▎ 摘　　要

The self-assembly of block copolymer in solution has proven to be an effective strategy for building up a wide range of nanomaterials with diverse structures and applications. This paper reports a facile self-assembly approach towards two-dimensional (2D) sandwich-like mesoporous nitrogen-doped carbon/reduced graphene oxide nanocomposites (denoted as mNC/rGO) with well-defined large mesopores. The strategy involves the synergistic self-assembly of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) spherical micelles, m-phenylenediamine (mPD) monomers and GO in solution and the subsequent carbonization at 900 A degrees C. The resultant mNC/rGO nanosheets have an average pore size of 19 nm, a high specific surface of 812 m(2)center dot g(-1) and a nitrogen content of 2.2 wt%. As an oxygen reduction reaction (ORR) catalyst, the unique structural features render the metal-free nanosheets excellent electrocatalytic performance. In a 0.1 mol center dot L-1 KOH alkaline medium, mNC/rGO exhibits a four-electron transfer pathway with a high half-wave-potential (E (1/2)) of +0.77 V versus reversible hydrogen electrode (RHE) and a limiting current density (J (L)) of 5.2 mA center dot cm(-2), which are well comparable with those of the commercial Pt/C catalysts.