奇奇核170Ta高自旋态及旋称反转研究

用97MeV的¹⁹F束通过¹⁵⁵Gd(¹⁹F,4n)¹⁷⁰Ta反应布居了奇奇核¹⁷⁰Ta的高自旋态,将¹⁷⁰Ta的3个转动带推向了更高的自旋态,并观测到了半退耦带的旋称反转点,将其自旋值定在了19.5h.首次比较系统地总结了稀土区半退耦带的旋称反转系统规律,并比较了该核区半退耦带与晕带的系统性差异,特别是这两个带在能量劈裂程度上存在着系统性差异.从这一现象出发,探讨了半退耦带与晕带旋称反转系统性差异的成因,指出p-n剩余相互作用在这一现象中起着非常重要的作用.     

Finite‐element/level‐set/operator‐splitting (FELSOS) approach for computing two‐fluid unsteady flows with free moving interfaces

The present work is devoted to the study on unsteady flows of two immiscible viscous fluids separated by free moving interface. Our goal is to elaborate a unified strategy for numerical modelling of two‐fluid interfacial flows, having in mind possible interface topology changes (like merger or break‐up) and realistically wide ranges for physical parameters of the problem. The proposed computational approach essentially relies on three basic components: the finite element method for spatial approximation, the operator‐splitting for temporal discretization and the level‐set method for interface representation. We show that the finite element implementation of the level‐set approach brings some additional benefits as compared to the standard, finite difference level‐set realizations. In particular, the use of finite elements permits to localize the interface precisely, without introducing any artificial parameters like the interface thickness; it also allows to maintain the second‐order accuracy of the interface normal, curvature and mass conservation. The operator‐splitting makes it possible to separate all major difficulties of the problem and enables us to implement the equal‐order interpolation for the velocity and pressure. Diverse numerical examples including simulations of bubble dynamics, bifurcating jet flow and Rayleigh–Taylor instability are presented to validate the computational method. Copyright © 2004 John Wiley & Sons, Ltd.     

Highly Conformal Deposition of an Ultrathin FeOOH Layer on a Hematite Nanostructure for Efficient Solar Water Splitting

An ultrathin (ca. 2 nm) amorphous FeOOH overlayer was deposited conformally on a hematite nanostructure by a simple solution‐based precipitation method, to generate an oxygen evolution cocatalyst for efficient solar water splitting. This uniform and highly conformal coating of the ultrathin metal oxyhydroxide is rare and is distinguished from the layers prepared by other conventional methods. With the FeOOH overlayer as the cocatalyst, the water oxidation photocurrent of hematite increased by a factor of approximately two and the onset potential shifted in the cathodic direction by 0.12 V under 1 sun illumination. The enhanced performance was attributed to the improved water oxidation kinetics and the passivation of the surface states of the hematite.     

Hollow Chevrel‐Phase NiMo3S4 for Hydrogen Evolution in Alkaline Electrolytes

Electrochemical water splitting to generate molecular hydrogen requires catalysts that are cheap, active, and stable, particularly for alkaline electrolyzers, where the cathodic hydrogen evolution reaction is slower in base than in acid even on platinum. Herein, we describe the synthesis of new hollow Chevrel‐phase NiMo₃S₄ and its alkaline hydrogen evolution reaction (HER) performance: onset potential of ?59 mV, Tafel slope of 98 mV per decade, and exchange current density of 3.9×10^?2 mA cm^?2. This Chevrel‐phase chalcogenide also demonstrates outstanding long‐term stability under harsh HER cycling conditions. Chevrel‐phase nanomaterials show promise as efficient, low‐cost catalysts for alkaline electrolyzers.     

Nitrogen,Phosphorus, and Fluorine Tri‐doped Graphene as a Multifunctional Catalyst for Self‐Powered Electrochemical Water Splitting

Electrocatalysts are required for clean energy technologies (for example, water‐splitting and metal‐air batteries). The development of a multifunctional electrocatalyst composed of nitrogen, phosphorus, and fluorine tri‐doped graphene is reported, which was obtained by thermal activation of a mixture of polyaniline‐coated graphene oxide and ammonium hexafluorophosphate (AHF). It was found that thermal decomposition of AHF provides nitrogen, phosphorus, and fluorine sources for tri‐doping with N, P, and F, and simultaneously facilitates template‐free formation of porous structures as a result of thermal gas evolution. The resultant N, P, and F tri‐doped graphene exhibited excellent electrocatalytic activities for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER). The trifunctional metal‐free catalyst was further used as an OER–HER bifunctional catalyst for oxygen and hydrogen gas production in an electrochemical water‐splitting unit, which was powered by an integrated Zn–air battery based on an air electrode made from the same electrocatalyst for ORR. The integrated unit, fabricated from the newly developed N, P, and F tri‐doped graphene multifunctional metal‐free catalyst, can operate in ambient air with a high gas production rate of 0.496 and 0.254 μL s^?1 for hydrogen and oxygen gas, respectively, showing great potential for practical applications.     

