A promising nonaqueous redox flow battery electrolyte has been developed by leveraging natural selection to elucidate stable, redox-active molecules.
Potentiometric plasticizer-free solid-contact Pb2+-selective electrodes based on copolymer methyl methacrylate-n-butyl acrylate (MMA-BA) as membrane matrix and multi-walled carbon nanotubes (MWCNTs) as intermediate ion-to-electron transducing layer have been developed. The disposable electrodes were prepared by drop-casting the copolymer membrane onto a layer of MWCNTs, which deposited on golden disk electrodes. The obtained electrodes exhibited a sub-ppb level detection limit of 10−10 mol·L−1. The proposed electrodes demonstrated a Nernstian slope of 29.1 ± 0.5 mV/decade in the linear range from 2.0 × 10−10 to 1.5 × 10−3 mol·L−1. No interference from gases (O2 and CO2) or water films was observed. The electrochemical impedance spectroscopy of the fabricated electrodes was compared to that of plasticizer-free Pb2+-selective electrodes without MWCNTs as intermediated layers. The plasticizer-free MWCNTs-based Pb2+-selective electrodes can provide a promising platform for Pb(II) detection in environmental and clinical application.
The title compound, C8H4BrNO2, has a single planar molecule in the asymmetric unit with the non-H atoms possessing a mean deviation from planarity of 0.024 Å. The molecules dimerize in the solid state through N—H...O hydrogen bonds. There are intermolecular Br...O close contacts at 3.0430 (14) Å. The nine-membered rings of the isatins stack along [001] with parallel slipped π–π interactions [inter-centroid distance: 3.7173 (6) Å, inter-planar distance: 3.3110 (8) Å, slippage: 1.6898 (14) Å].
There is a strong and growing need for reliable, cost-effective grid storage to support a transition from fossil fuels. Non-aqueous redox-flow batteries (NRFB) are a promising technology to meet this need but they are currently limited by poor stability of solution-phase, charge-carrying metal complexes. A major mechanism of decomposition of these redox electrolytes is substitution of ligands that have weak interactions with substitution-labile metal ions. Presented herein is an approach to mitigate these thermodynamic and kinetic challenges with a naturally occurring compound that is produced biologically. Mushrooms of the genus Amanita synthesize a molecule known as Amavadin, in which a vanadium ion is tightly coordinated by a pair of 2,2’-(hydroxyimino)dipropionic acid (HIDPA) ligands. Millions of generations of evolution have optimized the stability of this molecule. As a result, under physiological conditions in which most vanadium compounds would decompose, ligand substitution is suppressed. The electrochemical properties of redox molecules based on Amavadin as NRFB electrolytes will be presented. This will include data on electrochemical reversibility and stability to deep redox-cycling under various conditions. In addition, we will present the results of computational investigations that have guided ligand-design efforts. These are focused on optimization of the properties of Amavadin-based compounds for application in energy storage devices without losing their extraordinary ability to bind metal ions.
Recently, a significant emphasis has been placed on non-aqueous electrolytes for use in redox flow batteries due to their wider electrochemical potential windows, offering higher energy and power densities. To date, several non-aqueous electrolytes using organic molecules [1-2] and metal-ligand complexes [3] have been evaluated for use as electrolytes in non-aqueous redox flow battery (NRFB) systems. With these efforts, substantial performance enhancements, including a several-fold increase in energy density and improved operating temperature range, are possible compared to state-of-the- art vanadium/sulfuric acid flow batteries; however, NRFB progress has been hampered by poor electrolyte stability [4]. Thus far, development has been limited to systems with short cycle-life that exhibit capacity-fade and low current density. This underscores a key challenge currently limiting the advancement of these technologies – the stability. We employ a bio-inspired approach to address the problem of redox-couple instability that impedes commercialization of NRFB. Our strategy of molecular design is based on naturally occurring chelating molecules that have evolved to bind metal ions extraordinarily tightly and with high-specificity. With this approach we have targeted Amavadin, a vanadium compound found in mushrooms of the Amanita genus. This molecule, and its analog, calcium vanadium(iv)bis-hydroxyiminodiacetate (CVBH) (Figure 1 inset) are among the most stable vanadium chelates ever elucidated. Initial, static-cell investigations have demonstrated that CVBH is stable to exhaustive, deep redox cycling (Figure 1), making it an excellent candidate for implementation in an NRFB system. In this presentation we will demonstrate the performance of such an NRFB system, using this mushroom-based (CVBH) electrolyte. Results include battery cycling as well as capacity fade and efficiency analyses. The results of these analyses with respect to various operating conditions and flow cell components will also be reported. References: [1] Milshtein, J. D., Kaur, A. P., Casselman, M. D., Kowalski, J. A., Modekrutti, S., Zhang, P. L., Harsha Attanayake, N., Elliott, C. F., Parkin, S. R., Risko, C., Brushett, F. R., Odom, S. A. Energy Environ. Sci. 2016, 9 (11), 3531-3541. [2] Wei, X., Xu, W., Vijayakumar, M., Cosimbescu, L., Liu, T., Sprenkle, V., Wang, W. Adv. Mater. 2014, 26 (45), 7649-7653. [3] Suttil, J. A., Kucharyson, J. F., Escalante-Garcia, I. L., Cabrera, P. J., James, B. R., Savinell, R. F., Sanford, M. S., Thompson, L. T. J. Mater. Chem. A 2015, 3 (15), 7929-7938. [4] Carino, E. V., Staszak-Jirkovsky, J., Assary, R. S., Curtiss, L. A., Markovic, N. M., Brushett, F. R. Chem. Mater. 2016, 28 (8), 2529-2539. Figure 1
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