Tuning the crystallinity of titanium nitride on copper-embedded carbon nanofiber interlayers for accelerated electrochemical kinetics in lithium-sulfur batteries

The development of lithium-sulfur(Li-S)batteries is hindered by the disadvantages of shuttling of polysulfides and the sluggish redox kinetics of the conversion of sulfur species during discharge and charge.Herein,the crystallinities of a titanium nitride(TiN)film on copper-embedded carbon nanofibers(Cu-CNFs)are regulated and the nanofibers are used as interlayers to resolve the aforementioned crucial issues.A low-crystalline TiN-coated Cu-CNF(L-TiN-Cu-CNF)interlayer is compared with its highly crystalline counterpart(H-TiN-Cu-CNFs).It is demonstrated that the L-TiN coating not only strengthens the chemical adsorption toward polysulfides but also greatly accelerates the electrochemical conversion of polysulfides.Due to robust carbon frameworks and enhanced kinetics,impressive highrate performance at 2 C(913 mAh g^(-1)based on sulfur)as well as remarkable cyclic stability up to 300 cycles(626 mAh g^(-1))with capacity retention of 46.5%is realized for L-TiN-Cu-CNF interlayer-configured Li-S batteries.Even under high loading(3.8 mg cm^(-2))of sulfur and relatively lean electrolyte(10μL electrolyte per milligram sulfur)conditions,the Li-S battery equipped with L-TiN-Cu-CNF interlayers delivers a high capacity of 1144 mAh g^(-1)with cathodic capacity of 4.25 mAh cm^(-2)at 0.1 C,providing a potential pathway toward the design of multifunctional interlayers for highly efficient Li-S batteries.

Geochemical modeling to aid experimental design for multiple isotope tracer studies of coupled dissolution and precipitation reaction kinetics

It is a challenge to make thorough but efficient experimental designs for the coupled mineral dissolution and precipitation studies in a multi-mineral system, because it is difficult to speculate the best experimental duration, optimal sampling schedule, effects of different experimental conditions, and how to maximize the experimental outputs prior to the actual experiments. Geochemical modeling is an efficient and effective tool to assist the experimental design by virtually running all scenarios of interest for the studied system and predicting the experimental outcomes. Here we demonstrated an example of geochemical modeling assisted experimental design of coupled labradorite dissolution and calcite and clayey mineral precipitation using multiple isotope tracers. In this study, labradorite(plagioclase) was chosen as the reactant because it is both a major component and one of the most reactive minerals in basalt. Following our isotope doping studies of single minerals in the last ten years, initial solutions in the simulations were doped withmultiple isotopes(e.g., Ca and Si). Geochemical modeling results show that the use of isotope tracers gives us orders of magnitude more sensitivity than the conventional method based on concentrations and allows us to decouple dissolution and precipitation reactions at near-equilibrium condition. The simulations suggest that the precise unidirectional dissolution rates can inform us which rate laws plagioclase dissolution has followed. Calcite precipitation occurred at near-equilibrium and the multiple isotope tracer experiments would provide near-equilibrium precipitation rates, which was a challenge for the conventional concentration-based experiments. In addition, whether the precipitation of clayey phases is the rate-limiting step in some multi-mineral systems will be revealed. Overall, the modeling results of multimineral reaction kinetics will improve the understanding of the coupled dissolution–precipitation in the multi-mineral systems and the quality of geochemical modeling prediction of CO_(2) removal and storage efficacy in the basalt systems.

The autophagy-lysosome pathway:a potential target in the chemical and gene therapeutic strategies for Parkinson’s disease

Parkinson’s disease is a common neurodegenerative disease with movement disorders associated with the intracytoplasmic deposition of aggregate proteins such asα-synuclein in neurons.As one of the major intracellular degradation pathways,the autophagy-lysosome pathway plays an important role in eliminating these proteins.Accumulating evidence has shown that upregulation of the autophagy-lysosome pathway may contribute to the clearance ofα-synuclein aggregates and protect against degeneration of dopaminergic neurons in Parkinson’s disease.Moreover,multiple genes associated with the pathogenesis of Parkinson’s disease are intimately linked to alterations in the autophagy-lysosome pathway.Thus,this pathway appears to be a promising therapeutic target for treatment of Parkinson’s disease.In this review,we briefly introduce the machinery of autophagy.Then,we provide a description of the effects of Parkinson’s disease–related genes on the autophagy-lysosome pathway.Finally,we highlight the potential chemical and genetic therapeutic strategies targeting the autophagy–lysosome pathway and their applications in Parkinson’s disease.

