An ultralow-loading platinum alloy efficient ORR electrocatalyst based on the surface-contracted hollow structure

•Increase Pt utilization by forming open structures with accessible surface.•Increase intrinsic activity by optimizing O-intermediate absorption/desorption.•Enhance electrochemical durability by employing characteristic carbon substrate.•The Pt/p-BN catalyst achieves superior catalytic performance to Com. Pt/C. Reducing the cost of Pt-base ORR electrocatalysts is highly desirable for fuel-cell commercialization. One of the effective strategies is increasing Pt utilization by forming structures with accessible surface. Another is increasing intrinsic activity of Pt sites by redesigning electronic structure. Here, we developed a hollow Pt sphere with a compressive Pt surface on carbonized resorcinol–formaldehyde resin. The special hollow structure with accessible channel endows the nanoparticles with high Pt atom utilization. And the compressive Pt-rich shell gives rise to the enhanced intrinsic activity via tuning Pt d-band electronic structure. As a result, the PtFe(0.9)-C catalysts with an ultralow Pt loading of 0.86% achieved a 2.3 and 2.7 times enhancement in mass activity and specific activity relative to state-of-the-art Pt/C-20% catalysts.