bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrocatalytic Hydrogen Atom Transfer for the Activation of Alkenes: Mechanism of Formation and Reactivity of Cobalt Hydride
Authors: Boucher Dylan G , Minteer Shelley D.
Published: November 2022

Metal hydride species have proven to be a crucial chemical motif across chemical disciplines. As the key intermediate in electrocatalytic hydrogen evolution by molecular catalysts, understanding how metal hydrides are formed and how they react has allowed the design of more efficient electrocatalysts. Independently to the field electrocatalysis, metal hydride species have been critical for organometallic catalysis as reagents for hydrogen atom transfer (HAT), in particular the activation of alkenes to a diverse array of hydrofunctionalization products. Recently, these two fields have been explicitly linked via the emergence of electrocatalytic hydrogen atom transfer (e-HAT); utilizing primarily Cobalt based catalysts (salen and bipyridine) members of the NSF Center for Synthetic Organic Electrochemistry (CSOE) have shown that in situ electro-generated cobalt hydride species can catalyze highly sought-after organic transformations of alkenes, such as alkene isomerizations and enantioselective hydrocyanation reactions. However, from an electrochemical perspective these reactions remain poorly understood, severely limiting the design of new hydrofunctionalization reactions. Here, cyclic voltametric studies of Co(salen) provide a sorely needed mechanistic framework to understand these multi-step electrocatalytic reactions. Using model homolytic reactions we establish rate constants for cobalt hydride formation as well as a relationship between hydride donor ability and alkene activation. Hammett analysis of a series of modified salen ligands shows changes in the rate determing step, suggesting tunability in future organic electrosynthetic reactions. Finally, we detect key off-cycle intermediates that inhibit catalytic turnover and suggest further optimization in yield and enantioselectivity selectivity are possible. In summary, we contend that these mechanistic studies provide an important template for studying complex, multistep organic reactions from the perspective of traditional molecular electrocatalysis as developed by Jean-Michel Savéant.
Electrosynthesis of Value-Added Chemicals Using Water As a Proton Source
Authors: Xia Rong , Jiao Feng
Published: November 2022

Electrifying chemical productions is a potential approach to decarbonizing the chemical industry. The electrochemical processes, when powered by renewable electricity, have lower carbon footprints than conventional thermochemical routes. Using water as the proton source avoids the energy-intensive dry-reforming process to produce H2 from fossil fuels, and electrochemical reaction using voltage as driving force instead of elevated pressure enables the reaction to happen at ambient temperature and pressure. Electrosynthesis of value-added ethylamine and ethylene glycol are used as two examples in this presentation. Herein, we report an electrocatalytic route to produce ethylamine selectively through an electroreduction of acetonitrile at ambient temperature and pressure. Among all the electrocatalysts, Cu nanoparticles exhibited the highest ethylamine Faradaic efficiency (FE, ~96%) at -0.29 V versus reversible hydrogen electrode (RHE). In a flow cell configuration, an ethylamine partial current density of 846 mA cm-2 was achieved using the Cu catalyst at -0.73 V vs. RHE in a 1 M NaOH electrolyte containing 12 wt.% acetonitrile. Under a constant current density operation at 100 mA cm-2, the Cu catalyst also showed a stable 20-hour performance in a continuous acetonitrile electroreduction with an 86% ethylamine FE. Moreover, the reaction mechanism of acetonitrile electroreduction was investigated by density functional theory calculations, in which the calculated free energy changes of the rate-limiting steps in acetonitrile reduction and hydrogen evolution reaction suggest a better ethylamine selectivity for Cu than other conventional hydrogenation catalysts (i.e., Ni and Pt).
Electrolyte Induced Solvent Cage Effects for Enantioselective Electrosynthesis
Authors: Nguyen Zachary A , Boucher Dylan , Minteer Shelley D.
Published: November 2022

Electrochemistry provides a tunable, regioselective, and green alternative to traditional synthetic organic methods, and access to reactive intermediates. Problematically, electrochemical redox events often go through planar radical intermediates, thus destroying enantioselectivity. As such, researchers have sought the “chiral electron”, a general methodology to impart enantioselectivity to electroorganic reactions. One strategy has been asymmetric transition metal catalysis while replacing the typical stochiometric redox reagent needed with electricity, thus providing a chiral pathway for elecoorganic reactions. However, the general physical parameters that govern enantioselectivity at electrochemical interfaces, remains poorly understood.

