金属单原子催化剂在电催化二氧化碳和水裂解的研究进展

利用电催化技术开发新型能源,是替代传统能源的一种新策略,大量使用化石燃料导致的环境问题有望会通过此技术的发展而得到良好解决,设计并制备出高效稳定的电催化剂对于新型能源技术开发应用至关重要.单原子催化剂(SACs)在载体上具有原子分布的活性位点,是催化领域的新兴材料,具有美好的应用前景,现已成为电催化领域的研究热点.在此综述中,详细阐述了单原子电催化剂的一般载体、制备方法及其先进表征方法,系统总结了单原子电催化剂在能量转化和环境保护(CO₂还原、水裂解)方面的应用.同时,基于各种单原子催化剂研究的最新进展,简单阐述了催化机制,讨论了单原子催化剂在电催化方向的发展挑战和前景,希望为单原子电催化剂的合成、设计和应用提供经验,以更好地促进电催化能量转换方面的发展.     

电化学联用技术研究微生物的胞外电子传递机制

胞外电子传递（EET）是指氧化还原反应所产生的电子在微生物细胞内和细胞外的电子受体/电子供体之间互相转移的过程,这一过程伴随着能量和物质的转化。阐明EET机制是提高微生物能量和物质转化效率的基础,为元素的生物地球化学循环、金属防腐以及生物电化学系统的应用等提供理论支撑。电化学技术作为研究电极/溶液界面电子转移的简便、有效方法,在研究微生物的直接电子传递和间接电子传递机制中发挥了重要的作用,也促进了EET机制的研究从宏观层面到微观层面不断深入。本文综述了研究微生物EET机制所涉及的电化学联用技术（包括微电极、扫描电化学显微镜、电化学联用光学显微镜和光谱电化学等）;详细介绍了这些电化学联用技术的功能和优势;重点阐述了这些电化学联用技术如何推动着EET机制的研究,从宏观的生物膜层面到微观的单个微生物细胞、蛋白和分子层面不断深入;展望了新的电化学联用技术在EET研究领域的应用前景。     

无机多核过渡金属氰化物薄膜修饰电极的新进展

本文对普鲁士兰类无机多核过渡金属氰化物薄膜化学修饰电极的近年发展及其在电催化，电色效应，离子选择性电极和生物活体分析等方面的应用进行了评述，引用文献50篇。     

革兰氏阳性电活性菌的电子传递及其应用

电活性菌将电子从胞内转移至胞外电子受体或者将胞外电子转移至胞内的过程为胞外电子传递,其在微生物群落间的电子传递及元素的地球化学循环过程中发挥重要作用。电活性菌的胞外电子传递研究前期主要集中于革兰氏阴性菌,由于革兰氏阳性菌与革兰氏阴性菌的膜结构/厚度明显不同,因此二者的电子跨膜传递途径差异明显。革兰氏阳性菌因分布广泛且可在高温、低pH、高pH和高盐等环境中生存,其电活性和电子传递机制也逐渐引起关注。本文归纳总结了革兰氏阳性电活性菌的电子传递类型,基于厚壁菌门、放线菌门和绿弯菌门的分类阐述胞外电子传递的研究进展,分析了革兰氏阳性电活性菌在污染物降解、生物能源和工业制品合成等方面的应用,并展望了未来的发展方向。     

微纳器件技术在电催化前沿研究中的应用进展

电催化在能源转化与存储方面有着广阔的应用前景,并已成为当今世界的研究热点.对于大多数电催化体系而言,其催化性能的优化与提升,都需倚赖活性中心的合理构建以及催化机制的精确描述.为此,测试手段的不断丰富可以极大促进电催化的深入研究与应用.近年来,微纳(器件)加工技术的不断成熟和跨学科发展为电催化材料和过程的研究提供了更精细的全新平台.本文针对电催化研究的不同方向,从结构表征与精准测量、场效应调控和电输运关联动力学三个方面总结了近年来微纳器件技术在电催化领域中的研究进展.最后,本文展望了微纳器件技术在电催化领域所面临的挑战及应用前景.     

