In-situ synthesis of atomic Co-N_x sites in Holey Hollow Carbon nanospheres for efficiency Oxygen Reduction Reaction electrocatalyst

Recently, Metal-Organic Frameworks-derived carbide catalysts draw lots of attention because of their low price, abundant reserves and superior stability. However, the metal element tends to form particles at a high temperature still a challenge to achieving high Oxygen Reduction Reaction (ORR) activity. Herein, a kind of Zeolitic imidazolate frameworks (ZIFs) based carbon nanosphere with well-dispersed Co-N_x active sites (Co and N co-doped holey Hollow Carbon nanospheres, hHCS) are prepared by using Polyvinylpyrrolidone as the surfactant to realize the well dispersion of Cobalt. Then KOH activation is used to enlarge specific surfaces area (SSA). In an alkaline medium, the obtained sample shows excellent ORR catalytic performance with a half-ware potential of 0.80 V and a limiting current density of 6.53 mA cm^-2, which are even comparable with that of commercial Pt/C. Further, the simple also exhibits remarkable stability during long-term working and better tolerance of methanol. According to the Density Functional Theory (DFT), the outstanding ORR activity can be ascribed to the favorable dispersed Co-N_x. It can be also attributed to the high SSA, hierarchically pore structure and N-base active sites.