Phase Sulfur Research Articles

Comparative study of pure and mixed phase sulfurized‐carbon black in battery cathodes for lithium sulfur batteries

AbstractLithium‐sulfur battery (LSB) chemistry is regarded as one of the most promising contenders for powering next‐generation electronics, including electric vehicles. This is due to its high theoretical capacity, the use of inexpensive and environmentally friendly materials, and its alignment with climate‐smart manufacturing principles. Sulfur, the electroactive element in LSBs, undergoes lithiation to form a series of polysulfides, each contributing to the battery's energy density. However, this chemistry encounters several challenges, particularly concerning the stability of sulfur. Recent studies have shown that the presence of a full gamma phase of sulfur in an LSB cathode significantly enhances the capacity and overall cell performance. However, despite the advantages of cathodes with gamma sulfur, the characteristics of LSBs with mixed crystal phases of sulfur (alpha, beta, and gamma) have not been extensively studied. In this context, we developed a simple and cost‐effective synthesis method to produce both single‐phase (alpha) and mixed‐phase sulfur (primarily a mixture of alpha and gamma, with a trace of beta) and conducted their detailed physical and electrochemical characterization for use as electroactive cathode materials in LSBs. The cells fabricated using sulfur‐carbon black as the cathode delivered a specific capacity of approximately 640 mAh/g at a current density of 275 mA/g, demonstrating excellent cyclic stability over 50 cycles with a capacity retention of around 97%. This performance is superior to that of the sulfur‐baked carbon black composite cathode, which achieved 440 mAh/g at the same current density.

Decoding paleomire conditions of paleogene superhigh-organic-sulfur coals

Superhigh-organic‑sulfur (SHOS) coals (coals with organic sulfur content >4 wt%) are unique coal deposits found at a few notable locations in the world. Specific peat accumulation and preservation conditions must be met to form SHOS coals. Organic sulfur is a major constituent of such coals, and it may have various sources depending on the prevailing paleomire conditions. Understanding such paleomire conditions sheds light on the formation mechanisms of SHOS coals. This investigation decodes the paleomire conditions of the Paleogene SHOS coals from Meghalaya, India, using sulfur isotopic compositions (δ34S) of organic sulfur (δ34SOS) and pyritic sulfur (δ34SPy) along with organic petrography, pyrite morphology and trace element ratios. Thirty coal samples were collected from the Jaintia Hills in the east, Khasi Hills in the middle, and Garo Hills in the west of Meghalaya. The organic sulfur content in the Garo, Khasi, and Jaintia coals varies from 1.0 to 3.3 wt%, 1.4 to 13.8 wt%, and 1.0 to 7.2 wt%, respectively. Further, after separation from pyritic sulfur and sulfate sulfur phases, the organic sulfur content ranges from 54.4 to 69.2%, 63.8 to 79.9%, and 59.3 to 73.8%, in the Garo, Khasi, and Jaintia Hills, respectively, suggesting the SHOS nature of these coal samples. The δ34SPy varies from −29.3 ‰ to +5.7 ‰, −21.3 ‰ to +27.3 ‰, and −12.1 ‰ to −4.3 ‰, in the Jaintia, Khasi, and Garo Hills, respectively, while the δ34SOS fluctuates from −4.6 ‰ to +3.7 ‰, −9.3 ‰ to +7.8 ‰, and − 9.0 ‰ to −5.0 ‰, respectively. The δ34S values of pyrite and organic sulfur (OS) in Jaintia coals are 34S depleted compared to seawater sulfate (+22 ‰), leading to fractionations in the range of −51.3 ‰ to −16.3 ‰ (mean − 31.6 ‰) and − 26.6 ‰ to −18.3 ‰ (mean − 23.1 ‰) for pyritic and organic sulfur (OS), respectively. Pyrite in Khasi coals show a relatively heavier δ34S composition averaging at −20.5 ‰, whereas organic sulfur (OS) isotope compositions range from −31.3 ‰ to −14.2 ‰ with a mean of −22.6 ‰. Pyrite and OS in the Garo coals are depleted compared to seawater sulfate. Isotope variations in the Jaintia, Khasi, and Garo coals indicate microbial sulfate reduction (MSR) of seawater sulfate. Large isotopic fractionations between Eocene seawater sulfate and pyritic sulfur (Δ34SSO4Eocene – pyrite = up to −51.3 ‰; mean − 31.6 ‰) in Jaintia coals indicate their possible formation in the water column/near the sediment-seawater interface (open system) and also hint toward dissimilatory sulfate reduction pathways that prevailed under anoxic redox conditions. However, mean values of Δ34SSO4Eocene – pyrite (−20.5 ‰) in the Khasi coals imply pyrite formation deeper in the sediments (more closed system) under dysoxic conditions. The dominance of OS over pyritic sulfur, framboidal pyrite, and its microcrystal size distributions in Jaintia coals may suggest syngenetic pyrite formation in open water reducing/anoxic conditions under paralic environments. Elevated Sr/Ba and U/Th values in these coals further confirm the anoxic conditions. Nevertheless, the presence of euhedral pyrite with the alleviated pyrite framboids in the Khasi coals and their complete absence in the Garo coals may suggest dysoxic-suboxic and suboxic-oxic depositional conditions, respectively. The isotopic signatures of the Garo coals suggest sulfur contribution from the parent paleobiota and MSR under a freshwater-oxic environment. Insignificant fractionations between δ34SPy and δ34SOS indicate limited iron and sulfate availability for additional sulfur cycling and disproportionation reactions, typical of oxic conditions. The absence of framboidal pyrite, elevated sulfate concentration, and mean Sr/Ba and U/Th values of 0.5 and 0.3, respectively, further suggest the freshwater peat deposition in the Garo Hills under limnotelmatic to telmatic freshwater conditions. Moreover, high inertinite content (Immf = 9.77–33.16 vol%), possibly induced by atmospheric peat exposure, supports the interpretation of suboxic-oxic paleomire conditions in Garo Hills. Gradually decreasing mineral matter content from Jaintia (mean 13.6 vol%) to Garo coals (mean 7.4 vol%) additionally projects a transition from mesotrophic brackish to freshwater limnotelmatic environment, complementing the shift in the paleomire condition from eastern (Jaintia) to western (Garo) Meghalayan Hills.