碳纳米管尺寸对电化学反应活性的影响

制备不同尺寸的多壁碳纳米管(MWNT)修饰电极,应用循环伏安法研究了相同管径、不同管长和相同管长、不同管径的多壁碳纳米管修饰电极在K3Fe(CN)6溶液中的电化学行为及其对尿酸、多巴胺等生物分子的电催化作用,以及尺寸效应对碳纳米管修饰电极电化学活性的影响规律.结果显示,在同一条件下,短管的MWNT比长管的更能有效促进K3Fe(CN)6的电子传递,更有利于对生物分子的电催化;管径对它的电化学行为及生物电催化活性影响较小,无明显规律.主要原因在于碳纳米管管端、管壁的不同电化学活性.     

微生物电化学系统电子中介体

电化学活性微生物与电极之间的胞外电子传递在微生物电化学系统(microbial electrochemical systems,MESs)产能、生物修复等功能的实现中起着关键作用.目前,研究者对微生物胞外电子传递机理了解有限,限制了MESs的应用.相比于需要微生物功能蛋白与电极接触才能发生的直接电子传递,间接电子传递可通过具有可逆氧化还原活性的电子中介体(electron transfer mediators,ETMs)实现电子的传递,从而有效提高微生物胞外电子传递效率.在间接电子转移过程中,ETMs起着中间电子受体和中间电子供体的作用,即被还原后可将电子传递给最终电子受体并被重新还原;理论上每个ETMs分子可以循环数千次,因此ETMs对特定环境下终端氧化物(如铁离子)的循环有着极其显著的作用.本文系统总结了MESs中ETMs及间接电子传递机制近年来的研究进展,并且在此基础上探讨了ETMs在MESs中的研究趋势,以期推动MESs在生物修复、能源生产方面的实际应用.     

生物质平台化合物电催化制备高值燃料与化学品研究进展

生物质是一类丰富的可再生碳基资源, 有望代替传统化石资源生产燃料和化学品, 受到了广泛关注和研究. 近年来, 电催化作为一种绿色高效的转化策略, 成为生物质催化转化的重要研究方向之一, 具有巨大的应用前景. 本文总结了生物质平台化合物电催化制备高附加值燃料与化学品的研究进展, 根据反应类型重点介绍了电催化氧化、 还原和偶联反应, 对催化反应过程和机理进行了阐述, 并对电催化生物炼制的前景进行了展望.     

电生物还原降解二氯酚的动力学特性及功能菌解析

采用电辅助微生物(电生物)体系对二氯酚(2,4-DCP)进行了还原降解研究, 应用聚合酶链式反应-单链构象多肽技术(PCR-SSCP)对微生物群落结构进行解析, 并通过16S rRNA基因克隆及测序构建了系统进化树. 结果表明, 电生物体系对二氯酚的降解符合零级反应动力学特征, 体系中主要以肠球菌(Enterococcus)、 假单胞菌(Pseudomonas)和拟杆菌(Bacteroidales)为优势菌群, 这些菌群在电子传递中起着主要作用. 电生物体系中存在着电极与细胞色素c和脱氢酶的辅酶(NAD)及污染物间的逆向电子传递途径, 可实现电极-微生物-污染物多相界间的长程电子传递.     

电驱动下的环境污染物厌氧生物转化—电子转移原理和应用实例

厌氧环境下一些微生物能够接受来自于电极的电子并将电子传递至环境污染物,这使得电驱动下生物还原技术在可持续性废水处理以及生物修复方面受到越来越多关注.此体系中,阴极电子传递被认为是影响环境污染物厌氧转化可行性和效率的制约因素.文中首先评述可能的电子传递原理,包括水解氢气介导的间接电子传递、人工合成电子穿梭体或者细菌分泌电子穿梭体介导的间接电子传递、以及电极与细菌之间的直接电子传递等途径.相比间接电子传递,直接电子传递避免了将电子传递给没有起作用的介体及没有和电极接触的浮游微生物,因而更加节能.另外,列举了自养反硝化、生物还原脱氯、重金属生物还原、CO2生物还原以及硫酸盐生物还原等应用实例.最后,提出了此领域研究发展亟需解决的两个重要问题,包括阴极生物膜的培养以及电子从电极转至微生物内在机理的解析.     

