Sulfide Formation Research Articles

Electrophoretic assembly and electronic transport properties of rapidly synthesized Sb2Te3 nanoparticles

With the recent advances in thermoelectric (TE) technology, there is an increasing demand to develop thick films that would enable large-scale TE devices. Assembly of TE-films from size and morphology-controlled nanoparticles has been a challenging issue that can be addressed by the use of electrophoretic deposition (EPD) technique. In this work, morphology-controlled Sb2Te3 nanoparticles were synthesized through microwave-assisted thermolysis, which were subsequently used for EPD of TE films on specially developed glass-substrates. The electronic transport properties were measured in the temp-range of 22–45 °C. The as-made EPD films showed a high initial resistance, ascribed to high porosity and the presence of surface oxide/passivating layers. The impact of two types of small organic molecules -as hexanedithiol and dodecanethiol, on the electronic transport was investigated, resulting in a significant improvement in the electrical conductivity of the films. The XPS analysis suggests that the thiols bind to the surface of nanoparticles through formation of sulfides. Seebeck coefficient in the range of + 160 to + 190 µV/K was measured, revealing the p-type transport through the deposited films. Finally, a power factor of about 2.5 µW/K2.m was estimated the first time for p-type EPD films, revealing the potential of the developed nanoparticles and substrate, the small molecule additives and the EPD process presented in this work.

Enhanced Effect of Metal Sulfide Doping (MgS-TiO2) Nanostructure Catalyst on Photocatalytic Reduction of CO2 to Methanol

The conversion of CO2 gas from the global emission to methanol can be a route to look at in addressing greenhouse gas (GHG) issues. Photocatalysis has been attracting attention in the conversion of CO2 to methanol, as it is seen to be one of the most viable, economic, and sustainable strategies. The biggest hindrance to the use of metal oxide photocatalysts was the poisoning by sulfur content in the CO2 gas feedstock. Therefore, in the development of photocatalysts using metal oxide-based additives, the metal needs to be in the form of metal sulfides to avoid catalyst poisoning due to the presence of H2S. The magnesium sulfide-based TiO2 (MgS-TiO2) photocatalyst has not been synthesized and studied for its photocatalytic potential. In this study, a novel MgS-TiO2 photocatalyst was synthesized using a combination of wet impregnation and hydrothermal method and characterized to determine the physical and chemical properties of the photocatalyst. Characterization results have shown the presence of MgS on the native TiO2 photocatalyst. The optimization of MgS-TiO2 formulation was conducted, wherein the MgS and TiO2 ratio of 0.5 wt % has been shown to give the highest methanol yield of 229.1 μmol/g·h. The photocatalytic parameter optimization results showed that temperature and catalyst loading were the most important factors that impacted the photocatalytic process. In contrast, reaction time had the least significant effect on the CO2 photocatalytic reduction to methanol. This concludes that the MgS-TiO2 photocatalyst has potential and can be used for the photocatalytic reduction of CO2 to methanol.

Fatigue crack growth behavior of railway wheel steel modified by sulfides enveloping oxides inclusions

This study aims to investigate the fatigue crack growth (FCG) behavior of a railway wheel steel, which has undergone inclusion modification through sulfides enveloping oxides. It involves experimental and finite element (FE) investigations, including microstructural and inclusion analysis, mechanical testing (tensile, hardness, fracture toughness, and FCG tests), and FE analysis based on tessellated stress model and fracture mechanics method. The test results reveal that the microstructure of wheel steel remains almost unchanged as the sulfur content increases from 0.002% to 0.008%. However, the inclusion area fraction increases, the average inclusion size decreases, and most of the oxides are modified to be the duplex inclusions in the form of sulfide enveloping oxide. Moreover, the FCG resistance and fracture toughness are improved. The FE analysis results indicate that the tessellated stress around the inclusion, which is caused by the thermal expansion mis-match between inclusions and matrix material, can be reduced by the coverage of hard oxides by soft sulfides. This reduces the driving force of FCG at low ΔK ranges and results in improved FCG resistance. Furthermore, due to the lower driving force of FCG, fatigue cracks in the modified steel are more prone to deflect at cementite lamellas at low ΔK ranges, which leads to a rougher fracture surface. This further improves the FCG resistance by the mechanism of roughness-induced closure. As ΔK increases, FCG is gradually controlled by the remote applied loading, and the influence of the inclusion tends to disappear. In addition, the thermal expansion mis-match between inclusions and matrix material is found to have a more significant effect on FCG of wheel steel than the stiffness mis-match.

