Search Results (86)

The advancement of non-aqueous redox flow batteries (NARFBs) remains significantly constrained by the absence of membranes with sufficient ionic selectivity and chemical compatibility. Herein, we fabricated flexible membranes incorporating metal–organic framework (MOF) via a solution casting approach. The rigid framework structure of the MOF effectively suppresses membrane swelling in organic solvents. The appropriate structural pore of MOF enables a size-sieving effect toward redox-active materials and supporting electrolyte, thereby reducing material crossover and enhancing the ionic selectivity of the composite membranes. The batteries with the designed composite membranes exhibit a Coulombic efficiency of higher than 99% and significantly improved cycling stability at 10 mA cm⁻². The membrane design strategy, employing MOF materials with a structural pore size between the molecular size of the supporting electrolyte and active materials, is universal for NARFB. Full article

Supercapacitors are promising energy storage devices that combine high power density, fast charge/discharge rates, and excellent cycling stability. However, their relatively low energy density compared to batteries remains a major challenge. To address this limitation, redox additive electrolytes have emerged as a key strategy to introduce reversible Faradaic reactions, significantly enhancing the energy storage capacity of supercapacitors. This mini-review systematically summarizes recent advancements in the use of redox-active species across aqueous, non-aqueous, and solid-state/gel electrolytes. We highlight the role of both inorganic and organic redox additives, detailing their mechanisms, advantages, and limitations in improving energy density and stability. Furthermore, we discuss the challenges associated with redox species, such as solubility, long-term stability, and parasitic side reactions, which hinder their practical applications. Future research directions are proposed to optimize redox-active materials and electrolyte systems, aiming to develop next-generation supercapacitors with superior energy density, extended cycling life, and enhanced applicability. Full article

The current electrolytes used for metal electrodeposition mostly use aqueous solutions that limit the range and quality of possible coatings. Also, some of these solutions may contain toxic and corrosive chemicals. Thus, the importance of ionic liquids (ILs) and deep eutectic solvents (DES) becomes clear, as they can be used as green non-aqueous electrolytes for the electrodeposition of a range of reactive metals that are impossible to deposit in aqueous solutions and for the improved electrodeposition of metals that are deposable in aqueous solutions. This paper presents some examples of electrodeposition in ILs and DESs that are considered specific processes. Aluminum, as an active metal that it is impossible to electrodeposit in aqueous solution, was electrodeposited from a chloroaluminate IL. Moreover, the electrodeposition of Al was carried out in open air using a novel approach. Chromium was electrodeposited from a DES containing the environmentally friendly form of Cr (III) instead of toxic Cr (VI). Magnesium alloys, as water-sensitive substrates, were electroplated in an air and water-stable DES. Also, this paper discloses, for the first time, the procedure of pretreatment of Mg alloys for successful electroplating. Full article

Prussian blue PB analogues (K;Mg)_xM[Fe(CN)₆] were obtained via the co-precipitation method. Manganese, iron, cobalt, nickel, copper and zinc were selected to obtain the metal hexacyanoferrates (MHCFs) of these metals and to systematically study their structural and electrochemical properties as cathode materials. The obtained substances were characterized via X-ray powder analysis, scanning electron microscopy, thermogravimetric analysis and elemental analysis. An electrochemical study of the obtained cathode materials relative to a platinum anode in an aqueous medium and a magnesium anode in a nonaqueous medium was carried out, and the cycling parameters were determined. The influence of 3d-metal nature on the composition–structure–properties of hexacyanoferrates was demonstrated. MHCFs are promising cathode materials for Mg²⁺ intercalation/deintercalation in aqueous electrolytes. Full article

