Room Temperature Ionic Liquids Research Articles

Fluorescence and Phosphorescence Dual-Emission Liquid Crystal Polymer Optical Waveguide for logical Gate.

Information security has emerged as a critical concern in contemporary society. Leveraging optical logic gates with dual-emission characteristics offers a promising approach to enhancing information security. However, designing active optical waveguide materials (OWMs) capable of fluorescence-phosphorescence dual emission remains a significant challenge. In this study, we present a room-temperature phosphorescent liquid crystalline polymer (RTP LCP) as active OWMs exhibiting fluorescence-phosphorescence dual emission and a low optical loss coefficient (OLC) for implementation in optical logic gates. The resulting RTP LCP exhibits a smectic phase between 25 °C and 90 °C, followed by nematic phase between 90 °C and 110 °C, with a phosphorescence lifetime of 2.77 ms. Subsequently, the RTP LCP is processed into oriented liquid crystal fibers and encapsulated in polymethyl methacrylate. Optical waveguide experiments demonstrate that these oriented liquid crystal fibers exhibit fluorescence-phosphorescence dual emission, with low OLCs of 0.20 dB/mm at 490 nm and 0.17 dB/mm at 565 nm. Furthermore, these dual-emission active OWMs are successfully applied to optical logic gates. This work holds significant implications for the development of active OWMs with fluorescence-phosphorescence dual emission, advancing their potential applications in optical logic gates.

Liquid metal ion source based on magnetic suspensions for field emission electric propulsion (FEEP)

This work presents a process for the creation of emitter structures for liquid metal ion sources based on suspensions of iron and nickel in gallium-based room temperature liquid metal alloys. The process does not require needle etching or vacuum wetting of the emitter. Tip radii of less than 3 μm have been achieved. In addition, first measurements and observations from single emitter emission experiments are presented, including current-voltage characteristics, vacuum stability, degradation mechanisms and first thruster characteristics for the use in field emission electric propulsion. The impedance of the magnetic liquid metal emitters was found to correlate with the mass fraction of particles suspended in the liquid metal. Total impedances up to 30 MΩ have been achieved, indicating the feasibility of emitter clustering. Thrust measurements were performed with a commercial of the shelf load cell and verified in a dedicated setup for field emission electric propulsion testing, featuring a sub micro newton counterbalanced double pendulum thrust balance.

Strengthened Effect of Surface-Active Ionic Liquids on Curcumin Solubility and Extraction Performance of Curcuminoids

As a kind of bioactive component in the rhizome of natural plant Curcuma longa L. (turmeric), curcumin is almost insoluble in water at neutral and acidic pH, which limits its further utilization and development. At the same time, traditional extraction and separation processes typically require the use of a large number of organic solvents. Ionic liquids (ILs) are organic molten salts with melting points below 100 °C. When an ionic liquid exists in a liquid state at or near room temperature, it is referred to as a room-temperature ionic liquid (RTIL). They have a temperature range, good physical and chemical stability, and good structural designability. They have a strong solubilization enhancement effect for many organic compounds. This study first explored the molecular forms of curcumin in ionic liquid aqueous solutions and the intermolecular interactions between curcumin and ionic liquids using spectral analysis and computational chemistry methods; furthermore, using an ionic liquid aqueous solution as an extraction agent, curcumin-like substances (curcuminoids) were extracted from turmeric powders under ultrasound assisted conditions, revealing the relationship between the structure of the ionic liquid and the extraction efficiency. After that, a kinetic study was conducted for the extraction of curcuminoids from turmeric powders, using second-order kinetics fitting to obtain the rate constant and initial extraction rate during the extraction process. Finally, the comparison with a ComplexGAPI tool and antioxidant experiment was performed on the extraction by using ionic liquids and traditional solvent. The full results can provide reference for the design of IL extractants and their application for natural products.

Cavity correlations and the onset of charge ordering at charged interfaces: A modified Poisson-Fermi approach.

