Co_2Si@C催化剂的合成及其加氢脱硫性能

采用微波法制备了Co_2Si@C催化剂并对其在加氢脱硫反应中的催化性能进行了研究.通过XRD、 XPS、 TEM和N_2-物理吸附表征分析Co_2Si@C催化剂的组成和结构. Co_2Si@C催化剂具有一致的介孔结构,高钴含量(21%)、高比表面积(116.6 m~2·g~(-1))和均匀分布的纳米粒子.由于硅原子对钴原子结构和参数的修饰、纳米粒子效应和高金属含量等因素, Co_2Si@C催化剂在温和的反应条件下(340℃和3.0 MPa)具有良好的加氢脱硫活性和对直接脱硫(DDS)反应途径的高选择性,产物联苯的选择性超过了60%.     

铂合金氧还原催化剂:合成、结构和性能

质子交换膜燃料电池是一种将燃料中的化学能直接转化为电能的装置,它具有转化效率高、能量密度高、低温启动、易于操作等优点,因而被认为是最具发展前景的新能源利用方式,在电动汽车、便携电源及分散式电站有着广泛应用.但是,目前质子交换膜燃料电池技术的发展面临着巨大挑战,主要问题包括高成本、低功率密度和低寿命.众所周知,质子交换膜燃料电池中的阴极氧还原反应在酸性条件下是一个复杂的四电子过程,动力学速度缓慢,限制了电池的最终性能.目前大量使用的阴极氧还原催化剂是细小的铂或铂合金纳米颗粒负载在碳载体上,其成本占燃料电池总成本的比例最大.制约燃料电池商业化发展的另一个重要问题是电池寿命低,其中氧还原催化剂的稳定性是决定电池寿命的主要因素.在这样的研究背景下,如何降低催化剂中铂的用量、提高催化剂活性和稳定性显得尤为重要,这也是近年来国内外学者研究的热点.在铂基合金催化剂中,通常采用过渡金属元素作为掺杂元素,由于原子半径不匹配(几何效应)以及电子结构不同(电子效应),合金催化剂表现出优于纯铂催化剂的催化性能.近几年,对于铂基合金催化剂的研究已取得重大进展,以合金组成和结构研究为基础,通过精确控制原子结构、调控表面电子状态以及制备工艺,获得了各种特殊形貌的催化剂,大大提高了催化活性.本文深入综述了近年来铂基合金氧还原催化剂制备、形貌和性能,特别关注了催化剂形貌和催化活性之间的关系.值得注意的是,具有有序原子排列的铂合金催化剂不仅在半电池中表现出优异活性,在实际质子交换膜燃料电池中也显示了很好的活性和稳定性.另一方面,碳载体的形貌及微观结构也对提高催化活性和稳定性起到决定性作用,通过化学手段加强金属纳米颗粒与碳载体之间的相互作用也是提高催化剂稳定性的重要途径.尽管铂基氧还原催化剂在近几年取得了重要进展,但在实际商业化过程中还存在诸多挑战,本文在综述进展的基础上,对铂基催化剂的发展提出了展望.首先,对于氧还原反应机理仍需要深入研究,采用更加精确的理论模型模拟氧还原动力学过程,以获得影响催化活性的关键因素.其次,提高催化剂在膜电极中的催化活性和利用率.目前,氧还原催化剂在半电池测试中性能优异,但是实际燃料电池操作条件下其性能远不能达到要求,这与膜电极、催化剂层及扩散层结构相关.因此,基于不同铂基催化剂的特性,合理设计膜电极组件的结构是将催化剂进行实际应用的基础.最后,催化剂的稳定性仍需进一步提高,尽管目前大部分催化剂在实验室半电池研究中表现了很好的稳定性,但在实际燃料电池中的稳定性研究还不足,而且对催化剂在膜电极中性能衰退机理的研究也非常有限.因此,对于铂基氧还原催化剂的研发仍需要国内外科研工作者不懈的努力.     

三氟乙酸酐(TFAA)促进的Stieglitz重排反应制备苯胺

本工作使用简单易得的三氟乙酸酐作为活化试剂,拓展了Stieglitz重排反应的底物适用范围,发展了一种通过C—C键断裂由苯乙基羟胺制备芳基伯胺的方法.该反应条件较为温和且对官能团具有较好的兼容性.机理研究表明,反应经历了活性三氟乙酸酯中间体的原位生成,并通过C—C和N—O键的断裂实现芳基迁移的过程.     

Modification of Hole Transport Layers for Fabricating High Performance Non‐fullerene Polymer Solar Cells

Interfacial engineering is expected to be a feasible strategy to improve the charge transport properties of the hole transport layer (HTL), which is of crucial importance to boost the device performance of organic solar cells (OSCs). In this study, two types of alcohol soluble materials, 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F₄‐TCNQ) and di‐tetrabutylammoniumcis–bis(isothiocyanato)bis (2,2’‐bipyridyl‐4,4’‐dicarboxylato) ruthenium(II) (N719) dye were selected as the dopant for HTL. The doping of F₄‐TCNQ and N719 dye in poly (ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with and without integrating a graphene quantum‐dots (G‐QDs) layer has been explored in poly[[2,6′‐4‐8‐di(5‐ethylhexylthienyl)benzo[1,2‐b:3,3‐b]dithiophene][3‐fluoro‐2[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thio‐phenediyl:(2,2′‐((2Z,2′Z)‐(((4,4,9, 9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(4‐((2‐ethylhexyl)oxy)thiophene‐5,2‐diyl))bis(methanylylidene))bis(5,6‐difluoro‐3‐oxo‐2,3‐dihydro‐1H‐indene‐2,1‐diylidene))dimalononitrile (PTB7‐Th:IEICO‐4F) OSCs. The power conversion efficiency of the non‐fullerene OSCs has been increased to 10.12% from 8.84%. The influence of HTL modification on the nano‐morphological structures and photophysical properties is analyzed based on the comparative studies performed on the control and modified devices. The use of chemical doping and bilayer strategy optimizes the energy level alignment, nanomorphology, hole mobility, and work‐function of HTL, leading to considerable reduction of the leakage current and recombination losses. Our work demonstrates that the doping of HTL and the incorporation of G‐QDs layer to constitute a bilayer HTL is an promising strategy to fabricate high performance non‐fullerene polymer solar cells     

