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Metal–organic frameworks (MOFs) have important research value in the field of electrochemical CO2 reduction reaction because of their rational design. Here, a new MOF-CH3 was prepared via a simple solvothermal method by using Zn as the metal center and 1,2,4-triazole and 2-methyl-terephthalic acid as ligands for electrocatalytic CO2 reduction. The single-crystal X-ray diffraction shows that MOF-CH3 is N, O-coordinated 3D columnar layer framework with intramolecular hydrogen-bonding interactions. The powder X-ray diffraction for MOF-CH3 displays the good crystallinity of 24 h in 0.5 mol L−1 KHCO3 electrolyte solution. The electrochemical CO2 reduction reaction tests indicate that the MOF could effectively convert CO2 to formate, and the highest Faradaic efficiency of formate (FEformate) is 76.5% at − 1.37 V (vs. reversible hydrogen electrode) with a partial current density of formate of − 12.1 mA cm−2. The performance of MOF-CH3 is better than that of the reported other two structural analogues MOF-NH2 with FEformate of 55.7% at − 1.57 V or MOF-H with FEformate of 73.5% at − 1.37 V in aqueous CO2-saturated electrolyte solution. The work shows that the performance could be improved by regulating the microenvironment of MOF catalysts. [ABSTRACT FROM AUTHOR]

This research innovatively produced polyaniline-coated carbon cloth (PANI@CC) using an electrochemical deposition process, highlighting the impact of carbon cloth substrate characteristics on the performance of symmetric supercapacitors in a coin cell setup. The study compared the electrochemical performance of hydrophilic and hydrophobic, soft, and hard carbon cloth substrates through cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The PANI@0-N (hydrophilic soft carbon cloth) substrate showcased superior electrochemical properties, achieving a maximum specific capacitance of 113.3 F g−1 at a current density of 0.1 A g−1, with a noteworthy rate capability of 88.6%. After 2000 galvanostatic charge–discharge cycles at 1 A g−1, the developed symmetric coin cell supercapacitor retained 74% of its initial capacitance, demonstrating notable durability and efficiency. This underscores the significance of substrate selection in the direct synthesis approach for optimizing supercapacitor performance, making the PANI@0-N-based coin cell a promising option for supercapacitor applications. [ABSTRACT FROM AUTHOR]

Indium antimonide (InSb) is a III-V compound semiconductor with a narrow bandgap and a high electron mobility, and is used in various optoelectronic devices. Electrodeposition represents a low-cost, scalable method for fabricating InSb films. In the literature, aqueous electrolytes and ionic liquids have commonly been applied. In this work, the electrodeposition of InSb films and nanowires from a dimethyl sulfoxide (DMSO)-based electrolyte was demonstrated. This electrolyte enabled electrodeposition in a broader potential range and at higher temperatures as compared to aqueous electrolytes. The electrolyte has a lower viscosity than ionic liquids, therefore exhibiting better mass transport properties for electrodeposition. It was shown that antimony(III) chloride, a precursor that is commonly used for InSb electrodeposition, leads to the formation of the metastable "explosive" antimony allotrope. Instead, self-prepared antimony(III) nitrate and indium(III) methanesulfonate were used, and were proven to be suitable precursors. Electrolytes with a 5:1 indium-to-antimony precursor molar ratio enabled electrodeposition of InSb films at 21 °C and 120 °C on platinum and n-type InSb(400), as well as electrodeposition of InSb nanowires in anodized aluminum oxide templates. The morphology, elemental composition and crystallinity of as-deposited InSb was analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), respectively. It was demonstrated that the film quality did not improve at 120 °C. Tauc plots from FT-IR transmission measurements were used for the determination of the bandgap of the deposits. The bandgap of the InSb films on platinum was 0.159 eV at 21 °C and 0.168 eV at 120 °C, whereas the bandgap of the InSb film deposited at 120 °C on InSb(400) was 0.186 eV. [ABSTRACT FROM AUTHOR]

Aqueous zinc-ion batteries (AZIBs) are considered promising candidates for scalable and sustainable energy storage devices due to their low cost and high safety advantages. However, the practical application of AZIBs is subject to the limits of the reversibility of the Zn2+ stripping/plating, such as the growth of Zn dendrites, corrosion of Zn anode, and hydrogen evolution reaction (HER). Herein, we propose a solution to the issues of AZIBs by creating a versatile electrolyte via the addition of polyethylene glycol (PEG). PEG additive changes the coordination environment of Zn2+ and disturbs the solvation structure of H2O, which is beneficial to alleviate the side reactions triggered by water molecules in the Zn2+ solvation structure. In addition, the Zn2+ nucleation behavior is optimized by texturing the hexagonal deposition plane and inducing the compact-grained deposition manner to resist corrosion reactions and dendrite aggravation. The solvation structure of Zn2+ is optimized to improve the reversibility of the Zn anode. As a result, improved reversibility of Zn plating/stripping on the Cu-working electrode is achieved by 20% PEG electrolyte with high Coulombic efficiency (CE) of 99.43% at 1 mA cm−2, stably cycled for 750 cycles. Furthermore, the Zn||Zn symmetrical half-cell with 20% PEG electrolyte shows stable plating/stripping overpotentials for more than 1400 h. Finally, the Zn||V2O5 full-cells exhibit excellent long cycling stability for over 180 cycles even at 1000 mA g−1 with a high reversible capacity of 168 mAh g−1. This work provides valuable insights into designing electrolytes for aqueous zinc metal batteries. [ABSTRACT FROM AUTHOR]

In this study, manganese carbonate (MnCO3) microspheres were used as self-templates for the synthesis of hollow and radially porous MnO2 via an oxidation-etching process. Then, in situ polymerization of aniline was conducted with and without 3-aminopropyl triethoxysilane (APTES) grafting agent, resulting in the formation of PANI-grafted MnO2 (MGP) and PANI-coated MnO2 (MP), respectively. The electrochemical performances were evaluated in a three-electrode configuration using a 1 M H2SO4 aqueous electrolyte solution. Both samples showed high-specific capacitances owing to the unique MnO2 structure with radial cavities, which facilitate ion diffusion and effectively accommodate volume expansion during cycling. The MGP exhibited ~ 30% higher specific capacitance (765 F g−1 and 586 F g−1 at 0.25 A g−1) and extended cycle life (80% retention after 14,000 cycles) compared to the MP. The results demonstrate that the charge transfer efficiency and structural stability of MGP are enhanced by the formation of covalent bonds between MnO2 and PANI through grafting. [ABSTRACT FROM AUTHOR]

