Multi-scale simulation of diffusion behavior of deterrent in propellant

Concentration distribution of the deterrent in single-base propellant during the process of firing plays an important role in the ballistic properties of gun propellant in weapons. However, the diffusion coefficient calculated by molecular dynamics(MD) simulation is 6 orders of magnitude larger than the experimental values. Meanwhile, few simple and comprehensive theoretical models can explain the phenomenon and accurately predict the concentration distribution of the propellant. Herein, an onion model combining with MD simulation and finite element method of diffusion in propellants is introduced to bridge the gap between the experiments and simulations, and correctly predict the concentration distribution of deterrent. Furthermore, a new time scale is found to characterize the diffusion process. Finally, the time-and position-depended concentration distributions of dibutyl phthalate in nitrocellulose are measured by Raman spectroscopy to verify the correctness of the onion model. This work not only provides guidance for the design of the deterrent, but could be also extended to the diffusion of small molecules in polymer with different crystallinity.

与时俱进,不断开创物理化学课程建设新局面

物理化学课程作为化学类、材料类、药学类、化工类、生物类本科专业必需的基础理论课,对于培养符合社会经济发展需求的人才起到不容置疑的重要作用。多年来,华东理工大学物理化学教学团队坚持以“队伍建设为基,资源建设为根,模式创新为魂,能力培养为本”,持之以恒开展了物理化学课程改革与创新。本文将从一流团队建设、一流资源建设、教学内涵创新、教学模式探索等方面,总结我们在争创一流课程中的思考和体会,提炼可供一线教学同行借鉴的经验。

Densities and viscosities for ionic liquids [BMIM][BF4] and [BMIM][Cl] and their binary mixtures at various temperatures and atmospheric pressure

The density and viscosity of 1-butyl-3-methylimidazolium tetrafluoroborate[BMIM][BF4]and 1-butyl-3-methylimidazolium chloride[BMIM][Cl]and their binary mixtures within the temperatures from 303.15 K to323.15 K and at ambient pressure were determined in this work.The temperature dependences of density and viscosity were satisfactorily described with the linear model and the Vogel-Tammann-Fulcher type equation,respectively.The molar volume and viscosity of binary IL mixtures were predicted through ideal mixing rules showing that almost null deviations for IL mixtures were observed and their mixing was remarkably close to linear ideal behavior in the molar volumes,while comparatively large errors in viscosity occurred.Additionally,the molar volume of the investigated pure ILs and their mixtures could well be predicted by a predictive model presented by Valderrama et al.(Fluid Phase Equilib.,275(2009)145).

Multiscale modeling of electrolytes in porous electrode:From equilibrium structure to non-equilibrium transport

Understanding the mechanisms and properties of various transport processes in the electrolyte,porous electrode,and at the interface between electrode and electrolyte plays a crucial role in guiding the improvement of electrolytes,materials and microstructures of electrode.Nanoscale equilibrium properties and nonequilibrium ion transport are substantially different to that in the bulk,which are difficult to observe from experiments directly.In this paper,we introduce equilibrium and no-equilibrium thermodynamics for electrolyte in porous electrodes or electrolyte-electrode interface.The equilibrium properties of electrical double layer(EDL)including the EDL structure and capacitance are discussed.In addition,classical non-equilibrium thermodynamic theory is introduced to help us understand the coupling effect of different transport processes.We also review the recent studies of nonequilibrium ion transport in porous electrode by molecular and continuum methods,among these methods,dynamic density functional theory(DDFT)shows tremendous potential as its high efficiency and high accuracy.Moreover,some opportunities for future development and application of the non-equilibrium thermodynamics in electrochemical system are prospected.

Bubble size fractal dimension,gas holdup,and mass transfer in a bubble column with dual internals

As the scale of residual oil treatment increases and cleaner production improves in China,slurry bubble column reactors face many challenges and opportunities for residual oil hydrogenation technology.The internals development is critical to adapt the long-term stable operation.In this paper,the volumetric mass transfer coefficient,gas holdup and bubble size in a gas-liquid up-flow column are studied with two kinds of internals.The gas holdup and volumetric mass transfer coefficient increase by 120% and 42% when the fractal dimension of bubbles increases from 0.56 to 2.56,respectively.The enhanced mass transfer processing may improve the coke suppression ability in the slurry reactor for residual oil treatment.The results can be useful for the exploration of reacting conditions,scale-up strategies,and oil adaptability.This work is valuable for the design of reactor systems and technological processes.

