Electrodeposition in Ionic Liquids

Eco-Friendly Production of Boron Nitride Nanosheets via Deep Eutectic Solvents and Their Application in Enhancing Thermal Conductivity of PVDF Composites

Boron nitride nanosheets (BNNS) are expected to be ideal fillers because of their high thermal conductivity and excellent electrical insulation. However, it is still an open challenge to produce BNNS on a large scale using ecofriendly solvents. Here, first, we demonstrate an effective liquid exfoliation method for producing BNNS via utilizing deep eutectic solvents (DES) composed of D,L-menthol and various acids with the assistance of ultrasonication. The results show that the BNNSs with sizes of 1-2 μm in width and 6-8 nm in thickness were successfully exfoliated with a DES formulation of D,L-menthol and decanoic acid. Second, the obtained BNNSs were used for fabricating 1,6-hexanediol diacrylate@polydopamine functionalized BNNS (HDDA@BNNSs-PDA) core-shell microspheres via a Pickering emulsion method. Furthermore, these microspheres were incorporated into a polyvinylidene fluoride (PVDF) matrix to construct 3D thermally conductive networks, leading to a substantial enhancement in the thermal conductivity of the resulting composites. Impressively, the composites with only 25 wt % of BNNS loading reach a high thermal conductivity of 3.20 W/m K, which is a 1500% increase over the pure polymer matrix. This work not only provides a significant way for producing BNNSs ecofriendly but also demonstrates a tactic for constructing 3D thermally conductive networks.

Translational and reorientational dynamics in carboxylic acid-based deep eutectic solvents

The glass formation and the dipolar reorientational motions in deep eutectic solvents (DESs) are frequently overlooked, despite their crucial role in defining the room-temperature physiochemical properties. To understand the effects of these dynamics on the ionic conductivity and their relation to the mechanical properties of the DES, we conducted broadband dielectric and rheological spectroscopy over a wide temperature range on three well-established carboxylic acid-based natural DESs. These are the eutectic mixtures of choline chloride with oxalic acid (oxaline), malonic acid (maline), and phenylacetic acid (phenylaceline). In all three DESs, we observe signs of a glass transition in the temperature dependence of their dipolar reorientational and structural dynamics, as well as varying degrees of motional decoupling between the different observed dynamics. Maline and oxaline display a breaking of the Walden rule near the glass-transition temperature, while the relation between the dc conductivity and dipolar relaxation time in both maline and phenylaceline is best described by a power law. The glass-forming properties of the investigated systems not only govern the orientational dipolar motions and rheological properties, which are of interest from a fundamental point of view, but they also affect the dc conductivity, even at room temperature, which is of high technical relevance.

Structural Properties of HEHN- and HAN-Based Ionic Liquid Mixtures: A Polarizable Molecular Dynamics Study

Molecular dynamics simulations of binary mixtures comprising 2-hydroxyethylhydrazinium nitrate (HEHN) and hydroxylammonium nitrate (HAN) were conducted using the polarizable APPLE&P force field to investigate fundamental properties of multimode propulsion (MMP) propellants. Calculated densities as a function of temperature were in good agreement with experiments and similar simulations. The structural properties of neat HEHN and HAN-HEHN provided insights into their inherent, protic nature. Radial distribution functions (RDFs) identified key hydrogen bonding sites located at N-H···O and O-H···O within a first solvation shell of approximately 2 Å. Angular distribution functions further affirmed the relatively strong nature of the hydrogen bonds with nearly linear directionality. The increased hydroxylammonium cation (HA+) mole fraction shows the influence of competitively strong hydrogen bonds on the overall hydrogen bond network. Dominant spatial motifs via three-dimensional distribution functions along with nearly nanosecond-long hydrogen bond lifetimes highlight the local bonding environment that may precede proton transfer reactions.