In this study, a facile synthesis of Cobalt oxyhydroxide (CoOOH) via the co-precipitation method at room temperature under vigorous stirring and compared the supercapacitor performance with that of manganese, aluminum, and iron oxyhydroxides. The prepared materials were confirmed by X-ray Diffraction (XRD), and Fourier Transform-Infrared Spectroscopy (FT-IR). The structural and surface area were investigated by Scanning Electron Microscopy (SEM), and Bruner-Emmert-Teller (BET) analyses. These materials were examined for their capacitance performance by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M KOH aqueous electrolyte solution. Among these oxyhydroxides, CoOOH showed excellent capacitance than other oxyhydroxides. The CoOOH electrode exhibits a specific capacitance of 1096 F g− 1 at 25 mV s− 1 and 670 F g− 1 at 1 A g− 1 current density found from CV and GCD, respectively. Furthermore, the CoOOH electrode was investigated for cyclic stability and exhibited 91% capacitance retention after 5000 cycles. [ABSTRACT FROM AUTHOR]

An operational description of the linear potential scan voltammetry of solids experiencing a solid-state redox transformation with phase changes is described. The modeling is based on the application of nucleation equations of solid-state reaction kinetics to express the transferred charge/applied potential relationships. The flexible use of Prout-Tompkins and Avrami-Erofe'ev kinetics permits a satisfactory description of the voltammetry of solid-to-solid redox transformations with phase segregation. The model satisfactorily applies to reproduce linear potential scan curves recorded for graphite electrodes modified with several lead compounds in contact with aqueous electrolyte solutions. [ABSTRACT FROM AUTHOR]

Even though Pd-H system has been known since the nineteenth century, it is still of interest to scientists. Pd thin film electrode (called as a Limited Volume Electrode – LVE) is able to electrosorb hydrogen form aqueous (acid, base) and non-aqueous electrolytes (e.g. ionic liquids). Therefore Pd-H is an irreplaceable model system for the study of hydrogen electrosorption in different media. The paper presents: (1) short overview of the study of hydrogen sorption in Pd, (2) the detailed description of the electrochemical measurement methods and (3) the equations for the determination of hydrogen electrosorption charges needed to hydrogen electrosorption isotherms creation. The presented approach can be applied for laboratory work. The results show that Pd-LVE can be effectively used as a model system before the studies of multicomponent hydrogen storage alloys (e.g. AB5 alloys). [ABSTRACT FROM AUTHOR]

Aqueous zinc ion batteries have shown great prospects in large-scale energy storage. However, severe dendritic growth and unrestrained side reactions have limited the high speed development of aqueous zinc ion batteries due to the instability of zinc anodes in aqueous electrolytes. Here, butanediol additive is introduced into ZnSO4 electrolyte to improve the stability of zinc anode by adjusting the solvation structure of zinc hydration layer. This leads to a long cycle life (1000 h), which is more than 8 times greater than that of ZnSO4 basic electrolyte, for Zn||Zn symmetric batteries utilizing 2 M ZnSO4 and 15% butanediol additions. The butanediol additive can also achieve high Coulombic efficiency with an average value of 99.58% in Zn||Cu batteries. The Zn||V2O5 full battery exhibits a maximum capacity of 205 mAh g−1, and even after 1000 cycles at 1.0 A g−1, it still has a high reversible specific capacity of 177 mAh g−1. [ABSTRACT FROM AUTHOR]

Doped metal oxide nanostructures have emerged as a subject of considerable interest in the domain of energy storage applications, owing to their exceptional characteristics in comparison to their pristine metal oxides. Herein, pristine and Tin (Sn) doped hematite (α-Fe2O3) nanostructures were successfully synthesized using the hydrothermal method. The effect of Sn doping on various characteristics of hematite nanoparticles, such as unit cell size, crystallinity, particle size, and electrochemical properties, was examined and analyzed. The verification of Sn4+ ions being integrated into the crystalline structure of hematite was established through X-ray photoelectron spectroscopy (XPS) and with the assessment of unit cell expansion resulting from the substitution of octahedrally coordinated Fe3+ ions, with notably larger Sn4+ ions. The electrochemical properties of the materials that were prepared were analyzed within a three-electrode cell setup, utilizing a 3.0 M aqueous potassium hydroxide electrolyte. Notably, the hematite electrode doped with 7% Tin exhibited exceptional capacitance, reaching a value of 833 F/g at a scan rate of 10 mV/s. The incorporation of Tin into the hematite structure played a critical role in facilitating efficient ion transport and enhancing conductivity, thus promoting favorable conditions for various electrochemical reactions. Furthermore, the material exhibits exceptional rate capability and robust cycling stability. Finally, an asymmetric supercapacitor was fabricated by integrating Sn-doped α-Fe2O3 as the anode material and activated carbon as the cathode material. The resultant device showcases impressive energy and power densities of 28.3 Wh Kg−1 and 528.8 W Kg−1, respectively. Such noteworthy performance characteristics signify its promising prospects for practical implementation in energy storage devices. [ABSTRACT FROM AUTHOR]

Alloy electroplating using deep eutectic solvents (DES), compared to aqueous electrolytes, has essential benefits in a wide potential range, the high solubility of metal salts (including chlorides and oxides), and an environmentally friendly alternative. This research aimed to compare the coatings obtained by electrolysis of the Ni–Co alloy conventionally from an aqueous solution against the electroplating obtained in 2:1 ethylene glycol-choline chloride. The electrochemical behavior was studied through potentiodynamic polarization kinetic analysis carried out complying with Abner's rules for alloy deposits; hydrodynamic conditions were modified, keeping the temperature at 60 °C and the salt concentration in both baths constant. As a result, nickel electrolysis has been carried out successfully by taking advantage of the benefits of using DES in energy consumption with 80% efficiency compared to water as a solvent under the same conditions. The composition and morphology of Ni–Co alloy coatings were characterized by scanning electron microscopy (SEM/EDS), and corrosion resistance was investigated by potentiodynamic polarization and electrochemical impedance (EIS). Coatings were obtained for both electrolytic baths with a chemical composition within the range of the alloy but with a higher cobalt content in the deposits obtained in water; in contrast, the distribution of the Ni–Co alloy was more homogeneous with changes in morphology and crystallization in the deposits obtained from the DES bath. The coatings' anti-corrosion performance showed that the Co content difference increases the corrosion resistance of the Ni–Co alloy obtained from aqueous electrolytes compared to deposits obtained from DES. [ABSTRACT FROM AUTHOR]