Here, we focus on the effects of supporting electrolyte in synthetic organic electrochemistry, specifically its role in enantioselective reactions. Cyclic voltammetry provides a tool to investigate the mechanistic consequences of changes in electrolyte. Using the model reaction of enantioselective carboxylation with a cobalt catalyst, we observe changes in mechanism as the electrolyte size is varied. Specifically, electrolyte identity effects the lifetime of the chiral Co-alkyl intermediate. These fundamental electroanalytical studies provide a sound mechanistic basis for the origin of enantioselectivity in electroorganic reactions. In summary, these results of a general interest as a strategy to tune and improve enantioselectivity in electrochemical transformations.
Peroxynitrite Reactivity with Capsaicin: A Potential for Capsaicin-Based Sensing Devices
Authors: Kalil Haitham , Crichlow Cynthia , Bayachou Mekki
Published: November 2022

Peroxynitrite and other reactive oxygen species (ROS) have been linked to illnesses caused by oxidative stress, such as atherosclerosis. Accurate detection of these species in biological systems is crucial not only for understanding the etiology and course of the disease but also for creating and evaluating viable therapies. In the last 30 years, there has been an exponential increase in research into capsaicin's biological relevance. Capsaicin has analgesic, antioxidant, anti-inflammatory, anti-cancer, and anti-obesity properties. Most of these investigations have focused on the analgesic, antioxidant, and anticancer properties of this chemical compound throughout the last three decades. Capsaicin has been shown to increase the production of peroxynitrite by boosting the formation of superoxide anions in combination with nitric oxide.

Preliminary UV-Vis results suggested a potential interaction at micromolar levels between capsaicin and peroxynitrite. A hyperchromic shift has been shown at a wavelength of ~ 300 nm, indicating an interaction between capsaicin and peroxynitrite, which resulted in a 2x increase in absorbance. The interaction of capsaicin and peroxynitrite was further studied using cyclic voltammetry and differential pulse voltammetry.
Unraveling the Pathways of Electrochemical Reduction of Furfural Via Tailoring Microenvironments
Authors: Liu Hengzhou , Patel Deep , Chen Yifu , Lee Jungkuk , Roling Luke T. , Li Wenzhen
Published: November 2022

Electrochemical reduction of biomass-derived feedstocks holds great promise to produce value-added chemicals or fuels driven by renewable electricity. However, mechanistic understanding of the aldehyde reduction toward valuable products at the molecular level within the interfacial regions is still lacking. Herein, through tailoring the local environments, including H/D composition and local H3O+ and H2O content, we studied the furfural reduction on Pb electrodes in acid conditions and elucidated the detailed pathways toward three key products: furfuryl alcohol (FA), 2-methylfuran (MF), and hydrofuroin. By combining isotopic labeling and electrokinetic studies, we revealed the source of protons (H2O and H3O+) plays a critical but different role in the hydrogenation and hydrogenolysis pathways toward FA and MF, respectively. In particular, the product-selective kinetic isotopic effect of H/D and the surface property-dependent hydrogenation/deuteration pathway strongly impacted the generation of FA but not MF. This is because FA and MF are produced from Langmuir-Hinshelwood and Eley-Rideal pathways, respectively. Through modifying the double layer by cations with large radii, we further correlated the product selectivity (FA and MF) qualitatively and quantitively with interfacial environments (local H3O+ and H2O content, interfacial electric field, and differential capacitances). Experimental and computational investigations further suggested competitive pathways toward hydrofuroin and FA: Hydrofuroin is favorably produced through the self-coupling of ketyl radicals in the electrolyte, which are formed from the outer-sphere single-electron transfers, while FA is generated from hydrogenation of the adsorbed furfural/ketyl radical on the electrode surface.
Influence of Post-Synthetic Annealing on Photo-Electrochemical Properties of CuGaO2 Mesoporous Thin Films Using Different Viscosity Ethyl Cellulose
Authors: Yeasmin Humaira , Bredar Alexandria R. C. , Farnum Byron H.
Published: November 2022

Delafossite CuGaO2 is a p-type metal oxides which can be used as hole transport layers in a wide range of heterojunction solar cells. These materials are interesting because of their crystal structure that can facilitate hole diffusion through the valance band and a potential alternative to NiO as an HTM because of its more favorable band position to typical redox mediator, and its greater transperancy to visible light. Here we have investigated the effect of post synthetic annealing conditions on electrochemical properties of CuGaO2 nanocrystalline thin films in acetonitrile solution with LiClO4 electrolyte and iodide triiodide redox mediator. These metal oxide nanocrystals have defects intrinsic to their structure and those can be increased or remediate by different annealing atmosphere. In this work, CuGaO2 was synthesized by hydrothermal method and nanocrystalline films were produced by dispersion of CuGaO2 nanocrystals in a polymer solution designed to control the porosity of the resulting film. We have used four different chain lengths of ethyl cellulose polymers (10, 22, 100 and 300 cP) to understand their impact on film morphology and photocurrent. Electrochemical impedance spectroscopy (EIS) was used to probe the electrochemical behavior and capacitance of the films. The films were prepared by spin coating and annealed initially under Ar environment at 3500C. We have used I-/I3
- redox mediator to observe the comparative photocurrent under white light LED. We have used two other different annealing atmospheres H2 and O2 after the pre-Argon annealing step to compare the photocurrent and observed the highest photocurrent by annealing under H2 gas. We assume, this is due to remediating some of the defect states under reducing atmosphere. We have compared two different synthetic pH for CuGaO2 (pH 5 and 9).We have measured the film thickness and using the data from dye load experiments, the porosity of the films were calculated to get the idea about the best quality film in terms of photocurrent . Among four different chain lengths of polymer, the films prepared from shorter chain polymers show comparatively higher photocurrent.
Design and Fabrication of Electrochemical Protein Sensors for a Fetal Membrane-on-a-Chip
Authors: Buckey Grace , Owens Olivia , Cliffel David E
Published: November 2022

