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Optical absorption and redox kinetics of YBa 2 Cu 3 O 7 − δ thin films in oxidizing (O 2 ) and reducing (Ar/H 2 ) atmospheres were studied at temperatures from 200 °C to 500 °C by means of in situ UV–vis-NIR optical spectroscopy. The optical spectra in oxidizing atmospheres are characterized by optical absorption of oxygen holes, O − (O I ′), e. g., at about 450 nm at 200 °C, whereas those in reducing atmospheres are dominated by a band at about 600 nm due to electron hopping between Cu-ions. The fast redox processes of oxygen incorporation into and oxygen release from YBCO thin films induced by sudden changes in the ambient atmosphere between O 2 and Ar/H 2 are found to be controlled by surface exchange reaction. The oxygen surface exchange coefficients, k δ , determined from optical absorption relaxation experiments are about 4.96 × 10 − 7 m/s for the oxidation process and about 4.85 × 10 − 9 m/s for the reduction process at 500 °C. The temperature dependence of k δ yields an activation energy of about 0.3 eV for both oxidation and reduction processes in the studied temperature range. In addition, the rapid oxidation processes can be explained in terms of a high concentration of electrons in the reduced state of YBCO thin films, facilitating electron-transfer steps at the surface of YBCO film for oxygen exchange. [ABSTRACT FROM AUTHOR]

Copper oxide supported on silica and supported on alumina are often used as oxygen carriers for chemical looping combustion owing to their very high reduction rates at lower temperatures and their very good mechanical and chemical stability at temperatures below 1000 °C compared to other oxygen carriers. In this work, a comprehensive experimental study has been carried out to better understand the reaction mechanism and quantitatively describe the reaction kinetics of the oxygen uncoupling reaction and the reduction and oxidation reactions under different reaction conditions. First, the oxygen uncoupling and reduction reaction kinetics of the CuO/SiO 2 oxygen carrier was studied. A shrinking core type model (SCM) was developed that can well describe the oxygen uncoupling reaction rate and final conversion. Subsequently, a SCM and a simplified pseudo-homogeneous model was developed to describe the reduction kinetics of CuO/SiO 2 . Subsequently, the study was extended to investigate the reduction kinetics of CuO/Al 2 O 3 , where it was observed that the formation of tenorite spinel (CuAl 2 O 4 ) and cuprite spinel (CuAlO 2 ) strongly affects the overall reduction kinetics. Assuming that the reduction of CuO to Cu is independent of the support, the pseudo-homogeneous model was extended to include the reduction and oxidation kinetics of the spinel compounds, with which the experimentally determined redox kinetics could be well described. Regarding the CuO on Al 2 O 3 , The maximum temperature reached was 1000 °C in thermogravimetric analysis (TGA) without observing any sintering or melting effects. It can be due to the good stability with the Al 2 O 3 support and the relatively small amount of CuO (13%). However, for CuO/SiO 2 (70% CuO), the maximum temperature tested in the TGA was 900 °C, since at higher temperatures the sample was melting, due to the lower melting point of Cu. The main results of the study can be summarized as: (i) the oxygen uncoupling and reduction/oxidation of CuO/SiO 2 and CuO/Al 2 O 3 has been elucidated; (ii) a grain model that can describe the oxygen uncoupling and reduction reactions of CuO for different operating conditions has been developed; (iii) a pseudo-homogeneous grain model that can describe the redox kinetics of CuO/SiO 2 and CuO/Al 2 O 3 has been developed. [ABSTRACT FROM AUTHOR]

• A Fe-N 5 /NC SAC with high loading atomically dispersed Fe is prepared. • The asymmetrical Fe-N 5 sites in Fe-N 5 /NC are coordinated with pyridinic and pyrrolic N. • The Fe-N 5 /NC possesses excellent catalytic effects on series of complex SROR. • The Li-S battery with Fe-N 5 /NC-PP has a high performance with ultralong life. The practical application of Li-S battery is severely hampered by the sluggish sulfur-related redox reaction (SROR) kinetics along with lithium polysulfides (LiPSs) shuttle effect, advanced single-atom catalyst (SAC) is pursued to improve the SROR conversion capability. Herein, a novel SAC possessing of high loading (3.02 wt%) atomically dispersed Fe five-coordinated with pyridinic and pyrrolic N anchored on porous N-rich (16.4 at.%) carbon matrix is obtained. The resultant Fe-N 5 /NC SAC has a high Brunauer-Emmett-Teller surface area of 523 m2 g−1. The unique asymmetrical Fe-N 5 sites in Fe-N 5 /NC are identified by spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscope, X-ray photoelectron spectroscope, synchrotron X-ray absorption spectroscopy, density functional theory calculation, etc. The experimental and theoretical results demonstrate that the Fe-N 5 /NC SAC not only exhibits strong adsorption for LiPSs, but also provides a significant electrocatalytic effect on the SROR in Li-S battery. A high initial capacity of 1519 mAh g−1 was obtained at a current density of 0.1 C for the Li-S battery based on the Fe-N 5 /NC modified separator. An ultralong life of 2000 cycles was achieved for the Li-S battery, which has good initial capacities of 1030 mAh g−1 and 883 mAh g−1 with low decay rates of 0.032% and 0.031% per cycles at 1 C and 2 C, respectively. [ABSTRACT FROM AUTHOR]

Copper oxide on alumina is often used as oxygen carrier for chemical looping combustion owing to its very high reduction rates at lower temperatures and its very good mechanical and chemical stability at temperatures below 1000 °C. In this work, the redox behaviour of CuO/Al 2 O 3 has been studied in great detail together with the redox behaviour of CuO/SiO 2 to identify the main phenomena affecting the observed redox kinetics. Combination of TGA results with detailed characterisation with XRD of the oxygen carriers at different stages during the redox cycling allowed elucidating the causes for the sudden decrease in the reaction rate observed at higher conversions for the CuO/Al 2 O 3 oxygen carriers. The main results of the study can be summarized as: i) oxidation reaction reaches always full conversion independent of the reaction temperature; ii) reduction reaction reaches only full conversion at very high temperatures, showing a significant decrease in the reaction rate at lower temperatures at higher particle conversions; iii) the observed sudden decrease in the reduction rate is related to the spinel reduction of CuAl 2 O 4 and CuAlO 2 . [ABSTRACT FROM AUTHOR]

The studied electrochemical properties of the LaNiMnAlCoFe alloy showed a rather poor performance. To improve them, ZnO, a doping agent at different small amounts (0, 1, or 2.5 wt%), was added to this base alloy. Then, the prepared electrodes were investigated by various electrochemical techniques. The maximum discharge capacity, obtained after the activation procedure, increased with the rise in ZnO content. The activation, as well as the reversibility of the hydrogen absorption/desorption process, were significantly improved with the addition of ZnO. It was observed that the latter did not affect considerably the stability and the cycling lifetime if added to the electrodes. After 30 charge/discharge cycles, the diffusion coefficients were estimated to be 1.55 × 10, 1.30 × 10, and 6.05 × 10 cm s, respectively, for ZnO containing 0, 1, and 2.5 wt%. The ZnO catalyzed the kinetics of hydrogen absorption and desorption process thanks to capacity change before and after activation. [ABSTRACT FROM AUTHOR]

