Conformal sulfidation of HKUST-1 for constructing porous Cu2S/CuO octahedrons realizing highly sensitive non-enzymatic glucose detection.

Metal-organic frameworks (MOFs) are believed to be promising precursors for constructing novel and efficient catalysts for glucose sensing. Herein, HKUST-1 precursors are first fabricated using a one-pot hydrothermal approach, and then HKUST-1 is converted into porous Cu2S/CuO octahedrons through conformal sulfidation with the help of OH-ions. The as-obtained Cu2S/CuO composite can provide rich electrochemical active sites and promoted electric transfer kinetics. Benefiting from these combined merits, the as-fabricated Cu2S/CuO composite is confirmed to be a high-performance catalyst, with high sensitivities of 8269.45 and 4140.82µA mM-1cm-2in the corresponding ranges of 0.05 ∼ 0.6 mM and 0.6 ∼ 1.2 mM, respectively. Moreover, the as-prepared electrode materials possess good anti-interference ability, reproducibility and long-term stability. This work opens up new avenues for the design and preparation of transition metal sulfide composites.

Sulfidation of Cd-Sch during the microbial sulfate reduction: Nanoscale redistribution of Cd.

Schwertmannite (Sch) is found in environments abundant in iron and sulfate. Microorganisms that utilize iron or sulfate can induce the phase transition of Schwertmannite, consequently leading to the redistribution of coexisting pollutants. However, the impact of the molar ratio of sulfate to iron (S/Fe) on the microbial-mediated transformation of Schwertmannite and its implications for the fate of cadmium (Cd) have not been elucidated. In this study, we examined how S/Fe influenced mineral transformation and the fate of Cd during microbial reduction of Cd-loaded Schwertmannite by Desulfovibrio vulgaris. Our findings revealed that an increase in the S/Fe ratio facilitated sulfate-reducing bacteria (SRB) in mitigating the toxicity of Cd, thereby expediting the generation of sulfide (S(-II)) and subsequently triggering mineral phase transformation. As the S/Fe ratio increased, the predominant minerals in the system transitioned from prismatic-cluster vivianite to rose-shaped mackinawite. The Cd phase and distribution underwent corresponding alterations. Cd primarily existed in its oxidizable state, with its distribution being directly linked not only to FeS content but also showing a robust correlation with phosphorus. The coexistence of vivianite and FeS minerals proved to be more favorable for Cd immobilization. These findings have significant implications for understanding the biogeochemistry of iron (oxyhydr)oxides and Cd fate in anaerobic environments.

Expedient Synthesis of Alkyl and Aryl Thioethers Using Xanthates as Thiol-Free Reagents.

Thioethers are critical in the fields of pharmaceuticals and organic synthesis, but most of the methods for synthesis alkyl thioethers employ foul-smelling thiols as starting materials or generate them as by-products. Additionally, most thiols are air-sensitive and are easily oxidized to produce disulfides under atmospheric conditions; thus, a novel method for synthesizing thioethers is necessary. This paper reports a simple, effective, green method for synthesizing dialkyl or alkyl aryl thioether derivatives using odorless, stable, low-cost ROCS2K as a thiol surrogate. This transformation offers a broad substrate scope and good functional group tolerance with excellent selectivity. The reaction likely proceeds via xanthate intermediates, which can be readily generated via the nucleophilic substitution of alkyl halides or aryl halides with ROCS2K under transition-metal-free and base-free conditions.

Mastering Surface Sulfidation of MnP-MnO2 Heterostructure to Facilitate Efficient Polysulfide Conversion in Li─S Batteries.