Gallium(III)- and Indium(III)-Containing Ionic Liquids as Highly Active Catalysts in Organic Synthesis

The chemical industry still requires development of environmentally friendly processes. Acid-catalysed chemical processes may cause environmental problems. Urgent need to replace conventional acids has forced the search for sustainable alternatives. Metal-containing ionic liquids have drawn considerable attention from scientists for many years. These compounds may exhibit very high Lewis acidity, which is usually dependent on the composition of the ionic liquid with the particular content of metal salt. Therefore, metal-containing ionic liquids have found a lot of applications and are successfully employed as catalysts, co-catalysts or reaction media in various fields of chemistry, especially in organic chemistry. Gallium(III)- and indium(III)-containing ionic liquids help to transfer the remarkable activity of metal salts into even more active and easier-to-handle forms of ionic liquids. This review highlights the wide range of possible applications and the high potential of metal-containing ionic liquids with special focus on Ga(III) and In(III), which may help to outline the framework for further development of the presented research topic and synthesis of new representatives of this group of compounds.

Impact of Surface Roughness on Partition and Selectivity of Ionic Liquids Mixture in Porous Electrode

Understanding the influence of surface roughness on the adsorption of ions from an ionic liquids (ILs) mixture is essential for designing supercapacitors. The classical density functional theory (DFT) is applied to investigate the adsorption behavior of ILs mixtures in rough nanopores. The model parameters for each ion are determined by fitting experimental data of pure IL density. The results show that the smaller anions are densely accumulated near the rough surface and are the dominant species at a high positive potential. The exclusion of larger anions is enhanced by roughness at almost all potentials. At negative potential, the surface roughness promotes the adsorption of cations, and the partition coefficient increases with roughness. The partition coefficient of smaller anions is virtually independent of roughness. At positive potential, the surface roughness only promotes the adsorption of smaller anions and raises the partition coefficient. The partition coefficient of smaller anions is far greater than one. The selectivity of smaller anions for rough surfaces is very high and increases with roughness. The surface charge of a more uneven surface is significantly higher (about 30%) at a high potential.

Ionic liquids as electrolytes in aluminum electrolysis

Herein, the characteristics, research progress, and application prospects of ionic liquid-based electrolytic aluminum deposition are reviewed and analyzed in comparison with the Hall–Héroult method. The reaction conditions and production procedures of this material are discussed alongside the problems ionic liquids face in the electrolytic aluminum industry. Ionic liquid-based electrolytic aluminum deposition realizes the electrolytic aluminum reaction at low temperatures, achieving a reaction energy consumption close to the theoretical minimum value. The reaction also avoids harmful CO₂ or HF emissions, demonstrating a green and environmental-friendly approach to the production of electrolytic aluminum. In the future, in-depth work on the implementation of ionic liquid electrolytes should be carried out, establishing the necessary technical criteria and laying the foundation for the integration of this approach.

Decomposition of Deep Eutectic Solvent Aids Metals Extraction in Lithium-Ion Batteries Recycling

The application of deep eutectic solvents (DESs) to dissolve metal oxides in lithium-ion batteries (LIBs) recycling represents a green technological alternative to the mineral acids employed in hydrometallurgical recycling processes. However, DESs are much more expensive than mineral acids and must be reused to ensure economic feasibility of LIB recycling. To evaluate DES reusability, the role of the choline chloride-ethylene glycol DES decomposition products on metal oxides dissolution was investigated. The temperatures generally applied to carry on this DES leaching induced the formation of decomposition products that ultimately improved the ability to dissolve LIB metal oxides. The characterization of DES decomposition products revealed that the improved metal dissolution was mainly determined by the formation of Cl₃ ^- , which was proposed to play a pivotal role in the oxidative dissolution of LIB metal oxides.

Electrochemical behavior of ionic and metallic zirconium in ionic liquids

Metallic zirconium has a broad range of potential applications in engineering and in industries that are operating under harsh corrosive environments, such as nuclear and chemical industry. Compared to other metals like aluminum, its behavior in electrochemical reactions is poorly understood and so far, there are no larger-scale electrochemical approaches to process zirconium. Ionic liquids are a suitable reaction medium for electrochemical reactions of zirconium. To better understand the electrochemical reactivity of zirconium, different combinations of ionic liquids and zirconium precursors are investigated. It was found that interactions between the Zr precursor and the ionic liquids can have significant influence on the diffusion properties of Zr. Furthermore, mixtures of ionic liquids with other solvents were explored and it could be determined that most of the electrochemical properties of Zr are retained also in solvent mixtures. This could potentially save costs for industrial applications, as lower amounts of the ionic liquids can be used, to obtain similar electrochemical properties.

