12136-49-1Relevant articles and documents
Reactions in molten alkalimetal polychalcogenides: What happens in the melt? A study of the reactions in the system K-Nb-S using differential scanning calorimetry, infrared spectroscopy, and X-ray powder diffraction
Dürichen, Peter,Bensch, Wolfgang
, p. 1382 - 1386 (2002)
The reactions of potassium polysulfides with elemental Nb were investigated with different analytical techniques. The amount of the polysulfide applied has no influence onto product formation, i. e. the ratio K2Sx: Nb is not important. The length of the polsysulfide chain, i. e. the value of x in K2Sx determines what product is formed. In sulfur-poor melts, K3NbS4 is observed. Increasing x to 5-6, K4Nb2S11 is formed with a structure containing S22- anions. Finally, applying a melt with x > 6, K6Nb4S25 is found as the product with a crystal structure containing the S52- polysulfide anion. When K2Sx (x 2S5 is formed. Immediately after melting of K2S5 a reaction with elemental Nb occurs. The results of FT-IR and X-ray investigations have demonstrated that after oxidation the anion [Nb2S11]4- is formed relatively fast, and after a short time crystalline K4Nb2S11 can be detected. After 24 h the reaction is complete.
Understanding fluxes as media for directed synthesis: In situ local structure of molten potassium polysulfides
Shoemaker, Daniel P.,Chung, Duck Young,Mitchell,Bray, Travis H.,Soderholm,Chupas, Peter J.,Kanatzidis, Mercouri G.
, p. 9456 - 9463 (2012)
Rational exploratory synthesis of new materials requires routes to discover novel phases and systematic methods to tailor their structures and properties. Synthetic reactions in molten fluxes have proven to be an excellent route to new inorganic materials because they promote diffusion and can serve as an additional reactant, but little is known about the mechanisms of compound formation, crystal precipitation, or behavior of fluxes themselves at conditions relevant to synthesis. In this study we examine the properties of a salt flux system that has proven extremely fertile for growth of new materials: the potassium polysulfides spanning K2S3 and K 2S5, which melt between 302 and 206 °C. We present in situ Raman spectroscopy of melts between K2S3 and K 2S5 and find strong coupling between n in K 2Sn and the molten local structure, implying that the Sn2- chains in the crystalline state are mirrored in the melt. In any reactive flux system, K2Sn included, a signature of changing species in the melt implies that their evolution during a reaction can be characterized and eventually controlled for selective formation of compounds. We use in situ X-ray total scattering to obtain the pair distribution function of molten K2S5 and model the length of Sn2- chains in the melt using reverse Monte Carlo simulations. Combining in situ Raman and total scattering provides a path to understanding the behavior of reactive media and should be broadly applied for more informed, targeted synthesis of compounds in a wide variety of inorganic fluxes.
Syntheses and Crystal Structures of New Quaternary Ag-Containing Group 5 Chalcogenides: KAg2MVSe4 and K 3Ag3MV2S8 (MV = Nb, Ta)
Chen, Wen-Tong,Ma, Hong-Wei,Guo, Guo-Cong,Deng, Lei,Zhou, Guo-Wei,Dong, Zhen-Chao,Huang, Jin-Shun
, p. 505 - 509 (2004)
Four new quaternary Ag-containing group 5 chalcogenides, KAg 2NbSe4 (1), KAg2TaSe4 (2), K 3Ag3Nb2S8 (3), and K 3Ag3Ta2S8 (4), have been prepared through the use of molten alkali metal polychalcogenides as reactive fluxes and structurally characterized by single-crystal X-ray diffraction techniques. The layer-type structures of 1 and 2 can be regarded as constructed from the basic building block of the incomplete cubane [Ag3MVSe 3], which are corner-shared to form an infinite chain along the a direction. These incomplete cubane chains are interconnected and further bridged by Se atoms along the c direction, leading to a two-dimensional structure. The crystal structure of 3 and 4 consists of one-dimensional triple-metal [Ag3MV2S8] 3- anionic chains seperated by K+ cations. The alternate packing of MVS4 and AgS4 tetrahedra via edge-sharing along the b direction leads to mixed-metal sub-chains, every two of which are further linked by AgS4 tetrahedra along the a direction through edge-sharing to the MVS4 tetrahedra, thus yielding the so-called triple-metal chains.
