Sulfur Resources Research Articles

ZIF‐67/ZIF‐8 and its Derivatives for Lithium Sulfur Batteries

AbstractLithium–sulfur batteries (LSBs), renowned for their superior energy density and the plentiful availability of sulfur resources, are progressively emerging as the focal point of forthcoming energy storage technology. Nevertheless, they presently confront fundamental challenges including insulation of sulfur and its discharge product, the lithium polysulfides (LiPSs) shuttle phenomenon, and the growth of lithium dendrites. Zeolite imidazole framework materials (ZIFs), particularly ZIF‐8 and ZIF‐67, are significant members of the metal–organic frameworks (MOFs) family. Owing to their high porosity, exceptional adsorption capacity, high structural tunability, and straightforward synthesis process, these materials have demonstrated unique application potential in the field of LSBs. This review initially provides a comprehensive summary of the developmental status and challenges associated with LSBs. Subsequently, it delves into an in‐depth analysis of the distinctive properties and synthesis strategies of ZIFs, with a particular emphasis on ZIF‐8 and ZIF‐67, as well as their composites and derivatives. The review systematically categorizes innovative application examples of these materials in the design of cathode structures and optimization of separators in LSBs. It also presents a forward‐looking perspective and insights on the potential future trajectory of ZIF‐67 materials, informed by the latest research advancements in the field.

Recovering element sulfur from sulfur-containing waste through a pressure induced melting-crystallization method: Optimization using response surface methodology

Metallurgical sulfur-containing wastes (MSCWs) is an important secondary resource for recovering element sulfur in chemical and metallurgical industries. However, it is challenging to simultaneously achieve high recovery rate and sulfur purity, due to the multiple impurities combining with sulfur in these wastes. In this paper, we developed a novel method of pressure induced melting-crystallization to efficiently recover sulfur from MSCWs. The effects of condition parameters on the sulfur recovery rate and purity were optimized through response surface methodology. The single objective optimization results showed that the interaction between melting temperature and slurry concentration had a great influence on sulfur purity. The slurry concentration and pressure had great influence on sulfur recovery rate. The results of multi-objective optimization showed that under the conditions of pressure 1.2 MPa, slurry concentration 14.9% and melting temperature 140.9℃, the highest sulfur purity and recovery rate could reach 93.0% and 89.1% respectively. Mechanism investigation revealed that the high efficiency of sulfur recovery was ascribed to recrystallization of molten sulfur under the combined action of pressure and water, forming dense sulfur blocks and separating hydrophilic impurities. This work provides a new way to recover sulfur resources from MSCWs with sulfur content higher than 50%.

A Novel Fabrication of Hematite Nanoparticles via Recycling of Titanium Slag by Pyrite Reduction Technology.

An enormous quantity of titanium slag has caused not merely serious environment pollution, but also a huge waste of iron and sulfur resources. Hence, recycling iron and sulfur resources from titanium slag has recently been an urgent problem. Herein, hematite nanoparticles were fabricated through a pyrite reduction approach using as-received titanium slag as the iron source and pyrite as the reducing agent in an nitrogen atmosphere. The physicochemical properties of the hematite nanoparticles were analyzed using multiple techniques such as X-ray diffraction pattern, ultraviolet-visible spectrophotometry, and scanning electron microscopy. The best synthesis conditions for hematite nanoparticles were found at 550 °C for 30 min with the mass ratio of 14:1 for titanium slag and pyrite. The results demonstrated that hematite nanoparticles with an average particle diameter of 45 nm were nearly spherical in shape. The specific surface area, pore volume, and pore size estimated according to the BET method were 19.6 m2/g, 0.117 cm3/g, and 0.89 nm, respectively. Meanwhile, the fabricated hematite nanoparticles possessed weak ferromagnetic behavior and good absorbance in the wavelength range of 200 nm-600 nm, applied as a visible light responsive catalyst. Consequently, these results show that hematite nanoparticles formed by the pyrite reduction technique have a promising application prospect for magnetic material and photocatalysis.

Polyoxomolybdate-Based Metal-Organic Framework-Derived Cu-Embedded Molybdenum Dioxide Hybrid Nanoparticles as Highly Efficient Electrocatalysts for Al-S Batteries.