Charge layering in the close vicinity of charged interfaces is a well-known effect, extensively reported in both experiments and simulations of Room Temperature Ionic Liquids (RTILs) and concentrated electrolytes. The traditional Poisson-Fermi (PF) theory is able to successfully describe overcrowding effects but fails to reproduce charge ordering even in strong coupling regimes. Simple models, yet capable of investigating the interplay between these important interfacial phenomena, are still lacking. In order to bridge this gap, we herein present a modified PF approach that is able to capture layering effects in strong coupling regimes typical of RTIL. The modification is based on the introduction of charge cavities around test-particles, which simply extend the exclusion volume effects to also incorporate the accompanying depletion of charges due to particle insertion. The addition of this simple ingredient is shown to reproduce overscreening and charge ordering, thereby extending the predictive power of the PF approach to strong coupling regimes. Using a linear response theory, we were able to study the emergence of charge ordering based on two characteristic lengths: a wavelength responsible for charge layering, along with a damping length that screens charge oscillations. At large ionic strengths and strong couplings, the system undergoes a transition to undamped charge layering. The transition takes place when the poles of the Fourier components of the linear potential become real-valued. This criterion allows one to identify the transition line across the parameter space, thus delimiting the region of stability against unscreened charge ordering.

Phosphorescent Liquid Crystalline Polymer-based Circularly Polarized Luminescence Optical Waveguides for Enhanced Photonic Signal Processing and Information Encryption.

Efficient circularly polarized luminescence (CPL) optical waveguides have significant potential for advancing photonic and optoelectronic devices. However, the development of CPL optical waveguides materials (OWMs) with low optical loss coefficient remains a considerable challenge. To overcome this, we design and synthesize CPL OWMs based on room-temperature phosphorescent liquid crystalline polymers (LCPs). Experimental results demonstrate that these LCPs exhibit a nematic liquid crystal phase and a phosphorescence lifetime of approximately 0.145 ms. By introducing a chiral dopant, we induce a chiral arrangement in the LCPs, followed by crosslinking via photo-cycloaddition and removal of the chiral dopants through solvent soaking. The resulting polymers exhibit stable solvent resistance and highly efficient circularly polarized phosphorescence (CPP) properties, with dissymmetric factors (gRTP) in the range of 0.16 to 0.17. Notably, the CPP-active OWMs exhibit efficient circularly polarized photonic signal waveguiding, with an optical loss coefficient of approximately 0.175 dB/mm. Ultimately, these CPP-active OWMs are sucessfully applied in information encryption, decryption, and optical switching, paving the way for advanced photonic and optoelectronic devices.

Structure factor line shape model gives approximate nanoscale size of polar aggregates in pyrrolidinium-based ionic liquids.

Room temperature ionic liquids (RTILs) are interesting due to their myriad uses in fields such as catalysis and electrochemistry. Their properties are intimately related to their structures, yet structural understanding is difficult to achieve. This work presents a derivation of an approximate expression for the radial distribution function, g(r). The derivation assumes a Lorentzian line shape for total structure factors, S(Q). The derived form for g(r) is used to present new equations for maxima and minima in g(r) and to define a half-length, the value of r where g(r) decays to one-half its maximum value. A detailed test of the model is presented using experimentally measured and calculated S(Q) for N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (C1C3pyrrTFSI). Then, the model is extended to the series of RTILs with anions of increasing size, C1C3pyrrX (X- = Cl-, Br-, BF4-, PF6-, OTf-, TFSI-). The model predicts maxima and minima in the entire series within 4.2% of those calculated directly from molecular dynamics simulations. This reinforces our previous conclusion that distances within "polar scattering domains" responsible for the charge alternation peak in S(Q) are quantitatively related to inter-ionic distances within polar aggregates in these RTILs. The half-length is found to increase approximately linearly as anion size increases. We argue that the half-length is a measure of polar aggregate size in these RTILs.

Single Particle Dynamics at the Free Surface of Imidazolium-Based Ionic Liquids.

