Bromine Research Articles

Elemental Composition and Sources of Fine Particulate Matter (PM2.5) in Delhi, India.

In this study we have analysed the elemental composition of fine particulate matter (PM2.5) to examine the seasonal changes and sources of the elements in Delhi, India from January, 2017 to December, 2021. During the entire sampling period, 19 elements (Al, Fe, Ti, Cu, Zn, Cr, Ni, As, Mo, Cl, P, S, K, Pb, Na, Mg, Ca, Mn, and Br) of PM2.5 were identified by Wavelength Dispersive X-ray Fluorescence Spectrometer. The higher annual mean concentrations of S (2.29µg m-3), Cl (2.26µg m-3), K (2.05µg m-3), Ca (0.96µg m-3) and Fe (0.93µg m-3) were recorded during post-monsoon season followed by Zn > Pb > Al > Na > Cu > Ti > As > Cr > Mo > Br > Mg > Ni > Mn > and P. The annual mean concentrations of elemental composition of PM2.5 accounted for 10% of PM2.5 (pooled estimate of 5 year). Principal Component Analysis (PCA) identified the five main sources [crustal/soil/road dust, combustion (BB + FFC), vehicular emissions (VE), industrial emissions (IE) and mixed source (Ti, Cr and Mo rich-source)] of PM2.5 in Delhi, India.

Hydrogeochemical processes in rural coastal aquifer (Haha region, Morocco).

In arid and semi-arid regions, groundwater is the principal source of urban and rural water supply. Given that groundwater is the only source of water supply in the Haha region (Moroccan Atlantic coast), the evaluation of this vital resource, using the hydrogeochemical approach, is the main objective of this study. The interpretation of these analytical data showed that the chemical composition of the groundwater is of Ca-Mg-Cl, Na-HCO3, and Na-Cl, with the dominance of the first type. Hydrochemical characteristics using the bivariate diagrams of major (Ca2+, Mg2+, Na+, K+, HCO3-, Cl-, NO3-, and SO42-) and some trace elements (Br- and F-), mineral saturation indices, and statistical analysis show that the water-rock interaction, cation exchange processes, and marine effect are the main processes that control groundwater mineralization. Also, the majority of analyzed samples have concentrations above the thresholds for human consumption fixed by WHO, especially F-, NO3-, K+, Cl-, and HCO3- concentrations. This requires treatment of this groundwater before any consumption and domestic uses. For agricultural uses, the groundwater of the Haha region remains adequate, especially for plants, which can withstand water with electrical conductivity greater than 1000 µS/cm. However, the results obtained can be used as a basis for decision-makers for better water management in the Haha region.

Levels and distribution of chemical elements in house dust from the area of an abandoned Pb-Zn smelter in North Macedonia

The content of 41 chemical elements (Ag, Al, As, Au, Ba, Br, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Hf, In, K, La, Li, Mg, Mn, Mo, Na, Nd, Ni, P, Pb, Rb, Sb, Sc, Se, Sm, Sr, Tb, Th, Ti, Tm, U, V, W, and Zn) was determined in attic dust, household dust and soil samples collected from 33 houses in the area of the town of Veles, North Macedonia. Silver, Cd, Cu, Li, P, and, Pb were analyzed by inductively coupled plasma - atomic emission spectrometry while the other elements were analyzed by neutron activation analysis. The study area has been continuously exposed to high amounts of potentially toxic elements due to the emission from an abandoned Pb-Zn smelter plant. In this study, attic and household dust together with soil samples collected from the yards of the houses were used to assess the level of historical and present air contamination by potentially toxic elements. It was found that the contents of Ag, As, Cd, Cu, In, Pb, Sb, Se, and, Zn in dust samples represented an anthropogenic association of elements, with very high contents in samples collected from the town of Veles, which is close to the Pb-Zn smelter, compared with those collected from the mountainous area.

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine.

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.