The development of lithium-sulfur (Li─S) batteries has been hampered by the shuttling effect of lithium polysulfides (LiPSs). An effective method to address this issue is to use an electrocatalyst to accelerate the catalytic conversion of LiPSs. In this study, heterogeneous MnP-MnO2 nanoparticles are uniformly synthesized and embedded in porous carbon (MnP-MnO2/C) as core catalysts to improve the reaction kinetics of LiPSs. In situ characterization and density functional theory (DFT) calculations confirm that the MnP-MnO2 heterostructure undergo surface sulfidation during the charge/discharge process, forming the MnS2 phase. Surface sulfidation of the MnP-MnO2 heterostructure catalyst significantly accelerated the SRR and Li2S activation, effectively inhibiting the LiPSs shuttling effect. Consequently, the MnP-MnO2/C@S cathode achieves outstanding rate performance (10 C, 500 mAh g-1) and ultrahigh cycling stability (0.017% decay rate per cycle for 2000 cycles at 5 C). A pouch cell with MnP-MnO2/C@S cathode delivers a high energy density of 429 Wh kg-1. This study may provide a new approach to investigating the surface sulfidation of electrocatalysts, which is valuable for advancing high-energy-density Li-S batteries.

Mechanism of WS2 Nanotube Formation Revealed by in Situ/ex Situ Imaging.

Multiwall WS2 nanotubes have been synthesized from W18O49 nanowhiskers in substantial amounts for more than a decade. The established growth model is based on the "surface-inward" mechanism, whereby the high-temperature reaction with H2S starts on the nanowhisker surface, and the oxide-to-sulfide conversion progresses inward until hollow-core multiwall WS2 nanotubes are obtained. In the present work, an upgraded in situ SEM µReactor with H2 and H2S sources has been conceived to study the growth mechanism in detail. A hitherto undescribed growth mechanism, named "receding oxide core", which complements the "surface-inward" model, is observed and kinetically evaluated. Initially, the nanowhisker is passivated by several WS2 layers via the surface-inward reaction. At this point, the diffusion of H2S through the already existing outer layers becomes exceedingly sluggish, and the surface-inward reaction is slowed down appreciably. Subsequently, the tungsten suboxide core is anisotropically volatilized within the core close to its tips. The oxide vapors within the core lead to its partial out-diffusion, partially forming a cavity that expands with reaction time. Additionally, the oxide vapors react with the internalized H2S gas, forming fresh WS2 layers in the cavity of the nascent nanotube. The rate of the receding oxide core mode increases with temperatures above 900 °C. The growth of nanotubes in the atmospheric pressure flow reactor is carried out as well, showing that the proposed growth model (receding oxide core) is also relevant under regular reaction parameters. The current study comprehensively explains the WS2 nanotube growth mechanism, combining the known model with contemporary insight.

Integrated influence of sulfide modification on the reactivity of nanoscale zero-valent iron towards decabromodiphenyl ether under an electromagnetic field.

Individual application of sulfide modification and electromagnetic field (EMF) can enhance the reactivity of nanoscale zero-valent iron (nZVI), yet the potential of both in combination is not clear. This work found that the reactivity of nZVI towards decabromodiphenyl ether was significantly enhanced by the combined effect of sulfidation and EMF. The specific reaction rate constant of nZVI increased by 7 to 10 times. A series of characterization results revealed that the sulfidation level not only affects the inherent reactivity but also the magnetic-induced heating (MIH) and corrosion (MIC) of nZVI. These collectively influence the degradation efficiency of nZVI under EMF. Sulfidation generally diminished the MIH effect. The low degree of sulfidation (S/Fe = 0.1) slightly reduced the MIC effect by 21.4%. However, the high degree of sulfidation (S/Fe = 0.4) led to significantly enhanced MIC effect by 107.1%. For S/Fe = 0.1 and 0.4, the overall enhancement in the reactivity resulting from EMF was alternately dominated by the contributions of MIH and MIC. This work provides valuable insights into the MIH and MIC effects about the sulfidation level of nZVI, which is needed for further exploration and optimization of this combined technology.

Protracted metallogenic and magmatic evolution of the Kirazli epithermal Au-Ag and porphyry Cu deposits, Biga Peninsula, NW Turkey: evidence from zircon U-Pb, muscovite 40Ar/39Ar, and molybdenite Re-Os geochronology.

