Sharif Digital Repository

Nanoporous/cracked structures of cobalt oxide (Co3O4) electrodes were successfully fabricated by electroplating of zinc–cobalt onto previously formed TiO2 nanotubes by anodizing of titanium, leaching of zinc in a concentrated alkaline solution and followed by drying and annealing at 400 °C. The structure and morphology of the obtained Co3O4 electrodes were characterized by X-ray diffraction, EDX analysis and scanning electron microscopy. The results showed that the obtained Co3O4 electrodes were composed of the nanoporous/cracked structures with an average pore size of about 100 nm. The electrochemical capacitive behaviors of the nanoporous Co3O4 electrodes were investigated by cyclic... 

RGO/TiO2NTs/Ti electrodes with high surface area and good capacitive characteristics were prepared by simple electrochemical reduction of graphene oxide (GO) onto the previously formed TiO2 nanotubes. Microstructure studies show that reduced graphene oxide (RGO) having high surface area has been deposited onto the TiO2NT arrays. The electrochemical capacitive behaviors of the obtained electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge–discharge studies, and electrochemical impedance spectroscopy (EIS) in 1 M H2SO4 solution. The electrochemical data demonstrated that the electrodes displayed specific capacitance of 410 F g−1 at the current density of 50 A g−1 and... 

In this study, rhodium-copper alloys of different compositions are electrodeposited on graphite electrode from aqueous solutions. The bulk compositions of these alloys are determined using energy dispersive X-ray analysis and surface morphologies are investigated by scanning electron microscopy. The catalytic performance of these alloys in oxygen reduction reaction (ORR) in alkaline media is investigated by linear sweep voltammetry on rotating disk electrode assembly. The number of electrons transferred per O 2 molecule (n) obtained at different potentials is four indicating full reduction of oxygen to hydroxide ion. It is shown that Rh-Cu alloys are better electrocatalysts than Rh with... 

PANI/Pd/TiO2NTs electrodes with highly porous structures and good capacitive characteristics were prepared by electrodeposition of polyaniline on palladium nanoparticles loaded TiO2 nanotubes. The loading of small palladium nanoparticles was carried out by sonochemical reduction of Pd+2 onto TiO2NTs and affected the ordered growth of PANI, reducing the charge transfer resistance and increasing surface area of PANI. The specific capacitance and the stability of electrode showed improvements. The results illustrated that the specific capacitance of these electrodes was around 1060 F g-1 in 1.0 M H2SO4 electrolyte as measured at a constant current of 2.0 A g-1, whereas it was 210 F g-1 for the... 

Layers of cobalt and manganese oxides were co-deposited or deposited on top of each other or next to each other by potentiostatic method onto stainless steel substrate. Deposition potentials of 1 and -1 V for the anodic and cathodic depositions were employed. Specific capacitance values in the range of 38.5-78 F g -1 were found with cobalt oxide on top of manganese oxide having the lowest and manganese oxide on top of cobalt oxide having the highest capacitances. The usefulness of the electrodes was characterized by cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy in 2 M NaOH electrolyte for redox supercapacitor applications. The latter presented the... 

The pseudocapacitance and morphology of electrodeposited transition metal oxides depend significantly on the morphology of the substrate. The nanoporous nickel substrate, derived from selective electro-dissolution of antimony from an electro-deposited Ni-Sb alloy, effectively promotes the electrochemical utilization of manganese oxide deposited on this structure. The large electronic and ionic conduction within the nanostructured deposit improve the energy storage performance of Mn oxide as compared to that on flat Ni substrate. In this work, the MnO2 specific capacitances of around 612 F g-1 were obtained, which was five times higher than Mn oxide deposited on a flat Ni-ribbon. A highly... 

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...