High-performance rechargeable aluminum-sulfur batteries (RASB) have great potential for various applications owing to their high theoretical capacity, abundant sulfur resources, and good safety. Nevertheless, the practical application of RASB still faces several challenges, including the polysulfide shuttle phenomenon and low sulfur utilization efficiency. Here, we first developed a synergistic copper heterogeneous metal oxide MoO2 derived from polymolybdate-based metal-organic framework as an efficient catalyst for mitigating polysulfide diffusion. This composite enhances sulfur utilization and electrical conductivity of the cathode. DFT calculations and experimental results reveal the catalyst Cu/MoO2@C not only effectively anchors aluminum polysulfides (AlPSs) to mitigate the shuttle effect, but also significantly promotes the catalytic conversion of AlPSs on the sulfur cathode side during charging and discharging. The unique nanostructure contains abundant electrocatalytic active sites of oxide nanoparticles and Cu clusters, resulting in excellent electrochemical performance. Consequently, the established RASB exhibits an initial capacity of 875 mAh g-1 at 500 mA g-1 and maintains a capacity of 967 mAh g-1 even at a high temperature of 50 °C.

Engineering Oxygen Vacancies in In2O3 with Enhanced Polysulfides Immobilization and Selective Catalytic Capability.

Lithium-sulfur (Li-S) battery is identified as an ideal candidate for next-generation energy storage systems in consideration of its high theoretical energy density and abundant sulfur resources. However, the shuttling behavior of soluble polysulfides (LiPSs) and their sluggish reaction kinetics severely limit the practical application of the current Li-S battery. In this work, a series of In2O3 nanocubes with different oxygen vacancy concentrations are designed and prepared via a facile self-template method. The introduced oxygen vacancy on In2O3 can effectively rearrange the charge distribution and enhance sulfiphilic property. Moreover, the In2O3 with high oxygen vacancy concentration (H-In2O3) can slightly slow down the solid-liquid conversion process and significantly accelerate the liquid-solid conversion process, thus reducing the accumulation of LiPSs in electrolyte and inhibiting the shuttle effect. Contributed by the unique selective catalytic capability, the prepared H-In2O3 exhibits excellent electrochemical performance when used as sulfur host. For instance, a high reversible capacity of 609 mAh g-1 is obtained with only 0.044% capacity decay per cycle over 1000 cycles at 1.0C. This work presents a typical example for designing advanced sulfur hosts, which is crucial for the commercialization of Li-S battery.

Electrochemical processes for simultaneous sulfur and energy recoveries from sulfide-containing wastewater

Hydrogen sulfide and dissolved sulfide are notorious and lethal contaminants. The electrochemical process adopting the two-electron sulfide anodic oxidation reaction is an attractive strategy, which can simultaneously recycle and convert the chemical energy and sulfur resources into valued products. Sulfide pollutants are promising electron donors to reduce the electrochemical production cost, which is demonstrated in a sulfide/air fuel cell and a sulfide depolarized electrolyser. Sulfide oxidation behaviors are investigated on the developed IrxRu1-xO2 catalyst. A sulfide/air fuel cell is applied to evaluate the self-driven abilities of sulfur recovery and electricity generation. The sulfide/air fuel cell exhibits a notable discharge current density of > 120 mA cm−2 for 1.0 mol/L Na2S solution and 42.43 ± 1.94 mA cm−2 for the sulfide spent caustic stream. The potentials of sulfide anodic depolarization for electrochemical cost reduction are evaluated in a sulfide depolarized electrolyser for hydrogen production. Its open cell voltage is −0.33 V. For sulfur recovery, the cell can achieve about 20 mA cm−2 at 1.0 V, where the average energy cost of hydrogen production is about 2.39 kWh Nm−3. The sulfide removal rate is 0.26 ± 0.04 kgS m-2h−1, with an average current efficiency of 152.47 ± 28.59 %. This work may shed light on the potential of the incorporation of sulfide contaminants abatement and electrochemical productions.