Modeling of Soot Formation in Gas Burner Using Reduced Chemical Kinetics Coupled with CFD Code

A computational study of soot formation in ethylene/air coflow jet diffusion flame at atmospheric pres-sure was conducted using a reduced mechanism and soot formation model. A 20-step mechanism was derived from the full mechanism using sensitivity analysis,reaction path analysis and quasi steady state(QSS) approximation. The model in premixed flame was validated and with computing savings in diffusion flame was applied by incor-porating into a CFD code. Simulations were performed to explore the effect of coflow air on flame structure and soot formation. Thermal radiation was calculated by a discrete-ordinates method,and soot formation was predicted by a simple two-equation soot model. Model results are in good agreement with those from experiment data and detailed mechanism at atmospheric conditions. The soot nucleation,growth,and oxidation by OH are all enhanced by decrease in coflow air velocity. The peak soot volume fraction region appears in the lower annular region be-tween the peak flame temperature and peak acetylene concentration locations,and the high soot oxidation rate due to the OH attack occurs in the middle annular region because of high temperature.

Decomposition kinetics of dimethyl methylphospate(chemical agent simulant) by supercritical water oxidation

Supercritical water oxidation （SCWO） has been drawing much attention due to effectively destroy a large variety of high-risk wastes resulting from munitions demilitarization and complex industrial chemical. An important design consideration in the development of supercritical water oxidation is the information of decomposition rate. In this paper, the decomposition rate of dimethyl methylphosphonate（DMMP）, which is similar to the nerve agent VX and GB（Sarin） in its structure, was investigated under SCWO conditions. The experiments were performed in an isothermal tubular reactor with a H2O2 as an oxidant. The reaction temperatures were ranged from 398 to 633℃ at a fixed pressure of 24 MPa. The conversion of DMMP was monitored by analyzing total organic carbon （TOC） on the liquid effluent samples. It is found that the oxidative decomposition of DMMP proceeded rapidly and a high TOC decomposition up to 99.99% was obtained within 11 s at 555℃. On the basis of data derived from experiments, a global kinetic equation for the decomposition of DMMP was developed. The model predictions agreed well with the experimental data.

Kinetics of the electrochemical process of galena electrodes in the diethyldithiocarbamate solution

The electrochemical process of galena in a pH 12.8 buffer solution was investigated using chronoamperometry and chronopotentiometry. To establish kinetic parameters on the surface of galena in the diethyldithiocarbamate solution, the exchange current density and the dependence of current density on reaction time were determined. Experimental results demonstrate that the exchange current density of galena is 1.585× 10^-2A/m2 in the diethyldithiocarbamate-free solution. In the diethyldithiocarbamate solution, the thickness of lead diethyldi- thiocarbamate adsorbed on the surface of galena is 3.28 molecular layers, the diffusion coefficient of diethyldithiocarbamate on the surface of galena electrodes is 1.13 × 10^-10 m2/s, and the exchange current density of galena is 0.45 A/m2. Lead diethyldithiocarbamate on the surface of galena is firmly adsorbed.

Gaseous and Electrochemical Hydrogen Storage Kinetics of As-quenched Nanocrystalline and Amorphous Mg_2Ni-type Alloys

The nanocrystalline and amorphous Mg2Ni-type Mg2Ni1-xCox （x = 0, 0.1, 0.2, 0.3, 0.4） alloys were synthesized by melt quenching technology. The structures of the as-cast and quenched alloys were characterized by XRD, SEM and HRTEM. The gaseous hydrogen storage kinetics of the alloys was measured using an automatically controlled Sieverts apparatus. The alloy electrodes were charged and discharged with a constant current density in order to investigate the electrochemical hydrogen storage kinetics of the alloys. The results demonstrate that the substitution of Co for Ni results in the formation of secondary phases MgCo2 and Mg instead of altering the major phase Mg2Ni. No amorphous phase is detected in the as-quenched Co- ffee alloy, however, a certain amount of amorphous phase is clearly found in the as-quenched alloys substituted by Co. Furthermore, both the rapid quenching and the Co substitution significantly improve the gaseous and electrochemical hydrogen storage kinetics of the alloys, for which the notable increase of the hydrogen diffusion coefficient （D） along with the limiting current density （IL） and the obvious decline of the electrochemical impedance generated by both the Co substitution and the rapid quenching are basically responsible.

