Low Vapor Pressure Research Articles

Supramolecular Ionic Gels for Stretchable Electronics and Future Directions.

Ionic gels (IGs), ionic liquids (ILs) dispersed in polymers, exhibit extremely low vapor pressure, electrochemical and thermal stability, and excellent mechanical characteristics; therefore, they are used for fabricating stretchable sensors, electrochemical transistors, and energy storage devices. Although such characteristics are promising for flexible and stretchable electronics, the mechanical stress-induced ruptured covalent bonds forming polymer networks cannot recover owing to the irreversible interaction between the bonds. Physical cross-linking via noncovalent bonds enables the interaction of polymers and ILs to form supramolecular IGs (SIGs), which exhibit favorable characteristics for wearable devices that conventional IGs with noncovalent bonds cannot achieve. Herein, we review recent material designs and interactions used for fabricating SIGs, such as ionic interactions and hydrogen bonding. We present SIG characteristics achieved via the interaction of polymers and ILs, such as extreme toughness, self-healing capability, and self-adhesion favorable for human body sensors. We conclude this Perspective by discussing the potential of SIGs as a power source for implants, wearable devices, and environmental sensing applications.

Recovery of iron as hematite and separation of trivalent lanthanide ions from spent hard disk magnet leach liquor using [P66614][Cy272] ionic liquid.

The widespread use of neodymium-iron-boron (NdFeB) magnets has raised concerns about the environmental impact of their disposal, prompting the need for sustainable recycling strategies. Traditional solvents used in recycling are toxic and flammable, making them risky to use. Ionic liquids are safer and greener options with low vapor pressure, high stability, and less flammability. This study introduces an eco-friendly recycling approach utilizing the [P66614][Cy272] ionic liquid to selectively extract iron and recover rare earth elements (REEs) from the leach liquor of waste NdFeB magnets. Pre-treatment processes enhanced metal concentration before leaching, including demagnetization, grinding, and screening. Optimal leaching conditions: 2 mol L-1 HCl, 80 °C, 10 g L-1 pulp density, and 90 minutes, resulted in complete leaching of REEs (Dy, Pr, Nd), iron, and boron. Using 0.01 mol L-1 [P66614][Cy272] ionic liquid, 100% of the iron was removed from the leach liquor with minimal co-extraction of REEs (∼4%). Precipitation of iron leading to Fe2O3 (hematite) after calcination and is verified through XRD and SEM-EDS analyses. The ionic liquid also enabled 81.1% recovery of HCl from the leach liquor, reducing neutralization needs and operational costs. Subsequent REEs separation using 0.01 mol L-1 [P66614][Cy272] ionic liquid demonstrated high selectivity, achieving separation factors of 18.55 (Dy/Pr) and 15.52 (Dy/Nd) at pH 2.03. Dy(iii) was successfully separated from NdFeB leach solutions using counter-current extraction, leaving 6.0 mg L-1 in the raffinate, requiring two extraction stages at a 2 : 3 organic-to-aqueous phase (O/A) ratio. The reusability of the ionic liquid further enabled a sustainable, closed-loop recycling process. This approach highlights the potential for integrating ionic liquids into green technologies for NdFeB magnet recycling, ensuring resource recovery while minimizing environmental impact.

An improved endwall-injection technique for examining high-temperature ignition of lubricating oils in shock tubes.

Ignition of the lubricating fluid in a mechanical system is a highly undesirable and unsafe condition that can arise from the elevated temperatures and pressures to which the lubricant is subjected. It is therefore important to understand the fundamental chemistry behind its ignition to predict and prevent this condition. Lubricating oils, particularly those with a mineral oil base, are very complex mixtures of thousands of hydrocarbons. Additionally, these oils have very low vapor pressures and high viscosities. These physical characteristics present considerable barriers to examining and understanding lubricant ignition chemistry. Therefore, a novel experimental design was devised to create and introduce a lubricant aerosol into a shock-tube facility in a reliable yet relatively simple manner. In this way, the lubricant can be quasi-homogeneously introduced into the shock tube where it will be vaporized by the incident shock wave, and combustion can be observed behind the reflected shock wave. To characterize the technique and anchor it with previously established methods, n-hexadecane was chosen to be tested both with the endwall injection and the well-established, heated shock tube techniques. This comparison showed good agreement, proving the ability of the simple technique to produce reliable ignition delay time (IDT) results. From here, Jet-A was also tested with the current injection technique and compared to a previous generation of the technique to highlight the advantages of the present method. Then, IDT results for mineral oil were collected to establish a baseline IDT set to which off-the-shelf lubricants and additional mixtures can be compared. Finally, IDTs for the off-the-shelf, mineral-based lubricant Mobil DTE 732 were obtained and compared to the baseline as well as the n-hexadecane results. All experiments were conducted near atmospheric pressure and for temperatures between 1084 and 1530K. An analysis of the system estimated the effective stoichiometry to be around ϕ = 1.15. Although no kinetics mechanisms exist for lubrication oils, preliminary model predictions made by modern chemical kinetics mechanisms for an alkane with 16 carbon atoms were then compared to the results to elucidate some of the chemistry this new method will allow the community to probe. This paper establishes the new method as a viable way to study and compare the ignition behavior of lubricating oils and other very low-vapor-pressure fuels in a shock tube.