The Kirazli deposit is located at the center of the Biga Peninsula metallogenic province, in a geological setting characterized by an extensional tectonic environment. A NNW-SSE trending high-sulfidation (HS) orebody with a total reserve of 33.86 Mt @ 0.69 g/t Au and 9.42 g/t Ag lies beneath the Kirazli Main zone. A porphyry Cu orebody hosted by Eocene intrusive and volcanic rocks has been intersected by drilling within its vicinity. The HS epithermal deposit is hosted by a partly silicified and brecciated Oligocene volcanic and volcaniclastic sequence consisting mainly of basaltic andesite lava flow and lithic/crystal tuff. Lithogeochemistry and zircon U-Pb radiometric ages allow us to distinguish three distinct high-K calc-alkaline magmatic events at ca. 41, 38, and 32 Ma, sourced by metasomatized mantle melts, which have interacted with the crust during their ascent. Porphyry Cu mineralization took place at 36.7 ± 0.4 Ma (muscovite 40Ar/39Ar age) with subsequent re-opening and base metal deposition. Crosscutting quartz-pyrite-molybdenite veins were emplaced at 33.6 ± 0.2 Ma (molybdenite Re-Os age), and followed by the HS epithermal Au-Ag event at ca. 31 Ma, based on a previous study. Our radiometric data indicate that the Kirazli deposit has recorded a long-lasting Cenozoic magmatic and metallogenic evolution during about 10 Myr. Our study demonstrates that successive, independent, and overprinting, but genetically unrelated, HS epithermal precious metal, hydrothermal Mo, base metal, and porphyry Cu systems have been active at the same location during protracted extensional tectonics of the Biga Peninsula. Supplementary Information: The online version contains supplementary material available at 10.1007/s00126-023-01235-2.

Sulfidation-Induced Surface Local Electronic and Atomic Structures in a Silver Catalyst Enables Silicon Photocathode for Selective and Efficient Photoelectrochemical CO2 Reduction.

Converting CO2 to value-added chemicals through a photoelectrochemical (PEC) system is a creative approach toward renewable energy utilization and storage. However, the rational design of appropriate catalysts while being effectively integrated with semiconductor photoelectrodes remains a considerable challenge for achieving single-carbon products with high efficiency. Herein, we demonstrate a novel sulfidation-induced strategy for in situ grown sulfide-derived Ag nanowires on a Si photocathode (denoted as SD-Ag/Si) based on the standard crystalline Si solar cells. Such an exquisite design of the SD-Ag/Si photocathode not only provides a large electrochemically active surface area but also endows abundant active sites of Ag2S/Ag interfaces and high-index Ag facets for PEC CO production. The optimized SD-Ag/Si photocathode displays an ideal CO Faradic efficiency of 95.2% and an onset potential of +0.26 V versus the reversible hydrogen electrode, ascribed to the sulfidation-induced synergistic effect of the surface atomic arrangement and electronic structure in Ag catalysts that promote charge transfer, facilitate CO2 adsorption and activation, and suppress hydrogen evolution reaction. This sulfidation-induced strategy represents a scalable approach for designing high-performance catalysts for electrochemical and PEC devices with efficient CO2 utilization.

Carboxymethyl cellulose stabilization induced changes in particle characteristics and dechlorination efficiency of sulfidated nanoscale zero-valent iron.

Polymer stabilization, exemplified by carboxymethyl cellulose (CMC), has demonstrated effectiveness in enhancing the transport of nanoscale zero-valent iron (nZVI). And, sulfidation is recognized for enhancing the reactivity and selectivity of nZVI in dechlorination processes. The influence of polymer stabilization on sulfidated nZVI (S-nZVI) with various sulfur precursors remains unclear. In this study, CMC-stabilized S-nZVI (CMC-S-nZVI) was synthesized using three distinct sulfur precursors (S2-, S2O42-, and S2O32-) through one-step approach. The antioxidant properties of CMC significantly elevated the concentration of reduced sulfur species (S2-) on CMC-S-nZVIs, marking a 3.1-7.0-fold increase compared to S-nZVIs. The rate of trichloroethylene degradation (km) by CMC-S-nZVIs was observed to be 2.2-9.0 times higher than that achieved by their non-stabilized counterparts. Among the three CMC-S-nZVIs, CMC-S-nZVINa2S exhibited the highest km. Interesting, while the electron efficiency of CMC-S-nZVIs surged by 7.9-12 times relative to nZVI, it experienced a reduction of 7.0-34% when compared with S-nZVIs. This phenomenon is attributed to the increased hydrophilicity of S-nZVI particles due to CMC stabilization, which inadvertently promotes the hydrogen evolution reaction (HER). In conclusion, the findings of this study underscores the impact of CMC stabilization on the properties and dechlorination performance of S-nZVI sulfidated using different sulfur precursors, offering guidance for engineering CMC-S-nZVIs with desirable properties for contaminated groundwater remediation.

