Unsaturated Sulfur Edge Engineering of Strongly Coupled MoS2 Nanosheet–Carbon Macroporous Hybrid Catalyst for Enhanced Hydrogen Generation

The low hydrogen adsorption free energy and strong acid/alkaline resistance of layered MoS₂ render it an excellent pH‐universal electrocatalyst for hydrogen evolution reaction (HER). However, the catalytic activity is dominantly suppressed by its limited active‐edge‐site density. Herein, a new strategy is reported for making a class of strongly coupled MoS₂ nanosheet–carbon macroporous hybrid catalysts with engineered unsaturated sulfur edges for boosting HER catalysis by controlling the precursor decomposition and subsequent sodiation/desodiation. Both surface chemical state analysis and first‐principles calculations verify that the resultant catalysts exhibit a desirable valence‐electron state with high exposure of unsaturated sulfur edges and an optimized hydrogen adsorption free energy, significantly improving the intrinsic HER catalytic activity. Such an electrocatalyst exhibits superior and stable catalytic activity toward HER with small overpotentials of 136 mV in 0.5 m H₂SO₄ and 155 mV in 1 m KOH at 10 mA cm^?2, which is the best report for MoS₂–C hybrid electrocatalysts to date. This work paves a new avenue to improve the intrinsic catalytic activity of 2D materials for hydrogen generation.     

NiCo2O4 Nanofibers as Carbon‐Free Sulfur Immobilizer to Fabricate Sulfur‐Based Composite with High Volumetric Capacity for Lithium–Sulfur Battery

Both the energy density and cycle stability are still challenges for lithium–sulfur (Li–S) batteries in future practical applications. Usually, light‐weight and nonpolar carbon materials are used as the hosts of sulfur, however they struggle on the cycle stability and undermine the volumetric energy density of Li–S batteries. Here, heavy NiCo₂O₄ nanofibers as carbon‐free sulfur immobilizers are introduced to fabricate sulfur‐based composites. NiCo₂O₄ can accelerate the catalytic conversion kinetics of soluble intermediate polysulfides by strong chemical interaction, leading to a good cycle stability of sulfur cathodes. Specifically, the S/NiCo₂O₄ composite presents a high gravimetric capacity of 1125 mAh g^?1 at 0.1 C rate with the composite as active material, and a low fading rate of 0.039% per cycle over 1500 cycles at 1 C rate. In particular, the S/NiCo₂O₄ composite with the high tap density of 1.66 g cm^?3 delivers large volumetric capacity of 1867 mAh cm^?3, almost twice that of the conventional S/carbon composites.     

Carbon‐Sheathed MoS2 Nanothorns Epitaxially Grown on CNTs: Electrochemical Application for Highly Stable and Ultrafast Lithium Storage

Molybdenum disulfide (MoS₂), which possesses a layered structure and exhibits a high theoretical capacity, is currently under intensive research as an anode candidate for next generation of Li‐ion batteries. However, unmodified MoS₂ suffers from a poor cycling stability and an inferior rate capability upon charge/discharge processes. Herein, a unique nanocomposite comprising MoS₂ nanothorns epitaxially grown on the backbone of carbon nanotubes (CNTs) and coated by a layer of amorphous carbon is synthesized via a simple method. The epitaxial growth of MoS₂ on CNTs results in a strong chemical coupling between active nanothorns and carbon substrate via C? S bond, providing a high stability as well as a high‐efficiency electron‐conduction/ion‐transportation system on cycling. The outer carbon layer can well‐accommodate the structural strain in the electrode upon lithium‐ion insertion/extraction. When employed as an anode for lithium storage, the prepared material exhibits remarkable electrochemical properties with a high specific capacity of 982 mA h g^?1 at 0.1 A g^?1, as well as excellent long‐cycling stability (905 mA h g^?1 at 1 A g^?1 after 500 cycles) and superior rate capability, confirming its potential application in high‐performance Li‐ion batteries.     