The stable sulfur isotope and abundance fluxes of reduced inorganic sulfur and organic sulfur phases recorded in the Permian-Triassic transition of the Meishan type section

Sulfur cycle fluxes implicated in the Permian-Triassic mass extinction have traditionally been studied by the sulfur phase abundances in sedimentary rocks and the stable sulfur isotopic value (δ34S) of seawater sulfate inferred from mineral sulfate analyses. This information might be complemented by studies of the reduced inorganic sulfur and organic sulfur produced following bacterial sulfate reduction. To explore this potential the δ34S and concentration analyses of total reduced inorganic sulfur (TRIS) and organic sulfur – separately in the forms of kerogen (Ker) and individual organosulfur compounds, specifically dibenzothiophenes (DBTs) – has been conducted on sediments across the Late Permian to Early Triassic marine type section of Meishan-1 (South China). The relatively steady δ34S profiles (e.g., < 5 ‰ variation) of all sulfur phases measured through much of the late Permian were indicative of a primary seawater sulfate control, but other biogeochemical modulators caused prominent δ34S fluctuations of TRIS and DBT adjacent to the extinction event. The late Triassic δ34STRIS profile of Meishan-1 displayed a notable 34S enrichment (+15 ‰ increase) in bed 22–24 sediments concomitant with lower δ34SDBT values (−7 ‰ decrease), whereas co-eval δ34SKerS values remained relatively constant. The contrasting δ34SDBT and δ34SKerS data suggests the dynamic behavior of specific diagenetic sulfurisation processes may be resolved by the δ34S of discrete organic sulfur compounds (i.e., dibenzothiophenes, DBTs), but dissipated by the sulfurisation collective represented by the bulk kerogen fraction. The inverse isotopic trend observed between DBT and TRIS resulted in negative Δδ34SDBT-TRIS values identifying an organic sulfurisation pathway(s) with an unusual preference over pyrite (FeS2) for the lighter stable sulfur isotope. A redox control of the δ34SDBTs and δ34STRIS deviations in the bed 22–24 extinction interval was confirmed by coincident variation in TRIS/(TRIS + KerS) and pyrite (Py) and highly reactive (HR) iron ratios (FePy/FeHR). The iron (Fe) speciation data indicated a transition to ferruginous conditions, ruling out Fe2+ limitation as a factor in the bias against 34S evident in DBT formation. The 34S depletion of the DBTs promoted by the ferruginous setting may arise from the rapid and irreversible reaction of organic substrates with labile sulfur anions (e.g. HS-) or be supported by an especially localised sediment–water depositional microenvironment. Our study highlights the potential of incorporating stable sulfur isotope analytics of reduced and organic sulfur phases, particularly of specific organic compounds, into a holistic assessment of the dynamic sulfur biochemical periods of Earth’s past.