This work was aimed at preparing the composites TiO2@CNTs via facile sol-gel route and investigating the electrochemical performance in neutral aqueous electrolyte 1 M Na2SO4 with a high voltage of 1.8 V The synergistic effects between TiO2 and CNTs in composite electrode were offered a significantly high specific capacitance of 227 F·g−1 at a scan rate of 10 mV·s−1. The EIS analysis evidenced not only the pseudocapacitance process of composite TiO2@CNTs with the combination of non-Faraday and Faraday process but also the superior electrochemical performance of TiO2@CNTs-5%. The ionic diffusion coefficients of TiO2@CNTs-5%, TiO2@CNTs-3%, and TiO2@CNTs-1% were calculated 1.47 × 10−17 cm2·s−1, 1.12 × 10−17 cm2·s−1, and 0.71 × 10−17 cm2·s−1, respectively. Moreover, TiO2@CNT electrodes have been utilized to assemble a symmetrical supercapacitor which has delivered an excellent capacitance of 97.3 F·g−1 at a current rate of 1 A·g−1. The device shows a long-term stability upon 5000 cycles without degradation, and the energy density of TiO2@CNTs was 15–43.8 Wh·kg−1 in the power density range of 1800–18,000 W·kg−1. [ABSTRACT FROM AUTHOR]

Aqueous supercapacitors are promising electrochemical energy storage devices for research nowadays due to their intrinsic high safety, low cost and high power density. However, the freezing of water at low temperatures limits the scope of application of aqueous devices. Here, we report a dilute hybrid electrolyte with low-temperature performance by introducing ethylene glycol (EG) as an organic additive for mixed electrolysis at a low concentration of 1 m (mol kg−1) Mg(ClO4)2. The results show that EG can break the hydrogen bonding between water molecules to prevent the electrolyte from solidifying at low temperatures. The optimized electrolyte has a low freezing point below -50 ℃, which allows the assembled supercapacitor being able to operate at extreme low temperature environments. And it was worth mentioned that the addition of EG could effectively enhance the long-cycle performance of the devices and the assembled supercapacitor can operate stably for more than 30,000 cycles at -30 ℃ and delivered a capacitance of 22.5 F g−1 with a capacitance retention rate of 89% after completion of the cycling. [ABSTRACT FROM AUTHOR]

Due to the low cost and better security, aqueous zinc-ion batteries (AZIBs) are receiving a great deal of attention for large-scale energy storage. Vanadium-based materials have immense potential as AZIB cathode materials. Herein, the KxVO2 (KVO) cathode materials synthesized by the hydrothermal method. The morphology and structure of KVO were characterized by X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). FESEM demonstrated that sample displayed sheet morphology. The electrochemical performance of KVO electrode in aqueous zinc ion battery was determined by cyclic voltammetry and galvanostatic charge–discharge test after assembly of Zn-KVO button cell using 3 M ZnSO4 aqueous electrolyte. The Zn-KVO battery has a capacity of 435.8 mAh⋅g−1 at 0.2 A g−1. After 1000 cycles at 4 A g−1, the cycle reversible capacitance retention rate was 78% of the original capacity. Compared with V2O5 electrode, the capacity and cycle stability of KVO electrode have been significantly improved. [ABSTRACT FROM AUTHOR]

This work investigates the electrochemical performance of an asymmetric supercapacitor with a porous carbon electrode exhibiting a linear or stepwise change structure, along with a non-aqueous electrolyte, during the charging/discharging process, in which Butler–Volmer equations together with Frumkin isothermal relations are employed in a one-dimensional model to describe the deposition/dissolution reactions of lithium metal in a lithium electrode and adsorption/desorption in a porous carbon electrode. The effects of porosity distribution (i.e., linear, stepwise, and constant porosity) and the thickness ratios between two layers with different porosities in stepwise distribution on the cell voltage, electrode potential, and surface coverage or adsorption filling in the supercapacitor are analyzed. Higher cell voltage and electrode potential and larger surface coverage occur in the mode with a linearly increasing porosity of ε = 0.84 to 0.89 in the carbon electrode (i.e., 4.78 V cell voltage, 4.15 V electrode potential, and adsorption filling of 0.514 at current of 2.1 mA/cm2), which decrease with current increasing from 2.1 to 5.25 mA/cm2. The change in porosity amplitude relates to the matching between the current and electrolyte supply, as well as electrolyte conductivity and specific surface area in the electrode. Additionally, the cell voltage and electrode potential can be adjusted by varying the thickness ratio in the porous electrode in stepwise fashion. [ABSTRACT FROM AUTHOR]

Zinc ion batteries are favored by researchers because of their intrinsic safety, low cost, and high theoretical energy density. The serious dendrite growth of Zn anode during electrochemical deposition inhibits the development of zinc ion batteries currently. Many research works have been carried out to modify the zinc metal anode surface and aqueous electrolyte. Significantly, as the carrier of electrolyte and the bridge of ions, the separators show promising potential of inhibiting dendrites growth by regulating the ions migration and the electric field of the electrolyte-anode interface. However, a technical review about the separators of zinc ion batteries is still rare. In this review, the basic requirements of separators and the latest development of modification materials and mechanisms are summarized. Finally, the perspectives for further developments on the separators of zinc ion batteries are outlined. This review could offer useful information for the further development of separators for zinc ion batteries. [ABSTRACT FROM AUTHOR]

The Ti/TiO2 + ZrO2, Ti/TiO2 + CeOx, and Ti/TiO2 + CeOx + ZrO2 composites, including Y-doped ones, have been fabricated by one-stage plasma electrolytic oxidation (PEO) of titanium in aqueous electrolytes based on Zr(SO4)2 and/or Ce2(SO4)3 with and without additives of Y(CH3COO)2 at effective anodic current density of 0.05 A/cm2 for 10 min. SEM, XRD, and EDX methods have been used for investigation of the composition of the coatings. The resulting PEO coatings contain crystalline TiO2 in rutile and anatase modifications. PEO coatings formed in 0.1 M Zr(SO4)2 electrolyte additionally include TiZrO4 and m-ZrO2. The introduction of yttrium acetate or cerium sulfate into this electrolyte leads to the formation of t-ZrO2 instead of m-ZrO2 in the composition of PEO coatings. The pH sensitivity of obtained composites depends on the composition and morphology of their surface. The Ti/TiO2 + CeOx + ZrO2 composite revealed the highest electrode function slope equal to 51 ± 1 mV/pH and excellent performance for end-point indication potentiometric acid–base titration similar to the conventionally used glass electrode. The Ti/Ce + Zr electrodes have shown excellent performance for determining the alkalinity of both technogenic waters and seawater. These composites are promising for use as wear- and corrosion-resistant pH solid-state sensors for long-term monitoring of highly saline waters, including seawater. [ABSTRACT FROM AUTHOR]

