I3 Ions Research Articles

Ultralong Cycle Life and High Rate of Zn‖I2 Battery Enabled by MBene‐Hosted I2 Cathode

AbstractHigh rate tolerance and long cycle life represent the critical demand of the market for energy storage devices, known as one of major challenges for the development of rechargeable aqueous batteries. Herein, a layered Mo4/3B2T2 (where “T” denotes ‐O, ‐OH, and ‐F terminations) MBene (a transition metal boride) with in‐plane ordered metal vacancies is first proposed as an iodine species host of an aqueous Zn‖I2 battery, delivering a discharge capacity of 106.8 mAh g−1 at 25 A g−1 after 230 000 cycles and 80 mAh g−1 at 100 A g−1, far exceeding those of all Zn‖I2 batteries ever reported. The high performance is attributed to the strong affinity with iodine species and accelerated the redox kinetics by the conductive MBene with metal vacancies, as evidenced by the one‐step conversion of I‒/I0 without the generation of I3‒ ions. This work unlocks a new route for the construction of other halide or sulfur electrode batteries with superior durability and kinetics.

Enhanced sunlight harvesting of dye-sensitized solar cells through the insertion of a (Sr, Ba, Eu)2SiO4-TiO2 composite layer

TiO2 nanoparticle-based dye-sensitized solar cells (DSSCs) were modified by inserting a composite layer of (Sr, Ba, Eu)2SiO4-TiO2 on top or at bottom of the transparent layer, so as to enhance their sunlight harvesting capability. Due to the presence of the (Sr, Ba, Eu)2SiO4 phosphor layer, absorption band of the photoanodes was shifted from violet region to the active photoabsorption region of the dye N719 used in the DSSCs. Power conversion efficiency of the devices showed that the introduction of such phosphor significantly enhanced light harvesting capability of the DSSCs. The electrons which are produced by the (Sr, Ba, Eu)2SiO4 particles, reduced I3⿿ to I⿿, so that the concentration of I3⿿ was at a lower level in the electrolyte. As a result, the number of electrons injected into the TiO2 conduction band (CB) by I3⿿ ions was decreased. Under one sun illumination (AM 1.5G, 100mWcm⿿2), the devices with the insertion of the (Sr, Ba, Eu)2SiO4-TiO2 composite layer showed an optimal power conversion efficiency of 5.97%, which was increased by 23.34% as compared with that (4.84%) of the devices without the composite layer. The introduction of down-conversion phosphors into DSSCs is an effective approach to improve their performances.

A simple and sensitive fluorescence method for the determination of trace ozone in air using acridine red as a probe.

The ozone in an air sample was trapped by H3 BO3 -LK solution to produce iodine (I2) that interacted with excess I(-) to form I3(-). In pH 4.0 acetate buffer solutions, the I3(-) reacted with acridine red to form acridine red-I3 ion association particles that resulted in the fluorescence peak decreased at 553 nm. The decreased value ΔF553 nm is linear to the O3 concentration in the range 0.08-53.3 × 10(-6) mol/L, with a detection limit of 4 × 10(-8) mol/L. This fluorescence method was used to determine ozone in air samples, and the results were in agreement with that of indigo carmine spectrophotometry.

Facile iodination of aromatic compounds having electron-withdrawing substituents. Generation of triiodine cation in the system tetra-N-iodoglycoluril-iodine-sulfuric acid

In the middle of the past century several methods for the generation of I3 ion by reaction of iodine with oxidants in oleum or sulfuric acid were proposed and studied [1, 2]. It was shown that triodine cation in solution exhibits enhanced electrophilicity and that they are capable of iodinating benzene derivatives having electron-withdrawing substituents [3, 4]. On the basis of spectral data and quantum-chemical calculations we previously presumed [5–9] that dissolution of N-iodo imides in sulfuric acid could give rise to triodine cation I3 together with iodine(I) hydrogen sulfate (IOSO3H). With a view to get additional support to the above assumption we made an attempt to obtain a solution of I3 by reaction of tetra-N-iodoglycoluril (I, 1,3,4,6-tetraiodoperhydroimidazo[4,5-d]imidazole-2,5-dione) with iodine in sulfuric acid. As a result, we have developed an effective alternative way for the generation of I3. A solution containing I3 is readily formed by gradually adding compound I to a suspension of finely ground iodine in sulfuric acid (d = 1.815–1.834 g/cm) under stirring at 0–3°C (Scheme 1).

The diffuse X-ray scattering and the structure of the iodine chains in bis(1,2-benzoquinonedioximato)2nickel.0.5I[Ni(BCD)2.0.5I

Diffuse X-ray scattering from the title compound, containing linear iodine chains, indicates the formation of I3 ions. These anions are disordered from their averaged positions. The oxidation number of the Ni atoms in this mixed-valence one-dimensional solid is 2.17.

Nuclear quadrupole resonance of iodine in some polyiodides

The nuclear quadrupole resonance of iodine in a variety of alkylammonium triiodides, thallium(I) triiodide, and cesium octaiodide was observed at various temperatures. Observed frequencies were assigned to v, and v2, and the number of nonequivalent iodine sites in crystals was evaluated. In general, cations having a large size favor the symmetric structure of 13- ions, whereas triiodides having small cations form crystals containing anions of an asymmetric structure. However, the cationic size is not a single factor determining the geometry of I 3 − ions: the arrangement of ions surrounding an I3 ion is involved as well. Charge distribution in I 3 − and I 8 −2 ions was calculated. Tetramethylammonium triiodide and thallium(I) triiodide give rise to resonance lines having a positive temperature coefficient of resonance frequencies.

The vibrational spectra and structure of the Bis(hexamethylenetetramine)iodine(I) cation

The crystalline compound reported in the literature as the 1 : 1 addition complex of hexamethylenetetramine (hx) with iodine is shown by means of i.r. and Raman spectroscopy to be an ionic compound consisting of bis(hexamethyl-enetetramine)iodine(I) ions, (hx)2I+, and I3- ions. A crystalline compound consisting of molecules of the true 1 : 1 addition complex (hx)I2 does exist, however, and its preparation is described. On standing, this compound undergoes an unusual solid state transformation, resulting in the formation of the ionic complex. The (hx)2I+ ion is the first documented example of a bis(amine)halogen(I) ion involving an amine other than pyridine or its derivatives. A structure for this ion is proposed in which the hexamethylenetetramine molecules are bound to the iodine atom through one of their nitrogen atoms, the resulting N...I...N arrangement being linear, centrosymmetric, and lying along the threefold axis passing through the coordinated nitrogen atom of each hexamethylenetetramine molecule. The evidence for this structure obtainable from the vibrational spectra of the ion is discussed. A preliminary investigation of the valence force field indicates unusually strong nitrogen-iodine bonding in this ion. The literature method for preparing bis-(pyridine)halogen(I) perchlorates has been modified and used to prepare the perchlorate of bis(hexamethylenetetramine)iodine(I).

Nuclear quadrupole resonance of charge transfer complexes. I. The trihalide ions

The nuclear quadrupole resonance frequencies of the halogen atoms in the trihalide ions 13 and Ibr2 in some of their crystalline salts have been measured. The results have been correlated with a simple LOAD-MO bonding description and the charge distributions in the ions have been calculated. These ions can be regarded as charge-transfer complexes as described by Mulliken. The effect of the crystal field on the charge distribution in the I3 ion has been investigated.