In situ characterization of silver nanoparticles sulfidation processes in aquatic solution by hollow fiber flow-field flow fractionation coupled with ICP-QQQ.

The sulfidation is considered as one of the most important environmental transformation processes of silver nanoparticles (AgNPs), which affects their transport, uptake and toxicity. Herein, based on the hollow fiber flow-field flow fractionation coupled with triple quadrupole inductively coupled plasma mass spectrometry (HF5-ICP-QQQ), we developed an efficient approach to accurately characterize the sulfidation process of AgNPs in aquatic solutions. HF5 could efficiently remove interferential ions and separate nanoparticles with different sizes online, and ICP-QQQ could accurately detect S element through monitoring 32S16O+ in mass shift mode. By the proposed method, two kinds of AgNPs, citrate-coated AgNPs and PVP-coated AgNPs, were selected as models to trace their transfer behaviors during the sulfidation. The results showed once AgNPs were exposed to Na2S solution, the overlapping fractograms of 32S16O+ and 107Ag+ were rapidly detected by HF5-ICP-QQQ to indicate the co-presence of Ag and S, and thus confirming the production of Ag2S and AgNPs underwent a rapid sulfidation process. There were substantial differences in the influence of the two coated agents on the stability of the particles under the conditions examined. In the presence of sulfide, PVP-coated AgNPs could maintain initial size distribution with higher stability, while the size distribution of citrate-coated AgNPs changed considerably. The developed HF5-ICP-QQQ method provides a reliable tool to identify and characterize the transformation process of AgNPs in aquatic solution, which contributed to a deeper understanding of the environmental fate and behavior of AgNPs with different coating.

Ultralong Nanowires of Cadmium Phosphate Hydroxide Synthesized Using a Cadmium Oleate Precursor Hydrothermal Method and Sulfidation Conversion to Ultralong CdS Nanowires.

Ultralong nanowires with ultrahigh aspect ratios exhibit high flexibility, and they are promising for applications in various fields. Herein, a cadmium oleate precursor hydrothermal method is developed for the synthesis of ultralong nanowires of cadmium phosphate hydroxide. In this method, water-soluble cadmium salt is used as the cadmium source, water-soluble phosphate is used as the phosphorus source, and sodium oleate is adopted as a reactant to form cadmium oleate precursor and as a structure-directing agent. By using this method, ultralong nanowires of cadmium phosphate hydroxide are successfully synthesized using CdCl2, sodium oleate, and NaH2PO4 as reactants in an aqueous solution by hydrothermal treatment at 180 °C for 24 h. In addition, a new type of flexible fire-resistant inorganic paper with good electrical insulation performance is fabricated using ultralong nanowires of cadmium phosphate hydroxide. As an example of the extended application of this synthetic method, ultralong nanowires of cadmium phosphate hydroxide can be converted to ultralong CdS nanowires through a convenient sulfidation reaction. In this way, ultralong CdS nanowires are successfully synthesized by simple sulfidation of ultralong nanowires of cadmium phosphate hydroxide under mild conditions. The as-prepared ultralong nanowires of cadmium phosphate hydroxide are promising for applications as the precursors and templates for synthesizing other inorganic ultralong nanowires and have wide applications in various fields.

