Towards fuel cell and metal air battery development - part-I The mechanism of oxygen reduction at lanthanum manganate-based perovskite-type oxides in alkaline solution

The eledrocatalysis of oxygen reduction readion by lanthanum strontium manganate (La,, Sr,, MnO,) (LSM), lanthanum calcium manganate (Lao,5 Ca,, MnOd (LCM) and lanthanum barium manganate (La,,Ba,,MnO3 (LBM) has been studied by linear sweep cydic voltammetry using rotating ringdisc electrode technique in alkaline medium. From the ringdisc data and other kinetic parameters it has been assumed that oxygen redudion occurs by dissociative chernisorption at low werpotentials. At higher overpotentials the formation of hydrogen peroxide has been observed on these electrocatalysts. The apparent exchange current density values for oxygen redudion on LSM. LCM and LBM have been found to be 2x lo-', 5x 10-'and 4x 10-~~crnre-s~pe ctively, while the corresponding Talel slopes are 0.100, 0.1 15 and 0.1 15 V per decade. The possible readion mechanism lor eledroiedudion of oxygen on these oxide catalysts has been discussed

The lanthanum barium manganate, la(l-4)Ba2MnO3 - A possible electrocatalyst for oxygen evolution reaction in alkaline medium

Three different non-stoichiometric compositions of lanthanum barium manganate (LBM) have been synthesized and investigated for its possible application as anode catalyst in alkaline water electrolysis. The results of these investigations have shown that LBM is a good electrocatalyst for the oxygen evolution reaction. Of the three oxides examined, La2., Ba2Mn03 has been found to be the best. The above oxide electrodes have been scaled up from 1 cdt o 10 cdi n apparent area. The electrochemical stability over an operation duration of 500 hrs and the resulting time variation effect on the anode potential have been brought out at normal alkaline water electrolysis conditions of 3 KA.m-2 and 80% when a reduction of 0.1 V - 0.15 V in oxygen overpotential has been observed on these catalysts as compared to that of smooth nickel electrodes under identical conditions. The electrocatalytic activity of the oxides has been discussed from the point of view of structural distortion and means for further improvement have been suggested

A study on the formation of luminescent zinc silicate

A study to understand the mechanism of formation of zinc ortho silicate green phosphor has been attempted. Samples with different mole ratios of ZnO and Si02 ranging from 2:l to 0.25:l in steps of 0.25 respectively have been prepared. Characterisation of the samples were done by ernission and excitation spectra and XRD analysis

Kinetics of deposition and dissolution of cobalt using cobalt amalgam

Kinetics of cobalt on cobalt amalgam electrodes are discussed in the present investigation. The preparation of the cobalt amalgam by a simple and insitu method employing rotating platinum based mercury film electrode has been indicated. The amalgam thus prepared was subjected to anodic and cathodic polarization. The linear sweep voltammogram obtained for the reduction of Co(II) ion and the anodic dissolution of cobalt from amalgam electrode in solutions containing different concentrations of sodium sulphamate and sodium chloride at the sweep rate of 0.01 V.s-1 shows one pair of cathodic and one pair of anodic peaks. With increase in concentration of anions, in general, peak height decreases and at the highest concentration, it gets flattened. The peaks are absent in sodium sulphate solution. From the sweep rate dependence, the anodic and cathodic transfer coefficient values are calculated. Probable mechanism for the deposition and dissolution of cobalt from cobalt amalgam electrodes has been suggeste

Electrochemical power source systems based on hydrogen as energy carrier

The state of art of three rechargeable power source system viz. nickel-hydrogen, nickel-metalhydride and regenerative fuel cell is reviewed. The advantages, area of application and performance characteristics are briefly discussed

Sn02:f film properties: effect of electrochemical and mechanical polishing

The effect of electropolishing and mechanical polishing on the transmittance and sheet resistance of Sn02:F films prepared by using two mixed solvent media has been studied. Surface morphology changes recorded by SEM are presented

Molybdenum-titanium composite oxide mediated redox system

The redox nature of the molybdenum-titanium composite oxide coatings formed on titanium base metal prepared by means of a ceramic method has been examined using the cyclic voltammetric technique. The structural investigations were carried out by XRD studie