Simultaneous removal process of hydrogen sulfide and siloxanes and field application of iron hydroxide desulfurization agent for green hydrogen production from biogas

Biogas, one of renewable energies, is a key element necessary for a carbon-neutral policy and to build a hydrogen economy. In order to utilize biogas, impurities of biogas such as moisture, hydrogen sulfide(H2S), siloxanes, and VOCs should be removed. In particular, since H2S causes corrosiveness of equipment by sulfur oxides, and is harmful to the human body if leaked, it is a major target material to be removed. The minimum concentration of H2S obtainable from the wet method is several ppm. It is known, however that the iron hydroxide-based adsorbent in the dry method can obtain ultimately low concentration of H2S down to 0.1 ppm or less. The DeHyS was manufactured through a series of processes such as mixing iron cloride solution or iron sulfate solution, NaOH solution, and inorganic binder. During the adsorption process, H2S was removed in the form of iron sulfide through a chemical reaction, and siloxanes are known to be removed through physical adsorption. It was also applied to various biogas plant sites such as landfill gas, sewage sludge, livestock manure, and food waste. At this time, the H2S removal efficiency was known to be 99.9% or more, while simultaneous removal of 90% or more of the total siloxanes was possible. Moreover, the biogas produced at the Chungju Food Bioenergy Center was pretreated using the DeHyS and supplied to the nearby Chungju Bio Green Hydrogen Charging Station to produce hydrogen through steam methane reforming(SMR), producing 500 kg of hydrogen from 8,000 m3 of biogas per day.

Using calcium-containing injection wire filled with electrolytic calcium in steel ladle treatment

Aluminum is one of the most common deoxidizers; when it is used in the melt, refractory inclusions of alumina are formed. The presence of these non-metallic inclusions negatively affects the purity of liquid steel, mechanical properties, makes casting difficult due to tightening of the steel-pouring fittings. The modification of alumina inclusions with calcium promotes the formation of liquid calcium aluminates, which leads to an acceleration of their removal from the metal due to a higher ascent rate. Having a high affinity for sulfur, calcium reduces its harmful effect by binding it with the formation of calcium sulfides, reducing the anisotropy of steel properties during further rolling. For steel treatment with calcium, injection wires with a calcium-containing filler are used. As a filler can be used: electrolytic calcium, silicocalcium, aluminum-tremic calcium, or ferrocalcium. The paper describes results of the tests carried out on a calcium-containing wire filled with electrolytic calcium and silicocalcium. It is shown that the consumption of calcium when using silicocalcium wire is on average 35 % higher in comparison with calcium injection wire filled with electrolytic calcium. The calcium recovery rate for different steel grades was evaluated using calcium-containing wires of different designs and filler. In this work, the steel pourability was analyzed. As a determining parameter, dependence of change in position of the tundish stopper rod on calcium content in the metal was considered in the sample from CCM. It was established that a wire filled with electrolytic calcium shows a more effective result in comparison with a silicocalcium wire.

What Determines If a Ligand Undergoes Coordination or Catalytic Activation on a Metal Cluster?

We report a joint experimental and theoretical study on the reactivity of Agn+ clusters with H2S, D2O, and NH3. Complete dehydrogenation products are observed for Agn+ reacting with H2S, but no dehydrogenation products are found for D2O or NH3 under the same reaction condition. Theoretical calculations elucidate why Agn+ clusters show different reactivities with these inorganic hydrides. NH3 shows strong coordination with Agn+, but the dehydrogenation reactions are unfavorable; in contrast, the fragile H-S bonds and stable AgnS+ products facilitate the hydrogen evolution of H2S on Agn+. We fully analyzed the metal-ligand interactions of Agn+ clusters with three molecules and illustrated the reaction dynamics and charge-transfer interactions and altered the superatomic states during the formation of cluster sulfides. We expect this study to benefit the design of stable environmentally friendly desulfurization catalysts and also the understanding of the mechanism on ligand-protected metal clusters in wet chemistry.

