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1.
P. Brault C. Dubeau J. -B. Jaillet J. C. Sisi 《Journal of Thermal Analysis and Calorimetry》1974,6(3):361-370
Ulvospinel, having the composition Fe2TiO4, was prepared by heating an intimate mixture of Fe2O3 and TiO2 in a controlled atmosphere of CO2 and H2. The kinetics of its reduction by H2 was studied. The parameters controlling the rate of reduction, such as temperature, granulometry and hydrogen partial pressure were investigated. The optimum temperature range for reduction of the ulvospinel to TiO2 and Fe was established to be between 600° and 800°; above 800° reduction of the TiO2 commenced. 相似文献
2.
A study of TiO system between Ti3O5 and TiO2 at high temperature by means of electrical resistivity
The TiO system between the compositions TiO2 and Ti3O5 has been studied in following the electrical conductivity against the oxygen partial pressure. Several features are discussed : the dependence of electrical conductivity versus oxygen pressure, the kinetics of approach to equilibrium, and reversibility during oxidation and reduction paths. The results suggest an important contribution of point defects for small departures from the composition TiO2 at high temperature. 相似文献
3.
Dr. Dong Zheng Dr. Qiang Wang Dr. Hung‐Sui Lee Dr. Xiao‐Qing Yang Prof. Deyang Qu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(26):8679-8683
Tris(pentafluorophenyl)borane (TPFPB) was found to be an efficient catalyst for rapid superoxide (O2?) disproportionation. The kinetics for the catalytic disproportionation reaction is much faster than the reaction between O2? and propylene carbonate. Therefore, the negative impact of the reaction between the electrolyte and O2? produced by the O2 reduction is minimized. The cathodic current for O2 reduction can be doubled in the presence of TPFPB. The high reduction current resulted from the pseudo two‐electron O2‐reduction reaction due to the replenishment of O2 at the electrode surface. This discovery could lead to a new avenue for the development of high‐capacity, high‐rate, rechargeable Li–air batteries. 相似文献
4.
Tarasevich M. R. Bogdanovskaya V. A. Fridman V. A. Kuznetsova L. N. 《Russian Journal of Electrochemistry》2001,37(1):7-14
The regularities of the bioelectrocatalytic reduction of H2O2 in the presence of peroxidase (POD) or a POD–Nafion composite adsorbed on the surface of carbon black or isotropic pyrocarbon are considered. The effect of the surface coverage with the enzyme, the H2O2 concentration, and the H2O2 supply rate to the electrode on the system activity is studied. Specific activities of three electrode types (POD adsorbed on carbon black or pyrocarbon, and the composite deposited on pyrocarbon) are close to one another. A mechanism for the bioelectrocatalytic reduction of H2O2 in a wide potential range is proposed. At potentials near the steady-state value, the reaction rate is limited by the electrochemical kinetics. At high polarizations, the formation of a POD compound with H2O2 is the limiting stage. 相似文献
5.
M. V. Kryzhanov V. M. Orlov V. V. Sukhorukov 《Russian Journal of Applied Chemistry》2010,83(3):379-383
Results obtained in thermodynamic modeling of the magnesiothermic reduction of niobium and tantalum from pentoxides under
adiabatic conditions are given. The dependences of equilibrium temperature of the reactions on the composition and initial
temperature of the raw material, along with the equilibrium composition, were determined in the systems Nb2O5-Mg-NaCl and Ta2O5-Mg-NaCl in the temperature range 1200–3000 K. 相似文献
6.
Cathodic reduction of oxygen and hydrogen peroxide on amalgamated platinum electrodes, which are coated with monolayers of long-chain aliphatic compounds cetyl alcohol (CA) and stearic acid (SA), is retarded as compared with the same reactions on clean mercury (or amalgam) surface. The oxygen reduction kinetics differ from that on mercury. The difference is explained by that oxygen diffuses into the monolayer and is reduced in it at a certain distance from the metal surface and only at the limiting current the reaction is forced onto the monolayer surface. In contrast to the oxygen reduction, the hydrogen peroxide reduction kinetics on electrodes with SA and CA monolayers is much closer to that on mercury, but with some quantitative distinctions. All results favor the H2O2 reduction at the monolayer/solution interface. The difference in the behavior of O2 and H2O2 is explained by different polarity of these molecules: it is significantly more difficult to penetrate the hydrocarbon monolayer for polar H2O2 molecule than for nonpolar O2 molecule. 相似文献
7.