Preterm birth (PTB) is the top cause of death in newborns and the second leading cause of death in children under the age of five. Certain cytokines, like interleukin-6 (IL-6), and matrix metalloproteinases (MMPs) are known to facilitate the degradation of the fetal membrane, but the mechanisms that result in fetal membrane rupture under both normal and pathological conditions are largely unknown. Our fetal membrane-on-a-chip model will allow us to investigate the conditions and mechanisms that precede fetal membrane rupture. Our enzymatic electrochemical detection platform allows us to detect biosignatures from the fetal membrane by measuring analyte concentration changes such as glucose utilization, lactate production, and oxygen consumption. Addition of electrochemical sensors for cytokine and MMPs to the detection platform will provide further insight into the mechanisms underlying PTB by offering low-level protein biomarker quantification.

We are currently fabricating and optimizing electrochemical immunoassays for the detection of IL-6 and MMP-3 to leverage the advantages of electrochemical techniques in studying preterm births. The current protein assay design utilizes the enzyme alkaline phosphatase attached to the target protein. When introducing the substrate p-aminophenyl phosphate (PAPP) to the system, it is enzymatically converted to p-aminophenol (PAP). Upon oxidation, PAP is converted to p-quinone (PQI). We are currently studying the electrochemical behavior of PAP/PQI for application in immunoassays. We are investigating the use of different electrochemical techniques for PAP oxidation to PQI including cyclic voltammetry, square wave voltammetry, differential pulse voltammetry, and normal pulse voltammetry to see how the technique affects the reproducibility of assay measurements.
Bipolar Hydrogen Production from Biomass-Derived Aldehydes and Water in Flow Electrolyzers
Authors: Liu Hengzhou , Li Wenzhen , Janik Michael John , Agrawal Naveen , Chen Yifu
Published: November 2022

It is critical to fight against global warming and confine it to a manageable level of +1.5°C by curbing CO2 emissions, eventually achieving zero net emissions by 2050. This target will involve significant efforts from all industry sectors and require renewable energy storage and conversion, most of which are heavily rely on clean hydrogen production. Water electrolysis, producing hydrogen and oxygen from water and electricity, is a promising route to the decarbonization of industry and transportation. The main source of energy loss in water electrolysis is the unfavorable thermodynamics (standard potential of 1.23 V vs. NHE) and slow kinetics of oxygen evolution reaction (OER). These challenges motivate us to design efficient paired electrolysis systems to substitute OER. In this work, we demonstrate an efficient bipolar hydrogen production system that combines cathodic hydrogen evolution from water and anodic hydrogen generation from aldehyde oxidation, at a low voltage (~0.1V) with co-generation of high valuable carboxylic acid. We used furfural as the model aldehyde, a biomass-derived compound that is produced on a large scale, currently on a scale of 0.43 million tons/year. Unlike conventional combined systems for hydrogen production that require high voltage (> 1.0 V) and are limited by mass transport (<100 mA cm−2) of reactants, this study doubled the hydrogen production rate, obtained industrial-level current density (e.g. 390 mA cm−2, 0.6V), and achieved economic viability ($2.51/kg of H2). These achievements benefit from a thermodynamically favorable hydrogen production pathway from aldehyde, facile kinetics on porous Cu-based catalysts, efficient mass transport in flow cells, and inexpensive size-exclusive separators. The successful implementation of such an energy-efficient process will impact future low-carbon hydrogen production and distributed chemical manufacturing.
Enhanced Performance of Microbial Fuel Cells Using PVDF Activated Carbon Air Cathode and Electrochemically and Chemically Treated Carbon Felt Anode
Authors: Poureshghi Oskouei Fatemeh , Dong Nga Phuong , Das Subhashis , Petrich Chris , Calay Rajnish Kaur
Published: November 2022

Microbial fuel cells (MFCs) harness the metabolism of microorganisms, converting chemical energy into electrical energy. Improving both Anode and Cathode design is thus of great significance to enhance the MFC performance and its commercial application. For the performance improvement of MFCs, the anode becomes a breakthrough point due to its influence on bacterial attachment and extracellular electron transfer (EET). On the other hand, air cathodes have considerable influence on the maximum power of air-driven MFCs. The cathodes used in MFCs need to have high catalytic activity for oxygen reduction, but they should be inexpensive watertight,and easy to manufacture.

As the first part of this work, carbon felt was electrochemically and chemically treated by electrolyzing in nitric acid and phosphate buffer followed by soaking in aqueous ammonia. The treated and untreated carbon felts were utilized as anodes in MFCs, and current production was compared while the cathode was stainless steel mesh (SS-316L) in both cases. The treated carbon felt displays strong interaction with the microbial biofilm of Shewanella baltica 20 facilitating electron transfer from exoelectrogens to the anode. An MFC equipped with a treated carbon felt as anode has significantly lower charge-transfer resistance and achieves considerably better performance than one equipped with an untreated carbon felt anode. The enhanced electron transfer is attributed to newly generated carboxyl containing functional groups on the treated carbon felt.