Photocatalytic degradation of tetracycline hydrochloride with visible light-responsive bismuth tungstate/conjugated microporous polymer

Conjugated microporous polymer(CMP)is an emerging organic semiconductor withπ-conjugated skeletons,and the bandgap of CMP can be flexibly modulated to harvest visible light.Based on the diversity and adjustability of monomers in CMP,we designed and synthesized donor-accepter(D-A)type BTNCMP through Sonogashira-Hagihara cross-coupling polymerization,further in-situ constructing series of inorganic/organic Z-scheme BW/BTN-n composite in the presence of Bi_(2)WO_(6).After optimization,the tetracycline hydrochloride(C0=10 mg·L^(-1))degradation efficiency reached 84%with BW/BTN-2 as catalyst in 90 min under visible light irradiation,the apparent rate constant k1 is 0.017 min^(-1),which is 1.7 and 5.7 times higher than bare Bi_(2)WO_(6) and BTN-CMP.X-ray photoelectron spectra and UV-Vis diffuse spectra showed that the enhanced photocatalytic activity originated from the tight heterojunction between Bi_(2)WO_(6) and BTN-CMP,which can extend the light absorption range and facilitate the separation and transport of photogenerated charges in the interface of heterojunction.The active species trapping experiments and electron spin resonance technique revealed that h+was the dominant active species during the photodegradation process of tetracycline hydrochloride(TCH).The present study demonstrated the feasibility to construct inorganic/organic composite for the photocatalytic degradation of environmental pollutants.

A reaction density functional theory study of solvent effect in the nucleophilic addition reactions in aqueous solution

Whereas the proper choice of reaction solvent constitutes the cornerstone of the green solvent concept,solvent effects on chemical reactions are not mechanistically well understood due to the lack of feasible molecular models.Herein,by taking the case study of nucleophilic addition reaction in aqueous solution,we extend the proposed multiscale reaction density functional theory(RxDFT)method to investigate the intrinsic free energy profile and total free energy profile,and study the solvent effect on the activation and reaction free energy for the nucleophilic addition reactions of hydroxide anion with methanal and carbon dioxide in aqueous solution.The predictions of the free energy profile in aqueous solution for these two nucleophilic addition reactions from RxDFT have a satisfactory agreement with the results from the RISM and MD-FEP simulation.Meanwhile,the solvent effect is successfully addressed by examining the difference of the free energy profile between the gas phase and aqueous phase.In addition,we investigate the solvent effect on the reactions occurred near solid-liquid interfaces.It is shown that the activation free energy is significantly depressed when reaction takes place in the region within 10A distance to the substrate surface owing to the decrease of hydration free energy at the solid-liquid interface.

Curvature effects on electric-double-layer capacitance

Understanding the microscopic structure and thermodynamic properties of electrode/electrolyte interfaces is central to the rational design of electric-double-layer capacitors(EDLCs).Whereas practical applications often entail electrodes with complicated pore structures,theoretical studies are mostly restricted to EDLCs of simple geometry such as planar or slit pores ignoring the curvature effects of the electrode surface.Significant gaps exist regarding the EDLC performance and the interfacial structure.Herein the classical density functional theory(CDFT)is used to study the capacitance and interfacial behavior of spherical electric double layers within a coarse-grained model.The capacitive performance is associated with electrode curvature,surface potential,and electrolyte concentration and can be correlated with a regression-tree(RT)model.The combination of CDFT with machine-learning methods provides a promising quantitative framework useful for the computational screening of porous electrodes and novel electrolytes.

