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hemistry is the science about breaking and forming of bonds between atoms. One of the most important processes for organic chemistry is breaking bonds C–H, as well as C–C in various compounds, and primarily, in hydrocarbons. Among hydrocarbons, saturated hydrocarbons, alkanes (methane, ethane, propane, hexane etc. ), are especially attractive as substrates for chemical transformations. This is because, on the one hand, alkanes are the main constituents of oil and natural gas, and consequently are the principal feedstocks for chemical industry. On the other hand, these substances are known to be the less reactive organic compounds. Saturated hydrocarbons may be called the “noble gases of organic chemistry” and, if so, the first representative of their family – methane – may be compared with extremely inert helium. As in all comparisons, this parallel between noble gases and alkanes is not fully accurate. Indeed the transformations of alkanes, including methane, have been known for a long time. These reactions involve the interaction with molecular oxygen from air (burning – the main source of energy!), as well as some mutual interconversions of saturated and unsaturated hydrocarbons. However, all these transformations occur at elevated temperatures (higher than 300–500 °C) and are usually characterized by a lack of selectivity. The conversion of alkanes into carbon dioxide and water during burning is an extremely valuable process – but not from a chemist viewpoint.
I knew nothing of the work of C. G. Vayenas on NEMCA until the early nineties. Then I learned from a paper of his idea (gas interface reactions could be catalyzed electrochemically), which seemed quite marvelous; but I did not understand how it worked. Consequently, I decided to correspond with Professor Vayenas in Patras, Greece, to reach a better understanding of this concept. I think that my early papers (1946, 1947, and 1957), on the relationship between the work function of metal surfaces and electron transfer reactions thereat to particles in solution, held me in good stead to be receptive to what Vayenas told me. As the electrode potential changes, so of course, does the work function at the interface, and gas metal reactions there involve adsorbed particles which have bonding to the surface. Whether electron transfer is complete in such a case, or whether the effect is on the desorption of radicals, the work function determines the strength of their bonding, and if one varies the work function by varying the electrode potential, one can vary the reaction rate at the interface. I got the idea. After that, it has been smooth sailing. Dr. Vayenas wrote a seminal article in Modern Aspects of Electrochemistry, Number 29, and brought the field into the public eye. It has since grown and its usefulness in chemical catalytic reactions has been demonstrated and verified worldwide.
Since 1948, this series has bridged the gap between the papers that report and the textbooks that teach in the diverse areas of catalysis research. The editors of and contributors to Advances in Catalysis are dedicated to recording progress in this area. This volume contains cumulative subject and author indexes and tables of contents for volumes 1-42.
This book is a printed edition of the Special Issue "Electrocatalysis in Fuel Cells" that was published in Catalysts
This contributed volume provides a critical review of research in the field of Electrochemical Promotion of Catalysis (EPOC). It presents recent developments during the past decade that have led to a better understanding of the field and towards applications of the EPOC concept. The chapters focus on the implementation of EPOC for developing sinter-resistant catalysts, catalysts for hydrogen production, ammonia production and carbon dioxide valorization. The book also highlights the developments towards electropromoted dispersed catalysts and for self-sustained electrochemical promotion which are currently expanding. This authoritative analysis of EPOC is useful for various scientific communities working at the interface of heterogeneous catalysis, solid state electrochemistry and materials science. It is of particular interest to groups whose research focuses on developments towards a better and more sustainable future.
The different methods for enhancing the catalytic activity of transition metal complexes in hydrocarbon (particularly, alkylarene) oxidations with dioxygen are briefly discussed. The role played by H-bonds in mechanisms of homogeneous catalysis is also analysed. Furthermore, the authors propose a strategy of controlling the catalytic activity of Fe(II,III)(acac)nL2 complexes (L2 = R4NBr or 18C6) by adding H2O to small concentrations. In addition, the activity of Ni, Fe, and Co catalysts in microsteps of chain initiation (O2 activation), and propagation (Cat + RO2?) in the radical chain process of ethylbenzene oxidation is assessed by original method offered by authors. New concepts of mechanism of chain process of hydrocarbon oxidations with dioxygen, catalysed with transition metal complexes, participation of catalysts in microsteps of complicated hydrocarbon oxidation, activity M-O2 (M = Co, Ni, Fe) complexes in different oxidation reactions are briefly stated, and the self-assembled (self-organised) systems mediated by transition metals are briefly considered in connection with increasing research interest in chemical transformations with use of these systems.
This study demonstrates the development of a stable anode for electrochemical oxidation of hydrocarbons in solid oxide fuel cell (SOFC) and a highly active TiO2 based catalyst for photocatalytic reactions. The Ni/YSZ anode of SOFC was modified by Cu electroless plating. The catalytic activity toward H2 and CH4 oxidation were compared by the Faraday resistance (RF) obtained from the impedance spectroscopy. The RF ratio of Cu-Ni/YSZ in CH4 to H2 was greater than that of Ni/YSZ, indicating low catalytic activity of Cu-Ni/YSZ toward CH4 oxidation. The addition of Cu decreased the catalytic activity, but increased stability to 138 h in dry CH4. Characterization of the carbon type with Raman spectroscopy and temperature programmed oxidation showed that Cu formed disordered carbon rather than graphitic carbon which is the precursor to coking. Addition of CO2 to CH4 was studied as another approach to prevent coking. Electrochemical performance and mass spectrometry of the reactor effluent showed that the CH4-CO2 SOFC generated electricity from CO and H2, products of dry reforming reaction, with CO as the major contributor to current generation. CH4-CO2 decreased the activation polarization but showed a limiting current due to the fuel depletion at the interlayer-electrolyte interface. Anode interlayer was modified by reducing the particle size to 2 μm. The fine microstructure increased the three phase boundary length and reduced the activation polarization. The pore loss in the fine microstructure resulted in diffusion limitation and a limiting current in CH4 which was eliminated by adding 4 wt% of pore former at interlayer. Further addition of pore former lowered the performance by creating discontinuity at electrolyte-interlayer interface. The photocatalytic oxidation of ethanol on TiO2 and TiO2 modified with Ag and Au nanoparticles was studied by in-situ IR spectroscopy. Au and Ag increased the surface hydroxyl groups, which further served as active species to oxidize ethanol. Higher rate of electron transfer to Au than to Ag, evidenced by IR spectroscopy, resulted in higher rate of oxidation in Au-TiO2. This resulted in formation of formate (HCOO) on Au-TiO2 and acetate (CH3COO) on Ag-TiO2 as the major intermediate during the initial period of the photocatalytic oxidation.