The chemical environment and structural ordering in liquid Mg-Y-Zn system:An ab-initio molecular dynamics investigation of melt for the formation mechanism of LPSO structure

In an effort to clarify the formation mechanism of LPSO structure in Mg-Y-Zn alloy,the chemical environment and structural ordering in liquid Mg-rich Mg-Y-Zn system are investigated with the aid of ab-initio molecular dynamics simulation.In liquid Mg-rich Mg-Y alloys,the strong Mg-Y interaction is determined,which promotes the formation of fivefold symmetric local structure.For Mg-Zn alloys,the weak Mg-Zn interaction results in the fivefold symmetry weakening in the liquid structure.Due to the coexistence of Y and Zn,the strong attractive interaction is introduced in liquid Mg-Y-Zn ternary alloy,and contributes to the clustering of Mg,Y,Zn launched from Zn.What is more,the distribution of local structures becomes closer to that in pure Mg compared with that in binary Mg-Y and Mg-Zn alloys.These results should relate to the origins of the Y/Zn segregation zone and close-packed stacking mode in LPSO structure,which provides a new insight into the formation mechanism of LPSO structure at atomic level.

Atomic Level Dispersed Metal–Nitrogen–Carbon Catalyst toward Oxygen Reduction Reaction: Synthesis Strategies and Chemical Environmental Regulation

For development and application of proton exchange membrane fuel cell(PEMFC) energy transformation technology, the cost performance must be elevated for the catalyst. At present, compared with noble metal-based catalysts, such as Pt-based catalysts, atomically dispersed metal–nitrogen–carbon(M–N–C) catalysts are popularity and show great potential in maximizing active site density, high atom utilization and high activity,making them the first choice to replace Pt-based catalysts. In the preparation of atomically dispersed metal–nitrogen–carbon catalyst, it is difficult to ensure that all active sites are uniformly dispersed, and the structure system of the active sites is not optimal. Based on this, we focus on various approaches for preparing M–N–C catalysts that are conducive to atomic dispersion, and the influence of the chemical environmental regulation of atoms on the catalytic sites in different catalysts. Therefore, we discuss the chemical environmental regulation of the catalytic sites by bimetals, atom clusters, and heteroatoms(B, S, and P). The active sites of M–N–C catalysts are explored in depth from the synthesis and characterization, reaction mechanisms, and density functional theory(DFT)calculations. Finally, the existing problems and development prospects of the current atomic dispersion M–N–C catalyst are proposed in detail.

SPECTRAL VARIATION AND CHARACTERISTICS OF LOW VALENCY RARE EARTH IONS IN COMPLEX OXIDESⅢ.EFFECT OF THE CRYSTAL ENVIRONMENT AND CHEMICAL FACTORS ON LUMINESCENCE PROPERTIES OF EUROPIUM (Ⅱ) ION

In this paper,the influence of crystal-field on the Luminescence properties of Eu^(2+) in complex oxides are studied theoretically by using purely electrostatic model,the dependence of the 4f^65d levels on Eu-O bond distance is given.Quantum chemistry calculation shows that the splitting extent of 4f^65d energy band in cubic or in octahedral fields will be inversely proportional to R^5,where R is the distance of Eu^(2+) to oxygen ligand.The value of R affects slightly the location of the centre of 4f^65d energy band.According to the exper- imental spectrum data,we have discussed the influence of the host chemical composition,the replaced sites of Eu^(2+) and degree of covalency of Eu-O bond on luminescence properties of Eu^(2+).Some regularity of fluorescence spectrum was observed. In alkali-alkaline earth-phosphates,the splitting extent of 4f^65d band (△E) becomes smaller as the Eu-O bond distance (R) increases.In Na_(3-x)(PO_4)_(1-x)(SO_4)_x and Na_(2-x)CaSi_(1-x)P_xO_4 hosts,d-d emission peak of Eu^(2+) will shift to shorter wavelength with the increase of x's value. The crystal structure data show that Eu^(2+) in K_2Mg_2(SO_4)_3 is affected more strongly by crystal-field and covalancy than in KMgF_3,so K_2Mg_2(SO_4)_3:Eu^(2+) emits blue light (E_(em)~m=400nm) and KMgF_3:Eu^(2+) produces ultraviolet fluorescence.