Kinetics of chemical leaching of chalcopyrite from low grade copper ore: behavior of different size fractions

The kinetics of the chemical leaching of copper from low grade ore in ferric sulfate media was investigated using the constrained least square optimization technique. The experiments were carried out for different particle sizes in both the reactor and column at constant oxidation-reduction potential （Eh）, pH values, and temperature. The main copper mineral was chalcopyrite. About 40% of Cu recovery is obtained after 7 d of reactor leaching at 85℃ using -0.5 mm size fraction, while the same recovery is obtained at 75℃ after 24 d. Also, about 23% of Cu recovery is obtained after 60 d of column leaching for ＋4--8 mm size fraction whereas the Cu recovery is as low as about 15% for ＋8--12.7 and ＋12.7--25 mm size fractions. A 4-stage model for chalcopyrite dissolution was used to explain the observed dissolution behaviors. The results show that thick over-layers of sulphur components cause the parabolic behavior of chalcopyrite dissolution and the precipitation of Fe3＋ plays the main role in chalcopyrite passivation. In the case of coarse particles, transformation from one stage to another takes a longer time, thus only two stages including the initial reaction on fresh surfaces and S0 deposition are observed.

A Surface Femtosecond Two-Photon Photoemission Spectrometer for Excited Electron Dynamics and Time-Dependent Photochemical Kinetics

A surface femtosecond two-photon photoemission （2PPE） spectrometer devoted to the study of ultrafast excited electron dynamics and photochemical kinetics on metal and metal oxide surfaces has been constructed. Low energy photoelectrons are measured using a hemispherical electron energy analyzer with an imaging detector that allows us to detect the energy and the angular distributions of the photoelectrons simultaneously. A Mach-Zehnder interferom- eter was built for the time-resolved 2PPE （TR-2PPE） measurement to study ultrafast surface excited electron dynamics, which was demonstrated on the Cu（111） surface. A scheme for measuring time-dependent 2PPE （TD-2PPE） spectra has also been developed for studies of surface photochemistry. This technique has been applied to a preliminary study on the photochemical kinetics on ethanol/TiO2（110）. We have also shown that the ultrafast dynamics of photoinduced surface excited resonances can be investigated in a reliable way by combining the TR-2PPE and TD-2PPE techniques.

Growth kinetics of Thiobacillus ferrooxidans in bioelectrochemical cell

Thiobacillus ferrooxidans might be the most important bacteria used in biometallurgy. The foundation way of its growth process is oxidizing ferrous in order to obtain energy needed for metabolism, but the variation of ferrous concentration and mixed potential of the culture media would have crucial effect on the bacteria growth. Based on the characteristics of Thiobacillus ferrooxidans growth and redox potential of ferric and ferrous, an electrochemical cell was designed conventionally to study growth rule and the relationship between redox potential and bacteria growth was built up, and some growth kinetics of Thiobacillus ferrooxidans were elucidated. It demonstrates that the variation of open potential of electrochemical cell Δ E shows the growth tendency of Thiobacillus ferrooxidans , at the initial growth stage, the value of Δ E increases slowly, when at logistic growth stage, it increases drastically, and the growth rate of bacteria is linear with the oxidation rate of ferrous. The bacteria growth kinetics model is proposed using Monod and Michealis-Menten equation, and the kinetics parameters are got. The consistence of the measured and the calculated results proves that it is proper to use the proposed kinetics model and the electrochemical cell method to describe the growth rule of Thiobacillus ferrooxidans .

Isothermal kinetics of mechanochemically and thermally synthesized Ag from Ag_2O

The kinetics of isothermal reduction of Ag2O with graphite under argon atmosphere for a non-activated sample and mechanically activated sample was investigated.It is found that Johnson-Mehl-Avrami model appropriately explained the thermal and mechanochemical synthesis of Ag from Ag2O＋ghraphite mixture.The process kinetics was investigated using the same approach for milled and unmilled samples.The results show that the Avrami exponent of mechanochemical reduction is higher than that of high temperature thermal reduction.Also,the mechanisms of nuclei growth in thermal and mechanochemical reduction are diffusion controlled and interface controlled,respectively.

