Sulfur Ratio Research Articles

Overcoming Limitations in Water–Ethanol Sprayed Superstrate Solar Cells by Compositional Engineering of Cu2CdSn(S,Se)4

The increasing demand for solar energy requires materials from earth-abundant elements to ensure cost-effective production. One such light harvester Cu2CdSn(S,Se)4 fulfills this property. We report the development of functional solar cells based on Cu2CdSn(S,Se)4, which has been previously unreported. Furthermore, we deposited the thin films of Cu2CdSn(S,Se)4 by spray pyrolysis using environmentally benign solvents, in a superstrate architecture, reducing the potential cost of upscaling, the environmental hazards, and enabling its use in semitransparent or tandem solar cells. We analyze the Cu2CdSn(S,Se)4 and its optoelectronic characteristics with different sulfur and selenium ratios in the composition. We noted that Se is homogeneously distributed in the absorber and electron transport layer, forming a Cd(S,Se) phase that impacts the optoelectronic properties. The introduction of Se, up to 30%, is found to have a positive impact on the solar cell performance, largely improving the fill factor and absorption in the infrared region, while the voltage deficit is reduced. The device with a Cu2CdSn(S2.8Se1.2) composition had a 3.5% solar-to-electric conversion efficiency, which is on par with the reported values for chalcogenides and the first report using Cu2CdSn(S,Se)4. We identified the critical factors that limit the efficiency, revealing pathways to further reduce the losses and improve the performance. This work provides the first proof of concept of a novel material, paving the way for developing cost-efficient solar cells based on earth-abundant materials.

Sulfide Capacity and Activity of Iron Oxide in CaO–SiO<sub>2</sub>–FeO Ternary System at 1573 K

The knowledge of sulfide capacities of FeO-containing slags is necessary for better understanding the resulfurization reaction in hot metal pre-treatments. In this study, copper-iron-sulfur liquid alloy was equilibrated with CaO–SiO2–FeO ternary slag to measure sulfide capacities and FeO activities simultaneously at temperature below the melting point of pure iron. The experimental result that the sulfide capacity increased with increasing FeO content could be explained by the fact that FeO was a basic oxide, and the sulfide capacity of the CaO–SiO2–FeO ternary system was significantly larger than those of the CaO–SiO2–MgO, CaO–SiO2–AlO1.5 and CaO–SiO2–CaF2 ternary systems. Although the FeO activity and oxygen potential were raised by the FeO addition, the calculated value for sulfur distribution ratio between CaO–SiO2–FeO slag and hot metal increased with an increase in FeO content.

Synthesis and modification of graphene oxide-like carbon for conversion of hemicellulose to furfural from bagasse

The utilization of biomass to convert into valuable chemicals has been receiving research interest recently. In this study, the catalyst with a similar structure to graphene oxide was synthesized from bagasse (B-GO) by calcination using cellulose as the main carbon source. The influences of calcination temperature, calcination time, and cellulose:ferrocene ratios on the FTIR and furfural yield of B-GO were investigated, respectively. The sulfonated graphene oxide-like catalyst (B-SGO) was prepared from B-GO by sulfonation method with sulfuric acid for the application of converting hemicellulose in bagasse into furfural. The characteristics of B-GO and B-SGO materials were analyzed via modern analytical methods. The characteristic analysis of B-SGO results indicated that −SO3H was successfully attached to the B-GO with a sulfur mass ratio of 0.79%, increasing the acidity of the material and enhancing the catalytic efficiency. The effects of reaction temperature, reaction time, catalyst content, NaCl content, and hemicellulose dosage on the furfural yield of B-SGO were also investigated, respectively. The result showed the highest furfural yield achieved at 75.55% when conducting the reaction at 190°C in 120 min with the catalyst content at 1%, 0.1 mol/L NaCl, and a hemicellulose dosage of 1.5 g. Thereby, showing the potential application of synthesized materials from biomass in the process of converting hemicellulose into furfural along with utilizing the brackish water and wastewater containing low salt content as the solvent for the conversion process.

Defect-engineered Sulfur Vacancy Modified NiCo2 S4-x Nanosheet Anchoring Polysulfide for Improved Lithium Sulfur Batteries.