Sulfidation Impacts on the Hydrophobicity of Stepped Iron Surfaces

Nanoscale zero‐valent iron (nZVI) has demonstrated high potential for the remediation of contaminated groundwater. Its lifetime is directly related to the hydrophobicity of nZVI. A promising approach to enhance the lifetime of nZVI is through sulfidation. Herein, the density functional theory (DFT) is applied to understand the impact of sulfidation on the hydrophobicity of stepped Fe surfaces. Adsorption properties of sulfur (S) at different coverages on the flat Fe(110) and stepped Fe(210) and Fe(211) surfaces are investigated. Sulfur has the stronger adsorption at a low surface coverage due to limited S–S repulsion. At the highest coverage (⊖ = 1 ML) on Fe(210) and Fe(211), the atoms at the step edges catalyze the formation of iron sulfides. The DFT results show surface hydrophobicity is mainly determined by the S coverage. At the low S coverage, the surface may become more hydrophilic due to the enhanced adsorption strength of water on the surface. However, an increase in the S coverage can efficiently block water adsorption, which is further evidenced by ab initio molecular dynamics (AIMD) results. The findings show that controlling S coverages is essential to engineer the hydrophobicity of nZVI surfaces for practical water remediation applications.

Reductive Hydrogenation of Sulfido-Bridged Tantalum Alkyl Complexes: A Mechanistic Insight.

Hydrogenolysis of a series of alkyl sulfido-bridged tantalum(IV) dinuclear complexes [Ta(η5-C5Me5)R(μ-S)]2 [R = Me, nBu (1), Et, CH2SiMe3, C3H5, Ph, CH2Ph (2), p-MeC6H4CH2 (3)] has led quantitatively to the Ta(III) tetrametallic sulfide cluster [Ta(η5-C5Me5)(μ3-S)]4 (4) along with the corresponding alkane. Mechanistic information for the formation of the unique low-valent tetrametallic compound 4 was gathered by hydrogenation of the phenyl-substituted precursor [Ta(η5-C5Me5)Ph(μ-S)]2, which proceeds through a stepwise hydrogenation process, disclosing the formation of the intermediate tetranuclear hydride sulfide [Ta2(η5-C5Me5)2(H)Ph(μ-S)(μ3-S)]2 (5). Extending our studies toward tantalum alkyl precursors containing functional groups susceptible to hydrogenation, such as the allyl-and benzyl-substituted compounds [Ta(η5-C5Me5)(η3-C3H5)(μ-S)]2 and [Ta(η5-C5Me5)(CH2Ph)(μ-S)]2 (2), enables alternative reaction pathways en route to the formation of 4. In the former case, the dimetallic system undergoes selective hydrogenation of the unsaturated allyl moiety, forming the asymmetric complex [{Ta(η5-C5Me5)(η3-C3H5)}(μ-S)2{Ta(η5-C5Me5)(C3H7)}] (6) with only one propyl fragment. Species 2, in addition to the hydrogenation of one benzyl fragment and concomitant toluene release, also undergoes partial hydrogenation and dearomatization of the phenyl ring on the vicinal benzyl unity to give a η5-cyclohexadienyl complex [Ta2(η5-C5Me5)2(μ-CH2C6H6)(μ-S)2] (7). The mechanistic implications of the latter hydrogenation process are discussed by means of DFT calculations.

Rare‐Earth Doped Configurational Entropy Stabilized High Entropy Spinel Oxide as an Efficient Anchoring/Catalyst Functional Interlayer for High‐Performance Lithium‐Sulfur Battery

AbstractLithium‐sulfur batteries (LSBs) are one of the most promising and potential modern‐day energy storage devices due to the low‐cost sulfur‐based cathode and remarkably high energy density (∼2600 Wh kg−1). However, the detrimental shuttle effect of lithium polysulfide (LiPS) and the sluggish electrochemical redox kinetics of lithium sulfide (Li2S) formation restrict its commercial viability. Herein, we design a novel transition metal‐rare earth high entropy oxide (TM‐RE HEO) Co0.08Mn0.08Ni0.08Fe1.96Mg0.08Nd0.01Gd0.01Sm0.01Pr0.01O4 as a polysulfide adsorbent and catalyst for the redox reactions of sulfur species in Li−S battery. TM‐RE HEO interlayer exhibits an excellent discharge capacity of 1146 mAh g−1 at 0.1 C rate, high rate capability, and reasonable long‐term cycling stability at 0.5 C rate with a low capacity decay of 0.08 % per cycle after 300 cycles. High degree of chemical confinement of soluble polysulfides, as demonstrated by the strong bonding between TM‐RE HEO and Li2S6, and expedited catalytic conversion to insoluble Li2S, result from strong polar catalytically active multiple metal sites and abundant oxygen vacancies. This work demonstrates the potential of high entropy oxide in developing high‐efficiency LSB technology.