In this work, we carry out a systematic computer simulation investigation of the single particle dynamics at the free surface of imidazolium-based room temperature ionic liquids by applying intrinsic surface analysis. Besides assessing the effect of the potential model and temperature, we focus in particular on the effect of changing the anion type, and, hence, their shape and size. Further, we also address the role of the length of the cation alkyl chains, known to protrude into the vapor phase, on the surface dynamics of the ions. We observe that the surface dynamics of ionic liquids, being dominated by strong electrostatic interactions, is about 2 orders of magnitude slower than that for common molecular liquids. Furthermore, the free energy driving force for exposing apolar chains to the vapor phase "pins" the cations at the surface layer for much longer than anions, allowing them to perform noticeable lateral diffusion at the liquid surface during their stay there. On the other hand, anions, accumulated in the second layer beneath the liquid surface, stay considerably longer here than in the surface layer. The ratio of the mean surface residence time of the cations and anions depends on the relative size of the two ions: larger size asymmetry typically corresponds to larger values of this ratio. We also find, in a clear contrast with the bulk liquid phase behavior, that anions typically diffuse faster at the liquid surface than cations. Finally, our results show that the surface dynamics of the ions is largely determined by the apolar layer of the cation alkyl chains at the liquid surface, as in the absence of such a layer, cations and anions are found to behave similarly with respect to their single particle dynamics.

Reversed rectification of ionic liquid/water mixtures in conical nanochannels

Because of their remarkable properties, room-temperature ionic liquids (RTILs) are used widely in electrochemistry, fuel cells, supercapacitors, and even DNA sequencing, and many of these applications involve the transport of RTILs in nanoscale media. Particularly for single-molecule detection, the RTIL must be mixed with a solvent (e.g., water) so that the electrolyte has both high viscosity and conductivity to obtain excellent signals. If a RTIL contains a quantity of water in bulk, this has a significant effect on its properties (e.g., the electrochemical window), thereby limiting some applications. However, the physicochemical properties of RTILs containing water in nanoconfined spaces remain unclear, especially their ionic transport behavior. Therefore, reported here is a study of the ionic transport behavior of mixed RTIL/water solutions at the nanoscale using a single conical nanochannel as a nanofluidic platform. The conductivity of the mixtures in the nanoconfined space was closely related to the nanochannel size, and highly diluted mixed solutions resulted in a nonlinear rectification-reversed current, which was possibly due to the adsorption of cations on the nanochannel wall. The maximum rectification ratio was 114, showing excellent rectification that could be used to realize newly conceptualized nanofluidic diodes. In summary, this work provides an exhaustive understanding of the nonlinear ion transport of RTIL/water mixtures and a theoretical foundation for applying RTILs in energy storage and conversion and bio-sensing.

New room temperature ionic liquids, 1-butyl-3-methylimidazolium o-anisate and 1-butyl-3-methylimidazolium m-anisate as novel sensitizers for Eu3+ fluorescence

Fluorescence enhancement of Eu3+ was achieved using new room temperature ionic liquids, 1-butyl-3-methylimidazolium o-anisate ([Bumim][oA]) and 1-butyl-3-methylimidazium m-anisate ([Bumim][mA]) which was tailored for the purpose. Analytical methodology was developed for the trace level detection of Eu3+ in ionic liquid systems and the best detection limit of Eu3+ was in the order of 10-10 M. In addition, the fluorescence lifetime of Eu3+ in ionic liquid system has increased to about 1000 μs, which is due to the non quenching environment of Eu3+ in ionic liquid relative to aqueous. This is the first study to use new task-specific ionic liquids (TSILs) with anisate as anions for the trace level detection of Eu3+.This paper has also discussed the detailed synthesis and characterization methods adopted for new room temperature ionic liquids.

Enhancing Amperometric Ozone Gas Sensing with Room-Temperature Ionic Liquids and Platinum-Based Electrodes.

Ozone (O3) poses serious health risks, prompting numerous countries to implement regulations that establish exposure limits and emission controls, for example, the air quality index (AQI) for O3 ranging from 50 to 150 parts per billion (ppb), with natural levels at around 30 ppb. Electrochemical sensors are favored for detecting pollutant gases due to their high sensitivity, low cost, portability, energy efficiency, and capability for selective detection. In this study, we developed an O3 sensor employing carbon-supported Pt-based binary and ternary nanorods (NRs) combined with room-temperature ionic liquids (RTILs) as electrolytes, aiming at highly sensitive and selective detection of O3 at ppb levels. Initial screening of the O3 sensing performance across different electrolytes identified H2SO4 and [C4mpyrr][NTf2] (BMP) as the most sensitive options. BMP outperformed H2SO4 in terms of linearity, selectivity, reproducibility, and response/recovery times, despite a relatively lower sensitivity. Electrochemical testing of Pt, PtAu, PtAg, and PtAuAg NR electrodes in BMP revealed that the addition of Au enhanced the linear response, while Ag improved sensitivity. Consequently, the ternary PtAuAg NR electrode exhibited the highest sensitivity (10.5 nA/ppm (parts per million)) and a broad detection range, fulfilling the AQI requirements for O3. The current response from the PtAuAg NR electrode closely aligned with results from an ultraviolet (UV) photometric analyzer, confirming its accuracy. Notably, this electrode contains only 20 wt % noble metals, which reduces the overall cost to just 11% of that of a traditional pure Au electrode.