Effect of surface roughness on partition of ionic liquids in nanopores by a perturbed-chain SAFT density functional theory

In this work, the distribution and partition behavior of ionic liquids (ILs) in nanopores with rough surfaces are investigated by a two-dimensional (2D) classical density functional theory (DFT) model. The model is consistent with the equation of state (EoS) that combines the perturbed-chain statistical associating fluid theory (PC-SAFT) and the mean spherical approximation (MSA) theory for bulk fluid. Its performance is verified by comparing the theoretical predictions to the results from molecular simulations. The fast Fourier transform (FFT) and a hybrid iteration method of Picard iteration and Anderson mixing are used to efficiently obtain the solution of density profile for the sizeable 2D system. The molecular parameters for IL-ions are obtained by fitting to experimental densities of bulk ILs. The model is applied to study the structure and partition of the ILs in nanopores. The results show that the peak of the density profile of counterions near a rough surface is much higher than that near a smooth surface. The adsorption of counterion and removal of coions are enhanced by surface roughness. Thus the nanopore with rough surfaces can store more charge. At low absolute surface potential, the partition coefficient for ions on rough surfaces is lower than that on smooth surfaces. At high absolute surface potential, increasing surface roughness leads to an increase in partition coefficient for counterions and a decrease in partition coefficient for coions.

Ionic Liquids and Deep Eutectics as a Transformative Platform for the Synthesis of Nanomaterials

Ionic liquids (ILs) are becoming a revolutionary synthesis medium for inorganic nanomaterials, permitting more efficient, safer and environmentally benign preparation of high quality products. A smart combination of ILs and...

Electrochemical Synthesis of Unique Nanomaterials in Ionic Liquids

The review considers the features of the processes of the electrochemical synthesis of nanostructures in ionic liquids (ILs), including the production of carbon nanomaterials, silicon and germanium nanoparticles, metallic nanoparticles, nanomaterials and surface nanostructures based on oxides. In addition, the analysis of works on the synthesis of nanoscale polymer films of conductive polymers prepared using ionic liquids by electrochemical methods is given. The purpose of the review is to dwell upon an aspect of the applicability of ILs that is usually not fully reflected in modern literature, the synthesis of nanostructures (including unique ones that cannot be obtained in other electrolytes). The current underestimation of ILs as an electrochemical medium for the synthesis of nanomaterials may limit our understanding and the scope of their potential application. Another purpose of our review is to expand their possible application and to show the relative simplicity of the experimental part of the work.

Inorganic Synthesis Based on Reactions of Ionic Liquids and Deep Eutectic Solvents

Ionic liquids and deep eutectic solvents are of growing interest as solvents for the resource‐efficient synthesis of inorganic materials. This Review covers chemical reactions of various deep eutectic solvents and types of ionic liquids, including metal‐containing ionic liquids, [BF₄]⁻‐ or [PF₆]⁻‐based ionic liquids, basic ionic liquids, and chalcogen‐containing ionic liquids. Cases in which cations, anions, or both are incorporated into the final products are also included. The purpose of this Review is to raise caution about the chemical reactivity of ionic liquids and deep eutectic solvents and to establish a guide for their proper use.

Electrochemical Approaches for the Recovery of Metals from Electronic Waste: A Critical Review

Electronic waste (e-waste) management and recycling are gaining significant attention due to the presence of precious, critical, or strategic metals combined with the associated environmental burden of recovering metals from natural mines. Metal recovery from e-waste is being prioritized in metallurgical extraction owing to the fast depletion of natural mineral ores and the limited geographical availability of critical and/or strategic metals. Following collection, sorting, and physical pre-treatment of e-waste, electrochemical processes-based metal recovery involves leaching metals in an ionic form in a suitable electrolyte. Electrochemical metal recovery from e-waste uses much less solvent (minimal reagent) and shows convenient and precise control, reduced energy consumption, and low environmental impact. This critical review article covers recent progress in such electrochemical metal recovery from e-waste, emphasizing the comparative significance of electrochemical methods over other methods in the context of an industrial perspective.

