Photoelectron spectroscopic study of sulfur—sulfur interactions in macrocyclic thioethers

He I photoelectron spectra of 1,4,7-trithiacyclononane, 1,4,7-trithiacyclodecane, 1,4,7,10-tetrathiacyclododecane, 1,4,8,11-tetrathiacyclotetradecane, 1,5,9,13-tetrathiacyclohexadecane and 1,5,9,13-tetrathiacyclohexadecane-3,11-diol were measured and used to obtain information on sulphur—sulphur lone pair interactions. Comparisons with spectra of oxygen macrocyclic analogs allowed several general trends in electronic structures of these ligands to be established.     

Grafting polymeric sulfur onto carbon nanotubes as highly-active cathode for lithium–sulfur batteries

Lithium–sulfur(Li–S)batteries are being explored as promising advanced energy storage systems due to their ultra-high energy density.However,fast capacity fading and low coulombic efficiency,resulting from the dissolution of polysulfides,remain a serious challenge.Compared to weak physical adsorptions or barriers,chemical confinement based on strong chemical interaction is a more effective approach to address the shuttle issue.Herein,we devise a novel polymeric sulfur/carbon nanotube composite for Li–S battery,for which 2,5-dithiobiurea is chosen as the stabilizer of long-chain sulfur.This offers chemical bonds which bridge the polymeric sulfur and carbon nanotubes.The obtained composite can deliver an ultra-high reversible capacity of 1076.2 m Ah g~(-1)(based on the entire composite)at the rate of 0.1 C with an exceptional initial Coulombic efficiency of 96.2%,as well as remarkable cycle performance.This performance is mainly attributed to the reaction reversibility of the obtained polymeric sulfur-based composite during the discharge/charge process.This was confirmed by density functional theory calculations for the first time.     

Multibubble sonolysis and sonoluminescence in molten elementary sulfur and sulfur—styrene mixture

The effect of saturation with argon, as well as styrene and iodine additives on the temperature dependence of multibubble sonoluminescence intensity in molten sulfur at 120–230 °C was studied. The shape of the temperature dependence with a maximum at 170–200 °C is determined by the viscosity variations related to the changes in the molecular structure of molten elemental sulfur. At high temperatures, cyclooctasulfane (S₈) molecules break to radical products, which then undergo polymerization that can be slowed down by the additives. Sulfurization of styrene during sonolysis of a sulfur—styrene mixture resulting in products of the thiophene series was detected. Unlike thermal sulfurization that affords 2,5-diphenylthiophene as a major product, sonochemical sulfurization results mainly in 2,4-diphenylthiophene. The mechanism of 2,4-diphenylthiophene formation initiated by the reaction of styrene molecules with S⁺ ions produced upon fragmentation of S₈ within cavitation bubbles is proposed. The glow of electronically excited S⁺* ions is responsible for the band with a maximum at 560 nm in the sonoluminescence spectrum of molten sulfur, which is suppressed by the styrene additive.     

A comparison of sulfur loading method on the electrochemical performance of porous carbon/sulfur cathode material for lithium–sulfur battery

To get a high sulfur loaded porous carbon/sulfur cathode material with an excellent performance, we investigated four different sulfur loading treatments. The samples were analyzed by the Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD) patterns, thermal gravimetric analysis (TGA), and scanning electron microscopy (SEM). We proved that it is more effective to introduce the sulfur into the pores of porous carbon at 300 °C than at 155 °C. Especially, the porous carbon/sulfur composite heated in a sealed reactor at 300 °C for 8 h presents a fine sulfur load with sulfur content of 78 wt.% and exhibits an excellent electrochemical performance. The discharge capacity is 760, 727, 744, 713, and 575 mAh g^?1 of sulfur at a current density of 80, 160, 320, 800, and 1,600 mA g^?1 based on the sulfur/carbon composite, respectively. What is more, there is almost no decay at the current density of 800 mA g^?1 for 50 cycles and coulombic efficiency remains over 95 %.     