Room temperature, ultrafast and one-step synthesis of highly fluorescent sulfur quantum dots probe and their logic gate operation

The direct and rapid conversion of abundant and cheap elemental sulfur into fluorescent sulfur quantum dots (SQDs) at room temperature is a critical and urgent challenge. Conventional synthesis methods require high temperatures, high pressures, or specific atmospheric conditions, making them complex and impractical for real applications. Herein, we propose a simple method for synthesizing SQDs simply by adding H2O2 to an elemental sulfur-ethylenediamine (S-EDA) solution at room temperature. Remarkably, within a mere 10 min, SQDs with a photoluminescence quantum yield of 23.6 % can be obtained without the need for additional steps. A comprehensive analysis of the mechanism has demonstrated that H2O2 is capable of converting Sx2− ions generated in the S-EDA solution into zero-valent sulfur atoms through oxidation. The obtained SQDs can be utilized as a fluorescent probe for detection of tetracycline (TC) and Ca2+ ions with the limit of detection (LOD) of 0.137 μM and 0.386 μM respectively. Moreover, we have developed a sensitive logic gate sensor based on SQDs, harnessing the activated cascade effect to create an intelligent probe for monitoring trace levels of TC and Ca2+ ions. This paper not only presents a viable approach for ultrafast and scalable synthesis of SQDs at room temperature, but also contributes to the efficient utilization of elemental sulfur resources.

Nafion-Mediated Proton Transfer Facilitates the Electroreduction of SO2 to H2S.

The electrocatalytic reduction of SO2 to produce H2S is a critical approach for achieving the efficient utilization of sulfur resources. At the core of this approach for commercial applications lies the imperative need to elevate current density. However, the challenges posed by high current density manifest in the rapid depletion of protons, leading to a decrease in SO2 partial pressure, consequently hampering the generation and separation of H2S. Here, we demonstrate an effective solution to alleviate the problem of insufficient supply of protons by employing Nafion polymer as the proton conductor to modified Cu catalysts surface, creating a proton-enriched layer to boost H2S generation. It was observed that Nafion shortens the hydrogen bonds with water molecules in the electrolyte via its sulfonic acid groups, benefiting the proton transfer and consequently increasing the proton density on the electrode surface by 5-fold. With the Nafion-modified catalyst, the H2S partial current density and separation efficiency reached 205.9 mA·cm-2 (1.01 mmol·cm-2·h-1) and 87.8%, which were 1.34 and 1.22 times that on unmodified Cu, respectively. This work highlights the practicality of fabricating a proton conductor via ionic polymer for the control over product selectivity in pH-sensitive reactions under high current density.

Effects of glutaric acid, tricarballylic acid and citric acid on the morphology of α-hemihydrate gypsum: Experimental and DFT simulation studies

The controlled synthesis of α-hemihydrate (α-HH) gypsum using flue gas desulfurized gypsum is essential for the utilization of calcium and sulfur resources. An aspect ratio (AR) close to 1 is essential to improve the quality and performance of α-HH gypsum. To solve this problem, the morphological modification of α-HH gypsum by modifiers such as glutaric acid (GA), tricarballylic acid (TA) and citric acid (CA) was systematically studied. Five concentrations of 1.0–3.0 mM were considered for each modifier, with 0.5 mM as intervals. Our results show that the effect of GA is very small, while TA and CA can effectively turn needle-like α-HH gypsum into rod-like crystals. This change can be well quantified by the change in AR of α-HH gypsum crystals. The evolution of the morphology is determined by the preferential adsorption of the modifier on different surfaces of the α-HH gypsum crystals. These results and fundamental understanding should provide useful information for improving the synthesis of α-HH gypsum using flue gas desulfurized gypsum.

Intercalation-type catalyst for non-aqueous room temperature sodium-sulfur batteries

Ambient-temperature sodium-sulfur (Na-S) batteries are potential attractive alternatives to lithium-ion batteries owing to their high theoretical specific energy of 1,274 Wh kg−1 based on the mass of Na2S and abundant sulfur resources. However, their practical viability is impeded by sodium polysulfide shuttling. Here, we report an intercalation-conversion hybrid positive electrode material by coupling the intercalation-type catalyst, MoTe2, with the conversion-type active material, sulfur. In addition, MoTe2 nanosheets vertically grown on graphene flakes offer abundant active catalytic sites, further boosting the catalytic activity for sulfur redox. When used as a composite positive electrode and assembled in a coin cell with excess Na, a discharge capacity of 1,081 mA h gs−1 based on the mass of S with a capacity fade rate of 0.05% per cycle over 350 cycles at 0.1 C rate in a voltage range of 0.8 to 2.8 V is realized under a high sulfur loading of 3.5 mg cm−2 and a lean electrolyte condition with an electrolyte-to-sulfur ratio of 7 μL mg−1. A fundamental understanding of the electrocatalysis of MoTe2 is further revealed by in-situ synchrotron-based operando X-ray diffraction and ex-situ time-of-flight secondary ion mass spectrometry.