Jordan Hobbs.

"I would have liked to have discovered one of the early room temperature liquid crystal mixtures. Probably a good bit of money in those patents!… My science 'hero' is Alan Turing. For everything he accomplished whilst also being an LGBTQ+ icon…" Find out more about Jordan Hobbs in their Introducing… Profile.

Molecular Design and Alignment for Ambipolar SCLC Mobility in Self-Assembled Columnar Discogens.

The future of next-generation electronics relies on low-cost organic semiconductors that are tailored to simultaneously provide all requisite optoelectronic properties, focusing greatly on ambipolar charge-transport and solution processability. In this regard, room-temperature discotic liquid crystals (DLCs) are potential candidates, where quasi-1D self-assembly affords a charge-transport channel along their columnar axis. This work shows a molecular design strategy by utilizing anthraquinone as the primary motif, surrounded by ester functionalized tri-alkoxy phenyl units to develop room-temperature DLCs (1.1-1.3). Here, the polar ester functionality stabilizes the columnar mesophase over a wide range through the involvement of dipole-dipole interaction along with the π-π stacking. Throughout the entire mesophase transition, reported compounds 1.1-1.3 exhibit a highly ordered 2D columnar oblique (Colob) self-assembly. Space charge limited current (SCLC) experiments reveal balanced ambipolar charge transport, with the maximum hole and electron mobilities of 5.04 and 4.93 cm2 V-1 s-1, respectively. From the conoscopic results, their propensity to align in a highly homeotropic fashion is demonstrated. It is further justified by the azimuthal plot corresponding to the (11) peak of grazing incidence small angle X-ray scattering (GISAXS), denoting the crucial role of the design and alignment for efficient movement of charge carriers in the material.

Physicochemical and Thermal Behaviors of Room-Temperature Phosphonium Ionic Liquids Based on Fluorosulfonyl(trifluoromethylsulfonyl)Amide Anion As Potential Electrolytes

Room-temperature ionic liquids (RTILs), i.e. organic molten salts with melting points below 100 ◦C, have been intensively developed for electrolytic media in various electrochemical systems due to the fact that RTILs have unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Another advantage of RTILs is a purposive selection of the ion species and their designability. Although typical anion species employed for RTILs include sulfonylamide-based anions, e.g. bis(trifluoromethylsulfonyl)amide (N(SO2CF3)2 -, TFSA) and bis(fluorosulfonyl)amide (N(SO2F)2 -, FSA) anions, asymmetric fluorosulfonyl(trifluoromethylsulfonyl)amide (N(SO2F)(SO2CF3)-, FTA) anion have attracted attention in recent years. In our preliminary approach, FTA anion based RTILs in combination with quaternary phosphonium cationswe previously reported,1,2 examining their transport property behavior. In this work, we report design and synthesis of several FTA-based phosphonium RTILs (Fig. 1) as potential electrolytes available for electrochemical systems, summarizing their physicochemical and thermal characteristics including the thermal decomposition as well as the transport property behaviors.The preparation and purification of the phosphonium RTILs were carried out according to the procedures described in our previously published papers.1-3 The phosphonium RTILs were prepared by aqueous ion exchange reactions of the precursor phosphonium bromides with lithium FTA. The resulting crude RTILs was extracted by dichloromethane, and then purified by washing with pure water several times until no residual bromide anion was detected with the use of AgNO3. The RTILs was dried under high vacuum for at least 1 day at 80 ◦C prior to use. The physicochemical and electrochemical properties such as conductivity (ac impedance method, using a two-Pt electrode cell), viscosity (cone-plate type viscometer), density, melting point (DSC), thermal decomposition temperature (TGA) were measured under dry argon atmosphere.Several phosphonium RTILs melting at ambient temperatures were successfully prepared by combination with the FTA anion. Table 1 lists the physicochemical properties and thermal decomposition temperatures (10% weight loss) of the FTA-based phosphonium RTILs. All FTA-based phosphonium RTILs showed typical temperature-dependent behaviors for density, viscosity and electrical conductivity. It should be noted that P222(1O1)-FTA exhibited the lowest viscosity and the highest conductivity in the FTA-based phosphonium RTILs, which is attributed to the introducing effect of ether oxygen atom into the cation on the flexibility of the alkyl chain. On the other hand, the thermal decomposition temperatures of the FTA-based phosphonium RTILs tended to be relatively low (less than 300 ◦C) compared to those of TFSA-based RTILs. The detailed thermal decomposition behavior observed in the thermogravimetric traces will be discussed in comparison with both corresponding TFSA- and FSA-based RTILs.References1) K. Tsunashima, et al, Electrochem. Commun., 9, 2353 (2007).2) K. Tsunashima, et al, Electrochemistry, 75, 734 (2007).3) K. Tsunashima, et al, Electrochem. Commun., 13, 178 (2011). Figure 1

