On the use of surface-confined molecular catalysts in fuel cell development

Fuel cells have the potential to provide sustainable clean energy but are hampered by the reliance on Pt as an electrocatalyst for half-cell reactions. Bio-inspired molecular catalysts, composed of Earth-abundant elements, have shown promise as alternative electrocatalysts for fuel oxidation and oxygen reduction reactions. This article provides a concise overview of recent progress in this area with particular focus on (i) electrodes modified with molecular catalysts for fuel oxidation and O₂ reduction and (ii) fuel cells incorporating surface-confined molecular catalysts for both anodic and cathodic reactions. Finally, the prospect and challenges of using molecular catalysts in fuel cell assemblies are discussed.     

Oxidation-Reduction Condensation a New Method for Peptide Synthesis

Organic trivalent phosphorous compounds such as trialkyl phosphites and trialkyl or triarylphosphines are well known to be powerful deoxygenation reagents and have been used in various reduction reactions. But, it is rather a new aspect to make use of their property of deoxygenation for the gsneration of active acyl groups. Since the discovery of the rezcticn of mercuric acetate with trivalent phosphorous coqounds to yield acetic anhydride, our attention has been fccused on the generation of acyl groups and several novel reactions have been found which are applicable to the preparation of acid anhydride and peptide linkages. In considering these reactions described herein, it is necessary to choose appropriate oxidation reagents together with reducing reagents (trivalent phosphcrous compounds) because these dehydration reactions essentially proceed via an oxiaation reduction process as depicted in the following scheme.     

2种添加剂在电有机合成中的应用

通过电解实验分别考察了5个阴极电还原反应和1个阳极电氧化反应在加入添加剂前后电流效率和转化率的变化。所选择的6个反应可以分为2类,一类是原料以分子形式存在于电解液中的反应,另一类是原料以离子形式存在于电解液中的反应。实验间二硝基苯电还原制间苯二胺,3-甲基吡啶氧化制烟酸和邻硝基酚电还原制邻氨基酚(酸性条件下)属于前一类反应,加入添加剂后,它们的电流效率分别由原来的65.69%、28.00%和45.09%变为66.15%、28.45%和37.07%,说明添加剂对原料以分子形式存在的反应没有作用或有抑制作用。实验邻硝基酚电还原制邻氨基酚(碱性条件下),丁二酸的电解全盛和水杨酸电还原制水杨醛属于后一类反应,加入添加剂后,它们的电流效率分别从原来的49.37%、65.06%和24.55%提高到75.80%、78.60%和30.06%,说明添加剂能够提高原料以离子形态存在的反应的电流效率。     

Reduction–Oxidation of Chromium Ions in Aqueous Solution by Treatment with Atmospheric-Pressure Direct-Current Discharge in Argon

Kinetic features of the oxidation–reduction processes of chromium ions in a potassium dichromate aqueous solution subjected to treatment in argon atmospheric-pressure dc discharge have been investigated in the discharge current range of 20–80 mA and the dichromate concentration range of 0.1–0.5 mmol/L. The solution served as the discharge cathode. It has been revealed that the discharge treatment stimulates the reduction reactions of Cr⁶⁺ to Cr³⁺ ions and the reverse reactions of oxidation of Cr³⁺ to Cr⁶⁺ ions; i.e., the oxidation–reduction reactions are reversible. The limiting degree of reduction of Cr⁶⁺ ions has been found to depend on the discharge current and the initial concentration of the solution. The apparent rate constants of oxidation and reduction have been determined, and the energy efficiency of the process has been evaluated. The data are compared with the results obtained earlier for a discharge in air.     

Non‐Redox‐Metal‐Catalyzed Redox Reactions: Zinc Catalysts

The advantages of zinc catalysts, such as their low toxicity, low cost, and environmentally benignity, are encouraging organic chemists to explore their applications in organic synthesis. As a non‐redox metal, zinc catalysts have been investigated in redox reactions over the past few decades. Because of the importance of redox reactions, the interest in zinc catalysts, and the fact that no review on zinc‐catalyzed redox reactions has been published, herein, I have collected and summarized the main contributions in this area. This review is divided into two parts: reduction reactions and oxidation reactions.     