APPLICATION OF BENTONITE IN OBTAINING SULFUR-CONTAINING UREA BASED ON A FLUSH OF UREA AND SULFUR

This paper presents the results of a study of the processes for obtaining granular sulfur-containing carbamide from sulfur and a liquid carbamide melt using bentonite to influence the surface tension between two phases of sulfur and urea to obtain a mixed homogeneous phase. It was revealed that the addition of bentonite to sulfur before adding the latter to the melt of urea, which has a temperature of 135-145 °С at mass ratios (NH2)2CO : bentonite : sulfur = 100 : (1-7) : (1-15) prevents the stratification of melts sulfur and urea. The optimal conditions for obtaining, the composition and properties of granular sulfur-containing urea with a balanced content of nitrogen and sulfur are determined by adding a mixture of sulfur with bentonite to the urea melt before granulation. In fertilizers obtained with the addition of a mixture of sulfur with bentonite to the melt of carbamide at the studied ratios, the strength of the granules increases from the initial 2.65 to 4.76 MPa, the gyroscopic point increases from 58.4% to 62.3%, pH and porosity decrease from 8 02 to 5.32 and from 5.60 to 4.55, respectively, and the dissolution rate of the granules decreases 3.36 times. It was also found that when adding a mixture of sulfur with bentonite to the melt of carbamide, the density and viscosity of the melt increase with an increase in the amount of added mixture of sulfur with bentonite. An increase in the amount of addition of a mixture of sulfur and bentonite from 1 to 15 and from 1 to 7 g per 100 г melt of urea at a temperature of 135 °C leads to an increase in the density and viscosity of the melts from 1.16 to 1.33 g/cm3 and from 2.56 to 3.06 cPz. Microscopic examination showed that adding a mixture of sulfur with bentonite to the carbamide melt leads to a decrease in the size of micropores and microcracks up to 0.93 microns wide. On the basis of the results obtained, optimal technological parameters and a process flow diagram for the production of sulfur-containing granulated carbamide are proposed.

Thermal transport properties of graphene aerogel as an advanced carrier for enhanced energy storage.

Leveraging graphene aerogels as carriers offers innovative avenues for achieving enhanced energy density, thermal conductivity, and stability in energy storage materials due to their unique attributes. This study investigates the thermal transport properties of composite sulfur cathode materials and phase change materials based on graphene aerogels using molecular dynamics simulation. A graphene aerogel model is established, and the effects of sulfur and octadecane content on the thermal transport properties of graphene aerogels and graphene aerogel-based composites are examined. A theoretical model of heat transport is developed to analyze the contribution of fillers and graphene aerogels to the thermal conductivity of the composites. The results show that the theoretical analytical model shows strong agreement with the molecular dynamics results, especially at high filler content. This research provides valuable theoretical guidance for understanding the thermal transport properties of graphene aerogel-based composite sulfur cathode materials and phase change materials.

Study on the enhancement of low carbon-to-nitrogen ratio urban wastewater pollutant removal efficiency by adding sulfur electron acceptors.

The effective elimination of nitrogen and phosphorus in urban sewage treatment was always hindered by the deficiency of organic carbon in the low C/N ratio wastewater. To overcome this organic-dependent barrier and investigate community changes after sulfur electron addition. In this study, we conducted a simulated urban wastewater treatment plant (WWTP) bioreactor by using sodium sulfate as an electron acceptor to explore the removal efficiency of characteristic pollutants before and after the addition of sulfur electron acceptor. In the actual operation of 90 days, the removal rate of sulfur electrons' chemical oxygen demand (COD), ammonia nitrogen, and total phosphorus (TP) with sulfur electrons increased to 94.0%, 92.1% and 74%, respectively, compared with before the addition of sulfur electron acceptor. Compared with no added sulfur(phase I), the reactor after adding sulfur electron acceptor(phase II) was demonstrated more robust in nitrogen removal in the case of low C/N influent. the effluent ammonia nitrogen concentration of the aerobic reactor in Pahse II was kept lower than 1.844 mg N / L after day 40 and the overall concentration of total phosphorus in phase II (0.35 mg P/L) was lower than that of phase I(0.76 mg P/L). The microbial community analysis indicates that Rhodanobacter, Bacteroidetes, and Thiobacillus, which were the predominant bacteria in the reactor, may play a crucial role in inorganic nitrogen removal, complex organic degradation, and autotrophic denitrification under the stress of low carbon and nitrogen ratios. This leads to the formation of a distinctive microbial community structure influenced by the sulfur electron receptor and its composition. This study contributes to further development of urban low-carbon-nitrogen ratio wastewater efficient and low-cost wastewater treatment technology.

