Selection of oxygen reduction catalysts for rechargeable lithium-air batteries-Metal or oxide?

Carbon-supported Pd and PdO nanocatalysts were synthesised using either chemical reduction or thermal synthesis procedures and were used as model metal and oxide catalysts for oxygen reduction in rechargeable lithium-air batteries. The Pd metal catalyst showed excellent initial performance, e.g. a discharge capacity of 855 mAh (g solids)(-1). However, the PdO catalyst displayed superior capacity retention to the Pd catalyst, producing a discharge capacity of 336 mAh (g solids)(-1) after 10 cycles, i.e. the capacity retention was 6% per cycle. The activity and stability of Pd metal and oxide catalysts were found to be closely related to their intrinsic catalytic properties and structural changes during charge/discharge cycles in Li-air batteries. The implication of such a difference is discussed. Model Pd/C and PdO/C catalysts were compared with other widely used carbon-supported metal and oxide catalysts, including Pt/C, Ru/C, RuO2/C and MnO2/C. (C) 2011 Elsevier BM. All rights reserved.