18923-26-7Relevant articles and documents
Supported palladium oxide as a catalyst for oxidation of water
Ravindranathan Thampi,Gratzel
, p. 31 - 39 (1990)
Palladium oxide supported on TiO2, Al2O3, La2O3, Nb2O3 and SiO2 served as water oxidation catalysts. TiO2- and Al2O3-supported catalys
Kinetic Study of the Oxidation of Water by CeIV Ions Mediated by Activated Ruthenium Dioxide Hydrate
Mills, Andrew,McMurray, Neil
, p. 2055 - 2070 (1989)
The results of a kinetic study of the oxidation of water to oxygen by CeIV ions, mediated by thermally activated ruthenium dioxide hydrate (RuO2*yH2O*), are reported.At low 4+>, i.e. ca. 3.45*10-5 mol dm-3, the rate of reduction of CeIV ions (R) was diffusion controlled and depended directly upon 4+> and , but was virtually independent of 3+>.At higher 4+>, i.e. 3.45*10-3 mol dm-3, the kinetics were more complex, with R decreasing with increasing 3+> and decreasing 4+> and .The observed kinetics can be successfully described using an electrochemical model in which the catalyst particles are considered to act as microelectrodes which mediate the transfer of electrons between a Nerstian reaction (the reduction of CeIV ions) and an irreversible reaction (the oxidation of water).Using this model it proved possible to obtain from any 4+> vs. time decay trace a Tafel plot of the variation of current as a function of potential for the oxidation of water on the surface of the particles of RuO2*yH2O*.In addition to providing valuable mechanistic information concerning this reaction, it also allowed the original kinetic traces to be reconstructed and decay curves simulated for a wide range of conditions.From the variation in Tafel plot data as a function of temperature, an activation energy for water oxidation of 52+/-8 kJ mol-1 was obtained.
Cooperative catalysis and critical decomposition distances in water oxidation by tris(ethylenediamine)ruthenium (III) complex confined in a Nafion membrane
Yagi, Masayuki,Kasamastu, Mayumi,Kaneko, Masao
, p. 29 - 35 (2000)
The activity of tris(ethylenediamine)ruthenium (III) complex, [Ru(en)3]3+, as a water oxidation catalyst was studied in a homogeneous aqueous solution and a heterogeneous Nafion (Nf) membrane. In the aqueous solution, the apparent catalytic activity (k(app) (s-1)) decreased monotonously with the concentration due to a bimolecular decomposition of the complex. The bimolecular decomposition of the complex was remarkably suppressed by incorporating it into a Nf membrane. An optimum complex concentration for k(app) in the Nf membrane was exhibited, which was explained both by a cooperative catalysis and a bimolecular decomposition of the complex. The k(app) in the Nf membrane was analyzed in terms of an intrinsic catalytic activity (k(O2) (s-1)) of the complex, a cooperative catalysis distance (r(co) (nm)) and a critical decomposition distance (r(d) (nm)) between them based on intermolecular distance distribution to obtain the k(O2) = 8.5 x 10-5 s-1, r(co) = 1.44 nm and r(d) = 1.07 nm. The results in the [Ru(en)3]3+ system were compared with those obtained in the [Ru(NH3)6]3+ system. (C) 2000 Elsevier Science B.V.
Kinetics of oxidation of nitrogen compounds by cerium(IV)
Doherty, Anne M. M.,Radcliffe, Mark D.,Stedman, Geoffrey
, p. 3311 - 3316 (1999)
The kinetics of oxidation by CeIV in sulfuric acid of hydrazine, hydroxylamine, nitrous acid, hydrazoic acid and of an intermediate involved in the nitrite/hydrazine reaction has been examined under a uniform set of conditions. Reaction proceeds through the free base form of the nitrogen substrate, probably by an inner-sphere mechanism, with a reactivity sequence N2H4 > NH2OH > N3- > NO2-. An intermediate in the hydrazine/nitrous acid reaction, NH2N=NOH, is also oxidised by CeIV in a CeIV/HNO2/N2H5+ system. For the CeIV/HNO/HN3 system there is a much larger consumption of oxidant than can be accounted for by the separate oxidations of nitrite and azide. An additional pathway is proposed, probably involving NNN-O-N=O, formed by combination of azide and nitrogen dioxide radicals. The Royal Society of Chemistry 1999.
Sherill, M. S.,King, C. B.,Spooner, R. C.
, p. 170 - 179 (1943)
Kinetics of manganese(III) acetate in acetic acid: Generation of Mn(III) with Co(III), Ce(IV), and dibromide radicals; reactions of Mn(III) with Mn(II), Co(II), hydrogen bromide, and alkali bromides
Jiao, Xiang-Dong,Espenson, James H.