Unveiling Pseudo-Dirac Resonances in the (7×7)R19.1° Phase of Sulfur Segregated on Cu(111) Surface

Unveiling Pseudo-Dirac Resonances in the (7×7)R19.1° Phase of Sulfur Segregated on Cu(111) Surface

Flotation Decarbonization and Desulfurization of a High-Sulfur Bauxite in China

A high sulfur content is one of the challenges in the processing of refractory bauxites in China. The high carbon content of bauxite makes it more difficult to deal with. Desulfurization and decarbonization are the critical issues in the efficient exploitation of high-sulfur bauxite resources. An experimental study on the removal of sulfur and carbon in high-sulfur bauxite is proposed. The sulfur and carbon phases in high-sulfur bauxite were studied via X-ray diffraction and chemistry quantitative analyses. The results show that the sulfur phases in the high-sulfur bauxite mainly exist in the form of sulfide sulfur (pyrite), and the carbon phases in the sample mainly exist in the form of elementary substance carbon. The morphological features of pyrite in the high-sulfur bauxite were analyzed using a microscopic analysis and a scanning electron microscope (SEM). The pyrite exists in minerals in the forms of euhedral, semi-euhedral and other crystalline structures, with a particle size varying from several hundred microns to only a few microns. The raw ore, with a sulfur content of 4.78%, a sulfide sulfur content of 4.20%, a carbon content of 3.10% and an elementary substance carbon content of 2.46% goes through the “one roughing, one cleaning, two scavenging” process after a pre-decarburization, obtaining the total desulfurization recovery of 96.20% with a desulfurization tailing sulfur content of 0.38%, a carbon content of 0.27% and an alumina content of 71.85%, respectively. This work provides technical support for the efficient utilization of high-sulfur and high-carbon bauxite.

Exceptional X-Ray contrast: Radiography imaging of a Middle Triassic mixosaurid from Svalbard.

The black shales of the Middle Triassic Botneheia Formation in Svalbard are known for their fossil richness with abundant ichthyosaur remains and beds of the bivalve Daonella. Vertebrate remains from the Muen Mountain on Edgeøya are shown to have exceptional X-ray contrast due to a combination of sulphide and sulphate permineralisation and pseudomorphing. Radiography imaging of a previously described specimen, PMO 219.250, revealed new and spectacular details such as more carpals, teeth, and skull sutures. Teeth and skull characters are taxonomically significant. supporting the referral of PMO 219.250 to Phalarodon and further suggesting an affinity to P. atavus. Three sulphur phases were identified, with the sulphide sphalerite (ZnS) being the highest temperature phase, followed by the sulphate baryte (BaSO4), and the sulphide pyrite (FeS2). Sulphate permineralisation is also seen in specimens from the Upper Jurassic on Svalbard. We suggest that sulphur-rich fluids have flowed and dissolved barium from the shales and deposited the sphalerite and baryte, and that this could be linked to the Cretaceous HALIP. The Jurassic specimens are only permineralised by baryte, while the Triassic specimens have also been permineralised, but mainly pseudomorphed by baryte with crystals of sphalerite. Lithology differences appear to have controlled the compaction of the Triassic specimens, while the Jurassic specimens have retained their three-dimensional shape due to the baryte emplacement relatively earlier in their depositional history. Although soft tissues are not preserved, the excellent X-ray contrast in the Middle Triassic specimens is reminiscent of pyritised fossil sites such as the Hunsrück Slate (Devonian), Beecher's Trilobite Bed (Ordovician), and the La Voulte-sur-Rhône marls (Jurassic).