Machine-Learning Assisted Analysis on the Transport Behavior of Zn2+ in Room-Temperature Ionic Liquid Electrolytes

Imidazolium-based room-temperature ionic liquids (RTILs) show promise as electrolytes for zinc-air batteries due to their chemical stability and high ionic conductivity. While experimental performance data for various RTILs exist, the atomistic mechanisms underlying ion transport phenomena remain understudied, primarily due to computational costs and force field development challenges. This study presents a machine learning interatomic potential (MLIP) for imidazolium-based RTILs with four anion species: BF4, PF6, bis(trifluoromethanesulfonyl)imide (TFSI), and trifluoromethanesulfonate (TfO). We fine-tuned the pretrained MACE-MP-0 model using a dataset of 100 distinct configurations sampled from molecular dynamics (MD) trajectories of randomly generated RTIL mixtures. The MD simulations for data generation were performed using MACE-MP-0 potential to accelerate configurational sampling. The resulting MLIP demonstrates excellent generalization to out-of-domain data and accurately predicts RTIL densities. Using the trained MLIP, we performed 300 ps NVT MD simulations for each anion type. Radial distribution function analysis reveals that the primary solvation shell of Zn2+ consists of RTIL anions, which implies Zn2+-anion correlations in Zn2+ ion transport. Further investigation suggests a linear relationship between logarithmic ionic conductivity and Zn2+-cation binding energy, providing insights into the underlying transport mechanisms in these RTIL electrolytes.