Use of La-Co@NPC for Sulfite Oxidation and Arsenic Detoxification Removal for High-Quality Sulfur Resources Recovery in Desulfurization Process.

Ammonia desulfurization is a typical resource-recovery-type wet desulfurization process that is widely used in coal-fired industrial boilers. However, the sulfur recovery is limited by the low oxidation rate of byproduct (ammonium sulfite), leading to secondary SO2 pollution due to its easy decomposability. In addition, the high toxic arsenic trace substances coexisting in desulfurization liquids also reduce the quality of the final sulfate product, facing with high environmental toxicity. In this study, nitrogen-doped porous carbon coembedded with lanthanum and cobalt (La-Co@NPC) was fabricated with heterologous catalytic active sites (Co0) and adsorption sites (LaOCl) to achieve sulfite oxidation and the efficient removal of high toxic trace arsenic for the recovery of high-value ammonium sulfate from the desulfurization liquid. The La-Co@NPC/S(IV) catalytic system can generate numerous strongly oxidizing free radicals (·SO5- and ·O2-) for the sulfite oxidation on the Co0 site, as well as oxidative detoxification of As(III) into As(V). Subsequently, arsenic can be removed through chemical adsorption on LaOCl adsorption sites. By using the dual-functional La-Co@NPC at a concentration of 0.25 g/L, the rate of ammonium sulfite oxidation reached 0.107 mmol/L·s-1, the arsenic (1 mg/L) removal efficiency reached 92%, and the maximum adsorption capacity of As reached up to 123 mg/g. This study can give certain guiding significance to the functional material design and the coordinated control of multiple coal-fired pollutants in desulfurization for high-value recovery of sulfur resources.

Bimetal‐Organic Framework Nanoboxes Enable Accelerated Redox Kinetics and Polysulfide Trapping for Lithium‐Sulfur Batteries

AbstractLithium‐sulfur (Li−S) batteries are considered as promising candidates for next‐generation energy storage systems in view of the high theoretical energy density and low cost of sulfur resources. The suppression of polysulfide diffusion and promotion of redox kinetics are the main challenges for Li−S batteries. Herein, we design and prepare a novel type of ZnCo‐based bimetallic metal–organic framework nanoboxes (ZnCo‐MOF NBs) to serve as a functional sulfur host for Li−S batteries. The hollow architecture of ZnCo‐MOF NBs can ensure fast charge transfer, improved sulfur utilization, and effective confinement of lithium polysulfides (LiPSs). The atomically dispersed Co−O4 sites in ZnCo‐MOF NBs can firmly capture LiPSs and electrocatalytically accelerate their conversion kinetics. Benefiting from the multiple structural advantages, the ZnCo‐MOF/S cathode shows high reversible capacity, impressive rate capability, and prolonged cycling performance for 300 cycles.

Bimetal-Organic Framework Nanoboxes Enable Accelerated Redox Kinetics and Polysulfide Trapping for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered as promising candidates for next-generation energy storage systems in view of the high theoretical energy density and low cost of sulfur resources. The suppression of polysulfide diffusion and promotion of redox kinetics are the main challenges for Li-S batteries. Herein, we design and prepare a novel type of ZnCo-based bimetallic metal-organic framework nanoboxes (ZnCo-MOF NBs) to serve as a multifunctional sulfur host for Li-S batteries. The hollow architecture of ZnCo-MOF NBs can ensure fast charge transfer, improved sulfur utilization, and effective confinement of lithium polysulfides (LiPSs). The atomically dispersed Co-O4 sites in ZnCo-MOF NBs can firmly capture LiPSs and electrocatalytically accelerate their conversion kinetics. Benefiting from the multiple structural advantages, the ZnCo-MOF/S cathode shows high reversible capacity, impressive rate performance, and superior cycling stability for 300 cycles.