Li-air batteries have ultra-high theoretical capacity, but the actual discharge performance is not ideal. The morphology constraint formed by the cathode material in the electrolyte atmosphere is one of the factors affecting the transport performance of reactants. Coarse-grained simulation based on mesoscopic scale has inherent advantages in the study of system morphology and mass transfer characteristics by virtue of large spatial and temporal scales. Here, a polarizable water solvent coarse-grained model and carbon nanotube (CNT) pore coarse-grained model were constructed. The dynamic processes at the interface composed of CNT electrodes, different hydrophilic-functionalized CNT electrodes, and aqueous electrolytes were investigated by coarse-grain molecular dynamics (CGMD) simulations. The distribution and morphology of different functionalized CNTs, as well as the system and internal and external transport properties of the tube, were analyzed from the mesoscopic scale. The results show that CNTs can form a hydrophobic phase in aqueous electrolytes, and at the same time form a solvent phase that can provide favorable conditions for ion transport. By adding hydrophilic functional groups and uniform modification, the hydrophobic aggregation can be significantly improved, and the transport delay of CNTs to oxygen in the electrolyte can be weakened. The obtained simulation results of Li+ and oxygen diffusion coefficients are consistent with the microscopic simulation results and experimental data. In addition, the optimal material transport condition of the composite cathode is obtained when the mass ratio of uniformly functionalized CNT to hydrophobic CNT is 1/3. Moreover, the transport within the CNT tube has a higher transport efficiency in a single direction. This study is of great significance for analyzing the mesoscopic morphology and mass transfer characteristics of oxygen electrodes in Li-air batteries in aqueous electrolytes. [ABSTRACT FROM AUTHOR]

In this work, the asymmetric supercapacitor (ASC) devices with three different electrolytes including aqueous, organic, and gel polymer electrolytes have been fabricated to investigate and compare the potential window and the capacitive efficiency of the fabricated devices. The aqueous electrolyte includes potassium hydroxide (KOH, 6.0 M), the organic electrolyte is a solution of lithium hexafluorophosphate (LiPF6, 1.0 M in ethylene carbonate/dimethyl carbonate (EC/DMC)), and the gel polymer electrolyte includes porous poly(acrylonitrile-polyhedral oligomeric silsesquioxane) membrane (P(A-POS)) moistened in 1.0 M solution of LiPF6 in EC/DMC. The positive electrode was a cobalt oxide-based electrode, i.e., Co3O4 nanoribbons (NRCo3O4), and the negative electrode was the activated carbon (AC). The specific capacitance of the supercapacitor with aqueous electrolyte (A-ASC) at the current density of 2 A g−1 is 88.0 F g−1, which has a higher specific capacitance than that of the supercapacitor with organic electrolyte (O-ASC) and the supercapacitor with gel polymer electrolyte (G-ASC). The gel polymer electrolyte for NRCo3O4//AC device shows a wide potential window of 4 V and low charge transfer resistance of 11 Ω. The specific capacitance of NRCo3O4//AC device with gel polymer electrolyte was 54.34 F g−1 at 2 A g−1, which is higher than the specific capacitance of O-ASC. [ABSTRACT FROM AUTHOR]

This work presents the construction of a reversible zinc ion battery using components recovered from exhausted Zn/C primary cells. The reduced cathode material from the primary battery served as raw material to synthesize birnessite-type manganese oxide, which, when working as a cathode in conjunction with an aqueous electrolyte and a recovered zinc anode, exhibits a reversible capacity of 289 mAh g−1 at 20 mA g−1. This performance is similar to that observed for manganese oxide synthesized from potassium permanganate reagent (270 mAh g−1 at 20 mA g−1). The structural characterization shows that the material obtained from recycling activities changes its morphology and surface area due to the presence of sodium ions during the synthesis process, and these remain in their structure. These changes promote a 60% capacity lost after being cycled at different charges, compared to 26% of δ-MnO2 synthesized from permanganate reagent. The long-term stability test shows that both batteries can retain their capacity after 1000 discharge/charge cycles at a load of 1000 mA g−1. The results support the sustainability of using a primary cell residue to get an electric energy storage device again. [ABSTRACT FROM AUTHOR]

The present study considers TiC-derived carbon (CDC) and its partially oxidized derivative (ox-red-CDC) as potential electrode materials for pH-neutral aqueous electrolytes. The CDC was converted to ox-red-CDC by a modified Hummers' method involving back-reduction with hydrogen at 800 °C. Oxidation degraded the graphitic CDC structures, as shown by X-ray diffraction analysis, while scanning electron microscopy confirmed the exfoliation of graphene layers on the oxidized carbon surface. The changes in the surface chemistry of the carbon materials were studied by infrared, X-ray photoelectron, and energy-dispersive X-ray spectroscopy. The gas adsorption analysis showed a slight decrease in the volume of the subnanometer-sized pores during oxidation/reduction of CDC. To elucidate the relationships between the structure and electrochemical properties of carbon materials, cyclic voltammetry, galvanostatic cycling, and electrochemical impedance spectroscopy measurements were performed in 1 M Na2SO4 using 2- and 3-electrode test cells. The highest capacitance of 163 F g−1 was demonstrated by pristine TiC-derived CDC in a symmetric 2-electrode cell. The asymmetric cell, which contained ox-red-CDC as an anode and pristine CDC as a cathode, had a slightly lower capacitance but an excellent cycling lifetime (specific capacitance increased by 7% after 5000 cycles). Temporary repolarization of 2-electrode cells during cycling improved both capacitance and power characteristics. [ABSTRACT FROM AUTHOR]

Since their discovery in 2011, MXenes are extensively studied as materials for electrochemical energy storage systems. The high electric conductivity, 2D structure, enabling ions insertion, and excellent chemical stability make MXenes an attractive choice for energy storage applications. This review is focused on the utilization of MXenes in aqueous electrolyte solutions, as cost-effective and safe medium. This review describes the compatibility and electrochemical performance of MXenes as electrodes for charge storage devices. We present their composition with capacitive compounds or redox-active materials such as nano-carbons, metal-oxides, and conducting polymers. Other applications of MXenes as complementary components in energy devices including current collectors, separators, and binders are presented as well. Finally, we discuss the challenges and limitations of MXenes compounds and propose a perspective for their future development. [ABSTRACT FROM AUTHOR]

Anodic oxides were galvanostatically grown on sputtered Ti-12at%Si alloy at 5 mA cm−2 up to 50 V in phosphoric acid and sodium citrate aqueous electrolytes in order to investigate the effect of anions incorporation (if any) on dielectric properties of the grown oxides. Photoelectrochemical measurements supported the occurrence of incorporation of citrate anions when anodizing is carried out in a citrate-containing solution. Indeed, two different absorption thresholds were estimated due to energy transitions involving localized states in the mobility gap. Differential capacitance measurements showed higher capacitance values for anodic oxide grown in the citrate-containing solution, with a beneficial effect on the dielectric constant. The increased capacitance can be explained considering the synergistic effect of a more favourable anodizing ratio provided by the presence of Si cations from the bare alloy as well as the incorporation of foreign species due to the inward migration of citrate anions from the electrolyte during the anodizing process. [ABSTRACT FROM AUTHOR]

