Synergistically enhanced oxygen reduction electrocatalysis by atomically dispersed and nanoscaled Co species in three-dimensional mesoporous Co, N-codoped carbon nanosheets network

Metal-nitrogen-codoped carbon (M-N-C) nanostructures are promising electrocatalysts for oxygen reduction reaction (ORR). Despite the great progress that has been achieved, synthesizing three-dimensional porous nanoarchitectures derived from Co-N-C nanosheets or related nanohybrids with high content ( > 5 wt%) of exposed single-atom sites remains a challenge. Herein, novel three-dimensional mesoporous Co-N-C nanosheets network enwrapping small amount of Co nanoparticles nanohybrids are fabricated by molten-salt template-assisted pyrolysis of Co-folic acid precursors and chemical etching. In the obtained nanohybrids, the content of single-atom-like Co (SA-Co%) is 7.4 wt% < SA-Co% < 19.4 wt%. Due to the unique mesoporous nanosheets network structure and efficient synergy of atomic and nanoscaled Co species, such nanohybrids manifest enhanced ORR activity with a half-wave potential of 0.85 V, outperforming pure Co-N-C, Pt/C and most of other reported catalysts. Moreover, their stability exceeds that of Pt/C. This work will lead to the optimization of M-N-C nanostructures and accelerate their applications in fuel cells.