Kinetics and Modeling of Chemical Leaching of Sphalerite Concentrate Using Ferric Iron in a Redox-controlled Reactor

This work presents a study for chemical leaching of sphalerite concentrate under various constant Fe3+ concentrations and redox potential conditions. The effects of Fe3+ concentration and redox potential on chemical leaching of sphalerite were investigated. The shrinking core model was applied to analyze the experimental results. It was found that both the Fe3+ concentration and the redox potential controlled the chemical leaching rate of sphalerite. A new kinetic model was developed, in which the chemical leaching rate of sphalerite was proportional to Fe3+ concentration and Fe3+ /Fe2+ ratio. All the model parameters were evaluated from the experimental data. The model predictions fit well with the experimental observed values.

Nd–Mg–Ni alloy electrodes modified by reduced graphene oxide with improved electrochemical kinetics

To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.

Well-ordered layered LiNi0.8Co0.1Mn0.1O2 submicron sphere with fast electrochemical kinetics for cathodic lithium storage

Nickel-rich layered oxides have drawn sustainable attentions for lithium ion batteries owing to their higher theoretical capacities and lower cost.However,nickel-rich layered oxides also have exposed several defects for commercial application,such as uncontrollable ordered layered structure,which leads to higher energy barrier for Li+diffusion.In addition,suffering from structural mutability,the bulk nickelrich cathode materials likely trigger overall volumetric variation and intergranular cracks,thus obstructing the lithium ion diffusion path and shortening the service life of the whole device.Herein,we report wellordered layered Li Ni0.8Co0.1Mn0.1O2 submicron spheroidal particles via an optimized co-precipitation and investigated as LIBs cathodes for high-performance lithium storage.The as-fabricated Li Ni0.8Co0.1Mn0.1O2 delivers high initial capacity of 228 mAh g–1,remarkable energy density of 866 Wh kg–1,rapid Li ion diffusion coefficient(10–9cm2s–1)and low voltage decay.The remarkable electrochemical performance should be ascribed to the well-ordered layered structure and uniform submicron spheroidal particles,which enhance the structural stability and ameliorate strain relaxation via reducing the parcel size and shortening Li-ion diffusion distance.This work anticipatorily provides an inspiration to better design particle morphology for structural stability and rate capability in electrochemistry energy storage devices.

EFFECTIVE SOLUTION METHOD OF CHEMICAL REACTION KINETICS WITH DIFFUSE

The time integration method with four-order accuracy, self-starting and implicit for the diffuse chemical reaction kinetics equation or the transient instantaneous temperature filed equation was presented. The examples show that both accuracy and stability are better than Runge-Kutta method with four-order. The coefficients of the equation are stored with sparse matrix pattern, so an algorithm is presented which combines a compact storage scheme with reduced computation cost. The computation of the competitive and consecutive reaction in the rotating packed bed, taken as examples, shows that the method is effective.

Single-atomic tungsten-doped Co_(3)O_(4) nanosheets for enhanced electrochemical kinetics in lithium–sulfur batteries

The practical application of lithium–sulfur batteries(LSBs)is severely hindered by the undesirable shuttling of lithium polysulfides(LiPSs)and sluggish redox kinetics of sulfur species.Herein,a series of ultrathin singleatomic tungsten-doped Co_(3)O_(4)(Wx-Co_(3)O_(4))nanosheets as catalytic additives in the sulfur cathode for LSBs are rationally designed and synthesized.Benefiting from the enhanced catalytic activity and optimized electronic structure by W doping,the Wx-Co_(3)O_(4) not only reduces the shuttling of LiPSs but also decreases the energy barrier of sulfur redox reactions of sulfur species,leading to accelerated electrode kinetic.As a result,LSB cathodes with the use of 5.0 wt%W0.02-Co_(3)O_(4) as the electrocatalyst show the high reversible capacities of 1217.0 and 558.6 mAh g^(-1) at 0.2 and 5.0 C,respectively,and maintain a high reversible capacity of 644.6 mAh g^(-1) at 1.0 C(1.0 C=1675 mA g^(-1))after 500 cycles.With a high sulfur loading of 5.5 mg cm^(-2) and electrolyte–electrode ratio of 8μL_(electrolyte) mg_(sulfur)^(-1),the 5.0 wt%W_(0.02)-Co_(3)O_(4)-based sulfur cathode also retains a high reversible areal capacity of 3.86 mAh cm^(-2) at 0.1 C after 50 cycles with an initial capacity retention of 84.7%.