Regulating local chemistry in ZrCo-based orthorhombic hydrides via increasing atomic interference for ultra-stable hydrogen isotopes storage

Developing a universal and reliable strategy for the modulation of composition and structure of energy storage materials with stable cycling performance is vital for hydrogen and its isotopes storage advanced system,yet still challenging.Herein,an ultra-stable lattice structure is designed and verified to increase atomic chaos and interference for effectively inhibiting disproportionation reaction and improving cycling stability in ZrCo-based hydrogen isotopes storage alloy.After screening in terms of configuration entropy calculation,we construct Zr_(1-2)Nb_(x)Co_(1-2x)Cu_(x)Ni_(x)(x=0.15,0.2,0.25) alloys with increased atomic chaos,and successfully achieve stable isostructural de-/hydrogenation during 100 cycles,whose cycling capacity retentions are above 99%,much higher than 22.4%of pristine ZrCo alloy.Both theoretical analysis and experimental evidences indicate the high thermo-stability of orthorhombic lattice in Zr_(0.8)Nb_(0.2)Co_(0.6)Cu_(0.2)Ni_(0.2) alloy.Notably,the increased atomic chaos and interference in Zr_(0.8)Nb_(0.2)Co_(0.6)Cu_(0.2)Ni_(0.2) alloy causes regulation in hydrogen local chemical neighborhood,thereby confusing the hydrogen release order,which effectively eliminates lattice distortion and unlocks an ultrastable lattice structure.This study provides a new and comprehensive inspiration for hydrogen atoms transport behaviors and intrinsic reason of stable orthorhombic transformation,which can contribute to paving the way for other energy storage materials modulation.

Electrochemical CO_(2) reduction catalyzed by organic/inorganic hybrids

Electroreduction of CO_(2) into value-added chemicals and fuels utilizing renewable electricity offers a sustainable way to meet the carbon-neutral goal and a viable solution for the storage of intermittent green energy sources.At the core of this technology is the development of electrocatalysts to accelerate the redox kinetics of CO_(2) reduction reactions(CO_(2)RR)toward high targeted-product yield at minimal energy input.This perspective focuses on a unique category of CO_(2)RR electrocatalysts embodying both inorganic and organic components to synergistically promote the reaction activity,selectivity and stability.First,we summarize recent progress on the design and fabrication of organic/inorganic hybrids CO_(2)RR electrocatalysts,with special attention to the assembly protocols and structural configurations.We then carry out a comprehensive discussion on the mechanistic understanding of CO_(2)RR processes tackled jointly by the inorganic and organic phases,with respect to the regulation of mass and charge transport,modification of double-layer configuration,tailoring of intermediates adsorption,and establishment of tandem pathways.At the end,we outline future challenges in the rational design of organic/inorganic hybrids for CO_(2)RR and further extend the scope to the device level.We hope this work could incentivize more research interests to construct organic/inorganic hybrids for mobilizing electrocatalytic CO_(2)RR towards industrialization.

Assessing cypermethrin-contaminated soil with three different earthworm test methods

A series of tests (lethal,sublethal,and behavioral) on earthworms were conducted as an eco-assessment of pesticides.In this study,the toxicity of cypermethrin-contaminating soil on adult and juvenile earthworms was assessed.Beside the acute and chronic tests,an avoidance response test was carried out.It was shown that the all-round toxicity from cypermethrin was weak on adult earthworms.Compared with adult earthworms,the toxicity of juvenile earthworms from cypermethrin especially chronic toxicity increased...

