Metal complex electrocatalysis

Nyokong, T. (2006) Electrodes modified with monomeric M-N< catalysts for the detection of environmentally important molecules, in N4-Macrocyclic Metal Complexes Electrocatalysis,... 

Dodelet J-P (2006) Oxygen reduction in PEM fuel cell conditions heat-treated non-precious metal-N4 macrocycles and beyond. In Zagal JH, Bedioui F, Dodelet JP (eds) N4-macrocyclic metal complexes electrocatalysis,electrophotochemistry biomimetic electroanalysis. Springer, New York, pp 83-147... 

The aim of this overview is first to present the general principles of electrocatalysis by metal complexes, followed by a series of selected examples published over the last 20 years illustrating the major electrochemical reactions catalyzed by metal complexes and their potential applications in synthetic and biomimetic processes, and also in the development of sensory devices. The area of metal complex catalysts in electrochemical reactions was reviewed in 1990.1... 

The thing to be noted here is that the ° values of the 02/ 02" and 02" H202 redox couples are -0.35 and 0.68 V vs Ag/AgCl at pH 7.4 and thus the SODs, for example, Cu, Zn-SOD (Cu (I/II)) with ° = 65mV can mediate both the oxidation of 02 to 02 and the reduction of 02" to H202. Such a bi-directional electromediation (electrocatalysis) by the SOD/SAM electrode is essentially based on the inherent specificity of the SOD enzyme which catalyzes the dismutation of 02 to 02 and H202 via a redox cycle of their metal complex moiety (Scheme 3). 

Electrocatalysis of proton reduction by metal complexes in solution has been widely studied [106-111] and confinement of molecular electrocatalysts for this process in polymeric films has also received some attention [111, 112]. This area has received much impetus from biochemical and structural studies of the iron-only... 

Electrocatalysis, also named lectron-7ransfer-(2hain (ETC) catalysis, whereby a reaction (mostly of non-redox type) is catalyzed by an electron (reduction) or by an electron hole (oxidation). Organotransition-metal complexes can carry an electron or an electron hole and, if they achieve this function without decomposition, they are electron-reservoir complexes [6]. 

Fig. 21. Tentative chemical structures of polymeric transition metal complexes (chelates, 29-33) of potential interest for electrocatalysis...

For example, work in the fuel cell area at the beginning of the sixties has emphasized the interest of mixing small particles of noble metals, such as platinum and palladium, in conducting materials, e.g., carbon powders, in order to promote microheteroge-neous electrocatalysis. Later on, after the development of redox polymers as electrode materials, inclusion of particles into these electrodes has also been performed electrochemically, by the electroreduction of a metal complex ion, such as PtCl , Cu " or Co " in the... 

Earlandite structure, 849 Electrical conductivity metal complexes, 133 tetracyanoplatinates anion-deficient salts, 136 Electrical properties metal complexes, 133-154 Electrocatalysis, 28 Electrochemical cells, 1 Electrochemistry, 1-33 hydrogen or oxygen production from water coordination complex catalysts, 532 mineral processing, 831 reduction, 831 Electrodeposi (ion of metals, 1-15 mineral processing difficulty, 831 Electrodes clay modified, 23 ferrocene modified, 20 nation coated, 15 polymers on, 16 polyvinylferrocene coated, 19 poly(4-vinylpyridine) coated, 17 redox centres, 17 Prussian blue modified, 21 surface modified, 15-31 Electrolysis... 

Electrocatalysis is an important application of electron-induced processes. In electrocatalysis the catalyst has at first to accept chaige(s) from the electrode, and thereafter catalysis can take place. Enzyme-immobilized electrodes are tj ical examples used for various biosensors as well as for investigation of fundamental biocatalysis. The enzymatic active center is often located inside a protein molecule, so that mediation of charges from the electrode surface to the active center is important. Viologens, metallocenes and other metal complexes have been used as such mediators. 

Initial research into the application of PMEs focused on their potential use in electrocatalysis. Much of this work centered on preformed redox polymers containing coordinated electroactive metal complexes because of the synthetic flexibility and the ability to control loading of the electrocatalytic center in the modifying layer. Electrostatic binding of electroactive ions into ionomeric polymer films is a convenient procedure for preparing electrocatalytic layers, although care must be taken to minimize leaching of the electroactive center. ... 

Tatasevich MR, Radyushkina KA, Andruseva SI (1977) Electrocatalysis of oxygen reduction on organic metallic complexes. Bioelectrochem Bioenerg 4 18-29... 

Conductive polymers such as polypyrrole (PPy), polyaniline (PAni), and polythiophen (PTh) have been the subject of much research owing to their wide applications in biosensors, electrochemistry, and electrocatalysis [191, 192]. Recently, conductive polymers have been also investigated as ORR electrocatalysis in three different ways (1) utilizing conductive polymers as ORR electrocatalysts on their own, (2) incorporating non-precious metal complexes into the conductive polymer matrix, and (3) employing conductive polymers as a nitrogen/carbon precursor material for pyrolyzed M-N c/C catalysts [105]. 

Chapters 7-12 focus on the electrocatalysis of carbon-based non-precious metal catalysts. The unique properties and fuel cell applications of various carbon based catalysts are intensively discussed in these chapters. Chapter 7 summarizes the fundamental studies on the electrocatalytic properties of metallomacrocyclic and other non-macrocyclic complexes. Chapter 8 and 9 review the progress made in the past 5 years of pyrolyzed carbon-supported nitrogen-coordinated transition metal complexes. Chapter 10 gives a comprehensive discussion on the role of transitional metals in the ORR electrocatalysts in acidic medium. Chapter 11 introduces modeling tools such as density functional theory (DPT) and ah initio molecular dynamics (AIMD) simulation for chemical reaction studies. It also presents a theoretical point of view of the ORR mechanisms on Pt-based catalysts, non-Pt metal catalysts, and non-precious metal catalysts. Chapter 12 presents an overview on recent progresses in the development of carbon-based metal-free ORR electrocatalysts, as well as the correlation between catalyst structure and their activities. 

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