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.

Mechanism of the Electrochemical Reduction of Persulfates and Hydrogen Peroxide

Abstract: Electrochemical studies have shown that the reduction of persulfate and hydrogen peroxide is a two step mechanism, the first step occurs by electron transfer with the conduction band and the second step by hole injection with the valence band. It could be concluded from corresponding measurements performed with a semiconductor electrode that the electrochemical properties of these oxidizing agents have to be described by two instead of one redox (normal) potential. One normal potential is much lower and the other much larger than the theoretical value determined from thermodynamic data. These values are estimated as and .

Oxalate route for promoting activity of manganese oxide catalysts in total VOCs’ oxidation: effect of calcination temperature and preparation method

Abstract: A novel template-free oxalate route was applied to synthesize mesoporous manganese oxides with high surface area (355 m2 g−1) and well-defined mesopores which can be obtained in large quantities. The physicochemical properties of the materials were characterized by means of TG, XRD, SEM, TEM, H2-TPR and XPS techniques. All catalysts were tested on catalytic deep oxidation of benzene, and the effects of calcination temperature on the features of catalyst structure and catalytic activity were investigated. Manganese oxides prepared by oxalate route exhibited better catalytic activities for complete oxidation of benzene, toluene and o-xylene as compared with related manganese oxides prepared by other different methods (NaOH route, NH4HCO3 route and nanocasting strategy), and especially the temperature for benzene conversion of 90% on the oxalate-derived manganese oxide catalysts was 209 °C, which is 132 °C lower than required for the catalyst prepared by NaOH route. The catalytic performance of manganese oxide is correlated with surface area, pore size, low-temperature reducibility and distribution of surface species. The mole ratio of Mn4+/Mn2+ on the samples which performed with better catalytic activity was close to 1.0. This is good for the redox process of Mn4+ ↔ Mn3+ ↔ Mn2+ which is the key factor in determining the activity on MnOx, further indicating that the oxalate route is good for keeping the distribution of manganese oxidation states at an appropriate degree. A possible process of VOCs’ complete oxidation on manganese oxide catalysts is discussed. In addition, the best catalyst was highly stable with prolonged time on stream and was resistant to water vapor.

Electron Transfer Dynamics in Nanocrystalline Titanium Dioxide Solar Cells Sensitized with Ruthenium or Osmium Polypyridyl Complexes

Abstract: The electron transfer dynamics in solar cells that utilize sensitized nanocrystalline titanium dioxide photoelectrodes and the iodide/triiodide redox couple have been studied on a nanosecond time scale. The ruthenium and osmium bipyridyl complexes Ru(H2L‘)2(CN)2, Os(H2L‘)2(CN)2, Ru(H2L‘)2(NCS)2, and Os(H2L‘)2(NCS)2, where H2L‘ is 4,4‘-dicarboxylic acid 2,2‘-bipyridine, inject electrons into the semiconductor with a rate constant >108 s-1. The effects of excitation intensity, temperature, and applied potential on the recombination reaction were analyzed using a second-order kinetics model. The rates of charge recombination decrease with increasing driving force to the oxidized sensitizer, indicating that charge recombination occurs in the Marcus inverted region. The electronic coupling factors between the oxidized sensitizer and the injected electrons in TiO2 and the reorganization energies for the recombination reaction vary significantly for the different metal complexes. The charge recombination rates a...

Intervalence charge transfer (IVCT) in trinuclear and tetranuclear complexes of iron, ruthenium, and osmium.

Abstract: Electron and energy transfer are ubiquitous in biological, chemical, and physical processes, which has led to extensive multidisciplinary research efforts to elucidate the factors influencing mechanistic pathways. Of considerable importance in these studies have been investigations of intramolecular electron and energy transfer within polymetallic assemblies as a result of the diversity (coordination number, ligand environment, stereochemistry, and redox characteristics) provided by the metal centers in such structures. Because of their multicomponent nature, these structures have considerable design potential to exploit the cooperation between the metals and/or other redox-active centers. Novel photochemical molecular devices (PMDs) may be constructed which are capable of performing useful light- and redox-induced functionsincluding artificial photosynthesis and photoinduced energy- and electron-transfer processes in light-harvesting “antenna” systems. Metallosupramolecular assemblies have also been designed to mimic the photoinduced charge separation function in photosynthetic organisms, in an attempt to elucidate the complex electron- and energy-transfer mechanisms which occur in natural systems. The possibility of multiple electron transferby absorption of several photons by linked chromophores, or the design of systems which generate more than one electron upon absorption of one photonhas significant implications in catalytic schemes, as well as understanding long-range electron transfer in biological systems, and the conductivity of “molecular wires”. In molecules involving delocalized unpaired electrons, polarizability may be present so that the species exhibit interesting nonlinear optical or magnetic properties. Polypyridyl complexes of the d^6 metals Fe^II, Ru^II, and OsII have attracted particular attention as the basis of these assemblies due to a combination of favorable photophysical and redox characteristics, the longevity of their excited states, and their chemical inertness in a variety of oxidation states. An important feature of these complexes is the capability of systematic variation of the ground- and excited-state properties by the judicious choice of the coordinating ligands.