ZIF-derived sulfides with tremella-like core-shell structure for high performance supercapacitors.

Metal-organic frameworks (MOFs) have emerged as promising active electrode materials in supercapacitors for its controllable porous structure and excellent physio-chemical properties. However, the poor conductivities keep it from achieving its full capacitance potential, which greatly limits its practical application. Here, a facile pathway is reported to fabricate the GO/Ni2ZnS4@NiCo2S4 composite with large specific surface area and favorable electrical conductivity. Thanks to the novel tremella-like core-shell structure and high-efficient synergistic effects among multi-components, the designed GO/Ni2ZnS4@NiCo2S4 electrode shows a high specific capacitance of 2284 F/g at 1 A/g. Furthermore, the asymmetric supercapacitor fabricated by coupling GO/Ni2ZnS4@NiCo2S4 positive electrode with biological carbon negative electrode achieves a remarkable energy density of 120 Wh kg-1 at a power density of 750 W kg-1.

Enhanced Biogenic Sulfidation of Zero-Valent Iron in Columns: Implications for Promoting Dechlorination in Permeable Reactive Barriers.

Biogenic sulfidation of zero-valent iron (ZVI) using sulfate reducing bacteria (SRB) has shown enhanced dechlorination rates comparable to those produced by chemical sulfidation. However, controlling and sustaining biogenic sulfidation to enhance in situ dechlorination are poorly understood. Detailed interactions between SRB and ZVI were examined for 4 months in column experiments under enhanced biogenic sulfidation conditions. SRB proliferation and changes in ZVI surface properties were characterized along the flow paths. The results show that ZVI can stimulate SRB activity by removing excessive free sulfide (S2-), in addition to lowering reduction potential. ZVI also hinders downgradient movement of SRB via electrostatic repulsion, restricting SRB presence near the upgradient interface. Dissolved organic carbon (e.g., >2.2 mM) was essential for intense biogenic sulfidation in ZVI columns. The presence of SRB in the upgradient zone appeared to promote the formation of iron polysulfides. Biogenic FeSx deposition increased the S content on ZVI surfaces ∼3-fold, corresponding to 3-fold and 2-fold improvements in the trichloroethylene degradation rate and electron efficiency in batch tests. Elucidation of SRB and ZVI interactions enhances sustained sulfidation in ZVI permeable reactive barrier.

Coupling of Dissolved Organic Matter Molecular Fractionation with Iron and Sulfur Transformations during Sulfidation-Reoxidation Cycling.

Iron (oxyhydr)oxides and organic matter (OM) are intimately associated in natural environments, and their fate might be linked to sulfur during sulfidation-reoxidation cycling. However, the coupling of DOM molecular fractionation with Fe and S transformations following a full sulfidation-reoxidation cycle remains poorly understood. Here, we reacted Fh and Fh-OM associations with S(-II) anaerobically and then exposed the sulfidic systems to air. S(-II) preferentially reacted with Fh to form inorganic S (e.g., mackinawite, S0, and S22-) over being incorporated into OM as organic S and therefore indirectly affected OM fate by altering Fe speciation. Fh sulfidation was inhibited by associated OM, and the main secondary Fe species were mackinawite, Fe(II)-OM compounds, and lepidocrocite. Concomitantly, organic molecules high in unsaturation, aromaticity, and molecular weight were detached from solid-phase Fe species due to their lower affinities for secondary Fe species than for Fh. During the reoxidation stage, the previously formed Fe(II) species were reoxidized to Fh with a stronger aggregation, which recaptured formerly released OM with higher selectivity. Additionally, •OH was generated from Fe(II) oxygenation and degraded a portion of the DOM molecules. Overall, these results have significant implications for Fe, C, and S cycling in S-rich environments characterized by oscillating redox conditions.

Submillimeter-Long WS2 Nanotubes: The Pathway to Inorganic Buckypaper.