Comparison of sedimentary iron speciation obtained by sequential extraction and X-ray absorption spectroscopy

Iron (Fe) speciation in marine sediments and suspended particulate matter (SPM) are widely used to investigate the role of Fe minerals in marine biogeochemical cycling and to reconstruct paleo-redox conditions. A traditional method for the determination of Fe speciation are sequential extractions, in which operationally defined Fe pools are dissolved by specific extraction solutions. More recently, many studies make use of synchrotron radiation-based X-ray absorption near edge spectroscopy (XANES), especially if little sample material is available or a high spatial resolution is required. However, few studies have systematically compared Fe speciation obtained by the two methods. Here, we report Fe speciation for marine sediments (both wet and freeze-dried) and SPM from contrasting marine environments (western Baltic Sea and Amazon shelf) obtained by sequential extraction and XANES. The two methods yield comparable results regarding the approximate proportion of reactive Fe ((oxyhydr)oxide, carbonate and sulfide minerals) in the total Fe pool and the extent to which reactive Fe minerals have been converted to pyrite. However, methodological issues associated with both approaches complicate a direct comparison of specific mineral groups. Pyrite concentrations obtained by XANES are lower than those obtained by extraction, which is attributed to an underestimation by XANES due to self-absorption effects and an overestimation by the chromium reduction method due to dissolution of reduced sulfur phases that are not associated with Fe. As substantial amounts of pyrite are oxidized during freeze-drying and sample storage, we recommend to analyze wet sediments in modern marine environments. The XANES spectra of Fe (oxyhydr)oxide and Fe(III)-containing (ferric) clay minerals are similar, which is why these components cannot be differentiated by XANES. Similarly, sequential extraction schemes are known to dissolve a variable proportion of ferric clay minerals along with Fe carbonates and Fe (oxyhydr)oxides. Further investigating the role of ferric clay minerals in the low-temperature marine Fe cycle may therefore require the use of additional methods. Our findings may help to assess the transferability of XANES-based Fe speciation for small sediment and SPM samples to those reported in more traditional studies on Fe biogeochemical cycling and paleo-redox conditions.

Investigation and Determination of Electrochemical Reaction Kinetics in Lithium-Sulfur Batteries with Electrolyte LiTFSI in DOL/DME

A major challenge in the simulation of Li-S batteries is that the electrochemical reaction parameters supplied from the fitting of 0-d or 1-d models depend on the cathode and separator microstructure, so these parameters cannot be used in the design and optimization of material microstructure. The present investigation fits the electrochemical reaction kinetics employing a continuum model taking into account the pore size distribution and tortuosity of cathode and separator in the transport of sulfur molecules and ion species (Li+ ion, electrolyte and sulfide anions) in solvated or desolvated form depending on pore size. Hence, the specified reaction kinetics parameters are independent from the material microstructure. The Li-S redox reaction model includes six redox reactions in the cathode and the lithium redox reaction at the anode. Reactions are assumed to take place in the electrolyte solution rather than in the solid phase of sulfur or lithium sulfide precipitates, where dissolution/precipitation kinetics is modeled especially for the low solubility compounds: sulfur, Li2S and Li2S2. The fitting exercise is conducted based on experimental data of a cyclic voltammetry cycle accompanied by in operando UV–vis spectroscopy. The investigated battery has electrolyte LiTFSI in DOL/DME and no electrocatalysts in any part of the cell.

Growth mechanism of metal iron particles with sulfur additives in direct reduction: First-principles calculations and experiments

Sulfur additive can greatly promote iron particles growth in direct reduction. However, promotion mechanism for metallic iron particles growth is unclear. FeS was found as the thermodynamic stable sulfur phase in reduction, intensifying in metal iron particles growth. Therefore, microstructure evolution and phase transition of metallic iron growth with FeS was investigated by reduction experiments. There were three stages in reduction. Firstly, liquid FeS was found, and Fe was produced around pore. Secondly, Fe was wetted and wrapped by liquid phase (Fe-FeS). Thirdly, Fe migrated to even in liquid phase, then irregular fine Fe particles gradually transformed and aggregated to sphere. Furthermore, controlling mechanisms in each stage were identified. The first stage was driven by reduction reaction. For second stage, interfacial interaction was found as the driving force. As wettability is macroscopic manifestation of interfacial interaction, wetting experiments was used. The best wettability was found in Fe/FeS interface followed wetting order: Fe/FeS(1200 °C) > FeS/SiO2(1200 °C) > Fe/SiO2 (1570 °C) with contact angle of 1.86°, 71.5° and 100°, respectively. First-principles calculations further revealed that the strongest interfacial interaction between Fe/FeS drive second stage due to its combining ionic and covalent bonding, and the highest interfacial separation work in Fe(200)/FeS(110) which was 1.998 J/m2. Meanwhile, the well wettability of Fe/FeS also provides a well kinetic basis for third stage, and the huge Fe concentrations difference in FeS and irregular fine particles interfacial energy are combined to drive the stage. Summary, the growth mechanisms of metallic iron particles in direct reduction with sulfur is systematic established.