In the second part of the present study, SS-316L as a cathode was modified using phase inversion process to construct a poly vinylidenefluoride (PVDF) binder and an activated carbon catalyst according to the procedure reported previously.

Finally, the MFC with treated carbon felt anode and PVDF air cathode was tested. The MFC with both modified anode and cathode achieves considerably better performance than one with a traditional carbon felt anode and SS-316L cathode. The maximum current density, power density, and energy recovery, and sensitivity of the biofilm to the heavy metals are significantly improved.
Enhancing Electron Transfer in a Biomimetic Nanocomposite Electrode for Microbial Fuel Cell Applications
Authors: Deninger Ian D. , Sran Ashna K. , Keleher Jason J.
Published: November 2022

Microbial fuel cells (MFCs) have emerged as a renewable energy source due to their ability for direct conversion of organic substrates into electrical energy. However, issues with low power density, limited long-term stability, and higher operational costs have slowed larger scale integration and adoption. One main factor impacting fuel cell performance is the bacterial interactions at the electrode interface and the associated electron transfer mechanisms which are being widely studied. To increase productive interactions between the microbes and anode, this work focused on the synthetic design of a conductive polysaccharide-based (i.e., agar, alginate, pectin) nanocomposite material. More specifically, metal-carboxyl (Fe3+ or V5+)coordination chemistry was used to photoinitiate the polymerization of polyaniline (PANI) directly on the backbone of the biopolymer matrix increasing the overall uniformity. Results show that the n-doped conducting polymer nanocomposite has enhanced current flow when exposed to E. Coli. Additionally, the electrode surface was modified via non-covalent linkages of organic fuels, such as glucose, with TiO2 nanoparticles to decrease bacteria-surface repulsions. Initial results show that the sugar functionalized electrodes demonstrated an increased electric response in conjunction with photochemical activity. This phenomenon was observed through decreased fluorescence intensity without a decrease in cell viability as well as increased open circuit potential in the presence of light. This ligand-metal charge transfer coupled with increased conductivity of a biomimetic bulk material has resulted in an overall improved MFC system.
Exploring Sub-Detection Limit Electrochemistry with Luminogenic Reporting Reactions
Authors: Linfield Steven , Gawinkowski Sylwester , Nogala Wojciech
Published: November 2022

Electrochemistry has a limit of detection imposed by the inherent shot-noise present in electrical currents [1]. As a result, the direct measurement of single-electron charge transfer processes is not feasible using electrochemical methods. However, luminescence can be measured with single photon resolution and the development of a method to efficiently convert an electrochemical signal to an optical one is expected to be a key step in overcoming the detection limit of electrochemistry [2].

An optical conversion technique based on closed bipolar electrochemistry has recently been demonstrated using large glassy carbon electrodes [3,4]. In this technique, which is illustrated in Fig. 1, any electrochemical process of interest occurring in one cell (the detection cell) can be used to induce either fluorescence or chemiluminescence in another cell (the reporting cell). Fluorogenic reporting reactions have the advantage that several photons can be emitted during the lifetime of each fluorophore, leading to signals with a greater intensity. However, the facile photooxidation of some fluorophores introduces the need for chemical reductants, which complicates the electrochemistry [5]. Conversely, the constant electron-to-photon relationship of chemiluminescence makes it an easier process for calculating the number of electrons passed in the detection cell, but also leads to a reduced signal intensity [6]. There is still much work needed to understand which reporting mechanism is more suited to sub-detection limit electrochemistry and how to reach the maximum sensitivity of single-electron charge transfer processes.

In this work, we present our recent progress towards the measurement of sub-detection limit electrochemical processes via luminogenic reporting reactions. We compare the conversion mechanisms of reporting reactions which use either fluorescence or chemiluminescence, and we study the factors which can affect the sensitivity of the conversion, such as the presence of chemical reductants. Finally, we test the temporal resolution and sensitivity of optical conversion techniques in the measurement of single entity electrochemical processes. The results shown herein are of importance to electrochemists wishing to use optical conversion to probe below the detection limit of electrochemistry.

Literature

[1] R. Gao, M. A. Edwards, J. M. Harris and H. S. White, Curr. Opin. Electrochem., 2020, 22, 170–177.

[2] Y. Wu, S. Jamali, R. D. Tilley and J. J. Gooding, Faraday Discuss., 2022, 233, 10–32.

[3] J. P. Guerrette, S. J. Percival and B. Zhang, J. Am. Chem. Soc., 2013, 135, 855–861.

[4] J. S. Stefano, F. Conzuelo, J. Masa, R. A. A. Munoz and W. Schuhmann, J. Electroanal. Chem., 2020, 872, 113921.

[5] S. M. Oja, J. P. Guerrette, M. R. David and B. Zhang, Anal. Chem., 2014, 86, 6040–6048.

[6] P. A. Defnet and B. Zhang, ChemElectroChem, 2020, 7, 252–259.

