Developing efficient platinum (Pt)-based electrocatalysts is enormously significant for fuel cells.Herein,we report an integrated electrocatalyst of ultralow-Pt alloy encapsulated into nitrogen-doped nanocar-bon architecture for efficient oxygen reduction reaction.This hybrid Pt-based catalyst achieves a mass activity of 3.46 A mgpt-1 at the potential of 0.9 V vs.RHE with a negligible stability decay after 10,000 cycles.More importantly,this half-cell activity can be expressed at full cell level with a high Pt utilization of 10.22 W mgPt-1 cathode and remarkable durability after 30,000 cycles in single-cell.Experimental and the-oretical investigations reveal that a highly strained Pt structure with an optimal Pt-O binding energy is induced by the incorporation of Co/Ni into Pt lattice,which would account for the improved reaction kinetics.The synergistic catalysis due to nitrogen-doped nanocarbon architecture and active Pt compo-nent is responsible for the enhanced catalytic activity.Meanwhile,the strong metal-support interaction and optimized hydrophilic properties of nanocarbon matrix facilitate efficient mass transport and water management.This work may provide significant insights in designing the low-Pt integrated electrocata-lysts for fuel cells and beyond.