Asymmetrical Supercapacitor Based on Iodide Ion Containing Ionic Liquid Mixture

The increased global energy demand and environmental pollution require energy generated from renewable energy sources such as wind, solar, etc. As the adoption of these energy resources increases, developing different energy storage systems becomes important. The applicability of room-temperature ionic liquids (RTILs) as electrolytes for supercapacitors (SCs) and batteries has been discussed in many papers. RTILs have lower conductivity and higher viscosity; thus, they have narrower low-temperature operation limits compared to aqueous and non-aqueous electrolytes. However, compared with volatile aqueous and organic electrolytes, RTILs are much safer in SCs applications. To improve the power and energy densities of SCs, various mixtures of ionic liquids have been investigated, including systems of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) with bromide ion addition on carbon cloth1, EMImBF4 with iodide ion addition on Bi(111) electrode2 and D-glucose derived activated carbon (GDAC)3. However, in studies1,3 the capacitance and ideal polarizability of positively and negatively charged carbon cloth and GDAC electrodes were not taken into account, limiting the overall energy storage capability, efficiency, and cycle life of these systems. Therefore, characterization of these materials-based SCs in three- and two-electrode configurations are inevitable to overcome these mentioned shortcomings4. In the present research EMImBF4 with addition of 5 wt% 1-ethyl-3-methylimidazolium iodide (EMImI) was selected to study the influence of iodide anions addition on the electrochemical performance of micro- and mesoporous carbon material-based SC system4. Based on electrochemical data established by cyclic voltammetry, electrochemical impedance spectroscopy, constant current charge/discharge, and constant power discharge methods, the asymmetrical SC with ionic liquid mixture compared to the symmetrical SC with neat EMImBF4 demonstrated increase in cell capacitance about 5 F g-1 (33 F g-1 vs 27 F g-1 in cell potential range of 2.4 V) and specific energy about 3.5 W h kg-1 (28.1 W h kg-1 vs 24.4 W h kg-1 in cell potential range of 2.4 V). However, the ideal polarizability region, i.e., electrochemical stability of the iodide ion containing ionic liquid mixture-based SC is somewhat lower as well as specific adsorption and partial charge transfer is not fully reversible leading to the lower coulombic and energy efficiency values4. Acknowledgments: This research was supported by the EU through the European Regional Development Fund under project TK141, "Advanced materials and high-technology devices for energy recuperation systems" (2014–2020.4.01.15–0011) and TK210, “Estonian Centre of Excellence in Green Hydrogen and Sustainable Energetics”, Institutional Research grant IUT20–13, European Spallation Source: Estonian Partition in ESS Instrument design, development and building and application for science research project SLOKT12026T and by Estonian Research Council grants PUT1033, PUT55, and PRG676.

Paired Electrosynthetic Oxidations Using Multifunctional Ionic Liquids

The study of electrochemical oxidations has wide-ranging implications, from the development of new electrocatalysts for fuel cells for energy conversion, to the synthesis of fine chemicals. 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) has been used for decades as a sustainable, metal-free mediator for chemical and electrochemical oxidations. We describe here a novel approach to TEMPO-mediated electrooxidations, in which the chemical input and waste generated during electrooxidations of alcohols are minimized by using a paired flow electrosynthesis in a multi-functional solvent. Our three-pronged approach involves the following: (1) the use of a recyclable alkylimidazolium-based, room temperature ionic liquid (RTIL) to replace the electrolytes and volatile organic solvents typically used in TEMPO-mediated alcohol electrooxidations; (2) generation of required base at the counter electrode through reduction of the cationic component of the recyclable RTIL; (3) incorporation of the catalytic TEMPO moiety in our RTIL-based system. We demonstrate the possibilities offered by our strategy using a range of alcohol and allylic oxidations, illustrating the scope of reaction that can be driven using our strategy, and demonstrating the opportunities offered by RTILs to the development of task-specific, multi-functional electrolytes for electroorganic synthesis.

(Invited) Preparation of Aucu Alloy Nanoparticles Via Ionic Liquid/Metal Sputtering for Electrocatalytic CO2 Reduction

