▎ 摘　　要

We synthesize a graphene-wrapped 3D-PtNi nanosponge (G-PtNi NS) using formic acid as a reducing agent and carbon dots as a structure-directing agent at room temperature. Reduced Ni and Pt atoms initiate the exfoliation of carbon dots into graphene dots, which eventually encapsulate the PtNi nanocrystals. The strong Pt-carbon interaction propels the formation of the G-PtNi NS with large specific surface area and good long-term stability. The G-PtNi NS shows high reactivity for an oxygen reduction reaction (ORR). The ORR activity is maintained even after 3000 cycles. We confirm that the graphene layers physically stabilize the PtNi NS and chemically adjust the oxygen affinity of the PtNi NS, which both positively contribute to the ORR performance.