Revealing the Effect of Surface Composition on Multiwalled Carbon Nanotubes Supported Pt-Fe Alloy Electrocatalysts for Methanol Oxidation Performance

The designs of efficient and inexpensive Pt-based catalysts for methanol oxidation reaction (MOR) are essential to boost the commercialization of direct methanol fuel cells. Here, the highly catalytic performance PtFe alloys supported on multiwalled carbon nanotubes (MWCNTs) decorating nitrogen-doped carbon (NC) have been successfully prepared via co-engineering of the surface composition and electronic structure. The Pt₁Fe₃@NC/MWCNTs catalyst with moderate Fe³⁺ feeding content (0.86 mA/mg_Pt) exhibits 2.26-fold enhancement in MOR mass activity compared to pristine Pt/C catalyst (0.38 mA/mg_Pt). Furthermore, the CO oxidation initial potential of Pt₁Fe₃@NC/MWCNTs catalyst is lower relative to Pt/C catalyst (0.71 V and 0.80 V). Benefited from the optimal surface compositions, the anti-corrosion ability of MWCNT, strong electron interaction between PtFe alloys and MWCNTs and the N-doped carbon (NC) layer, the Pt₁Fe₃@NC/MWCNTs catalyst presents an improved MOR performance and anti-CO poisoning ability. This study would open up new perspective for designing efficient electrocatalysts for the DMFCs field.     

Identification of metabolites of Ginkgolide B in vivo and in vitro using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry

Ginkgolide B is a dietary diterpene with multiple pharmacological activities. However, current research on ginkgolide B is not comprehensive. The current study analyzed the metabolic profile of ginkgolide B in vivo and in vitro using ultra-high-performance liquid chromatography quadrupole time-of-flight mass spectrometry. To detect and identify the different metabolites in ginkgolide B, a novel data processing method was used as an assistant tool. A total of 53 different metabolites of ginkgolide B (38 phase I metabolites and 15 phase II metabolites) were detected relative to blank samples. The biotransformation route of ginkgolide B was identified as oxidation, dehydroxylation, hydrogenation, decarbonylation, demethylation, sulfate conjugation, glucose conjugation, methylation, and acetylation. The current study demonstrated a method for rapidly detecting and identifying metabolites and provided useful information to further characterize the pharmacology and mechanism of ginkgolide B. A method for the analysis of other diterpene metabolic components in vivo and in vitro was also established.     

嵌段共聚物薄膜快速自组装方法

嵌段共聚物 (BCP) 薄膜可通过不同的退火方法诱导其微相分离,从而获得大面积圆柱状、层状和球状等纳米图案。这些长程有序的纳米结构形态,已经广泛应用在纳米光刻和电子器件等多个领域中。目前,有效且快速的退火方法仍然是BCP薄膜自组装技术中的研究热点。本文首先介绍了制备BCP薄膜纳米结构图案常用的退火技术,然后综述了三种新型快速退火技术,最后分析总结了这些退火技术的优缺点。     

Significant Enhancement of the Capacity and Cycling Stability of Lithium-Rich Manganese-Based Layered Cathode Materials via Molybdenum Surface Modification

Lithium-rich manganese-based layered cathode materials are considered to be one of the best options for next-generation lithium-ion batteries, owing to their ultra-high specific capacity (>250 mAh·g⁻¹) and platform voltage. However, their poor cycling stability, caused by the release of lattice oxygen as well as the electrode/electrolyte side reactions accompanying complex phase transformation, makes it difficult to use this material in practical applications. In this work, we suggest a molybdenum surface modification strategy to improve the electrochemical performance of Li_1.2Mn_0.54Ni_0.13Co_0.13O₂. The Mo-modified Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ material exhibits an enhanced discharge specific capacity of up to 290.5 mAh·g⁻¹ (20 mA·g⁻¹) and a capacity retention rate of 82% (300 cycles at 200 mA·g⁻¹), compared with 261.2 mAh·g⁻¹ and a 70% retention rate for the material without Mo modification. The significantly enhanced performance of the modified material can be ascribed to the formation of a Mo-compound-involved nanolayer on the surface of the materials, which effectively lessens the electrolyte corrosion of the cathode, as well as the activation of Mo⁶⁺ towards Ni²⁺/Ni⁴⁺ redox couples and the pre-activation of a Mo compound. This study offers a facile and effective strategy to address the poor cyclability of lithium-rich manganese-based layered cathode materials.     