Synthesis and electrochemical performance of sulfur–carbon composite cathode for lithium–sulfur batteries

In this paper, porous carbon was synthesized by an activation method, with phenolic resin as carbon source and nanometer calcium carbonate as activating agent. Sulfur–porous carbon composite material was prepared by thermally treating a mixture of sublimed sulfur and porous carbon. Morphology and electrochemical performance of the carbon and sulfur–carbon composite cathode were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectra (EIS), and galvanostatic charge–discharge test. The composite containing 39 wt.% sulfur obtained an initial discharge capacity of about 1,130 mA?h g^?1 under the current density of 80 mA?g^?1 and presented a long electrochemical stability up to 100 cycles.     

Synthesis and application of single-atom catalysts in sulfur cathode for high-performance lithium–sulfur batteries

Lithium–sulfur(Li-S) batteries are regarded as one of the most promising energy storage devices because of their low cost, high energy density, and environmental friendliness. However, Li-S batteries suffer from sluggish reaction kinetics and serious “shuttle effect” of lithium polysulfides(LiPSs), which causes rapid decay of battery capacity and prevent their practical application. To address these problems, introducing single-atom catalysts(SACs) is an effective method to improve the electroch...     

Rational design of Co nano-dots embedded three-dimensional graphene gel as multifunctional sulfur cathode for fast sulfur conversion kinetics

Lithium-sulfur(Li-S)batteries hold great promises to serve as next-generation energy storage devices because of their high theoretical energy density and environmental benignity.However,the shuttle effect of the soluble lithium polysulfides(LiPS)and intrinsic insulating nature of sulfur lead to low sulfur utilization and coulombic efficiency,leading to poor cycling performance.The impeded charge transportation and retard LiPS catalytic conversion also endows the Li-S batteries with sluggish redox reaction,leading to unsatisfied rate capability.In this study,Co-based MOF material ZIF-67 is used as the precursor to prepare Co nano-dots decorated three-dimensional graphene aerogel as sulfur immobilizer.This porous architecture establishes a highly conductive interconnected framework for fast charge/mass transportation.The exposed Co nano-dots serve as active sites to strongly trap LiPS,which endows CoNDs@G with low decomposition energy barrier for fast LiPS conversion reaction and promote the completely Li2 S catalytic transformation.Li-S cells based on the Co-NDs@G cathode exhibits excellent cyclability and a high capacity retention rate of 91.1%in 100 cycles.This strategy offers a new direction to design sulfur immobilizer for accelerated LiPS conversion kinetics of Li-S batteries.     

Preparation of yolk-shell sulfur/carbon nanocomposite via an organic solvent route for lithium–sulfur batteries

A yolk-shell sulfur/carbon (S/C) composite for the cathode of lithium–sulfur batteries was successfully prepared by an accessible method with tetrahydrofuran as solvent. The as-prepared composites are characterized by thermal gravimetric, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption and desorption. In this composite, sulfur particle is encapsulated in the carbon shell even entering into the micropores of carbon Bp2000. The electrochemical performance of the S/C composites is evaluated. The results indicate that the S/C composite with 50 wt% sulfur content shows good reversibility, excellent rate capability, and slow degradation. It delivers an initial capacity of 784.4 mAh g^?1 (based on sulfur weight) and preserves at 598.3 mAh g^?1 after 195 cycles at 1C. It achieves a high-capacity retention of 76.27 % from the 5th to 200th cycle, and as high as 91.19 % during the latter 150 cycles. The improvement is mainly attributed to the favorable structure of the S/C composite, in which the carbon cannot only facilitate transport of electrons and Li⁺ ions but also trap polysulfides and retard the shuttle effect during charge/discharge process.     

Engineering sulfur vacancies for boosting electrocatalytic reactions

Transition metal sulfides are demonstrated to play an increasingly important role in boosting the deployment of ecofriendly electrocatalytic energy conversion technologies. It is also widely recognized that the introduction of vacancies is now becoming an important and valid approach to promote the electrocatalytic performance. In this review, the significance of sulfur vacancies on the enhancement of catalytic performance via four main functionalities, including tuning the electronic structure,...     

