Browsing by Author "Elumeeva, Karina"

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    Low Overpotential Water Splitting Using Cobalt-Cobalt Phosphide (Co/Co2 P) Nanoparticles Supported on Nickel Foam
    (ACS Energy Letters, 2016) Masa, Justus; Barwe, Stefan; Andronescu, Corina; Ruff, Adrian; Jayaramulu, Kolleboyina; Elumeeva, Karina
    We report a simple, facile, and safe route for preparation of cobalt–cobalt phosphide (Co/Co2P) nanoparticles and demonstrate their application as efficient low-cost catalysts for electrochemical water splitting. The catalyst achieves good performance in catalyzing both the cathode and anode half-cell water-splitting reactions in 1.0 M KOH and the hydrogen evolution reaction in an acidic electrolyte, 0.5 M H2SO4. For the oxygen evolution reaction in 1.0 M KOH, a current of 10 mA cm–2 was attained at 0.39 V overpotential on a glassy carbon electrode, while an overpotential of 0.19 V was attained at 50 mA cm–2 when the catalyst was supported on nickel foam.
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    Perovskite-based Bifunctional Electrocatalysts for Oxygen Evolution and Oxygen Reduction in Alkaline Electrolytes
    (Electrochimica acta, 2016) Elumeeva, Karina; Masa, Justus; Muhler, Martin; Schuhmann, Wolfgang
    Due to the high cost of precious metal-based electrocatalysts for oxygen reduction and oxygen evolution, the development of alternative low cost and efficient catalysts is of high importance for energy storage and conversion technologies. Although non-precious catalysts that can efficiently catalyze oxygen reduction and oxygen evolution have been developed, electrocatalysts with high bifunctional activity for both oxygen evolution and reduction are needed. Perovskites based on modified lanthanum cobaltite possess significant activity for the oxygen evolution reaction. We describe the synthesis of a bifunctional oxygen electrode with simultaneous activity for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in alkaline media by direct growth of nitrogen-doped carbon nanotubes on the surface of a perovskite containing Co and Fe by means of chemical vapor deposition. The difference in the overvoltage between ORR (at 1mA/cm2) and OER (at 10mA/cm2) was below 880mV in 0.1M KOH. The formation of H2O2 during the ORR was reduced by at least three fold when using the bifunctional catalyst as compared to the non-modified perovskite. Long-term durability tests indicate stable performance for at least 37h during the OER and 23h during the ORR.