▎ 摘　　要

Constructing ultrafine and highly dispersive palladium nanoparticles on 3-dimentional hierarchically porous carbon matrix is of great significance to develop high-performance and cost-effective electrocatalysts for fuel cell systems. Herein, a facile and stabilizer-free strategy was exploited to decorate of ultrafine and well-dispersive Pd nanoparticles (similar to 2.8 nm) on mesocellular graphene network (MGN) that was templated by zeolite MCM-22. It was found that optimal oxygen defects in MGN templated by zeolite framework Al sites were contributed to the ultrafine structure. The as-prepared Pd/MGN not only inherited the nanosheet structure of zeolite MCM-22 with hierarchical pores, large surface area and high conductivity, but also exhibited plentiful and accessible catalytic active sites. In comparison with the commercial platinum-carbon (Pt/C) catalyst (20 wt %), Pd/MGN demonstrated lower onset potential (positive shift 9 mV), significantly enhanced mass activity (up to 3.6 fold) and much longer durability for cathodic oxygen reduction reaction. It is believed that this work promises a straightforward method to develop carbon-supported ultrafine nanoparticles for low-cost and highly efficient catalytic applications.