A new method of preparation of aqueous electrolyte baths for electrochemical deposition of nickel targets for medical accelerators is presented. It starts with fast dissolution of metallic Ni powder in a HNO3-free solvent. Such obtained raw solution does not require additional treatment aimed to removal nitrates, such as the acid evaporation and Ni salt precipitation-dissolution. It is used directly for preparation of the nickel plating baths after dilution with water, setting up pH value and after possible addition of H3BO3. The pH of the baths ranges from alkaline to acidic. Deposition of 95% of ca. 50 mg of Ni dissolved in the bath takes ca. 3.5 h for the alkaline electrolyte while for the acidic solution it requires ca. 7 h. The Ni deposits obtained from the acidic bath are physically and chemically more stable and possess smoother and crack-free surfaces as compared to the coatings deposited from the alkaline bath. A method of estimation of concentration of H2O2 in the electrolytic bath is also proposed. [ABSTRACT FROM AUTHOR]

Asymmetrical Zn thin foil|carbon cloth two-electrode cells based on 1 M Zn(ClO4)2 aqueous solution have been tested using cyclic voltammetry, constant current charge/discharge, and electrochemical impedance methods. The Ragone plots have been calculated from constant power measurements data. Very high gravimetric and volumetric energy densities at moderate gravimetric and volumetric power densities have been calculated, nearly 2–3 times higher than those for the best sol–gel method prepared two carbon electrode single cells. It was found that even at high power density (10 kW kg−1), the energy density values are comparable with the results for best CDC and sol–gel methods prepared carbon materials based supercapacitors. It has been observed that studied asymmetrical two-electrode cells demonstrated higher energy densities (~ 70 W h kg−1) than the ionic liquid based symmetrical cells what show energy density up to 47 W h kg−1 and capacitance ~ 120 F g−1. However, the power densities and relaxation times for Zn(ClO4)2 aqueous electrolyte based supercapacitors still need to be increased and decreased, respectively, to meet the needs of very quick short pulses high power energy storage applications. [ABSTRACT FROM AUTHOR]

This paper presents a non-aqueous Li-air battery model that considers the side reactions of lithium carbonate (Li2CO3) formation from both electrolyte decomposition and carbon dioxide (CO2) in the ambient air. The deposition and decomposition behaviors of discharge products, the voltage, and capacity evolutions during the cycling operation of the Li-air batteries are investigated. The deposition behavior analysis implies that the Li2CO3 generated by electrolyte decomposition is mainly distributed near the separator side, while it is dominantly generated by Li-O2/CO2 reaction near the air side. The formation of Li2CO3 by side reactions makes the Li-air batteries exhibit a peak discharge deposition inside the cathode. Moreover, Li2CO3 is difficult to decompose and gradually accumulates with cycles, especially near the air side. The severe accumulation of Li2CO3 near the air side significantly reduces the O2 diffusion into the electrode, which induces severe cycling performance decay of the Li-air batteries. According to the distribution and evolution of the deposition, three simple hierarchical cathode structures with high porosities near the air side are finally studied. The simulation results indicate that the increase of the local porosity near the air side substantially improves the cycling performance of the Li-air batteries. [ABSTRACT FROM AUTHOR]

This paper reviews reported methods of the electrochemical deposition of nickel layers which are used as target materials for accelerator production of medical radioisotopes. The review focuses on the electrodeposition carried out from aqueous electrolytes. It describes the main challenges related to the preparation of suitable Ni target layers, such as work with limited amounts of expensive isotopically enriched nickel; electrodeposition of sufficiently thick, smooth and free of cracks layers; and recovery of unreacted Ni isotopes from the irradiated targets and from used electrolytic baths. [ABSTRACT FROM AUTHOR]

The objective of this work is twofold: (1) to improve the electrochemical performance of reduced graphene oxide (RGO) by decorating RGO sheets with magnetic nanoparticles (MNPs) and (2) to evaluate the electrochemical performance of RGO and MNP-decorated RGO (MRGO) in various aqueous electrolyte solutions (phosphate buffer solution (PBS) containing ferricyanide, PBS containing ferricyanide and KCl, Na2SO4, and KOH). The morphological and structural characteristics of solvothermal synthesized RGO and MRGO revealed the decoration of phase pure Fe3O4 nanoparticles on RGO sheets. In FC-PBS-KCl electrolyte solution, MRGO showed higher redox peak current (83.89 μA) and lower peak potential separation (0.11 V) at 50 mV s−1 scan rate compared with that in FC-PBS electrolyte solution. MRGO showed 15.5% higher peak current than that for the RGO in FC-PBS-KCl electrolyte solution. Moreover, the peak current for MRGO in FC-PBS-KCl was increased by 30% when compared with that in FC-PBS electrolyte solution. These results suggest that MRGO in FC-PBS-KCl electrolyte solution can be a good electron pathway between electrode and electrolyte solution for sensing applications. On the other hand, in both Na2SO4 and KOH electrolyte solution, RGO and MRGO showed supercapacitive behavior. In KOH, MRGO exhibited higher specific capacitance (180 Fg−1 at 3 A g−1) and superior cyclic stability (87% after 2000 cycles) compared with that in Na2SO4. MRGO showed 219% increase in specific capacitance than that of the RGO in KOH electrolyte solution. The superior electrochemical performance of MRGO compared with that of RGO is attributed to the synergistic effect of conductivity of RGO and redox activity of MNPs. [ABSTRACT FROM AUTHOR]

The stability of graphene dispersions in water is of both scientific and technological significance. We studied the dispersion stability of electrochemically exfoliated graphene in an aqueous medium to minimize the strong aggregation tendency, within a short period, of graphene prepared in various electrolytes. This study focused on increasing the dispersion stability of graphene and finding the reason for its poor dispersion stability. The residual electrolyte trapped in the graphene layers was difficult to be removed from electrochemically exfoliated graphite and caused a significant aggregation. The stability and dispersion concentration can be improved by removing the trace amount of aqueous electrolyte. The aggregation mechanism of graphene in aqueous media is proposed and discussed in detail. [ABSTRACT FROM AUTHOR]

Concerning the importance of the identification and characterization of food dyes in food science, this work presents a screening method using voltammetry of immobilized microparticles for identification in solid state of sunset yellow, tartrazine yellow, brilliant blue, indigotine, and erythrosine in food matrices. Different aqueous supporting electrolyte were investigated for screening purpose and NaCl 0.1 mol L−1 showed to be suitable for evaluating dyes in solid state. By using square wave voltammetry as detection mode was possible to establish qualitative diagnostic criteria for identification of dyes in commercials powder of food dyes samples using both anodic and cathodic scan. Moreover, based on the solid-state electrochemistry profile and due to the lack of information about the electrochemical behavior of these compounds in solid state, some oxi/reduction pathways could be elucidated, and special attention was given to the case of sunset yellow dye. [ABSTRACT FROM AUTHOR]