Preparation of Monodispersed Copper Nanoparticles by an Environmentally Friendly Chemical Reduction

In this paper, highly dispersive nanosized copper particles with a mean particle size of less than 6 nm are prepared by an environmentally friendly chemical reduction method. Non-toxic L-ascorbic acid acts as both reducing agent and antioxidant in ethylene glycol in the absence of any other capping agent. Transmission electron microscopy （TEM） is used to characterize the size and morphology of Cu nanoparticles. The results of UV-Vis spectroscopy （UV-Vis）, energy dispersive spectroscopy （EDS） and high resolution TEM （HRTEM） illustrate that the resultant product is pure Cu nanocrystals. The size of Cu nanoparticles is remarkably impacted by the order of reagent addition, and the investigation reveals the reaction procedure of Cu^2＋ ions and L-ascorbic acid.

2013 5th International Conference on Chemical,Biological and Environmental Engineering-ICBEE 2013

The ICBEE 2013 is sponsored by Asia-Pacific Chemical, Biological ＆ Environmental Engineering Society. The primary goal of the conference is to promote research and developmental activities in Chemical, Biological and Environmental Engineering. Another goal is to promote scientific information interchange between researchers, developers, engineers, students, and practitioners working in India and abroad. All ICBEE 2013 papers will be published in the APCBEE Procedia （Journal under Elsevier, ISSN： 2212-6708）, and will be included in ScienceDirect. One Excellent Paper will be selected from each oral session. The Certificate for Excellent Papers will be awarded in the Welcome Banquet on September 15, 2013.

具有丰富孤对电子的亲锌超分子分子通道实现高度稳定锌阳极

在柔性设备和静态储能电网应用中,可充电水性锌离子电池展现出巨大的潜力.但其发展受到界面不稳定性引起的副反应及枝晶生长的阻碍.本研究中,我们采用了一种新颖的电解液设计,通过含大量孤电子对的亲锌葫芦[7]超分子来应对这一挑战.这些超分子因其独特的分子结构,能够在电化学循环中有效地吸纳和固定Zn离子,从而有效避免了Zn离子的无序迁移和枝晶的形成.超分子中丰富的孤对电子提供的Lewis碱性位点(如叔胺和羰基氧)作为Zn离子的供电子成核位点,促进了紧密成核.这些超分子与Zn离子之间的强烈相互作用,不仅提高了系统的稳定性,还显著抑制了不良副反应.因此,我们组装的对称电池和Zn//V_(2)O_(5)全电池均展示了长效的循环稳定性和卓越的库仑效率.

Regulating Electronic Status of Platinum Nanoparticles by Metal-Organic Frameworks for Selective Catalysis

Selective hydrogenation of alkynes to alkenes remains challenging in the field of catalysis due to the ease of over-hydrogenated of alkynes to alkanes.Favorably,the incorporation of metal nanoparticles(MNPs)into metal-organic frameworks(MOFs)provides an opportunity to adjust the surface electronic properties of MNPs for selective hydrogenation of alkynes.Herein,we used differentmetal-O clusters of MOFs to regulate the electronic status of platinum nanoparticles(Pt NPs)toward overhydrogenation,semihydrogenation,and unhydrogenation of phenylacetylene.Specifically,Pt/Fe-O cluster-based MOFs are found to reduce the electronic density on Pt NPs and inhibit the overhydrogenation of styrene,leading to an 80%increase in selectivity toward a semihydrogenation product(styrene).Meanwhile,Cu-O cluster-based MOFs generate high oxidation states of Pt NPs and release Cu^(2+)ions,which worked together to deactivate Pt NPs in the hydrogenation reaction entirely.Thus,our studies illustrate the critical role of metal-O clusters in governing chemical environments within MOFs for the precise control of selective hydrogenation of alkynes,thereby,offering appealing opportunities for designing MNPs/MOFs catalysts to prompt a variety of reactions.