Recent Advancement in the Development of Detection and Removal of Heavy Metal Ions by Deep Eutectic Solvents: A Review

: Heavy metal pollution is one of the most serious environmental problems, because of the non-degradable nature of heavy metals and their accumulation in the food chain, which poses a severe threat to the environment and human health even at low concentrations. Most of these metal ions can coordinate with biological molecules and disturb their function. Exposure to heavy metals can cause different health threats such as endothelial dysfunction, allergy, infant mortality, cancer, neurological diseases, respiratory diseases, oxidative stress, cardiovascular disorders and kidney diseases. Therefore the detection and removal of these toxic species are very important. Deep eutectic solvents (DESs) are green solvents and have excellent applications in many fields. They contain nonsymmetrical ions that have low lattice energy, low vapor pressure, dipolar nature, nonflammability, low volatility, low melting points, excellent thermal and chemical stability and high solubility. DESs are also better in terms of the availability of raw materials, easy synthetic procedure, low cost of their starting materials and their easy storage. DESs have an excellent ability for the detection and removal of heavy metal ions. In this review, we discussed various DES-based spectrophotometric and fluorimetric chemosensors for the detection of heavy metal ions in different matrixes. Additionally, we have also explored the capabilities of different DESs in removing heavy metals.

Removal of phenol from water using fenchol-menthol hydrophobic deep eutectic solvent

Hydrophobic deep eutectic solvents (HDESs) are regarded as a potential green alternative to conventional organic solvents in separation processes such as liquid-liquid extraction, due to their favourable properties, such as lower vapour pressure and tunable properties. The present work investigated the application of HDES which is synthesised from fenchol and menthol, in the removal of phenol from water. The HDES was synthesised experimentally at a fenchol mole fraction range of 0.1 to 0.9. The experimental results showed that stable liquidus HDES was successfully formed when the fenchol mole fraction in the HDES was 0.2 – 0.9. Further investigation showed that HDES with a fenchol mole fraction of 0.2, which had a low viscosity and high stability in water, had the highest phenol removal efficiency. The phenol removal process was highly sensitive to solution pH and solution-to-HDES ratio. In contrast, phenol removal was less affected by initial concentration and temperature. A high phenol removal efficiency of up to 95.9% was achieved in this study, which further showed the positive feasibility of HDES to serve as an alternative to conventional organic solvents in the liquid-liquid extraction of phenol from water.

Preparation and Characterization of Novel Core-Shell Microcapsules Containing C6F12O for Initial Fire Suppression

As an environmentally friendly and efficient fire extinguishing agent, C6F12O (CFO) is widely used for various types of fires. However, due to its low vaporization temperature and high vapor pressure, it is difficult to store and utilize. In order to reduce the loss and improve fire suppression efficiency of CFO, the complex coacervation method was employed to encapsulate CFO using a polymer material shell composed of gelatin (GE) and arabic gum (GA). The experimental results demonstrated that the preparation parameters had a significant impact on the microcapsule encapsulation efficiency. When the coacervation temperature was set to 40°C, the coacervation pH value was maintained at 3.8, the shell material concentration was adjusted to 8%, and the core-shell mass ratio was kept at 4:1, the microcapsule encapsulation efficiency reached its peak at 26.4%. CFO was successfully encapsulated as confirmed by characterization techniques such as TG, FT-IR, SEM, and 19F-NMR. CFO was released by breaking through the shell when the microcapsules reached the thermal response temperature. Additionally, the fire suppression tests showed that the microcapsules exhibited highly efficient fire extinguishing performance. They decreased the maximum temperature of the n-heptane flame by 196.7°C, lowered the temperature rate by 4.07°C/s, and shortened the self-extinguishing time by 47s. These results provide a new and effective solution for the microencapsulation of heat-sensitive materials and early-stage fire suppression.

