The study reports a hybrid material of Co3O4 nanocrystals grown on reduced graphene oxide (GO) as a high-performance bifunctional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Despite the low catalytic activity of Co3O4 or GO alone, their hybrid exhibits unexpectedly high ORR activity, which is further enhanced by nitrogen-doping of graphene. The Co3O4/N-doped graphene hybrid shows similar catalytic activity to commercial Pt/C catalysts but superior stability in alkaline solutions. The hybrid also demonstrates high activity for OER, making it a promising non-precious metal-based bi-catalyst for both ORR and OER. The synergistic chemical coupling effects between Co3O4 and graphene are responsible for the enhanced catalytic activity. The hybrid material's performance is comparable to state-of-the-art Pt/C catalysts and outperforms manganese oxide, a previously reported bi-functional catalyst. This work opens a new approach to advanced catalysts for energy conversion and storage.The study reports a hybrid material of Co3O4 nanocrystals grown on reduced graphene oxide (GO) as a high-performance bifunctional catalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Despite the low catalytic activity of Co3O4 or GO alone, their hybrid exhibits unexpectedly high ORR activity, which is further enhanced by nitrogen-doping of graphene. The Co3O4/N-doped graphene hybrid shows similar catalytic activity to commercial Pt/C catalysts but superior stability in alkaline solutions. The hybrid also demonstrates high activity for OER, making it a promising non-precious metal-based bi-catalyst for both ORR and OER. The synergistic chemical coupling effects between Co3O4 and graphene are responsible for the enhanced catalytic activity. The hybrid material's performance is comparable to state-of-the-art Pt/C catalysts and outperforms manganese oxide, a previously reported bi-functional catalyst. This work opens a new approach to advanced catalysts for energy conversion and storage.