Syntrophic Growth of Biomaibacter acetigenes Strain SP2 on Lactate and Glycerol

A moderately thermophilic Gram-positive chemo-organotrophic bacterium, strain SP2, was isolated by serial dilutions with crotonate and yeast extract as substrates from a butyrate-degrading methanogenic enrichment obtained from thermophilically digested sludge of the Kuryanoskaya wastewater treatment plant (Moscow, Russia). Cells of strain SP2 are spore-forming rods, sometimes occurring in short chains. The bacterium is an obligate anaerobe that grows at temperatures from 20 to 70 °C (55–60 °C optimum) within a pH range of 3.5–8 (7.5 optimum) and with NaCl concentrations of up to 2.5%. The strain utilized yeast extract and simple sugars as carbon and energy sources. Thiosulfate was used as an electron acceptor when grown on sucrose, resulting in the formation of hydrogen sulfide and the accumulation of elemental sulfur globules inside the cells. Strain SP2 is phylogenetically related to Biomaibacter acetigenes strain SK-G1T as revealed by comparison with the 16S rRNA gene (99.9% identity) and genome (ANI 99%, dDDH 90%) of both strains. It is interesting that strain SP2 was capable of syntrophic conversion of glycerol and lactate when co-cultivated with hydrogenotrophic methanogen, which was not previously shown for the SK-G1T type of strain. The isolation and in-depth study of new facultatively syntrophic microorganisms is important for wastewater treatment ecotechnologies due to their ability to switch to an alternative source of carbon and energy and therefore greater resistance to changing environmental conditions in bioreactors.

Occurrence of characteristic defects of grinding balls from rejects of continuously cast billets of rail steel

On the basis of metallographic studies, the authors determined the characteristic defects of grinding balls rolled from the rejects of continuously cast billets of K76F rail steel. Relationship of the presence of internal defects of the balls with their impact resistance was established. Defects in the form of internal cracks with accumulations of non-metallic inclusions in the area of their localization and flocks have the greatest impact on the reduction of balls impact resistance. Such defects are the cause of balls destruction during impact resistance tests in 62 and 17 % of cases, respectively. The effect of internal cracks without significant accumulations of non-metallic inclusions and quenching microcracks located along the boundaries of the phase interface was estimated at 12 and 9 %. The regularities and mechanism of influence of the rejects chemical composition of K76F rail steel billets on the probability of destruction of the balls produced from them during impact resistance tests were established. An increase in sulfur content in the billets of the studied rail steel reduces impact resistance of the balls produced from them, as it contributes to formation of non-plastic sulfides that concentrate in the area of internal cracks. An increase in hydrogen content in rail steel naturally contributes to an increase in probability of formation of the flocks, which significantly reduce the balls stability to shock loads. An increase in carbon content in the initial billets affects the increase in probability of destruction of K76F steel balls during copra tests. It is explained by formation of cementite-type carbides when carbon content corresponding to the eutectoid steel is reached. In general, the relative degree of influence of the K76F rail steel chemical composition on impact resistance of grinding balls is 48 %.

Metal Catalyst-Dependent Poisoning Effect of Organic Sulfur Species for the Hydroconversion of 5-Hydroxymethylfurfural

The transformation of 5-hydroxymethylfurfural (HMF) into ring-saturated furanics is a vital step in carbohydrate valorization. In this work, we report on the remarkable catalyst poisoning effect of numerous sulfur species for HMF hydroconversion. The presence of minor amounts of dimethyl sulfoxide (DMSO) affects ring-saturated product selectivity for the metal-catalyzed reactions using molecular hydrogen, whereas it fully deactivates catalytic transfer hydrogenation (CTH) in 2-propanol. The degree of poisoning correlates with the thermodynamic favorability of the metal sulfide formation. Reduced sulfur species (sulfide or thiol) are the ultimate metal poisoning agent. Their easy formation from more oxidized sulfur compounds explains the observed poisoning effect for such species. Here, the metal’s oxophilicity determines the catalysts’ behavior in the presence of oxidized sulfur species by forming (or not) poisoning sulfur–metal interactions. To overcome the sulfur poisoning, we propose DMSO removal with organic solvent extraction and catalyst oxidation post-treatment. These findings pinpoint the crucial, though overlooked, role of the biobased HMF purity for reductive catalytic studies. We provide a deeper understanding of the noble metal poisoning by sulfur from different origins and oxidation states that may be present during HMF hydroconversion.