The elusive nature of Martian liquid brines

The possible presence of brines on Mars adds an intriguing dimension to the exploration of Martian environments. Their potential involvement in the formation of recurring slope lineae has sparked debates on the existence of liquid water versus alternative dry processes. In situ instrumentation on rovers and landers has been instrumental in providing valuable data for comprehending the dynamics of brines. Laboratory experiments and thermodynamic simulations conducted under Martian conditions offer insights into the formation and persistence of brines, shedding light on the planet’s current hydrological processes. Despite these findings, the prevailing surface conditions on Mars, characterized by a combination of low temperature, pressure, and water vapor pressure, generally hinder the stability of most brines. In such environments, only a few select salts, notably calcium perchlorate, could play a pivotal role in potentially forming brines through deliquescence or melting. These environmental factors emerge as critical contributors influencing the stability of brines, but such limitations generally restrict the locations, timescales, and amounts of brine formed. However, the exploration of brines extends beyond geochemical considerations, serving as a lens through which we can examine potential habitability and gain a broader understanding of the Martian climate. Therefore, observing brines on Mars would offer valuable insights into the dynamic interplay of various factors that influence their stability, contributing to our overall comprehension of Mars’ unique environmental conditions.

Responses of field-grown maize to different soil types, water regimes, and contrasting vapor pressure deficit

Abstract. Drought is a serious constraint on crop growth and production of important staple crops such as maize. Improved understanding of the responses of crops to drought can be incorporated into cropping system models to support crop breeding, varietal selection, and management decisions for minimizing negative impacts. We investigate the impacts of different soil types (stony and silty) and water regimes (irrigated and rainfed) on hydraulic linkages between soil and plant, as well as root : shoot growth characteristics. Our analysis is based on a comprehensive dataset measured along the soil–plant–atmosphere pathway at field scale in two growing seasons (2017 and 2018) with contrasting climatic conditions (low and high vapor pressure deficit). Roots were observed mostly in the topsoil (10–20 cm) of the stony soil, while more roots were found in the subsoil (60–80 cm) of the silty soil. The difference in root length was pronounced at silking and harvest between the soil types. Total root length was 2.5–6 times higher in the silty soil than in the stony soil with the same water treatment. At silking time, the ratios of root length to shoot biomass in the rainfed plot of the silty soil (F2P2) were 3 times higher than those in the irrigated silty soil (F2P3), while the ratio was similar for two water treatments in the stony soil. With the same water treatment, the ratios of root length to shoot biomass of silty soil were higher than for stony soil. The seasonally observed minimum leaf water potential (ψleaf) varied from around −1.5 MPa in the rainfed plot in 2017 to around −2.5 MPa in the same plot of the stony soil in 2018. In the rainfed plot, the minimum ψleaf in the stony soil was lower than in the silty soil from −2 to −1.5 MPa in 2017, respectively, while these were from −2.5 to −2 MPa in 2018, respectively. Leaf water potential, water potential gradients from soil to plant roots, plant hydraulic conductance (Ksoil_plant), stomatal conductance, transpiration, and photosynthesis were considerably modulated by the soil water content and the conductivity of the rhizosphere. When the stony soil and silt soil are compared, the higher “stress” due to the lower water availability in the stony soil resulted in fewer roots with a higher root tissue conductance in the soil with more stress. When comparing the rainfed with the irrigated plot in the silty soil, the higher stress in the rainfed soil resulted in more roots with a lower root tissue conductance in the treatment with more stress. This illustrates that the “response” to stress can be completely opposite depending on conditions or treatments that lead to the differences in stress that are compared. To respond to water deficit, maize had higher water uptake rate per unit root length and higher root segment conductance in the stony soil than in the silty soil, while the crop reduced transpired water via reduced aboveground plant size. Future improvements in soil–crop models in simulating gas exchange and crop growth should further emphasize the role of soil textures on stomatal function, dynamic root growth, and plant hydraulic system together with aboveground leaf area adjustments.

Long-Range Surface Forces in Salt-in-Ionic Liquids.

Ionic liquids (ILs) are a promising class of electrolytes with a unique combination of properties, such as extremely low vapor pressures and nonflammability. Doping ILs with alkali metal salts creates an electrolyte that is of interest for battery technology. These salt-in-ionic liquids (SiILs) are a class of superconcentrated, strongly correlated, and asymmetric electrolytes. Notably, the transference numbers of the alkali metal cations have been found to be negative. Here, we investigate Na-based SiILs with a surface force apparatus, X-ray scattering, and atomic force microscopy. We find evidence of confinement-induced structural changes, giving rise to long-range interactions. Force curves also reveal an electrolyte structure consistent with our predictions from theory and simulations. The long-range steric interactions in SiILs reflect the high aspect ratio of compressible aggregates at the interfaces rather than the purely electrostatic origin predicted by the classical electrolyte theory. This conclusion is supported by the reported anomalous negative transference numbers, which can be explained within the same aggregation framework. The interfacial nanostructure should impact the formation of the solid electrolyte interphase in SiILs.

