Sharif Digital Repository

The dearth of efficient, robust, and economical electrocatalysts for water oxidation is dubiously the key obstacle for renewable energy devices, so synthesis of efficient, and cost-effective metal-based water oxidation catalysts is vital. Herein, Co3O4, Co9S8 catalysts and their heterostructure Co3O4/Co9S8 were synthesized and evaluated as water oxidation electrocatalysts. The characterization of Co3O4, Co9S8, and Co3O4/Co9S8 electrocatalysts was performed using Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction techniques. The heterostructure Co3O4/Co9S8 (1.46 V) exhibited water oxidation electrocatalysis at extremely low onset potential compared to... 

The aim of this paper was to improve the magnetic properties of magnetoplumbite-type (M-type) strontium hexaferrite substituted with Co 2+-La3+ produced by conventional ceramic forming techniques. The effect on the magnetic properties of varying the composition of the target compound Sr1-xLaxFe12-yCo yO19 and the primary and secondary firing temperatures was investigated. Microstructure studies and XRD phase analysis indicated that optimum values of the remanent magnetization Br and coercive field Hcj were obtained with a primary firing temperature of 1240 C and a final firing temperature of 1180 C, where (x=y)th 1=0.15, (y/x)exp 2=0.75 and the molar ratio of ferric oxide to strontium... 

Nowadays cobalt is mostly produced through the electrowinning process of sulfate solutions. Regarding to the competition between the precipitation of cobalt ions and evolution of hydrogen gas on the cathode surface during the reduction process in a sulfate bath, investigation on the mechanism of metal precipitation is of great importance. In the present work, study on the kinetics of cobalt electrowinning and the mechanism of the involved reactions have been carried out. The obtained results, confirm the mechanism of cobalt precipitation by depletion of hydroxides. The effects of temperature and scan rate parameters were studied on electrowinning of cobalt by cyclic voltammetry technique.... 

The Co-Ni alloy nanowires were electrodeposited into porous anodic aluminum oxide (AAO) templates. At the first, highly ordered AAO templates were synthesized by two-step anodizing of aluminum to increase pore ordering. Arrays of nanowires with diameter about 30 nm and length about 5000 nm were electrodeposited by alternating current. The composition and structure property of nanowires were investigated by EDX, SEM and TEM techniques. It was found that nanowire composition was related to ions concentration in solution and it was shown that at the optimum potential range of electrodeposition (17-19 V), a change at the potential was shown no strong effect on chemical composition of nanowires.... 

A mixture of cobalt(II) and manganese(II) salts of 4-aminobenzoic acid supported on silica gel catalyses the oxidation of thiols to disulfides in the presence of oxygen or air  

A 1:1 molar ratio of the cobalt and manganese salts of p-amino benzoic acid supported on silica gel is an effective catalyst for the oxidation of various organic compounds in reasonable yields using molecular oxygen. The catalyst can be reused several times  

The novel unsymmetrical tetradentate Schiff base complexes of Co(II) and Pd(II) with the general formula M(SaI.Phen.Acac.) and M(Sal.Phen. Naph.), have been synthesised by template and non-template method  

Aromatic and cyclic organic compounds such as nitrobenzene (NB) are widely used in various industries and are present in their wastewater. In addition, the photocatalytic process has received considerable attention due to its lower chemical consumption and more efficient degradation of refractory pollutants. In this study, a CoFe2O4-ZnO (CFZ) composite was prepared and evaluated its efficiency in the degradation of NB from aqueous solution under UV light. The optical, structural, and physicochemical properties of catalysts were characterized using PL, UV–vis DRS, XRD, TEM, FESEM-EDS, and VSM techniques and then discussed in detail. It was found that not only does the use of CF facilitate the... 

Cobalt-based catalysts were prepared on gamma alumina supports, and their behaviour for different Fischer-Tropsch synthesis (FTS) conditions was assessed. Although Co/γ-Al 2O 3 is a well-known FTS catalyst, its durability ought to be improved to make the industrial process economically feasible. The effect of lanthanum doping on the catalyst lifetime was examined utilising reactor tests and catalyst characterization techniques including TPR, ICP and N 2 porosimetry. Reactor test results revealed that an optimum amount of lanthanum improved catalyst activity and selectivity. Increasing amounts of lanthanum doping up to about 1.1wt% seemed to modify the chemical composition of the support... 

