Journal of Physical and Theoretical Chemistry
Volume:3 Issue: 1, Spring 2006

The electrocatalysis of the oxygen reduction reaction (ORR) on carbon supportedPt-V (1:1) catalyst in polymer electrolyte fuel cells (PEFC) was investigated. Atan oxygen pressure of one atm an enhanced electrocatalytic property of Pt-V/Ccompared with Pt/C is revealed. These results indicate the occurrence of adifferent electrocatalytic mechanism for the ORR on Pt/C and Pt-V/C. Anincrease of mass transport overpotentials is observed for the Pt-V/C catalyst, andthis was related to the presence of vanadium oxide. So the ORR activity of Pt-V/Cat oxygen pressure of one atm is higher than that of Pt/C.

The series of mono-metallic and bi-metallic catalysts have been prepared by impregnatingwith solutions containing compound of H2PtC15,NbC15 and lml HC1 (0.1 mol). The activityand selectivity of the catalysts have been determined under conditions at 450-500°C, 15-30atm. Molar ratio H2/C7H16=5 and VVH=1.5/h for converting n-heptane. Under theseexperimental conditions it has been established that the conversion of n-heptane intobranched aliphatic isomers is catalyzed by a bifunctional mechanism. The results show thatwhen Nb is present, the catalysts are much more stable and have much higher selectivities forisomerization reaction. At a given conversion the bimetallic catalysts produce much lowerconcentrations of cracked products. It is shown that Nb modifies the acidity of the support,resulting to higher selectivity for isomerization and lower selectivity for cracking and alsomodifies the properties of the Pt.

In this paper geometry optimization of two ionic complexes such as Cr042-Gly+1, and Mo042- Gly+I have been carried out at the HF and B3LYP levels oftheory with 6-31G* basis set in the gas phase. Moreover, chemical shift andnatural bond of orbital (NBO) of these compounds have been obtainedusing NMR and NBO methods. Finally, the obtained theoretical results werecompared with each other.

Adsorption of 1-Butanol, Phenol, and P-nitrophenol on activated carbon havebeen studied. The results were used to testifying the validity of different modelsbased on thermodynamic principles: Freundlich, Langmuir and Henry isotherms.The maximum capacity of adsorbent for three compounds was determined, Theconstants of equilibrium were determined by Freundlich isotherm and virialisotherm expression for phenol and 1-butanol, respectively. The thermodynamicfunctions: AG',AS',AH° , were calculated from the data of adsorption of phenol onactivated carbon as a function of temperature. In addition, adsorption of mixturesof phenol and p-nitrophenol under limited range of concentration were studied.Finally arrangement of carbon atoms in activated carbon and surface coverage ofactivated carbon by phenol and 1-butanol for different configurations ofcompounds has been discussed.

The molecular structure of the stable conformation of phosphonic acid in gas phase has beencomputed by employing complete geometry optimization in Density Functional Theory(DFT) methods. The methods used for calculations are B3LYP, BP86 and B3PW91 that havebeen studied in two series of basis sets: D95** and 6-31+G(d,p) for hydrogen and oxygenatoms; LANL2DZ for phosphorus. Bond lengths and angles generally agree with the limitedprior theoretical and experimental values. Phosphonic acid exhibits a minimum-energyconformation in which the acidic hydrogens are oriented toward the phosphoryl oxygen andthe distance from it, nearly 2.7-2.8 A. The conformation of phosphonic acid may bedescribed on the basis dipole-dipole interactions plus relatively small internal hydrogenbonding and steric effect. In contrast to earlier studies, little conformational evidence of"anomeric" effects is found in this compound.

The color removal of three reactive dyes in an aquatic system without priortreatment was studied. Selected commercial dyes were treated with NaC102 andUV as oxidation agents. Effects of nature of oxidant, temperature, pH ofsolutions, concentration of C107—, contact time of C102— and UV irradiation wereinvestigated. Optimal C102— concentration for color removal in the absence of UVirradiation was found to be 20 mg I for all dyes studied. Combination of UVirradiation and C102— was found to be more effective. C102— dosage between 20mg I and UV irradiation (15 watts) for color removal than individual oxidantwith contact time of 30 minutes was required. The accuracy of method waschecked by measuring the COD of the samples. For determination of colorremoval of samples, Spectrophotometery method was used for measurement ofabsorbance changes of the samples (AA).