Tailoring Interfacial Charge Transfer of Epitaxially Grown Ir Clusters for Boosting Hydrogen Oxidation Reaction

The sluggish kinetics of hydrogen oxidation reaction (HOR) is one of the critical challenges for anion exchange membrane fuel cells. Here, we report epitaxial growth of Ir nanoclusters (<2 nm) on a MoS₂ surface (Ir/MoS₂) and optimize the alkaline HOR activity via tailoring interfacial charge transfer between Ir clusters and MoS₂. The electron transfer from MoS₂ to Ir clusters can effectively prevent the oxidation of Ir clusters, which is not the case for carbon-supported Ir nanoclusters (Ir/C) synthesized using the same method. Moreover, the HOR performance of the Ir/MoS₂ can be further optimized by tuning the hydrogen binding energy (HBE) via a precise annealing treatment. A substantial exchange current density of 1.28 mA cm_ECSA⁻² is achieved in the alkaline medium, which is ∼10 times over that of Ir/C. The HOR mass-specific activity of Ir/MoS₂ heterostructure is as high as 182 mA mg_Ir⁻¹. The experimental results and density functional theory calculations reveal that the significant improved HOR activity is attributed to the decreased HBE, which highlights epitaxial growth is an effective way for boosting catalytic activity of heterostructured catalysts.     

A Low-Cost Al(OH)3-Modified Fire-Retardant and Shuttle-Limiting Separator for Safe and Stable Lithium–Sulfur Batteries

Lithium–sulfur battery (LSB) possesses high theoretical energy density, but its poor cycling stability and safety issues significantly restrict progress in practical applications. Herein, a low-cost and simple Al(OH)₃-based modification of commercial separator, which renders the battery outstanding fire-retardant and stable cycling, is reported. The modification is carried out by a simple blade coating of an ultrathin composite layer, mainly consisting of Al(OH)₃ nanoparticles and conductive carbon, on the cathode side of the separator. The Al(OH)₃ shows strong chemical absorption ability toward Lewis-based polysulfides and outstanding fire retardance through a self-decomposition mechanism under high heat, while the conductive carbon material acts as a top current collector to prevent dead polysulfide. LSB using the Al(OH)₃-modified separator shows an extremely low average capacity decade per cycle during 1000 cycles at 2 C (0.029%, 1 C = 1600 mA g⁻¹). The pouch cell exhibiting high energy density (426 Wh kg⁻¹) can also steadily cycle for more than 100 cycles with high capacity retention (70.2% at 0.1 C). The effectiveness and accessibility of this Al(OH)₃ modification strategy will hasten the practical application progress of LSBs.     

Capture and Catalytic Conversion of Polysulfides by In Situ Built TiO2‐MXene Heterostructures for Lithium–Sulfur Batteries

The detrimental shuttle effect in lithium–sulfur batteries mainly results from the mobility of soluble polysulfide intermediates and their sluggish conversion kinetics. Herein, presented is a multifunctional catalyst with the merits of strong polysulfides adsorption ability, superior polysulfides conversion activity, high specific surface area, and electron conductivity by in situ crafting of the TiO₂‐MXene (Ti₃C₂T_x) heterostructures. The uniformly distributed TiO₂ on MXene sheets act as capturing centers to immobilize polysulfides, the hetero‐interface ensures rapid diffusion of anchored polysulfides from TiO₂ to MXene, and the oxygen‐terminated MXene surface is endowed with high catalytic activity toward polysulfide conversion. The improved lithium–sulfur batteries deliver 800 mAh g^?1 at 2 C and an ultralow capacity decay of 0.028% per cycle over 1000 cycles at 2 C. Even with a high sulfur loading of 5.1 mg cm^?2, the capacity retention of 93% after 200 cycles is still maintained. This work sheds new insights into the design of high‐performance catalysts with manipulated chemical components and tailored surface chemistry to regulate polysulfides in Li–S batteries.     