Aqueous Recovery of Zinc and Lead from Coal Fly Ashes of a Colombian Thermoelectric Plant

A hydrometallurgical treatment under ambient conditions was proposed in order to eliminate and recover the lead and zinc contained in a sample of thermal coal fly ash used to produce energy. By using leaching solutions with conventional inorganic acids (HCl, HNO3, and H2SO4), ferric chloride, and sodium citrate, more than 90% zinc and approximately 40% lead were obtained. The most favorable leaching conditions were set at 0,5 M, with a pH value of 8 for citrate. Two leaching stages were necessary to optimize metal recovery: the first with nitric acid for zinc extraction and the second one with citrate for the lead. The sulfur phases of the metals limited a complete metal extraction.

A tandem electrocatalyst with dense heterointerfaces enabling the stepwise conversion of polysulfide in lithium-sulfur batteries

The complicated sulfur phase transformation and diversity kinetics of lithium polysulfide intermediates hinder the practical applications of Li-S batteries. Herein, we report that Mo-Ni bimetal sulfide nanosheets with dense heterointerfaces and defects can decouple the complicated reactions into well-controlled multi-steps in tandem. Specifically, the MoS2 in Mo-Ni tandem catalyst is more effective in catalyzing the phase transformation from Li2S8 to Li2S4, while NiS2 delivers higher catalytic activity toward both the Li2S4 to Li2S conversion and the Li2S dissociation steps, as indicated by density functional theory calculations and comprehensive experiments. This integrated system tends to selectively propel the stepwise conversion of sulfur and thereby enhancing the battery performance. As a result, the sulfur loaded cathode delivers a high initial capacity of 1481 mAh g−1 at 0.2 C, and a low capacity decay rate of 0.0236% per cycle over 1000 cycles at 2 C. This study demonstrates the feasibility of using tandem catalysis for regulating the smooth solid-liquid-solid multiphase transformation of polysulfides.

Supervolcanic resurfacing in northwestern Arabia Terra, Mars

An area roughly 9 × 105 km2 within northwest Arabia Terra contains several depressions interpreted to be supervolcanic calderas, contained within a chemical province considered consistent with large-scale igneous processes. Despite the underlying global significance to climate and geology, the supervolcanic hypothesis is yet to be tested with comprehensive compositional or geophysical analyses. Here we present geochemical evidence consistent with regional-scale supervolcanic resurfacing, with associated eruptions capable of degassing a climate-altering ∼108 kg of sulfur phases. Through gravitational modeling, we find evidence of low-density pyroclastic loading within this region, and a low elastic thickness, suggestive of a higher heat flow during the eruptive process. Our geochemical observations within this region reinforce its compositional uniqueness compared to contemporaneous volcanoes.

Microstructural Evolution Revealed By Operando X-Ray Tomographic Microscopy in Next Generation Batteries