Deep Eutectic Solvents: Molecular Simulations with a First-Principles Polarizable Force Field

The unique properties of deep eutectic solvents make them useful in a variety of applications. In this work we develop a first-principles force field for reline, which is composed of choline chloride and urea in the molar ratio 1:2. We start with the symmetry adapted perturbation theory (SAPT) protocol and then make adjustments to better reproduce the structure and dynamics of the liquid when compared to first-principles molecular dynamics (FPMD) simulations. The resulting force field is in good agreement with experiments in addition to being consistent with the FPMD simulations. The simulations show that primitive molecular clusters are preferentially formed with choline-chloride ionic pairs bound with a hydrogen bond in the hydroxyl group and that urea molecules coordinate the chloride mainly via the trans-H chelating hydrogen bonds. Incorporating polarizability qualitatively influences the radial distributions and lifetimes of hydrogen bonds and affects long-range structural order and dynamics. The polarizable force field predicts a diffusion constant about an order of magnitude larger than the nonpolarizable force field and is therefore less computationally intensive. We hope this study paves the way for studying complex hydrogen-bonding liquids from a first-principles approach.

Effects of Ionic Liquids on Aqueous Urea Solutions: Insights into the Ionic Liquid-Assisted Protein Renaturation

Ionic liquids (ILs) are designer solvents that find wide applications in various areas. Recently, ILs have been shown to induce the refolding of certain proteins that were previously denatured under the treatment of urea. A molecular-level understanding of the counteracting mechanism of ILs on urea-induced protein denaturation remains elusive. In this study, we employ atomistic molecular dynamics simulations to investigate the ternary urea-water-IL solution in comparison to the aqueous urea solution to understand how the presence of ILs can modulate the structure, energetics, and dynamics of urea-water solutions. Our results show that the ions of the IL used, ethylammonium nitrate (EAN), interact strongly with urea and disrupt the urea aggregates that were known to stabilize the unfolded state of the proteins. Results also suggest a disruption in urea-water interaction that releases more free water molecules in solution. We subsequently strengthened these findings by simulating a model peptide in the absence and presence of EAN, which showed broken versus intact secondary structure in urea solution. Analyses show that these changes were accomplished by the added IL, which enforced a gradual displacement of urea from the peptide surface by water. We propose that the ILs facilitate protein renaturation by breaking down the urea aggregates and increasing the amount of free water molecules around the protein.

Controlling Interfacial Ion-Transport Kinetics Using Polyelectrolyte Membranes for Additive- and Effluent-free, High-Performance Electrodeposition

The development of high-performance, environmentally friendly electrodeposition processes is critical for emerging coating technologies because current technologies use highly complex baths containing metal salts, supporting electrolytes, and various kinds of organic additives, which are problematic from both environmental and cost perspectives. Here, we show that a 200 μm-thin polyelectrolyte membrane sandwiched between electrodes effectively concentrates metal ions through interfacial penetration, which increases the conductance between the electrodes to 0.30 S and realizes solid-state electrodeposition that produces no mist, sludge, or even waste effluent. Both, experimental results and theoretical calculations, reveal that electrodeposition is controlled by ion penetration at the solution/polyelectrolyte interface, providing an intrinsically different ion-transport mechanism to that of conventional diffusion-controlled electrodeposition. The setup, which includes 0.50 mol L^-1 copper sulfate and no additives, delivers a maximum current density of 300 mA cm^-2, which is nearly fivefold higher than that of a current commercial plating bath containing organic additives.

