▎ 摘　　要

Graphene sheets are prepared by subjecting pyrolytic graphite in acetone to liquid exfoliation with sonication. Pyrolytic graphite is synthesized via arc discharge method. Five-layered graphene sheets are obtained through sonication for 12 h. The synthesized graphene sheets are then used as catalysts for hybrid sodium-air cells. The electrocatalytic activity of the exfoliated graphene sheets toward oxygen reduction reaction (ORR) is higher than that of pyrolytic graphite because of numerous edges and efficient electron communication between active edge sites and electrode substrate in the former. The discharge voltage is held constant at 2.48 V versus Na/Na+ for the exfoliated graphene sheets as the catalyst at a current density of 1 mA cm(-2) and room temperature.