Bioinspired Binders Actively Controlling Ion Migration and Accommodating Volume Change in High Sulfur Loading Lithium–Sulfur Batteries

High‐loading lithium–sulfur batteries have gained considerable fame for possessing high area capacity, but face a stern challenge from capacity fading because of serious issues, including “polysulfides shuttling,” insulating S/Li₂S, large volume changes, and the shedding of S/C particles during drying or the cell encapsulation process. Herein, a bioinspired water‐soluble binder framework is constructed via intermolecular physical cross‐linking of functional side chains hanging on the terpolymer binder. Experimental results and density‐functional theory (DFT) calculations reveal that this network binder featuring superior volume change accommodation can also capture lithium polysulfides (LiPSs) through strong anchoring of O, N⁺ actives to LiPSs by forming Li···O and N⁺···S_x^2? bonds. In addition, the abundant negative charged sulfonate coordination sites and good electrolyte uptake of the designed binder endow the assembled cells with high lithium ion conductivity and fast lithium ion diffusion. Consequently, a remarkable capacity retention of 98% after 350 cycles at 1 C and a high areal capacity of 12.8 mA h cm^?2 with high sulfur loading of 12.0 mg cm^?2 are achieved by applying the environmentally friendly binder.     

Dual‐Functional N Dopants in Edges and Basal Plane of MoS2 Nanosheets Toward Efficient and Durable Hydrogen Evolution

Herein, the authors explicitly reveal the dual‐functions of N dopants in molybdenum disulfide (MoS₂) catalyst through a combined experimental and first‐principles approach. The authors achieve an economical, ecofriendly, and most efficient MoS₂‐based hydrogen evolution reaction (HER) catalyst of N‐doped MoS₂ nanosheets, exhibiting an onset overpotential of 35 mV, an overpotential of 121 mV at 100 mA cm^?2 and a Tafel slope of 41 mV dec^?1. The dual‐functions of N dopants are (1) activating the HER catalytic activity of MoS₂ S‐edge and (2) enhancing the conductivity of MoS₂ basal plane to promote rapid charge transfer. Comprehensive electrochemical measurements prove that both the amount of active HER sites and the conductivity of N‐doped MoS₂ increase as a result of doping N. Systematic first‐principles calculations identify the active HER sites in N‐doped MoS₂ edges and also illustrate the conducting charges spreading over N‐doped basal plane induced by strong Mo 3d –S 2p –N 2p hybridizations at Fermi level. The experimental and theoretical research on the efficient HER catalysis of N‐doped MoS₂ nanosheets possesses great potential for future sustainable hydrogen production via water electrolysis and will stimulate further development on nonmetal‐doped MoS₂ systems to bring about novel high‐performance HER catalysts.     

Highly Stable Lithium–Sulfur Batteries Based on Laponite Nanosheet‐Coated Celgard Separators

Lithium–sulfur (Li–S) batteries are of great interest due to their high theoretical energy density. However, one of the key issues hindering their real world applications is polysulfide shuttle, which results in severe capacity decay and self‐discharge. Here, a laponite nanosheets/carbon black coated Celgard (LNS/CB‐Celgard) separator to inhibit polysulfide shuttle and to enhance the Li⁺ conductivity simultaneously is reported. The polysulfide shuttle is efficiently inhibited through strong interactions between the O active sites of the LNS and polysulfides by forming the Li···O and O? S bonds. Moreover, the separator features high Li⁺ conductivity, fast Li⁺ diffusion, excellent electrolyte wettability, and high thermal stability. Consequently, the Li–S batteries with the LNS/CB‐Celgard separator and the pure S cathode show a high initial reversible capacity of 1387 mA h g^?1 at 0.1 C, high rate performance, superior cycling stability (with a capacity decay rate of 0.06% cycle^?1 at 0.2 C and 0.028% cycle^?1 at 1.0 C over 500 cycles), and ultralow self‐discharge. The separator could also enhance the performance of other batteries such as the LiFePO₄/separator/Li battery. This work sheds a new light on the design and preparation of novel separators for highly stable Li–S batteries via a “green” and cost‐effective approach.     

