▎ 摘　　要

The Sn/SnO/graphene core-shell nanocomposite, comprising of an onion-type architecture of an interior Sn core, a transition SnO layer and an exterior high-defective few-layer graphene, is synthesized by a modified arc-discharge method. The novel triple junction nanostructure exhibits electrocatalytic performance in near four-electron transfer process for the oxygen reduction reaction. The reaction in the heterogeneous catalyst proceeds by the lattice oxygen consumption of SnO, followed by reoxidation of the SnO transition shell. The significant synergetic effects, originated from the sub-nanoscale Sn/SnO/graphene interfacial junctions, not only provide intrinsic activity and the overall conductivity for accelerating the penetration and exchange of ions, electrons and O-2 molecules, but also suppress the chemical/thermal coarsening of Sn/SnO interior cores. The Sn/SnO/ graphene nanocomposite thus has the engineering implications for the interfacial design of heterogeneous catalysts.