Development of highly active electrocatalysts for carbon dioxide reduction has been intensively investigated for the efficient utilization of CO2 and the lowering of electric energy consumption. Among various strategies, alloy nanoparticles (NPs) have attracted significant interest due to their tunable catalytic properties, which can be adjusted by altering their chemical composition and particle size. Recently, we reported novel preparation methods of metal nanoparticles through the sputter deposition of metals onto room-temperature ionic liquids (RTILs), a technique we termed “RTIL/metal sputtering technique”. This method enabled the formation of metal and alloy NPs, such as Au, Ag, Pd, Pt, AuAg, AuCu, AuPt and AuRh,(1-6) with sizes in the nanometer ranges, in the absence of additional stabilizing agents. Here we report the preparation of AuCu alloy NPs via RTIL/metal sputtering and evaluate their electrocatalytic activity for CO2 reduction as a function of the alloy composition.The simultaneous sputtering of Au and Cu onto RTILs produced AuCu alloy NPs with the size ranging from 3 to 4 nm. Subsequent loading of these sputter-deposited AuCu NPs in RTIL on carbon black powders (CB) not only increased the AuCu NP size to 3-7 nm but also facilitated alloying between Au and Cu. The chemical composition of AuCu NPs was controlled by changing the area fraction of Au plates in Au-Cu binary targets used for sputtering. The XRD analysis revealed that thus-obtained AuCu NPs had the fcc structure, in which each peak shifted to a lower angle with an increase in the Au fraction.The prepared AuCu/CB powers were immobilized on glassy carbon electrodes and used for the electrocatalyst for CO2 reduction in a 0.5 M KHCO3 aqueous solution. Cyclic voltammetry revealed that cathodic currents were observed at potentials more negative than -1.2 V, with the current intensity being higher under a CO2 atmosphere compared to an N2 atmosphere. This confirms the CO2 reduction activity of AuCu nanoparticles. Constant potential electrolysis was carried out at -2 V vs. Ag/AgCl in a CO2 atmosphere. As CO2 reduction products, CO and HCOOH were formed. The selectivity of these products was remarkably influenced by the composition of AuCu alloy NPs: The HCOOH selectivity increased with a higher Cu ratio, while the CO selectivity showed a volcano-type relationship, reaching an optimum at the Au fraction in NPs of ca. 0.8. H2 was also produced as a byproduct, with its selectivity being minimized at the Au fraction of 0.6-0.9. In conclusion we demonstrated the importance of alloy composition in optimizing the electrocatalytic performance of AuCu NPs for CO2 reduction. References T. Torimoto, et al., Appl. Phys. Lett. 89, 243117 (2006) .K. Okazaki, et al, Chem. Commun. 691-693 (2008) .M. Hirano, et al., Chem. Chem. Phys. 15, 7286-7294 (2013).S. Suzuki, et al., 44, 4186-4194, (2015).S. Suzuki, et al., CrystEngComm, 14, 4922-4926 (2012)K. Akiyoshi, et. al, Phys. Chem. Chem. Phys., 24, 24335 (2022) .

Deep Eutectic Solvents As Novel Solvent-Electrolyte System for Electroreductive Transformations

Organic electrosynthesis is regarded as a sustainable alternative to traditional organic synthesis as it enables replacement of stochiometric redox agents with electricity – which can be generated from renewable sources – and high product selectivity at ambient conditions [1]. However, the poor conductivity of the organic solvents typically requires the addition of large amounts of supporting electrolyte salts, leading to increased waste generation and lowered atom economy of the process.Alternative solvents such as room temperature ionic liquids (RTILs) and deep eutectic solvents (DESs) represent a promising alternative electrolyte and solvent in electrosynthesis. They are conducting, non-volatile and able to solubilize several organic compounds as well as easily separated from products by extraction and thus prone for reuse [2-4]. In addition, they have a tunable, large electrochemical window and this has already led to their use as electrolytes in other fields of electrochemistry, including batteries, electrochromic devices, supercapacitors and in electrodeposition processes [5-6].DESs offer some advantages compared to RTILs, including that their synthesis is comparable inexpensive and simple, requiring no purification. In addition, some of the DES are biodegradable. DESs have already been use in organic synthesis as solvents and catalysts, however only few examples use DESs as electrolyte systems in organic electrosynthesis despite their advantageous properties. DESs can also solubilize untreated biomass and biomass components, and thus they are attractive solvents for several biorefinery processes including pretreatment, fractionation, and catalytic conversion [7]. Selective reductive transformations are key in biomass valorization to yield precursors for fuels and chemicals.In this work, we show how DESs can play a dual role as solvent and electrolyte for reductive transformations of organic compounds. The physical and electrochemical properties of the DESs and their role in the reaction are investigated. In addition, the feasibility of reusing the DES over several reactions is examined.[1] Frontana-Uribe, B.A.; Little, R. D.; Ibanez, J. G.; Palma, A. & Vasquez-Medrano, R. Green Chem. 2010, 12, 2099-2119.[2] Singh, S. K. & Savoy, A. W. J. Mol. Liquids 2020, 297, 1120938[3] Hansen, B. B.; Spittle, S.; Chen, B.; Poe, D.; Zhang; Y., Klein; J. M.; Horton, A.; Adhikari, L.; Zelovich, T.; Doherty, B. W.; Gurkan, B.; Maginn, E. J.; Ragauskas, A.; Dadmun, M.; Zawodzinski, T. A.; Baker, G. A.; Tuckerman, M. E.; Savinell, R. F. & Sangoro, J. R. Chem. Rev. 2021, 121, 1232–1285.[4] Kathiresan, M., & Velayutham, D. Chem. Commun. 2015, 51, 17499.[5] Armand, M.; Endres, F.; MacFarlane, D. R.; Ohno, H. & Scrosati, B. Nat. Mater. 2009, 8, 621–629.[6] Abbott, A. P. Curr. Opin. Green Sustain. Chem. 2022, 36, 100649.[7] Wang, Y.; Kim, K. H.; Jeong, K.; Kim, N. K.; Yoo, C. G. Curr. Opin. Green Sustain. Chem. 2021, 27, 100396.