The goal of this work is separation and recovery of catalyst residue in wastewater and byproducts of PTA (poly terephetalic acid) unit. Catalyst recovery consists in separating the maximum amount of catalyst and changing the same into valuable compounds. The PTA unit uses cobalt catalyst for oxidation reactions. The byproducts, which contain catalyst, were burned. In the case of metal oxide recovery in the ashes of waste materials, we could solve the problem of the Petrochemical Company. This new method may help us to recover catalyst from wastewater in PTA unit, after which small amounts of ions may be absorbed on a column filled with special absorbent, in such a way that the wastewater... 

A composition of multiwalled carbon nanotube (MWCNT), Nafion and cobalt(II)-5-nitrosalophen (CoNSal) is applied for the modification of carbon-paste electrode (CPE). The pretreated MWCNT is well dispersed in the alcoholic solution of Nafion under the ultrasonic agitation, and the resulted suspension is used as modifier (with 10% w/w) in the matrix of the paste electrode. The prepared electrode further modified by addition of 3 wt% of CoNSal. The resulted modified electrode is used as a sensitive voltammetric sensor for simultaneous determination of uric acid (UA) and ascorbic acid (AA). The electrode showed efficient electrocatalytic activity in lowering the anodic overpotentials and... 

Developing high-performance supercapacitors is of great significance in the area of renewable energies by virtue of having both high energy and power densities. In this work, an innovative strategy is employed for the fabrication of binder-free binary nickel–cobalt-sulfide (NCS) nanosheets (NSs) directly decorated onto the hydrothermal nickel-sulfide (Ni3S2) nanowires (NWs) as the positive electrodes. The NCS/Ni3S2-nickel foam (NF) positive electrodes rendered superior specific capacity of 499.1 mAh.g−1 at 6 A.g−1. Encapsulated iron into the carbon sphere hosts (Fe-HTCSs) are used as the negative counterparts, exhibiting remarkable specific capacitance of 336.6 F.g−1 (at 0.1 A.g−1). The... 

Voltammetric behavior of two mercaptopyrimidine derivatives (2-thiouracil and 2-thiobarbituric acid) has been studied by cyclic voltammetry at a cobalt phthalocyanine (CoPc)-modified carbon-paste electrode. The results of voltammetric determinations showed that the CoPc in the matrix of modified electrode acts as catalyst for electrooxidation of these thiols (RSH), lowering the overpotential of the reaction and significantly increasing the sensitivity for detection of thiols in neutral conditions. The results of voltammetric and polarization measurements in solutions with various pHs were used for prediction of the mechanism of electrocatalytic oxidation at the surface of modified electrode.... 

Electrocatalytic oxidation of penicillamine (PA) at a carbon paste electrode chemically modified with cobalt salophen as a schiff base complex (CoSal) was thoroughly investigated. The results of cyclic voltammetry (CV) and polarization studies were used for the prediction of the mechanism of electrochemical oxidation of PA mediated with CoSal at the surface of a modified electrode. The performance of the modified electrode was compared with those of electrodes modified with cobalt phthalocyanine (CoPc). In comparison, CoSal appears to be considerably more effective as a catalyst for reduction of the overpotential of the anodic oxidation of PA, resulting in a very sharp anodic CV peak at... 

A mixture of cobalt and manganese salts of p-aminobenzoic acid supported on silica gel catalyses the epoxidation of terminal olefins to the corresponding 1,2-epoxy compounds in the presence of oxygen  

The electrochemical oxidation of thiocytosine on the surface of carbon-paste electrode modified with Schiff base (salophen derivatives) complexes of cobalt is studied. The effect of the substituents in the structure of salophen on the catalytic property of the modified electrode is investigated by using cyclic and differential pulse voltammetry. Cobalt (II)-5-nitrosalophen, because of its electrophilic functional groups, leads to a considerable enhancement in the catalytic activity, sensitivity (peak current), and a marked increase in the anodic potential of the modified electrode. The differential pulse voltammetry is applied as a very sensitive method for the detection of thiocytosine. The...