“Low-Hanging Fruit” Practices for Improving Water Productivity of Rainfed Potatoes Using Integration of Cultivar Selection, Mulch Application, and Different Agroecological Zones in Sub-Tropical, Semi-Arid Regions

Unevenly distributed rainfall leads to reduced potato water productivity (WP) under rainfed production conditions. Understanding the practices that can increase WP is vital. Our objectives were to understand (i) the seasonal variables that influence WP under rainfed conditions and (ii) the effect of the integration of cultivar x locality x mulch on potato WP. The study was undertaken in smallholder settings in two agroecological zones: Appelsbosch (Mbalenhle locality) and Swayimane (Stezi and Mbhava locality). A split plot, in a randomized complete block design experiment, included mulching (mulch and no mulch), four selected cultivars, and s three localities. Soil water content (SWC), yield, and climatic data were collected, and actual crop evapotranspiration (ETa) and WP were calculated. Rainfall, ETa, and crop growth and development had a significant influence on the seasonal WP. Cultivar × mulch × locality had an insignificant effect on the WP, however, locality × cultivar significantly altered the WP. The localities that had lower vapor pressure deficit (VPD), high relative humidity, and sandy soil had a higher potato WP for all cultivars, with the highest (18.38 kg m−3) being that from Electra. The findings suggest that using localities that have less atmospheric dryness and a cultivar (Electra) that shows stability of yield across the seasons can be an easy-to-apply practice for increasing potato WP in a resource-limited environment.

The Chemistry of Atmospheric Aerosols: At the Nexus Between Climate, Energy, and Air Quality

Atmospheric aerosols can be emitted directly as particles or formed in the atmosphere from phase transitions of gaseous compounds with low enough vapor pressure. During their lifecycle in the atmosphere, aerosols undergo multiphase changes, altering chemical composition, reactivity, physical and optical properties, ultimately influencing how they impact climate, human health and ecosystems. The understanding of the chemical processes in the atmosphere is crucial to assess these effects. Here we provide a brief overview on relevant aerosol chemical processes and measurement techniques with no claim to completeness and describe the Swiss contribution to the European infrastructure ACTRIS for long-term monitoring and its relevance for the research field.

Application of liquid metal driven-abrasive flow to material removal for the inner surface of channel

Gallium-based eutectic liquid metal alloys possess unique properties such as deformability, high electrical conductivity, and low vapor pressure. These characteristics have generated significant interest in their application for stretchable electronics and microelectromechanical systems (MEMS). Precise manipulation of liquid metal within electrolytes is essential to meet specific functional requirements. This study investigates the electrostatic manipulation of liquid metal in an alkaline solution with abrasives for material removal from the inner surfaces of flow channels. The polarization of the double layer at the gallium‑indium alloy and electrolyte interface is analyzed, elucidating the principle of electrolyte propulsion via continuous electrowetting. A theoretical model is developed, and two- and three-dimensional transient and steady-state simulations of the liquid metal-driven abrasive flow are conducted. Results demonstrate that this method effectively removes material from the inner walls of straight channels during cyclic motion. Utilizing continuous electrowetting, an experimental apparatus was designed, where gallium‑indium liquid metal propelled silicon carbide abrasives against PMMA channel walls. Experimental results showed effective material removal, consistent with finite element simulations, confirming the feasibility of this innovative approach.