A Review on the Electrodeposition of Aluminum and Aluminum Alloys in Ionic Liquids

Aluminum plays an essential role as an excellent coating material in diversified applications due to its better corrosion resistance and physicochemical properties. Employing such a material as a coating on different metallic substrates such as carbon steel would benefit many industries such as the automotive, aviation, shipbuilding, construction, electronics etc. Amongst the various available coating techniques, electrodeposition of aluminum (Al) Al alloys have gained significant attention in the last 10 years as a metallic protection coating for various commercial substrates and has become the industry’s choice owing to being lightweight, corrosion-resistant, and cost-effective. This paper shall provide a detailed review covering electrochemical deposition of Al and Al alloys using ionic liquids with various cations, anions, and additives, and reports on progress in development thus far. It shall also cover the challenges in the electrodepositing aluminum, its alloys on light weight metal substrates viz., magnesium (Mg), commercial substrates such as low carbon steel, spring steel, and their pretreatments. The factors that play an important role in electroplating on an industrial scale, along with future challenges, are discussed.

Optimization of Nazarov Cyclization of 2,4-Dimethyl-1,5-diphenylpenta-1,4-dien-3-one in Deep Eutectic Solvents by a Design of Experiments Approach

The unprecedented Nazarov cyclization of a model divinyl ketone using phosphonium-based Deep Eutectic Solvents as sustainable non-innocent reaction media is described. A two-level full factorial Design of Experiments was conducted for elucidating the effect of the components of the eutectic mixture and optimizing the reaction conditions in terms of temperature, time, and substrate concentration. In the presence of the Deep Eutectic Solvent (DES) triphenylmethylphosphonium bromide/ethylene glycol, it was possible to convert more than 80% of the 2,4-dimethyl-1,5-diphenylpenta-1,4-dien-3-one, with a specific conversion, into the cyclopentenone Nazarov derivative of 62% (16 h, 60 °C). For the reactions conducted in the DES triphenylmethylphosphonium bromide/acetic acid, quantitative conversions were obtained with percentages of the Nazarov product above 95% even at 25 °C. Surface Responding Analysis of the optimized data furnished a useful tool to determine the best operating conditions leading to quantitative conversion of the starting material, with complete suppression of undesired side-reactions, high yields and selectivity. After optimization, it was possible to convert more than 90% of the model substrate into the desired cyclopentenone with cis percentages up to 77%. Experimental validation of the implemented model confirmed the robustness and the suitability of the procedure, leading to possible further extension to this specific combination of experimental designs to other substrates or even to other synthetic processes of industrial interest.

Electrodeposition of lanthanides from ionic liquids and deep eutectic solvents

Lanthanides belong to the most important raw materials and are highly demanded in high-tech industry. Low-temperature electrochemical deposition of lanthanides and lanthanide-based alloys for recycling and obtaining functional materials can provide a real alternative to the currently used high-temperature electrolysis of molten salts. The review summarizes the advancements in the field of electrodeposition of lanthanides from organic ionic systems, such as ionic liquids and deep eutectic solvents. The growing interest in these ionic systems is due to their excellent physicochemical properties, in particular non-volatility, thermal and electrochemical stability. The review also discusses further prospects and potential of the electrochemical approach for obtaining lanthanide-containing advanced materials.

The bibliography includes 219 references.

Integrated Leaching and Separation of Metals Using Mixtures of Organic Acids and Ionic Liquids

In this work, the aqueous phase diagram for the mixture of the hydrophilic tributyltetradecyl phosphonium ([P44414]Cl) ionic liquid with acetic acid (CH3COOH) is determined, and the temperature dependency of the biphasic region established. Molecular dynamic simulations of the [P44414]Cl + CH3COOH + H2O system indicate that the occurrence of a closed "type 0" biphasic regime is due to a "washing-out" phenomenon upon addition of water, resulting in solvophobic segregation of the [P44414]Cl. The solubility of various metal oxides in the anhydrous [P44414]Cl + CH3COOH system was determined, with the system presenting a good selectivity for CoO. Integration of the separation step was demonstrated through the addition of water, yielding a biphasic regime. Finally, the [P44414]Cl + CH3COOH system was applied to the treatment of real waste, NiMH battery black mass, being shown that it allows an efficient separation of Co(II) from Ni(II), Fe(III) and the lanthanides in a single leaching and separation step.