Incorporating electrocatalysts into lithium-sulfur (Li-S) batteries is a promising strategy to relieve the deleterious shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPSs). However, atomic modulation of the electrocatalysts to boost the catalytic activity is still challenging because of their intrinsic structural complexity. Herein, we report the theoretical prediction and experimental realization of Mo single atoms with different ligand coordinations (Mo-N x C 3−x), wherein we find that the LiPSs adsorption and conversion are well modulated by the atomic coordination species of single Mo centers. The resultant Mo-N 2 C 1 displays a moderate bonding strength with LiPSs in comparison with the Mo-N 1 C 2 and Mo-N 3 counterparts, which facilitates the charge transfer kinetics and reduces the Li 2 S precipitation/decomposition energy barrier. Consequently, the constructed Li-S batteries with Mo-N 2 C 1 present a durable cyclability with a low capacity decay rate of 0.055% each cycle over 1000 cycles at a high current rate of 10 C and a decent areal capacity of 4.27 mAh cm−2 after 100 cycles with a low electrolyte/sulfur ratio of 8 µL mg−1. This work demonstrates that optimizing LiPSs adsorption and conversion through local composition and coordination modulation is an effective strategy for developing efficient and durable electrocatalysts for advanced Li-S batteries. [Display omitted] • LiPSs adsorption energy can be effectively modulated through the ligand engineering of single Mo atoms at the atomic level. • Mo-N 2 C 1 presents a mild adsorbability toward LiPSs compared with the counterparts. • Rapid interfacial charge transfer kinetics and LiPSs conversion are achieved for Mo-N 2 C 1. • A high capacity of 732.1 mAh g−1 at 10 C associated with a low capacity decay rate of 0.055% over 1000 cycles is delivered. [ABSTRACT FROM AUTHOR]

Sluggish redox kinetics and shuttle effect of polysulfides hinder the extensive application of the lithium-sulfur batteries (LSBs). Herein a functional heterostructure of boron nitride (BN) and MXene with an alternately layered structure (BN@MXene) is designed as separator interlayer. High efficiency Li + transmission, uniform lithium deposition, strong adsorption, and efficient catalytic conversion activities of lithium polysulfides (LiPSs) realized by this heterostructure are confirmed by experiments and theoretical calculations. The alternately layered structure provides unblocked ion transmission channels and abundant active sites to accelerate the polysulfides redox kinetics with reduced energy barriers of oxidation and reduction reactions. As a result, the LSBs deliver an initial discharge capacity of up to 1273.9 mAh g -1 at 0.2 °C and a low decay of 0.058% per cycle in long-term cycling up to 700 cycles at 1 °C. This work provides an effective designing strategy to accelerate the polysulfides redox kinetics for advanced Li-S electrochemical system., (© 2023 Wiley-VCH GmbH.)

Lithium-sulfur batteries (LSBs) are recognized as the prospective candidate in next-generation energy storage devices due to their gratifying theoretical energy density. Nonetheless, they still face the challenges of the practical application including low utilization of sulfur and poor cycling life derived from shuttle effect of lithium polysulfides (LiPSs). Herein, a hollow polyhedron with heterogeneous CoO/Co 9 S 8 /nitrogen-doped carbon (CoO/Co 9 S 8 /NC) is obtained through employing zeolitic imidazolate framework as precursor. The heterogeneous CoO/Co 9 S 8 /NC balances the redox kinetics of Co 9 S 8 with chemical adsorption of CoO toward LiPSs, effectively inhibiting the shuttle of LiPSs. The mechanisms are verified by both experiment and density functional theory calculation. Meanwhile, the hollow structure acts as a sulfur storage chamber, which mitigates the volumetric expansion of sulfur and maximizes the utilization of sulfur. Benefiting from the above advantages, lithium-sulfur battery with S-CoO/Co 9 S 8 /NC achieves a high initial discharge capacity (1470 mAh g -1 ) at 0.1 C and long cycle life (ultralow capacity attenuation of 0.033% per cycle after 1000 cycles at 1 C). Even under high sulfur loading of 3.0 mg cm -2 , lithium-sulfur battery still shows the satisfactory electrochemical performance. This work may provide an idea to elevate the electrochemical performance of LSBs by constructing a hollow metal oxide/sulfide/nitrogen-doped carbon heterogeneous structure., (© 2023 Wiley-VCH GmbH.)

Lithium-sulfur batteries (LSBs) with superior energy density are among the most promising candidates of next-generation energy storage techniques. As the key step contributing to 75% of the overall capacity, Li 2 S deposition remains a formidable challenge for LSBs applications because of its sluggish kinetics. The severe kinetic issue originates from the huge interfacial impedances, indicative of the interface-dominated nature of Li 2 S deposition. Accordingly, increasing efforts have been devoted to interface engineering for efficient Li 2 S deposition, which has attained inspiring success to date. However, a systematic overview and in-depth understanding of this critical field are still absent. In this review, the principles of interface-controlled Li 2 S precipitation are presented, clarifying the pivotal roles of electrolyte-substrate and electrolyte-Li 2 S interfaces in regulating Li 2 S depositing behavior. For the optimization of the electrolyte-substrate interface, efforts on the design of substrates including metal compounds, functionalized carbons, and organic compounds are systematically summarized. Regarding the regulation of electrolyte-Li 2 S interface, the progress of applying polysulfides catholytes, redox mediators, and high-donicity/polarity electrolytes is overviewed in detail. Finally, the challenges and possible solutions aiming at optimizing Li 2 S deposition are given for further development of practical LSBs. This review would inspire more insightful works and, more importantly, may enlighten other electrochemical areas concerning heterogeneous deposition processes., (© 2023 Wiley-VCH GmbH.)

[Display omitted] • Hollow carbon spheres with conducting vanadium nitride decorating upon the surfaces are functioned as sulfur host material in Li-S batteries. • Preferential distribution of nano sulfur around the layer region rather than aggregating within the core of VNHCS host is demonstrated. • Excellent electrocatalytic effect toward LiPS conversion is demonstrated for the VNHCS host. Li-S battery has been regarded as one of the most promising energy storage technologies due to the remarkable increase in energy density and desirable low cost when comparing with the commercial lithium-ion battery, yet the shuttling effect of soluble lithium polysulfide (LiPS) and the sluggish reaction kinetics during the reactions have hampered its further development. Here, we develop the vanadium nitride-decorated hollow carbon sphere (VNHCS) as advantageous sulfur host aiming to address these issues. Preferential distribution of nano sulfur around the layer region of VNHCS rather than aggregating into particles within the core is demonstrated as a result of the desirable chemical bonding effect of VN nanoparticles, which helps boost the electron and ion transport rates and inhibit shuttling of LiPS simultaneously. Furthermore, the accelerated reaction kinetics towards LiPS conversion are demonstrated by the favorable catalytic behavior of VNHCS, which are verified by the theoretical simulation results. Benefiting from these merits, the S@VNHCS cathode has exhibited advantageous electrochemical performances including the high initial discharge capacity of 1453 mA h g−1 at 0.1C and the ultralow capacity fading rate of 0.0293 % per cycle at 2C, outperforming most of the reported results of nitride compound-based sulfur cathodes. [ABSTRACT FROM AUTHOR]