Eugene A. Kotomin Yuri A. Mastrikov Rotraut Merkle Joachim Maier 《Current Opinion in Electrochemistry》2020
The efficiency of solid oxide fuel cells (SOFC) depends critically on materials, in particular for the cathode where the oxygen reduction reaction (ORR) occurs. Typically, mixed conducting perovskite ABO3-type materials are used for this purpose. The dominating surface terminations are (001) AO and BO2, with the relative fractions depending on materials composition and ambient conditions.Here, results of recent large-scale first principles (ab initio) calculations for the two alternative polar (La,Sr)O and MnO2 (001) terminations of (La,Sr)MnO3 cathode materials are discussed. The surface oxygen vacancy concentration for the (La,Sr)O termination is more than 5 orders of magnitude smaller compared to MnO2, which leads to drastically decreased estimated ORR rates. Thus, it is predicted for prototypical SOFC cathode materials that the BO2 termination largely determines the ORR kinetics, although with Sr surface segregation (long-term degradation) its fraction of the total surface area decreases, which slows down cathode kinetics. 相似文献
8.
Michiel Langerman Dennis G. H. Hetterscheid 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(37):13108-13112
Catalytic pathways for the reduction of dioxygen can either lead to the formation of water or peroxide as the reaction product. We demonstrate that the electrocatalytic reduction of O2 by the pyridylalkylamine copper complex [Cu(tmpa)(L)]2+ in a neutral aqueous solution follows a stepwise 4 e?/4 H+ pathway, in which H2O2 is formed as a detectable intermediate and subsequently reduced to H2O in two separate catalytic reactions. These homogeneous catalytic reactions are shown to be first order in catalyst. Coordination of O2 to CuI was found to be the rate‐determining step in the formation of the peroxide intermediate. Furthermore, electrochemical studies of the reaction kinetics revealed a high turnover frequency of 1.5×105 s?1, the highest reported for any molecular copper catalyst. 相似文献
9.
Studies on Nickel Oxide Mixed Catalysts. XVI. Reduction Behaviour of Amorphous NiO? Al2O3/SiO2 Catalysts The reduction behaviour of NiO? Al2O3/SiO2 catalysts prepared by precipitationdeposition is influenced by the phase composition (amorphous nickel layersilicates and nickel alumino layersilicates, nickel spinels, nickel oxide) and the differences of the composition between surface and bulk. TPR measurements, determinations of the reduction degree, and the nickel particle sizes by static magnetic measurements showed that the reducibility of the NiO? Al2O3/SiO2 catalysts is enhanced and the nickel dispersity is decreased at low Al2O3 contents. The decrease of the reducibility at Al2O3 contents >5 mole% is caused by the formation of nickel spinels and the decrease of the NiII ion surface concentration. 相似文献
10.
M. Pospísil 《Journal of Thermal Analysis and Calorimetry》1995,44(1):133-146
This paper describes a study on some physico-chemical properties of CuO?Bi2O3 mixed oxides of various composition and their reactivity during hydrogen reduction in the range 290–460°C. Depending on the composition, the changes in the morphology of the samples, their specific surface areas, phase composition of Bi2O3 as well as the change in the amount of chemisorbed surface oxygen (specific surface oxidation ability) were found. The last mentioned parameter is strongly affected positively or negatively (depending on the dose absorbed) by the pre-irradiation with gamma-rays and accelerated electrons. Either reduction of CuO or consecutive reduction of both components with a maximum rate on the surface or sub-surface layers of grain, proceed in different temperature ranges. The retarding effect of liquid bismuth is partially compensated for by the sponging and trapping effects, so that the overall reduction rate changes non-monotonously with the composition of the samples. Pre-irradiation leads in all cases to the lowering of reduction rate, which can be correlated with the increase in the concentration of strongly bound oxygen forms, creating centres of donor hydrogen chemisorption. The effect of gamma-radiation appears to be function of the threshold dose absorbed. 相似文献
11.