Figure 1
Investigating Nafion Responsiveness Via Coupled Transport-Mechanical Network Modelling
Authors: Goyal Priyamvada , Kusoglu Ahmet , Weber Adam Z.
Published: November 2022

Perfluorosulfonated (PFSA) ionomer membranes owe their high conductivity and durability, which make them popular as proton-exchange membranes for fuel cells and electrolyzers, to their characteristic phase-separated morphology. The hydrophilic domains connecting the ionic moieties form the transport network for ions and water, while the hydrophobic polymeric backbone affords them the much-needed mechanical stability. Interactions between these domains constitute the structure-property relationship. PFSAs such as Nafion can be reimagined as responsive materials by leveraging this structure-property relationship, integral to their functionality, as a stimuli-response dynamic.

Modelling, in tandem with morphological, mechanical, and transport experimental evidence, can be a powerful tool to deconstruct how different stimuli can be designed to elicit a desired response from an ionomer. A large majority of relevant models have dealt with transport in and mechanics of Nafion membranes as isolated behaviors. Transport models, which are usually continuum scale, use dilute solution (Nernst–Planck) or concentrated solution (Onsager–Stefan–Maxwell) theory depending on the scale and complexity of the phenomena in focus. Mechanical models range from statistical-mechanics-led molecular scale formulations to macroscopic phenomenological approaches. Whereas the continuum models lose out on details regarding morphological changes, molecular models are simply too expensive to scale up. Mesoscale models can offer an elegant solution for this problem by incorporating phenomenon inseparable from structural details of the material while remaining computationally tenable.

In this work, the hydrophilic and hydrophobic domains in the ionomer will be modelled as two-way coupled mesoscale networks. Whereas the transport network will share characteristics with a pore-network-like configuration, the polymeric backbone will be visualized as a network of non-Hookean springs. The interspersed networks will be configured using the dual-cubic as well as the Delaunay–Voronoi conformations. The mathematical frameworks for each phase will also be modified to include mass-momentum coupling, as implemented by a few continuum models. The network nature of the topology will allow for local flux and deformation changes to organically propagate beyond the nearest neighbors, capturing the core of the ionomer’s responsiveness. Deeper insights into the stimuli-response behavior will allow for more nuanced control of operating conditions for fuel cells and electrolyzers to obtain a tailored performance from existing ionomers as well as enable development of better customized materials for the future.
Examining the Impact of Solution and Surface Composition on Positive Electrode Kinetics for the All-Iron Redox Flow Battery
Authors: Springer Renaldo E , Zimudzi Tawanda J , Hall Derek M.
Published: November 2022

Efforts to reduce the cost of long-duration energy storage systems have drawn increased interest in all-iron redox flow battery systems due to their inexpensive electrolytes. Previous studies have shown that the kinetics of the positive electrode for the Fe(II, III) reaction in these systems are sluggish on carbon surfaces and require significant overpotentials. Here, we identify how changes to the electrode surface and electrolyte composition can influence the electrochemical rate constants to reduce required overpotentials using a rotating disc electrode (RDE) assembly. The impacts of solution composition in terms of pH, chloride content, and cation species were investigated using a range of electrolyte compositions reported for all-iron flow battery systems. The electrode materials studied were glassy carbon, pyrolytic graphite basal plane, and pyrolytic graphite edge plane. Untreated and electrochemically oxidized electrode materials were quantified using X-ray photoelectron spectroscopy (XPS), and the reaction rate constants were quantified using electron impedance spectroscopy (EIS). Rate constants of the Fe(II, III) reaction on untreated electrode materials were largest on platinum and lowest on glassy carbon with pyrolytic materials providing comparable results. For the materials examined, increases electrolyte chloride content generally decreased the obtained rate constant.
Time-Dependent Development of Mesoporosity in Ionic Liquid Treated Cellulosic Materials
Authors: Aiello Ashlee , Cosby James , Durkin David P. , Trulove Paul C.
Published: November 2022

Natural Fiber Welding (NFW) is process that leverages the unique solvating power of ionic liquids (IL) to mobilize a natural fiber’s outermost polymer strands and enable these mobile polymers to reconfigure and interact with mobilized polymers of adjacent fibers. Upon removal of the ionic liquid via a solvent exchange and drying process, the biopolymer material is welded into a new matrix while still maintaining the vast majority of its native structural hierarchy. Recent work in our laboratory has shown relatively simple modifications to the NFW process can drastically impact the modified matrix morphology, particularly regarding surface structure. Changes in polarity during the solvent exchange process, for instance, can be used to very the surface area over a 1000-fold and produce high surface are materials with tunable mesoporosity. In the present work we investigate the impact of variable ionic liquid treatment time on the development of mesoporosity in fiber welded cotton substrates. Nitrogen gas adsorption/desorption measurements were employed to evaluate changes in surface area and pore size with ionic liquid treatment time. Raman spectroscopy was carried out on epoxy potted material cross sections to assess the impact of treatment time on cellulose decrystallization, and epoxy penetration measured by Raman spectroscopy was used to evaluate the continuity of the mesoporous regions and further asses material porosity.
In-Situ Characterization of Electroreduced Tantalum and Niobium in Deep Eutectic Solvents
Authors: Frater Theodore , Maurer Joshua A.
Published: November 2022

