Showing papers on "Iodide published in 2017"
TL;DR: Mechanistic insights into oxygen-induced photodegradation of perovskite films are reported, finding fast oxygen diffusion into CH3NH3PbI3 films is accompanied by photo-induced formation of highly reactive superoxide species from oxygen.
Abstract: Methylammonium lead halide perovskites are attracting intense interest as promising materials for next-generation solar cells, but serious issues related to long-term stability need to be addressed. Perovskite films based on CH3NH3PbI3 undergo rapid degradation when exposed to oxygen and light. Here, we report mechanistic insights into this oxygen-induced photodegradation from a range of experimental and computational techniques. We find fast oxygen diffusion into CH3NH3PbI3 films is accompanied by photo-induced formation of highly reactive superoxide species. Perovskite films composed of small crystallites show higher yields of superoxide and lower stability. Ab initio simulations indicate that iodide vacancies are the preferred sites in mediating the photo-induced formation of superoxide species from oxygen. Thin-film passivation with iodide salts is shown to enhance film and device stability. The understanding of degradation phenomena gained from this study is important for the future design and optimization of stable perovskite solar cells.
850 citations
TL;DR: In this paper, the authors showed that I2 vapour causes severe degradation of MAPbI3 (MA: CH3NH3+) perovskite, due to chemical chain reactions.
Abstract: Efficiencies of organic–inorganic lead halide perovskite solar cells (PSCs) have significantly increased in recent years, but instability issues impede their further development and application. Previous studies reported that volatile species (for example, iodine, I2) were generated when perovskites were subjected to moisture, oxygen, light illumination, applied electric field, and thermal stress (all of which are relevant to the operation of PSCs in practical applications). Here we show that I2 vapour causes severe degradation of MAPbI3 (MA: CH3NH3+) perovskite, due to chemical chain reactions. Furthermore, I2 vapour could also induce degradation of other iodide-based perovskites, such as FAPbI3 (FA: HC(NH2)2+) and FA0.8Cs0.2PbI3. The results reveal a universal degradation factor for iodide-based perovskite by I2. As the release of I2 is nearly inevitable during practical applications, this work suggests that MAPbI3 may not be suitable for long-term stable solar cells and it is imperative to develop other types of perovskite material to achieve stable PSCs. Extensive efforts are under way to tackle the degradation issue—one of the biggest challenges for the practical application of perovskite-based solar cells. Here the authors show that CH3NH3PbI3 and several other iodine-containing perovskites are inherently unstable due to decomposition caused by self-generated I2.
446 citations
TL;DR: In this paper, the authors exploit dynamic equilibrium to photocatalytically generate hydrogen from aqueous HI solutions using methylammonium lead iodide, which has been the subject of intensive research efforts in the context of photovoltaic applications.
Abstract: Organometal halide perovskite materials have been the subject of intensive research efforts in the context of photovoltaic applications. Here the authors exploit dynamic equilibrium to photocatalytically generate hydrogen from aqueous HI solutions using methylammonium lead iodide.
380 citations
TL;DR: Iodine ions are unambiguously shown to be the mobile species in CH3NH3PbI3, with iodine vacancies shown to represent the mechanistic centers under equilibrium conditions, and local variations of the iodine stoichiometry may be fast and enable light effects on ion transport.
Abstract: By applying a multitude of experimental techniques including 1 H, 14 N, 207 Pb NMR and 127 I NMR/NQR, tracer diffusion, reaction cell and doping experiments, as well as stoichiometric variation, conductivity, and polarization experiments, iodine ions are unambiguously shown to be the mobile species in CH3 NH3 PbI3 , with iodine vacancies shown to represent the mechanistic centers under equilibrium conditions Pb2+ and CH3 NH3+ ions do not significantly contribute to the long range transport (upper limits for their contributions are given), whereby the latter exhibit substantial local motion The decisive electronic contribution to the mixed conductivity in the experimental window stems from electron holes As holes can be associated with iodine orbitals, local variations of the iodine stoichiometry may be fast and enable light effects on ion transport
230 citations
TL;DR: It is shown that light has a strong influence on the rate of perovskite formation and on film morphology in both of the main deposition methods currently used: sequential deposition and the anti-solvent method.