Jing Xu Qiang Zhang Xin Gao Peifang Wang Huinan Che Chunmei Tang Yanhui Ao 《Angewandte Chemie (International ed. in English)》2023,62(32):e202307018
Piezo-catalytic self-Fenton (PSF) system has been emerging as a promising technique for wastewater treatment, while the competing O2 reductive hydrogen peroxide (H2O2) production and FeIII reduction seriously limited the reaction kinetics. Here, we develop a two-electron water oxidative H2O2 production (WOR−H2O2) coupled with FeIII reduction over a FeIII/BiOIO3 piezo-catalyst for highly efficient PSF. It is found that the presence of FeIII can simultaneously initiate the WOR−H2O2 and reduction of FeIII to FeII, thereby enabling a rapid reaction kinetics towards subsequent Fenton reaction of H2O2/FeII. The FeIII initiating PSF system offers exceptional self-recyclable degradation of pollutants with a degradation rate constant for sulfamethoxazole (SMZ) over 3.5 times as that of the classic FeII-PSF system. This study offers a new perspective for constructing efficient PSF systems and shatters the preconceived notion of FeIII in the Fenton reaction. 相似文献
12.
Prof. Jujun Yuan Haishan He Xiaofan Li Yunfei Gan Meiqi Mu Prof. Huajun Yu Prof. F. Kuang Prof. Xiaokang Li Prof. Xianke Zhang Prof. Jun Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(67):e202202432
Nb2O5 possesses superior fast Li+ storage capability for LIB anodes, benefiting from its fast pseudocapacitive behavior and low volumetric change within the cycling processes. However, the poor electric conductivity for Nb2O5 restricts its reaction kinetics and rate property. Herein, Nb2O5/carbon (C) submicrostructures are fabricated by solvothermal method followed by calcination process. The Nb2O5/C submicrostructures exhibit outstanding rate behavior and cyclic performance (332 (194) mAh g−1 after 1000 cycles at 1 (5) A g−1). The superior electrochemical property is attributed to the distinctive structure for Nb2O5/C submicrostructures, in which Nb2O5 nanoparticles uniformly distributed within Nb2O5/C composite can protect Nb2O5 nanoparticles from agglomeration, and the porous carbon matrix can enhance electron/ion conductivity. This work furnishes a novel strategy for fabricating Nb2O5/C submicrostructures with superior Li+ storage performance, which can be potentially used to design other metal oxide/C submicrostructures for second battery anode. 相似文献
13.
The reduction of cadmium oxide and zinc oxide mixtures of various compositions with hydrogen at 410–450° was studied with thermogravimetry. The reduction kinetics, which depends markedly on the composition in the whole composition range, can be described by the equation (α+0.3)/(1?α)=A·e kt. Preliminary irradiation of the samples with60Coγ-rays (applied doseD γ=105 Gy) causes an increase in the rate of reduction of samples containing an excess of CdO and decrease in the rate of reduction in the region with excess of non-reducible ZnO. Fast neutron irradiation with a flux density of 1.18·1017 n/m2 (total doseD n=4.5·102 Gy) from a252Cf source retards the reduction in the whole range of composition. The probable mechanism of mutual interaction of both components and of the applied ionizing radiation is discussed. 相似文献
14.