Reactive Capture of CO2 via Amino Acid

The electrochemical production of carbon monoxide (CO) from carbon dioxide (CO2) has conventionally relied on gas-phase CO2 electrolysis with complex upstream capture and downstream gas separation processes. Reactive capture of CO2 – an integrated approach that combines CO2 capture and electrochemical conversion – uses chemisorbed CO2 directly as the feedstock and thereby avoids CO2 purification and associated costs.To date, reactive capture has relied on hydroxide-based capture solutions (e.g. potassium hydroxide (KOH)) suitable for direct air capture (DAC) processes or amines (e.g. monoethanolamine (MEA)) that have been conventionally used for point source capture. However, in hydroxide-based systems that capture CO2 in the form of carbonate, the CO Faradaic efficiency (FE) is limited to 50% due to the interaction between in-situ regenerated CO2 and local hydroxides that reduce CO2 availability at the cathode. Amine-based reactive capture can overcome this selectivity challenge when CO2 is captured in the form of carbamate and bicarbonate; compared to carbonate, these forms of chemisorbed CO2 require less electron-coupled protons to regenerate in-situ CO2, and thus yield more CO2 at the cathode. However, conventional amines are volatile and have poor oxygen tolerance, rendering them inapplicable to oxygen-rich CO2-lean conditions.Here, we report amino acid salt (AAS)-based reactive capture of CO2 that exceeds the CO energy efficiency (EE) achieved in amine- and hydroxide- based systems. The AAS capture solution, potassium glycinate (K-GLY), contains amino functional groups for efficient CO2 capture while offering advantages including oxygen tolerance, low vapor pressure, and low toxicity. We synthesized a nickel single atom (Ni-N/C) catalyst to improve conversion efficiency, optimized the capture solution composition to reduce the electrolysis overpotential at high current densities, and elevated the operating temperature and pressure to increase availability of dissolved in-situ CO2 at the cathode. We achieve CO production with 64% CO FE and a measured full cell voltage of 2.74 V at 50 mA cm-2, resulting in an CO EE of 31% and an energy intensity of 40 GJ tCO-1. The feasibility of the full reactive capture process was demonstrated with both simulated flue gas and direct air input.

Non-Destructive Pest Detection: Innovations and Challenges in Sensing Airborne Semiochemicals.

Pests, especially invasive ones, pose significant threats to the global ecosystem, crop security, and agriculture economy. Sensing airborne semiochemicals as a nondestructive detection method has been recognized as a promising strategy to detect the presence of these living pests on site. However, sensing airborne semiochemicals in fields is challenging, as they are transmitted in concentrations as low as several nanograms per cubic meter in chemically diverse environments. This low vapor pressure together with similarity in functional groups of pheromones among different species have curtailed the practical deployment of corresponding sensors for real world applications. This review describes the advances in semiochemical detection methods and technologies including traditional analytical instruments, trained animals, and electroantennography with a focus on electronic noses (e-noses). Several key types of volatile organic compound (VOC) sensors used in e-noses are summarized, including their transduction methods, sensing materials, and sensing performance for semiochemical and simulants detection. Notably, it was found that many commercial VOC sensors failed to respond to airborne semiochemicals effectively, leading to a reduced efficiency of e-noses. Future work may focus on developing stable and robust sensing materials with higher sensitivity and selectivity to pheromones and understanding the feasibility of the deployment of the sensors under field conditions.

Dependence of Carboxylate Anions on Physicochemical Properties of Tributyloctylphosphonium-Based Ionic Liquids

Ionic liquids, i.e. organic molten salts composed of cations and anions with melting points below 100°C, have unique properties such as high ionic conductivity, high thermal stability, low vapor pressure, low flammability, and so on. Among the numerous ionic liquids, considerable ionic liquids based on carboxylate anions have been reported1). On the other hand, several published papers reported ionic liquids based on quaternary phosphonium cations, demonstrating relatively high transport properties and thermal stability2,3). Our research group has preliminarily attempted to design and synthesize several carboxylate-based ionic liquids based on quaternary phosphonium cations. This paper discusses the dependence of carboxylate anions on physicochemical properties of room-temperature ionic liquids based on tributyloctylphophonium (P4448) cation in combination with various carboxylate anions (Fig. 1).The precursor hydroxides were synthesized from the corresponding phosphonium bromides by using an anion exchange resin (Amberlite IRN78 OH). Carboxylate-based phosphonium salts were obtained by adding equimolar amounts of carboxylic acids (formic, acetic, propionic, butyric, octanoic and lactic acids) into the hydroxide solution. The products were isolated by evaporation and then were dried under high vacuum at 50°C. The physicochemical properties of carboxylate-based ionic liquids, e.g. melting point, density, viscosity, conductivity and thermal decomposition temperature, were measured under argon atmosphere.Table 1 shows the melting points, glass transition temperature, thermal decomposition temperature and physicochemical properties of the carboxylate-based phosphonium ionic liquids at 25°C. All P4448-based ionic liquids became viscous liquids at room temperature, showing considerably low-melting behavior. It is noted that the density of P4448-Lac was higher than P4448-EtCO2. This result seems likely to be attributed to hydrogen bonding of the hydroxyl group in the lactate anion. The viscosity was decreased with increasing the carbon numbers in the alkyl chains of lower carboxylate anions. Although the details of this relationship between measured viscosity and the carbon numbers of the alkyl chains in carboxylate anions still remain unclear at present, the charge distribution of the anions is thought to be one of the factors. The acetate-, propionate-, butyrate-, and octanoate-based ionic liquids showed thermal decomposition temperatures around 280°C; however, lactate-based ionic liquids exhibited relatively high thermal decomposition temperature above 310°C. This may be due to the delocalization of the charge distribution in the lactate anion, resulting in the high thermal stability.References1) M. T. Clough, et al, Phys. Chem. Chem. Phys., 15, 20480 (2013).2) K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007).3) K. Tsunashima, et al, Electrochemistry, 75, 734 (2007). Figure 1

