And the catalytic mechanisms of other TM atoms embedded graphene with N coordination, such as Zn , Cu , Ni , have also been explored in recent years. In the experimental aspect, many TM-N-C catalysts (TM including Fe, Ni, Zn, Co, etc.) have been practically synthesized and also exhibit promise ORR/OER activity. As Sun et al. developed a highly active Cu-N-C catalyst through the pyrolysis of Cu(NO3)2•3H2O and urea, showing an excellent ORR activity (5.36 mA cm -2 at 0.9V; E1/2 = 0.898V vs RHE). Therefore, these results indicate that the kind of structure of TM-N-C system offers a great opportunity for the practical application of ideal ORR/OER catalysts, and the design of novel catalysts with higher activity and stability need to be challenged continuously.