对比分析三角Pr3+中心在CsCdBr3和GdCl3晶体中的能级分裂

以Racah的群表示论和Slater的波函数理论为基础,分别建立了4f2组态离子Pr3+在三角晶体场C3v和C3h中的91×91完全能量矩阵,并对Pr3+离子掺杂在卤化物CsCdBr3和GdCl3中的Stark能级做了计算与分析. 结果显示计算值与实验值吻合很好,表明在分析由稀土离子掺杂体系的能级分裂时,完全能量矩阵方法是有效的方法. 此外,将两种具有不同点群对称的体系的能级分裂情况作了比较,结果显示六阶晶体场参量对能级分裂的影响是不能忽略的,而且CsCdBr3:Pr3+和GdCl3:Pr3+将产生不同程度的畸变.     

Cu-doped flower-like hematite nanostructures for efficient water splitting applications

This study reports the successful preparation of Cu-doped hematite (α-Fe₂O₃) flower-like nanostructures with different Cu concentrations on FTO glass substrates using a facile hydrothermal method. The Cu-doped α-Fe₂O₃ flower-like nanostructure combines the advantage of p-type doping with the feature of a flower-like architecture. The prepared nanostructure film was applied as a photocathode in a photoelectrochemical (PEC) water splitting experiment and achieved a significantly improved photocurrent density of −5.34 mA cm⁻² at −0.6 V vs. reversible hydrogen electrode (RHE) for 1 mol% Cu doping. The obtained photocurrent is about 4.85 times higher than that of the pure α-Fe₂O₃ based photoelectrode. The incorporation of Cu into α-Fe₂O₃ results in a dramatic enhancement in the water splitting performance. The enhancement is gained through an improvement in light harvesting and charge carrier separation. The copper-modified α-Fe₂O₃ sample also exhibited an up shift in the conduction band edge potential, which is energetically favorable for the water reduction reaction. This result demonstrated high performance PEC water splitting as a potential route for the production of hydrogen gas using a single Cu-doped α-Fe₂O₃ photoelectrode without the need for other catalysts and hybrid structures.     

Perovskite membrane reactor for continuous and isothermal redox hydrogen production from the dissociation of water

The redox water splitting is one of the most promising routes for sustainable hydrogen production. Towards this goal, serious technological obstacles are set: (i) by the non-isothermal operation of the redox process, that causes serious reactor construction problems, and (ii) by the need for efficient high temperature oxygen/hydrogen separation technology which is a very challenging development. In this paper, perovskite materials having the formula La_0.3Sr_0.7FeO₃ were synthesized and subsequently tested for their high temperature oxidation/reduction behavior. The redox activity of the materials in relation to the water splitting reaction has been also investigated. Dense, disc shaped membranes of the materials were synthesized and placed in a membrane reactor. Experiments at 1133 K revealed the possibility of performing the reduction and oxidation steps simultaneously and isothermally on each side of the membrane reactor. A steady-state situation was thereby achieved where hydrogen was continuously produced on one side while the material was simultaneously regenerated on the other side. The created oxygen vacancy gradient formed the driving force for a continuous flux of vacancies from the membrane reduction surface to the membrane oxidation surface. The hydrogen production rate under the particular experimental conditions estimated to be ∼47.5 cm³ H₂ (STP) m⁻² min⁻¹. It could be increased by a factor of approximately 3, up to ∼145 cm³ H₂ (STP) m⁻² min⁻¹, if the membrane reduction was enhanced with a reductant such as carbon monoxide. This approach resulted in an efficient execution of the water gas shift reaction towards high purity hydrogen production.     

On the triplet nature of paramagnetic centers in conducting polymers

Temperature dependences of the magnetic susceptibility of solutions and powders of polyaniline synthesized by oxidative polymerization using two methods were measured by ESR in the temperature range from 123 to 423 K. The dependences observed can be described by the integral of susceptibility of the polymer fragments in the triplet state over the singlet—triplet splitting from E ₁ to E ₂ with constant weight. The susceptibility of the fragments was accepted to obey the Bleaney—Bowers equation. The most part of the experimental dependences can be presented as the sum of the temperature-independent susceptibility and the susceptibility obeying the Curie law. The both susceptibilities are described in a single manner at E ₁ < 0. In some cases, the comparison of the calculated and experimental dependences makes it possible to determine the length of the fragments L. The conditions of polymer synthesis, heating, and water vapors affect the E ₁ and E ₂ values. A similar analysis can be applied to other conducting polymers. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 316–321, February, 2008.