(Invited) Ionic Liquids As Multifunctional Electrolytes for Sodium Secondary Batteries

To sustain the fast-growing energy demand, high-performance electrolytes and electrode materials are required for secondary batteries. Sodium secondary batteries have emerged as expedient lithium-ion battery alternatives due to the low costs and high abundance of sodium resources. Ionic liquids (ILs) with low vapor pressure and low flammability are fascinating electrolytes for sodium secondary batteries owing to their intrinsic high safety and thermal stability.[1,2] In this talk, multifunctionalities of ionic liquid electrolytes for sodium secondary batteries will be comprehensively presented, especially targeting the performance of a range of negative and positive electrode materials and dual electrolyte system combined with beta-alumina. Intermediate temperature operation is also possible with the aid of thermally stable ionic liquids. Advantages of operation at intermediate temperature will be also discussed based on the results of electrochemical analysis.

Effect of Electrolyte Composition on Positive Electrode Properties of Rechargeable Aluminum-Graphite Batteries

Introduction The use of fossil fuels and the resulting greenhouse gas emissions, particularly CO2, have caused significant environmental damage. Rechargeable batteries are attracting attention as a storage application for renewable energy, and the emergence of next-generation rechargeable batteries that exceed the energy density of lithium-ion batteries is eagerly awaited. Aluminum is a promising material for batteries due to its cost-effectiveness, chemical stability in air, safety, and ease of handling. The oxidation of Al is a 3-electron reaction, resulting in a high theoretical volumetric capacity of 8046 mAh cm-3. Therefore, rechargeable aluminum batteries (RABs), which use aluminum as the negative electrode, are considered one of next-generation rechargeable batteries.Graphite has attracted considerable attention as the positive electrode active material in RABs due to its low cost, high stability, excellent electrical conductivity, and high redox potential. As for electrolyte, room temperature ionic liquids (RTILs) such as 1-ethyl-3-methylimidazolium chloride (EMImCl) offer several advantages, including high ionic conductivity, low vapor pressure, non-flammability, a wide potential window. It is known that AlCl3, a Lewis acid, forms a stoichiometric complex, AlCl4 -, with Cl-, a Lewis base, and AlCl4 - forms the dinuclear complex, Al2Cl7 -, with excess Cl-. So, the mixing ratio of AlCl3 to EMImCl (AlCl3/EMImCl molar ratio) will have a significant effect on the composition of RTILs, and the reaction kinetics of the graphite positive electrode. In this study, we investigated the effect of AlCl3/EMImCl ratio on the positive electrode properties. Experimental A slurry was prepared by mixing graphite powder and polyvinylidene fluoride (PVDF) as a binder with N-methylpyrrolidone (NMP), followed by ultrasonication. An appropriate amount of prepared slurry was applied to a Mo foil and dried under vacuum conditions to prepare a graphite positive electrode. In a glove box, AlCl3 and EMImCl were mixed in different molar ratios and stirred until a light-yellow liquid was obtained. Polished aluminum foil was used as the negative electrode. Results and Discussion Figure 1 shows Raman spectra of ionic liquids with AlCl3/EMImCl ratios from 1.1 to 1.9. In each spectrum, peaks assigned to AlCl4 - and Al2Cl7 - in addition to EMIm+ were observed. As the AlCl3/EMImCl ratio increased, the intensity of the AlCl4 - peak at 350 cm-1 decreased and that of the Al2Cl7 - peaks at 310 cm-1 and 430 cm-1 increased. The intensity of AlCl4 - and Al2Cl7 - linearly decreased and increased with an increase in the AlCl3/EMImCl ratio, respectively, indicating the reaction, AlCl4 - + AlCl3 → Al2Cl7 -, proceeds quantitatively.The cyclic voltammogram of the graphite electrode suggest that some couples of redox peaks of graphite were observed in a potential range between 0.5 V and 2.5 V. Each redox peak shifted negatively as the AlCl3/EMImCl ratio increased. Galvanostatic charge-discharge tests at 500 mA g-1 between 0.5 and 2.5 V were performed using Al/graphite cells containing electrolytes with different AlCl3/EMImCl ratios. In each AlCl3/EMImCl ratio, discharge curve with two plateaus was observed. The discharge capacity at the higher plateau voltage for the electrolyte with AlCl3/EMImCl = 1.1 was lower than that for the other electrolytes, while the discharge capacity at the lower plateau voltage was similar to each other. Irrespective of AlCl3/EMImCl ratio, discharge capacity hardly decreased over 100 charge-discharge cycles, while coulombic efficiency decreased with increasing the AlCl3/EMImCl ratio. This study compared the electrochemical properties of graphite in different molar ratios of electrolytes, which may help with future research and practical applications of RABs. Figure 1

