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At least 19 records

Comparison of Quinone-Based Catholytes for Aqueous Redox Flow Batteries and Demonstration of Long-Term Stability with Tetrasubstituted Quinones

Quinones are appealing targets as organic electrolytes for aqueous redox flow batteries (RFBs), but their utility continues to be constrained by limited stability under operating conditions. The present study evaluates the stability of a series water-soluble quinones, with redox potentials ranging from 605–885 mV vs. NHE, under acidic aqueous conditions (1 M H2SO4). Four of the quinones are examined as cathodic electrolytes in an aqueous RFB, paired with anthraquinone-2,7-disulfonate (AQDS) as the anodic electrolyte. The RFB data complement the solution stability measures and show that the most stable electrolyte is a tetrasubstituted quinone containing four sulfonated thioether substituents. The results highlight the importance of substituting all C–H positions of the quinone in order to maximize the quinone stability and set the stage for design of improve organic electrolytes for aqueous RFBs. The authors thank Joseph Fourie for assisting in the synthesis of compound 8. Financial support for this work was provided by the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (SSS, TWR, JBG, CWA, YP), with supplemental contributions by the Wisconsin Alumni Research Foundation (WARF) through the WARF Accelerator Program (YQ and partial support for JBG, CWA, YP). NMR spectroscopy facilities were partially supported by the NSF (CHE-0342998 and CHE-1048642), a UW Madison Instructional Laboratory Modernization Award, and a gift from Paul J. and Margaret M. Bender.

aqueous flow batteries, quinones, organic, redox m↗

Revealing Hidden Quinones Through Diagnostic MS² Fragmentation of Peptide–Quinone Adducts

Quinones are redox-active components of natural organic matter that mediate electron transfer and influence biogeochemical processes, but many quinones in pyrogenic organic matter (PyOM) remain unresolved because they ionize poorly by mass spectrometry. Here, we present a peptide-tagging approach to improve detection of cysteine-reactive electrophiles in PyOM, with quinones expected to be a dominant subset based on reaction chemistry and selectivity experiments. A cysteine-containing peptide was used to form Michael-addition adducts, enhancing electrospray ionization and enabling untargeted screening by high-performance liquid chromatography-high-resolution tandem mass spectrometry. The method was benchmarked with five quinone standards and applied to extracts from charred plant material as a discovery-level screen for cysteine-reactive targets. We identified 98 quinone-candidate adducts (mean neutral mass ~603 Da), of which more than 70% were not detectable in native MS1 data. Among formula-assigned features, hidden quinone candidates had median (O+N)/C of 0.391 and normalized oxidation state of carbon of -0.281, consistent with relatively low polarity and low oxidation state. These results reveal a previously inaccessible pool of hidden redox-active compounds in PyOM and provide a framework for prioritizing quinone-like electrophiles for confirmation and incorporation into models of fire-driven biogeochemical cycling.

LC-MS/MS↗

Lactiplantibacillus plantarum uses ecologically relevant, exogenous quinones for extracellular electron transfer

Extracellular electron transfer (EET) is a metabolic process that frequently uses quinones to couple intracellular redox reactions with extracellular electron acceptors. The physiological relevance of this metabolism for microorganisms capable of EET but unable to synthesize their own quinones remains to be determined. To address this question, we investigated quinone utilization by Lactiplantibacillus plantarum, a microorganism required for food fermentations, that performs EET and is also a quinone auxotroph. L. plantarum selectively used 1,4-dihydroxy-2-naphthoic acid (DHNA) and more hydrophilic naphthoquinones for EET reduction of insoluble iron (ferrihydrite). However, quinones used for EET also inhibited L. plantarum growth in non-aerated conditions. Transcriptomic analysis showed that DHNA-induced oxidative stress in L. plantarum, but this was alleviated when the electron acceptor, ferric ammonium citrate (FeAC), was included in the growth medium. Although DHNA and FeAC induced L. plantarum EET, this metabolism was still dependent on direct access to environmental electron shuttles. To determine whether quinone-producing food fermentation bacteria could be sources of those electron shuttles, L. plantarum EET was measured after incubation with Lactococcus lactis and Leuconostoc mesenteroides. Quinone-producing L. lactis, but not a quinone-deficient L. lactis ΔmenC mutant, increased L. plantarum ferrihydrite reduction and medium acidification through an EET-dependent mechanism. L. plantarum EET was also stimulated by L. mesenteroides, resulting in greater environmental acidification and transient increases in L. plantarum cell numbers. Our findings show that L. plantarum overcomes the toxic effects of exogenous quinones to use those compounds for EET-conferred, ecological advantages during the early stages of food fermentations.