Abstract: Optimizing the morphology of metal halide perovskite films is an important way to improve the performance of solar cells when these materials are used as light harvesters, because film homogeneity is correlated with photovoltaic performance. Many device architectures and processing techniques have been explored with the aim of achieving high-performance devices, including single-step deposition, sequential deposition and anti-solvent methods. Earlier studies have looked at the influence of reaction conditions on film quality, such as the concentration of the reactants and the reaction temperature. However, the precise mechanism of the reaction and the main factors that govern it are poorly understood. The consequent lack of control is the main reason for the large variability observed in perovskite morphology and the related solar-cell performance. Here we show that light has a strong influence on the rate of perovskite formation and on film morphology in both of the main deposition methods currently used: sequential deposition and the anti-solvent method. We study the reaction of a metal halide (lead iodide) with an organic compound (methylammonium iodide) using confocal laser scanning fluorescence microscopy and scanning electron microscopy. The lead iodide crystallizes before the intercalation of methylammonium iodide commences, producing the methylammonium lead iodide perovskite. We find that the formation of perovskite via such a sequential deposition is much accelerated by light. The influence of light on morphology is reflected in a doubling of solar-cell efficiency. Conversely, using the anti-solvent method to form methyl ammonium lead iodide perovskite in a single step from the same starting materials, we find that the best photovoltaic performance is obtained when films are produced in the dark. The discovery of light-activated crystallization not only identifies a previously unknown source of variability in opto-electronic properties, but also opens up new ways of tuning morphology and structuring perovskites for various applications.
228 citations
191 citations
TL;DR: In this article, a zinc/iodine-bromide battery was proposed to achieve an energy density of 101 W h Lposolyte+negolyte−1, which is the highest energy density achieved for aqueous flow batteries to date.
Abstract: Highly soluble iodide/triiodide (I−/I3−) couples are one of the most promising redox-active species for high-energy-density electrochemical energy storage applications. However, to ensure high reversibility, only two-thirds of the iodide capacity is accessed and one-third of the iodide ions act as a complexing agent to stabilize the iodine (I2), forming I3− (I2I−). Here, we exploit bromide ions (Br−) as a complexing agent to stabilize the iodine, forming iodine–bromide ions (I2Br−), which frees up iodide ions and increases the capacity. Applying this strategy, we demonstrate a novel zinc/iodine–bromide battery to achieve an energy density of 101 W h Lposolyte+negolyte−1 (or 202 W h Lposolyte−1), which is the highest energy density achieved for aqueous flow batteries to date. This strategy can be further generalized to nonaqueous iodide-based batteries (i.e. lithium/polyiodide battery), offering new opportunities to improve high-energy iodide-based energy storage technologies.
190 citations
TL;DR: In this paper, a 2D BA2CPb2I7 (BA = CH3(CH2)3NH3) was proposed for perovskite solar cells, which not only exhibits prominent optoelectronic properties, but also possesses superior structural and compositional stability.
Abstract: Cesium lead iodide perovskite (CsPbI3) has been proposed as an efficient alternative to modify the instability of methylammonium lead iodide (MAPbI3) under thermal and humidity stress. However, three-dimensional (3D) cesium lead iodide forms an undesirable non-perovskite structure with a wide bandgap at ambient atmosphere. Herein, dimension engineering is employed by introducing a bulky ammonium cation to form stable 2D cesium lead iodide perovskite BA2CsPb2I7 (BA = CH3(CH2)3NH3), which not only exhibits prominent optoelectronic properties, but also possesses superior structural and compositional stability to 3D CsPbI3 and MAPbI3 under the pressure of heat and humidity. The current 2D BA2CsPb2I7 shows excellent stability after exposure to 30% relative humidity for 30 days or upon heating at 85 °C for 3 days. In addition, the corresponding BA2CsPb2I7 based planar perovskite solar cells retain 92% of the initial power conversion efficiency (PCE) after aging for over 30 days without any encapsulation, demonstrating the up-scalability of 2D perovskite compounds as stable and efficient light-absorbing materials for perovskite solar cells and other optoelectronic applications.
