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Harald Muckenhuber 《Carbon》2007,45(2):321-329
Commercial carbon black, spark generator soot, Diesel soot from passenger car and high-purity graphite were used for the investigation of the reaction of carbonaceous materials with NO2 applying diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The occurrence of infrared bands was analyzed as they were depending on the reaction temperature. The focus of interest was particularly on the conversion at an elevated temperature of 400 °C. The formation of oxidation products and the adsorption of NO2 on the surface of the samples were observed. Infrared bands could be attributed to C(O)OR, RNO2, and RONO as the main functionalities. The comparison of the results from the different samples revealed that different infrared signals appear when NO2 is adsorbed either on aliphatic or graphitic domains of soot. However, the formation of characteristic bands for an acidic functional group did not occur. This supports the assumption, made in a prior temperature programmed desorption mass spectroscopy (TPD-MS) study, that this group is a transition state.  相似文献   

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The oxidation of carbon nanotubes (CNTs) by hydroxyl radical produced by pulsed O2 plasma in a gas-liquid hybrid discharge reactor was conducted with the goal of enhancing their solubility and improving the yield of H2O2 in electro-Fenton. Data from the characterization experiments showed that oxygen bearing groups (COH, COO, COOH, CO) were formed on the surface of CNTs. The possible mechanism indicated that introduction of oxygen bearing groups onto CNTs could be attributed to the attacks by hydroxyl radical. The oxidized CNTs were easily dispersed in ethanol. The H2O2 yield on the original CNTs was 102 mg/L at −0.85 V after 90 min; in contrast, H2O2 yield on CNTs-15 reached 146 mg/L under the same conditions, resulting from the enhancement of the accessibility of O2 on CNTs. In the electro-Fenton, the removal of methyl orange on the original CNTs was around 40%, and it increased to 95% on CNTs-15.  相似文献   

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Electrochemical oxidation of Inosine has been studied in the phosphate buffers of pH range 3.3-10.9 at pyrolytic graphite electrode. In the entire pH range a single well-defined oxidation peak (Ia) was observed, when the sweep was initiated in the positive direction. In the reverse sweep no cathodic peak was obtained. The peak potential of the oxidation peak was dependent on pH and shifted to less positive potential with increase in pH. The kinetics of the UV absorbing intermediate was followed spectrophotometrically and the decay occurred in a pseudo first order reaction having k values in the range 0.50-0.92 × 10−3 s−1 in the entire pH range studied. The value of n was found to be 2.95 ± 0.3. The products of oxidation were silylated and characterized by using GC-Mass. Two tetramers having CC, CN, NN, CON and COOC linkages were identified. A plausible mechanism for the electrooxidation of Inosine has been suggested.  相似文献   

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Quantum chemical calculations were performed on azacyclo C5 to C14 amines, open chain C6 to C14 amines and phenylazacyclo C5 to C14 amines. Inspection of the calculated parameters and corrosion inhibition efficiencies were made to observe any clear links, which might exist between the two. Possible correlations between experimental inhibition efficiencies and parameters such as dipole moment (μ), highest occupied (EHOMO) and lowest unoccupied (ELUMO) molecular orbitals and the differences between them, HOMO-LUMO gap (Δ), as well as some structural characteristics were investigated. The models of the inhibitors were optimized with the Modified Neglect of Diatomic Overlap (MNDO) method. The Quantitative Structure Activity Relationship (QSAR) approach has been used and a composite index of some quantum chemical parameters were constructed in order to characterize the inhibition performance of the tested molecules. The inhibition effect of polymethylene amines is closely related to orbital energies and/or energy gap and dipole moment.  相似文献   

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Xiaowei Li 《Electrochimica acta》2008,53(22):6662-6667
Carbon-supported PdCo alloy electrocatalysts of different Pd/Co atomic ratios were simply prepared in an aqueous solution at room temperature with NH4F as a complexing agent and H3BO3 as a buffer, followed by NaBH4 reduction. As-prepared PdCo bimetallic nanoparticles show a single-phase face-centered-cubic (fcc) disordered structure, and the mean particle size is found to decrease with increase in Co content. TEM images demonstrated that the as-prepared PdCo alloy nanoparticles are well dispersed on the surface of the carbon support with a small particle size and a relatively narrow particle size distribution. For example, the average particle size of a Pd2Co1/C catalyst is ca. 3.0 nm, which is much smaller than that of the PdCo/C bimetallic nanoparticles reported by others. An activity evaluation of the oxygen reduction reaction (ORR) on as-prepared PdCo/C catalysts with a rotating disk electrode (RDE) technique indicated that the maximum ORR mass activity was observed for a Pd:Co atomic ratio of 4:1, but the highest specific activity was found on a Pd:Co atomic ratio of 2:1. Kinetic analysis reveals that the ORR on PdCo/C catalysts follows a four-electron process leading to water. Moreover, the PdCo/C catalyst exhibited much higher methanol tolerance during the ORR than the Pt/C catalyst, assessing that it may function as a methanol-tolerant cathode catalyst in a direct methanol fuel cell (DMFC).  相似文献   

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S. Rosini 《Electrochimica acta》2005,50(14):2943-2953
The potentiometric response of three different platinum gas diffusion electrodes deposited on H3PO4 doped polybenzimidazole (PBI) was investigated under humidified atmospheres that contained H2 or mixtures of H2 and O2. Continuum modelling was used to analyse the response. It is shown that the non-Nernstian response under H2H2ON2 mixtures can be explained by a difference of water activity on both sides of the membrane. Under H2O2N2 mixtures, the oxygen mass transport parameters have a strong effect on the electrode sensitivity.  相似文献   

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