The rotating disk electrode technique was used to study in 0.5 M H2SO4 catalytic properties of products of pyrolysis of the metal-free polyacrylonitrile/carbon black composite, polyacrylonitrile/iron/carbon black composite, and also supported pyropolymers of Co(II) tetramethoxyphenyl porphyrine (CoTMPP) and Fe(III) tetramethoxyphenyl porphyrin chloride (FeTMPPCl). It is shown that the metal-free polyacrylonitrile/carbon black composite catalyzes the oxygen reduction reaction via the parallel path. Addition of up to 2% of Fe into the composite results in abrupt growth of the catalytic activity and share of the four-electron reaction, which provides the parallel–serial reaction path. The parallel reaction with no further catalytic conversion of H2O2 occurs on catalysts of the CoTMPP/Vulcan XC72 and FeTMPPCl/Vulcan XC72 series. The chemical composition is one of the key factors affecting activity and selectivity of CoTMPP/Vulcan XC72 catalysts. An increase in the precursor content from 5 to 30% is accompanied by an increase in selectivity k1/k2 from 0.14–0.30 to 0.5–1.7, where k1 is the rate constant of the reaction of O2 reduction to H2O, k2 is the rate constant of the reaction of O2 reduction to H2O2. 相似文献
15.
A strategy for design of bioimprinted proteins with glutathione peroxidase (GPX) activity has been proposed. The proteins imprinted with a glutathione derivative were converted into selenium-containing proteins by chemical modifying the reactive hydroxyl groups of serines followed by sodium hydrogen selenide displacement. These selenium-containing proteins exhibited remarkable GPX activities and the GPX activities of reduction of H2O2 by glutathione (GSH) were found to be 101-817 U μmol−1, which approaches the activity of a selenium-containing catalytic antibody elicited by a hapten similar to our template. The steady state kinetic study for imprinted protein catalysis revealed Michaelis-Menten kinetics for both H2O2 and GSH, e.g. the pesudo-first-order rate constant kcat (H2O2) and the apparent Michaelis constant Km (H2O2) at 1 mM GSH were calculated to be 784 min−1 and 1.24×10−3 M, respectively, and the apparent second-order rate constant kcat (H2O2)/Km (H2O2) was determined to be 6.33×105 (M min)−1. The kinetics and the template inhibition showed that the strategy might be a remarkably efficient one for generating artificial enzyme with GPX activity. 相似文献
16.
C.J. Van Velzen M. Sluyters-Rehbach A.G. Remijnse G.J. Brug J.H. Sluyters 《Journal of Electroanalytical Chemistry》1982,134(1):87-100
Via the combination of data obtained from dc and ac experiments it is shown that, contrary to earlier beliefs, the kinetics of the reaction O2 + 2e + 2 H2O ? H2O2 + 2 OH? do not depend on pH between pH = 6.5 and pH = 12.5. The rate of reduction is obtained in a large potential range that allows proof of the existence of an electrochemical step followed by a chemical step and the determination of the kinetic parameters of these steps.The analyses of the ac data have some novel aspects. 相似文献
17.
J R Totter 《Photochemistry and photobiology》1975,22(5):203-211
Abstract— Kinetic studies were made of light production and 02 absorption elicited by treatment of dimethylbiacridylium hydroxide [D(OH)2] with reducing agents in alkaline aqueous solutions. D(OH)2 addition stimulated O2 uptake which proceeded with zero-order kinetics until nearly all of the O2 or of the D(OH)2 was converted to end products. At the termination of the reactions with fructose as reductant the D(OH)2 was converted to methylacridone and to dimethylbiacridene each compound accounting for approximately one-half the D(OH)2 consumed. O2 was reduced to H2O2. With hydroxylamine as the reducing agent the emitted light intensity was related to the first power of the D(OH)2 concentration and the rate of O2 uptake to the square root of the D(OH)2. The disappearance of D(OH)2 in these circumstances was by a first order or pseudo-first order rate. Fructose as a reducing agent by contrast resulted in an O2 uptake nearly independent of D(OH)2 concentration over a range from 1 × 10-5M-1 × 10-4M, while the light intensity and disappearance of D(OH)2 followed a one-half order rate. O2 uptake was by zero order kinetics and the oxidation of fructose proceeded at the same rate as was found with ferricyanide as oxidant. The kinetics, quantum yields and temperature dependence of the fructose reactions were compared with similar reactions employing H2O2 as the light eliciting reagent. The results are interpreted as indicating that D(OH)2 acts as a chain initiator in a manner analogous to better known, radical producing compounds found to accelerate hydrocarbon autooxidations. 相似文献
18.