187 citations
TL;DR: It is shown herein that the metastable state is maintained in the absence of moisture, up to a temperature of 100 °C, and a reversible phase-change enthalpy of 14.2 (±0.5) kJ/mol is observed.
Abstract: The perovskite phase of cesium lead iodide (α-CsPbI3 or “black” phase) possesses favorable optoelectronic properties for photovoltaic applications. However, the stable phase at room temperature is a nonfunctional “yellow” phase (δ-CsPbI3). Black-phase polycrystalline thin films are synthesized above 330 °C and rapidly quenched to room temperature, retaining their phase in a metastable state. Using differential scanning calorimetry, it is shown herein that the metastable state is maintained in the absence of moisture, up to a temperature of 100 °C, and a reversible phase-change enthalpy of 14.2 (±0.5) kJ/mol is observed. The presence of atmospheric moisture hastens the black-to-yellow conversion kinetics without significantly changing the enthalpy of the transition, indicating a catalytic effect, rather than a change in equilibrium due to water adduct formation. These results delineate the conditions for trapping the desired phase and highlight the significant magnitude of the entropic stabilization of thi...
186 citations
TL;DR: The temperature dependence of reorientation of the dipolar molecular cations systematically described here can clarify various hypotheses including those of large-polaron charge transport and fugitive electron spin polarization that have been invoked in the context of these unusual materials.
Abstract: The role of organic molecular cations in the high-performance perovskite photovoltaic absorbers, methylammonium lead iodide (MAPbI3) and formamidinium lead iodide (FAPbI3), has been an enigmatic subject of great interest. Beyond aiding in the ease of processing of thin films for photovoltaic devices, there have been suggestions that many of the remarkable properties of the halide perovskites can be attributed to the dipolar nature and the dynamic behavior of these cations. Here, we establish the dynamics of the molecular cations in FAPbI3 between 4 K and 340 K and the nature of their interaction with the surrounding inorganic cage using a combination of solid state nuclear magnetic resonance and dielectric spectroscopies, neutron scattering, calorimetry, and ab initio calculations. Detailed comparisons with the reported temperature dependence of the dynamics of MAPbI3 are then carried out which reveal the molecular ions in the two different compounds to exhibit very similar rotation rates (≈8 ps) at room ...
127 citations
TL;DR: A visible-light-driven Minisci protocol that employs an inexpensive earth-abundant metal catalyst, decacarbonyldimanganese Mn2 (CO)10 , to generateAlkyl radicals from alkyl iodides has been developed and is demonstrated on the late-stage functionalization of complex nitrogen-containing drugs.
Abstract: A visible-light-driven Minisci protocol that employs an inexpensive earth-abundant metal catalyst, decacarbonyldimanganese Mn2 (CO)10 , to generate alkyl radicals from alkyl iodides has been developed. This Minisci protocol is compatible with a wide array of sensitive functional groups, including oxetanes, sugar moieties, azetidines, tert-butyl carbamates (Boc-group), cyclobutanes, and spirocycles. The robustness of this protocol is demonstrated on the late-stage functionalization of complex nitrogen-containing drugs. Photophysical and DFT studies indicate a light-initiated chain reaction mechanism propagated by . Mn(CO)5 . The rate-limiting step is the iodine abstraction from an alkyl iodide by . Mn(CO)5 .
TL;DR: The results demonstrate the transferability of H-bond parameters for anions between different solvents and different HBD partners, allowing reliable prediction of anion recognition properties in other scenarios.
Abstract: UV/vis absorption titrations have been used to investigate the formation of H-bonded complexes between anionic H-bond acceptors (HBAs) and neutral H-bond donors (HBDs) in organic solvents. Complexes formed by three different HBDs with 15 different anions were studied in chloroform and in acetonitrile. The data were used to determine self-consistent HBA parameters (β) for chloride, bromide, iodide, phosphate diester, acetate, benzoate, perrhenate, nitrate, triflimide, perchlorate, hexafluorophosphate, hydrogen sulfate, methyl sulfonate, triflate, and perfluorobutyl sulfonate. The results demonstrate the transferability of H-bond parameters for anions between different solvents and different HBD partners, allowing reliable prediction of anion recognition properties in other scenarios. Carboxylates are the strongest HBAs studied, with β parameters (≈ 15) that are significantly higher than those of neutral organic HBAs, and the non-coordinating anion hexafluorophosphate is the weakest acceptor, with a β param...