Hot Corrosion Behavior of Inconel 625 in Na2SO4 and V2O5 Molten Salt System

This study aimed to examine the corrosion behavior of Inconel 625 in a molten salt system of sodium sulfate and vanadium pentoxide at varying temperatures and durations. The corrosion products, microstructure, and element distribution of hot extruded Inconel in Na2SO4 and V2O5 molten salt systems were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) analyses. This study demonstrates that corrosion of the alloy increases with time at a constant temperature. During the initial stage of corrosion, the surface of the alloy is primarily composed of a dense oxide layer consisting of Cr2O3 and NiO. However, after exposure to the salt bath for 24 h, a chemical reaction occurs between the alloy and vanadium (V), resulting in the formation of CrVO4 and Ni3V2O8. Furthermore, the intrusion of sulfur (S) element into the matrix leads to the formation of internal sulfides, including Ni-, Cr-, and Mo-based sulfides, which accelerate intergranular and intracrystalline corrosion. As the corrosion temperature rises, the surface microstructure of the corrosion layer transforms from powder to salt particles and then to massive particles. The corrosion products exhibit a clear stratification, while the alloy undergoes simultaneous oxidation and vulcanization processes.

Nickel Isotope Fractionation During Magmatic Differentiation

AbstractThe behavior of nickel (Ni) isotopes during magmatic differentiation is not adequately explored. Here, we find that tholeiitic rocks in the Kīlauea Iki (KI) lava lake, Hawai'i, show progressively lighter Ni isotopic compositions with increasing magmatic differentiation, whereas calc‐alkaline rocks from the thick Kamchatka arc (30–45 km), located at the convergent boundary of the Eurasian and Pacific plates show increasing Ni isotope values as MgO and Ni decrease. Forty‐three global intermediate‐felsic continental igneous rocks analyzed in this study display large Ni isotopic variations, with the Eoarchean samples having light Ni isotopic compositions that fall in the trend defined by the KI lavas, and the post‐Eoarchean samples showing systematically heavier Ni isotopic compositions overlapping those of Kamchatka arc rocks. The isotopic dichotomy results from the crystallization of isotopically heavy magnetite during low‐pressure differentiation of KI lavas, whereas the participation of sulfide separation that removes isotopically light Ni during high‐pressure differentiation of magmas traversing thick continental crust. Combined with Rhyolite‐MELTS and sulfur concentration at sulfide saturation simulations, we demonstrate that the Ni isotope fractionation during magmatic differentiation is mainly controlled by the tempo of magnetite crystallization and sulfide formation, which is a function of pressure, oxygen fugacity, and water activity. High‐pressure calc‐alkaline differentiation usually suppresses magnetite crystallization while stabilizing sulfide, leading to heavy Ni isotopic compositions for the evolved magmas, significantly deviating from the low‐pressure fractionation trend seen in the KI lavas. Ni isotopes can be used in the future as a tracer of magmatic differentiation and processes of continent formation and differentiation.

Operational characteristics of steel structures of long term service life

Introduction. The process of natural ageing of metal structures under influence of long-term mechanical loading and environmental factors, leads to changes in physical, chemical and mechanical properties of metals. Nowadays, a considerable number of industrial and civil buildings with metal structures having service life in the range of 30 to 120 years are in operation all over the world. Most of the scientific work on the aging of metals has been done in mechanical engineering, wear resistance of pipelines, machine parts, etc. In this connection, undoubtedly, the development of scientific direction connected with the study of peculiarities of changes in the structure, physical and mechanical characteristics of steel structures of a long period of their operation becomes actual. This is caused by the necessity of safe functioning of these constructions during the whole service life of a building or a structure, and also by the necessity of prediction of their behavior in fire and fire-resistant conditions.
 
