Complementary Design in Multicomponent Electrocatalysts for Electrochemical Nitrogen Reduction: Beyond the Leverage in Activity and Selectivity

Electrochemical nitrogen reduction reaction (eNRR) is promising in place of the Haber–Bosch process for artificial N₂ fixation. However, the high activity and selectivity of eNRR are challenging to achieve simultaneously due to the scaling relations. Such “leverage” between activity and selectivity has severely restricted eNRR. To overcome this bottleneck, the complementary design of electronic structures in multicomponent electrocatalysts has been recently pursued, aiming to maximize the advantages of each component and optimize the multistep reactions, which has stood at the cutting edge in this aspect. Here, we present a minireview of the design, performance, and mechanism of multicomponent electrocatalysts with complementary electronic structures. We particularly emphasize the interactions between N₂ and elements from d-, p-, and s-blocks, which are essential for understanding how these electrocatalysts are beyond the “leverage” between activity and selectivity.     

Di-functional magnetic nanoflowers: A highly efficient support for immobilizing penicillin G acylase

The novel di-functional magnetic nanoflowers (DMNF) which had both epoxy groups and hydrophilic catechol as well as phthaloquinone groups capable of covalently coupling of penicillin G acylase (PGA) were characterized by scanning electron microscopy, transmission electron microscope (TEM), vibrating sample magnetometer, N₂ adsorption, and so on. The studies showed that DMNF possessed “hierarchical petal” structure of nanosheets had specific saturation magnetization of 39.7 emu/g and average pore diameter of 25.4 nm as well as specific surface area of 17.28 m²/g. For hydrolysis of penicillin G potassium catalyzed by the PGA immobilized on DMNF with enzyme loading of 106 mg/g-support, its apparent activity reached 2,667 U/g, which benefited from the “hierarchical petal” and large pore structure of the magnetic DMNF leading to high enzyme loading and fast diffusion of substrate molecules to the immobilized PGA to reaction. The apparent activity of the immobilized PGA could keep 2,408 U/g (above 90% of its initial activity) after repeating use for 10 cycles. The magnetic immobilized PGA exhibited excellent operational stability due to covalently coupling of the enzyme molecules between the support by covalent interaction of the amino groups of PGA and the reactive groups of epoxy, catechol, and phthaloquinone groups on DMNF. Furthermore, the PGA displayed good acid and alkaline resistance as well as thermal stability by immobilization using DMNF.     

A Heterometallic MOF based on Monofunctional Linker by “One-pot” Solvothermal Method for Highly Selective Gas Adsorption

Heterometallic MOFs, as an important branch of MOF materials, open up a new way to design and synthesize innovative MOF materials. Hence, it has positive significance for the development of MOF materials. By utilizing monofunctional linker CBDA [5,5'-(carbonylbis(azanediyl))-diisophthalic acid], a heterometallic MOF In/Gd-CBDA was obtained under “one-pot“ solvothermal method. The three-dimensional framework exhibits (3,4,6)-connected network belonging to a new topology. In addition, the synthetic conditions that affect the growth of crystal have been studied in detail. Numerous experiments led to the finding that the type and composition of solvents are very important for inducing the recognition of carboxylic acid groups at different positions coordination to diverse metals. Furthermore, the mechanism of this kind of heterometallic MOFs assembled by monofunctional linker under “one-pot” solvothermal method has been clarified, which is mainly related to the steric hindrance of functional groups and the properties of heterometals. Based on ideal adsorbed solution theory (IAST), In/Gd-CBDA shows the efficient selective gas adsorption, especially for equimolar mixtures of CO₂/CH₄ (13) and C₃H₈/CH₄ (321). This work of heterometallic MOF material assembled by monofunctional linker under “one-pot” solvothermal method provides a new platform for the development of MOF materials in terms of enriching the topological family and broadening possibilities in advanced applications.     