Understanding electrokinetic thermodynamics in nanochannels

Understanding the electrokinetic conversion efficiency in a nanochannel is vital for designing energy storage and conversion devices.In this paper,an analytical electrokinetic energy conversion efficiency in a nanochannel is obtained based on the linear electrokinetic response.The analytical result shows that the conversion efficiency has a maximum with the increasing of the nanochannel pore radius.Numerical solutions based on the Poisson-Nernst-Planck(PNP)and Navier-Stokes(NS)equations are used to confirm the analytical expressions.Besides,the influences of the pore radius and surface roughness on the conversion efficiency in nanochannels are also studied by the numerical calculations.In particular,the influences of the surface roughness on the fluid flow,streaming current and streaming potential are examined.The results show that the large bumps and grooves representing the roughness can hinder the fluid flows and ion transports in the nanochannels.The maximum efficiency in a smooth nanochannel is higher than that in a rough channel.However,the small bumps and grooves can increase the surface area of the channel,which is beneficial to improving the conversion efficiency in some cases.This research can provide theoretical guidance to design electrokinetic energy conversion devices.

Ionic Liquid-Polypyrrole-Gold Composites as Enhanced Enzyme Immobilization Platforms forHydrogen Peroxide Sensing

In this work, three different aqueous solutions containing imidazole-based ILs w让h different alkyl chain lengths ([Cnmim]Br, n = 2Z 6,12) were adopted as the medium for the synthesis of ionic liquid-polypyrrole (IL-PPy) composites. Herein, the ILs undertook the roles of the pyrrole solvent, the media for emulsion polymerization of PPy and PPy dopants, respectively. The electrochemical performances of the three IL-PPy composites on a glassy carbon electrode (GCE) were investigated by electrochemical experiments, which indicated that [Ci2mim]Br-PPy (Ci2~PPy) composites displayed better electrochemical performance due to their larger surface area and firmer immobilization on the GCE. Further, Ci2?PPy/GCE were decorated with Au microparticles by electrodeposition that can not only increase the conductivity, but also immobilize sufficient biomolecules on the electrode. Then, the obtained Ci2~PPy^Au/GCE with outstanding electrochemical performance was employed as a horseradish peroxidase (HRP) immobilization platform to fabricate a novel Ci2-PPy-Au-HRP/GCE biosensor for H2O2 detection. The results showed that the prepared Ci2-PPy-Au-HRP/GCE biosensor exhibited high sensitivity, fast response, and a wide detection range as well as low detection limit towards H2O2. This work not only provides an outstanding biomolecule immobilization matrix for the fabrication of highly sensitive biosensors, but also advances the understanding of the roles of ILs in improving the electrochemical performance of biosensors.

Operando generated copper‐based catalyst enabling efficient electrosynthesis of 2,5‐bis(hydroxymethyl)furan

Electrocatalytic upgrading of biomass-derived platform molecules has emerged as a sustainable and environmentally benign route to produce high-value chemicals.The main challenge lies in developing efficient catalysts for the selective activation of designated chemical bonds in the presence of various reducible groups.This work demonstrated a high-efficiency electrochemical conversion of 5-hydroxymethylfurfural(HMF)to 2,5-bis(hydroxymethyl)furan(BHMF),an important industrial synthetic reagent.A highly porous Cu-based catalyst was developed that achieved nearly 100%BHMF selectivity and long-term stability.Through comprehensive operando and ex-situ structural characterizations,an electrochemically generated catalyst with abundant Cu/Cu2O interfaces was identified as a catalytically active phase for HMF conversion.Deuterated BHMF,with the potential to produce deuterated drugs,was also synthesized using D2O as the deuterium source.Density functional theory calculations show that the Cu/Cu2O interface structure exhibits relatively low energy barriers for the hydrogenation of HMF to BHMF.This work provides insights into the origin of electrocatalytic hydrogenation activity and highlights the promising potential of the electrocatalytic synthesis of high-value chemicals.

FeOCl层状材料及其插层化合物:结构、性质与应用

氧基氯化铁(FeOCl)是一种典型的Fe基层状材料,于20世纪30年代被发现,并于20世纪70年代起作为一种优异的插层主体在超分子插层化学领域进行了大量的研究。FeOCl的层状结构赋予了其远比传统铁(氢)氧化物更加灵活的调变空间,自2013年第一次发现FeOCl具有优异的固体Fenton活性以来,围绕FeOCl及其插层化合物在催化、能源等领域涌现了大量的应用性研究,展现了其巨大的发展潜力。本文首先对FeOCl及其几种典型的插层体系进行了介绍,重点对插层诱导的FeOCl晶体和电子结构变化进行了讨论,然后对FeOCl及其插层化合物在水中污染物高级氧化降解、电极材料以及其他新兴领域的应用研究进展进行了综述。最后,从FeOCl的结构设计和稳定性等方面对其未来的开发应用趋势进行了展望。

