ABSTRACT
Due to the rechargeable metal-air batteries (RMABs) as the main topic in this book, this chapter 2 introduces the bifunctional mechanisms of catalysis at RMAB air-electrodes in catalyzing both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Depending on the type of electrolytes and metal electrodes, the bifunctional catalysts at air-electrode exhibits different electrochemical reactions and overall products in RMABs. It is demonstrated that the design of advanced bifuncitonal catalysts is importantly related to the improvement of ORR/OER and their durability/stability in RMABs. Also it is emphasized that for advanced composite catalysts, the synergistic effect arising from two or more components is greater than the sum of their individual effects, which can produce a strong physicochemical interaction, resulting in effective charge transfers and/or electronic effects, and thereby improving catalytic performance.