• Ultrafine Ni 2 P nanodots decorated porous N-doped carbon was fabricated by a facile chelate-phosphating strategy. • Ni 2 P electrocatalysts effectively enhanced chemisorption, accelerated LiPS conversion, and regulated Li 2 S precipitation. • The Li–S cell with Ni 2 P@PNC/S cathode under lean electrolyte system achieved outstanding electrochemical performance. The intractable shuttle effect and sluggish redox kinetics are major impediments to the practical application of lithium–sulfur (Li–S) batteries. Herein, ultrafine Ni 2 P nanodots decorated porous N-doped carbon (Ni 2 P@PNC) is successfully constructed by a novel chelate-phosphating strategy and employed as sulfur host to realize effective suppression of shuttle effect and enhancement of redox kinetics. Owing to the strong polarity and catalytic activity, the Ni 2 P electrocatalyst synergized with PNC conductive skeleton can efficiently promote chemisorption and catalytic conversion of the electrochemical intermediate lithium polysulfides. In addition, Ni 2 P@PNC can effectively decrease the transformation barrier and enhance the precipitation capability for the discharge end-product Li 2 S. As a result, the assembled Li–S cells with high sulfur-loading Ni 2 P@PNC/S cathode under low electrolyte/sulfur ratio deliver remarkable electrochemical performances in terms of high initial discharge capacity of 1350 mA h g–1, excellent rate capability of 695 mA h g–1 at 2.0 C, as well as outstanding cycle stability with an ultralow capacity decay rate of 0.021% per cycle over 1000 cycles at 2.0 C. Such the inspiring architectonic of multifunctional catalyzing-type sulfur hosts paves a new path for the development of high-performance Li− S batteries. [ABSTRACT FROM AUTHOR]

Inhibiting polysulfide shuttle and improving cycling stability are crucial for the commercialization of lithium-sulfur batteries (LSBs). Developing multifunctional sulfur host materials that combine rational carbon structure with highly catalytic metal compounds is pivotal for LSBs. Herein, Ultra-thin MoO 2 nanosheets loaded on hollow mesoporous carbon (HMC@MoO 2) were rationally designed and synthesized. In this structure, the hollow mesoporous carbon provides sufficient space to store sulfur and buffer volume fluctuations, the mesoporous carbon shell and the MoO 2 nanosheets on its surface can act as a double defensive system to effectively prevent polysulfide dissolution through physical and chemical trapping. Moreover, the ultra-thin MnO 2 nanosheets with more exposed active sites facilitate the capture and catalytic conversion of LiPSs, thereby effectively suppressing the shuttle effect of polysulfide. Consequently, the HMC@MoO 2 -S cathode exhibits impressive cycling stability, maintaining 771 mAh g−1 after 500 cycles at 0.5 C with a very low capacity decay of 0.045% per cycle. In particular, the HMC@MoO 2 -S cathode with high areal sulfur loading of 5.0 mg cm−2 achieved initial areal capacities of 4.48 mAh cm−2 and retention capacities of 3.32 mAh cm−2 after 500 cycles at 0.1 C. [Display omitted] [ABSTRACT FROM AUTHOR]

The current technology of lithium-sulfur (Li-S) batteries is hindered by the sluggish kinetics and low utilization of sulfur (S) due to its electronic insulating nature. Herein, tellurium (Te) is introduced into S by forming Te x S y solid solutions to reshape Li-S chemistry and facilitate the solid-state conversion of the cathode in carbonate-based electrolytes. Numerical calculations suggest a more delocalized charge-density difference around the Te atoms in Li 16 Te 1 S 7 compared to site-equivalent S atoms in Li 2 S, thus enabling lower energy barriers throughout the Li migration pathway. Mesoporous carbon Ketjenblack (KB) is employed to confine Te x S y materials via a melt diffusion method. By tuning the molar ratio of Te/S, it is found that the Te 1 S 7 /KB cathode delivers the highest reversible capacity of 1306.7 mAh g−1 at 0.1 A g−1 and maintains a capacity of 959.8 mAh g−1 after 400 cycles at 1 A g−1. Kinetics analysis reveals that the introduction of Te accelerates Li-ion diffusion and decreases reaction resistance during the charge/discharge process, thus enabling fast and reversible redox conversion. Moreover, the Te-containing solid electrolyte layer on the electrode surface is generated to prevent the loss of Te 1 S 7 active materials. These encouraging findings suggest that the heteroatomic Te 1 S 7 /KB is a promising cathode to achieve long cycle life and high energy density for Li-S batteries. [Display omitted] • An optimized Te x S y composite cathode is constructed for Li-S batteries. • Theoretical simulations suggest the lowered energy barrier for Li-ion migration in Te 1 S 7. • The Te x S y cathode shows significant enhancement in capacity, stability and kinetics. • A robust SEI is generated to maintain good structural integrity and prevent active materials loss. [ABSTRACT FROM AUTHOR]

In virtue of density functional theory (DFT), we theoretically predict that electron structure of Ni sites in NiMn-based metal-organic frameworks (NiMn-MOF) was favorably modulated via electron interaction between Ni ions and adjacent Mn ions, which is conducive to optimizing the adsorption energy of oxygen species on NiMn- MOF electrodes and thus decreasing the energy barrier of oxygen redox reactions. Based on the theoretical design, bimetallic coupling strategy is proposed to optimize the electrocatalytic activity of Ni-MOF via introducing secondary metal Mn ions. The spatial distribution and geometric morphology of final Li 2 O 2 species are appropriately tuned on NiMn 0.05 -MOF electrode. Moreover, lithium-oxygen batteries with NiMn 0.05 -MOF electrodes perform excellent electrochemical performance. [Display omitted] • e g orbital occupancy of Ni sites in NiMn 0.05 -MOF was modulated via electron interaction between Mn ions and adjacent Ni ions. • Bimetallic coupling strategy is proposed to optimize the electrocatalytic activity of MOF. • The adsorption of intermediate on the NiMn 0.05 -MOF was modulated. • The NiMn 0.05 -MOF electrode shows extraordinary electrocatalytic performance for ORR and OER. Rational design and synthesis of highly efficient bifunctional oxygen electrocatalysts is significant for rechargeable lithium-oxygen batteries (LOBs). In this work, a bimetal coupling strategy has been adopted to fabricate Ni/Mn bimetal-organic framework (Ni/Mn-MOF). The LOBs equipped with NiMn 0.05 -MOF electrocatalyst exhibit excellent performances with large specific capacity of 28,464 mAh/g and extraordinary stability of 524 cycles at 100 mA g−1. Combining with the experimental results and density functional theory (DFT) calculation, it is found that the doped Mn cations enable triggering the redistribution of 3d electron in Ni sites, adjusting e g orbital occupancy of Ni and strengthening the hybridization between Ni −3d and O −2p orbits due to the intense electron coupling between Ni and Mn ions, which greatly optimizes the inherent absorption capability of NiMn 0.05 -MOF for LiO 2 intermediate and thus decreases the energy barriers of oxygen redox reactions. [ABSTRACT FROM AUTHOR]