The low conductivity of sulfur and the shuttle effect of lithium polysulfides (LiPSs) are the two intrinsic obstacles that limit the application of lithium-sulfur batteries (LSBs). Herein, a sulfur vacancy introduced NiCo2 S4 nanosheet array grown on carbon nanofiber (CNF) membrane (NiCo2 S4-x /CNF) is proposed to serve as a self-supporting and binder-free interlayer in LSBs. The conductive CNF skeleton with a non-woven structure can effectively reduce the resistance of the cathode and accommodate volume expansion during charge-discharge process. The bonding between CNF matrix and NiCo2 S4 nanosheet is enhanced by in situ growth, ensuring fast electron transfer. Besides, the sulfur vacancies in NiCo2 S4 enhance the chemisorption of LiPSs, and the highly active sites at vacancies can accelerate the LiPSs conversion kinetics. LSB paired with NiCo2 S4-x /CNF interlayer achieved improved stability in 500 cycles at 0.2 C and long life of 3000 cycles at 3 C. More importantly, a high areal capacity of 9.69 mAh cm-2 is achieved with a sulfur loading of 10.8mg cm-2 and a low electrolyte to sulfur (E/S) ratio of 4.8. This work provides insight into the sulfur vacancy in catalysis design for LiPSs conversion and demonstrates a promising direction for electronic defect engineering in material design for LSBs.

Kinetics and mechanism of manganese reductive leaching from electrolytic manganese anode slag with elemental sulfur in sulfuric acid solution

Recycling EMAS in an eco-friendly manner is crucial to alleviate the demand for manganese resource and reduce environmental pollution. Hydrometallurgical reductive leaching of EMAS with elemental sulfur is proposed, but sulfur is chemically inert. To improve the rate and degree of reductive dissolution of EMAS using elemental sulfur. Reductive leaching kinetics of EMAS by elemental sulfur with the aid of H2SO4 at atmospheric pressure have been conducted. A shrinking core model was used to explain the leaching data obtained, and the apparent activation energy was determined to be 63.8 kJ mol−1, indicating the leaching was controlled by chemical reation. The reaction order with respect to sulfuric acid concentration and mass ratio of sulfur to EMAS were 2.6 and 0.9, respectively. The leaching rate equation was established based on the shrinking core model, and good agreement between experimental data and predicted rate curves was obtained. Mechanism of reductive leaching was reasonably speculated with the assistance of X-ray diffraction and scanning electron microscope, revealing that the manganese reduction and sulfur oxidation progressed step by step, following the order Mn4+→Mn3+→Mn2+ and S0→S1+→S2+→ S4+→S6+. The ring opening reaction of [S8]•+ was identified as the rate-determining step. The results of this research provide a theoretical guidance for improving the speed and degree of manganese reduction leaching.

Performance calculation of slag from vanadium titano-magnetite by full oxygen bath smelting process

Vanadium titano-magnetite is an important iron ore resource containing iron, vanadium and titanium. Although iron and vanadium can be recovered by the traditional blast furnace process, titanium can only be stored in the form of TiO2 bearing slag, which resulting in a great waste of titanium resources. In the full oxygen bath smelting process, thanks to high oxygen potential, low nitrogen content and no coke bed in the furnace, the reduction of TiO2 in the slag. This may lead to slag viscosity, inhibit the smelting of vanado-titano-magnetite, and obtain a slag with high TiO2 content. Based on slag coexistence theory, a multi system coexistence theoretical model of vanadium titano-magnetite smelting slag is established, and the influence of slag basicity on the concentration of slag components and the ratio of sulfur between slag and iron is calculated. The results show that with the increase of slag basicity, the interaction concentration of TiO2 in slag decreases gradually, which makes the reduction of TiO2 more difficult and is conducive to the smelting of vanadium–titanomagnetite. Under the optimum alkalinity and reduction temperature (R=1.1, melting temperature is 1500 °C), the distribution ratio of S element between slag and iron is 6.57, and the theoretical S concentration in molten iron is 0.073%. The molten iron can meet the steel-making requirements after pretreatment and desulfurization.

Application of Stable Isotope Analysis for Detecting the Geographical Origin of the Greek Currants "Vostizza": A Preliminary Study.