Polysulfide chalcogels with ion-exchange properties and highly efficient mercury vapor sorption
Oh, Youngtak,Morris, Collin D.,Kanatzidis, Mercouri G.
, p. 14604 - 14608 (2012)
We report the synthesis of metal-chalcogenide aerogels from Pt2+ and polysulfide clusters ([Sx]2-, x = 3-6). The cross-linking reaction of these ionic building blocks in formamide solution results in spontaneous gelation and eventually forms a monolithic dark brown gel. The wet gel is transformed into a highly porous aerogel by solvent exchanging and subsequent supercritical drying with CO2. The resulting platinum polysulfide aerogels possess a highly porous and amorphous structure with an intact polysulfide backbone. These chalcogels feature an anionic network that is charged balanced with potassium cations, and hosts highly accessible S-S bonding sites, which allows for reversible cation exchange and mercury vapor capture that is superior to any known material.
Aluminum anodic behavior in aqueous sulfur electrolytes
Licht, Stuart,Jeitler, James R.,Hwang, Jin H.
, p. 4959 - 4965 (1997)
We report on an unexpected domain of high Coulombic efficiency for electrochemical oxidation of aluminum in aqueous polysulfide solutions at high current density for the process: Al + 3OH- → Al(OH)3 + 3e-. This high-efficiency domain, of importance to battery processes, includes aluminum oxidation in a wide range of solutions containing concentrated dissolved zerovalent sulfur. As expected at lower concentrations of dissolved sulfur, aluminum electrochemical oxidation is inefficient, due to various exothermic parasitic reactions, including: Al(c) + ySx2-(aq) + yH2O(1) ? 1/2Al2S3(C) + yOH-(aq) + yHS-(aq), y = 1.5/(x - 1), and Al(c) + 1.5S22-(aq) + 3H2O(1) ? Al(OH)3(amorph) + 3HS-(aq). However, at high polysulfide and sulfur concentrations, the Coulombic efficiency can approach 100%. This domain of high efficiency is correlated to an observed cathodic shift with increasing sulfur concentration, leading to improved chemical passivation at the aluminum surface.
Energetics of a zinc-sulfur fuel cell
Bendikov, Tatyana A.,Yarnitzky, Chaim,Licht, Stuart
, p. 2989 - 2995 (2002)
Energetics of a novel zinc-sulfur charge storage (generalized as Zn + S a?? ZnS) is explored to access the high (> 1000 Ah/kg) charge capacity of sulfur. At 25 ?°C, the theoretical energy density of the complete Zn/S system is a high 572 Wh/kg, at E?
Highly efficient iodine capture by layered double hydroxides intercalated with polysulfides
Ma, Shulan,Islam, Saiful M.,Shim, Yurina,Gu, Qingyang,Wang, Pengli,Li, Hao,Sun, Genban,Yang, Xiaojing,Kanatzidis, Mercouri G.
