▎ 摘　　要

The development of metal-free electrocatalysts with efficient catalytic performance and long-term stability is highly desirable for fuel cell applications. In this study, a solution-processable graphene-based electrocatalyst for the oxygen reduction reaction (ORR) is developed using a facile liquid-phase exfoliation process. An aqueous dispersion of poly(3-hexylthiophene-2,5-diyl) (P3HT) nanoparticles is prepared via a simple miniemulsion process and used as a medium for graphite exfoliation, where the interfacial interaction between P3HT nanoparticles and graphene is utilized to simultaneously stabilize the exfoliated graphene flakes and induce efficient intermolecular charge transfer to accelerate the ORR. Neutron scattering with contrast variation was carried out to study the colloidal architecture of the produced dispersions and the interactions at the interface between graphene and P3HT nanoparticles. The nanoparticlestabilized graphene (G/P3HT) dispersions were employed for printing of flexible conductive circuits (similar to 180 Omega sq-1) and fabrication of metal-free electrocatalyst layers for the ORR, which reduces O2 molecules to OH- ions via the highly efficient four-electron pathway and exhibits superior stability (similar to 97% retention after 10,000 cycles). This printable graphene electrocatalyst provides a breakthrough in green chemistry and advanced techniques for the fabrication of low-cost and sustainable fuel cells.