Systematic procedure for reduction of kinetic mechanisms of complex chemical processes and its software implementation

Feasibility of multidimensional hydrodynamic modeling depends critically on the availability of accurate reduced kinetic mechanisms of physical and chemical processes taking place in the system. Such mechanisms should describe the processes under consideration within a specified error tolerance in the range of initial conditions of interest while keeping the number of species and reactions as small as possible. We have developed an advanced tool for reduction of detailed kinetic mechanisms with a minimal human effort. The tool includes 10 reduction and 2 analysis methods which are based on the results of zero-dimensional modeling. The methods can be combined and applied in sequence. The reduction tool has been implemented as a part the Chemical Workbench computational package and has been tested for a number of large kinetic mechanisms of gas-phase processes. Using this tool, we reduced the mechanism of tar gasification from 177 species and 879 reversible reactions to only 83 species and 278 reactions, while the mechanism of methane combustion initially involving 127 species and 1,206 reactions was reduced to 42 species and 173 reactions.     

Oxidation leading to reduction: redox-induced electron transfer (RIET)

Complex electron transfer reactions have been characterized whereby in addition to electron transfer, subsequent electrochemical, chemical and even in some cases biological consequences occur. These include a secondary electron transfer that leads to a major rearrangement of the electronic structure, such that an initial oxidation leads to a reduction (or an initial reduction leads to an oxidation) for these valence ambiguous compounds. Mixed valency and valence-tautomeric behaviors can additionally result from these complex electron-transfer-induced reactions.     

REACTIONS OF ARYLSULPHONYL FLUORIDES

Abstract

Substituent effects have been investigated for both nucleophili -ic and reduction reactions of arylsulphonyl fluorides in aqueous media. The significance of the results will be discussed in relation to the reactions of arylsulphonyl chlorides.     

Kinetics of Conversions of Peroxynitrous Acid in Reactions of Isomerization,Decomposition, and Reduction by Cyclohexane

We have studied the kinetics of decomposition and reduction of peroxynitrous acid HOONO by cyclohexane in aqueous solutions. We used the measured effective rate constants of the reactions to compare the reactivities of the acid in the processes of isomerization, decomposition, and reduction.     

Disparate behavior of ketones and thioketones on reaction with organolithiums

The reactions of alkyllithiums with ketones and thioketones proceed in fundamentally different ways. Whereas alkyllithiums add to the carbonyl carbon of ketones to give tertiary alcohols, the reaction with thioketones proceeds to give secondary thiols by reduction of the CS group. Transition states for the addition and reduction reactions of acetone and thioacetone in ethereal solution have been located and the computed activation free energies are in agreement with the observed behavior of ketones and thioketones in reactions with alkyllithiums.     

碳催化剂在催化反应中的应用

由于碳材料表面存在缺陷,可生成具有不同性能的活性位,因此可催化不同的热催化反应.我们首先介绍了单质碳材料的表面结构化学:其表面活性位主要为含杂原子官能团;然后对其可催化的反应进行了介绍:碳单质材料可催化选择性氧化反应、高级氧化反应、还原反应、烷烃活化反应、酸催化反应、电催化还原和氧化反应等.对碳单质催化剂的制备方法、所...     

Concentration Dependent Catalytic Activity of Glutathione Coated Silver Nanoparticles for the Reduction of 4-Nitrophenol and Organic Dyes

In the present study, we have synthesized glutathione modified silver nanoparticles (GSH-AgNPs) in aqueous medium and are characterized by absorption, high resolution transmission electron microscope (HR-TEM), selective area electron diffraction (SAED) pattern, dynamic light scattering (DLS), Zeta potential and Fourier transform infrared (FT-IR) spectroscopic measurements. Catalytic activity of GSH-AgNPs has been evaluated for the reduction reactions of 4-nitrophenol (4-NP), methylene blue (MB dye) and eosin Y (EY dye) in presence of sodium borohydride including the effect of catalyst concentration on the catalytic activity. Furthermore, the rate constants of reduction reactions are determined, which are linearly enhanced upon increasing the concentrations of GSH-AgNPs. It is explored that reduction reactions such as 4-NP, organic dyes by NaBH₄ in the presence of catalyst follow a pseudo first order kinetics. The catalytic reduction of 4-NP and organic dyes proceed with a faster rate even in the presence of nanomolar concentration of catalyst.     