铁催化剂上化学吸附N2的络合活化与加氢成氨

关于Fe上N₂的络合活化,业已提出若干原子簇模型。基于所得到的现场动态互补红外与拉曼光谱的实验结果,进行了EHMO计算,以便从理论上比较化学吸附N₂的各种络合活化模式,并探测其加氢成氨的可能方式。取α-Fe(111)面Fe₇原子簇及其络合活化的N₂为计算模型体系。模型-A为双端基加多侧基桥式对称平躺式,模型-B₁和B₂分别为单端基或准双端基加多侧基斜交式,模型-C为单端基加多侧基直插式。     

用铝灰生产聚氯化铝的反应动力学研究

本文对以工业废渣铝灰与盐酸反应制取聚氯化铝的反应进行了动力学研究。在0.5～3N的盐酸浓度范围内,反应速度与盐酸浓度的1.5次方成正比,反应的表观活化能为48kJ/mol-H₂。以某厂提供的铝灰为试样,测得动力学方程式为 dH₂/dt=6.2×10²·exp(-5.8×10³/T)·W·C_Hcl^1.5(mol/s)。     

Mechanism of water oxidation catalyzed by vitamin B12: Redox non-innocent nature of corrin ligand and crucial role of phosphate

Vitamin B₁₂（macrocyclic cobalamin） has been recently reported to be capable of electrochemically catalyzing water oxidation in a neutral phosphate buffer solution. In this work, density functional calculations were employed to elucidate the water oxidation mechanism catalyzed by vitamin B₁₂. The calculations showed that the catalytic cycle starts from the L·-Co^Ⅱ-OH₂ complex 1. A proton-coupled electron transfer process then leads to the formation of a ...     

A flame retardant separator modified by MOFs-derived hybrid for safe and efficient Li-S batteries

In this work,we have successfully prepared a novel separator modified with N,S co-doped carbon framework(named NSPCF)with confined CoS₂ nanoparticles and rooted carbon nanotubes material(named NSPCF@CoS₂)to apply for high-performance Lithium-Sulfur batteries(Li-S batteries).Robust carbon structure with large specific surface can act as a physical barrier and possess physical adsorption effect on lithium polysulfides(LiPSs).In addition,highly-conductive carbon can improve integral conductivity,leading to the fast charge transport and reaction kinetics.Also,doping heteroatoms could form more active sites to adsorb LiPSs strongly so that modified separator could inhibit the shuttle effect effectively.Moreover,the presence of CoS₂ further enhances the ability of modified separator to trap LiPSs owing to the Lewis acid-base action.As a result,the NSPCF@CoS₂@C-150 battery can deliver initial discharge capacities of 863.0,776.2,649.1 and 489.4 mAh g^-1 at 0.1,0.5,1 and 2C with a high sulfur loading of 2.04 mg cm^-2,respectively.Notably,when turning the current density back to 0.1 C,its discharge capacity can recover to 1008.7 mAh g^-1.In addition,the modified separators exhibit outstanding capacities to restrain the growth of lithium dendrites.It is noteworthy that the flame retardant performances of Li-S batteries are improved dramatically owing to the novel structures of modified separators.This rationally designed separator endows Li-S batteries with higher safety and excellent electrochemical performances,providing a feasible strategy for practical application of Li-S batteries.     

Spatiotemporally-regulated multienzymatic polymerization endows hydrogel continuous gradient and spontaneous actuation

There are several natural materials which have evolved functional gradients,ingeniously attaining maximal efficacy from limited components.Herein,we utilized the spatiotemporal distribution of initiator acetylacetone to regulate the multienzyme polymerization and fabricate a chitosan-polymer hydrogel.The temporal priority order of acetylacetone was higher than phenolmodified chitosan by density functional theory calculation.The acetylacetone within the gelatin could gradually diffuse spatially into the chitosan hydrogel to fabricate the composite hydrogel with gradient network structure.The gradient hydrogel possessed a transferring topography from the two-dimensional pattern.A continuously decreased modulus along with acetylacetone diffusion was confirmed by atomic force microscope-based force mapping experiment.The water-retaining ability of various regions was confirmed by low-field nuclear magnetic resonance(NMR)and thermogravimetric analysis(TG)analysis,which led to the spontaneous actuation of gradient hydrogel with maximum 1821°/h curling speed and 227°curling angle.Consequently,the promising gradient hydrogels could be applied as intelligent actuators and flexible robots.     

Synthesis and magnetic properties of trinuclear nickel(II) complexes bridged by α-benzyldioximato groups

Four new NiII–NiII–NiII homotrinuclear complexes namely [Ni(-BD)2{NiL2}](ClO4)2 [L = 1,10-phenanthroline (phen), 5-nitro-1,10-phenanthroline (5-NO2-phen), 2,2-bipyridyl (bpy) or 4,4-dimethyl-2,2bipyridyl (Me2bpy) and (-BD)– = -benzyldioximato ion] have been prepared and characterized. Based on elemental analyses, i.r. spectra, conductivity measurements, extended -benzyldioximato-bridged systems consisting of three nickel(II) ions in which the central nickel(II) ion has a square-planar environment and the end capped two nickel(II) ions have a distorted octahedral environment are proposed for these structures. The temperature dependence of the magnetic susceptibility for complexes (1) (phen), (2) (5-NO2-phen), (3) (bpy) and (4) (Me2bpy) were measured over the 77–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator (H^ = –2JS^1S^2), giving the exchange integral J = –13.31 cm–1 for (1), J = –7.37 cm–1 for (2), J = –8.96 cm–1 for (3) and J = –7.33 cm–1 for (4) These results indicate a weak antiferromagnetic spin exchange interaction between the two terminal nickel(II) io