 Materials and methods. The results of research concerning a steel structure specimen with a service life of 86 years have been presented. A set of experimental research methods was used: optical emission method to determine the chemical composition; metallographic method to study the microstructure, identify material defects and evaluate non-metallic inclusions in the structure of the sample; static tensile tests to determine the quality and performance characteristics of materials, in particular strength and ductility.
 
 Results. The results show that the chemical composition of the steel in general remains essentially unchanged during operation. A comparative analysis of the microstructure of steel St3 and steel with a lifetime of 86 years indicates slight changes in the structure related to the presence of multi-grain and fragmentary restructuring of structural elements, which may be indicative of the beginning of the destruction of the structure and reduce the strength characteristics of steel. The steel structure revealed the presence of non-metallic inclusions (point oxides and manganese sulfides) which serve as stress and strain concentrators in the matrix, causing local material failure at lower average strain, which may also lead to a reduction in the tensile strength of steel structures. According to the results of metallographic analysis insignificant transformations in the structure characterized by a change in perlite morphology, the presence of heterogeneity as well as the presence of non-metallic inclusions in the form of point oxides and manganese sulfides can be demonstrated. The significant influence of uniform and ulcerous corrosion process flowing into corrosion cracking going deep into the base metal on mechanical characteristics of steel is revealed. The obtained values of operational characteristics of the considered steel structure, having surface corrosion damages shows the lowering of ultimate strength by 15 %, yield strength by 10 % and relative elongation by 12 % from the normative values.
 
 Conclusions. Characteristic changes in the structure of steel with a long service life have been established. A comparative analysis of the results of static tensile tests on specimens from sections of the structure without corrosion damage and specimens cut out at the section acutely affected by corrosion has been made. The influence of corrosion process on reduction of operational characteristics of steel structure is shown. It is supposed that corrosion in course of time turns to a more aggressive type from even corrosion to corrosion cracking and spreads deep into the base metal which leads to considerable loss of mechanical properties of steel structures and to reduction of their fire-resistance limits.

Agitation Leaching Behavior of Copper–Cobalt Oxide Ores from the Democratic Republic of the Congo

Agitation leaching is a promising technology in hydrometallurgy for treating copper–cobalt oxide ores. In this work, the behavior of oxide ores containing around 2.3% Cu and 0.3% Co received from Congo was investigated for varying particle size, acidity, pulp density, temperature, leaching time, and reduction potential. XRD, optical microscopy (OM), and ICP-OES methods were used to examine the chemical composition, morphology, and metal content of the samples. The copper and cobalt recovery reached 88.2% and 82.5%, respectively, at room temperature, with a leaching time of 4 h, a pulp density of 33%, an acidity of 178 g/L, and no reductant. The Cu and Co remaining in the leaching residue were found to be in their sulfide forms and coated with dense and fine calcium sulfate. To improve the metal recovery, a combination of flotation and agitation leaching of the flotation tailings method was adopted, after which the Cu and Co recovery reached 96.6% and 86.0%, respectively.

Structure-property relationship of zeolite-Y/cubic ZnS nanohybrid material and its utilization for gaseous phase mercury removal

Zinc acetate dihydrate and thiourea based metal sulfide was synthesized and used to develop zeolite-ZnS (ZY-ZnS) nanohybrid material by using sonication process, solvothermal method and heat treatment process. The sulfur atom in thiourea is involved in formation of metal sulfide and ethylene glycol was used as solvents in the solvothermal method. The structure of the nanohybrid material was analyzed by Raman spectroscopy, FTIR, XRD and XPS. Raman spectra confirmed the presence of 4, 6- membered rings of zeolite and polar modes A1 and E1 and nonpolar mode E2 of ZnS nanoparticles. The morphology of the nanohybrid material was analyzed by TEM and SEM analysis. The uniform distribution of ZnS in the zeolite matrix was observed in TEM and SEM morphology. The spherical aggregates ZnS crystals size between 100 and 200 nm were observed. Cubical morphology was observed in pure zeolite samples in the range of 400 nm−500 nm. The X-ray photoelectron spectroscopy analysis was used to confirm the metal-sulfide species in the hybrid material. Mercury adsorption (elemental (Hg°)) in the vapor phase follows both pseudo-first-order and pseudo-second-order kinetic models. Kinetic study shows that the mercury adsorption on the zeolite-ZnS nanohybrid adsorbent was mostly regulated by the chemisorption. Vapor phase mercury adsorption capacity of zeolite-Y (ZY) and zeolite-ZnS (ZY-ZnS), is 2295 and 3461 µg/g at 180 °C, respectively. In ZY and ZY-ZnS the intraparticle diffusion rates were 86.1 and 141.2 μg/gmin-1/2, respectively. The higher intraparticle diffusion rate observed in ZY-ZnS confirm the uniformly decorated ZnS nano particles in ZY-ZnS nanohybrid material.