1 The strategy of modifying lithium polysulfides with cluster-type regulator to improve the performance of Li-S batteries was proposed for the first time. 2 The macromolecular LiPyS clusters have low solubility and thus can be confined to the cathode side. 3 LiPyS clusters can combine with LiPSs through double Li···S bonds to inhibit the "shuttle effect". 4 LiPyS clusters accelerate LiPSs redox kinetics based on frontier molecular orbital energy regulation strategy. Lithium polysulfide intermediates suffer from serious "shuttle effect" and slow redox kinetics, resulting in limited rate performance, low discharge capacity and rapid capacity decay of lithium-sulfur (Li-S) batteries. Here, we propose a concept of cluster-type lithium polysulfides (LiPSs) regulator to address the above-mentioned problems. Dipyridyl disulfide (DpyDS) is introduced to be an electrolyte additive to form low solubility macromolecular lithium pyridine-2-thiolate (LiPyS) clusters in electrolyte by in-situ lithiation and Li bond network. The LiPyS monomer in the clusters form complexes (LiPyS-LiPSs) with LiPSs through bi-directional Li···S bonds, so as to restrict LiPSs to the clusters on the cathode side, preventing the parasitic reaction between LiPSs and Li metal. At the same time, LiPyS-LiPSs have higher HOMO energy levels and lower LUMO energy levels than that of single LiPSs. As a result, LiPSs can achieve an enhanced redox activity, and the Li-S battery regulated with DpyDS provides a capacity as high as 900 mA h g −1 at 2 C rate. [Display omitted] [ABSTRACT FROM AUTHOR]

The electrocatalytic conversion of polysulfides is crucial to lithium-sulfur batteries and mainly occurs at triple-phase interfaces (TPIs). However, the poor electrical conductivity of conventional transition metal oxides results in limited TPIs and inferior electrocatalytic performance. Herein, a TPI engineering approach comprising superior electrically conductive layered double perovskite PrBaCo 2 O 5+δ (PBCO) is proposed as an electrocatalyst to boost the conversion of polysulfides. PBCO has superior electrical conductivity and enriched oxygen vacancies, effectively expanding the TPI to its entire surface. DFT calculation and in situ Raman spectroscopy manifest the electrocatalytic effect of PBCO, proving the critical role of enhanced electrical conductivity of this electrocatalyst. PBCO-based Li-S batteries exhibit an impressive reversible capacity of 612 mAh g -1 after 500 cycles at 1.0 C with a capacity fading rate of 0.067% per cycle. This work reveals the mechanism of the enriched TPI approach and provides novel insight into designing new catalysts for high-performance Li-S batteries.

Zn-I 2 batteries stand out in the family of aqueous Zn-metal batteries (AZMBs) due to their low-cost and immanent safety. However, Zn dendrite growth, polyiodide shuttle effect and sluggish I 2 redox kinetics result in dramatically capacity decay of Zn-I 2 batteries. Herein, a Janus separator composed of functional layers on anode/cathode sides is designed to resolve these issues simultaneously. The cathode layer of Fe nanoparticles-decorated single-wall carbon nanotubes can effectively anchor polyiodide and catalyze the redox kinetics of iodine species, while the anode layer of cation exchange resin rich in -SO 3 - groups is beneficial to attract Zn 2+ ions and repel detrimental SO 4 2- /polyiodide, improving the stability of cathode/anode interfaces synergistically. Consequently, the Janus separator endows outstanding cycling stability of symmetrical cells and high-areal-capacity Zn-I 2 batteries with a lifespan over 2500 h and a high-areal capacity of 3.6 mAh cm -2 ., (© 2023 Wiley-VCH GmbH.)

For practical lithium-sulfur batteries (LSBs), the high sulfur loading and lean-electrolyte are necessary conditions to achieve the high energy density. However, such extreme conditions will cause serious battery performance fading, due to the uncontrolled deposition of Li 2 S and lithium dendrite growth. Herein, the tiny Co nanoparticles embedded N-doped carbon@Co 9 S 8 core-shell material (CoNC@Co 9 S 8 NC) is designed to address these challenges. The Co 9 S 8 NC-shell effectively captures lithium polysulfides (LiPSs) and electrolyte, and suppresses the lithium dendrite growth. The CoNC-core not only improves electronic conductivity, but also promotes Li + diffusion as well as accelerates Li 2 S deposition/decomposition. Consequently, the cell with CoNC@Co 9 S 8 NC modified separator delivers a high specific capacity of 700 mAh g -1 with a low-capacity decay rate of 0.035% per cycle at 1.0 C after 750 cycles under a sulfur loading of 3.2 mg cm -2 and a E/S ratio of 12 µL mg -1 , and a high initial areal capacity of 9.6 mAh cm -2 under a high sulfur loading of 8.8 mg cm -2 and a low E/S ratio of 4.5 µL mg -1 . Besides, the CoNC@Co 9 S 8 NC exhibits an ultralow overpotential fluctuation of 11 mV at a current density of 0.5 mA cm -2 after 1000 h during a continuous Li plating/striping process., (© 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.)

• Redox active Cu(III) center as copper(III)-diperiodate complex (DPC) was employed as a competent oxidizing agent. • Oxidative kinetics of 1-propanol and 1,3-propanediol have been explored by DPC in binary surfactant solution. • Cationic CPC and nonionic TX-100 surfactants enable the redox transformation satisfactorily beyond their cmc value. • Equimolar ratio of CPC and TX-100 micelle conjunctively produced significant synergism effect in the oxidation. • CPC/TX-100 mixed micelle offers ∼ 25 fold rate enhancements compared to surfactant free oxidation of alcohols. The realization of employment of two surfactants in organic transformation comes from the intensity on achievement of better results with lower concentrations of individual surfactants than with single surfactants. In this work, the oxidations of 1-propanol and 1,3-propanediol by copper(III)-periodate (DPC) complex in aqueous micellar media were investigated, separately. The kinetic measurements were conducted by recording UV–visible absorbance spectra following the pseudo-first order condition. The isolated oxidized products were identified by assigning 1H NMR and FTIR studies. Both the oxidations were considerably promoted by the presence of micro-environment, constituted by CPC (cetylpyridinium chloride) and TX-100 (Triton-X 100) surfactants, individually. The maximum catalytic achievement was ascertained while both the surfactants were exist in equimolar amount in the reaction media. The aggregation of binary surfactants to produce a balanced mixed micelle is crucial to analyze the absolute kinetic results of present oxidation study. The electrostatic interaction between charged micelle and DPC facilitates to bring about the oxidizing species closest approach to the substrate (1-propanol and/or 1,3-propanediol) which are usually solubilized in micellar micro-environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A simple one-spot method is used to prepare the ultrafine Ni 2 P nanoparticles. • Theoretical calculations reveal the improved reduction kinetics of polysulfides. • Advanced Raman technology verifies the reduced shuttle effect of polysulfides. The shuttle effect and the sluggish redox kinetics of lithium polysulfides (LiPSs) are the major issues impeding the practical applications of lithium-sulfur batteries (LSBs). Herein, a highly-efficient Ni 2 P electrocatalyst supported on N, P co-doped graphene (Ni 2 P@NPG) is developed via a simple "recrystallization-self-assembly" method to address the above issues. The ultrafine Ni 2 P nanoparticles ensure abundant adsorption-diffusion-conversion interfaces for accelerating LiPSs transformation and Li 2 S deposition, which extremely decreases the accumulation of LiPSs in the electrolyte and therefore prevents the migration of LiPSs. Their superior catalytic performance is demonstrated by reduced Gibbs free energy changes of rate-limiting step based on the systematic theoretical calculations and the reduced shuttle effect is tested by the three-dimensional reconstructions of Raman depth profiles. Benefiting from these synergistic effects, the LSBs with Ni 2 P@NPG modified separators present a superior cycling performance with an average capacity decay rate of 0.048 % per cycle at 1C around the 400 cycles and a high-rate capacity of 731 mAh/g at 2C. Even with a high-sulfur loading of 3.53 mg cm−2, the cell can still contain a reversible capacity of 809 mAh/g at 0.2C with a remarkable columbic efficiency of 98.4 %. [ABSTRACT FROM AUTHOR]