There is a plethora of food products with geographical indications registered in the European Union without any study about their discrimination from other similar products. This is also the case for Greek currants. This paper aims to analyze if stable isotope analysis of C, N, and S could discriminate the Greek currants "Vositzza", registered as a product of Protected Designation of Origin, from two other currants registered as products of Protected Geographical Indication coming from neighboring areas. The first results show that the stable isotope ratio of sulfur is not detectable due to the very low sulfur content in the samples, and the analysis should be based on the stable isotope ratios of carbon and nitrogen to discriminate these products. The mean value of δ15N (1.38‱) of PDO "Vostizza" currants is lower than that of currants grown outside the PDO zone (2.01‱), while the mean value of δ13C of PDO "Vostizza" currants is higher (-23.93‱) in comparison to that of currants grown outside the PDO zone (-24.83‱). Nevertheless, the results indicate that with only two isotopic ratios, discrimination could not be achieved, and further analysis is required.

Grafting of Porous Conductive Fiber Mats with an Antifouling Polymer Brush by Means of Filtration-Based Surface Initiated ATRP.

This work addresses the challenge of surface modification of porous, electrospun fiber mats containing an insoluble conducting polymer coating. Herein, a novel methodology of grafting a polymer brush onto conducting polymer fiber mats is developed that employs filtering of the polymerization solution through the fiber mat. An electrospun sulfonated polystyrene-poly(ethylene-ran-butylene)-polystyrene (sSEBS) fiber mat is first coated with a layer of conducting copolymer bearing an Atom Transfer Radical Polymerization (ATRP) initiating functionality (PEDOT-Br). The surface-initiated ATRP from the fibers' surface is then carried out to graft a hydrophilic polymer brush (poly(ethylene glycol) methyl ether methacrylate) by means of filtering the polymerization solution through the fiber mat. Scanning electron microscopy (SEM) images reveal a progressive change in the morphology of the fiber mat surface with the increasing volume of the filtrated polymerization solution, while energy dispersive X-ray spectrosdcopy (EDX) spectra show a change in the atomic oxygen to sulfur (O/S) ratio, therefore confirming the successful grafting from the fibers' surface. The conductive fiber mat grafted with hydrophilic brushes shows a 20% reduction in the non-specific adsorption of bovine serum albumin (BSA) compared to a pristine fiber mat. This study is a proof-of-concept for this novel, filtration-based, surface-initiated polymerization methodology.

Effect of Sulfur Contents in NiZnS Composite Photocatalysts on Solar Water Splitting

Solar energy is attracting much attention as an eco-friendly source for future energy needs. Herein, NiZnS photocatalysts were synthesized with a hydrothermal method at various sulfur contents. The ZnS material is widely used as a photocatalyst because of its high stability, low toxicity, and excellent charge separation characteristics. Nickel is considered a co-component in the ZnS base to improve hydrogen evolution efficiency, because nickel sulfide has a narrow band gap. Field emission scanning electron microscopy analysis was used to observe particle size and shape. As the sulfur ratio increased, the particle size increased, and relatively uniform particle sizes were obtained at the 2:2 molar ratio of NiZn:S. X-ray diffractometer analysis showed the formation of ZnO crystals at low sulfur contents in the NiZnS photocatalysts. Among the various NiZnS compositions, the NiZn:S ratio of 2:2 resulted in the highest hydrogen production rate (1541.5 μmol/g/h) with stable reproducibility. UV-vis spectroscopy was used to analyze light absorbance, and the band gap changed with different sulfur contents due to the oxygen vacancies in ZnO, as identified by X-ray photoelectron spectroscope. High amounts of thiourea used to introduce the sulfur increased the particle sizes and blocked sunlight coming to NiZnS surfaces, thereby degrading photocatalytic performance. Therefore, changing the sulfur content when fabricating the NiZnS composite photocatalysts affected the crystalline structures and band characteristics of the materials, and it finally resulted in improved light absorption, charge separation, and the hydrogen production rate of the photocatalysts.

Purifying Fe-based amorphous alloys to enhance glass-forming ability by designing a novel refining slag