Sulfur conversion chemistry boasts a high theoretical specific capacity of 1672 mAh/gs and promises to deliver a high-energy density battery when combined with a lithium metal anode (3862 mAh/gLi). The use of such chemistries has the additional benefits of utilizing abundant and low cost materials in the cathode, i.e. carbon and sulfur.[1] Despite clear advantages, lithium-sulfur (Li-S) batteries still face a low practical energy density, poor rate performance, and limited cycling life. These issues are a result of the complex conversion chemistry of the cathode, and the stripping/plating mechanism of the Li-metal anode. These processes include the dissolution and diffusion of polysulfide species through the cell’s electrolyte from the cathode resulting in capacity fade, in addition to the growth of dendritic structures from the anode causing the formation of ‘dead lithium’ and short circuiting of the battery. A plethora of strategies have been developed to address the issues posed by the soluble polysulfide species, from using additives to prevent polysulfide shuttling, to encapsulation of sulfur to prevent its dissolution. While to address the growth of Li-dendrites, electrolyte formulations and the use of interlayer materials have been investigated.When developing these strategies, a detailed understanding of the conversion chemistry and Li-metal plating/stripping mechanisms during cycling is required. This can be obtained by e.g. the use of Raman spectroscopy to probe chemical changes to electrolytes and observe polysulfide speciation,[2] or using phase-field modelling to investigate factors that influence the growth mechanisms of Li-metal during plating.[3] In addition, sulfur dissolution and Li-metal dendrite growth induce microstructural changes that need to be probed using techniques with an appropriate resolution and field-of-view, e.g. synchrotron x-ray tomographic microscopy (XTM), which is capable of micrometre resolution, a near millimetre wide field of view, and measurement times of less than 60 seconds. This allows synchrotron XTM to continuously probe microstructural changes during battery operation, giving quantitative insights into the complex electrochemical mechanisms of the sulfur cathode and Li-metal anode.In this contribution we address the conversion processes of sulfur and its relation in limiting the battery’s practical specific capacity by using a capillary cell type battery, placing the entire cathode within the field of view of the XTM measurement. This enables quantification of the sulfur phase and correlative analysis with simultaneously acquired electrochemical data.[4] We demonstrate the full dissolution of elemental sulfur, with further conversion of sulfur species occurring immediately, and that an efficient diffusion of dissolved polysulfide species through and from the cathode is crucial to achieve a high specific capacity of Li-S cells in practice. Furthermore, we find that in the final step of cell discharge, a uniform and porous Li2S layer is formed on the cathode surface, effectively limiting access to the carbon surface and preventing further polysulfide conversion. We also demonstrate XTM as a unique technique to follow the growth of Li-metal microstructures in real time showing the difference in growth mechanisms when using different electrolyte compositions and under different cycling conditions. We observed change in the growth mechanisms of Li-metal. from homogenous mossy growth of Li-metal, to island dendritic growth and the formation of dead Li, to the growth of a globular phase, showing a changes in the fundamental process of Li-metal growth.[1] M. Agostini, J.Y. Hwang, H.M. Kim, P. Bruni, S. Brutti, F. Croce, A. Matic, Y.K. Sun, Adv. Energy Mater. 8 (2018) 1–7.[2] M. Sadd, M. Agostini, S. Xiong, A. Matic, ChemPhysChem 23 (2022).[3] Y. Liu, X. Xu, M. Sadd, O.O. Kapitanova, V.A. Krivchenko, J. Ban, J. Wang, X. Jiao, Z. Song, J. Song, S. Xiong, A. Matic, Adv. Sci. 2003301 (2021) 1–11.[4] M. Sadd, S. De Angelis, S. Colding‐Jørgensen, D. Blanchard, R.E. Johnsen, S. Sanna, E. Borisova, A. Matic, J.R. Bowen, Adv. Energy Mater. 2103126 (2022) 2103126.

Dual MOF-Derived MoS2 /CdS Photocatalysts with Rich Sulfur Vacancies for Efficient Hydrogen Evolution Reaction.

Cocatalyst plays an important role in efficient charge transfer and separation for photocatalysis. Herein, a MoS2 /CdS photocatalyst with MoS2 as cocatalyst was designed by using Mo-MOF and Cd-MOF as precursors. Due to the existence of rich sulfur vacancies and 1T phase, MoS2 shows strong charge capture and transport ability. The photo-generated electrons on conduction band (CB) can be bound by the sulfur vacancy of CdS and effectively transported to MoS2 through the compact interface between the CdS nanoparticles and 2D large-scale MoS2 . The optimal photocatalyst 1 %MoS2 /CdS exhibited dramatically improved photocatalytic hydrogen production activity, which is 28 times that of pristine CdS and even about 2 times that of 1 %Pt/CdS with same loading amount of noble metal Pt. This work highlights the role of Mo-MOF derived MoS2 with 1T-2H phases as a sustainable and prospective candidate of cocatalyst for improving charge separation and photocatalytic stability of MoS2 /CdS composites.

Performance and reaction mechanism of pyrite(FeS2)-based catalysts for CO reduction of SO2 to sulfur

In this study, an iron sulfide catalyst (PAC) was prepared to catalyze the reaction of CO reducing SO2 to sulfur to satisfy the high activity and stability of the catalyst, simplify the preparation process, and remove the sulfurization process. The physicochemical properties, reduction activity of the iron sulfide catalyst, and reaction mechanism of PAC-catalyzed CO reduction of SO2 were then systematically investigated. The results indicated that the optimum reaction conditions were a FeS2 proportion of 6 wt%, a reaction temperature of 550 °C, an airspeed of 5000 h−1, and a CO/SO2 molar ratio of 2.6:1. Under these conditions, the SO2 conversion of PAC was stabilized at over 99.5% with a sulfur yield of up to 95.5% within 850 min without deactivating the active component or deteriorating the sulfate. This proves that PAC has very high catalytic activity and stability. The XRD and in situ XRD characterization showed that the reduced PAC contained primarily Fe7S8 in the sulfur phase, while no sulfate and sulfite were found. The reaction mechanism of the PAC-catalyzed CO reduction of SO2 can be divided into the FeS2 thermal decomposition mechanism and the COS intermediate product mechanism.