Profile measurements of the H2/O2 reaction have been obtained using a variable pressure flow reactor over pressure and temperature ranges of 0.3–15.7 atm and 850–1040 K, respectively. These data span the explosion limit behavior of the system and place significant emphasis on HO2 and H2O2 kinetics. The explosion limits of dilute H2/O2/N2 mixtures extend to higher pressures and temperatures than those previously observed for undiluted H2/O2 mixtures. In addition, the explosion limit data exhibit a marked transition to an extended second limit which runs parallel to the second limit criteria calculated by assuming HO2 formation to be terminating. The experimental data and modeling results show that the extended second limit remains an important boundary in H2/O2 kinetics. Near this limit, small increases in pressure can result in more than a two order of magnitude reduction in reaction rate. At conditions above the extended second limit, the reaction is characterized by an overall activation energy much higher than in the chain explosive regime. The overall data set, consisting primarily of experimentally measured profiles of H2, O2, H2O, and temperature, further expand the data base used for comprehensive mechanism development for the H2/O2 and CO/H2O/O2 systems. Several rate constants recommended in an earlier reaction mechanism have been modified using recently published rate constant data for H + O2 (+ N2) = HO2 (+ N2), HO2 + OH = H2O + O2, and HO2 + HO2 = H2O2 + O2. When these new rate constants are incorporated into the reaction mechanism, model predictions are in very good agreement with the experimental data. ©1999 John Wiley & Sons, Inc. Int J Chem Kinet 31: 113–125, 1999 相似文献
19.
Preparation and Electrochemical Performance of V2O3-C Dual-Layer Coated LiFePO4 by Carbothermic Reduction of V2O5
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The V2O3-C dual-layer coated LiFePO4 cathode materials with excellent rate capability and cycling stability were prepared by carbothermic reduction of V2O5. X-ray powder diffraction, elemental analyzer, high resolution transmission electron microscopy and Raman spectra revealed that the V2O3 phase co-existed with carbon in the coating layer of LiFePO4 particles and the carbon content reduced without graphitization degree changing after the carbothermic reduction of V2O5. The electrochemical measurement results indicated that small amounts of V2O3 improved rate capability and cycling stability at elevated temperature of LiFePO4/C cathode materials. The V2O3-C dual-layer coated LiFePO4 composite with 1wt% vanadium oxide delivered an initial specific capacity of 167 mAh/g at 0.2 C and 129 mAh/g at 5 C as well as excellent cycling stability. Even at elevated temperature of 55 oC, the specific capacity of 151 mAh/g was achieved at 1 C without capacity fading after 100 cycles. 相似文献
20.
Reduction reactivity of CuO-Cr2O3 mixed oxides with hydrogen and the effect of gamma pre-irradiation
《Thermochimica Acta》1987,119(2):261-272
The physico-chemical properties and parameters of CuO-Cr2O3 mixed oxides as well as their reactivity toward reduction with hydrogen have been investigated by means of various methods (X-ray analysis, electron spectroscopy for chemical analysis (ESCA), DTA, IR spectroscopy and scanning electron microscopy). A series of mixed oxides of various compositions in the range 0–100% of each component were prepared by calcinating the mass of coprecipitated basic carbonates in air. The reduction kinetics were studied by isothermal thermogravimetry in the temperature range 180–470 ° C. The effect of the origin of the oxides on the reactivity of the oxide system during its hydrogen reduction was proved by comparing its properties with those of a previously studied series of analogous mixed oxides, which were prepared from different precursors.The pre-irradiation of the system by 60Co γ radiation results in a positive kinetic effect (an increase in the reduction rate) if the lowest dose applied is 2.57 × 106 Gy. The magnitude of the radiation effect is greatly dependent on the composition of the mixed oxides. 相似文献