Inferior specific capacity and sluggish redox kinetics are the most stubborn problems lithium-ion and lithium-sulfur batteries (LIBs and LSBs) are facing, respectively. Here we report a facile fabrication of self-supported hollow Co 3 O 4 @carbon nanotubes on carbon cloth (H-Co 3 O 4 @CNT/CC) through a mild pyrolysis-oxidation process. The additive- and binder-free H-Co 3 O 4 @CNT/CC shows excellent electrochemical performances as both LIBs and LSBs electrodes. As a robust integrated anode for LIBs, the areal capacities are 2.72 mAh cm−2 at the current density of 0.5 C over 1000 cycles. While as a durable cathode host for LSBs, favorable areal capacities of 2.37 mAh cm−2 are maintained with a low capacity decay of 0.11 % per cycle at the sulfur loading of 6 mg cm−2 and current density of 1 C after 400 cycles. Electrochemical technology, ex situ Raman spectroscopy and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC via thermodynamics and kinetics. It is demonstrated that the hierarchically hollow interior structure, strong adsorb ability of Co 3 O 4 toward polysulfides and three-dimensional (3D) inter-connected conductive carbon framework are responsible for the high areal capacity, fast redox kinetics and cycling durability. [Display omitted] • The integrated electrode possesses the merits of hollow nanostructured Co 3 O 4 and 3D inter-connected conductive network. • Electrochemical technology and DFT calculations are performed to comprehensively analyze H-Co 3 O 4 @CNT/CC. • H-Co 3 O 4 @CNT/CC delivers high areal capacities of 2.72 mAh cm-2 after 1000 cycles at 0.5 C as anode. [ABSTRACT FROM AUTHOR]

• TPPS cross-linked polypyrrole is rationally fabricated by aqueous self-assembly. • 3-D network is constructed with electron highway and reinforced conductivity. • Plenty of N sites are exposed to anchor polysulfides and release shuttle effect. • TPPS catalytically promote solid–liquid conversion between Li 2 S and polysulfides. • PPy-TPPS exhibits improved Li-S battery performances. The synergistic mechanisms of chemisorption and catalysis play an important role in developing high-performance lithium–sulfur (Li-S) batteries. To bestow conductive polymer enhanced bulk conductivity, chemisorptions to polysulfides and catalytic activity, herein, 5, 10, 15, 20-tetrakis (4-sulphophenyl) porphyrin (TPPS) cross-linked polypyrrole (PPy) nanocomposites (named PPy-TPPS) is rationally fabricated as an integrated polymeric host by aqueous self-assembly through the interaction between -SO 3 − and –NH=+. PPy-TPPS nanocomposites exhibit peag-like chain in morphology with hierarchical porous structure and high pore volume. The rigid conjugate TPPS molecules bridge linear PPy chains to extend the conjugate system, construct a multipath electron highway, create a three-dimensional conductive network and greatly reinforce the bulk conductivity of the nanocomposites. The unique structural features expose plenty of N sites to enhance the chemically anchoring polysulfides, suppress polysulfide diffusion, and release the shuttle effect. Both experimental and theoretical calculation confirms the enhanced polysulfide trapping ability. The presence of TPPS also bestows the PPy-TPPS/S cathode catalytic property to promote the Li 2 S nucleation rate and accelerate the reversible solid–liquid conversion between Li 2 S and soluble polysulfides. The improved conductivity and enhanced polysulfide affinity with catalytic property render PPy-TPPS nanocomposites improved Li-S battery performances with high specific capacity, high rate capability, and high cycling stability. The PPy-TPPS/S cathode delivers a high initial capacity of 1278 mAh∙g−1 at 0.2 C. The cathode exhibits an initial discharge capacity of 761 mAh∙g−1 at 2 C with residual capacity of 470 mAh∙g−1 after 500 cycles. The present work contributes a novel route to explore low-cost, up-scale producible and high performance polymeric sulfur host for Li-S battery. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries have received extensive attention in electrochemical energy storage systems due to their high theoretical energy density as well as natural abundance of sulfur and low cost. However, Li-S batteries exhibit rapid capacity decay and inferior rate performance due to polysulfides (LiPSs) shuttling and sluggish redox kinetics. Therefore, it is crucial that LiPSs are anchored and their conversion reactions are catalyzed in order to improve the performance of Li-S batteries. In this work, ZIF-67-derived carbon polyhedra decorated with ultrafine CoS 2 nanoparticles are interconnected by carbon nanotubes (CNTs). The uniformly distributed CoS 2 nanoparticles can immobilize LiPSs and catalyze their conversion of solid-to-liquid-to-solid reactions, which enhances the redox kinetics. Furthermore, the three-dimensional conductive network consisting of ZIF-67-derived carbon polyhedra and CNTs facilitates fast electron transport and thus leads to excellent rate and cycling performance. The cells were assembled using CoS 2 -NC@CNTs-pp and show a high initial discharge capacity of 1408.5 mAh g−1 at 0.1 C and 1186.7 mAh g−1 at 1 C, and they remain outstanding cycling stability for over 500 cycles. Even at a high C rate of 5 C, it still can deliver a high discharge capacity of 832.6 mAh g−1. This work provides an efficient route to accelerate redox conversion and suppress the shuttle effect by designing a multifunctional separator. [ABSTRACT FROM AUTHOR]

Regulating redox kinetics is able to spur the great-leap-forward development of room-temperature sodium-sulfur (RT Na-S) batteries, especially on propelling their Na-ion storage capability. Here, an innovative metal oxide kinetics accelerator, orthorhombic Nb 2 O 5 Na-ion conductor, is proposed to functionalize porous carbon nanoreactors (CNR) for S cathodes. The Nb 2 O 5 is shown to chemically immobilize sodium polysulfides via strong affinity. Theoretical and experimental evidence reveals that the Nb 2 O 5 can bidirectionally regulate redox behaviors of S cathodes, which accelerates reduction conversions from polysulfides to sulfides as well as promotes oxidation reactions from sulfides to S. In situ and ex situ characterization techniques further verify its electrochemical lasting endurance in catalyzing S conversions. The well-designed S cathode demonstrates a high specific capacity of 1377 mA h g -1 at 0.1 A g -1 , outstanding rate capability of 405 mA h g -1 at 2 A g -1 , and stable cyclability with a capacity retention of 617 mA h g -1 over 600 cycles at 0.5 A g -1 . An ultralow capacity decay rate of 0.0193% per cycle is successfully realized, superior to those of current state-of-the-art RT Na-S batteries. This design also suits emerging Na-Se batteries, which contribute to outstanding electrochemical performance as well., (© 2022 The Authors. Advanced Science published by Wiley-VCH GmbH.)

