Reaction Characteristics of Polysaccharide-Iodine Complexes: A Mini-review

The potential reactions between natural polysaccharides and iodine and their products have been explored for a long time. Due to the complex factors that can influence these reactions, a clear-cut mechanism has not yet been developed. Starch-iodine complexes, especially the amylose-iodine complex, are the most investigated of the polysaccharide-iodine reactions, and the study of this reaction can be used as a basis for the investigation of other polysaccharide-iodine reactions. In this paper, significant aspects of the reaction were introduced, including the influence of the polysaccharide structure on the properties of the resulting complexes, the relationship between the concentration of CaCl_2 and formation of the final products, as well as the form of the polyiodides in these complexes. The interior structure and the surface morphology of the complexes were discussed, along with the progress in research related to this reaction.     

Raman scattering studies of the condensed phase of the HIx feed of the sulfur–iodine thermochemical cycle

The species present in the condensed phase of the HI_x, hydrogen producing, feed in the water‐splitting, sulfur–iodine thermochemical cycle have been investigated using spontaneous Raman scattering. Measurements of I₂‐containing species in the low Raman‐shift region from 50 to 400 cm^?1 in samples of the two aqueous binary systems, I₂/H₂O and HI/H₂O, and the ternary system HI/I₂/H₂O with and without the addition of H₂SO₄ have provided a consistent picture of the aqueous iodine and polyiodide chemistry. Samples were contained in sealed silica ampoules and were heated to temperatures in the range 20–300°C. The results, which cover a wide range of I₂ and HI mole fractions, and x/x_HI mole ratios, in the HI/I₂/H₂O system, reveal the co‐occurrence of H⁺I, H⁺–I^?(I₂), and H⁺–I^?(I₂)₂ solvated species in the condensed phase of HI_x. Thus, while the first is mostly evident by its strong fundamental band with Raman shift in the range from 110 to 115 cm^?1, the other two species appear convoluted in a broad prominent band whose Raman shift ranges between 153 and 172 cm^?1 depending on the x/x_HI mole ratio. These well characterized Raman features are proposed as an in situ diagnostic for process control of the cycle. Copyright © 2010 John Wiley & Sons, Ltd.     

Efficient Charge Storage in Zinc–Iodine Batteries based on Pre-Embedded Iodine-Ions with Reduced Electrochemical Reaction Barrier and Suppression of Polyiodide Self-Shuttle Effect

Aqueous zinc Iodine batteries are considered as a promising energy storage system due to their high energy/power density, and safety. However, polyiodide shuttling leads to severe active mass loss, which results in lower Coulombic efficiency and limits the cyclic life. Herein, a novel structure-limiting strategy to pre-embed iodide ions into Prussian blue (PBI) is proposed. The DFT calculations and electrochemical characterization reveal that the formation of Ferrum Iodine bond reduces the electrochemical reaction energy barrier of subsequent iodide-ions at the pre-embedding sites, improves the I⁻ oxidation reaction kinetic process, and suppresses the polyiodide self-shuttle. The PBI//Zn batteries exhibit a low Tafel slope (155 mV dec⁻¹). Moreover, UV–vis spectroscopy confirms that the proposed strategy suppresses the polyiodide self-shuttle. As a result, the PBI//Zn battery achieves high iodide utilization and Coulomb efficiency (242 mAh g⁻¹ at 0.2 A g⁻¹, CEs ≈ 100%), as well as high multiplicity performance of 197.2 mAh g⁻¹ even at 10 A g⁻¹(82% of initial capacity). The PBI//Zn battery also renders excellent cyclic stability with a capacity retention of 94% at 4 A g⁻¹ after 1500 cycles. The device exhibits a high energy density of 142 W h kg⁻¹ at a power density of 5538 W kg⁻¹.