Dramatically Enhanced Ambient Ammonia Electrosynthesis Performance by In‐Operando Created Li–S Interactions on MoS2 Electrocatalyst

The Haber‐Bosch process can be replaced by the ambient electrocatalytic N₂ reduction reaction (NRR) to produce NH₃ if suitable electrocatalysts can be developed. However, to develop high performance N₂ fixation electrocatalysts, a key issue to be resolved is to achieve efficient hydrogenation of N₂ without interference by the thermodynamically favored hydrogen evolution reaction (HER). Herein, in‐operando created strong Li–S interactions are reported to empower the S‐rich MoS₂ nanosheets with superior NRR catalytic activity and HER suppression ability. The Li⁺ interactions with S‐edge sites of MoS₂ can effectively suppress hydrogen evolution reaction by reducing H* adsorption free energy from 0.03 to 0.47 eV, facilitate N₂ adsorption by increasing N₂ adsorption free energy from –0.32 to –0.70 eV and enhance electrocatalytic N₂ reduction activity by decreasing the activation energy barrier of the reaction control step (*N₂ → *N₂H) from 0.84 to 0.42 eV. A NH₃ yield rate of 43.4 μg h^?1 mg^?1 MoS₂ with a faradaic efficiency (FE) of 9.81% can be achieved in presence of strong Li–S interactions, more than 8 and 18 times by the same electrocatalyst in the absence of Li–S interactions. This report opens a new way to design and develop catalysts and catalysis systems.     

Local Charge Distribution Engineered by Schottky Heterojunctions toward Urea Electrolysis

Urea electrooxidation with favorable thermodynamic potential offers great promise for decoupling H₂/O₂ evolution from sluggish water splitting, and simultaneously mitigating the problem of urea‐rich water pollution. However, the intrinsically slow kinetics of the six‐electron transfer process impels one to explore efficient catalysts in order to enable widespread use of this catalytic system. In response, taking CoS₂/MoS₂ Schottky heterojunctions as the proof‐of‐concept paradigm, a catalytic model to modulate the surface charge distribution for synergistically facilitating the adsorption and fracture of chemical group in urea molecule is proposed and the mechanism of urea electrooxidation at the molecular level is elucidated. Based on density functional calculations, the self‐driven charge transfer across CoS₂/MoS₂ heterointerface would induce the formation of local electrophilic/nucleophilic region, which will intelligently adsorb electron‐donating/electron‐withdrawing groups in urea molecule, activate the chemical bonds, and thus trigger the decomposition of urea. Benefiting from the regulation of local charge distribution, the constructed Schottky catalyst of CoS₂‐MoS₂ exhibits superior urea catalytic activities with a potential of 1.29 V (only 0.06 V higher than the thermodynamic voltage of water decomposition) to attain 10 mA cm^?2 as well as robust durability over 60 h. This innovational manipulation of charge distribution via Schottky heterojunction provides a model in exploring other highly efficient electrocatalysts.     

Simultaneous Cobalt and Phosphorous Doping of MoS2 for Improved Catalytic Performance on Polysulfide Conversion in Lithium–Sulfur Batteries

The lithium–sulfur batteries are susceptible to the loss of sulfur as dissolved polysulfides in the electrolyte and their ensuing redox shutting effect. The acceleration of the conversion kinetics of dissolved polysulfides into the insoluble sulfur and lithium sulfide via electrocatalysis has the appeal of being a root‐cause solution. MoS₂ is the most common electrocatalyst used for this purpose. It is demonstrated that how the effectiveness can be improved by simultaneous cobalt and phosphorus doping of MoS₂ nanotubes (P‐Mo_0.9Co_0.1S₂‐2, containing 1.81 at% of P). Cobalt doping induces the transformation of MoS₂ from 2H phase to metallic 1T phase, which improves the electrical conductivity of the MoS₂. The Co–P coordinated sites on the catalyst surface are highly active for the polysulfide conversion reactions. Consequently, a sulfur cathode with P‐Mo_0.9Co_0.1S₂‐2 can decrease the capacity fade rate from 0.28% per cycle before modification (over 150 cycles at 0.5C rate) to 0.046% per cycle after modification (over 600 cycles at 1C rate). P‐Mo_0.9Co_0.1S₂‐2 also enhances the high rate performance from a capacity of 338 to 931 mAh g^?1 at 6C rate. The results of this study provide the first direct evidence of the beneficial effects of heteroatom codoping of polysulfide conversion catalysts.     

