Browsing by Author "J.F. Koenig"

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Active thin NiCo2O4 film prepared on nickel by spray pyrolysis for oxygen evolution
(1995) S.K. Tiwari; S. Samuel; R.N. Singh; G. Poillerat; J.F. Koenig; P. Chartier
Thin films of NiCo2O4 were prepared on Ni at 370 °C by the method of spray pyrolysis. The films were uniform, adherent, free from cracks and electrocatalytically much more active for oxygen evolution than other NiCo2O4 films recently reported in the literature. This film electrode showed two Tafel slopes ~40 and ~120 mV decade-1 at low and high overpotential, respectively. The second-order observed kinetics in OH- concentration at lower overpotentials changed to first-order at higher overpotentials. A suitable mechanism involving the formation of a physisorbed hydrogen peroxide intermediate in a slow electrochemical step has been suggested. © 1994.
Electrocatalysis of oxygen evolution/reduction on LaNiO3 prepared by a novel malic acid-aided method
(Springer Netherlands, 1998) S.K. Tiwari; J.F. Koenig; G. Poillerat; P. Chartier; R.N. Singh
A kinetic study of the electroformation and electroreduction of oxygen in KOH solutions has been carried out on a LaNiO3 electrode obtained through a malic acid precursor route. The new electrocatalyst was found to show greatly enhanced activity for both oxygen evolution and reduction. The apparent electrocatalytic activity of this electrode for oxygen reduction was more than 10 times higher than those reported for similar electrodes obtained by other methods. It was, however, observed to be less active electrocatalytically for oxygen evolution as compared to the active LaNiO3 electrode obtained by the Bockris-Otagawa coprecipitation method. The electrochemical reaction order with respect to OH- concentration was found to be approximately 1 in the case of oxygen evolution while that for oxygen reduction, was approximately -1. The Tafel slope values for the reactions were ∼2.3 RT/F and ∼2 × 2.3 RT/3F, respectively.