Redox

About: Redox is a research topic. Over the lifetime, 26853 publications have been published within this topic receiving 862368 citations. The topic is also known as: reduction-oxidation & reduction-oxidation reaction.

Self-catalysis by Catechols and Quinones during Heterogeneous Electron Transfer at Carbon Electrodes

Abstract: Heterogeneous electron transfer kinetics for several catechols were examined on glassy carbon (GC) electrodes in aqueous solution. Electrode preparations yielded GC surfaces with low levels of oxides or adsorbed impurities, which exhibited strong adsorption of dopamine (DA) and related catechols. Conversely, modification of GC with an organic monolayer suppressed DA adsorption and in many cases prevented electron transfer. By relating catechol adsorption to observed electron transfer, it was concluded that an adsorbed layer of catechol acts as an electrocatalyst for solution-phase redox components. Physisorbed or chemisorbed monolayers of several quinones, including duroquinone, anthraquinone, and dopamine itself, are catalytic toward dopamine oxidation and reduction, but nitrophenyl, trifluoromethylphenyl, and methylene blue monolayers severely inhibit electron transfer. The magnitude of inhibition was affected by electrostatic attraction or repulsion between the surface and the redox system, but the maj...

Heme and Nonheme High-Valent Iron and Manganese Oxo Cores in Biological and Abiological Oxidation Reactions

Abstract: Utilization of O2 as an abundant and environmentally benign oxidant is of great interest in the design of bioinspired synthetic catalytic oxidation systems. Metalloenzymes activate O2 by employing earth-abundant metals and exhibit diverse reactivities in oxidation reactions, including epoxidation of olefins, functionalization of alkane C–H bonds, arene hydroxylation, and syn-dihydroxylation of arenes. Metal–oxo species are proposed as reactive intermediates in these reactions. A number of biomimetic metal–oxo complexes have been synthesized in recent years by activating O2 or using artificial oxidants at iron and manganese centers supported on heme or nonheme-type ligand environments. Detailed reactivity studies together with spectroscopy and theory have helped us understand how the reactivities of these metal–oxygen intermediates are controlled by the electronic and steric properties of the metal centers. These studies have provided important insights into biological reactions, which have contributed to ...

Deep oxidation of chlorinated VOCs over CeO2-based transition metal mixed oxide catalysts

Abstract: Cerium-transition metal mixed oxides (4Ce1M, M = V, Cr, Mn, Fe, Co, Ni and Cu) were prepared by coprecipitation method and investigated for deep oxidation of four chlorinated VOCs with quite different molecule structures. 4Ce1M catalysts show mesoporous structures with larger specific surface area and pore volume, and some metal ions can go into the lattice of fluorite, which contributes to improving the stability of the active components. The redox properties of 4Ce1M catalysts are significantly promoted due to the strong interaction between CeO 2 and MO x , which facilitates the destruction of the reactants and byproducts at lower temperature in the process of CVOCs oxidation. Especially, 4Ce1Cr catalyst exhibits the best catalytic activity and selectivity, mainly due to the formation of Cr 6+ species with strong oxidizing ability. 4Ce1Cr also represents good durability for DCE destruction during the 100 h continuous test, and the chemical adsorbed Cl species on the surface can be removed above 325 °C. Moreover, the presence of water or non-chlorinated VOCs can slightly decrease the conversion of chlorinated VOCs at lower temperature due to the competitive adsorption for active sites, while promote at higher temperature (above 300 °C) because of the contribution to removing Cl species away from the surface.

The Kinetic Significance of V5 in n-Butane Oxidation Catalyzed by Vanadium Phosphates

Abstract: Maleic anhydride, a precursor to polyester resins, is made by oxidation of n -butane over vanadium phosphate catalysts. This system is of general interest because it is the only heterogeneously catalyzed, alkane-selective oxidation reaction in commercial use. Time-resolved in situ x-ray absorption spectroscopy shows that when either α I -VOPO 4 /SiO 2 or (VO) 2 P 2 O 7 /SiO 2 catalysts are exposed to n -butane, the rate of maleic anhydride formation is proportional to the rate of decay of V 5+ species in the catalyst. Thus V 5+ species are kinetically significant for the production of maleic anhydride and not just for the production of by-products. The results also suggest that V 5+ species may play a role in the initial hydrogen abstraction from n -butane, the rate-determining step in the reaction sequence. V 4+ sites appear to be responsible for by-product formation.