TL;DR: LiI has been revealed to promote the superoxide-related nucleophilic attack toward electrolyte by catalyzing the decomposition of peroxide intermediate, resulting in the accumulation of LiOH and other parasitic products as discussed by the authors.
Abstract: Lithium iodide (LiI) has garnered considerable attention in aprotic Li–O2 batteries. However, the reaction mechanism is still under hot debate and is attracting increasing controversy due to contrasting observations. Herein, on the basis of thorough evidence, a relevant mechanism has been systematically illustrated. LiI has been revealed to promote the superoxide-related nucleophilic attack toward electrolyte by catalyzing the decomposition of peroxide intermediate, resulting in the accumulation of LiOH and other parasitic products. Also, they refuse to be oxidized by not only triiodide (I3–) but also iodine (I2), resulting in inevitable degradation. However, as a proton-donor, water can buffer the superoxide-related nucleophilic attack by reducing it to moderate hydroperoxide (HO2–). More importantly, the catalysis of iodide toward speroxide is restrained with the increase of alkalinity in water-contained electrolyte, resulting in the formation of Li2O2. Turning LiOH into Li2O2, the newly proposed mechan...
TL;DR: In this paper, the role of lithium iodide on reduction product chemistry under two conditions: mixing KO2 with lithium salts and discharging Li-O2 batteries at high and low overpotential, in the presence of an ether-based electrolyte with different ratios of H2O':'LiI'.
Abstract: Lithium iodide has been studied extensively as a redox-mediator to reduce the charging overpotential of Li–oxygen (Li–O2) batteries. Ambiguities exist regarding the influence of lithium iodide on the reaction product chemistry and performance of lithium–oxygen batteries. In this work, we examined the role of lithium iodide on the reduction product chemistry under two conditions: (i) mixing KO2 with lithium salts and (ii) discharging Li–oxygen batteries at high and low overpotentials, in the presence of an ether-based electrolyte with different ratios of H2O : LiI. The addition of iodide to electrolytes containing water was found to promote the formation of LiOOH·H2O, LiOH·H2O and LiOH at the expense of Li2O2. At low H2O : LiI ratios (lower than 5), LiOH instead of Li2O2 was formed, which was accompanied by the oxidation of iodide to triodide while at high H2O : LiI ratios (12, 24, 134), a mixture of Li2O2, LiOOH·H2O and LiOH·H2O was observed and no triiodide was detected. The reaction between peroxide Li2O2 and/or superoxide LiO2 with H2O to form LiOH is facilitated by increased water acidity by strong I−–H2O interactions as revealed by 1H NMR and FT-IR measurements. This mechanism of LiOH formation in the presence of LiI and H2O was also found upon Li–O2 cell discharge, which is critical to consider when developing LiI as a redox mediator for Li–O2 batteries.
TL;DR: In this article, transient terahertz spectroscopy is applied to solution-processed, all-inorganic, perovskite-phase cesium lead iodide (CsPbI3) thin films, which lack such a dipole.
Abstract: Hybrid organic/inorganic lead iodide perovskites of the formula APbI3, where A is a molecular cation such as methylammonium, exhibit remarkably slow photoinduced charge carrier recombination rates, for reasons that remain uncertain. Prevalent hypotheses credit this behavior to the unique dipolar nature of the molecular cation. Herein, transient terahertz spectroscopy is applied to solution-processed, all-inorganic, perovskite-phase cesium lead iodide (CsPbI3) thin films, which lack such a dipole. The recombination kinetics are studied as a function of the initial photoinduced carrier concentration and the wavelength of excitation. A kinetic model combining diffusion and recombination is fit to the data, from which the rate constants are determined, revealing a bimolecular recombination rate of 10–10 cm3 s–1, comparable to high-quality, single-crystal, direct-gap semiconductors. This rate, as well as a charge carrier mobility > 30 cm2 V–1 s–1 measured herein for CsPbI3, are similar to values reported for t...