CHARACTERIZATION OF CIS- AND TRANS-DINITROBIS-(l-CYCLOHEXANEDIAMINE)-COBALT(III) CHLORIDE1

Abstract

Two geometrical isomers of [Co(l-chxn)₂(No₂)₂]Cl have been isolated. The trans-isomer is eluted first from a cellulose ion exchange column as a single isomer. The cis-isomer corresponds to the complex previously reported as the trans-isomer. The cis-isomer with the same CD sign pattern as for the trans-isomer is stereoselectively favored, but a small amount of the second cis-isomer separates using Cellex CM ion exchange cellulose. The CD spectra of the cis- and trans- isomers are similar to those of the corresponding isomers of the l-pn complex.     

北京市“7.21”军地联合应急预警与信息报告建模与仿真

以北京市"7.21"特大自然灾害军地联合应急活动为研究对象,运用EPC方法对预警和信息报告活动进行建模和仿真研究;通过对仿真结果分析,认为存在问题的症结在于目前北京市军地联合应急机构不健全;在重新构建北京市军地联合应急领导小组的前提下,对其进行优化建模和仿真.     

具有包藏结构的三元聚丙烯纳米复合材料结构与性能关系的研究

制备了一种新型聚丙烯 丁苯橡胶 纳米碳酸钙三元纳米复合材料 .研究结果显示 ,复合材料中的大多数纳米碳酸钙粒子被包藏在丁苯橡胶中 ,并与之共同形成分散于聚丙烯树脂中的分散相 ,这种聚丙烯纳米复合材料具有高刚性、高韧性、高耐热性和高的结晶速率 .系统研究了成核剂苯甲酸钠的加入和纳米碳酸钙的用量对该类纳米复合材料相态结构、结晶形态和结晶动力学的影响 ,以及具有包藏结构的分散相粒径和PP中β晶含量对材料性能的影响 .结果表明 ,苯甲酸钠的加入和纳米碳酸钙用量的提高均可使体系中分散相粒径减小 ,结晶速率加快 ,进而使材料的韧性、刚性和耐热性提高 .     

新型激光装置前端系统激光时间脉冲整形技术

对惯性约束聚变实验而言,激光时间脉冲整形具有非常重要的意义。随着惯性约束聚变技术的不断发展,对终端脉冲的时间填充因子的要求越来越高,直接导致了对前端系统时间脉冲整形技术的要求也越来越高。为了满足惯性约束聚变实验对前端时间脉冲整形技术的要求,自行设计了“刀口器”装置。利用这一装置,并结合改进的时空变换脉冲整形技术,在“神光—Ⅱ”的升级装置上,实现了大功率激光装置上的激光时间脉冲整形,在终端得到了脉宽1．16ns、上升沿337ps、下降沿360ps、时间填充因子为81．2％的方波激光脉冲,满足了物理实验对前端系统激光时间脉冲整形的要求。同时,提出了进一步改进的措施,以满足今后物理实验的更高要求。     

"海洋一号"卫星10通道水色扫描仪光学系统的设计

介绍了2002年5月发射的中国“海洋一号”卫星10通道水色扫描仪的光学系统设计。该系统有10个探测通道,波段从可见到远红外,空间分辨率1．1km,并首次采用了“K镜”消像旋系统。     

Optical “visualization” of Pythagorean triples and electrostatic multipoles in quantum dash

The problem of the features of the electron energy spectrum in a quantum parallelepiped has been considered. The family of triply degenerate energy levels has been found for the chosen model of the quantum parallelepiped. The optical transitions in this system has been investigated. It has been established that primitive Pythagorean triples are in the basis of every family of triply degenerate levels and this fact is directly reflected on the optical properties of the quantum dashes. In particular, due to the selection rules for the electronic transitions, it is possible to "visualize" Pythagorean triples theoretically. The dependence of absorption coefficient on the incident photon energy of quantum dash ensemble has been studied. The dipole, quadrupole moments and the electrostatic field created by the electron localized in a quantum dash have been investigated.