Facile synthesis of PtCo nanoparticles/three-dimensional graphene hybrid material as a highly active and stable electrocatalyst for oxygen reduction reaction

•Ultrathin Co3O4-Pt core–shell nanoparticles were converted into PtCo alloyed nanoparticles with heating treatment in H2/Ar mixture gas.•Mass and specific activity of PtCo @3DG showed 6.8- and 6.2- times higher than those of Pt/C.•Ultrathin size, a high Pt utilization, and a beneficial alloy effect play important roles for the high activity.•3D graphene possesses an open and interconnected porous structure, and conducive to the ORR intermediates transfer process. To further promote the widespread commercialization of proton exchange membrane fuel cells (PEMFCs), high performance oxygen reduction reaction (ORR) catalysts with high activity and stability must be developed to accelerate its sluggish kinetic process. Here, we report a successful synthesis of a novel hybrid material - highly synergistic PtCo nanoparticles (NPs) attached to three-dimensional graphene (PtCo @3DG). The PtCo @3DG exhibits excellent ORR performance, and the mass activity and specific activity measured at 0.9 V vs. RHE were 0.801 A/mgPt and 1.250 mA/cm2 respectively, which are 6.8 and 6.2 times higher than commercial Pt/C. High stability of this new material is achieved, which has demonstrated a loss of only 1.87% after an extensive 10,000 cycles test. The superior performance of PtCo @3DG can be primarily attributed to several key features, including its ultrathin size, a high Pt utilization, and a beneficial alloy effect. Additionally, the 3D graphene possesses an open and interconnected porous structure that facilitates efficient charge and mass transfer, which accelerates the desorption process of intermediates and exposes more active sites.