TL;DR: The relative enhancement in the presence of HA in the photodegradation of PFOS can be attributed to several factors: a) HA enhances the effective generation of eaq- due to the reduction of I2, HOI, IO3- and I3- back to I-; b) certain functional groups of HA enhance the electron transfer efficiency as electron shuttles; c) a weakly-bonded association of I- and PFOS with HA increases the reaction probability.
TL;DR: The results demonstrate that the Cu content and morphology of samples can be tuned by the adding amount of ammonia, and Cu/Cu2O hybrids showed excellent selectivity for I- anions in the presence of large concentrations of competitive anions such as SO42- and NO3- and could work in an acidic and neutral environment.
TL;DR: In this paper, the routes and kinetics of the degradation of thin films of methylammonium (MA)/formamidinium (FA) lead iodide perovskites (MA1−xFAxPbI3, 0 ≤ x ≤ 1) under dry atmospheric conditions have been investigated.
Abstract: The routes and kinetics of the degradation of thin films of methylammonium (MA)/formamidinium (FA) lead iodide perovskites (MA1−xFAxPbI3, 0 ≤ x ≤ 1) under dry atmospheric conditions have been investigated. MA-rich phases decompose to the precursor iodide salts and PbI2, while FA-rich phases convert mainly to the yellow hexagonal phase. The reactivity is strongly inhibited for mixed cation phases of MA1−xFAxPbI3, for x = 0.4 to 0.6, where the decomposition routes available to end member phases become less favourable. It is shown that for pristine films with x = 0.6, PbI2 formation can be completely suppressed for up to 10 days. Kinetic analysis reveals that the rate of PbI2 formation decays exponentially with increasing FA content until x = 0.7, beyond which the FA containing perovskite transforms rapidly to the hexagonal phase. Ab initio simulations of the decomposition reaction energies fully support the increased kinetic stability found experimentally for the mixed A-cation perovskites.
TL;DR: A synthetic ion channel developed from a shape-persistent porphyrin-based covalent organic cage appears to facilitate iodide transport across the membrane of a living cell, suggesting that the cage could be useful as a biological tool that may replace defective iodide channels in living systems.
Abstract: We report here a synthetic ion channel developed from a shape-persistent porphyrin-based covalent organic cage The cage was synthesized by employing a synthetically economical dynamic covalent chemistry (DCC) approach The organic cage selectively transports biologically relevant iodide ions over other inorganic anions by a dehydration-driven, channel mechanism as evidenced by vesicle-based fluorescence assays and planar lipid bilayer-based single channel recordings Furthermore, the organic cage appears to facilitate iodide transport across the membrane of a living cell, suggesting that the cage could be useful as a biological tool that may replace defective iodide channels in living systems
TL;DR: In this article, a solution-based strategy for doping colloidal quantum dots with iodide to further optimize solar cell performance was proposed, and the optimum precursor I/Pb ratio was found to be in the 1.5-3% range at which iodide substituted S without excessively altering the dots' surface chemistry.
Abstract: Surface passivation of PbS colloidal quantum dots (QDs) with iodide has been used in highly efficient solar cells. Iodide passivation is typically achieved by ligand-exchange processes on QD films. Complementary to this approach, herein we present a nonintrusive solution-based strategy for doping QDs with iodide to further optimize solar cell performance. The doping step is applied in situ at the end of the synthesis of the QDs. The optimum precursor I/Pb ratio is found to be in the 1.5–3% range at which iodide substitutes S without excessively altering the dots’ surface chemistry. This allows for band engineering and decreasing the density of deep trap states of the QDs, which taken together lead to PbS QD solar cells with efficiency in excess of 10%.
TL;DR: In this article, the local structure present in single-step precursor solutions of methylammonium lead iodide (MAPbI3) perovskite as a function of organic and inorganic precursor ratio, as well as with hydriodic acid (HI).