Indirect (hydrogen-driven) electrodeposition of porous silver onto a palladium membrane

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.

Progress in Electrodeposition of Zinc and Zinc Nickel Alloys Using Ionic Liquids

Zinc (Zn) and zinc–nickel (Zn–Ni) electrodeposition has been widely used in many industries, such as automotive and aerospace, for corrosion protection of steel components owing to their excellent corrosion resistance. Conventional zinc and zinc–nickel electrodeposition is performed in different types of aqueous baths (acid and alkaline). Such electrolytes suffer from certain drawbacks such as hydrogen gas evolution, low coulombic efficiencies, and environmental toxicity. Electrodeposition of Zn and Zn–Ni alloys from ionic liquids has gained significant attention in aerospace and automotive sectors owing to the different environments they provide for electrodeposition. This paper reviews the progress in deposition of zinc and zinc-nickel alloys in non-aqueous systems, especially ionic liquids. In addition, the challenges and technological developments associated with the Zn and Zn–Ni deposition on different substrates and the factors that need to be considered while electroplating at an industrial scale are discussed.

Effect of Hydrogen Bonding between Ions of Like Charge on the Boundary Layer Friction of Hydroxy-Functionalized Ionic Liquids

Atomic force microscopy has been used to measure the lubricity of a series of ionic liquids (ILs) at mica surfaces in the boundary friction regime. A previously unreported cation bilayer structure is detected at the IL-mica interface due to the formation of H-bonds between the hydroxy-functionalized cations [(c-c) H-bonds], which enhances the ordering of the ions in the boundary layer and improves the lubrication. The strength of the cation bilayer structure is controlled by altering the strength of (c-c) H-bonding via changes in the hydroxyalkyl chain length, the cation charge polarizability, and the coordination strength of the anions. This reveals a new means of controlling IL boundary nanostructure via H-bonding between ions of the same charge, which can impact diverse applications, including surface catalysis, particle stability, electrochemistry, etc.

Electrodeposition of nickel in air- and water-stable 1-butyl-3-methylimidazolium dibutylphosphate ionic liquid

Nickel coating was obtained by potentiostatic electrodeposition in 1-butyl-3-methylimidazolium diethylphosphate ionic liquid without any additive. Further, cyclic voltammetry (CV) tests were used to investigate the electrochemical behaviour of Ni²⁺ in the ionic liquid, revealing that the electrodeposition of nickel in this ionic liquid is an irreversible process. It was revealed that the diffusion of Ni²⁺ is a rate-determining step in the electrodeposition process. Further, the influence of dissolved water and applied voltage on electrodeposition were also studied using scanning electron microscopy (SEM).

Electrodeposition of (hydro)oxides for an oxygen evolution electrode

Electrochemical water splitting is a promising technology for hydrogen production and sustainable energy conversion, but the electrolyzers that are currently available do not have anodic electrodes that are robust enough and highly active for the oxygen evolution reaction (OER). Electrodeposition provides a feasible route for preparing freestanding OER electrodes with high active site utilization, fast mass transport and a simple fabrication process, which is highly attractive from both academic and commercial points of view. This minireview focuses on the recent electrodeposition strategies for metal (hydro)oxide design and water oxidation applications. First, the intrinsic advantages of electrodeposition in comparison with traditional technologies are introduced. Then, the unique properties and underlying principles of electrodeposited metal (hydro)oxides in the OER are unveiled. In parallel, illustrative examples of the latest advances in materials structural design, controllable synthesis, and mechanism understanding through the electrochemical synthesis of (hydro)oxides are presented. Finally, the latest representative OER mechanism and electrodeposition routes for OER catalysts are briefly overviewed. Such observations provide new insights into freestanding (hydro)oxides electrodes prepared via electrodeposition, which show significant practical application potential in water splitting devices. We hope that this review will provide inspiration for researchers and stimulate the development of water splitting technology.