Room temperature ionic solvents are expected to possess electrochemical properties suitable for tantalum and niobium redox analogous to high temperature molten salts, in which successful bulk metal electrodeposition is reported. However, with the combination of perplexing multivalent chemistry of niobium and tantalum and alien electrochemical properties of ionic solvents, when compared to better characterized aqueous environments, the fundamental understanding of the electrochemical behavior of niobium and tantalum in these promising, yet compositionally diverse, solvents is severely underpopulated. Herein we report a new toolbox of coordinating additives that form, in many traditional and ionic solvents, chemically-robust reduced niobium and tantalum complexes with distinct photometric and paramagnetic properties, that serve as metal redox indicators and intermediate valence traps during electroreduction. We showcase the utility of these indicator species for clarifying the electrochemical behavior of niobium and tantalum in chemically varied ionic solvent environments by comparing in-situ electrochemical UV-Vis and electron paramagnetic resonance (EPR) observations in a series of chemically dissimilar deep eutectic solvents.
The Impact of Phase Changes of Imidazolium Based Ionic Liquids on the Solubility of Hydrofluorocarbons
Authors: Baca Kalin , Olsen Greta , Haggard Dorothy , Bennett Madelyn , Matamoros Valenciano Lucia , Shiflett Mark
Published: November 2022

Project EARTH (Environmentally Applied Research Toward Hydrofluorocarbons) is focused on developing sustainable processes for selectively separating refrigerant mixtures with high global warming potentials. The initial focus of the project is R-410A which is widely used in both commercial refrigeration systems and residential air conditioning. It is an azeotropic mixture containing 50 wt.% HFC-32 (CH2F2) and 50 wt.% HFC-125 (CHF2CF3). The separation approaches being investigated include membranes, porous media, and the use of ionic liquids as entrainers for extractive distillation.

This poster will describe the work being conducted using ionic liquids and will specifically focus on the impact of phase changes of imidazolium based ionic liquids that are solid at room temperature on the solubility of HFC-32 and HFC-125. The poster will include an overview of how we use specialized equipment including a High-Pressure View Cell and Hiden Isochema IGA gravimetric microbalance to build a comprehensive understanding of these solubility differences.
Electrodeposited from Ion-Organic Melt Ti-B Protective Coatings on Al-Foil
Authors: Devyatkin Sergei Vladimirovich , Kuksenko Sergei , Pisanenko Alexandr , Kochetova Svetlana
Published: November 2022

The great demand for advanced batteries in applications such as mobile devices, the transportation sector, and stationary storage has spurred intensive research and development on rechargeable lithium batteries. The corrosion behavior of Al-foil, as material for theirs current collectors, has long been a concern due to uniform or localized pitting corrosion occurs in contact with an organic electrolyte. Pitting corrosion is attributed to inhomogeneous current flow through the aluminum / electrode interface and results in local breakdown of the passive film on Al-foil. Particular attention among different protective coatings of Al-foil excites Ti-B coatings as conductive and electrochemically inactive protective layers.

The main objectives of the present work are investigation of regimes for electrodeposition of Ti-B protective coatings onto Al-foil and examination of the corrosion behavior of Al-foil with such electrodeposited Ti-B protective coatings in contact with an organic electrolyte under various electrodes charging conditions.

Low melting point of aluminium (tm = 6600C) made impossible electrodeposition of Ti-B coatings from chloride-fluoride melts (tel = 7000C). But it is possible from ion-organic melts at 70−2000C. In this work was investigated electrodeposition of Ti-B coatings from carbamide melt contains titanium and boron oxides. Cyclic voltammetry has shown the limit current density and potential of electrochemical synthesis. Ultra fine Ti-B coatings were electrodeposited onto Al-foil at 1300C. Figure shows the surface morphologies of an obtained Ti-B coating. Such cost-effective method of obtaining Ti-B protective coatings on Al-foils gives excellent results under theirs using as current collectors in rechargeable lithium batteries.

Figure 1
Electrochemistry of Neodymium in an Equimolar NaCl-KCl Melt without and with Addition of Fluoride Ions
Authors: Markovich Sergey I , Popova Anna V , Kuznetsov Sergey A
Published: November 2022

An investigation of compounds of those few elements in the oxidation state (II), by opposition to the general trivalent lanthanides is of special interest. The present work follows our previous investigations on samarium, europium ytterbium chloride systems and, in particular, the electrochemical behavior of the Sm(III)/Sm(II), Eu(III)/Eu(II) Yb(III)/Yb(II) redox couples. It deals with neodimium compounds.

The electrochemical behavior of NdCl3 in molten salts was studied in few works, but only melts with a low melting point LiCl-KCl and LiCl-KCl-CsCl were investigated.

The electroreduction of NdCl3 in an equimolar NaCl-KCl mixture was studied in the temperature range 973-1123 K by different electrochemical methods. It was shown that the discharge of Nd(III) to Nd(II) is complicated by the disproportionation reaction (DPP):

3Nd(II) ↔ 2Nd(III) + Nd (1)

Ignoring of reaction DPP can lead to incorrect determination of values diffusion coefficients and formal standard redox potentials of the Nd(III)/Nd(II) redox couple. The relatively narrow interval of polarization rate was found when the recharge process was reversible and not accompanied by the DPP reaction. At these scan rates the diffusion coefficients and formal standard redox potentials of the Nd(III)/Nd(II) redox couple were determined by cyclic voltammetry.