Supercapacitor Electrodes Obtained by Directly Bonding 2D MoS2 on Reduced Graphene Oxide

Layered molybdenum disulfide (MoS₂) is deposited by microwave heating on a reduced graphene oxide (RGO). Three concentrations of MoS₂ are loaded on RGO, and the structure and morphology are characterized. The first layers of MoS₂ are detected as being directly bonded with the oxygen of the RGO by covalent chemical bonds (Mo‐O‐C). Electrochemical characterizations indicate that this electroactive material can be cycled reversibly between 0.25 and 0.8 V in 1 m HClO₄ solution for hybrids with low concentrations of MoS₂ layers (LCMoS₂/RGO) and between 0.25 and 0.65 V for medium (MCMoS₂/RGO) and high concentrations (HCMoS₂/RGO) of MoS₂ layers on graphene. The specific capacitance measured values at 10 mV s^?1 are 128, 265, and 148 Fg^?1 for the MoS₂/RGO with low, medium, and high concentrations of MoS₂, respectively, and the calculated energy density is 63 W h kg^?1 for the LCMoS₂/RGO hybrid. This supercapacitor electrode also exhibits superior cyclic stability with 92% of the specific capacitance retained after 1000 cycles.     

Catalytic Polysulfide Conversion and Physiochemical Confinement for Lithium–Sulfur Batteries

The lithium–sulfur (Li–S) battery is widely regarded as a promising energy storage device due to its low price and the high earth‐abundance of the materials employed. However, the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox conversion result in inefficient sulfur utilization, low power density, and rapid electrode deterioration. Herein, these challenges are addressed with two strategies 1) increasing LiPS conversion kinetics through catalysis, and 2) alleviating the shuttle effect by enhanced trapping and adsorption of LiPSs. These improvements are achieved by constructing double‐shelled hollow nanocages decorated with a cobalt nitride catalyst. The N‐doped hollow inner carbon shell not only serves as a physiochemical absorber for LiPSs, but also improves the electrical conductivity of the electrode; significantly suppressing shuttle effect. Cobalt nitride (Co₄N) nanoparticles, embedded in nitrogen‐doped carbon in the outer shell, catalyze the conversion of LiPSs, leading to decreased polarization and fast kinetics during cycling. Theoretical study of the Li intercalation energetics confirms the improved catalytic activity of the Co₄N compared to metallic Co catalyst. Altogether, the electrode shows large reversible capacity (1242 mAh g^?1 at 0.1 C), robust stability (capacity retention of 658 mAh g^?1 at 5 C after 400 cycles), and superior cycling stability at high sulfur loading (4.5 mg cm^?2).     

Optimized Catalytic WS2–WO3 Heterostructure Design for Accelerated Polysulfide Conversion in Lithium–Sulfur Batteries

