Sharif Digital Repository

NiO-ZnO/TiO2NTs electrodes were synthesized by the electrodeposition of Zn-Ni onto TiO2 nanotubes, dealloying in a concentrated alkaline solution and finally calcination of the resulting Zn(OH)2-Ni(OH)2/TiO2NTs at 300 C. Morphology of the electrodeposited nanostructures was studied using scanning electron microscopy (SEM) while their electrochemical characterizations were carried out using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge procedures. The SEM analysis revealed the nanoporous/cracked structures of the NiO-ZnO/TiO2NTs obtained at the electroplating time of 20 min. The EIS studies showed that nanoporous/cracked structures of... 

The present work describes the preparation and electrochemical characterization of RuO2/MWCNT/Stainless Steel Mesh (SSM) electrode as compared with a MWCNT/SSM electrode in the positive half-cell of a Vanadium Redox Flow Battery (VRFB). The electrochemical characterization of prepared electrode was carried out using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge procedures. The electrochemical activity of MWCNT/SSM modified with RuO2 as positive electrode in a VRFB was notably improved. The RuO2-included electrodes demonstrated high peak current ratio, small peak potential difference and high electron... 

Copper-palladium alloys of different compositions are electrodeposited on nickel from aqueous solutions. These alloys are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The catalytic activity of these alloys toward oxygen reduction reaction (ORR) in alkaline solution is investigated using rotating disk electrode (RDE). The number of electrons transferred per O2 molecule (n) obtained at different potentials is close to 2 at low overpotential indicating HO2- formation and gradually increases to 4 at higher overpotentials indicating full reduction to OH-. It is shown that Cu-Pd alloys are better electrocatalysts than Pd with Pd-Cu-1 having 24.5%... 

The method of unity bond index-quadratic exponential potential has been employed to calculate the heats of adsorption of formic acid and its fragments and the activation energy of the catalytic dehydrogenation of formic acid on Cu85Pd15(110) surface. The active site being a 3-fold site composed of one Pd and two Cu atoms. The calculations based on assuming hydrogen bonding interactions between the adsorbed formic acid and formate species best account for the experimental findings. It is concluded that the rate determining step is the decomposition of formate occurring with an activation energy of 125 kJmol-1, while desorption of the products, CO2 and H2 require activation energies of 20 and... 

The method of unity bond index-quadratic exponential potential (UBI-QEP) has been employed to investigate the energetics of routes to adsorption and decomposition of 1- and 2-propanols on Cu(111) plane. Both the clean and pre-adsorbed oxygen containing surfaces have been considered. A mechanism based on the formation of surface alkoxide groups which become more favored in the presence of adsorbed oxygen and further elimination of β-hydrogen to yield exclusively the corresponding aldehyde/ketone is confirmed on the basis of the energy criteria. The latter process is somewhat hindered in the presence of surface oxygen. The early adsorption of water and the lack of H/D scrambling as reported... 

L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10 -5 to 4.5 × 10 -4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy. Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation, with the poisoning effect of polysulfide ion being more pronounced in the potential range of -0.3 to -0.2 V/SCE. The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were, 10 -3 to 1 × 10 -2 s and 1 × 10 -4 to 1 × 10 -2 s, respectively depending on the potential used for the impedance analysis. Based on the cyclic... 

Cathodically deposited Ag 2Se, to form a 1-μm-thick film, characterized by energy dispersive X-ray analysis and scanning electron microscopy, showed high electro-catalytic activity for l-ascorbic acid oxidation in alkaline solution. The onset of the process was about 80 mV cathodic of that previously observed on Ag under the same conditions and far superior over glassy carbon and Pt. The values of the exchange current density, standard heterogeneous rate constant, and transfer coefficient of the reaction were 1. 65 × 10 -4 A cm -2, 4. 35 × 10 -7 cm s -1, and 0. 60, respectively. Diffusion coefficient of l-ascorbate di-anion was also measured and was around 7. 00 × 10 -6 cm 2 s -1  

Artificial neural networks were used to predict the oxidation peaks potentials of 7 monosaccharides under linear sweep voltammetry regime. Two sets of descriptors, one based on molecular properties calculated through DFT and another based on simple geometric distributions of hydroxyl groups and asymmetric carbon atoms along molecular chains, were employed to introduce the molecules to networks. Relatively, simple networks of (3,3,1) and (3,3,3,1) structures with the number of epochs not exceeding 15 through training process were capable of correctly predicting the peaks positions with R values in the range of 0.97-0.99. © 2008 Elsevier Ltd. All rights reserved  

Adsorption of molecular and atomic oxygen on neutral and negatively charged PdxCu3-x (x=0-3) nano-clusters have been studied by density functional theory. It has been observed that modes and energies of adsorption strongly depend on the charge and composition of the nano-clusters. The most stable adsorption mode for molecular oxygen on neutral Pd/Cu nano-clusters is to bridge Pd-Cu site (adsorption energy=-103.7kJmol-1) while on negatively charged nano-clusters bridging of Pd-Pd or Cu-Cu are more stable adsorption modes (adsorption energies=-140.9 and -172.9kJmol-1). Also, the most stable adsorption mode for atomic oxygen on neutral Pd/Cu nano-clusters is on the hollow site (adsorption... 

Adsorption and dissociation of NO on RhxCu4-x(x = 0–4) nano clusters were investigated using density functional theory. Adsorption energy, total charge on NO, NO bond length, and NO vibrational frequency for various modes of NO adsorption were analyzed. Adsorption from the nitrogen end of NO on the Rh atom(s) of the clusters are more favored and adsorption energies are in the −1.02 eV to −2.59 eV range. NO binds stronger to Rh-Cu mixed clusters compared to pure Cu4 cluster, so N[sbnd]O bond is significantly weakened upon adsorption on the former. NO binding to more atoms of the clusters results in a corresponding decrease of the N[sbnd]O vibrational frequency. Dissociation of NO was also... 

Metallic foams are a class of lightweight materials that show high potentials for different industrial applications such as automotive and aerospace engineering. However, many factors have prevented metallic foams from being fully utilized in industrial applications. One main factor is that the influences of the porous structure on the mechanical properties of metallic foams are not well known yet. In this paper, a finite element model was used to analyze monodisperse closed cell aluminum foam in order to determine the relationship between its elastic modulus, porosity and pore diameter. A nonlinear relationship was found between the foams porosity, pore diameter and modulus of elasticity.... 

Electro-oxidation of methanol on Ni in NaOH solutions with the alkali concentration in the range of 0.05-0.5 M and in the presence of 0.5 M Na 2SO4 supporting electrolyte is studied. All the mentioned species compete for adsorption on Ni and OH- is essential for the electro-oxidation process. The electro-oxidation seems to proceed through the electro-chemical reactions of adsorbed methanol and hydroxide species and the removal of the resulting intermediate by adsorbed hydroxyl groups. The mechanism is consistent with the cyclic voltammetry and impedance spectroscopy results and can semi-quantitatively account for the appearance of capacitive, inductive and negative resistance loops as well...