An interpretation framework is presented which provides a straightforward means to characterise the electrochemical reactivity of aqueous ions together with their various hydrolysed counterparts. Our novel approach bypasses the more laborious strategy of solving rigorously, for all relevant species, the complete set of Butler-Volmer equations coupled to diffusion differential equations. Specifically, we consider the spatial variable via a Koutecký-Koryta type of differentiation between nonlabile and labile zones adjacent to the electrode. The theory is illustrated by an assessment of the electrochemical reactivity of aqueous In(III) species based upon proper comparison between relevant time scales of the involved interfacial processes, i.e. diffusion, (de)protonation of inner-sphere water, dissociation/release of H2O and OH−, and electron transfer. The analysis reveals that whilst all In(III) species are labile on the experimental timescale with respect to (de)protonation and (de)hydration, there are large differences in the rates of electron transfer between In H 2 O 6 3 + and the various hydroxy species. Specifically, in the case of In H 2 O 6 3 + , the rate of electron transfer is so slow that it replaces the traditional Eigen rate-limiting water release step in the overall passage from hydrated In3+ to its reduced metallic form; in contrast, the In(III) hydroxy species display electrochemically reversible behaviour. [ABSTRACT FROM AUTHOR]

Hydrogen permeation through a pure palladium film (25 μm thickness, optically dense) is employed to trigger electron transfer (hydrogen-driven) reactions at the external palladium | aqueous electrolyte interface of a two-compartment electrochemical cell. Two systems are investigated to demonstrate feasibility for (i) indirect hydrogen-mediated silver electrodeposition with externally applied potential and (ii) indirect hydrogen-mediated silver electrodeposition driven by external formic acid decomposition. In both cases, porous metal deposits form as observed by optical and electron microscopies. Processes are self-limited as metal deposition blocks the palladium surface and thereby slows down further hydrogen permeation. The proposed methods could be employed for a wider range of metals, and they could provide an alternative (non-electrochemical or indirect) procedure for metal removal or metal recovery processes or for indirect metal sensing. [ABSTRACT FROM AUTHOR]

Polypyrroles doped with multiply charged anions are becoming increasingly important in a wide range of energy, environmental and biomedical applications. The increased counterion charge promotes anion binding and retention and can significantly increase stability and performance. The electrochemical properties of polypyrrole films prepared galvanostatically in Na2SO4 (PPySO4) where found to be similar those of PPyClO4 prepared in NaClO4, although there was significantly more anion retention during potential cycling. In contrast, PPyPO4 films prepared in Na3PO4 under the same conditions were over-oxidised and more dense, which is beneficial for corrosion protection and electroanalysis. Paradoxically, the low mobility of SO42− counterions results in more facile charging and discharging of the film, as observed with large and polymeric counterions. This can create significant benefits in applications that require fast cycling, such as supercapacitors and high-rate batteries. These conclusions are corroborated by electrochemical impedance measurements in various aqueous electrolytes. Ionic conductivity was dominated by anion transport for both PPyClO4 and PPySO4, whilst PPyPO4 was predominantly a cation conductor. [ABSTRACT FROM AUTHOR]

Polyaniline/carbon (Pani/C) composites were synthesized by oxidative polymerization of aniline in the presence of carbon material at different pH values. Composites obtained possess identical composition (56 wt% of polymer as determined by CHNS elemental analysis) but differ in morphology and porous structure. Biomass-derived activated carbon having specific surface area of 1740 m2 g−1 was used as carbon component. Porous structure was characterized by low-temperature nitrogen adsorption at 77 K. The electrochemical behavior of the samples was investigated by cyclic voltammetry in a three-electrode cell in different electrolytes: aqueous 1 M H2SO4 and 1 M solution of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) in acetonitrile (ILE). Based on cyclic voltammetry data mechanism of polyaniline transformations in ILE involving BMIM+ as a proton source was proposed. Symmetric supercapacitors (SC) were assembled with Pani/C electrodes and ILE. Study of SC by the set of electrochemical techniques and investigation of the electrode structure prior and after stability tests performed by Fourier transform infrared spectroscopy allowed to reveal the main regularities of SC performance and evolution of material properties. [ABSTRACT FROM AUTHOR]

A hybrid LiMn2O4-graphene-carbon nanotubes (LMO-GN-CNT) material is synthesized successfully by a facile hydrothermal method. The 15-nm-nanosized LiMn2O4 (LMO) particles anchor uniformly in the cross-linked conductive graphene (GN) and carbon nanotubes (CNT) matrix in the LMO-GN-CNT composite. Rechargeable hybrid aqueous batteries (ReHABs) are assembled by using LMO-based materials as cathodes and zinc metal as anodes. Galvanostatic charging/discharging cycles of the LMO-GN-CNT composite are performed in rechargeable hybrid aqueous batteries (ReHABs) in comparison of LMO-GN composite and pristine LMO material. Electrochemical measurements indicate that the LMO-GN-CNT composite exhibits superior rate capability and cycle ability. The initial discharge capacity of 129 and 100 mAh g−1 can be delivered at 0.2 and 5.0 C. The discharge capacity is still above 93 mAh g−1, and capacity retention of over 82.1% is obtained after 600 cycles at 2.0 C. The satisfactory electrochemical properties can be ascribed to the little aggregation and good dispersion of the nanosized LMO particles and the introduction of GN and CNT, which can enhance the conductivity, shorten the diffusion length of electrolyte, and provide a large specific surface area for lithium storage. [ABSTRACT FROM AUTHOR]

How to modify carbon materials in a highly efficient manner is an important issue for the practical application. In this work, we demonstrate a hydrothermal approach for modifying nanoporous carbon using H2O2 and H2SO4 as oxygen/sulfur dopants, which can realize the purpose of achieving highly O/S doping. It reveals that hydrothermal temperature and dosage of H2SO4 exert crucial roles for determining the carbon structures and capacitive performances. The change of temperature affects the reaction process, changes the degree of oxidation of carbon by H2O2, and changes the number of oxygen-containing functional groups on carbon surface. Under constant temperature conditions, H2SO4, as a strong oxidizing acid, changes in its dosage will affect the oxidation strength of the system, while changing the number of oxygen-containing functional groups, increasing a certain amount of sulfur-containing functional groups. The specific capacitance of microporous carbon increases from 43 to 168 F g−1, nearly 3.5 times, at a scan rate of 100 mV s−1 in 6 M KOH aqueous electrolyte, under the action of oxygen-containing functional groups, and the cycle stability is also as high as 92%, which is higher than 90% of untreated nanoporous carbon. The energy density of the modified sample is 5.49 Wh kg−1 at the power density of 0.5 kW kg−1. In addition to improving the wettability of carbon materials, oxygen-containing functional groups also produce pseudocapacitance by redox reaction. [ABSTRACT FROM AUTHOR]

