▎ 摘　　要

The development of bifunctional catalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is highly desirable for fuel cells and rechargeable metal-air batteries. Till now, it is still challenging to achieve both efficient activities on a single commercial noble-metal catalyst. Recently, N, P co-doped graphene has shown good bifunctional evidence. However, the atomic-scale understanding of the bifunctional mechanism is still lacking. Here, we show that the N and P atoms prefer to bond with each other, forming embedded N-P clusters in graphene. The catalytic performances of the N-P clusters are sensitive to their geometries, especially the N:P ratios. The N:P ratio of similar to 2 is optimal for OER, while similar to 3 is optimal for ORR. Through evaluating the ORR/OER potential gaps, we found that the N-P cluster designated as (NCPC1)-P-2 shows both the high performances of ORR and OER, responsible for the unique bifunctionality in the N, P co-doped graphene.