Decoration of Pd Porous Structures on Perovskite Oxides to Improve Li-Air Battery Performance

摘要

Perovskites La_(0.6)Sr_(0.4)CoO_(3-δ) (LSC) and Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF) are still low in the catalytic activity of oxygen reduction reaction (ORR) although it exhibits relatively good catalytic activity for oxygen evolution reaction (OER). In this work, palladium (Pd) was deposited over the LSC surface to improve the ORR activity of the LSC. The Pd decorated perovskite La_(0.6)Sr_(0.4)CoO_(3-δ) (Pd/LSC) was characterized by using various analytic techniques. Pd was deposited on the surface of LSC powders in nanostructured forms without giving a influence on the crystallinity of LSC. The surface area of the Pd/LSC samples dramatically increased over 10 wt% due to the formation of Pd porous structure over the perovskite surface. The electrochemical characterization of the Pd/LSC was examined in both aqueous and non-aqueous electrolyte solutions. In aqueous electrolyte, the Pd/LSC materials exhibited higher ORR and OER activities than LSC and KB. The ORR activity rapidly increased with the increase of Pd wt% deposited in order of 5<10<20<30, though the OER activity displayed not much different values for all the Pd weight percentages. The Pd/LSC materials were applied as air cathode catalyst of lithium air battery to examine their catalytic performances in non-aqueous electrolyte. The highest discharge capacity and the longest cycle life were observed over 30wt% Pd/LSC catalyst. It is concluded that the decoration of Pd over perovskite LSC oxide was more effective to increase the ORR activity, resulting in increasing the performance of lithium air battery.