Band-Gap Energies of Choline Chloride and Triphenylmethylphosphoniumbromide-Based Systems

UV-VIS spectroscopy analysis of six mixtures containing choline chloride or triphenylmethylphosphonium bromide as the hydrogen bond acceptor (HBA) and different hydrogen bond donors (HBDs, nickel sulphate, imidazole, d-glucose, ethylene glycol, and glycerol) allowed to determine the indirect and direct band-gap energies through the Tauc plot method. Band-gap energies were compared to those relative to known choline chloride-containing deep band-gap systems. The measurements reported here confirmed the tendency of alcohols or Lewis acids to increment band-gap energy when employed as HBDs. Indirect band-gap energy of 3.74 eV was obtained in the case of the triphenylmethylphosphonium bromide/ethylene glycol system, which represents the smallest transition energy ever reported to date for such kind of systems.

Influence of Hydrogen Bonding between Ions of Like Charge on the Ionic Liquid Interfacial Structure at a Mica Surface

Ionic liquids (ILs) have attracted increasing interest in science and technology because of their remarkable properties, which can be tuned via varying ion structures to control the relative strengths of Coulomb interactions, hydrogen bonding (H-bonding), and dispersion forces. Here we use atomic force microscopy to probe the interfacial nanostructures of hydroxy functionalized ILs at negatively charged mica surfaces. H-bonding between hydroxy functionalized cations (c-c) produces cation clusters and a stronger interfacial nanostructure. H-bond stabilized cation clusters form despite opposing electrostatic repulsions between charge groups, cation-anion (c-a) electrostatic attractions, and (c-a) H-bonds. Comparison of ILs with and without OH functionalized cations shows directional H-bonding enhances interfacial structure more strongly than the dispersion forces between alkyl groups. These findings reveal a new means of controlling IL interfacial nanostructure via H-bonding between like-charged ions, which impact diverse areas including electrochemical charge storage (batteries and catalysis), electrodeposition, lubrication, etc.

Potential Dependence of Surfactant Adsorption at the Graphite Electrode/Deep Eutectic Solvent Interface

Atomic force microscopy and cyclic voltammetry are used to probe how ionic surfactant adsorbed layer structure affects redox processes at deep eutectic solvent (DES)/graphite interfaces. Unlike its behavior in water, sodium dodecyl sulfate (SDS) in DESs only adsorbs as a complete layer of hemicylindrical hemimicelles far above its critical micelle concentration (CMC). Near the CMC it forms a tail-to-tail monolayer at open-circuit potential (OCP) and positive potentials, and it desorbs at negative potentials. In contrast, cetyltrimethylammonium bromide (CTAB) adsorbs as hemimicelles at low concentrations and remains adsorbed at both positive and negative potentials. The SDS horizontal monolayer has little overall effect on redox processes at the graphite interface, but hemimicelles form an effective and stable barrier. The stronger solvophobic interactions between the C₁₆ versus C₁₂ alkyl chains in the DES allow CTAB to self-assemble into a robust coating at low concentrations and illustrate how the structure of the DES/electrode interface and electrochemical response can be engineered by controlling surfactant structure.

Robust Aluminum Electrodeposition from Iionic Liquid Electrolytes Containing Light Aromatic Naphta as Additive

Aluminum electrodeposition can be carried out from several ionic liquid electrolyte formulations. Nevertheless, this plating process has not been industrialized so far because of the durability of the electrolytes and because the Al coatings obtained are non-fully homogeneous in terms of coating morphology and thickness distribution. In this work we electrodeposited Al coatings from a 3-butyl-1-ethylimidazolium tetrachloroaluminate electrolyte additivated with increasing concentrations of a new cost-effective additive: light aromatic naphtha solvent. Firstly, electrolytes were characterized by cyclic voltammetry, where changes in the electrochemistry of the process were identified. Then, surface characterization showed that Al coatings morphology turned out to be smoother, more homogeneous and more compact with increasing additive concentration. Furthermore, the process was scaled up to flat plates of 18 cm² area and also on 25 cm² parts designed with straight corners to demonstrate both the optimization of the electrolytic bath performance and its throwing power enhancement.