Synthesis and electrochemical performance of TiO2–sulfur composite cathode materials for lithium–sulfur batteries

Titania–sulfur (TiO₂–S) composite cathode materials were synthesized for lithium–sulfur batteries. The composites were characterized and examined by X-ray diffraction, nitrogen adsorption/desorption measurements, scanning electron microscopy, and electrochemical methods, such as cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge tests. It is found that the mesoporous TiO₂ and sulfur particles are uniformly distributed in the composite after a melt-diffusion process. When evaluating the electrochemical properties of as-prepared TiO₂–S composite as cathode materials in lithium–sulfur batteries, it exhibits much improved cyclical stability and high rate performance. The results showed that an initial discharge specific capacity of 1,460 mAh/g at 0.2 C and capacity retention ratio of 46.6 % over 100 cycles of composite cathode, which are higher than that of pristine sulfur. The improvements of electrochemical performances were due to the good dispersion of sulfur in the pores of TiO₂ particles and the excellent adsorbing effect on polysulfides of TiO₂.     

Heterogeneous reactions of sulfur dioxide on dust

In urban atmospheric environment, SO2 is the prin- cipal sulfur-containing anthropogenic pollutant, with concentrations reaching into hundreds of parts per bil- lion[1]. Atmospheric SO2 can be adsorbed and oxidized to sulfate on the surface of particles and subsequently involved in the formation of secondary inorganic aerosol in the atmosphere[2―4]. Sulfate particles are known to affect climate by scattering solar radiation, resulting in a net cooling effect, as well as acting as cloud conde…     

Molecular thioamide ↔ iminothiolate switches for sulfur mustards

SNS platinum(II) pincer complexes reversibly bind and release the surrogate half sulfur mustard, 2-chloroethyl ethyl sulfide (CEES). The switch-like behavior of the pincers is attributed to a reversible transformation between the thioamide and iminothiolate forms of the pincer skeleton under slightly acidic and basic conditions, respectively. An amide-based palladium(II) pincer complex also binds CEES, as confirmed crystallographically and by NMR.     

Lithium–sulfur redox: challenges and opportunities

Mechanistic and kinetic insights into the lithium–sulfur (Li–S) redox processes are essential to fundamentally increase the utilization of active material and further realize the practical applications of Li–S batteries. In this article, recent advances of in situ/operando characterizations of Li–S reaction processes and mechanism are presented, revealing the multistep transformations of S species. Interfacial visualization, from the whole interface to nanometer scale, provides specific evidence of sulfur distribution, polysulfide diffusion, and lithium sulfide precipitation. Moreover, the development of efficient electrocatalysts to improve the reaction kinetics are additionally presented and discussed. Although the understanding of the mechanism of the Li–S redox processes has improved in recent times, additional efforts are required for the scale-up production and practical applications of Li–S batteries.     

A multi-functional binder for high loading sulfur cathode

Lithium sulfur(Li-S)batteries are the promising power sources,but their commercialization is significantly impeded by poor energy-storage functions at high sulfur loading.Here we report that such an issue can be effectively addressed by using a mussel-inspired binder comprised of chitosan grafted with catecholic moiety for sulfur cathodes.The resulting sulfur cathodes possess a high loading up to 12.2 mg cm-2 but also exhibit one of the best electrochemical properties among their counterparts.The excellent performances are attributed to the strong adhesion of the binder to sulfur particles,conducting agent,current collector,and polysulfide.The versatile adhesion effectively increases the sulfur loading,depresses the shuttle effect,and alleviates mechanical pulverization during cycling processes.The present investigation offers a new insight into high performance sulfur cathodes through a bio-adhesion viewpoint.     

Sequential analysis of dimethyl sulfur compounds in seawater

A sequential method for the determination of dimethyl sulfur compounds, including dimethylsulfide （DMS）, dimethylsulfonio- propionate （DMSP） and dimethylsulfoxide （DMSO）, in seawater samples has been developed. Detection limit of 2.5 pmol of DMS in 25 mL sample, corresponding to 0.10 nmol/L, was achieved. Recoveries for dimethyl sulfur compounds were in the range of 68.6- 78.3%. The relative standard deviations （R.S.D.s） for DMS, DMSP and DMSO determination were 3.0, 5.4 and 7.4%, respectively.     