CO_(2) capture and in-situ conversion: recent progresses and perspectives

Global warming caused by excess carbon dioxide(CO_(2))emission has been a focus of the world.The development of neutral carbon technologies becomes a strategic choice for the sustainable human society.Integrating CO_(2) capture and conversion(iCCC)technology can simultaneously convert the captured CO_(2) from flue gas into value-added chemicals,which saves great energies and expenses incurred in CO_(2) compression and transportation processes of conventional carbon capture,utilization,and storage(CCUS)technology.The present review criti-cally discusses the dual-function materials(DFMs)and the iCCC technology at intermediate temperature for methane production and high temperature for syngas production.The design of reactor and optimization of operation conditions are emphasized from the perspective of industrial applications.The dual-fixed-bed reactors mode by switching the flue gas and reactant gases,and the dual-fluidized-bed reactors mode by the circulation of DFMs particles are comparatively reviewed.We hope this review can stimulate further studies including designing and fabricating feasible DFMs,exploring realistic catalytic process for CO_(2) conversion to high value-added chemicals,developing workable reactor modes and optimizing operation conditions,and establishing industrial demonstration for real applications of iCCC technology in the future.

Improved oxidation of hydrogen off-gas by hydrophobic surface modification: A multiscale density functional theory study

A catalytic micro-reactor for converting hydrogen off-gas into water was recently developed, through which the conversion efficiency of hydrogen gas was greatly improved by hydrophobic modification of the catalytic substrate. Herein, a hybrid theoretical method is reported that combines density functional theory (DFT) on both the quantum and molecular scales. This method allows the microscopic study of the mechanism by which the surface catalytic reaction can be manipulated. Specifically, quantum DFT calculations are performed to quantify the molecular interaction between the catalytic substrate and reagent or product. Classical DFT investigations are subsequently carried out to determine the local concentrations of reagents near catalytic sites subject to different surface coating conditions. Finally, the reaction efficiency is determined from the local concentrations based on collision theory. This multiscale method provides molecular insight for quantifying the effect of catalytic surface modification on the reaction efficiency. The method reveals that an optimal surface hydrophobic modification can promote the densities of reagents near the substrate, while depleting the produced water. These two factors promote the conversion efficiency. The exclusion of produced water from the catalytic substrate is affected more by the degree of polymer grafting than by the chain length of hydrophobic polymer moieties.

Atomistic simulations for adsorption and separation of flue gas in MFI zeolite and MFI/MCM-41 micro/mesoporous composite

Adsorption of pure CO_(2) and N2 and separation of CO_(2)/N2 mixture in MFI zeolite and MFI/MCM-41 micro/mesoporous composite have been studied by using atomistic simulations.Fully atomistic models of MFI and MFI/MCM-41 are constructed and characterized.A bimodal pore size distribution is observed in MFI/MCM-41 from simulated small-and broad-angle X-ray diffrac-tion patterns.The density of MFI/MCM-41 is lower than MFI,while its free volume and specific surface area are greater than MFI due to the presence of mesopores.CO_(2) is preferentially adsorbed than N2,and thus,the loading and isosteric heat of CO_(2) are greater than N2 in both MFI and MFI/MCM-41.CO_(2) isotherm in MFI/MCM-41 is similar to that in MFI at low pressures,but resembles that in MCM-41 at high pressures.N2 shows similar amount of loading in MFI,MCM-41 and MFI/MCM-41.The selectivity of CO_(2) over N2 in the three adsorbents decreases in the order of MFI>MFI/MCM-41>MCM-41.With increasing pressure,the selectivity increases in MFI and MFI/MCM-41,but decreases in MCM-41.The self-diffusivity of CO_(2) and N2 in MFI decreases as loading increases,while in MFI/MCM-41,itfirst increases and then drops.