WS2 nanotubes present many new technologies under development, including reinforced biocompatible polymers, membranes, photovoltaic-based memories, ferroelectric devices, etc. These technologies depend on the aspect ratio (length/diameter) of the nanotubes, which was limited to 100 or so. A new synthetic technique is presented, resulting in WS2 nanotubes a few hundred micrometers long and diameters below 50 nm (aspect ratios of 2000-5000) in high yields. Preliminary investigation into the mechanistic aspects of the two-step synthesis reveals that W5O14 nanowhisker intermediates are formed in the first step of the reaction instead of the ubiquitous W18O49 nanowhiskers used in the previous syntheses. The electrical and photoluminescence properties of the long nanotubes were studied. WS2 nanotube-based paper-like material was prepared via a wet-laying process, which could not be realized with the 10 µm long WS2 nanotubes. Ultrafiltration of gold nanoparticles using the nanotube-paper membrane was demonstrated.

Dissolution Potential of Elemental Mercury in the Presence of Bisulfide and Implications for Mobilization.

Liquid elemental mercury (Hg0L) pollution can remain in soils for decades and, over time, will undergo corrosion, a process in which the droplet surface oxidizes soil constituents to form more reactive phases, such as mercury oxide (HgO). While these reactive coatings may enhance Hg migration in the subsurface, little is known about the transformation potential of corroded Hg0L in the presence of reduced inorganic sulfur species to form sparingly soluble HgS particles, a process that enables the long-term sequestration of mercury in soils and generally reduces its mobility and bioavailability. In this study, we investigated the dissolution of corroded Hg0L in the presence of sulfide by quantifying rates of aqueous Hg release from corroded Hg0L droplets under different sulfide concentrations (expressed as the S:Hg molar ratio). For droplets corroded in ambient air, no differences in soluble Hg release were observed among all sulfide exposure levels (S:Hg mole ratios ranging from 10-4 to 10). However, for droplets oxidized in the presence of a more reactive oxidant (hydrogen peroxide, H2O2), we observed a 10- to 25-fold increase in dissolved Hg when the oxidized droplets were exposed to low sulfide concentrations (S:Hg ratios from 10-4 to 10-1) relative to droplets exposed to high sulfide concentrations. These results suggest two critical factors that dictate the release of soluble Hg from Hg0L in the presence of sulfide: the extent of surface corrosion of the Hg0L droplet and sufficient sulfide concentration for the formation of HgS solids. The mobilization of Hg0L in porous media, therefore, largely depends on aging conditions in the subsurface and chemical reactivity at the Hg0L droplet interface.

Enhanced arsenic(III) sequestration via sulfidated zero-valent iron in aerobic conditions: Adsorption and oxidation coupling processes.

Sulfidated zero-valent iron (S-ZVI) has shown significant potential for the removal of arsenic(III). However, little attention has been paid to the mechanism of As(III) sequestration enhancement and how the phase transformation for S-ZVI strengthens this process in aerobic conditions. In this work, sulfidated ZVI was created by ball-milling (S-ZVIbm) and liquid-mixing (S-ZVIlm) of ZVI with elemental sulfur(S0) to investigate the performance and mechanisms of As(III) sequestration in air-saturated water. Sulfidation was found to significantly enhance the As(III) removal rate constant, which was 2.8 âˆ¼ 6.7 times (S-ZVIbm) and 3.1 âˆ¼ 17.1 times (S-ZVIlm) higher than that without sulfidation. FeS was identified as the predominant sulfur species in the S-ZVI samples using S K-edge XANES spectra. The enhanced electron transfer and ZVI corrosion after sulfidation were verified via electrochemical tests. XANES and Mössbauer spectra suggested that lepidocrocite(γ-FeOOH) was the predominant corrosion product generated on the ZVI surface with the presence of oxygen, and DFT calculations further confirmed the improved performance of γ-FeOOH for As(III) sequestration. Besides, As(III) oxidation occurred dominantly on the heterogeneous surface rather than in solution, and the As(III) sequestration pathway of adsorption followed by oxidation was proposed. This study provides new insight into the enhanced As(III) sequestration by S-ZVI in aerobic conditions.