Large presence of bromine and toxic metals in ambient fine particles from urban fires

Urban fires in densely populated areas can burn large amounts of manmade structures and synthetic materials. Realworld chemical composition data of urban fire plumes are vital for evaluating health impacts; however, they are rarely available. Online monitoring of trace elements in ambient PM2.5 at five sites throughout Hong Kong in 2021 provided unprecedented opportunities to observe the highly transient fire plumes. Sharp spikes were captured for bromine (up to 0.65 μg m−3), chlorine (7.0 μg m−3), and certain metals such as lead (0.97 μg m−3), zinc (8.3 μg m−3), and copper (0.32 μg m−3) during four urban fires, showing ∼10–6000 times higher concentrations than pre-fire periods. These elements showed decreased concentrations with increased distance from the fire location, but their concentration ratios remained relatively constant. During fire-influenced hours, these elements exhibited 3–101 times enrichment relative to iron, an element that had no discernible increase in concentration. Our results represent the first observation of the co-emissions of Br and certain metals from urban fires. Reactive bromine released from burning of the wide-spread brominated synthetic chemicals was suggested to facilitate the mobilization of toxic metals into the atmosphere. This mechanistic knowledge will help us understand the emissions and impacts of fires occurring in wildland urban interface zones. The work also calls attention to previously overlooked influence of urban fires-mobilized metals on human health and of bromine on atmospheric oxidizing capacity in megacities.

Elemental Variability of PM2.5 Aerosols in Historical and Modern Areas of Jeddah, Saudi Arabia

Air particulate matter with a diameter of 2.5 µm (PM2.5) were assembled for a whole year from the historical Jeddah district. Additional PM2.5 aerosols were collected during the autumn and winter seasons from another newly constructed district in Jeddah city (Alnaeem). The annual concentration of the total mass of the PM2.5 aerosols from the historical Jeddah site was found to be 43 ± 6 µg/m3. In addition, the average of the total mass concentration at the Alnaeem site was 61 ± 14 µg/m3. These values were greater than the annual mass concentration of the air quality standards of the European Commission (25 µg/m3) and the World Health Organization (10 µg/m3). The elemental analysis of the collected fine atmospheric aerosols was achieved by energy dispersive X-ray fluorescence (EDXRF) with three secondary targets (CaF2, Ge, and Mo). Quantitative elemental analyses of twenty-two (22) elements were achieved starting from the low atomic number element (Na) up to the high atomic number element (Pb). Although the historical Jeddah site is not well organized, the elemental concentrations and total mass concentrations were lower than those of the other site. The statistical analyses including enrichment factors, correlation analysis, and the principal component analysis revealed more information about the source identification of the PM2.5 aerosols collected from both locations. It was recognized that the elements Al, Si, K, Ca, Ti, Mn, Fe, Rb, and Sr originated from a natural source. On the other hand, the elements Ta, Br, Pb, Sc, Ni, Cu, Zn, and S originated from anthropogenic sources. Finally, the elements Na, Cl, and Br came mainly from the sea spray source.

Apparent Reactivity of Bromine in Bromochloramine Depends on Synthesis Method: Implicating Bromine Chloride and Molecular Bromine as Important Bromine Species.

The chloramination of bromide containing waters results in the formation of bromine containing haloamines: monobromamine (NH2Br), dibromamine (NHBr2), and bromochloramine (NHBrCl). Many studies have directly shown that bromamines are more reactive than chloramines in oxidation and substitution reactions with organic water constituents because the bromine atom in oxidants is more labile than the chlorine atom. However, similar studies have not been performed with NHBrCl. It has been assumed that NHBrCl has similar reactivity as bromamines with organic constituents in both oxidation and substitution reactions because NHBrCl, like bromamines, rapidly oxidizes N,N-diethyl-p-phenylenediamine. In this study, we examined the reactivity of NHBrCl with phenol red to determine if NHBrCl reacts as readily as bromamines in an isolated substitution reaction. NHBrCl was synthesized two ways to assess whether NHBrCl or the highly reactive intermediates, bromine chloride (BrCl) and molecular bromine (Br2), were responsible for bromine substitution of phenol red. NHBrCl was found to be much less reactive than bromamines with phenol red and that BrCl and Br2 appeared to be the true brominating agents in solutions where NHBrCl is formed. This work highlights the need to reexamine what the true brominating agents are in chloraminated waters containing bromide.

New Insights into the Role of Nitrite in the Degradation of Tetrabromobisphenol S by Sulfate Radical Oxidation.