• A novel refining slag design strategy was proposed for Fe-based amorphous alloys. • The designed SiO 2 -CaO-Al 2 O 3 -B 2 O 3 refining slag was effective in enhancing the GFA. • Inclusions with small lattice disregistry can promote the heterogeneous nucleation. • The enhanced GFA is due to the reduced impurities and inclusions after refining. Designing low melting point and low basicity refining slag suitable for Fe-based amorphous alloys and understanding the inclusions’ formation, removal, influencing mechanisms are quite vital in the fields of metallurgy and materials. In this study, a novel 13%SiO 2 -32%CaO-30%Al 2 O 3 -25%B 2 O 3 (wt.%) refining slag was designed after careful calculations of the liquid phase region, slag-metal equilibrium, surface tension, viscosity, deoxidation capability and sulfur distribution ratio. After refining with our designed slag, the content of impurities and the number density of inclusions in a representative Fe 83 Si 2 B 15 (at.%) amorphous alloy were significantly reduced. Moreover, the glass-forming ability (GFA) of the alloy was also enhanced, enabling the preparation of amorphous ribbons with a lower cooling rate. Based on the impurities in Fe-based amorphous alloys as well as the calculated oxide and sulfide free energy diagrams, CaO, SiO 2 , Al 2 O 3 oxides and CaS, TiS, MnS sulfides will form in the master alloy. The high melting point inclusions in the melt are generally removed via a floatation-separation-absorption process and the Mn, Ti, S impurities are removed via slag-metal interface reactions during refining. As for the detrimental effect of inclusions on glass formation, the small lattice disregistry between Ti, Mn-containing inclusions and primary α-Fe gains reveal that these inclusions are effective in promoting the heterogeneous nucleation, and therefore greatly deteriorate the GFA. These findings are important and provide an ideal solution to purifying the Fe-based amorphous alloys by refining and enhancing the GFA for industrial production.

Viscosity and desulphurisation behaviour of CaO–SiO2–MgO–Al2O3–BaO–MnO slag

ABSTRACT The influence of BaO on the structure, viscosity and sulfide capacity at 1500°C of CaO-SiO2-MgO-Al2O3-BaO-MnO slag was investigated comprehensively. The activity of O2− and activity coefficient of S2− were discussed, and the sulfur distribution ratio was deduced and analyzed from sulfide capacity. The results revealed that the viscosity increased slightly owing to an increase of BaO content, and the complexity of [SiO4]-tetrahedra and the connection between [SiO4]- and [AlO4]-tetrahedra structure were tighter. The sulfide capacity was lager due to the increased sum of basic component, but the increased range was weakened when BaO was more than 3wt-%. The activity of CaO increased and activity coefficient of CaS descended firstly and then enhanced, but the difference between logaCaO and logγCaS tended to be bigger as a function of BaO. The sulfur distribution ratio was in range of 40–50, similar to the variations of sulfide capacity.

Where are you from? Isotopic tracing of juvenile Olrog’s Gulls from Mar Chiquita during the wintering season

ABSTRACT Individual traits such as age-class can have profound effects on space utilisation by individual birds, with juvenile birds more often exhibiting dispersive movements. We studied the origin of juvenile Olrog’s Gulls Larus atlanticus, a threatened species, using stable isotopes ratios of carbon (δ13C), nitrogen (δ15N) and sulphur (δ34S). We analysed feathers from individuals captured in the wintering season at Mar Chiquita Coastal Lagoon, Argentina, and the potential trophic sources of their breeding sites at Bahía Blanca and San Blas. Mean δ13C was similar for trophic sources and mean δ15N was higher for Bahía Blanca. The δ34S showed a greater variation among prey species than among sites. The mean contributions of the main colonies resulted in assigning 37.5% individuals as from Bahía Blanca, 16.7% from San Blas, and 45.8% undetermined. Results indicate that Mar Chiquita coastal lagoon attracts juvenile Olrog’s Gulls dispersing from the two main breeding grounds of the species. This work is one of the first approaches to study the origin of dispersive juvenile larids through the application of stable isotope analysis. This isotopic approach allows obtaining trophic and movement information when it is not possible to use other tools.

Late Quaternary marine transgressions inferred from the pyrite sulfur content and isotopes within core sediments from the southeast coast of China