Flame Aerosol Synthesis of Metal Sulfides at High Temperature in Oxygen Lean Atmosphere.

The development of a novel reactive spray technology based on the well-known gas phase metal oxide synthesis route provides innumerable opportunities for the production of non-oxide nanoparticles. Among these materials, metal sulfides are expected to have a high impact especially in the development of electrochemical and photochemical high surface area materials. As a proof-of-principle, MnS, CoS, Cu2 S, ZnS, Ag2 S, In2 S3 , SnS, and Bi2 S3 were synthesized in an O2 -lean and sulfur-rich environment. In addition, the formation of Cu2 S in a single droplet combustion experiment, is reported. The multi-scale approach combining flame sprays with single droplet combustion is expected to pave the way towards a fundamental understanding of the gas phase formation of metal sulfides in the future. The knowledge acquired will open the possibility for the development of a next generation gas-phase technology facilitating the scalable synthesis of functional binary/ternary metal sulfides. This article is protected by copyright. All rights reserved.

In Situ Gravimetric Probing of Copper Sulfide Formation on the Counter Electrode for Quantum Dot Sensitized Solar Cells

Copper sulfide is a classical counter electrode (CE) catalytic material for the high catalytic activity of polysulfide in quantum dot-sensitized solar cells (QDSSCs). Actually, copper sulfide is a complicated compound. Different preparation methods will lead to the difference in the morphology and structure of copper sulfide, which has a profound impact on its catalytic activity. However, the formation mechanism and electrochemical properties of copper sulfide are rarely reported in the field of QDSSCs. Herein, we report an approach to obtain a high-stability counter electrode material by the electrochemical synthesis in sodium sulfide solution. The in situ electrochemical quartz crystal microbalance (EQCM) method was also employed to reveal the detailed transformation mechanism of copper vulcanized into copper sulfide during cyclic voltammetry in sodium sulfide solution. According to the calculation results of mpe theory, the formation of copper sulfide is accompanied by side reactions such as the conversion of polysulfide ions and water oxidation. Copper sulfide was proven to be a copper-rich phase by X-ray photoelectron spectroscopy (XPS) and other characterization methods. The photoconversion and stability of QDSSCs were studied using CdSe QD as the sensitizing material. The results show that the performance of copper sulfide prepared by this working method is better than the CE prepared by chemical bath deposition (CBD), and the replicability of photoelectric conversion efficiency (PCE) is better than CBD-CE. This work has theoretical significance to reveal the complex formation mechanism, electrochemical process mechanism, and working mechanism of copper sulfide in QDSSCs.

Tin sulfides and cadmium sulfide mixture in montmorillonite with enhanced visible-light photocatalytic activity

In situ formation of tin sulfide (SnS) and cadmium sulfide (CdS) mixture in montmorillonite was carried out by the reaction between an aqueous dispersion of Sn2+- and Cd2+-montmorillonite and an aqueous solution of S2− (from Na2S). The effects of Sn2+ / Cd2+ molar ratios were examined. The appearance of two diffraction peaks (d001 = 1.3 and 1.4 nm) and/or the large mismatch (8%) of SnS and CdS lattices were attributed to the possible formation of SnS and CdS in two different interlayer spaces (segregation) of montmorillonite. The blue shifts of the absorption onset relating to the expansion of band gap energy, and the emission band as well as the increase of emission intensity of the intercalated SnS and CdS mixture were observed with increasing SnS / CdS molar ratio. The photodegradation of rhodamine 6G solution was achieved within 360 min by using the product, which has the molar ratio of Sn / Cd = 3:1. The photocatalytic process followed pseudo-first-order kinetic with a rate constant of 0.011 min−1. The scavenger test indicated that superoxide radical (O2•-) was the predominant species involved in the photocatalytic process. This result represented an important role of montmorillonite and the heterostructures of SnS and CdS in tailoring the photocatalytic properties.