Tetrabromobisphenol S (TBBPS) is a brominated flame retardant and a contaminant of emerging concern. Several studies found that sulfate radical (SO4•-) oxidation is effective to degrade TBBPS. Here, we demonstrate that the presence of nitrite (NO2-) at environmentally relevant levels causes dramatic changes in the kinetics and pathways of TBBPS degradation by SO4•-. Initially, NO2- suppresses the reaction by competing with TBBPS for SO4•-. At the same time, SO4•- oxidizes NO2- to form nitrogen dioxide radicals (NO2•), which actively react with some key TBBPS degradation intermediates, thus greatly altering the transformation pathway. As a result, 2,6-dibromo-4-nitrophenol (DBNP) becomes the primary TBBPS product. As TBBPS undergoes degradation, the released bromide (Br-) is oxidized by SO4•- to form bromine radicals and free bromine. These reactive bromine species immediately combine with NO2• or NO2- to form nitryl bromide (BrNO2) that in turn attacks the parent TBBPS, resulting in its accelerated degradation and increased formation of toxic nitrophenolic byproducts. These results show that nitryl halides (e.g., BrNO2 or ClNO2) are likely formed yet inadequately recognized when SO4•- is applied to remediate halogenated pollutants in the subsurface environment where NO2- is ubiquitously found. These insights further underscore the potential risks of the application of SO4•- oxidation for the remediation of halogenated compounds in realistic environmental conditions.

Multiphase Reactive Bromine Chemistry during Late Spring in the Arctic: Measurements of Gases, Particles, and Snow

Bromine radicals (Br·) cause ozone depletion and mercury deposition in the Arctic atmospheric boundary layer, following Polar sunrise. These Br radicals are primarily formed by the photolysis of molecular bromine (Br2), which is photochemically produced in the snowpack. Recently, it was shown that bromine monoxide (BrO·), formed from the reaction of Br· with ozone, is episodically present until the onset of snowmelt in late Arctic spring. To examine the drivers of this late spring shutdown of reactive bromine chemistry, the gases Br2, HOBr, BrO, and BrCl were continuously monitored using chemical ionization mass spectrometry during the spring (March–May 2016) near Utqiaġvik, Alaska. On May 10th, all four reactive bromine species fell below levels of detection at the same time that air temperature increased above 0 °C, surface albedo decreased, and snowmelt onset was observed. Prior to the cessation of atmospheric bromine chemistry, local surface snow samples in early May became significantly enriched in bromide, likely due to the slowdown of reactive bromine recycling with continued deposition but decreased emissions from the snowpack. Particulate bromide concentrations were not sufficient to explain the quantities of reactive bromine gases observed and decreased upon snowmelt. Low wind speeds during the weeks preceding the cessation of reactive bromine chemistry point to the lack of a contribution to bromine chemistry from blowing snow. Together, these results further highlight the significance of the surface snowpack in multiphase bromine recycling with important implications as the melt season arrives earlier due to climate change.

Preparation and Characterization of PAM‐b‐DOPOAA by ATRP

AbstractPolyacrylamide has been a hot topic of research in recent years, however, the preparation of block copolymers of polyacrylamide using ATRP method has been little studied. In this paper, polyacrylamide with reactive group bromine (PAM−Br) was synthesized by atom transfer radical polymerization (ATRP) using acrylamide (AM) as the monomer and water as the solvent, and polyacrylamide was used as the macromolecular initiator for the next reaction step. Then 9,10‐dihydro‐9‐oxa‐10‐phosphafi‐10‐oxide (DOPO) was organically modified to obtain acrylate monomers with DOPO functional groups (DOPOAA), and a mixture of water and N, N‐dimethylformamide (DMF) was used as the solvent to obtain PAM‐b‐DOPOAA block copolymers with controllable molecular mass and narrow molecular mass distribution. The effects of the molecular mass of the macromolecular initiator, polymerization time, and the molar ratio of catalyst to the ligand on the polymerization process were investigated. The structure and properties of the products were also characterized by 1H‐NMR, FTIR, XPS, DSC, TG, etc. The PAM‐b‐DOPOAA prepared by ATRP method can artificially design the length and ratio of the two chain segments, realizing one additive with two functions and the permanent existence of the function of polymer additives.