Paleoenvironmental reconstructions of coastal areas during geological history are critical for understanding past responses to marine transgression. Identifying transgressive layers in sedimentary strata is therefore of great importance. To this end, we examined the content and isotopic composition of pyrite sulfur, in combination with classical organic geochemical indicators (e.g., C/N ratio and the δ13C of organic carbon), to trace the marine transgressions along the southeast coast of China since Marine Isotope Stage (MIS) 5. Our results suggest that the mass ratio of total organic carbon and pyrite sulfur (C/S ratio) is sensitive to seawater intrusion. Three transgressive layers were identified by low C/S ratios in core NDGK2, which correspond to sea level rise during MIS5, MIS3, and MIS1. Sediments deposited during MIS1 are represented by low C/S ratios with an average of 2.31, while those deposited during MIS5 and MIS3 have slightly higher C/S ratios, indicating a less extensive influence of seawater. Pyrite production in sediments deposited during MIS5 and MIS3 may have been limited by sulfate supply, as reflected by more positive values of δ34Spyr, whereas pyrites deposited during MIS1 were likely formed without sulfate limitation, as reflected by more negative values of δ34Spyr. The isotopic signals of pyrite sulfur thus further confirm the inference based on the C/S ratio. The magnitude of the transgression increased from MIS5 to MIS1, which is in agreement with the findings from classical organic geochemical indicators examined in this study, as well as geochemical and micropaleontological salinity indicators from previous studies. Our findings provide a promising method for identifying marine transgressions and their magnitude from the depositional record, especially when sedimentary strata lack diagnostic micropaleontological and sedimentological characteristics.

The shifting of secondary inorganic aerosol formation mechanisms during haze aggravation: the decisive role of aerosol liquid water

Abstract. Although many considerable efforts have been done to reveal the driving factors on haze aggravation, however, the roles of aerosol liquid water (ALW) in secondary inorganic aerosol (SIA) formation were mainly focused on the condition of aerosol liquid water content (ALWC) < 100 µg m−3. Based on the in situ high-resolution field observations, this work studied the decisive roles and the shifting of secondary inorganic aerosol formation mechanisms during haze aggravation, revealing the different roles of ALWC on a broader scale (∼500 µg m−3) in nitrate and sulfate formation induced by aqueous chemistry in the ammonia-rich atmosphere. The results showed that chemical domains of perturbation gas limiting the generation of secondary particulate matter presented obvious shifts from a HNO3-sensitive to a HNO3- and NH3-co-sensitive regime with the haze aggravation, indicating the powerful driving effects of ammonia in the ammonia-rich atmosphere. When ALWC < 75 µg m−3, the sulfate generation was preferentially triggered by the high ammonia utilization and then accelerated by nitrogen oxide oxidation from clean to moderate pollution stages, characterized by nitrogen oxidation ratio (NOR) < 0.3, sulfur oxidation ratio (SOR) < 0.4, ammonia transition ratio (NTR) < 0.7 and the moral ratio of NO3-/SO42-=2:1. When ALWC > 75 µg m−3, the aqueous-phase chemistry reaction of SO2 and NH3 in ALW became the prerequisite for SIA formation driven by Henry's law in the ammonia-rich atmosphere during heavy and serious stages, characterized by high SOR (0.5–0.9), NOR (0.3–0.5) and NTR (>0.7), as well as the high moral ratio of NO3-/SO42-=1:1. A positive feedback of sulfate on nitrate production was also observed in this work due to the shift in ammonia partitioning induced by the ALWC variation during haze aggravation. It implies the target controlling of haze should not simply focus on SO2 and NO2, but more attention should be paid to gaseous precursors (e.g., SO2, NO2, NH3) and aerosol chemical constitution during different haze stages.

Hyperdoping-regulated room-temperature NO2 gas sensing performances of black silicon based on lateral photovoltaic effect

Black silicon co-hyperdoped with sulfur and nitrogen in different ratios is prepared by femtosecond laser-assisted chemical etching in the mixed atmosphere of SF6 and NF3 with varying gas pressure ratios. Their room-temperature NO2 gas sensing capability is studied systematically, in which the photocurrent as a readout signal is generated by the lateral photovoltaic effect of black silicon under an asymmetrical light illumination. These co-hyperdoped black silicon exhibits high response, fast response/recovery, ultrawide detection range from 29 ppb to 2000 ppm, excellent selectivity and acceptable long-term durability over 3 months. Moreover, NO2 gas sensing performances are effectively tuned or optimized by deliberately changing the co-doping ratio of sulfur and nitrogen, as different photovoltaic characteristics are induced by changes in morphology and structural defects resulting from different hyperdoping. Specifically, ultra-high relative gas response (∼3955%@20 ppm NO2) and superior selectivity are obtained at the SF6/NF3 pressure ratio of 56/14, while faster response/recovery time (17 s/ 47 s @ 20 ppm NO2) and response photocurrent with a weaker disturbance by humidity are given by the samples with SF6/NF3 of 7/63 and 63/7, respectively. Therefore, such black silicon material has good potential to meet different application needs.