Influence of humate on the degradation of chloramphenicol by sulfidated ferrihydrite under dynamic anoxic/oxic environments: A combined DFT calculation and experimental study.

Sulfidation of ferrihydrite is known to affect the degradation of contaminants, but little was known about the role of natural organic matter (NOM) in antibiotics degradation by sufidated ferrihydrite under redox-dynamic conditions. Here, a typical antibiotic (i.e., chloramphenicol (CAP)) was chosen to investigate how it redistributed when ferrihydrite reacted with reductive dissolved sulfide (S(-II)dis) in the presence of humate (HA) under dynamic anoxic/oxic environments. In anoxic environments, HA enhanced CAP reduction via dichlorination or decarboxylation by sufidated ferrihydrite in the low concentration of S(-II), while HA inhibited CAP reduction in the high concentration of S(-II) by the contribution of S(-II) and surface-bound Fe(II) (Fe(II)adsorbed). When the conditions transited from anoxic to oxic, remaining CAP molecules in solutions continued undergoing oxidative degradation to form the succinic acid, hexanedioic acid, CO2, and H2O by the attack of ·OH. Meantime, HA was adsorbed to ferrihydrite to block autocatalytic Fe(II) oxidation, which inhibited the generation of ·OH under oxic conditions. Additionally, from the density function theory (DFT) calculation and intermediate products analysis obtained from HPLC-MS/MS, two oxidative degradation pathways of CAP during the oxidation of sulfidated ferrihydrite have been proposed. Collectively, the framework elucidated different roles of HA in CAP elimination and environmental behavior of ferrihydrite when exposed to the S(-II) under the dynamic redox conditions.

Closed-loop recycling of spent lithium-ion batteries based on selective sulfidation: An unconventional approach.

The facile recycling of spent lithium-ion batteries (LIBs) has attracted considerable attention because of its great importance to environmental protection and resource utilization. A novel process is developed for cyclic utilization of spent LiNixCoyMnzO2 (NCM) batteries. The spent NCM was converted into water-soluble Li2CO3, acid-dissolved MnO, and nickel-cobalt sulfides through selective sulfidation, based on roasting condition optimization and thermodynamic calculation. More than 98 % of lithium is extracted preferentially from calcined NCM through water leaching, and over 99 % of manganese is extracted selectively from water leaching residue with H2SO4 solution of 0.4 mol/L in the absence of additional reductant. The nickel and cobalt sulfides were concentrated into the leaching residue without metal impurities. The obtained Li2CO3, MnSO4, and nickel-cobalt sulfides can be regenerated as new NCM, showing good electrochemical performance, and its discharge capacity is 169.8 mAh/g at 0.2C. After 100 cycles at 0.2C, the discharge specific capacity can still be maintained at 143.24 mAh/g, and its capacity retention ratio is as high as 92  %. An environmental assessment and economic evaluation indicate that the process is an economical and eco-friendly approach for green recycling of spent LIBs.

Chemical Bond Bridging across Two Domains: Generation of Fe(II) and In Situ Formation of FeSx on Zerovalent Iron.

Sulfidation of zerovalent iron (SZVI) can strengthen the decontamination ability by promoting the electron transfer from inner Fe0 to external pollutants by iron sulfide (FeSx). Although FeSx forms easily, the mechanism for the FeSx bonding on the ZVI surface through a liquid precipitation method is elusive. In this work, we demonstrate a key pathway for the sulfidation of ZVI, namely, the in situ formation of FeSx on ZVI surface, which leads to chemical bonding across two domains: the pristine ZVI and the newly formed FeSx phase. The two chemically bridged heterophases display superior activity in electron transportation compared to the physically coated SZVI, eventually bringing about the better performance in reducing Cr(VI) species. It is revealed that the formation of chemically bonded FeSx requires balancing the rates for the two processes of Fe(II) release and sulfidation, which can be achieved by tuning the pH and S(-II) concentration. This study elucidates a mechanism for surface generation of FeSx on ZVI, and it provides new perspectives to design high-quality SZVI for environmental applications.