The reduction kinetics of tungsten trioxide (WO 3 ) powder using hydrogen gas was studied with titanium dioxide (TiO 2 ) or 8 mol% yttria-stabilized zirconia (8YSZ) mixed into the powder bed. TiO 2 was selected as an inert volume filler, and 8YSZ was selected to increase the ionic conductivity of the powder bed. The reduction sequence of tungsten trioxide in hydrogen is known to take place in the following steps: WO 3 → WO 2.9 → WO 2.72 → WO 2 → W. When the electronic and ionic conductivities of the mixed powder bed were both sufficiently high, reduction rates were found to increase. Specifically, reaction kinetics improved with the addition of 8YSZ to the WO 3 when compared to experiments in which TiO 2 was added to the WO 3 powder bed. Chemical reaction rates were determined by first recording changes in mass as a function of time during reduction using thermogravimetry, and then reaction rates were calculated using relevant kinetic theory. [ABSTRACT FROM AUTHOR]

Aqueous zinc batteries are among the most promising large-scale energy storage technologies but their practical application is hindered by the low redox reversibility of Zn anode in aqueous electrolytes. In this work, an indium-coated carbon-zinc composite (ICZ) anode is demonstrated with outstanding cyclic stability in classic aqueous zinc sulfate electrolytes. Compared with Zn and the carbon-zinc composite (CZ) anodes, the ICZ anode reduces the high overpotential required for Zn nucleation, and prevents high-rate HER and its related parasitic reactions, endowing high redox reversibility of the ICZ anode. Consequently, the ICZ anode enhances the cyclic stability of zinc ion batteries and zinc ion capacitors. The practical potential of the ICZ anode is demonstrated by an ICZ//porous carbon pouch cell delivering a high areal capacity of 4.7 mAh cm−2 at 6 mA cm−2. Our work provides an effective redox-kinetics regulation strategy for Zn anodes in aqueous zinc batteries. [Display omitted] • An indium-carbon composite coating layer is utilized to boost the reversibility of Zn anode. • Poor cycling stability of Zn foil is elucidated by the GCD curves and microscopy images. • High energy barrier for Zn nucleation triggers high-rate parasitic reactions. • The ICZ anode shows superior effects in suppressing parasitic reactions. • The ICZ pouch cell achieves a high areal capacity of 4.7 mAh cm−2 at 6 mA cm−2. [ABSTRACT FROM AUTHOR]

Iron(III)-containing aqueous solutions of 5-methylresorcinol (5-MR), 5- n-propylresorcinol (5- n-PR) and 4- n-hexylresorcinol (4- n-HR) at pH ~ 3 were studied by means of Fe transmission Mössbauer spectroscopy. Kinetic considerations were applied to the redox reactions. Density Functional Theory (DFT) calculations were performed for the alkylresorcinol (AR) molecules and their non-alkylated analogue (resorcinol). Mössbauer spectra consisted of quadrupole doublets assigned to high-spin Fe(III) and Fe(II) species. From changes in their relative spectral areas, a gradual reduction of Fe(III) by all the ARs studied was observed. However, significant differences were found for the reduction rates among the ARs. The following series of the reduction rates was established by means of Mössbauer spectroscopy: 4- n-HR ≫ 5-MR > 5- n-PR, supplemented by rate constants calculated using a kinetic model. DFT calculations resulted in the following series: 4- n-HR ≫ 5- n-PR > 5-MR ≫ resorcinol (the latter is not oxidised under the conditions applied). The reversed order of the experimentally observed 5-MR and 5- n-PR oxidation rates may be explained in terms of their different kinetic parameters related to their structure. [ABSTRACT FROM AUTHOR]

Developing efficient electrocatalysts to accelerate the sluggish conversion of lithium polysulfides (LiPSs) is of paramount importance for improving the performances of lithium-sulfur (Li-S) batteries. However, a consensus has not yet been reached on the in situ evolution of the electrocatalysts as well as the real catalytic active sites. Herein, defective MnV 2 O 6 (D-MVO) is designed as a precatalyst toward LiPSs' adsorption and conversion. We reveal that the introduction of surface V defects can effectively accelerate the in situ sulfurization of D-MVO during the electrochemical cycling process, which acts as the real electrocatalyst for LiPSs' retention and catalysis. The in situ-sulfurized D-MVO demonstrates much higher electrocatalytic activity than the defect-free MVO toward LiPSs' redox conversion. With these merits, the Li-S batteries with D-MVO separators achieve superior long-term cycling performance with a low decay rate of 0.056% per cycle after 1000 cycles at 1C. Even under an elevated sulfur loading of 5.5 mg cm -2 , a high areal capacity of 4.21 mAh cm -2 is still retained after 50 cycles at 0.1C. This work deepens the cognition of the dynamic evolution of the electrocatalysts and provides a favorable strategy for designing efficient precatalysts for advanced Li-S batteries using defect engineering.

It is now well established that Iron (Fe) is a limiting element in many regions of the open ocean. Our current understanding of the key processes which control iron distribution in the open ocean have been largely based on thermodynamic measurements performed under the assumption of equilibrium conditions. Using this equilibrium approach, researchers have been able to detect and quantify organic complexing ligands in seawater and examine their role in increasing the overall solubility of iron. Our current knowledge about iron bioavailability to phytoplankton and bacteria is also based heavily on carefully controlled laboratory studies where it is assumed the chemical species are in equilibrium in line with the free ion association model (FIAM) and/or its successor the biotic ligand model (BLM). Similarly most field work on Fe biogeochemistry generally consists of a single profile which is in essence a ‘snap-shot’ in time of the system under investigation. However it is well known that the surface ocean is an extremely dynamic environment and it is unlikely if thermodynamic equilibrium between all the iron species present is ever truly achieved. In sunlit waters this is mostly due to the daily passage of the sun across the sky leading to photoredox processes which alter Fe speciation by cycling between redox states and between inorganic and organic species. Episodic deposition events, are also important perturbations to iron cycling as they bring new iron to the system altering the equilibrium between species and phases. Over the last 20 years the mesoscale iron enrichment experiments (e.g. IronEx I /II, SOIREE, EisenEx, SOFeX, EIFeX, SAGE, SEEDS and SERIES I /II) and the FeCycle (I/II) experiments have provided the first insights into processes altering iron speciation and distribution which occur over temporal scales of days to weeks. Here we utilize new field data collected in the open ocean on the redox and complexation kinetics of iron in the euphotic zone.