抗氧化剂活性的电子顺磁共振（EPR）研究

抗氧化剂在化工、食品以及生命科学等领域具有重要的作用,近年来更是由于其在解决与人类健康相关问题方面所起到的重要作用而受到广泛重视。本综述较为详细地介绍了利用电子顺磁共振（EPR）技术测定抗氧化剂活性的原理和方法,系统总结了近年来在天然抗氧化剂以及合成抗氧化剂化学活性方面的EPR研究最新进展,特别是定量测定表征抗氧化活性...     

Energy filtered transmission electron microscopy for the physico-chemical characterization of aquatic submicron colloids

A combination of energy filtered transmission electron microscopic (EF-TEM) procedures is proposed for the non-perturbing physico-chemical characterization of submicron mineral and organic colloids in aquatic systems. Synthetic hematite microparticles and xanthan polysaccharides were used as well-characterized model colloids in order to determine the optimum EF-TEM analysis conditions. In this paper, it is demonstrated that (i) our model colloids are morphologically representative of naturally occurring mineral/organic associations, (ii) EF-TEM allows the detection of fine xanthan ultrastructures without artefacts of conventional staining methods and (iii) submicron hematite particles can be specifically visualized and spectrometrically measured by EF-TEM within a hematite/xanthan mixture. This EF-TEM procedure appears to be appropriate for the characterization of real aquatic samples.     

格氏试剂与酮反应的一个重要途径: 单电子转移

本文着重阐述了格氏试剂和酮的性质影响反应的一般规律,介绍了普遍接受的格氏试剂与酮反应的机理。讨论了溶剂及微量过渡金属对反应的影响。     

Determination of Sulfite in Botanical Medicine Using Headspace Thin-Film Microextraction and Surface Enhanced Raman Spectrometry

A facile method using headspace thin-film microextraction (HS-TFME) coupled with surface enhanced Raman spectrometry (SERS) has been developed for the determination of sulfite in traditional Chinese herbal medicine. The extraction substrate was synthesized by depositing urchin-like ZnO micron particles on glass sheets using chemical liquid phase deposition. Under the optimal conditions, the intensity of the SERS signal at 630–640?cm^?1 provided a good linear relationship with the concentration of sulfite from 25 to 400?mg/kg, and the linear correlation coefficient (R) was 0.996 with a detection limit of 6?mg/kg. The method was employed for the determination of sulfite in herbal medicines, and the results were confirmed by a traditional distillation-titration method. Therefore, this developed HS-TFME-SERS method may play an important role in the rapid, simple, and selective determination of sulfite residues in Chinese herbal medicine and become a potentially universal method for this analyte in various solid samples.     

THE KINETICS OF ELECTRON TRANSFER FOR A SERIES OF IRON(II) CYCLIDENE COMPLEXES

Abstract

The kinetics of oxidation of a series of iron(II) cyclidene complexes by tris(1,10-phenanthroline)cobalt(III) in methanol have been measured by stopped flow spectrophotometry. The reactions obey a first order rate law when the cobalt(III) complex is present in large excess. The corresponding second order rate constants fall in the range 5.0–130 × 10⁵ M^?1s^?1 (25°C). A linear correlation between the logarithm of the rate constant and the iron(III)/(II) redox potential indicates that the reactions behave as simple outer-sphere electron transfer processes. The self-exchange rate constants for the iron cyclidene complexes have been estimated from the Marcus equation and found to vary between 0.7 × 10⁷ M¹s¹ and 9 × 10⁷ M¹s¹. The dependence of the self-exchange rate constant on ligand structure is discussed.     