Construction of mixed carboxylate and pyrogallate building units for luminescent metal-organic frameworks

A metal-organic framework,Ce-FDM-50,was constructed by employing gallic acid featuring both carboxylate and pyrogallate as the coordinating sites and Ce(Ⅲ).The co-assembly of the carboxylates and pyrogallates with two metal ions have achieved a new type of paddle wheel secondary building unit.These building units were further joined by organic struts to obtain frameworks in sql topology.This synthetic approach could be expanded to five different lanthanide metals(Nd,Eu,Gd,Tb,Yb)for the construction of a series of isoreticular MOFs based on FDM-50,and even MTV-MOFs in which mixed lanthanide metals with specific ratios were distributed.In addition,featuring the lanthanide metals as the inorganic nodes in the network,Tb-FDM-50 showed distinct luminescence properties that could be furtherly tuned for variable applications.     

有机电极材料固定化策略

有机电极材料因其理论比容量高、低成本、环境友好以及分子结构可设计性强等特点,有望成为下一代可持续和多功能能量储存设备的有效电极材料。然而,根据“相似相溶”原理,该类材料极易溶解在有机电解液中,导致电池容量衰减快、循环稳定性和倍率性能也较差。目前已有许多研究致力于通过“固定化”过程解决有机电极材料的溶解问题。本综述针对有机电极材料的固定化策略展开评述,介绍了有机电极材料的固定化机理,以及各种固定化策略在不同种类有机电极材料中所起的作用,指出了有机电极材料面临的挑战,并对未来的研究和改进方向进行展望。     

大气颗粒物中棕色碳的化学组成、来源和生成机制

大气颗粒物中棕色碳(BrC)在近紫外波段具有强吸光性,并因其显著的气候效应被广泛关注。BrC组成、来源、演变和光学性质的不确定性是造成气候模型估算气溶胶辐射强迫不确定性的重要因素。本文综述了大气颗粒物中BrC的化学组成、来源和生成机制,聚焦分子水平上BrC组成、二次生成机制和吸光间的关联。大气颗粒物中BrC的主要类别包括有机溶剂(甲醇)提取的碳质组分、水溶性有机碳及类腐殖质; 分子水平上,硝基芳香烃和含氮杂环有机物是BrC的主要发色团。BrC的来源包括生物质等不完全燃烧一次排放和挥发性有机物氧化二次生成; 二次生成途径主要包括人为源芳香烃氧化生成硝基芳香烃等含氮组分、羰基化合物与铵/胺反应生成含氮杂环组分或低聚物。前体物和反应条件影响二次生成BrC的组成和吸光性质; BrC在大气传输过程中还会发生“光漂白”现象。在分子水平上识别和阐明BrC的发色团、二次生成机制及其演变过程是未来该领域的重点研究方向。     

Thermo IRIS IntrepidⅡ型电感耦合等离子体发射光谱仪故障快速判断方法

针对Thermo IRIS IntrepidⅡ型电感耦合等离子体发射光谱仪（ICP-OES）在测定含金基体溶液中的杂质元素时,仪器出现灵敏度下降、稳定性变差等现象,通过故障现象分析和排查,给出相应的解决方案,确保仪器恢复到正常使用状态.     

Application of Lectin Microarrays for Biomarker Discovery

Many proteins in living organisms are glycosylated. As their glycan patterns exhibit protein-, cell-, and tissue-specific heterogeneity, changes in the glycosylation levels could serve as useful indicators of various pathological and physiological states. Thus, the identification of glycoprotein biomarkers from specific changes in the glycan profiles of glycoproteins is a trending field. Lectin microarrays provide a new glycan analysis platform, which enables rapid and sensitive analysis of complex glycans without requiring the release of glycans from the protein. Recent developments in lectin microarray technology enable high-throughput analysis of glycans in complex biological samples. In this review, we will discuss the basic concepts and recent progress in lectin microarray technology, the application of lectin microarrays in biomarker discovery, and the challenges and future development of this technology. Given the tremendous technical advancements that have been made, lectin microarrays will become an indispensable tool for the discovery of glycoprotein biomarkers.     

Sorbents for the Direct Capture of CO2 from Ambient Air

The urgency to address global climate change induced by greenhouse gas emissions is increasing. In particular, the rise in atmospheric CO₂ levels is generating alarm. Technologies to remove CO₂ from ambient air, or “direct air capture” (DAC), have recently demonstrated that they can contribute to “negative carbon emission.” Recent advances in surface chemistry and material synthesis have resulted in new generations of CO₂ sorbents, which may drive the future of DAC and its large‐scale deployment. This Review describes major types of sorbents designed to capture CO₂ from ambient air and they are categorized by the sorption mechanism: physisorption, chemisorption, and moisture‐swing sorption.