In present work, we have developed 2.0 V symmetric supercapacitor with rationally prepared iron tungstate (FeWO4) nanoparticles as electrodes and redox-active electrolyte. It is revealed that the electrochemical performances of FeWO4-system were significantly improved due to the addition of potassium iodide (KI) redox additive in conventional KOH electrolyte in terms of the specific capacitance and energy density. Notably, FeWO4-based symmetric cell with KI-additive shown two-fold enhancement in specific energy (113 Wh/kg) compared with the cell with pristine KOH electrolyte (41.62 Wh/kg). Such an excellent enhancement is attributed to the improvement in the stability of existing KOH electrolyte by KI which influences the strength of OH bond in aqueous media and prevents the breakdown of electrolyte without adversely affecting the redox behavior and on contrary supporting the interactions at the higher potential to produce better results. [ABSTRACT FROM AUTHOR]

A series of sherds from the archeological site of Qotakalli in the area of Cusco (Perú), corresponding to four different Inka periods, were studied by means of square wave voltammetry of immobilized particles (VIMP) and electrochemical impedance spectroscopy (EIS). Ceramic microparticles were placed on a graphite working electrode and were characterized by VIMP and EIS in contact with 0.10 M H2SO4 aqueous electrolyte. Voltammetric features of the sherds, corresponding to the reduction of Fe(III) and Mn(IV) minerals and the oxidation of Fe(II), provided characteristic voltammetric features able to differentiate between different types of ceramic production and Inka periods. A consistent grouping was obtained from VIMP and EIS measurements, mainly responsive to porosity and microstructure variations of the ceramic samples, being also consistent with attenuated total reflectance—Fourier transformed infrared (ATR-FTIR) measurements, scanning electron microscopy (SEM), and optical and structural observations. Grouping of ceramic samples is important to support the archeological proposal of a diverse origin and production of pottery in Qotakalli. [ABSTRACT FROM AUTHOR]

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolyte-filled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10-μm thickness on a 6-μm-thick poly(ethylene-terephthalate) (PET) substrate with a 20-μm diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of − 37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca2+ and Mg2+ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu4+ is shown to 'invert' the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed. [ABSTRACT FROM AUTHOR]

We report herein a high energy density asymmetric supercapacitor cell consisting of polyaniline as a positive electrode and heteroatom-doped activated carbon as a negative electrode in aqueous sulfuric acid electrolyte. Polyaniline is prepared via oxidative polymerization of aniline using hydrothermally prepared manganese dioxide oxidant. Nitrogen and sulfur-doped activated carbon is prepared from AC by hydrothermal synthesis, employing ammonium thiocyanate as a heteroatom precursor. This asymmetric supercapacitor cell is cycled in the voltage range of 0 to 1.4 V, which exhibits an excellent performance with a high specific capacitance of 592 F g−1 and a high energy density of 80 W h kg−1 at a power density of 500 W kg−1, while symmetric cell configuration of individual components of polyaniline//polyaniline and activated carbon//activated carbon shows less performance, i.e., 35 W h kg−1 at 214 W kg−1 and 33 W h kg−1 at 286 W kg−1, respectively. Furthermore, asymmetric cells show good cycling stability retaining over 72% of its initial capacitance even after 10,000 continuous charge-discharge cycles at a higher discharge current, 5 mA. Practical device is demonstrated in the form of a CR2032 coin cell.ᅟ [ABSTRACT FROM AUTHOR]

In this study, a novel potential-triggered electroactive composite film consisting of mesoporous silica SBA-15, polyaniline (PANI), and polystyrenesulfonate (PSS) was fabricated in an aqueous electrolyte solution via a facile pulse potentiostatic method. The obtained composite film was characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric (TG) analysis, and scanning electron microscopy (SEM). The ion exchange properties were evaluated in a solution containing 0.1 M Pb(NO3)2 by using an electrochemical quartz crystal microbalance (EQCM) as well as cyclic voltammetry (CV) method. It was found that the uptake/release of Pb2+ ions in/from SBA-15/PANI/PSS composite film was successfully achieved by modulating the redox states of the electroactive composite film, and the composite film exhibited different ion exchange behaviors at different scan rates. Based on these results, the ion exchange mechanism was proposed. Compared with the PANI/PSS composite film, the SBA-15/PANI/PSS composite film had higher adsorption capacity as well as higher selectivity toward Pb2+ ions, which should be attributed to the 3D porous morphology of the composite film with more active sites in the mesoporous SBA-15. Remarkably, the film maintained a high stability over 97% even after 500 successive cycles. It is expected that this SBA-15/PANI/PSS composite film can serve as a promising electroactive material for the effective separation of Pb2+ ions from wastewater.ᅟ [ABSTRACT FROM AUTHOR]

Electrochemical behavior of poly-3,4-ethylenedioxythiophene composites with manganese dioxide (PEDOT/MnO2) has been investigated by cyclic voltammetry and electrochemical quartz crystal microbalance at various component ratios and in different electrolyte solutions. The electrochemical formation of PEDOT film on the electrode surface and PEDOT/MnO2 composite film during the electrochemical deposition of manganese dioxide into the polymer matrix was gravimetrically monitored. The mass of manganese dioxide deposited into PEDOT at different time of electrodeposition and apparent molar mass values of species involved into mass transfer during redox cycling of PEDOT/MnO2 composites were evaluated. It was found that during the redox cycling of PEDOT/MnO2 composite films with various MnO2 content, the oppositely directed fluxes of counterions (anions and cations) occur, resulting in a change of the slope of linear parts of the Δf-E plots with changing the mass fraction of MnO2 in the composite film.Rectangular shape of cyclic voltammograms of PEDOT/MnO2 composites with different loadings of manganese dioxide was observed, which is characteristic of the pseudocapacitive behavior of the composite material. Specific capacity values of PEDOT/MnO2 composites obtained from cyclic voltammograms were about 169 F g−1. The specific capacity, related to the contribution of manganese dioxide component, was about 240 F g−1. [ABSTRACT FROM AUTHOR]