Synergetic effect of polydopamine particles and in-situ fabricated gold nanoparticles on charge-dependent catalytic behaviors

The versatile catechol unit of polydopamine (PDA) endows this molecule with a broad ranging adhesive properties and reducibility.We prepared free-standing PDA particles by a simple self-polymerization and these particles served as both an effective reductant and scaffold for a hybrid catalyst.The raspberrylike nanocomposites featured a high density of AuNPs uniformly deposited on PDA particles (PDA@Au).This system was prepared in-situ with assistance from the active catechol and amine groups of the PDA particles.To quantify the effect of the PDA carriers,we studied the catalytic activity of the PDA and PDA@Au particles.The PDA particles showed a pronounced charge-dependent catalytic activity for reduction of cationic methylene blue,negatively-charged 4-nitrophenolate,and zwitterionic rhodamine B in the presence of borohydride,whereas PDA@AuNPs showed catalytic activity with a less pronounced charge-dependence of the catalytic efficiency of the AuNPs.The PDA particles served as a redox mediator and adsorbent accelerator in degradation of the dyes owing to its unique chemical structure.

Synthesis, characterization and fluorescence quenching of conjugated polymer containing triphenylamine group

Poly(triphenylamine-p-phenylenevinylene)s with two different end-groups were obtained through a Wittig polycondensation.The structures of two copoly-mers were characterized.Ultraviolet and visible spectro-scopy(UV-Vis)and photoluminescence(PL)spectra show the end-capped polymer emits intensive green light in both solution and film state.Their applications in the detection of nitro compounds were investigated,and the results show high fluorescence quenching sensitivity of the end-capped polymer towards o-nitrotoluene(o-NT).When the concentration of o-NT was 21.5×10^(-3) mol/L,the fluorescence quenching reached 96%.Additionally,after the exposure of polymer film in three different quenchers such as dinitrotoluene(DNT),p-nitrobenzo-quinone(p-BQ)and p-nitrotoluene(p-NT)for 600 s,its fluorescence quenching reached 93.6%,11.5%and 77.9%,respectively.This kind of polymer has great advantages in preparation and may find applications in the detection of nitro explosives.

Mechanical behavior and wrinkling patterns of phaseseparated binary polymer blend film

The wrinkling of phase-separated binary polymer blend film was studied through combining the Monte Carlo(MC)simulation for morphologies with the lattice spring model(LSM)for mechanical properties.The information of morphology and structure obtained by use of MC simulation is input to the LSM composed of a three-dimensional network of springs,which allows us to determine the wrinkling and the mechanical properties of polymer blend film,such as strain,stress,and Young’s modulus.The simulated results show that the wrinkling of phase-separated binary polymer blend film is related not only to the structure of morphology,but also to the disparity in elastic moduli between polymers of blend.Our simulation results provide fundamental insight into the relationship between morphology,wrinkling,and mechanical properties for phase-separated polymer blend films and can yield guidelines for formulating blends with the desired mechanical behavior.The wrinkling results also reveal that the stretching of the phase-separated film can form the micro-template,which has a wide application prospect.

Multivalence-Ion Intercalation Enables Ultrahigh 1T Phase MoS_(2)Nanoflowers to Enhanced Sodium-Storage Performance

Developing rapid charging and robust electrode materials for Na-ion batteries is of considerable significance in large-scale power electricity fields.Herein,the authors have proposed a multivalenceion intercalation strategy to construct threedimensional(3D)Co-MoS2 nanoflowers with tailorable 1T/2H phase and interlayer distance.The as-formed S-Co-S covalent bonds serve as“electric bridges”to accelerate interlayer charge transfer without 1T phase degeneration during sodiation and desodiation.Quantum density functional theory(QDFT)calculations further confirm that the optimal Co-MoS2 nanoflowers possess the highest Na adsorption energy with reduced ionic diffusion barrier.Consequently,they deliver a superior sodiumstorage capacity of 351 mAh g−1 in 0.4-3.0 V even at 20 A g−1 without capacity fading at 5 A g−1 for 2000 cycles.The high electrochemical reversibility of the 1T phase in Co-MoS2,which accounts for such excellent performance,has been unveiled for the first time by in situ Raman spectra.This finding demonstrates important insights onto promoting two-dimensional(2D)nanomaterials toward rapid charging alkali-ion batteries.