Comparison of model and ground observations finds snowpack and blowing snow aerosols both contribute to Arctic tropospheric reactive bromine

Abstract. Reactive halogens play a prominent role in the atmospheric chemistry of the Arctic during springtime. Field measurements and modeling studies suggest that halogens are emitted into the atmosphere from snowpack and reactions on wind-blown snow-sourced aerosols. The relative importance of snowpack and blowing snow sources is still debated, both at local scales and regionally throughout the Arctic. To understand the implications of these halogen sources on a pan-Arctic scale, we simulate Arctic reactive bromine chemistry in the atmospheric chemical transport model GEOS-Chem. Two mechanisms are included: (1) a blowing snow sea salt aerosol formation mechanism and (2) a snowpack mechanism assuming uniform molecular bromine production from all snow surfaces. We compare simulations including neither mechanism, each mechanism individually, and both mechanisms to examine conditions where one process may dominate or the mechanisms may interact. We compare the models using these mechanisms to observations of bromine monoxide (BrO) derived from multiple-axis differential optical absorption spectroscopy (MAX-DOAS) instruments on O-Buoy platforms on the sea ice and at a coastal site in Utqiaġvik, Alaska, during spring 2015. Model estimations of hourly and monthly average BrO are improved by assuming a constant yield of 0.1 % molecular bromine from all snowpack surfaces on ozone deposition. The blowing snow aerosol mechanism increases modeled BrO by providing more bromide-rich aerosol surface area for reactive bromine recycling. The snowpack mechanism led to increased model BrO across the Arctic Ocean with maximum production in coastal regions, whereas the blowing snow aerosol mechanism increases BrO in specific areas due to high surface wind speeds. Our uniform snowpack source has a greater impact on BrO mixing ratios than the blowing snow source. Model results best replicate several features of BrO observations during spring 2015 when using both mechanisms in conjunction, adding evidence that these mechanisms are both active during the Arctic spring. Extending our transport model throughout the entire year leads to predictions of enhanced fall BrO that are not supported by observations.

Electrochemical Bromofunctionalization of Alkenes and Alkynes—To Sustainability and Beyond

The electrochemical generation of highly reactive and hazardous bromine under controlled conditions as well as the reduction of surplus oxidizers and reagent waste has placed electrochemical synthesis in a highlighted position. In particular, the electrochemical dibromination and bromofunctionalization of alkenes and alkynes have received significant attention, as the forming of synthetically important derivatives can be generated from bench-stable and safe bromide sources under “green” conditions. Readily available and non-corrosive bromide salts have been utilized with a dual role as both a reagent and supporting electrolyte. However, this trend seems to change with the preparation of organobromine species. In this review, the electrochemical dibromination and bromofunctionalization of alkenes and alkynes was addressed in terms of their bromine sources and sustainability.

Concentration and inorganic elemental analysis of particulate matter in a road tunnel environment (Žilina, Slovakia): Contribution of non-exhaust sources

Particulate matter (PM) is present in the surrounding air. The tunnel environment is no exception, where the PM source is road traffic. In a broader sense, the tunnel can be described as a separate point source of air pollution from which PM pollutants spread to the portal parts and the external environment. PM originates from the exhaust and non-exhaust processes of road traffic (brake wear, tire wear, road surface wear, and road dust re-suspension). This study deals with the specification of non-exhaust PM emissions in a tunnel environment where the primary source is road traffic. PM measurements took place in the “Považský Chlmec” highway tunnel with a length of 2,118 m directly in the tunnel tube and near the tunnel portal. PM measurements were performed using gravimetric and optical methods. PM chemical analyses were performed using energy-dispersive X-ray fluorescence (EDXRF). The concentration of PM in the tunnel was on average: PM10 = 30.76 μg/m3 and PM2.5 = 15.66 μg/m3 and near the tunnel portal PM10 = 14.38 μg/m3 and PM2.5 = 8.74 μg/m3. The average traffic volume in the tunnel tube was 2,274 veh/24 h. Using EDXRF, the main chemical elements Al, Br, Ca, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, P, Si, S, Ti, and Zn were identified in the PM. Chemical element concentrations in PM10 and PM2.5 were subjected to factor analysis (FA) and principal component analysis (PCA) to determine the origin of PM. Two sources were identified for PM10 and three for PM2.5. Absolute principal component scores (APCS) in conjunction with multiple regression analysis (MRA) were used to determine the source contribution to the production of PM10 and PM2.5.