Facile synthesis of hierarchically nanostructured bismuth vanadate: An efficient photocatalyst for degradation and detection of hexavalent chromium

Heterostructured nanomaterials can paid more significant attention in environmental safety for the detection and degradation/removal of hazardous toxic chemicals over a decay. Here, we report the preparation of hierarchically nanostructured shuriken like bismuth vanadate (BiVO₄) as a bifunctional catalyst for photocatalytic degradation and electrochemical detection of highly toxic hexavalent chromium (Cr(VI)) using the green deep eutectic solvent reline, which allows morphology control in one of the less energy-intensive routes. The SEM results showed a good dispersion of BiVO₄ catalyst and the HR-TEM revealed an average particle size of ca. 5-10 nm. As a result, the BiVO₄ exhibited good photocatalytic activity under UV-light about 95% reduction of Cr(VI) to Cr(III) was observed in 160 min. The recyclability of BiVO₄ catalyst exhibited an appreciable reusability and stability of the catalyst towards the photocatalytic reduction of Cr(VI). Also, the BiVO₄-modified screen printed carbon electrode (BiVO₄/SPCE) displayed an excellent electrochemical performance towards the electrochemical detection of Cr(VI). Besides, the BiVO₄/SPCE demonstrated tremendous electrocatalytic activity, lower linear range (0.01-264.5 μM), detection limit (0.0035 μM) and good storage stability towards the detection of Cr(VI). Importantly, the BiVO₄ modified electrode was also found to be a good recovery in water samples for practical applications.

Nanostructure of the deep eutectic solvent/platinum electrode interface as a function of potential and water content

The interfacial nanostructure of the three most widely-studied Deep Eutectic Solvents (DESs), choline chloride:urea (ChCl:Urea), choline chloride:ethylene glycol (ChCl:EG), and choline chloride:glycerol (ChCl:Gly) at a Pt(111) electrode has been studied as a function of applied potential and water content up to 50 wt%. Contact mode atomic force microscope (AFM) force-distance curves reveal that for all three DESs, addition of water increases the interfacial nanostructure up to ∼40 wt%, after which it decreases. This differs starkly from ionic liquids, where addition of small amounts of water rapidly decreases the interfacial nanostructure. For the pure DESs, only one interfacial layer is measured at OCP at 0.5 nm, which increases to 3 to 6 layers extending ∼5 nm from the surface at 40 or 50 wt% water. Application of a potential of ±0.25 V to the Pt electrode for the pure DESs increases the number of near surface layers to 3. However, when water is present the applied potential attenuates the steps in the force curve, which are replaced by a short-range exponential decay. This change was most pronounced for ChCl:EG with 30 wt% or 50 wt% water, so this system was probed using cyclic voltammetry, which confirms the interfacial nanostructure is akin to a salt solution.

Solvation Properties of Silver and Copper Ions in a Room Temperature Ionic Liquid: A First-Principles Study

Understanding the behavior of metal ions in room temperature ionic liquids (ILs) is essential for predicting and optimizing performance for technologies like metal electrodeposition; however, many mechanistic details remain enigmatic, including the solvation properties of the ions in ILs and how they are governed by the intrinsic interaction between the ions and the liquid species. Here, we utilize first-principles molecular dynamics simulations to unravel and compare the key structural properties of Ag⁺ and Cu⁺ ions in a common room temperature IL, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate. We find that, when compared to Cu⁺, the larger Ag⁺ shows a more disordered and flexible solvation structure with a more frequent exchange of the IL species between its solvation shells. In addition, our simulations reveal an interesting analog in the solvation behavior of the ions in the IL and aqueous environments, particularly in the effect of the ion electronic structures on their solvation properties. This work provides fundamental understanding of the intrinsic properties of the metal ions in the IL, while offering mechanistic understanding and strategy for future selection of ILs for metal electrodeposition processes.