Functionalized Hf3C2 and Zr3C2 MXenes for suppression of shuttle effect to enhance the performance of sodium–sulfur batteries

Sodium-sulfur batteries show great potential for storing large amounts of energy due to their ability to undergo a double electron-redox process, as well as the plentiful abundance of sodium and sulfur resources. However, the shuttle effect caused by intermediate sodium polysulfides (Na2Sn) limits their performance and lifespan. To address this issue, here we propose using Hf3C2T2 and Zr3C2T2 (T = F, O), two functionalized MXenes, as cathode additives to suppress the shuttle effect. By using density-functional theory calculations, we investigate nature of the interactions between Na2Sn and MXene, such as the strength of adsorption energy, the electronic density of states, the charge exchange, and the dissociation energy of the Na2S molecule. Our findings show that both Hf3C2T2 and Zr3C2T2 systems inhibit the shuttle effect by binding to Na2Sn with a binding energy stronger than the commonly used electrolyte solvents. These MXenes retain their metallicity during this process and the decomposition barrier for Na2Sn on the oxygen-functionalized MXenes gets reduced which enhances the electrochemical process. Among the MXene systems studied, Zr3C2O2 shows the best performance in suppressing the shuttle effect and catalyzing the electrochemistry process and, thus, increasing the battery's reversible capacity and lifespan.

Enhanced Separation of Sulfur and Metals from Polymetallic Sulfur Slag through Recrystallizing Regulation of Sulfur Crystals

Elemental sulfur is an important non-metallic material that is widely used in various fields including chemical, metallurgical and sulfuric acid industries. Polymetallic sulfur slag (PSS) is an important secondary resource for the recovery of sulfur. However, separation of sulfur from PSS is difficult due to the tight binding of some thiophilic metals to sulfur. Herein, we proposed a recrystallization method for the effective separation of sulfur and metals by using organic solvents to control the particle size of sulfur crystals. It was suggested that the particle size of sulfur recovered in the close to saturation state of toluene is about 2000 μm, while the purity is as high as 99.6%. Moreover, the recovery rate is over 95%, which is more than the current commonly used flotation method. The growth mechanism of sulfur crystals under different saturation conditions lays a foundation for the deepening of the growth theory of large-size sulfur crystals. This method realized the effective separation of sulfur from metal sulfides such as FeS2 and ZnS, which provided an important guidance for the recovery of sulfur resources through a novel method of recrystallizing regulation.

Research on the Selective Electrocatalytic Reduction of SO2 to Recover S0 by Pb Electrode

Resource utilization of SO2 from flue gas is a key challenge for the green development of the smelting industry. Recovery of sulfur resources in the form of elemental sulfur (S0), which has a high market demand and is a current focus in the field of SO2 treatment, can reduce the solid waste from desulfurization. In this study, it was found that Pb as a cathode material had good catalytic activity for the electrochemical reduction of SO2 and good selectivity towards elemental sulfur. However, the cathode suffers from sulfur poisoning. The problem was resolved by introducing surfactant, specifically sodium dodecyl benzene sulfonate (SDBS), which significantly lowered the sulfur content ratio on the surface of the electrode from 31.82% to 2.17%. Through the optimization of electrocatalytic parameters, this method enables efficient conversion of SO2 to S0, achieving a selectivity of 83% at pH = 0.25 and E = −0.8 V (vs. SCE).

Effective recovery of calcium and sulfur resources in FGD gypsum: Insights from the mechanism of reduction roasting and the conversion process of sulfur element

Flue gas desulfurized (FGD) gypsum is produced during the removal of SO2 from flue gas. The reductive decomposition of FGD gypsum to calcium sulfide (CaS) is a crucial method for resource utilization. This study investigated the reduction roasting behavior and mechanism to enrich and recycle the calcium and sulfur resources in FGD gypsum effectively. Firstly, thermodynamics calculation revealed that the complete reduction of CaSO4 to CaS is feasible. Experimental results showed that more than 95 % of the FGD gypsum can be reduced to CaS. Subsequently, the kinetic parameters of the reduction process were calculated. The results indicate that the reaction is controlled by the phase boundary, which is a typical shrinking sphere reaction process. Based on the kinetic study, the micromorphological transformation during the reduction process were studied. The results show that the reduction reaction initially starts from the boundary and gradually occurs towards the core. Finally, the reduction roasting mechanism is proposed. The intermediate processes of calcium sulfate reduction behavior were studied through XRD and XPS. The phase conversion and behavior of the main elements S in the process were explored. The results indicate that the process is a step-by-step reduction, and the transformation of S is SO42−-SO32−-S22−-S2−. The reduction product forms a hollowed-out spheroid structure that cannot only effectively enrich Ca and S resources, but also provide advantageous conditions for their subsequent reuse.