A study on the reactions of NADH models with electron-deficient alkenes. A probe for the extreme of concerted electron-hydrogen atom transfer mechanism

The reactions of 9-fluorenylidenemalononitrile (FDCN) and 1,1-diphenyl-2,2-dicyanoethylene (DPCN) with Hantzsch ester (HEH), N-methyl Hantzsch ester (Me-HEH), and 1-benzyl-1,4-dihydronicotinamide (BNAH) in oxygen-saturated acetonitrile have been studied. The aerobic reactions with HEH give solely reduction products. However, reactions with Me-HEH and BNAH not only result in reduction products, but also give varying amounts of oxidation products. The amount of oxidation product appears to be related to the electronic character and bulkiness of reactants. We propose that all these reactions follow a general mechanism of concerted electron-hydrogen atom transfer mechanism. If the electron-transfer complex is very tight, only ‘concerted hydride transfer reaction’ occurs. However, if the electron-transfer complex is not so tight, oxygen can capture the radicaloid intermediate to result in oxidation products.     

Étude de la reduction électrochimique des hydrocarbures aromatiques polynucleaires dans le diméthylacétamide

The electrochemical reduction of some aromatic polynuclear hydrocarbons has been studied in anhydrous dimethylacetamide. The half-wave potentials of the stages of reduction and the nature and the reversibility of the reactions have been studied with rotating platinum and dropping mercury electrodes. A study in greater detail of the first stage of the reduction has shown the formation of radical anions by electrochemical methods and electron spin resonance.     

含侧链手性噁唑硼烷催化还原苯乙酮对映选择性的理论研究

用AMI方法研究了含侧链手性恶唑硼烷催化苯乙酮还原反应的对映选择性机理 及其取代基和构型对对映选择性的影响。计算结果表明，含侧链手性恶唑硼烷催化 还原苯乙酮的反应机理与Corey等人提出的机理相符合，在此类硼催化剂的作用下 ，苯乙酮还原产物的绝对构型以R型为主。当恶唑硼烷环N(3)，B(2)上无取代基时 ，C(4)，C(5)位的取代基及其构型是不对称催化反应对映选择性的主要影响因素。     

聚合物负载的手性催化剂和手性试剂和合成及应用

近年来,用聚合物负载的手性催化剂和手性试剂完成的不对称合成反应主要集中在潜手性酮的不对称还原反应;烯烃的不对称双羟基化反应;烯烃的不对称环氧化反应;不对称Ｄｉｅｌｓ－Ａｌｄｅｒ反应和饱和碳原子上的不对称取代反应。就近十年来聚合物负载手性催化剂和手性试剂的合成及应用进行了讨论。     

C60的化学修饰

C_(60)分子中含Pyracylene结构。具有苯环烯烃、共轭烯烃的性质。本文讨论了它的加成反应(包括卤化,胺化等),Friedel—Crafts反应,氧化反应,Diels—Aider反应,成络反应,自由基反应和还原反应的进展。参考文献52篇。     

Covalent modification of graphitic carbon substrates by non-electrochemical methods

New methods for modifying graphitic carbon surfaces without electrochemical assistance, and without the deliberate formation of carbon surface oxygen functionalities, have emerged in the past decade. The approaches rely on spontaneous reactions of aryldiazonium salts, primary amines, ammonia and iodine azide at room temperature, chemical reduction of aryldiazonium salts, reactions of alkenes and alkynes at elevated temperatures and photochemical reactions of alkenes, alkynes, azides and diazirines. This review describes the methodology and scope of these reactions at graphitic carbon materials (excluding carbon nanotubes) and examines mechanistic possibilities and future prospects.     

Electrochemical impedance spectroscopy in interfacial studies

A fundamental aim in the field of electrochemistry is to investigate electron transfer events caused by electrode processes, which are more commonly described as redox reactions. In this short review, an overview of the use of electrochemical redox reactions in the realm of organic synthesis is given. These reactions can be divided into three subcategories: cathodic reduction, anodic oxidation, and a paired approach. This short review illustrates the basic schemes of these reactions and introduces representative examples that have been reported in the past 2 years, with a particular emphasis on the development of novel reactions.     

Electrocatalytic and photocatalytic applications of atomically precise gold-based nanoclusters

With advances in cluster chemistry, atomically precise gold nanoclusters(NCs) with well-defined composition and tunable structure provide an exciting opportunity to uncover the specific roles of the geometrical and electronic structures as well as the capped ligands in overall catalytic performances. The Au NCs possess quantum energy levels and unique optical properties,which have exhibited unexpected photocatalytic and electrocatalytic activities. In this review, we first highlight the electrocatalytic applications of Au NCs, including hydrogen evolution reaction, oxygen reduction reaction, CO_2 reduction and catalytic oxidation reactions, and then present Au NCs-driven photocatalytic applications such as selective organic reactions, decomposition of pollutants and energy conversion reactions. Finally, we conclude this review with a brief perspective on the catalytic field of Au NCs.