is small enough, the oxygen bubbles can only form porous structure similar to those found in bread, such as in H2SO4 and H3PO4 solutions.

Effects of Hybrid Solid Electrolyte on Internal Resistance of TiNb2O7/LiNi0.5Co0.3 Mn0.2O2 Cells

Lithium-ion batteries have been required to enhance power density, high and low temperature performance, energy density, and safety due to electrification of various mobilities. We have developed hybrid solid electrolytes consisting of lithium-ion conducting solid particles and a gel polymer or liquid electrolyte as candidate to respond to these demands [1]. Our previous study revealed that hybrid solid electrolytes in the cell reduce the internal resistance, particularly at low temperatures. Moreover, we proposed the mechanism of the resistance reduction, which the lithium ion transference number was increased by attracting the cyclic carbonates such as PC and PF6 - anion on the surface of Lithium-ion conducting solid particles [2]. In this study, we have investigated the effect of hybrid electrolytes on the internal resistance of TiNb2O7(TNO)-based high-power lithium ion batteries.We prepared 1Ah TNO/LiNi0.5Co0.3Mn0.2O2 (NCM) pouch cells with hybrid electrolytes consisting of lithium-ion conducting solid electrolyte wetted by PF6-based liquid electrolyte. The solid electrolyte layer was formed on cathode as shown in Fig.1. NASICON-type Li1.2Zr1.9Ca0.1(PO4)3 (LZCP) was used as a lithium-ion conducting solid electrolyte because of its wide potential window, high chemical stability, and relatively low cost of raw materials. We compared electrochemical properties of the LZCP-based hybrid electrolytes cell to that of the liquid electrolyte cell and the Al2O3 (non-ion conductivity ceramic)-based hybrid electrolytes cell. The particle size and the film thickness of layer for Al2O3 were comparable to those for LZCP.Figure 2 shows DC resistance (DCR) of the three types of cells at various state of charge (SOC) conditions for 10 sec charging at 25℃ and -20℃. The DCR of LZCP-based hybrid electrolyte cell is smaller than that of liquid electrolyte in the whole SOC range at 25℃. At low temperature, the difference of DCR of two cells becomes remarkable, and DCR of LZCP-based hybrid electrolyte cell is about 20% lower than that of liquid electrolyte cell at -20℃. On the other hand, the DCR of the Al2O3-based hybrid electrolyte cell was a little higher than that of liquid electrolyte cell in the all temperature range. Therefore, the solid electrolyte contributes to the reduction of internal resistance especially at low temperatures.Typical AC-impedance spectra of the cells with the three kinds of electrolytes at 25℃ and -20℃ are shown in Figure 3. The impedance spectra exhibit a depressed semicircle, which can be interpreted as resulting from the interface resistance such as the charge-transfer process on the electrodes. The semicircle of the hybrid electrolytes cell is significantly smaller than that of liquid electrolyte cell and Al2O3-based hybrid electrolyte cell especially at -20℃. It is considered that the concentration overpotential near the cathode mainly decreased due to the increase of lithium ion transference numbers by using solid electrolyte to promote the supply of lithium ion to the electrode surface. On the other hand, the LZCP-based hybrid electrolytes cell and the Al2O3-based hybrid electrolyte cell have a larger bulk resistance than that of the liquid electrolytes cell at 25℃. This bulk resistance is mainly ascribable to lithium ion conductive resistance in liquid electrolyte. The lithium ion conductive resistance increased because the porosity was decreased by inserting of solid electrolyte layer or Al2O3 layer between electrodes.These results reveal that LZCP particles in the hybrid solid electrolyte reduces the charge transfer resistance between the electrolyte and active materials rather than the bulk ionic resistance in the electrolyte. The charge transfer resistance rapidly increases compared to the bulk ionic resistance with decreasing temperature. Therefore, it is considered that the DCR of LZCP-based hybrid electrolyte cell decreases especially at low temperatures. In this report, the detail of this hybrid electrolytes cell performance and the mechanism of resistance decreasing will be discussed.[1] K. Yoshima, Y. Harada and N. Takami, J. Power Sources, 302,283-290(2016).[2] T. Kusama, K. Yoshima, T. Sugizaki, K. Hoshina, T. Sasakawa, Y. Harada, and N. Takami, No A02-0172, The Electrochemical Society Meeting MA2019-01, Dallas, TX, May 27 (2019) Figure 1

Electrochemical Determination of Ciclopirox Olamine by Using Boron-Doped Diamond Electrode Modified with Overoxidized Polypyrrole Film

Ciclopirox olamine is one of the basic antifungal agents used in medicine. The multiplicity of pharmaceutical and cosmetic preparations containing ciclopirox olamine causes the need for quick methods to assay it. In this work, the author proposes a method of assaying ciclopirox olamine using BDDE electrode modified with overoxidized polypyrrole (OPPy-BDDE). The work involved the analysis of optimum conditions of BDDE electrode modification. Ciclopirox olamine displayed a well-defined irreversible oxidation peak at the potential of +0.68 V (versus SCE electrode). The analysis of recorded currents depending on the scan rate showed their diffusion character. The pH values and the kinds of electrolyte were optimized using cyclic voltammetry. The optimization of characteristic parameters in the SWV method was conducted in Britton-Robinson buffer with pH 6.98. A linear range of ciclopirox olamine determination was obtained in the concentration range from 6.95 × 10−6 to 6.02 × 10−5 mol/L with the limit of detection of 2.02 × 10−6 mol/L and good repeatability (3.63%, n = 6 measurement, c = 2.34 × 10−5 mol/L). The influence of interferents was also tested. The proposed procedure was successfully used to assay the analyte in pharmaceutical preparations. The obtained results were compared with the values obtained with the comparative method. The error of the developed procedure in relation to the pharmacopoeial method did not exceed 2.5%.