Unique benthic foraminiferal communities (stained) in diverse environments of sub-Antarctic fjords, South Georgia

Abstract. Sub-Antarctic fjords are among the environments most affected by the recent climate change. In our dynamically changing world, it is essential to monitor changes in these vulnerable settings. Here, we present a baseline study of “living” (rose-bengal-stained) benthic foraminifera from fjords of South Georgia, including fjords with and without tidewater glaciers. Their distribution is analyzed in the light of new fjord water and sediment property data, including grain size and sorting, total organic carbon, total sulfur, and δ13C of bulk organic matter. Four well-defined foraminiferal assemblages are recognized. Miliammina earlandi dominates in the most restricted, near-shore and glacier-proximal habitats, Cassidulinoides aff. parkerianus in mid-fjord areas, and Globocassidulina aff. rossensis and an assemblage dominated by Ammobaculites rostratus, Reophax subfusiformis, and Astrononion echolsi are in the outer parts of the fjords. Miliammina earlandi can tolerate strong glacial influence, including high sedimentation rates in fjord heads and sediment anoxia, as inferred from sediment color and total organic carbon / sulfur ratios. This versatile species thrives both in the food-poor inner reaches of fjords that receive mainly refractory petrogenic organic matter from glacial meltwater and in shallow-water coves, where it benefits from an abundant supply of fresh, terrestrial, and marine organic matter. A smooth-walled variant of C. aff. parkerianus, apparently endemic to South Georgia, is the calcareous rotaliid best adapted to inner-fjord conditions characterized by moderate glacial influence and sedimentation rates and showing no preference for particular sedimentary redox conditions. The outer parts of fjords with clear, well-oxygenated bottom water are inhabited by G. aff. rossensis. Ammobaculites rostratus, R. subfusiformis, and A. echolsi dominate in the deepest-water settings, with water salinities ≥ 33.9 PSU and temperatures 0.2–1.4 ∘C, characteristic of winter water and Upper Circumpolar Deep Water. The inner- and mid-fjord foraminiferal assemblages seem specific to South Georgia, although with continued warming and deglaciation, they may become more widespread in the Southern Ocean.

Improved performance of Cd-free CZTS thin-film solar cells by using CZTS0.4Se0.6 BSF layer

Cu2ZnSnS4 (CZTS) thin film solar cells (TFSCs) have received great attention from the solar cell industry for their environment, price, high absorption coefficient and great electronic properties. This work provides a strategy to prompt the photoelectric conversion efficiency (η) of CdS/CZTS-based TFSCs via introducing the back surface field (BSF) layer and wxAMPS to simulate the results. Meanwhile, the optimum ratio of sulfur to selenium in the BSF layer material CZTSSe has been also studied, and a new device structure has been constructed. Beneficial from the introduction of CZTSSe as a BSF layer, the interface recombination is suppressed and leads to an enhanced Voc. Subsequently, MoO3, ZnS, WO3, TiO2 and In2S3 as candidates to substitute for the toxic Cd buffer layer are investigated. The results demonstrate that In2S3/CZTSSe exhibits the best performance with 28.59 % and 0.99 V, ascribed to a superior spike-like value. It was found that the presence of a spike-like conduction band (CB) at the In2S3/CZTSSe interface and a more suitable conduction band offset (CBO) value could suppress the interfacial complexation. Therefore, In2S3 performs best as a buffer layer material. However, due to the cost of indium, this paper recommends the utilization of wide bandgap semiconductor materials MoO3 and ZnS, which also have good stability and conversion efficiencies that can reach 28.38% and 28.41%, respectively. The work of this paper provides important guidance for researchers to manufacture CZTS TFSCs.