This work describes lithium nickel vanadate (LiNiVO) as a pseudocapacitor electrode material for the first time. The micro and nano-sized LiNiVO are synthesized via mechanochemical reaction and hydrothermal reaction followed by calcination, respectively. The phase purity, surface morphology and microstructure of the LiNiVO synthesized by both methods are analysed by X-ray diffraction and scanning electron microscopy techniques. The lithium ion intercalation-extraction behaviour of the LiNiVO electrode material is investigated in 1 M LiOH electrolyte solution. The results demonstrate an improved capacitive performance for nano-sized LiNiVO electrode synthesized via hydrothermal reaction due to the collective effect of small size and additional redox sites. The nanocrystalline LiNiVO electrode exhibits a high specific capacitance of 456.56 F g at a current density of 0.5 A g. The cycle stability test reveals exceptional capacitance retention of 99.60% even after 1000 cycles owing to the unique structural feature which permit intercalation mechanism. These findings demonstrate the significance of lithium transition metal vanadate-based electrode material in the development of lithium ion intercalation pseudocapacitors. [ABSTRACT FROM AUTHOR]

Electric double-layer capacitors (EDLCs) are composed of two activated carbon (AC) electrodes and an electrolyte/separator, in which the ACs contain numbers of surface oxygen functionalities (SOFs). In this work, the effect of SOFs on the EDLC's capacitance in non-aqueous electrolytes is studied by using a 1.0 m (molality) LiPF 3:7 (wt.) ethylene carbonate-ethyl methyl carbonate electrolyte and a commercial activated carbon. Results show that the SOFs on one hand contribute to Faradic pseudocapacitance, and on the other hand adversely reduce the EDLC's performances, including the initial reversibility, coulombic efficiency, and capacitance retention. It is found that the AC behaves significantly different in the Li/AC half cells and in the AC/AC full cells and that the SOF's pseudocapacitance increases with widening the EDLC's operating voltage. The latter is attributed to the large-voltage hysteresis of the redox of SOFs. In this paper, the AC's unique behaviors in Li salt electrolyte are presented, and a possible mechanism for the observed behaviors is proposed. [ABSTRACT FROM AUTHOR]

The activated carbon was modified by the wet method with a solution of ammonium persulfate at room temperature with different times. Kinetics studies showed that the modification took place mostly during the first 60 min of the process. The physicochemical properties of the obtained carbon were evaluated by thermogravimetric studies, Raman and FTIR spectroscopy, elementary and BET analyses. Furthermore, the fabricated material was applied in symmetric capacitors operated on the three aqueous electrolytes (1 M HSO, 6 M KOH and 1 M NaSO). Mild conditions of the modification process are optimal to obtain electroactive groups on the carbon surface, which make this material useful in a supercapacitor application. In our studies, we noticed that this type of functional groups mainly appears on the surface of the activated carbon, in the first oxidation stage. With prolonged oxidation, they may transform into undesirable groups. The results show that this kind of modification improves the capacity of all the tested supercapacitors. It was connected mainly with an increase of the carbon material's wettability and in the case of capacitor operated in acid and base electrolytes due to a redox reaction of oxygen functional groups. [ABSTRACT FROM AUTHOR]

Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different temperatures (600, 700 and 800 °C) using potassium hydroxide (KOH) pellets as an activation agent with different mass loading. The physicochemical and microstructural characteristics of the as-obtained material revealed interconnected microporous/mesoporous architecture with increasing trend in specific surface area (SSA) as carbonization temperatures rises. The SSA values of up to 1018 m g and a high pore volume of 0.67 cm g were obtained. The potential of the ACB material as suitable supercapacitor electrode was investigated in both a three and two-electrode configuration in different neutral aqueous electrolytes. The electrodes exhibited electric double-layer capacitor (EDLC) behaviour in all electrolytes with the NaSO electrolyte working reversibly in both the negative (−0.80 V to −0.20 V) and positive (0.0 V to 0.6 V) operating potentials. A specific capacitance ( C ) of up to 191 F g at a current density of 1 A g was obtained for the optimized ACB electrode material in 1 M NaSO electrolyte . A symmetric device fabricated exhibited specific C of 114 F g at 0.3 A g and excellent stability with a coulombic efficiency of a 100 % after 5000 constant charge-discharge cycles at 5.0 A g and a low capacitance loss for a floating time of 70 h. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate a safe, inexpensive, and stable cycle-life aqueous rechargeable Li-ion battery system using tavorite LiTiPOF as anode and Li[LiCoMn]O as cathode in aqueous electrolyte using 2 M LiSO. These materials have been synthesized via a simple and an efficient method called RAPET (reaction under autogenic pressure at elevated temperature) method, and for the first time, we have evaluated the electrochemical properties of LiTiPOF in aqueous electrolyte. Structural and morphological features have been characterized using X-ray diffraction and scanning electron microscopy techniques, and the electrochemical studies have been investigated by using cyclic voltammetry, galvanostatic charge/discharge studies, electrochemical impedance spectroscopic technique, potentiostatic intermittent titration techniques, and galvanostatic intermittent titration techniques. In galvanostatic charge/discharge studies, the capacity, cycle life, and columbic efficiency of LiTiPOF have been tested in combination with Li [LiCoMn]O cathode. In particular, LiTiPOF shows capacity of 82 mA h g, the capacity retention was maintained 90 % even after the 45th cycle. [ABSTRACT FROM AUTHOR]

Nitrobenzene was found dissimilar to 1,2-dichloroethane and chloroform in electrodeposition of electronically conducting polypyrrole at a water/organic solvent junction by means of the three-phase electrode. Morphologies of the two sides of the potentiostatically deposited, freestanding thin polymer films differ distinctly which might be of interest for specific applications. A low temperature of the synthesis at the liquid-liquid junction is preferable for attaining the homogeneous surface morphologies of the polymer films. [ABSTRACT FROM AUTHOR]

Focused ion beam scanning electron microscopy (FIB-SEM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller gas adsorption methods have been used for the characterisation of physical properties of microporous carbide-derived carbon electrodes, prepared from MoC at 600 °C (noted as MoC-CDC) before and after electrochemical tests conducted within a very wide two-electrode cell potential region. Cyclic voltammetry, constant current charge/discharge and impedance data have been analysed to establish the electrochemical characteristics of the hybrid devices consisting of the 1 M NaSO and 1 M RbSO aqueous electrolytes and MoC-CDC electrodes within the very wide cell potential region (Δ E ≤ 2.4 V). The influence of cation chemical composition on the electrochemical characteristics of supercapacitors/electrochemical hybrid devices has been analysed. The complex kinetics behaviour of completed devices (adsorption, blocking adsorption and intercalation of Na and Rb ions; faradic and mass transfer; gas adsorption; etc.) has been established at Δ E ≥ 1.5 V. At least three different characteristic time constants dependent on the electrolyte cation composition and cell potential applied have been established. [ABSTRACT FROM AUTHOR]