Emerging energy chemistry in lithium–sulfur pouch cells

正On pursuing high-energy-density energy storage systems beyond the current lithium-ion battery technique, lithium–sulfur(Li–S) batteries have attracted worldwide attention due to their ultrahigh theoretical energy density up to 500 Wh kg~(-1)[1]. The unique Li–S chemistry based on the conversion reactions between solid sulfur, dissolved lithium polysulfides, and solid lithium sulfide affords thermodynamic advantages including high cathode specific capacity and low anode potential [2]. However,     

Facile preparation of visible-light-sensitive sulfur–nitrogen-codoped titanium dioxide

S–N-codoped TiO₂ powders have been synthesized through a facile one-step sol–gel method by using tetrabutyltitanate and thiourea as precursors. The S–N-codoped TiO₂ treated at 500 °C showed the highest photocatalytic activity for degrading methylene blue under visible light irradiation. XRD, XPS and UV–vis studies revealed that the high visible-light photocatalytic activity of the doped TiO₂ may originate from the synergetic effect of sulfur and nitrogen codoping into TiO₂.     

Iron–sulfur clusters and their electronic and magnetic properties

Iron–sulfur clusters of diverse nuclearities constitute the active sites of a large and prominent family of metalloproteins which play essential roles in all living organisms, such as in electron transfer chains, reduction catalysis, photosynthesis, the respiratory chain and nitrogen fixation. This review is devoted to the presentation of the current state of understanding of their electronic and magnetic properties, which is here derived from their Mössbauer, EPR and ENDOR spectroscopic properties. These techniques constitute fine tools for characterization and provide knowledge of the different oxidation states of these proteins, although our interest here will be mainly centered on the [4Fe–4S*]ⁿ⁺ clusters (with n=1–3). A qualitative physical model involving the competing magnetic interactions in these clusters is discussed. Moreover, this article contains new developments on two more specialized subjects:

• 1.some quantitative consequences of an already published theory of the g-tensors of [4Fe–4S*]ⁿ⁺ clusters (n=1,3) will be derived in Section 3;
• 2.a model permitting the rationalization, from very simple ingredients and formulae, of the redox potentials of a whole set of known synthetic redox clusters (with 1, 2, 3, 4 and 6 iron atoms) will be presented in the final Section 6.

     

Ether-compatible lithium sulfur batteries with robust performance via selenium doping

The increasing demand of the green energy storage system encourages us to develop a higher energy storage system to take the place of the present lithium-ion batteries with limited energy/power densities[1,2].Among the diverse candidates。     

Determination of sulfur forms in wine including free and total sulfur dioxide based on molecular absorption of carbon monosulfide in the air–acetylene flame

A new method for the determination of sulfur forms in wine, i.e., free SO₂, total SO₂, bound SO₂, total S, and sulfate, is presented. The method is based on the measurement of the carbon monosulfide (CS) molecular absorption produced in a conventional air–acetylene flame using high-resolution continuum source absorption spectrometry. Individual sulfur forms can be distinguished because of the different sensitivities of the corresponding CS molecular absorption. The sensitivity of free SO₂ is about three times higher than the value for bound SO₂ and sulfate. The method makes use of procedures similar to those used in classic reference methods. Its performance is verified by analyzing six wine samples. Relative standard deviations are between 5 and 13% for free SO₂ and between 1 and 3% for total SO₂. For the validation of the accuracy of the new method, the results are compared with those of reference methods. The agreement of the values for total SO₂ with values of the classic method is satisfactory: five out of six samples show deviations less than 16%. Due to the instability of free SO₂ in wine and the known problems of the used reference method, serious deviations of the free SO₂ results are found for three samples. The evaluation of the limits of detection focuses on the value for free SO₂, which is the sulfur form having by far the lowest concentration in wine. Here, the achievable limit of detection is 1.8 mg L⁻¹. Figure Detection of non-metal elements using continuum source flame absorption spectrometry