Adsorption of Bipyridine at Single-Crystal Electrode | Ionic Liquid Interface – from Monolayers to Clusters

The self-assembly of organic molecules into ordered structures on the electrode’s surface offers various options for surface functionalisation. The formation of nanostructures also provides insights into the subtle interplay of various interactions between the electrode, organic adsorbate, and the electrolyte1. The detailed description of adsorption and self-assembly processes thus contributes to the development of molecular wires, junctions, and switches. Various studies have focused on the formation of a hybrid inorganic-organic interface in vacuum or aqueous electrolytes2–5. Using ionic liquids as electrolytes in nanotechnology can be beneficial due to their large variability, low vapour pressure, and good electrochemical stability. Meanwhile, their interfacial properties differ notably from other common solvents.The given presentation focuses on the adsorption and self-assembly of 4,4’-bipyridine at single-crystal electrode | ionic liquid interface. The use of density functional theory calculations alongside in situ scanning tunnelling microscopy and electrochemical impedance spectroscopy provides a multifaceted description of the 4,4’-bipyridine adsorption. The results show that, although the organic adlayer forms at studied Bi(111)6, Sb(111)7, and Cd(0001)8 electrode surfaces, the adlayer structure varies from highly organised monolayers to clusters. Furthermore, there are notable differences in 4,4’-bipyridine adsorption behaviour from previous aqueous electrolyte studies, highlighting the complex nature of the adsorption and organisation processes at electrode | ionic liquid interfaces9–11. Acknowledgements This work was supported by the Estonian Research Council grant PSG249, by the EU through the European Regional Development Fund under project TK141 (2014-2020.4.01.15-0011), by the Estonian Ministry of Education and Research (TK210), by the project “Increasing the knowledge intensity of Ida-Viru entrepreneurship” (ÕÜF12) co-funded by the European Union, and by the Graduate School of Functional materials and technologies receiving funding from the European Regional Development Fund in University of Tartu, Estonia. References 1K. Cui, I. Dorner and S. F. L. Mertens, Curr. Opin. Electrochem., 2018, 8, 156–163. 2S. Lemke, C.-H. Chang, U. Jung and O. M. Magnussen, Langmuir, 2015, 31, 3115–3124. 3A. Jeindl, J. Domke, L. Hörmann, F. Sojka, R. Forker, T. Fritz and O. T. Hofmann, ACS Nano, 2021, 15, 6723–6734. 4M. H. Hölzle, Th. Wandlowski and D. M. Kolb, Surf. Sci., 1995, 335, 281–290. 5T.-H. Vu and T. Wandlowski, J. Electron. Mater., 2017, 46, 3463–3471. 6H. Ers, L. Siinor and P. Pikma, Electrochim. Acta, 2024, 144081. 7H. Ers, L. Siinor, C. Siimenson, E. Lust and P. Pikma, Electrochim. Acta, 2022, 421, 140468. 8H. Ers, L. Siinor and P. Pikma, Electrochem. Commun., 2023, 148, 107451. 9P. Pikma, H. Kasuk, O. Oll, V. Ivaništšev, T. Romann, V. Grozovski, K. Lust and E. Lust, Electrochim. Acta, 2015, 180, 965–976. 10V. Grozovski, V. Ivaništšev, H. Kasuk, T. Romann and E. Lust, Electrochim. Acta, 2014, 120, 86–95. 11G. Gorbatovski, O. Oll, H. Kasuk, P. Pikma and E. Lust, Electrochem. commun, 2019, 105, 106500.

