“Green” Catalyst for the Oxygen Reduction Reaction in Ecological Metal-Air Systems

Abstract

<p>Thermally treated caffeine doped active carbon (Caffeine-Norit) is studied as a catalyst for the oxygen reduction reaction (ORR) with application in metal-air systems and neutral aqueous electrolytes. Catalytic activity is characterized by polarization curves and Tafel plots and the results are compared with 5% Platinum (5% Pt-Norit) and 4% Silver (4% Ag-Norit) catalysts. The Tafel slopes of all three catalysts are the same, the activity of Ag-Norit being somewhat smaller then both Caffeine-Norit and Pt-Norit. The polarization curves are also comparable, especially in the low current density region. The increase of overpotential for the Caffeine-Norit at current density higher than 50 mA cm<sup>-2</sup> is due to accumulation of H<sub>2</sub>O<sub>2</sub> in the catalyst layer. This was demonstrated by using a simple method for detection of peroxides in neutral electrolytes based on indigo carmine indicator. </p>

Investigation of optical, dielectric properties and conduction mechanism of LiCo 0.7 Mn 0.3 O 2

“…In order to distinguish the contribution of the grains and the grain boundaries, the Maxwell-Wagner equivalent circuit model comprising of a parallel combination of a number of capacitors (C) and resistors (R) is used. As shown in figure (8), the response of the grains is modeled by a parallel combination of a resistance and a fractal capacitance, while that of the grain boundaries is presented by the parallel association of a resistance, capacitance and fractal capacity. The electrode polarization is modeled by a fractal capacitor mounted in series with the two preceding cells.…”

“…Partial replacement of Mn by transition metals with larger potential couplings could lead to an increase in the energy density and discharge plateaus; on the other hand, the presence of toxic and expensive Co ions in LiCoO2 introduces an environmental problem as well as a raise the cost of the (lithium ion battery) LIB. The research work is moving towards the partial or full replacement of Co by more abundant and environmental friendly transition metal ions such as Ni and Mn to enhance the capacity of the cathode [7].Based on these results, several materials of the formula LiCo1-yMnyO2 have been developed and characterized in order to satisfy the needs in electrical and electrochemical properties [8]. In this work, we are studying the structure and morphology of the LiCo0.7Mn0.3O2compound.…”