Abstract: Here we investigate the local structure present in single-step precursor solutions of methylammonium lead iodide (MAPbI3) perovskite as a function of organic and inorganic precursor ratio, as well as with hydriodic acid (HI), using X-ray absorption spectroscopy. An excess of organic precursor as well as the use of HI as a processing additive has been shown to lead to the formation of smooth, continuous, pinhole free MAPbI3 films, whereas films produced from precursor solutions containing molar equivalents of methylammonium iodide (MAI) and PbI2 lead to the formation of a discontinuous, needlelike morphology. We now show that as the amount of excess MAI in the precursor solution is increased, the iodide coordination of iodoplumbate complexes present in solution increases. The use of HI results in a similar increase in iodide coordination. We therefore offer insight into how solution chemistry can be used to control MAPbI3 thin film morphology by revealing a strong correlation between the lead coordination ...
TL;DR: Near-ambient-pressure X-ray photoelectron spectroscopy enables the study of the reaction of in situ-prepared methylammonium lead iodide (MAPI) perovskite at realistic water vapour pressures for the first time.
TL;DR: It is shown that iodide ions in the methylammonium lead iodide migrate via interstitial sites at temperatures above 280 K, which coincides with temperature dependent static distortions resulting in pseudocubic local symmetry.
Abstract: Hybrid perovskites form an emerging family of exceptional light harvesting compounds. However, the mechanism underpinning their photovoltaic effect is still far from understood, which is impeded by a lack of clarity on their structures. Here we show that iodide ions in the methylammonium lead iodide migrate via interstitial sites at temperatures above 280 K. This coincides with temperature dependent static distortions resulting in pseudocubic local symmetry. Based on bond distance analysis, the migrating and distorted iodines are at lengths consistent with the formation of I2 molecules, suggesting a 2I−→I2+2e− redox couple. The actual formula of this compound is thus (CH3NH3)PbI3−2x(I2)x where x∼0.007 at room temperature. A crucial feature of the tetragonal structure is that the methylammonium ions do not sit centrally in the A-site cavity, but disordered around two off-centre orientations that facilitate the interstitial ion migration via a gate opening mechanism. The mechanism underpinning the photovoltaic effect in hybrid perovskite solar cells has remained unclear. Here, Green and co-workers suggest that iodide ions in methylammonium lead iodide perovskite migrate via interstitial sites and undergo a redox reaction to form molecular iodine and free electrons.
TL;DR: An innovative AOP using a combination of peroxymonosulfate (PMS) and iodide ions (I-) for the selective removal of phenolic pollutants from aqueous solutions is developed and evidence that iodide atoms were the dominant oxidants is found.
Abstract: The development of environmentally friendly, oxidation-selective advanced oxidation processes (AOPs) for water decontamination is important for resource recovery, carbon dioxide abatement, and cost savings. In this study, we developed an innovative AOP using a combination of peroxymonosulfate (PMS) and iodide ions (I–) for the selective removal of phenolic pollutants from aqueous solutions. The results showed that nearly 100% degradation of phenol, bisphenol A, and hydroquinone was achieved after reaction for 4 min in the presence of 65 μM PMS and 50 μM I–. PMS-I– oxidation had a wide effective pH range, with the best performance achieved under circumneutral conditions. The ratio between [PMS] and [I–] influenced the degradation, and the optimal ratio was approximately 1.00 for the degradation of the phenols. Neither sulfate nor hydroxyl radicals were found to be the active species in PMS-I– oxidation. Instead, we found evidence that iodide atoms were the dominant oxidants. In addition, both Cl– and Br– a...
TL;DR: A palladium-catalyzed fluorosulfonylvinylation reaction of organic iodides is described, demonstrated in the successful syntheses of eighty-eight otherwise difficult to access compounds, in up to 99 % yields, including the unprecedented 2-heteroarylethenesulfonyl fluorides and 1,3-dienylsulfonyL fluorides.
Abstract: A palladium-catalyzed fluorosulfonylvinylation reaction of organic iodides is described. Catalytic Pd(OAc)2 with a stoichiometric amount of silver(I) trifluoroacetate enables the coupling process between either an (hetero)aryl or alkenyl iodide with ethenesulfonyl fluoride (ESF). The method is demonstrated in the successful syntheses of eighty-eight otherwise difficult to access compounds, in up to 99 % yields, including the unprecedented 2-heteroarylethenesulfonyl fluorides and 1,3-dienylsulfonyl fluorides.