Solubility of Beryllium Metal in Molten 2LiF-BeF2

Fluoride salt-cooled High-temperature Reactors (FHRs) are a subtype of molten salt reactors (MSRs) in which a molten salt fills the role of a low pressure coolant to coated particle fuel. Another use for molten salt is in fusion reactors as a fusion blanket/coolant. The use of a molten salt as the coolant or blanket offers several safety advantages when compared to the current water-based designs due to the low vapor pressure of molten salts and their boiling point being far above the maximum coolant temperature. It also allows to integrate passive safety systems and to use a high-temperature power cycle. Careful control over the chemistry of the molten salt coolant must be kept in FHRs to reduce the corrosion of structural materials. The primary coolant candidate for FHRs is FLiBe (66.7%LiF-33.3%BeF2), which is not corrosive in its pure form, but impurities in the salt (commonly oxygen or water) and tritium fluoride generated from neutron irradiation of the salt can create an oxidizing environment.1 This in turn leads to structural corrosion, which degrades the system and and further modifies the properties of the salt. Because of this, redox control of the coolant salt is a key issue in FHRs.2 One of the methods for redox control is to introduce excess Be as a redox control agent to the salt, which reacts with tritium fluoride and decreases the redox potential. However, it has been found that when Be metal is contacted with FLiBe containing HF, it does not simply react with the HF, but is also dissolved in the salt. Another method is to add LiH to the FLiBe mixture as a hydrogen donor, which will induce the formation of dissolved metallic Be. This dissolution is not well understood, but could prove to be an elegant way for introducing a reducing agent to the system as the salt could be left in contact with Be metal in one part of the reactor to saturate the salt everywhere or be periodically saturated using LiH. The solubility of Be plays an important role here as it sets the limits for this saturation. Phases with visually different colours at different contents of Be in FLiBe have been reported in the literature, but no comprehensive analysis has been conducted to understand the solubility of metallic Be in FLiBe.3 In this study, we present data on these different phases of dissolved Be in FLiBe using LiH additions to understand the solubility of metallic Be. The crystal structure of different phases will be characterized using powder X-ray diffraction, the elemental composition via inductively coupled plasma mass spectrometry and melting points and latent heats via differential scanning calorimetry. Cyclic voltammetry will be used to determine activity coefficient of BeF2 in with different amounts of Be dissolved in it and electrical conductivities of different phases of the melt will be measured via electrochemical impedance spectroscopy. Additionally, neutron diffraction PDF data of Li2BeF4 with and without 1 mol% of metallic Be dissolved inside will be shown. A better understanding of the characteristics and speciation of dissolved Be in FLiBe will allow for closer redox control of the coolant melt and a longer lifetime for structural elements in FHR coolant loops. References (1) Vergari, L.; Scarlat, R. O.; Hayes, R. D.; Fratoni, M. The Corrosion Effects of Neutron Activation of 2LiF-BeF2 (FLiBe). Nuclear Materials and Energy 2023, 34, 101289. https://doi.org/10.1016/j.nme.2022.101289.(2) Zhang, J.; Forsberg, C. W.; Simpson, M. F.; Guo, S.; Lam, S. T.; Scarlat, R. O.; Carotti, F.; Chan, K. J.; Singh, P. M.; Doniger, W.; Sridharan, K.; Keiser, J. R. Redox Potential Control in Molten Salt Systems for Corrosion Mitigation. Corrosion Science 2018, 144, 44–53. https://doi.org/10.1016/j.corsci.2018.08.035.(3) Hara, M.; Hatano, Y.; Simpson, M. F.; Smolik, G. R.; Sharp, J. P.; Oya, Y.; Okuno, K.; Nishikawa, M.; Terai, T.; Tanaka, S.; Anderl, R. A.; Petti, D. A.; Sze, D.-K. Interactions between Molten Flibe and Metallic Be. Fusion Engineering and Design 2006, 81 (1), 561–566. https://doi.org/10.1016/j.fusengdes.2005.06.372.

(Invited) EIS Measurements in Ionic Liquids: Monitoring of the Electrodeposition of a Thin Metal Layer

Ionic liquids are increasingly used in a variety of applications, including electrolytes for electrochemical devices, solvents for the electroplating of thin metal layers, and corrosion inhibitors. Ionic liquids are a broad family of solvents whose physicochemical properties (viscosity, conductivity, etc.) depend on the nature of the anion and cation that form them. Some are protic with a labile proton, others are non-protic. Electrodeposition of metal in a protic ionic liquid such as ethylammonium nitrate (EAN) can be carried out at ambient temperature whereas higher temperatures are frequently performed in a non-protic ionic liquid. In addition, the electrodeposition of several elements is simple, yielding to an alloy whose composition and morphology are determined by the electroplating conditions. In this presentation, we will show how Electrochemical Impedance Spectroscopy (EIS) which is an efficient technique for characterizing the solid-liquid interface and investigating the electrodeposition mechanisms, can help for working in these media.In a first part, we will look at the electrodeposition of Nickel, Cobalt and their mixtures in EAN, a pure protic ionic liquid, and discuss EIS results. In a second part, we will take advantage of the low vapor pressure of ILs, and we will discuss how we can characterize a material reactivity by performing electrochemical measurements in a 3 - 5 µL drop of ionic liquid.