• The ultrathin V 2 CT x nanoribbons were etched successfully for the first time. • V 2 CT x nanoribbons expose more active sites for LiPSs anchoring. • V 2 CT x /CNT modified layer can facilitate the LiPSs conversions and induce the Li 2 S homogeneous nucleation. • The Li–S batteries with V 2 CT x /CNT modified separator present outstanding rate performance and cycling stability. The worldwide application of lithium-sulfur (Li–S) batteries is severely hampered by the low utilization of sulfur, rapid capacity fading, and poor rate performance. Herein, an efficient functional V 2 CT x /CNT framework is constructed and employed as an anchoring-catalysis modified layer of the separator to improve the performance of Li–S batteries. CNT acts as the foundation of the structure due to its impressive conductivity, continuous framework, and satisfactory mechanical stability, which provides a conductive surface and prevents the structure from collapsing during cycling progress as well. While V 2 CT x nanoribbons, strengthen the chemical anchoring to lithium polysulfides (LiPSs), facilitate the further conversions of the LiPSs in the liquid phase, and induce the Li 2 S homogeneous nucleation, restraining the shuttle effect and accelerating redox reactions. Benefiting from the anchoring-catalysis effect, the Li–S battery with V 2 CT x /CNT separator delivers an outstanding rate performance of 893.6 mAh g−1 at 2 C. The average capacity decay per cycle within 1000 cycles at 1 C is as low as 0.047%. This work provides a rewarding view to develop the practical application of Li–S batteries with a functional separator. [ABSTRACT FROM AUTHOR]

Nickel-rich layered cathode is a forefront candidate for lithium-ion batteries; however, structural degradation such as intragranular cracking and phase transition in polycrystals focus researchers' attention towards single-crystals. Nevertheless, the sluggish ionic transport and redox kinetics in single-crystals hinder their rate capability and electrochemical performance in harsh conditions. Herein, a synergy of gradient Nb doping on single-crystal LiNi 0.8 Co 0.1 Mn 0.1 O 2 stabilizes the core by strong Nb-O bond and induces Li/Ni antisite migration forming a disordered buffer layer on the surface. The disordered structure maintains the structural integrity by suppressing the phase transition and triggering the Li+ transport. Thus, the modified single-crystal (SNCM@Nb-2) delivers remarkable capacity retention of 92.54% after 100 cycles at 1 C between 2.7 and 4.3 V@ 25 °C (84.26% for SNCM, respectively) and 86.7% at an elevated temperature of 55 °C (SNCM 76.69%). The fast redox kinetics results in remarkably enhanced rate capability and ultra-stable high voltage performance at 4.5 V with SNCM@Nb-2 delivers an initial discharge capacity of 285.2 mAh g−1 with retention of 79.8% (SNCM with 192.1 mAh g−1, 64.1%). The findings of this study provide advancement for the inadequate kinetic properties of single-crystal Ni-rich cathodes under harsh operational conditions. [Display omitted] • Single crystal NCM811 was modified by gradient doping of high-valent Nb5+. • Nb5+ reduces Ni and facilitate Li/Ni antisite defect formation. • Li/Ni antisite migration results in a disordered buffer layer on the surface. • Stronger Nb-O retain surface oxygen, maintaining the structural integrity. [ABSTRACT FROM AUTHOR]

Lithium-sulfur (Li-S) batteries (LSBs) have been considered one of the most potential candidates to substitute traditional Li-ion batteries (LIBs), owing to their high theoretical energy density and low cost. Nevertheless, the shuttle effect and the sluggish redox kinetics of lithium polysulfides (LiPSs) have long been obstacles to realizing stable LSBs with high reversible capacity. In this study, we proposed a metal-semiconductor (Mo and MoO 2 ) heterostructure with the hollow microsphere morphology as an effective Mott-Schottky electrocatalyst to boost sulfur electrochemistry. The hollow structure can physically inhibit the shuttling of LiPSs and accommodate the volume fluctuation during cycling. More importantly, the built-in electric field at the heterointerfacial sites can effectively accelerate the reduction of LiPSs and oxidation of Li 2 S, thereby reaching a high sulfur utilization. With the assistance of the Mo/MoO 2 catalyst, the cell exhibited prominent rate capability and stable long-term cycling performance, showing a high capacity of 630 mA h·g -1 at 4 C and a low decay of 0.073% at 1 C after 500 cycles. Even with high areal sulfur loading of 10.0 mg·cm -2 , high capacity and good cycle stability were achieved at 0.2 C under lean electrolyte conditions (E/S ratio of 6 μL·mg -1 ).

Although single-atom catalysts (SACs) have been largely explored in lithium-sulfur (Li-S) batteries, the commonly reported nonpolar transition metal-N 4 coordinations only demonstrate inferior adsorption and catalytic activity toward shuttled lithium polysulfides (LiPSs). Herein, single Fe atoms with asymmetric coordination configurations of Fe-N 3 C 2 -C were precisely designed and synthesized as efficient immobilizer and catalyst for LiPSs. The experimental and theoretical results elucidate that the asymmetrically coordinated Fe-N 3 C 2 -C moieties not only enhance the LiPSs anchoring capability by the formation of extra π-bonds originating from S p orbital and Fe d x 2 - y 2 /d xy orbital hybridization but also boost the redox kinetics of LiPSs with reduced Li 2 S precipitation/decomposition barrier, leading to suppressed shuttle effect. Consequently, the Li-S batteries assembled with Fe-N 3 C 2 -C exhibit high areal capacity and cycling stability even under high sulfur loading and lean electrolyte conditions. This work highlights the important role of coordination symmetry of SACs for promoting the practical application of Li-S batteries.

The article discusses selective catalytic reduction (SCR) of nitrogen oxides that are emitted from diesel engines. It describes the application of a dynamic Mars-van Krevelen kinetic model that accounts for standard and fast SCR reactions for vanadium-based catalysts. The article explains the catalytic chemistry represented by the model and estimation of kinetic parameters by global multi-response nonlinear regression. The model is said to reproduce the SCR reaction system and account for SCR process stoichiometry, selectivity, and kinetics.

Lithium-sulfur (Li-S) batteries have become one of the most promising next-generation battery systems. Nevertheless, Li-S batteries are still restricted by the dissolution and 'shuttling' of intermediate electrochemical products, lithium polysulfides (LiPSs), and the sluggish redox kinetics. Herein, we design a Nb 2 C/Nb 2 O 5 heterostructure via water-steam etching at the first time to achieve fast trapping-diffusion-conversion of LiPSs by combining the trapping ability of Nb 2 C with catalytic activity of Nb 2 O 5 toward LiPSs. The porous structure form in the water-steam etching process and the accordion-like structure can effectively contribute to the Li+ transportation enhancement. Nb 2 C nanosheets with high conductivity provide the basal planes for Nb 2 O 5 contact, which suppresses the aggregation of Nb 2 O 5 nanoparticles, leading to the overall structural and interface stabilization. In addition, the heterostructured interface ensures a rapid diffusion of anchored LiPSs. Benefiting from synergetic contributions of the above merits, Li-S batteries with the S-Nb 2 C/Nb 2 O 5 electrode display a superior electrochemical performance with large initial discharge capacity of 844 mAh g−1 with a low capacity fading rate of only 0.05% per cycle during 500 cycles at 1.0 C. This work holds considerable instructive toward development of high-performance Li-S batteries. [Display omitted] • The accordion-like Nb 2 C/Nb 2 O 5 was prepared via water-steam etching method. • Nb 2 C/Nb 2 O 5 offered enhanced trapping effect and redox conversion of LiPSs. • Li-S battery with S-Nb 2 C/Nb 2 O 5 exhibited excellent electrochemical performance. [ABSTRACT FROM AUTHOR]