, p. 7114 - 7123 (2014)
We demonstrate strong iodine (I2) vapor adsorption using Mg/Al layered double hydroxide (MgAl-LDH) nanocomposites intercalated with polysulfide (Sx2-) groups (Sx-LDH, x = 2, 4, 6). The as-prepared LDH/polysulfide hybrid materials display highly efficient iodine capture resulting from the reducing property of the intercalated polysulfides. During adsorption, the I2 molecules are reduced to I3- anions by the intercalated [Sx]2- groups that simultaneously are oxidized to form S8. In addition to the chemical adsorption, additional molecular I2 is physically captured by the LDH composites. As a result of these parallel processes, and despite their very low BET surface areas, the iodine capture capacities of S2-LDH, S4-LDH, and S6-LDH are 1.32, 1.52, and 1.43 g/g, respectively, with a maximum adsorption of 152% (wt %). Thermogravimetric and differential thermal analysis (TG-DTA), energy dispersive X-ray spectroscopy (EDS), and temperature-variable powder X-ray diffraction (XRD) measurements show the resulting I3- ions that intercalated into the LDH gallery have high thermal stability (￥350 °C). The excellent iodine adsorption performance combined with the facile preparation points to the Sx-LDH systems as potential superior materials for adsorption of radioactive iodine, a waste product of the nuclear power industry.
Synthesis and crystal structures of K2CuVS4 and K3VS4: First examples of ternary and quaternary vanadium sulfides prepared via the molten flux method
Duerichen,Bensch
, p. 309 - 320 (2008/10/08)
The ternary potassium vanadium sulfide K3VS4 and the new quaternary compound K2CuVS4 were prepared at low temperatures via the molten flux method. K2CuVS4 is isostructural with the analoguous niobium and tantalum selenides. Infinite chains of edge-sharing copper and vanadium-centered tetrahedra are running parallel to the [100] direction. The chains are separated by K+ ions. The Cu and V atoms occupy the tetrahedra in an ordered fashion. The Cu-V interatomic separation of 2.719 A is indicative of no significant metal to metal bonding interaction. Originally K3VS4 was synthesized at 800°C. This compound can also be prepared at temperatures as low as 270°C via the reactive flux method. Gauthier-Villars.
Syntheses and characterization of the new homoleptic indium-polysulfide complexes [In2S27]4-, [In2S14]2-, and [In2S16]2-
Dhingra, Sandeep S.,Kanatzidis, Mercouri G.
, p. 3300 - 3305 (2008/10/08)
The reaction of InCl3 with K2S5 and Ph4PCl in a 2:5:4 mole ratio in DMF afforded thin pale yellow crystals of (Ph4P)4[In2S27] (I). I crystallizes in the triclinic space group P1 (No. 2) with a = 12.276(3) ?, b = 21.849(8) ?, c = 10.852(2) ?, α = 99.57(2)°, β = 112.44(2)°, γ = 79.28(3)°, V = 2628(1) ?3 (at -90°C), and Z = 1. The [In2(S4)2(S6)2(S 7)]4- anion consists of In3+ centers in trigonal bipyramidal coordination. Each In atom is chelated by two bidentate polysulfide S42- and S62- ligands forming a [In(S4)(S6)]- unit. Two [In(S4)(S6)]- units are bridged by an S72- chain forming a dimer. A similar reaction of InCl3 with K2S5 and Ph4PCl in a slightly different mole ratio of 1:2:1 in DMF afforded pale yellow crystals of (Ph4P)2{[In2S14] 0.5[In2S16]0.5} (II). II crystallizes in the triclinic space group P1 (No. 2) with a = 10.906(2) ?, b = 11.892(2) ?, c = 21.554(3) ?, α = 89.81(1)°, β = 97.46(1)°, γ = 92.25(1)°, V = 2769(1) ?3 (at -80°C), and Z = 2. II is a cocrystallizate of [In2S14]2- and [In2Si6]2- anions with equal occupancies. The two anions contain tetrahedral In3+ centers. The In atoms are bridged by an S2- and an S52- ligand to form an eight-membered [In2S(S5)]2+ ring core in an extreme cradle configuration. The remaining two coordination sites on each In atom are occupied by a S42- chelating ligand on one side and a S42- or a S62- chelating ligand disordered on the other. These complexes show no absorption peaks in the UV/vis region of the spectrum. The solid-state far-IR spectra of the compounds exhibit strong absorptions in the 500-100-cm-1 region due to the S-S and M-S stretching vibrations. Thermal gravimetric analysis data for these compounds are reported.