59 BASIC BIOLOGICAL SCIENCES↗

Quinone and hydroquinone based flow battery

The invention provides an electrochemical cell based on a new chemistry for a flow battery for large scale, e.g., gridscale, electrical energy storage. Electrical energy is stored chemically in quinone molecules having multiple oxidation states, e.g., three or more. During charging of the battery, the quinone molecules at one electrode are oxidized by emitting electrons and protons, and the quinone molecules at the other electrode are reduced by accepting electrons and protons. These reactions are reversed to deliver electrical energy. The invention also provides additional high and low potential quinones that are useful in rechargeable batteries.

Huskinson, Brian↗

Effect of Molecular Structure of Quinones and Carbon Electrode Surfaces on the Interfacial Electron Transfer Process

Quinones can undergo thermodynamically reversible proton-coupled electron transfer reactions and are being applied as electroactive compounds in aqueous organic batteries. However, the electrochemical reversibility of these compounds is affected not only by their molecular structure but also by the properties of a carbon-based electrode surface. This study combines experimental and theoretical approaches to understand this dependence. Specifically, we study the electron transfer kinetics of two synthesized quinone derivatives and two commercially available ones with a glassy carbon, a highly ordered pyrolytic graphite, and a high-edge-density graphite electrode (HEDGE). The electrochemical reversibility is notably improved on the HEDGE, which shows a higher density of defects and presents oxygenated functional groups at its surface. The electron transfer kinetics are controlled by adsorbed species onto the HEDGE. Molecular dynamics simulation and quantum mechanics calculations suggest defects with oxygen-containing functional groups, such as C-O and C$=$O, on HEDGE surfaces drive the interaction with the functional groups of the molecules, during physisorption from van der Waals forces. The presence of sulfonic acid side groups and a greater number of aromatic rings in the molecular structure may contribute to a higher stabilization of quinone derivatives on HEDGEs. We propose that high-performance carbon-based electrodes can be obtained without catalysts for organic batteries, by the engineering of carbon-based surfaces with edge-like defects and oxygenated functional groups.

25 ENERGY STORAGE↗

High-solubility thioether quinones

Substituted hydroquinones and quinones and methods of synthesizing such compounds are disclosed herein. The substituted hydroquinones have the formula: while the substituted quinones have the corresponding oxidized structure (1,4-benzoquinones). One, two, three, or all four of R1, R2, R3 and R4 comprise a thioether moiety and a sulfonate moiety, and wherein each R1, R2, R3 and R4 that does not comprise a thioether and a sulfonate moiety sulfonate moiety is independently a hydrogen, an alkyl or an electron withdrawing group. The substituted hydroquinones and quinones are soluble in water, stable in aqueous acid solutions, and have a high reduction potential in the oxidized form. Accordingly, they can be used as redox mediators in emerging technologies, such as in mediated fuel cells or organic-mediator flow batteries.