The application of deep eutectic solvents (DESs) as an innovative class of environmentally friendly liquid media represents a significant advancement in materials science, especially for the development and enhancement of structural materials. Among the promising applications, DESs are particularly attractive for the electrodeposition of corrosion-resistant coatings. It is established that corrosion-resistant and protective coatings, including those based on metals, alloys, and composite materials, can be synthesized using both traditional aqueous electrolytes and non-aqueous systems, such as organic solvents and ionic liquids. The integration of DESs in electroplating introduces a unique capacity for precise control over microstructure, chemical composition, and morphology, thereby improving the electrochemical corrosion resistance and protective performance of coatings. This review focuses on the electrodeposition of corrosion-resistant and protective coatings from DES-based electrolytes, emphasizing their environmental, technological, and economic benefits relative to traditional aqueous and organic solvent systems. Detailed descriptions are provided for the electrodeposition processes of coatings based on zinc, nickel, and chromium from DES-based baths. The corrosion–electrochemical behavior and protective characteristics of the resulting coatings are thoroughly analyzed, highlighting the potential and future directions for developing anti-corrosion and protective coatings using DES-assisted electroplating techniques. Full article

A comprehensive, three-dimensional, macro-scale model was developed to simulate non-aqueous deep eutectic solvent (DES) electrolyte flow batteries. The model’s feasibility was validated by comparing the simulated polarization data with the experimental results. Utilizing this model, the work reported here compared the flow characteristics and electrochemical properties of electrolytes with different redox couples within the porous electrodes of the batteries. Despite variations in the active materials, the distribution of the electrolyte flow rate showed uniformity due to consistent electrode and flow channel designs, indicating that the structural design of electrodes and channels has a more significant impact on electrolyte flow than the physicochemical properties of the electrolytes themselves. This study also highlighted that TEMPO and Quinoxaline DES electrolytes exhibited less flow resistance and more uniform concentration distributions, which helped reduce overpotentials and enhance battery energy efficiency. Furthermore, this research identified that the highest average overpotentials occurred near the membrane for all the redox couples, demonstrating that electrochemical reactions in DES electrolyte flow batteries primarily occur in the region close to the membrane. This finding underscores the importance of optimizing active redox ions transport in electrolytes to enhance electrochemical reactions in the proximal membrane region, which is crucial for improving flow battery performance. Full article

Nafion^® is a cation exchange polymer that is commonly used in aqueous energy applications such as fuel cells due to its ability to exclude anions and neutral molecules and increase apparent diffusion of cationic redox molecules. However, this behavior is not well studied in nonaqueous solutions. The behavior of platinum electrodes modified with recast Nafion^® films in nonaqueous solutions was observed to be different from its well-studied behavior in aqueous solutions. The reversible redox couple tris(2,2′-bipyridine)ruthenium(II) hexafluorophosphate was studied in the nonaqueous, aprotic solvent acetonitrile with different electrolytes (tetrabutylammonium tetrafluoroborate, tetrabutylammonium trifluoromethanesulfonate, tetrabutylammonium hexafluorophosphate, and ammonium trifluoromethanesulfonate) using cyclic voltammetry and rotating disk voltammetry. An unmodified platinum electrode in the nonaqueous systems and a recast Nafion^®-modified platinum electrode equilibrated in an aqueous solution of tris(bipyridine)ruthenium(II)chloride hexahydrate were used as controls. Results indicate that the polymer structure in acetonitrile conditions does not allow apparent (Dahms–Ruff) diffusion but does allow significant physical diffusion that would make Nafion a great immobilization option for modifying electrodes with catalysts in nonaqueous systems. Full article

The fast-growing area of battery technology requires the availability of highly stable, energy-efficient batteries for everyday applications. This, in turn, calls for research into new battery materials, especially with regard to a battery’s main component: the electrolytes. Besides the demands associated with solid ionic conduction and appropriate electrochemical behaviour, considerable effort will be necessary to thoroughly reduce safety risks in terms of flammability, leakage, and thermal runaway. Consequently, completely new classes of electrolytes need to be developed that are compatible with energy storage systems. Despite the progress made in solid polymer electrolytes, such materials have suffered from limitations to their real-world application. Now, ionic liquids are considered a class of electrolytes with the most potential for the creation of more advanced and safer lithium–ion batteries. In recent decades, ILs have been widely explored as potential electrolytes in the search for new breakthroughs in the ESS field, such those associated with fuel cells, lithium–ion batteries, and supercapacitors. The present review will discuss ILs that present high ionic conductivity, a lower melting point below 100 °C, and which feature up to 5–6 V wide electrochemical potential windows vs. Li⁺/Li. Furthermore, ILs exhibit good thermal stability, non-flammability, and low volatility—all of which are attributes realized by appropriate cation–anion combinations. This paper seeks to review the status of research concerning ILs, along with the advantages and challenges yet to be overcome in their development. Full article