Three-dimensional microstructure and mineralogy of a cosmic symplectite in the Acfer 094 carbonaceous chondrite: Implication for its origin

Cosmic symplectites (COSes), consisting mainly of nanoscaled symplectic intergrowths of magnetite and Fe-Ni sulfides, have extremely heavy oxygen isotopic compositions and are considered tracers of 16O-poor primordial ice in the early solar system. We examined the three-dimensional microstructure and mineralogy of one COS particle, COS#1, in the Acfer 094 carbonaceous chondrite and investigated its origin. Synchrotron-radiation based X-ray computed nanotomography revealed a presence of micro-inclusions inside COS#1. The largest inclusion consists mainly of high-temperature phases of anhydrous sodium sulfate (Na2SO4) and elemental sulfur, which seem to have been formed from a Na2SO4-S eutectic melt. COS#1 showed a trilayered structure surrounding the large inclusion: the innermost coarse-grained layer consisting mainly of 100–200 nm-sized magnetite and Fe-sulfide, the symplectite layer consisting mainly of nanoscaled symplectic intergrowths of magnetite and Fe-Ni sulfides, and the outermost Fe-oxide layer. The symplectite layer comprises the major volume of COS#1 and shows the pseudomorphic structure of precursor Fe-Ni metal grains. The coarse-grained layer seems to have been formed via metal–salt interaction (hot corrosion) at high temperatures, where the precursor Fe-Ni metals contacted with the Na2SO4-S melt. The symplectite formed simultaneously with the coarse-grained layer due to high-speed diffusion of sulfur and oxygen inside the metal grains. The high-temperature metal–salt interactions should have occurred before the incorporation of COS#1 into the meteorite parent body. The precursor of COS#1 should have consisted of Fe-Ni metals and O-Na-S-rich material. The two reductive and oxidative components seem to have formed separately and got together by some mechanical mixing processes in nebula. The COS#1 precursor was heated in a short period and the O-Na-S-rich material melted. The melt induced the hot corrosion of the Fe-Ni metals and was subsequently cooled and solidified. Subsequently, it was incorporated into the meteorite parent body as COS#1. In the parent body, aqueous alteration occurred and formed the outermost Fe-oxide layer on the COS#1 surface.

Effects of sulfur phase transition on moisture-induced damages in bitumen colloidal structure

Over the years, a reduced upper limit on sulfur content in marine-vehicle fuel has created a situation where a major diversion of sulfur into bitumen will be noticeable in the near future. In addition to the naturally occurring sulfur compounds in bitumen, sulfur is known as a promising admixture for the bitumen matrix. Despite the hydrophobic nature of elemental sulfur, which is commercially used as a modifier or extender in asphalt mixtures, the moisture susceptibility of sulfurized bitumen is one of the concerns challenging the use of sulfur in bitumen. In this study, we used laboratory experiments to examine how the effect of moisture conditioning varies between low-sulfur bitumen and high–sulfur bitumen. We also used molecular modeling in a framework of density functional theory (DFT) to gain insights into the molecular mechanisms by which a hydrophobic substance (elemental sulfur) acts as a hydrophile to attract water molecules and increase the moisture susceptibility of bitumen. The results show that high–sulfur bitumen has significantly more strain accumulation and shear thinning when exposed to water for an extended period. Based on our molecular-level analysis geared toward a DFT approach, the affinity of polymeric chains of sulfur to water could be a driving force for the moisture susceptibility of sulfurized bitumen. The presence of polymeric chains of sulfur, even at ambient temperature, can be attributed to that portion of polysulfides formed at high temperatures that remain in the matrix after dropping the temperature. Another mechanism proposed is the thermal decomposition of polysulfides upon heating, leading to the formation of thiols (RS-H), which can easily interact with water molecules. Considering the higher concentration of SO bonds in sulfurized bitumen, a part of the moisture susceptibility could also be attributed to those sulfur compounds that have been functionalized with hydrophilic groups, such as sulfonate, sulfoxide, or other functional groups containing oxygen. The high concentrations of sulfoxide group (SO), particularly in aged bitumen, and their ability to set up H-bonding interactions, make them potential candidates for effective interactions with water molecules.