36 MATERIALS SCIENCE↗

High solubility thioether quinones

Substituted hydroquinones and quinones and methods of synthesizing such compounds are disclosed herein. The substituted hydroquinones have the formula: while the substituted quinones have the corresponding oxidized structure (1,4-benzoquinones). One, two, three, or all four of R1, R2, R3 and R4 comprise a thioether moiety and a sulfonate moiety, and wherein each R1, R2, R3 and R4 that does not comprise a thioether and a sulfonate moiety sulfonate moiety is independently a hydrogen, an alkyl or an electron withdrawing group. The substituted hydroquinones and quinones are soluble in water, stable in aqueous acid solutions, and have a high reduction potential in the oxidized form. Accordingly, they can be used as redox mediators in emerging technologies, such as in mediated fuel cells or organic-mediator flow batteries.

Stahl, Shannon S.↗

Stable Tetrasubstituted Quinone Redox Reservoir for Enhancing Decoupled Hydrogen and Oxygen Evolution

In this report, we discuss Redox reservoirs (RRs) that may be used to decouple the two half-reactions of water electrolysis, enabling the spatial and temporal separation of hydrogen and oxygen evolution. Organic RRs are appealing candidates for this application; however, their instability limits their utility. Here we show that a tetrathioether-substituted quinone, tetramercaptopropanesulfonate quinone (TMQ), exhibits significantly enhanced stability relative to anthraquinone-2,7-disulfonate, the most effective organic RR reported previously. The enhanced stability, confirmed by symmetric flow-battery experiments under relevant conditions, enables the stable electrochemical production of H 2 and O 2 in a continuous-flow electrolysis cell. The reduced RR, tetramercaptopropanesulfonate hydroquinone, is not susceptible to decomposition, whereas the oxidized state, TMQ, undergoes slow decomposition, evident only after sustained operation (>60 h). The analysis of the byproducts provides a basis for a decomposition mechanism, establishing a foundation for the design of new organic RRs with even better performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Size and Charge Effects on Crossover of Flow Battery Reactants Evaluated by Quinone Permeabilities Through Nafion

Organic reactants are promising candidates for long-lifetime redox flow batteries, and synthetic chemistry unlocks a wide design space for new molecules. Minimizing crossover of these molecules through ion exchange membranes is one important design consideration, but the ways in which the crossover rate depends on the structure of the crossing species remain unclear. Here, we contribute a systematic evaluation of size- and charge-based effects on dilute-solution small molecule permeability through the Nafion NR212 cation exchange membrane. We found that increasing the magnitude of charge number z with the same sign as membrane fixed charges, achieved here by successive sulfonation of quinone redox cores, results in more than an order of magnitude permeability reduction per sulfonate. Size-based effects, understood by comparing the Stokes radii of the quinones studied, also reduces permeability with increasing effective molecule size, but doubling the effective size of the redox reactants resulted in a permeability decrease of less than a factor of three.

25 ENERGY STORAGE↗

Electrochemical CO 2 Capture by a Quinone-Based Covalent Organic Framework

Electrochemical CO 2 capture is an emerging technology that promises to be more energy-efficient than traditional thermal or pressure-swing processes. Herein, the first evidence of electrochemical capture of CO 2 using a covalent organic framework (COF) is presented. We hypothesized that the assembly of anthraquinone units into a well-defined porous framework electrode would lead to enhanced electrochemical CO 2 capture compared to previous approaches that grafted anthraquinones on carbon supports and suffered from low CO 2 capacities and stabilities. To test this, an anthraquinone-based COF is employed, and it is found that the quinones are electrochemically accessible for reversible CO 2 capture in an ionic liquid electrolyte. The system achieves a high electrochemical CO 2 uptake capacity >2.6 mmol g –1 COF, reaching half of the theoretical CO 2 capacity of the material and surpassing the capacities of anthraquinone-functionalized carbons. The stability and CO 2 uptake rate issues encountered with the ionic liquid system are also addressed by using aqueous electrolytes where we attained stable carbon capture for 500 cycles with a 99.6% Coulombic efficiency and an electrical energy consumption of 31 kJ mol CO 2 –1 . The use of covalent organic framework electrodes can become a general strategy for understanding and enhancing the electrochemical CO 2 capture.

carbon capture and storage↗

Mechanochemical synthesis of pillar[5]quinone derived multi-microporous organic polymers for radioactive organic iodide capture and storage