Analysis of the Composition of Bromide Anion Oxidation Products in Aqueous Solutions with Different pH via Rotating Ring-Disk Electrode Method.

We measured the ring collection coefficient of bromide anion oxidation products in a neutral and slightly alkaline medium on a rotating ring-disk electrode (glassy carbon disk, platinum ring) varying the following parameters: disk electrode rotation velocity, sodium bromide concentration, pH of the medium (in the range of 6–12), anode current on the disk, and the electroreduction potential of the bromide anion oxidation products on the ring. The data obtained are presented via dependences of the cathode ring current on the disk current ratio vs. the ring electrode potential. The analysis of the results was carried out by comparing the experimental polarization curves of the ring electrode with the data of cyclic voltammetry in model solutions to determine the electrical activities of various bromine compounds in positive oxidation states. We claim that the RRDE method could be used to obtain quantitative and qualitative data on the electrooxidation of bromide ions in neutral and alkaline solutions. For the most effective regeneration of the spent oxidizer, the values of pH > 10 and moderate concentrations of NaBr should be used.

The SINQ gas-jet facility as a source for radionuclides from neutron-induced fission of 235U

The Swiss Spallation Neutron Source SINQ of the Paul Scherrer Institute provides neutrons via proton-induced spallation reactions in a lead target. Produced neutrons are thermalized and impinge on 235U-targets, enclosed in a three-part chamber assembly, which is located in the inner wall of the SINQ shielding. The thermal-neutron-induced fission products can be readily transported from this chamber assembly to a radiochemical laboratory using the gas-jet technique either with a pure carrier gas or with an aerosol-particle-loaded carrier gas. In the past, mainly radioisotopes of the elements Se, Br, Rb, and Kr were retrieved and used for gas-phase chemistry experiments. Here, we present first experiments after the commissioning of the SINQ gas-jet facility as a source of recoverable, non-volatile and volatile, carrier-free fission products for general radiochemical studies and other applications.

Identification of Toxic Heavy Metals and Trace Elements in Pesticides Used by Shallots <i>(Allium Cepa Var. Aggregatum)</i> Farmers in Brebes District, Indonesia

This study aims to identify the toxic heavy metals and trace elements in pesticides which are suspected to be a source of environmental pollution. The Neutron Activation Analysis method was used to identify and determine the concentration of toxic heavy metals and trace elements in pesticide samples. The pesticides used in this study consist of pesticides that are widely used by onion farmers in Brebes District, Central Java – Indonesia. These pesticides consist of two types (fungicides and insecticides) and in two different forms (solid and liquid). The results indicates that pesticides contain large levels of trace elements (Mg, Ti, Cl, Al, Ca, Br, Na, U, Mn, Br, La, Se, Hg, Rb, Fe, Eu, and Sb), and toxic heavy metals (As, Co, Cr, Ni, Zn, Cu, Hg). Generally, solid pesticides contain higher concentration of elements than liquid pesticides. In addition to releasing organic compounds, pesticides are also proven to be a source of certain trace elements (especially Mn, Br, Ti, Fe, Al) and toxic heavy metals (Cu, Zn, and Cr). They can affect the presence of these elements in the environment. *Corresponding author: sjuari@ugm.ac.id

Spectroelectrochemical and ESR investigation of free radicals derived from indotricarbocyanine dyes for photodynamic therapy

Cyclic voltammetry, UV–Vis absorption spectroscopy, and electron spin resonance are applied to study the properties of indotricarbocyanine dyes and their radicals formed during electrooxidation. We use electrochemistry to generate relatively stable free radicals of the dyes under controlled conditions. The dyes undergo electrooxidation during the chronoamperometric electrolysis at 1.1 V (versus saturated calomel electrode) yielding radical dications. The radicals exhibit an absorption band that is blue-shifted relative to the parent dye (561 nm versus 714 nm). In acetonitrile solutions, the radicals are characterized by a lifetime of ca. 20 min and a g factor of 2.002. The oxidation potential of the dyes is slightly greater than that of bromide ions allowing the radicals of the dyes to interact with bromide ions. The ability of the indotricarbocyanine dyes to sensitize generation of highly reactive bromine radicals might play an important role in their photodynamic activity.

