Nonprecious Electrocatalysts for Li-Air and Zn-Air batteries: Fundamentals and recent advances

Over their 150-year history, new twists on metal-air batteries have continued to emerge up to the present day. In this article, we present the fundamentals and recent advances in nonprecious electrocatalysts for metal-air batteries. The catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in lithium (Li)-air and zinc (Zn)-air batteries, including transition-metal oxides, inorganic-organic hybrid materials, and metal-free materials, are summarized. Both aqueous and nonaqueous systems are also considered. We briefly introduce the mechanism and challenges of oxygen electrochemistry and provide a perspective on the design and development of nonprecious electrocatalysts.