Deep eutectic solvents (DESs) have attracted much attention as sustainable electrolytes for redox flow batteries. Despite the tremendous advantages of DES-based electrolytes, their high viscosity property has a negative effect on their mass transfer, limiting current density and power density. The ultrasonic effect has been demonstrated as an efficient strategy to improve mass transfer characteristics. Incorporating ultrasonic waves into a deep eutectic solvent (DES) electrolyte enhances the mobility of redox-active ions, thereby accelerating the reaction dynamics of the Fe(III)/Fe(II) redox pair. This enhancement makes it suitable for use in non-aqueous electrolyte-based redox flow batteries. However, it is necessary to consider the loss of ultrasonic on the internal structure of the battery, as well as the loss of battery component materials and ultrasonic energy consumption in practical applications. Moreover, the continuous extension of the duration of ultrasonic action not only hardly leads to a more significant improvement of the battery performance, but is also detrimental to the energy and economic savings. Herein, intermittent ultrasound is used to overcome the quality transfer problem and reduce the operating cost. Good electrochemical performance enhancement is maintained with a roughly 50% reduction in energy consumption values. The mechanism as well as the visualization of the pulsed ultrasonic field on each half cell has been envisaged through fundamental characterization. Finally, the feasibility of interrupted ultrasonic activation applied to Fe/V RFB using DES electrolytes has been demonstrated, demonstrating similar behavior with continuous ultrasonic operation. Therefore, the interrupted ultrasonic field has been found to be a more effective operation mode in terms of energy cost, avoiding alternative undesirable effects like overheating or corrosion of materials. Full article

As the object of investigation in the present study, reactive distillation based on the transesterification of isopropyl acetate (IPAc) and 2,2,3,3,4,4,4-heptafluorobutanol (HFBol) under acidic conditions is addressed. This process aims to obtain 2,2,3,3,4,4,4-heptafluorobutyl acetate (HFBAc), which is used in the production of non-aqueous electrolytes, ethyllithium sulphate, charge retention medium, ultraviolet light-absorbing oligomers, etc. Through a combination of NMR spectroscopy and GC-MS, it was determined that during the process, the following were primarily formed in the system: target HFBAc and the by-product, isopropanol. The following side-products were identified: di-isopropyl ether, acetic acid, water, and 2,2,3,3,4,4,4-heptafluorobutyl isopropyl ether (HFB-IPEth). No bis(1H,1H-heptafluorobutyl) ether or acetic anhydride were identified in the system. For HFBol, HFBAc and HFB-IPEth the ¹H, ¹⁹F and ¹³C{¹⁹F}), ¹⁹F-¹⁹F COSY NMR, and mass spectra were reported in this study. Full article

In the current context of increasing energy demand, ionic liquids (ILs) are presented as possible candidates to replace conventional electrolytes and to develop more efficient energy storage devices. The IL 1-Methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide has been selected for this work, due to the good thermal and chemical stabilities and good electrochemical performance of the pyrrolidinium cation based ILs. Binary mixtures of this IL and lithium salt with the same anion, [TFSI], have been prepared with the aim of assessing them, as possible electrolytes for lithium batteries. These mixtures were thermally and electrochemically characterised through DSC and dielectric spectroscopy studies. The ionic conductivity decreases as the salt concentration increases, finding values ranging between 0.4 S/m and 0.1 S/m at room temperature. Additionally, a wide liquid range was found for the mixtures, which would reduce or even eliminate some of the most common problems of current electrolytes, such as their crystallisation at low temperatures and flammability. Finally, the toxicity of pure IL and the intermediate salt concentration was also evaluated in terms of the bioluminescence inhibition of the Alivibrio Fischeri bacteria, observing that, although the toxicity increases with the salt addition, both samples can be classified as practically harmless. Full article