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

Use of Pulsed Potentials for Electropolishing TA6V Parts Elaborated By Additive Manufacturing in Deep Eutectic Solvent

It is now possible to achieve complex geometries by additive manufacturing of various metals and alloys, without compromising their core mechanical and structural properties. Nevertheless, their degraded surface state remains a critical issue which constitutes a key obstacle for its broad deployment. SLM parts are characterized by their high roughness (Ra up to 40 µm), a strong texture (directly related to the manufacturing process and parameters) and to the presence of potentially detachable unmelted particles. For almost all applications, relevant finishing post-treatments must be carried-out on the surface, to improve its behavior against fatigue, ageing, corrosion and abrasion. Due to oxygen contamination of the surface, titanium and titanium alloys have the ability to form an oxide layer at its surface, called alpha case. In addition to a high hardness which makes the part difficult to machine, this layer alters the mechanical properties (such as loss of ductility, degradation of static and fatigue strength) and corrosion resistance. The degradation of the properties caused by the formation of this layer forces manufacturers to carry out additional operations such as chemical attack, machining, sandblasting, ...etc. Removal of alpha case by chemical polishing is often done with fluorine ions, which creates soluble complex with titanium leading to mass loss, with the drawbacks linked to this kind of processes.Electropolishing then becomes an interesting alternative, especially if it is carried out in an electrolyte presenting a low health hazard such as Deep Eutectic Solvent (DES). This kind of solvent, used for the first time by Abbott et al [1], are more tolerant to water and less expensive than Room Temperature Ionic Liquids. Pure metallic titanium plates were also successfully electropolished in a DES mixture made of choline chloride-propylene glycol, improving the brightness of the sample and a reduction of the roughness from a few hundreds of nanometers to about 40 nm [2]. The problem is however very different considering additively manufactured parts which show very high roughness (going up to several dozen µm), which leads to the risk of deformation of the geometry of the parts due to very long processing times. In addition, the very high natural viscosity of the electrolyte, combined with the formation of a viscous layer on its surface, creates fluid movements. Indeed, when it reaches too much thickness, the viscous layer detaches itself to flow, which has the effect of creating inhomogeneities on the removal of matter and the reduction of roughness. To overcome this problem, the use of pulsed potentials cycles, at two frequencies, was evaluated. The first one based on short pulses, already experienced on stainless steel, aims to limit the geometric deformation during long processing time [3]. The second one, based on longer pulses allow to limit the growth of the viscous layer and prevent its flow. These sequences were designed through the study of transient curves, and were applied to test pieces on RDE electrodes, leading to bright and homogeneous titanium alloy samples. This process was implemented into a 65L tank, were different parts were successfully finished.[1] A.P. Abbott; G. Capper; K.J. McKenzie; A. Glidle; K.S. Ryder; “Electropolishing of stainless steels in a choline chloride based ionic liquid: an electrochemical study with surface characterisation using SEM and atomic force microscopy” Phys. Chem. Chem. Phys., 8 (2006), pp. 4214-4221[2] A. Kityk; V. Protsenko; F. Danilov; V. Pavlik; M. Hnatko; J. Šoltýs; “Enhancement of the surface characteristics of Ti-based biomedical alloy by electropolishing in environmentally friendly deep eutectic solvent (Ethaline); Colloids and Surfaces A: Physicochemical and Engineering Aspects, 613 - (2021), pp126125[3] M. L. Doche; J-Y Hihn; E. Drynski, F. Roy; A. Boucher; Jason Rolet; J. Tardelli; “Electropolishing of 316L stainless steel parts elaborated by selective laser melting: from laboratory to pilot scale,” Procedia CIRP, vol. 108, no. C, pp. 722–727, 2022