The standard rate constants for the redox reaction Nd(III) + e- ↔ Nd(II) were calculated on the basis of cyclic voltammetry at sweep rates corresponding to the quasy-reversible process. The nature of working electrode on the rate of charge transfer for the Nd(III)/Nd(II) redox couple was studied. It was found that the values of k
s determined at a molybdenum electrode were higher than those at a glassy carbon electrode.

The introduction of fluorine anions into a chloride melt at a molar ratio of F-/Nd(III) = 5 leads to the disappearance of the recharge wave and only an ascending section associated with joint discharge of neodymium complexes and sodium and potassium cations was observed. Thus, the introduction of fluorine anions leads to stabilization of the highest oxidation state of neodymium in chloride-fluoride melt and neodymium in the oxidation state +2 does not exist in the melt.

Introducing of fluoride ions to the melt NaCl-KCl containing Nd(II) accompanied by reaction of disproportionation:

3NdCl4
2- + 12F- ↔ 2NdF6
3- + Nd + 12Cl- (2)

The standard rate constants of charge transfer for the Nd(III)/Nd(II) redox couple were compared with the values obtained for other redox couples of lanthanides and these results were discussed in connection with the strength and stability of complexes.
(Invited) Ionic Liquids As Polymeric Nanoparticle Coatings
Authors: Tanner Eden EL
Published: November 2022

One of the major challenges facing intravenous nanoparticle administration is the formation of protein coronae on the surface of injected nanoparticles, which prevents them from reaching the target tissue. Biocompatible ionic liquids (ILs) have been shown to have tunable interactions with biomolecules including proteins and are prone to rearrangement on charged surfaces. We show that this can be exploited to use designer protein avoidant-ionic liquids as polymeric coatings, which can protect the nanoparticle from being fouled by serum proteins in the blood. When the IL coated poly(lactic-co-glycolic acid) (PLGA) particles are injected into mice, they show reduced clearance compared to control poly(ethylene glycol) or bare PLGA particles. Instead of lung, kidney or splenic deposition, the IL-particles accumulate in the lung tissue after hitching a ride on red blood cells post-injection. This talk will discuss the development of ionic liquids for efficacious nanoparticle drug delivery, elucidate the lessons learnt thus far, describe the many challenges to come, and highlight the opportunities that arise at the intersection of physical chemistry and bioengineering.
Liquid Polymerized Ionic Liquids
Authors: Texter John
Published: November 2022

Polymerized ionic liquids (PIL) are being used in many advanced materials applications. An interesting subclass of PILs is composed of liquid PIL, LPIL. Such materials exhibit classical liquid properties and offer insight into the physics and physical chemistry of liquids and particles. We present an overview of LPIL and a classification scheme to usefully compartmentalize such materials for further design, optimization, and application. Several members of this class of LPIL are described in detail along with multiple applications. One member consists of organosiloxanes condensed on themselves to produce a novel type of solvent-free nanofluid. These materials are the first to experimentally illustrate polydispersity frustration of crystallization and to show that both freezing and glass transitions are lambda transitions. Another member comprises a functional core decorated with ionic liquid salts. Such materials can be used to mitigate embrittlement accompanying using nanofillers and to incorporate such nanofluids in diverse new materials and functional coatings. Linear LPIL offer similar advantages to those provided by molecular IL and promise to overcome leaching limitations in liquid supported membranes and polyeletrolyte membranes in batteries and fuel cells. Lastly, extension of PILs to polyurethanes and polyureas (PUs) and to polyesters (PEs) has resulted in the first known self-dispersing polyurethane and polyester dispersions (PUDs and PEDs, respectively). Several of their applications in stimuli responsive coatings and graphene dispersions are illustrated.
(Invited) Dielectric Screening of Ionic Liquids and Implications for Their Capacitance, Solvation, and Structural Properties
Authors: McDaniel Jesse , Hymel John , Renfro Chloe Anne
Published: November 2022

Development and utilization of ionic liquids for applications as electrolytes and solvents requires understanding their electrostatic interactions with solutes, co-solvents, and interfaces. In this regard, the bulk dielectric constant of an ionic liquid is of little use, but rather the dielectric response must be characterized at atomistic lengthscales. We will discuss the dielectric response of ionic liquids as computed from molecular dynamics simulations and statistical mechanical theory. We will then describe how the dielectric properties of ionic liquids are connected with observed trends in interfacial capacitance, solvation, and liquid structure. Comparisons will be made to aqueous electrolytes and molten salts, and similarities and differences will be discussed.
Physical and Electrochemical Properties of Pyrrolidinium-Based Ionic Liquid and Methyl Propionate Co-Solvent Electrolyte
Authors: Keating Michael , Oh Seungmin , Biddinger Elizabeth J.
Published: November 2022

