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Keywords:

  • electrocatalysts;
  • lithium-air;
  • lithium-O2;
  • pyrochlore;
  • oxide catalysts

Abstract

Nano-crystalline mixed metal oxides with an expanded pyrochlore structure are synthesized by a chemical precipitation route in alkaline media. The high concentration of surface active sites afforded by their high surface area, intrinsically variable oxidation state and good electron transport lead to promising electrocatalytic properties for oxygen evolution in Li-O2 cells, yielding rechargeable discharge capacities over 10 000 mAh g−1 and lowering anodic overpotentials significantly. The discharge capacity of the Li-O2 cell is increased further when a small amount of gold is deposited on the pyrochlore oxide, which serves as a more efficient oxygen reduction catalyst. The amount of catalyst necessary for oxygen evolution performance is reduced to as little as 5 wt% by supporting the highly-divided pyrochlore oxide crystallites on carbon using in-situ deposition methods.