The lithium–sulfur (Li–S) battery is a next generation high energy density battery, but its practical application is hindered by the poor cycling stability derived from the severe shuttling of lithium polysulfides (LiPSs). Catalysis is a promising way to solve this problem, but the rational design of relevant catalysts is still hard to achieve. This paper reports the WS₂–WO₃ heterostructures prepared by in situ sulfurization of WO₃, and by controlling the sulfurization degree, the structure is controlled, which balances the trapping ability (by WO₃) and catalytic activity (by WS₂) toward LiPSs. As a result, the WS₂–WO₃ heterostructures effectively accelerate LiPS conversion and improve sulfur utilization. The Li–S battery with 5 wt% WS₂–WO₃ heterostructures as additives in the cathode shows an excellent rate performance and good cycling stability, revealing a 0.06% capacity decay each cycle over 500 cycles at 0.5 C. By building an interlayer with such heterostructure‐added graphenes, the battery with a high sulfur loading of 5 mg cm^?2 still shows a high capacity retention of 86.1% after 300 cycles at 0.5 C. This work provides a rational way to prepare the metal oxide–sulfide heterostructures with an optimized structure to enhance the performance of Li–S batteries.     

In Situ TEM Study of Volume Expansion in Porous Carbon Nanofiber/Sulfur Cathodes with Exceptional High‐Rate Performance

Although lithium sulfur batteries (LSBs) have attracted much interest owing to their high energy densities, synthesis of high‐rate cathodes and understanding their volume expansion behavior still remain challenging. Herein, electrospinning is used to prepare porous carbon nanofiber (PCNF) hosts, where both the pore volume and surface area are tailored by optimizing the sacrificial agent content and the activation temperature. Benefiting from the ameliorating functional features of high electrical conductivity, large pore volume, and Li ion permselective micropores, the PCNF/A550/S electrode activated at 550 °C exhibits a high sulfur loading of 71 wt%, a high capacity of 945 mA h g^?1 at 1 C, and excellent high‐rate capability. The in situ transmission electron microscope examination reveals that the lithiation product, Li₂S, is contained within the electrode with only ≈35% volume expansion and the carbon host remains intact without fracture. In contrast, the PCNF/A750/S electrode with damaged carbon spheres exhibits sulfur sublimation, a larger volume expansion of over 61%, and overflowing of Li₂S, a testament to its poor cyclic stability. These findings provide, for the first time, a new insight into the correlation between volume expansion and electrochemical performance of the electrode, offering a potential design strategy to synthesize high‐rate and stable LSB cathodes.     

Molybdenum Disulfide/Nitrogen‐Doped Reduced Graphene Oxide Nanocomposite with Enlarged Interlayer Spacing for Electrocatalytic Hydrogen Evolution

Facile design of low‐cost and highly active catalysts from earth‐abundant elements is favorable for the industrial application of water splitting. Here, a simple strategy to synthesize an ultrathin molybdenum disulfide/nitrogen‐doped reduced graphene oxide (MoS₂/N‐RGO‐180) nanocomposite with the enlarged interlayer spacing of 9.5 Å by a one‐step hydrothermal method is reported. The synergistic effects between the layered MoS₂ nanosheets and N‐doped RGO films contribute to the high activity for hydrogen evolution reaction (HER). MoS₂/N‐RGO‐180 exhibits the excellent catalytic activity with a low onset potential of ?5 mV versus reversible hydrogen elelctrode (RHE), a small Tafel slope of 41.3 mV dec^?1, a high exchange current density of 7.4 × 10^?4 A cm^?2, and good stability over 5 000 cycles under acidic conditions. The HER performance of MoS₂/N‐RGO‐180 nanocomposite is superior to the most reported MoS₂‐based catalysts, especially its onset potential and exchange current density. In this work, a novel and simple method to the preparation of low‐cost MoS₂‐based electrocatalysts with the extraordinary HER performance is presented.     

Enhancing Catalytic Activity of Titanium Oxide in Lithium–Sulfur Batteries by Band Engineering