Advancements in modern technology has led to increasing demand for high-capacity batteries. Lithium metal batteries have high specific capacity and are a promising candidate for post lithium-ion batteries. Traditional organic electrolytes have poor compatibility with lithium metal batteries. Ionic liquids (IL) with the addition of co-solvents have shown promised in lithium metal battery systems. In this work, 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide ([Pyr14][TFSI]) was selected for its large electrochemical window and methyl propionate (MP) for its low viscosity and melting point. The IL/MP mixture with 0.8m LiTFSI maintained a large electrochemical window (>5V), extended liquid range of the IL and noticeably improved conductivity (from 0.56 mS/cm for 0.8m LiTFSI in [Pyr14][TFSI] to 11 mS/cm for 0.8m LiTFSI in a mixture of 1 to 7 mole ratio of [Pyr14][TFSI] to MP at 25°C). Also, we have identified that the addition of cyclic carbonate is important to increase the columbic efficiency for lithium deposition and stripping.
Physical and Electrochemical Analysis of Novel Boronium Cation-Based Ionic Liquids
Authors: Stachurski Christopher D. , Davis James H. , Cosby James , Larm Nathaniel E. , Durkin David P. , Trulove Paul C.
Published: November 2022

The designer nature of ionic liquids makes them a promising material for applications spanning disciplines from material processing to energy generation. While a great deal of interest has been directed towards dialkylimidazolium-based ionic liquids, there are many understudied classes of cations with favorable properties for energy related applications, such as disubstituted boroniums. To date only a handful of boronium cation-based ionic liquids have been thoroughly characterized despite exhibiting electrochemical stabilities (> 5.0 V) far surpassing what is seen with their alkylimidazolium and alkylpyrrolidinium counterparts. This work investigates a series of novel boronium-bistriflimide [TFSI-] ionic liquids using electrochemical and physical characterization techniques such as cyclic voltammetry, broadband dielectric spectroscopy, oscillatory shear rheology, and thermogravimetric analysis. Systematic variations in boronium cation structure were employed to help identify the structural motifs that lead to optimal electrochemical and physical properties. The best performing boronium-based ionic liquids were then tested for initial lithium stability to further probe their potential for use in battery applications.
Insights into Ionic Liquid Electrolyte and Redox Mediator Design for Dye Sensitized Solar Cells
Authors: Mudring Anja Verena
Published: November 2022

We are currently living in an energy crisis. It has been realized that not only our energy consumption is rising and that we have to be aware to reduce our carbon footprint in order to mitigate climate change, but we are also seeing that carbon-based energy sources become critical resources, like critical raw materials, when they come for region of political instability. For all these reasons, it is important to advance energy harvesting from benign resources, such as sun light. It is assumed that harvesting the solar energy reaching the earth at 10 % efficiency would be enough to cover the current global electricity consumption. In this context, dye sensitized solar cells (DSSCs) are interesting. They are not only promising low-cost alternatives to semi-conductor solar cells, but they bear additional properties, such as being able to absorb diffused light, flexibility and transparence, which allows them to be used in many different application, consumer electronics being a very relevant market. Particularly interesting for the low cost segment of solar cells would be if they could be made in air and not necessarily would require a strict encapsulation of the components. In this context, we have investigated a series of DSSCs with triazolium halides as the electrolyte. Interestingly, they DSSCs surpassed the performance of those with analogous imidazolium compounds and even had higher lifetimes. A particular advantage over imidazolium salts is, that the triazolium analogues are not hygroscopic, which makes device fabrication easier and also leads to a significantly long-term stability of the devices. In addition, electrode passivation which is commonly observed with imidazolium iodides could not be noticed for the triazolium analogues. This renders triazolium ionic liquids interesting candidates for electrochemical applications, not only for DSSCs.
Electrodeposition of Aluminium and Co-Deposition of Alloying Elements Titanium, Manganese and Silicon in Molten Fluoride Electrolyte
Authors: Haarberg Geir Martin , Awayssa Omar , Meirbekova Rauan , Xu Wenting , Saevarsdottir Gudrun
Published: November 2022

Primary aluminium is produced by the Hall-Heroult process which is based on electrolysis in molten fluoride electrolyte, Na3AlF6-AlF3, at ~960 oC in which the raw material alumina is dissolved and decomposed into pure aluminium and CO2 gas due to the use of carbon anodes. Alloys are made by adding pure metals prior to the casting process. An alternative approach to produce alloys by co-deposition of alloying elements during electrolysis, where metal oxides of alloying elements are added to the electrolyte, is under study. Laboratory experiments were carried out to quantify the impact of co-deposition of alloying elements of titanium, manganese and silicon. The experimental set-up was dedicated to determine the current efficiency of aluminium and aluminium based alloys during galvanostatic electrolysis.

Current efficiencies above 90 % were obtained for electrodeposition of aluminium alloys with titanium, manganese and silicon. It was found that the current efficency decreasde a few percentage points compared to the current efficiency for deposition of pure aluminium. The content of deposited allloying element was determined by ICP analysis of deposits. By adding from 1 - 3 wt% of metal oxide to the electrolyte the content of alloying element was found to be typically ~ 5 - 10 wt% after electrolysis. Experiments were carried out by changing temperature and amount of added metal oxide.

The proposed method for producing aluminium based alloys directly in the Hall-Heroult process may give substantial benefits in terms of cost and efficiency. Challenges are related to metal oxide solubilities and control of the alloy composition.