Performance of a high-rate anammox reactor under high hydraulic loadings: Physicochemical properties, microbial structure and process kinetics

In this study, a lab-scale upflow anaerobic sludge blanket(UASB) reactor was applied to studying the high-rate nitrogen removal of granule-based anammox process. The nitrogen removal rate(NRR) finally improved to 15.77 kg/m3/d by shortening hydraulic retention time(HRT) to 1.06 h. Well-shaped red anammox granules were extensively enriched inside the reactor. The results of nitrogen removal kinetics indicated that the present bioreactor has great nitrogen removal potential, because the maximum rate of substrate utilization(Umax) predicted by Stover-Kincannon model is suggested as 55.68 kg/(m3·d). Analysis of the microbial community showed that the anammox genus Candidatus Kuenenia dominated the bacterial communities. The relative abundance of Candidatus Kuenenia rose from 12.29% to 36.95% after progressively shorter HRT and higher influent substrate concentrations, illustrating the stability of nitrogen removal performance and biomass enrichment offered by the UASB in carrying out high-rate anammox process.

A tool model for predicting atmospheric chemical kinetics with sensitivity analysis

A package(a tool model) for program of predicting atmospheric chemical kinetics with sensitivity analysis is presented. The new direct method of calculating the first order sensitivity coefficients using sparse matrix technology to chemical kinetics is included in the tool model, it is only necessary to triangularize the matrix related to the Jacobian matrix of the model equation. The Gear type procedure is used to integrate a model equation and its coupled auxiliary sensitivity coefficient equations. The FORTRAN subroutines of the model equation, the sensitivity coefficient equations, and their Jacobian analytical expressions are generated automatically from a chemical mechanism. The kinetic representation for the model equation and its sensitivity coefficient equations, and their Jacobian matrix is presented. Various FORTRAN subroutines in packages, such as SLODE, modified MA28, Gear package, with which the program runs in conjunction are recommended. The photo\|oxidation of dimethyl disulfide is used for illustration.

Numerical study of CNG engine combustion using CFD with detailed chemical kinetics

A three dimensional model which considers the effects of turbulence and detailed chemi cal kinetics is built to simulate the combustion process of engine fueled by compressed nature gas （CNG）. The model is accomplished by integrating CFD software KIVA3V and chemical kinetic soft- ware CHEMKINII. Meanwhile, a turbulence combustion model which is suitable for describing the reaction rate under the coupled simulation is developed to balance the effects of turbulence and de tailed chemical kinetics. To reduce the computation time, subsequent development of the simulation code is realized, which enables the simulation code to have the function of parallel computing and run on parallel computing facility based on message passing interface （MPI）. The coupled software is used to simulate the combustion process of spark ignition CNG engine. The results show that sim ulation data have a good consistency with experimental results and parallel computing has good effi ciency and accelerate ratio.

Chemical Kinetics for NO Emissions in System of Methane-Air Turbulent-Jet Diffusion Flame

An explicit expression for local, instantaneous NO production rate model was proposed to simulate NO formation in turbulent methane-air combustion. The average production rates of mixture fraction and scalar dissipation were obtained from asymptotes through approximation of two single-variable probability-density function. The theory predicted significant contributions from the Zeldovich mechanism, but negligible contributions from the nitrous-oxide mechanism in the oxygenconsumption zone. The proposed model was used to simulate NO formation in the pilot methane-air jet diffusion combustion. The simulation results were compared with those obtained by the CFD software FLUENT module. Validation of predictions with the experimental data given by Sandia National Laboratory of the USA indicates that the proposed model yields better results than other models, and the deviation is under 5%. And in some complete reaction zones, the simulation results are even the same as the experimental data. Realizable κ-ε model, Reynold stress model and standard κ-ε model were also investigated to predict the turbulent combustion reaction, which shows that the simulation results of velocities, temperatures, and concentrations of combustion productions by standard κ-ε model are in accordance with the experimental data.