The incorporation of supramolecular macrocycles into porous organic polymers may endow the material with enhanced uptake of specific guests through host–guest interactions. Here we report a solvent and catalyst-free mechanochemical synthesis of pillar[5]quinone (P5Q) derived multi-microporous organic polymers with hydrophenazine linkages (MHP-P5Q), which show a unique 3-step N 2 adsorption isotherm. In comparison with analogous microporous hydrophenazine-linked organic polymers (MHPs) obtained using simple twofold benzoquinones, MHP-P5Q is demonstrated to have a superior performance in radioactive iodomethane (CH 3 I) capture and storage. Mechanistic studies show that the rigid pillar[5]arene cavity has additional binding sites though host–guest interactions as well as the halogen bond (-I···N = C-) and chemical adsorption in the multi-microporous MHP-P5Q mainly account for the rapid and high-capacity adsorption and long-term storage of CH 3 I.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Overexpression of sulfide:quinone reductase (SQR) in Acidithiobacillus ferrooxidans enhances sulfur, pyrite, and pyrrhotite oxidation

ABSTRACT Hydrogen sulfide is produced during the dissolution of some sulfidic minerals and during the microbial metabolism of reduced sulfur compounds. The sulfide:quinone reductase (SQR) enzyme is able to oxidize H 2 S, and the bioleaching cells Acidithiobacillus ferrooxidans have two SQR genes, only one of which has been characterized. We cloned and overexpressed the two SQR genes in A. ferrooxidans and show that they both have SQR activity. Both AFE_0267 and AFE_1792 are active under anaerobic conditions, but only AFE_1792 is active under aerobic conditions. The effect of the SQR overexpression and the expression of related genes on sulfur metabolism was investigated. The overexpression of SQR improved cell growth and sulfur oxidation, suggesting enhanced SQR activity led to a reduction in H 2 S toxicity as well as providing additional energy through H 2 S oxidation. Additionally, the impact on the oxidation of pyrite and pyrrhotite was investigated. The rate of oxidation of pyrite by the engineered cells was enhanced, and, furthermore, the rate of pyrrhotite oxidation was more than doubled. IMPORTANCE H 2 S is a toxic sulfur intermediate, and the SQR enzyme has evolved to oxidize H 2 S in A. ferrooxidans . In addition to detoxification, H 2 S oxidation provides energy, and overexpression of SQR enhanced aerobic and anaerobic growth on sulfur. The SQR overexpression also enhanced pyrite and pyrrhotite oxidation, which may facilitate the pyrometallurgical processing of a number of critical materials including copper, nickel, and the platinum group metals.

Jung, Heejung↗

Mechanistic Insights in Quinone-Based Zinc Batteries with Nonaqueous Electrolytes

Three quinone-based organic electrodes were tested in nonaqueous Zn-batteries using different salts and solvents. The Zn(TFSI)(2)/acetonitrile system exhibited the best performance due to its excellent transport and electrochemical properties. The mechanistic studies on the electrode kinetics were also carried out. While 2,5-dimethoxybenzoquinone (DMBQ) displayed a typical faradaic battery behavior, its polymeric derivatives showed a slow charge transfer inside the polymeric film as depicted by cyclic voltammograms. (C) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.

organic electrode, electrolyte, mechanism↗

A quinone-assisted photoformation of energy-rich chemical bonds

In a study of biochemical means of solar energy conversion, ADP and inorganic phosphates were converted to ATP by white light in the nonaqueous solvent dimethylformamide in the presence of tetrachloro-p-quinone or ubiquinone. Conversion of ADP to ATP has been accomplished in aqueous suspension by the use of cell-like structures aggregated from poly(aspartic acid, glutamic acid, tyrosine). This is believed to occur through the formation of dopaquinone in the peptide structure during illumination. The way in which the quantitative yield of ATP has been influenced by pH and by added substances, such as FeCl2, was studied.

Fox, S. W.↗