Effects of Catalysis and Separator Functionalization on High‐Energy Lithium–Sulfur Batteries: A Complete Review

Lithium–sulfur (Li‐S) batteries have the advantages of high theoretical specific capacity (1675 mAh g−1), rich sulfur resources, low production cost, and friendly environment, which makes it one of the most promising next‐generation rechargeable energy storage devices. However, the “shuttle effect” of polysulfide results in the passivation of metal lithium anode, the decrease of battery capacity and coulombic efficiency, and the deterioration of cycle stability. To realize the commercialization of Li‐S batteries, its serious “shuttle effect” needs to be suppress. The commercial separators are ineffective to suppress this effect because of its large pore size. Therefore, it is an effective strategy to modify the separator surface and introduce functional modified layer. In addition to the blocking strategy, the catalysis of polysulfide conversion reaction is also an important factor hindering the migration of polysulfides. In this review, the principles of separator modification, functionalization, and catalysis in Li‐S batteries are reviewed. Furthermore, the research trend of separator functionalization and polysulfide catalysis in the future is prospected.

Insights into the Superior Bioavailability of Biogenic Sulfur from the View of Its Unique Properties: The Key Role of Trace Organic Substances.

Elemental sulfur (S0) is widely utilized in environmental pollution control, while its low bioavailability has become a bottleneck for S0-based biotechnologies. Biogenic sulfur (bio-S0) has been demonstrated to have superior bioavailability, while little is known about its mechanisms thus far. This study investigated the bioavailability and relevant properties of bio-S0 based on the denitrifying activity of Thiobacillus denitrificans with chemical sulfur (chem-S0) as the control. It was found that the conversion rate and removal efficiency of nitrate in the bio-S0 system were 2.23 and 2.04 times those of the chem-S0 system. Bio-S0 was not pure orthorhombic sulfur [S: 96.88 ± 0.25% (w/w)]. Trace organic substances detected on the bio-S0 surface were revealed to contribute to its hydrophilicity, resulting in better dispersibility in the aqueous liquid. In addition, the adhesion force of T. denitrificans on bio-S0 was 1.54 times that of chem-S0, endowing a higher bacterial adhesion efficiency on the sulfur particle. The weaker intermolecular binding force due to the low crystallinity of bio-S0 led to enhanced cellular uptake by attached bacteria. The mechanisms for the superior bioavailability of bio-S0 were further proposed. This study provides a comprehensive view of the superior bioavailability of bio-S0 and is beneficial to developing high-quality sulfur resources.

Three-dimensional carbon foam decorated with SnO2 as multifunctional host for lithium sulfur batteries.

Lithium-sulfur (Li-S) batteries with high theoretical capacity and abundant sulfur resources are potential energy storage systems. Nevertheless, there are several roadblocks that strongly limit the commercial application of Li-S batteries, including the insulating nature of sulfur and Li2S, large volume change and the shuttle effect of lithium polysulfides. Herein, a three-dimensional carbon foam (CF) decorated with SnO2 (SnO2/CF) is fabricated by the simple electrodeposition and used as a sulfur host to resolve the bottleneck issues in Li-S batteries. Thanks to the synergetic effect of the polar SnO2 and conductive carbon framework, the SnO2/CF framework is endowed with multifunctionalities such as providing three-dimensional conductive framework, inhibiting the migration of polysulfides and improved reaction kinetics. Consequently, durable cycle performance with a capacity of 458.2 mAh g-1 after 1000 cycles at 1 C is achieved. Furthermore, a high capacity of 749.5 mAh g-1 at a high rate of 5 C is attained. Remarkably, under high sulfur loading of 8.84mgcm-2, the S@SnO2/CF cathode can still deliver a high specific capacity of 389.8 mAh g-1 after 300 cycles at 0.5 C. This work demonstrates a novel strategy to improve the performance of Li-S batteries for energy storage applications.