Defective/Doped Graphene-Based Materials as Cathodes for Metal-Air Batteries

Graphene, as a proof-of-concept two-dimensional material, has proven to have excellent physical and chemical properties. Its derivatives, such as defective or doped graphene, are also applied as catalytic materials for metal-air batteries (MABs). MABs have been recognized as possible candidates for new-generation energy storage systems due to their ultra-high theoretical energy density. So far, graphene and its derivatives with optimized structures have been widely explored to improve the electrochemical performance in MABs. Generally speaking, perfect graphene crystalline is inert for many catalytic processes, while defects and heteroatoms can endow graphene with high activity for many electrocatalytic reactions. Under this circumstance, recent progress is summarized for defective/doped graphene as air cathodes in aqueous or organic MABs, which are actually different electrochemical systems with distinct requirements for air cathodes. Also, the relationship is clarified between graphene defects/doping and electrocatalytic mechanisms that can be the guidance for catalyst design. Future directions are also prospected for the development of graphene-based MAB cathodes.