渣油加氢处理前后沥青质的微观结构研究

采用元素分析、扫描电镜和透射电镜等分析方法对渣油原料中的沥青质、加氢处理后的沥青质及添加高芳香性轻循环油(LCO)反应后的沥青质进行对比研究。结果发现,渣油加氢处理前后沥青质的表面呈现出光滑表面和多孔的球形颗粒表面两种完全不同的形貌。渣油加氢前后沥青质的芳核堆砌表现出明显的长程无序局部有序的特征;加氢处理后的沥青质芳核片层易于堆砌,出现了多层堆砌、长程有序的类石墨结构。渣油中高芳香性LCO的添加有利于促进沥青质的加氢反应、改善沥青质芳核系统在渣油加氢处理过程中的聚集行为。     

Surface analysis by TEY — Theory and applications

TEY (total electron yield) is frequently used to investigate EXAFS and XANES in the region of low photon energies and high photoabsorption coefficients. We extended the application to quantitative surface analysis [1,2]. For this purpose we developed by analogy to the theoretical approaches of quantitative X-ray fluorescence analysis a correlation between measured TEY-jumps at specific absorption edges of the specimen and the unknown composition. The present paper describes the derivation of the equations for primary and secondary excited contributions to the measured TEY-jumps. We have checked our theory for the example of binary Au-Pd alloys. Besides, the influence of a retarding field between the specimen surface and the electron detector on the analytical results is outlined.Dedicated to Professor Dr. rer. nat. Dr. h.c. Hubertus Nickel on the occasion of his 65th birthday.     

Biphasic oxidation of diaquadichloro(1,10-phenanthroline)chromium(III) by N-bromosuccinimide and the formation of chromium(IV) and chromium(V)

The kinetics of oxidation of diaquadichloro(1,10-phenanthroline)chromium(III) complex, [Cr^III(phen)(H₂O)₂Cl₂]⁺, by N-bromosuccinimide (NBS) is biphasic. The first faster step involves the oxidation of Cr(III) to Cr(IV). The second slower step is due to the oxidation of Cr(IV) to Cr(V). The reaction product is isolated and characterized by electron spin resonance (ESR), IR, and elemental analysis. The chromium(V) product is consistent with the formula [Cr^V(phen)Cl₂(O)]Br. The rate constants k_f and k_s, for the faster and the slower steps respectively, were obtained using an Origin 9.0 software program. Values of both k_f and k_s, varied linearly with [NBS] at constant reaction conditions. The effect of pH on the reaction rate is investigated over the pH (4.11–6.01) range at 25.0°C. The rate constants k_f and k_s increased with increasing pH. This is consistent with hydroxo forms of the chromium species being more reactive than the aqua forms. Chromium(III) complexes, more often than not, are inert. The oxidation of the Cr(III) complex to Cr(IV), most likely, proceeds by an outer sphere mechanism. Since chromium(IV) is labile the mechanism of its oxidation to chromium(V) is not certain.     

Studying banded spherulites in HDPE by electron microscopy

HDPE is a semi-crystalline thermoplastic polymer, with remarkable physical properties such as high chemical resistivity, high impact strength, and high modulus. Compared to the other semi-crystalline polymers, HDPE mostly possesses a high crystallinity, due to which, it exhibits a unique combination of mechanical and chemical resistance properties. In the present work, we have characterized the crystalline spherulites of neat and formulated HDPE compositions thoroughly characterized by different electron microscopy techniques such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). One of the critical steps to obtaining well-resolved SEM images is the sample preparation that typically involves the etching process to elucidate the crystalline spherulites. Though such traditional methodology can effectively be used for neat HDPE, it leads to the creation of undesirable experimental artifacts when used to investigate formulated HDPE compositions. An alternate TEM-based method provides clear images without any artifacts, apart from being a direct and green method and taking relatively a lesser measurement time.