Trace Elements and Mineralogy of Upper Permian (Zechstein) Potash Deposits in Poland

Mineral composition and content analysis of selected trace elements (Ag, As, Ba, Be, Br, Cd, Ce, Co, Cr, Cs, Cu, Ga, I, La, Li, Mn, Mo, Ni, Pb, Rb, Sb, Se, Sn, Sr, Ti, Tl, U, V, and Zn; 308 rock samples) were studied in the Upper Permian (Zechstein) potash-bearing deposits in Poland. They represented K–Mg chlorides of PZ2 and PZ3 cyclothems from four salt domes and stratiform K–Mg sulphates of PZ1 cyclothem. The dominant mineral components of K–Mg sulphates (polyhalite) are anhydrite and polyhalite. The most common minerals of the K–Mg salts of PZ2 cyclothem are halite, sylvite, kieserite, and anhydrite, and the most common of PZ3 cyclothem are halite, carnallite, kieserite, and anhydrite. Most analysed trace elements in the Zechstein potash-bearing deposits show a low content (up to 26 mg/kg) that eliminates them as potential profitable source rocks of such required elements as Ce, Cs, La, Li, or Rb. Common elements, such as Br, Fe, and Sr, are more easily exploited from natural brines, sulphate, and ore deposits.

Towards Selective Removal of Bromide from Drinking Water Resources using Electrochemical Desalination

Disinfection of drinking water is crucial in water treatment as it suppresses waterborne pathogenic diseases. However, as an unintended consequence, disinfection generates disinfection byproducts (DBP). DBPs are cytotoxic, carcinogenic, and nephrotoxic especially when they are brominated. Brominated DBP formation is governed by the interaction of reactive precursors such as natural organic matter (NOM), and Brˉ with oxidants that are added as disinfectants (e.g., chlorine, chloramines, ozone). Historically, the main strategy to control the formation of DBP was to remove NOM from water by coagulation, adsorption, bio-filtration, pre-oxidation, or membrane separation; however, processes that remove NOM do not necessarily remove Brˉ. Herein, we investigated the utilization of combined capacitive and faradaic ion removal in a flow cell to remove Brˉ as well as Clˉ concurrently with more selectivity towards the former. The effectiveness of the proposed technique was evaluated by determining the maximum salt adsorption capacity and measuring the specific ion concentration with ion chromatography. In a binary equimolar mixture of Brˉ and Clˉ, Brˉ was more selectively adsorbed over Clˉ at 1.2 V applied potential due to the contribution of bromine gas evolution to the capacitive deionization.

Understanding the Electrolyte/Electrode Interfacial Interactions for the Development of High-Performance Aqueous Redox-Enhanced Electrochemical Capacitors

Research in electrochemical energy storage is converging to target systems with battery-level energy density, and capacitor-level cycling stability and power density. One approach is to utilize redox-active electrolytes that add faradaic charge storage to increase energy density of supercapacitors. Aqueous redox-active electrolytes are simple to prepare and to up-scale; and, can be synergistically optimized to fully utilize the dynamic charge/discharge and storage properties of micro/mesoporous carbon based electrode systems. However, aqueous redox-enhanced electrochemical capacitors (redox ECs) have performed relatively poorly, primarily due to the cross-diffusion of soluble redox couples, reduced cycle life, and low operating voltages.In this presentation, we show that these challenges can be met by the use of liquid-to-solid phase transitions of redox electrolyte molecules, and their reversible confinement in the pores ( > 2 nm) of high-surface-area electrodes. This approach is demonstrated by the use of bromide catholyte and modified hydrophobic cations (e.g., viologens and tetrabutylammonium) that together induce reversible solid-state complexation of Br2/Br3 –. This mechanism solves the cross-diffusion issue of redox ECs without using costly ion-selective membranes, and has the added benefit of stabilizing the reactive bromine generated during charging.Using the concepts learned from this 1st generation configuration, we further developed high-performance aqueous-based redox ECs by (1) synthesizing differently functionalized/substituted viologen molecules and (2) optimizing the interfacial interactions between the viologens and hierarchically porous-structured carbon electrodes. In the second part of this presentation, we show systematic approaches to explore optimal parameters to improve the energy storage capacity of the device.