CdS, CdTe, Hg_0.1Cd_0.9Te, CdTe, and Ag films were progressively electrodeposited on ITO-coated soda–lime glass to manufacture a short- and mid-wavelength infrared photodetector. A distinctive feature of the applied electrodeposition method is the use of a non-aqueous solution containing ethylene glycol (EG) as the electrolyte in a traditional three-electrode configuration for every film deposition. Using EG as a supplementary electrolyte and using the same deposition conditions with a potential below 0.75 V for all film coatings reduces their environmental incompatibility and offers a low-cost and low-energy route for fabricating the reported photodetector. The produced photodetector has a sensitivity of up to ≈957 nm with a detectivity (D*) of 2.86 × 10¹² cm Hz^1/2 W⁻¹ and a dark current density (J_dark) of 10⁻⁶ mA cm⁻². Furthermore, the manufactured photodiode exhibits self-powered performance because V_oc and J_sc are self-generated, unlike previously reported photodiodes. The presented all-layer electrodeposition assembly approach can easily be adapted to fabricate sensing devices for different applications. Full article

This paper reports the results of our study on electrochemical polishing of titanium and a Ti-based alloy using non-aqueous electrolyte. It was shown that electropolishing ensured the removal of surface defects, thereby providing surface smoothing and decreasing surface roughness. The research was conducted using samples made of titanium and Ti₆Al₄V alloy, as well as implant system elements: implant analog, multiunit, and healing screw. Electropolishing was carried out under a constant voltage (10–15 V) with a specified current density. The electrolyte used contained methanol and sulfuric acid. The modified surface was subjected to a thorough analysis regarding its surface morphology, chemical composition, and physicochemical properties. Scanning electron microscope images and profilometer tests of roughness confirmed significantly smoother surfaces after electropolishing. The surface profile analysis of processed samples also yielded satisfactory results, showing less imperfections than before modification. The EDX spectra showed that electropolishing does not have significant influence on the chemical composition of the samples. Full article

Polyaniline (PANI) has long been explored as a promising organic cathode for Li-ion batteries. However, its poor electrochemical utilization and cycling instability cast doubt on its potential for practical applications. In this work, we revisit the electrochemical performance of PANI in nonaqueous electrolytes, and reveal an unprecedented reversible capacity of 197.2 mAh g⁻¹ (244.8 F g⁻¹) when cycled in a wide potential range of 1.5 to 4.4 V vs. Li⁺/Li. This ultra-high capacity derives from 70% -NH- transformed to =NH⁺- during deep charging/discharging process. This material also demonstrates a high average coulombic efficiency of 98%, an excellent rate performance with 73.5 mAh g⁻¹ at 1800 mA g⁻¹, and retains 76% of initial value after 100 cycles, which are among the best reported values for PANI electrodes in battery applications. Full article

In order to expand the application of bismuth vanadate (BiVO₄) to the field of photoelectrochemistry, researchers have explored the potential of BiVO₄ in catalyzing or degrading organic substances, potentially presenting a green and eco-friendly solution. A study was conducted to investigate the impact of electrolytes on the photocatalysis of benzyl alcohol by BiVO₄. The research discovered that, in an acetonitrile electrolyte (pH 9) with sodium bicarbonate, BiVO₄ catalyzed benzyl alcohol by introducing saturated V⁵⁺. This innovation addressed the issue of benzyl alcohol being susceptible to catalysis in an alkaline setting, as V⁵⁺ was prone to dissolution in pH 9 on BiVO₄. The concern of the photocorrosion of BiVO₄ was mitigated through two approaches. Firstly, the incorporation of a non-aqueous medium inhibited the formation of active material intermediates, reducing the susceptibility of the electrode surface to photocorrosion. Secondly, the presence of saturated V⁵⁺ further deterred the leaching of V⁵⁺. Concurrently, the production of carbonate radicals by bicarbonate played a vital role in catalyzing benzyl alcohol. The results show that, in this system, BiVO₄ has the potential to oxidize benzyl alcohol by photocatalysis. Full article