The altering of electronic states of metal oxides offers a promising opportunity to realize high‐efficiency surface catalysis, which play a key role in regulating polysulfides (PS) redox in lithium–sulfur (Li–S) batteries. However, little effort has been devoted to understanding the relationship between the electronic state of metal oxides and a catalyst's properties in Li–S cells. Herein, defect‐rich heterojunction electrocatalysts composed of ultrathin TiO_2‐x nanosheets and carbon nanotubes (CNTs) for Li–S batteries are reported. Theoretical simulations indicate that oxygen vacancies and heterojunction can enhance electronic conductivity and chemical adsorption. Spectroscopy and electrochemical techniques further indicate that the rich surface vacancies in TiO_2‐x nanosheets result in highly activated trapping sites for LiPS and lower energy barriers for fast Li ion mobility. Meanwhile, the redistribution of electrons at the heterojunction interfaces realizes accelerated surface electron exchange. Coupled with a polyacrylate terpolymer (LA132) binder, the CNT@TiO_2‐x–S electrodes exhibit a long cycle life of more than 300 cycles at 1 C and a high area capacity of 5.4 mAh cm^?2. This work offers a new perspective on understanding catalyst design in energy storage devices through band engineering.     

Sulfur in Ghanain soils

Sulfur availability in twenty selected surface soils (0–22 cm), which varied in both physical and chemical properties and sampled under cultivated and uncultivated management in the various ecological zones of Ghana, was studied. Texture varied from coarse sand to clay, with 16–85% sand and 10–51% clay. Organic C varied from 0.45 to 2.24% and total N from 0.034 to 0.215%; soil pH (0.01M CaCl₂) from 3.69 to 7.43 and total S from 44 to 273 ppm. Inorganic sulfate formed 2.3 to 14.8% of the total S, HI-reducible S 4.4 to 28.2, C-bonded S 4.4 to 28.2 and unidentified organic S 12.7 to 63.2%. Sulfur availability was assessed by chemical extraction methods and electroultrafiltration technique as follows: (i) extraction with Ca(H₂PO₄)₂·H₂O solution containing 500 ppm P, (ii) extraction with 0.1M LiCl and (iii) electroultrafiltration (EUF) at 80°C, 400 V for 10 min and also on seven of the soils the standard EUF fractionation procedure of Neméth. Ca(H₂PO₄)₂-extractable S was not significantly correlated with LiCl-extractable S nor with any of the EUF values. LiCl-extractable S was not significantly correlated with sulfate extractable by and EUF?1+2+3 fractions (r=0.911^**). Dry matter yield of oat seedlings and EUF?1+2+3 fractions (r=0.911^**). Dry matter yield of oat seedlings was not correlated with any of the availability indexes. Total S uptake was significantly correlated with LiCl-extractable S (r=0.629^** without S and 0.729^** with S applied) and with EUF-80°C, 400 V/10 min (r=0.561^**), EUF-1 (r=0.953^***) and EUF-2 (r=0.912^**). On all the soils, more S was taken up by oat plants than could be accounted for by the inorganic S and S mineralized from organic S during an incubation period of 4 weeks.     

Chemical Bonding and Physical Trapping of Sulfur in Mesoporous Magnéli Ti4O7 Microspheres for High‐Performance Li–S Battery

Various host materials have been investigated to address the intrinsic drawbacks of lithium sulfur batteries, such as the low electronic conductivity of sulfur and inevitable decay in capacity during cycling. Besides the widely investigated carbonaceous materials, metal oxides have drawn much attention because they form strong chemical bonds with the soluble lithium polysulfides. Here, mesoporous Magnéli Ti₄O₇ microspheres are prepared via an in situ carbothermal reduction that exhibit interconnected mesopores (20.4 nm), large pore volume (0.39 cm³ g^?1), and high surface area (197.2 m² g^?1). When the sulfur cathode is embedded in a matrix of mesoporous Magnéli Ti₄O₇ microspheres, it exhibits a superior reversible capacity of 1317.6 mA h g^?1 at moderate current (C/10) and a low decay in capacity of 12% after 400 cycles at C/5. Strong chemical bonding of the lithium polysulfides to Ti₄O₇, as well as effective physical trapping in the mesopores and voids in the matrix are considered responsible for the improved electrochemical performance. A mechanism of the physical and chemical interactions between mesoporous Magnéli Ti₄O₇ microspheres and sulfur is proposed based on systematic investigations.