1 Preparation of Li 1+x Mn 2 O 4 material by in-situ lithiation. 2 Li 1+x Mn 2 O 4 has better electronic conductivity and LiPSs adsorpting capability than LiMn 2 O 4. 3 The lithiation strategy can achieve fast LiPSs converting kinetics and low Li+ diffusion barrier. 4 Li 1+x Mn 2 O 4 CNF@S electrodes have outstanding rate performance and long cycle stability. Lithium-sulfur (Li-S) battery is one of the most promising candidates for the next generation energy storage systems. However, the inherent slow redox kinetics of sulfur leads to limited rate performance, low discharge capacity and rapid capacity fading. Herein, the Li 1+x Mn 2 O 4 material produced by in-situ lithium intercalation of LiMn 2 O 4 before 2.5 V is selected to improve the performances of Li-S batteries. First-principles calculations show that Li 1+x Mn 2 O 4 can improve electronic conductivity and chemical adsorption. Electrochemical characterizations further confirm that lithiated material provides a fast conversion kinetics for LiPSs and a low barrier of lithium-ion diffusion. As a result, the Li-S battery incorporating Li 1+x Mn 2 O 4 presents excellent rate performance with a discharge capacity as high as 915 mAh g −1 at 2 C rate. At the same time, the battery maintains a high reversible capacity of 531 mAh g −1 after 1000 cycles at 1 C rate, and the average capacity loss per cycle is only 0.047%. This work can improve the redox kinetics of sulfur cathodes and provide a new path for the advancement of high-performance Li-S batteries. [Display omitted] [ABSTRACT FROM AUTHOR]

Catalysis is a fundamental solution in suppressing the shuttling of lithium polysulfides (LiPSs), which is essential to the practical applications of lithium-sulfur batteries with high energy density. However, the uncontrollable deposition of electronic and ionic insulative Li 2 S always passivates the catalyst surface for the continuous LiPS conversion. Herein, we propose an effective method to regulate Li 2 S deposition to avoid the catalyst surface passivation by introducing grain boundaries (GBs) in the catalyst. Hollow microspheres composed of MoN-Mo 2 N heterostructure with abundant and highly accessible GBs were prepared as the models. The results show GBs act as the two-dimensional nucleation sites, guiding the fast nucleation and three-dimensional deposition of Li 2 S around them, avoiding the formation of dense Li 2 S coating on their surface. Thus, the high capacity Li 2 S deposition with enhanced conversion kinetics was achieved. The interlayer composed of the above catalyst and carbon nanotube effectively suppresses the shuttling of LiPSs and promotes their fast conversion, leading to a low capacity decay of 0.049% per cycle at 1 C for 800 cycles for the assembled battery. With a higher sulfur loading of 4.7 mg cm−2 under 0.5 C, high capacity retention of 77.2% after 200 cycles could also be achieved. [Display omitted] • The MoN-Mo 2 N catalyst with abundant grain boundaries (GBs) was prepared. • The rich GBs guide the three-dimensional and high capacity Li 2 S deposition. • The Li-S batteries with MoN-Mo 2 N based interlayer show good reversibility and cycling stability. [ABSTRACT FROM AUTHOR]

Abstract: The primary goal of this work has been to electrochemically form and then characterize a composite polyaniline (PANI)/hydrous Ir oxide (IrOx) film. Efforts to electrochemically form IrOx and PANI simultaneously in acidic aniline-containing solutions failed, likely as aniline adsorption on Ir prevents IrOx formation. Successful composite films were therefore made by first forming an anodic IrOx film on bulk Ir and then depositing PANI into its pores. Based on the characteristics of the PANI redox peaks, it is seen that all of the PANI film that is electrochemically active is in direct electrical contact with the Ir surface at the base of the IrOx film pores. This is consistent with the cross-sectional SEM and EDX analyses, showing the formation of films of uniform thickness and composition. Thin films of Ir nanoparticles, subsequently converted to IrOx, were also used as a template for PANI formation within the porous structure. These hybrid films exhibit an enhanced internal porosity, ease of multiple coating formation (up to 20μm in thickness), high charge densities, unusual electrochromic behavior, and very rapid charge transfer kinetics. The formation of composite IrOx/PANI films also resulted in a widening (by 0.3–0.4V) of the potential window over which a pseudocapacitive and electrochromic response is seen. [Copyright &y& Elsevier]

Abstract: Upon reduction, originally fully transparent and insulating ytterbium alumina garnet single crystals, Yb3Al5O12, become deeply colored and electrically conducting with a conductivity of the order of 10−3 Ω−1 cm−1 in the temperature range of 550°C to 1000°C. The redox kinetics of the material is studied by means of conductivity relaxation experiments performed at oxidising and reducing conditions. Good agreement is obtained with an optical study into the redox kinetics of Yb3Al5O12. [Copyright &y& Elsevier]

We present transient kinetic data that demonstrate an inhibiting effect of ammonia on the NH3-selective catalytic reduction (SCR) of nitric oxide (NO) at low temperatures over a V2O5-WO3/TiO2 commercial catalyst for vehicles. This effect has significant mechanistic as well as practical implications. It cannot be reproduced by conventional or modified Eley--Rideal approaches used in the past for SCR-deNOx stationary applications, but is well described by a novel dual-site redox rate expression assuming that ammonia may block the vanadium-related catalyst sites for NO + NH3 activation. The same rate model also successfully represents the kinetic influence of the oxygen concentration. It is shown that account of ammonia inhibition at low temperatures is critical for simulating the highly transient operation of onboard SCR converters for diesel exhaust aftertreatment. [ABSTRACT FROM AUTHOR]

The electrode reaction of glutathione (GSH) at the hanging mercury drop electrode is studied by means of square-wave voltammetry (SWV). At potentials more positive than -0.350 V (vs. Ag/AgCl (3 mol/l KCl)) the oxidation of the mercury electrode in the presence of GSH leads to creation of a sparingly soluble mercury–GSH complex that deposits onto the electrode surface. Under cathodic potential scan, the deposited complex acts as a reducible reactant, giving raise to a well-defined cathodic stripping reversible SW voltammetric response. The electrode reaction can be described by the scheme: Hg(SG)2(s)+e-+2H(aq)+=Hg(l)+2GSH(aq). Thus, the electrode reaction provides information on both thermodynamics and kinetics of the chemical interactions of GSH with mercury. An experimental methodology for measuring the kinetics of the electrode reactions, based on the property known as “quasireversible maximum”, is developed. The standard redox rate constant is 5.09, 5.75 and 5.22 cm s-1 in a phosphate buffer at pH 5.6, 7.0 and 8.5, respectively, with a precision of ±10%. The high rate of the electrode reaction reflects the strong affinity of GSH towards chemical interaction with mercury. The electrode reaction is particularly sensitive to the presence of heavy metal ions such as Cu2+, Cd2+, and Zn2+. The rate of the electrode reaction decreases significantly in the presence of these ions due to simultaneous interactions of GSH with the respective ion and mercury. [Copyright &y& Elsevier]