TL;DR: The addition of iodide has been shown to improve the performance of aPDT in several animal models of localized infection, and KI is non-toxic and is an approved drug for antifungal therapy, so its transition to clinical use in aPDt should be straightforward.
Abstract: Introduction: Antimicrobial photodynamic inactivation (aPDI) involves the use of non-toxic dyes excited with visible light to produce reactive oxygen species (ROS) that can destroy all classes of microorganisms including bacteria, fungi, parasites, and viruses. Selectivity of killing microbes over host mammalian cells allows this approach (antimicrobial photodynamic therapy, aPDT) to be used in vivo as an alternative therapeutic approach for localized infections especially those that are drug-resistant.Areas covered: We have discovered that aPDI can be potentiated (up to 6 logs of extra killing) by the addition of simple inorganic salts. The most powerful and versatile salt is potassium iodide, but potassium bromide, sodium thiocyanate, sodium azide and sodium nitrite also show potentiation. The mechanism of potentiation with iodide is likely to be singlet oxygen addition to iodide to form iodine radicals, hydrogen peroxide and molecular iodine. Another mechanism involves two-electron oxidation of...
TL;DR: The results demonstrate the potential risk of producing toxic iodinated organic compounds in the novel PDS/CNT oxidation process developed very recently, which should be taken into consideration before its practical application in water treatment.
Abstract: In this study, we interestingly found that peroxydisulfate (PDS) could be activated by a commercial multiwalled carbon nanotube (CNT) material via a nonradical pathway. Iodide (I–) was quickly and almost completely oxidized to hypoiodous acid (HOI) in the PDS/CNT system over the pH range of 5–9, but the further transformation to iodate (IO3–) was negligible. A kinetic model was proposed, which involved the formation of reactive PDS-CNT complexes, and then their decomposition into sulfate anion (SO42–) via inner electron transfer within the complexes or by competitively reacting with I–. Several influencing factors (e.g., PDS and CNT dosages, and solution pH) on I– oxidation kinetics by this system were evaluated. Humic acid (HA) decreased the oxidation kinetics of I–, probably resulting from its inhibitory effect on the interaction between PDS and CNT to form the reactive complexes. Moreover, adsordable organic iodine compounds (AOI) as well as specific iodoform and iodoacetic acid were appreciably produc...
TL;DR: In this paper, a hybrid energy storage system combining zinc iodide (ZnI2) as redox electrolyte with a nanoporous activated carbon fiber (ACF) cathode and a zinc disk anode was introduced.
Abstract: A key challenge for present-day electric energy storage systems, such as supercapacitors and batteries, is to meet the world's growing demand for high performances, low cost, and environmental-friendliness Here, we introduce a hybrid energy storage system combining zinc iodide (ZnI2) as redox electrolyte with a nanoporous activated carbon fiber (ACF) cathode and a zinc disk anode We found that the nanopores (<1 nm) of ACF lead to a strong adsorption behavior of iodide and triiodide Hence, this system exhibits low self-discharge rates without applying an ion exchange membrane The high power performance (200 kW kg−1) originates from the enhanced redox kinetics of the iodide system as evidenced by electrochemical analysis Considering the high specific energy (226 W h kg−1), the ACF/Zn ZnI2 battery represents an alternative for lead acid, Ni–Zn, and Ni–Cd batteries, while providing a supercapacitor-like power performance in the range of seconds to minutes charging times
TL;DR: Speciation analysis and geochemical modeling results indicate that fluoride complexes in groundwater are dominated by free fluoride, the negative charge of which favors fluoride enrichment in groundwater under basic conditions, and iodide, iodate and organic iodine co-occur in groundwater at NCP with iodide as the dominant species.
TL;DR: A novel fluorescent and colorimetric platform for simple and selective detection of iodide ions based on the DNA-templated gold/silver nanoclusters (DNA-Au/Ag NCs) which shows an obvious fluorescence quenching with the addition of iodid ions and a good linear range from 0 to 10μmol/L for iodine ions.