, p. 1549 - 1554 (2000)
The reaction of cobalt(III) acetate with excess manganese(II) acetate in acetic acid occurs in two stages, since the two forms Co(IIIc) and Co(IIIs) are not rapidly equilibrated and thus react independently. The rate constants at 24.5 °C are k(c) = 37.1 ± 0.6 L mol-1 s-1 and k(s) = 6.8 ± 0.2 L mol-1 s-1 at 24.5 °C in glacial acetic acid. The Mn(III) produced forms a dinuclear complex with the excess of Mn(II). This was studied independently and is characterized by the rate constant (3.43 ± 0.01) x 102 L mol-1 s-1 at 24.5 °C. A similar interaction between Mn(III) and Co(II) is substantially slower, with k = (3.73 ± 0.05) x 10-1 L mol-1 s-1 at 24.5 °C. Mn(II) is also oxidized by Ce(IV), according to the rate law -d[Ce(IV)]/dt = k[Mn(II)]2[Ce(IV)], where k = (6.0 ± 0.2) x 104 L2 mol-2 s-1. The reaction between Mn(II) and HBr2·, believed to be involved in the mechanism by which Mn(III) oxidizes HBr, was studied by laser photolysis; the rate constant is (1.48 ± 0.04) x 108 L mol-1 s-1 at ~23 °C in HOAc. Oxidation of Co(II) by HBr2· has the rate constant (3.0 ± 0.1) x 107 L mol-1 s-1. The oxidation of HBr by Mn(III) is second order with respect to [HBr]; k = (4.10 ± 0.08) x 105 L2 mol-2 s-1 at 4.5 °C in 10% aqueous HOAc. Similar reactions with alkali metal bromides were studied; their rate constants are 17-23 times smaller. This noncomplementary reaction is believed to follow that rate law so that HBr2· and not Br· (higher in Gibbs energy by 0.3 V) can serve as the intermediate. The analysis of the reaction steps then requires that the oxidation of HBr2· to Br2 by Mn(III) be diffusion controlled, which is consistent with the driving force and seemingly minor reorganization.
HBrO2/Ce(4+) Reaction and HBrO2 Disproportionation Measured in Sulfuric Acid Solution at Different Acidities
Foersterling, Horst-Dieter,Varga, Margit
, p. 7932 - 7938 (1993)
The rate of the reaction of bromous acid with Ce(4+), which is responsible for the slowing down of the autocatalytic oxidation of Ce(3+) by bromate in the Belousov-Zhabotinsky reaction, is measured directly by spectroscopic methods in sulfuric acid medium at different acidities.BrO2 radicals are identified as primary reaction products.The rate constant decreases from 40000 M-1 s-1 in 0.3 M H2SO4 to 1000 M-1 s-1 in 3 M H2SO4.The reaction is slowed down upon the addition of NaClO4.The observations are discussed on the assumption that the active cerium species are sulfato complexes with one or two sulfato groups; the equilibrium constants for the complex formation increases with increasing ionic strength leading to smaller concentrations of the active sulfato complexes.Additionally, the disproportionation reaction of HBrO2 was investigated in the same range of acidities.The rate of this reaction increases from 1300 M-1 s-1 in 0.3 M H2SO4 to 12000 M-1 s-1 in 3.0 M H2SO4.We suggest that the rate determining step is a reaction of a protonated with an unprotonated HBrO2.At high acidities the disproportionation reaction is fast enough to compete with the oxidation of HBrO2 by Ce(4+).These results are important for the understanding of the autocatalytic processes in the Belousov-Zhabotinsky reaction, especially at high sulfuric acid concentrations, and for the study of nonbromide-controlled oscillations.
Minero, Claudio,Lorenzi, Eugenio,Pramauro, Edmondo,Pelizzetti, Ezio
, p. 301 - 306 (1984)
A simple, novel method for preparing an effective water oxidation catalyst
Mills, Andrew,Duckmanton, Paul A.,Reglinski, John
, p. 2397 - 2398 (2010)
A novel oxygen catalyst is prepared via the photodeposition of ruthenium(iv) oxide on a titania photocatalyst derived from a perruthenate precursor. The Royal Society of Chemistry.
Moeller, T.,Quinty, G. H.
, p. 1354 - 1355 (1952)
Oxidation of Chloride to Chlorine by CeIV Ions mediated by Different RuIV and IrIV Oxide-based Catalysts
Mills, Andrew,Worsley, David
, p. 3275 - 3284 (1991)
A number of different, characterised, supported and unsupported oxides of RuIV and IrIV have been tested for activity as a chlorine catalyst in the oxidation of brine by CeIV ions.All the different materials tested gave yields of chlorine of > 90percent and first-order kinetics for the reduction of the CeIV ions.The samples prepared by the Adams method were the most active of the materials tested and are typified by high surface areas and appreciable activities per unit area.The kinetics of the catalysed reduction of CeIV ions by brine were studied in detail using an RuIV oxide prepared by the Adams method and supported on TiO2 and the results were rationalised in terms of an electrochemical model in which the rate-determining step is the diffusion-controlled reduction of CeIV ions.In support of this model the measured activation energies for the oxidation of brine by CeIV ions, catalysed by either a supported or unsupported Adams catalyst, were both close (18-21 kJ mol-1) to that expected for a diffusion-controlled reaction (ca. 15 kJ mol-1).
Gersten, Susan W.,Samuels, George J.,Meyer, Thomas J.
, p. 4029 - 4030 (1982)
Sigler, P. B.,Masters, B. J.
, p. 6353 - 6357 (1957)
Growth of spherulitic crystal patterns in a Belousov-Zhabotinski type reaction system
Yadav, Narendra,Srivastava
, p. 1080 - 1087 (2011/07/08)
The growth of spherulitic crystal patterns in a Belousov-Zhabotinski (BZ) type reaction system by using acetyl acetone (AA)-succinic acid (SA) as dual organic substrates has been reported. The reaction system in the liquid phase has been found to show concentric ring-like wave patterns. A colloidal phase composed of numerous fine particles has also been observed during reaction. The solid phase nucleation has been found to occur in the colloidal phase, which leads to the formation of some stable nucleus centers. The solid phase nucleus has been found to grow in symmetric crystal patterns, with the progress of reaction, exhibiting spherulitic morphology. The possible growth behavior of spherulites has also been discussed. The spherulitic structure composed of fine crystal fibrils diverging from a common center have been observed by a scanning electron microscopy (SEM) technique. The polymorphic crystalline phase, found in spherulites has been supported by thermal characterization (TGA/DTA) and X-ray diffraction (XRD) patterns of crystal materials. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2011.
