▎ 摘　　要

The oxygen reduction reaction taking place in the cathode compartment of alkaline exchange membrane fuel cells plays a crucial role in optimizing the electrochemical energy conversion efficiency of the cell. It has therefore become imperative to design electrocatalysts that can efficiently catalyze the electroreduction of oxygen in alkaline media. In this work, palladium nanoparticles were synthesized by using a surfactant-free method and deposited on 3D graphene nanosheets (Pd/3D-GNSs) with morphologies modified by sacrificial templating. The Pd nanoparticles dispersed on the 3D-GNSs have a face-centered cubic crystalline structure with an average particle size of 4-5 nm. By using various surface analysis techniques, it was shown that the porous 3D-GNS supports were highly graphitized and facilitated the dispersion of Pd nanoparticles. By using cyclic voltammetry, it was demonstrated that, relative to Pd nanoparticles supported on commercial carbon black (Vulcan XC-72R), the Pd/3D graphene nanocomposites had increased electrochemically accessible surface areas and significantly higher catalytic activity towards the four-electron reduction of oxygen, with an onset potential closer to theoretical values and minimal hydrogen peroxide yields (3-4%). Overall, the 3D graphene nanosheets significantly enhanced the performance of Pd nanoparticles in alkaline exchange membrane fuel cells by improving their dispersion, increasing the active surface area, and enhancing mass-transport kinetics through its porous 3D morphology.