▎ 摘　　要

The assembly between carbon materials and transition metals has been proved to be a feasible strategy to synthesize electrocatalysts with good activity and stability, especially those with carbon-encapsulated core shell structures that were prepared through multiple processes. Via direct pyrolysis of kelp, we demonstrate in our work the successful synthesis a composite consisting of electrochemically active and graphene-encapsulated cobalt nanoparticles embedded in N, P, S codoped carbon three-dimensional matrix. This biomass-derived electrocatalyst is low-cost and more facile in preparation, and its typical structural features like hierarchical pore structure, high specific area and heteroatom doping enable it to serve as not only a promising cathode material for oxygen reduction reaction (ORR) in fuel cells but also a counter electrode material for triiodide reduction reaction (TIRR) in dye-sensitized solar cells. More importantly, the unique structure of multilayer-graphene-encapsulated cobalt nanoparticles is beneficial to increase contact area, inhibiting the aggregation and dissolution of metal nanoparticles, thus improving the electrocatalytic performance and stability for ORR and TIRR.