Cu2+ regulates high-performance Fe2O3 nanospheres (Fe1−xCuxO1.5-δ (x = 0.33, 0.4, 0.5)) sulfur loaded matrix to improve the electrochemical performance of lithium-sulfur batteries

Lithium-sulfur batteries are considered as promising energy storage systems owing to rather high theoretical specific capacity (1675 mAh.g−1) and low cost. Nevertheless, the practical prospect is always limited owing to some short-comings, such as sulfur insulation, volume alternation and shuttle effect. To solve these problems, Cu2+ regulated Fe2O3 nanospheres (Fe1−xCuxO1.5-δ) as high-performance matrixes for sulfur composite cathodes of lithium-sulfur batteries are constructed via a facile hydrothermal method. It indicates that Cu2+ regulation can increase the lattice size and exhibit uniform nanospheres micromorphology with less serious agglomeration. Moreover, as sulfur loading material can realize the joint effect on the physical and chemical confinement and some dissociate excess Cu2+ with sulfur also can directly compose some Cu-S structures, further stabilizing the structure of sulfur composite cathode. In addition, Fe0.6Cu0.4O1.5-δ/S composite cathode with sulfur loading mass ratio to 1:3 has fast electrochemical reaction kinetics with the low charge transfer resistance (25.54 Ω) and the high lithium-ion transfer efficiency (DLi+=2.59 ×10−12 cm2·s−1) and the initial specific discharge capacities and ideal capacity retention accompanied by a charge and discharge voltage platform with small fluctuation.

Electrochemical Pourbaix diagrams of monolayer MoSSe with different atomic ratios of chalcogens

MoSSe material is a very promising photoelectric material, and its application environment is aqueous solution. However, there is no research of the electrochemical stability of MoSSe materials in aqueous solution. In this work, the Pourbaix diagrams of monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium are constructed based on density functional theory, and the thermodynamic stabilities and electrochemical corrosion behaviors under different pH values and electrode potentials are studied. The study of the pourbaix diagram of MoSSe shows that part of the corrosion-free region of MoSSe exists within the stable region of water in the Pourbaix diagram, indicating that the MoSSe can exist stably in the water environment. Compared with alkaline solutions, MoSSe has good corrosion resistance in acidic solution and neutral solution. The Pourbaix diagram of Mo<sub>4</sub>S<sub>2</sub>Se<sub>6</sub>, Mo<sub>4</sub>S<sub>6</sub>Se<sub>2</sub>, Mo<sub>4</sub>S<sub>7</sub>Se and Mo<sub>4</sub>SSe<sub>7</sub> show that in the case of high molar fraction of sulfur in monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium, the conditions for the stable existence of materials in aqueous solution can have a larger range, and the corrosion resistance becomes better. In the case of high molar fractions of selenium in monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium, the range of conditions for the stable existence of materials in aqueous solution becomes smaller, and the corrosion resistance becomes worse. In this work, the stabilities and corrosion behaviors of monolayer MoSSe with different atomic ratios of molybdenum, sulfur and selenium in aqueous solution are predicted, and the degradation behaviors of MoSSe materials are further explored, which can provide theoretical guidance for the application of MoSSe materials in the field of optoelectronics.

Study of natural attenuation after acid in situ leaching of uranium mines using isotope fractionation and geochemical data

Acid in situ leaching (AISL) is a subsurface mining approach suitable for low-grade ores which does not generate tailings, and has been adopted widely in uranium mining. However, this technique causes an extremely high concentration of contaminants at post-mining sites and in the surroundings soon after the mining ceases. As a potential AISL remediation strategy, natural attenuation has not been studied in detail. To address this problem, groundwater collected from 26 wells located within, adjacent, upgradient, and downgradient of a post-mining site were chosen to analyze the fate of U(VI), SO42−, δ34S, and δ238U, to reveal the main mechanisms governing the migration and attenuation of the dominant contaminants and the spatio-temporal evolutions of contaminants in the confined aquifer of the post-mining site. The δ238U values vary from −0.07 ‰ to 0.09 ‰ in the post-mining site and from −1.43 ‰ to 0.03 ‰ around the post-mining site. The δ34S values were found to vary from 3.3 ‰ to 6.2 ‰ in the post-mining site and from 6.0 ‰ to 11.0 ‰ around the post-mining site. Detailed analysis suggests that there are large differences between the range of isotopic composition variation and the range of pollutants concentration distribution, and the estimated Rayleigh isotope fractionation factor is 0.9994–0.9997 for uranium and 1.0032–1.0061 for sulfur. The isotope ratio of uranium and sulfur can be used to deduce the migration history of the contaminants and the irreversibility of the natural attenuation process in the anoxic confined aquifer. Combining the isotopic fractionation data for U and S with the concentrations of uranium and sulfate improved the accuracy of understanding of reducing conditions along the flow path. The study also indicated that as long as the geological conditions are favorable for redox reactions, natural attenuation could be used as a cost-effective remediation scheme.