Facile self-assembly N-doped graphene quantum dots/graphene for oxygen reduction reaction

Graphical abstract: Contents Graphic: The FE-TEM image of N-doped graphene quantum dots/graphene sheets (N-GQDs/G) and its structural schematic diagram and electrocatalyzing oxygen reduction reaction. - Highlights: • We successfully prepare inexpensive hybrid of N-GQDs/G by simple two-step hydrothermal progresses. • The N-GQDs act as the effective crosslinker and conductive agent for constructing 3D graphene with large specific surface area. • The N-GQDs/G shows high electrocatalytic performance for ORR (dominating four-electron pathway), long-term stability and resistance to methanol crossover. • The pyridinic-N plays an important role for high electrocatalytic activity. - Abstract: Nitrogen doping carbon nanomaterial has become an important metal-free electrocatalyst for oxygen reduction reaction (ORR) in fue cells. N-doped graphene quantum dots (N-GQDs) are one of the most promising nanomaterials due to abundant electrocatalytic edging and N doping active sites, but low yield, high dispersity and no forming efficient percolative conductive network hinder their direct application as the electrocatalyst. Hydrothermal method is an effective route for preparing high-quality N-GQDs and meanwhile, overcomes the drawbacks of complicated preparing progress and low yield. We further hydrothermally prepare the hybrid material of N-GQDs/Graphene (G) to immobilize N-GQDs on graphene and construct 3D conductive network. Therefore, the inexpensive N-GQDs/G integrates the advantages of rich edges, N doping active sites, high conductivity, and large specific surface area. As confirmed by a series of characterizations and tests, the N-GQDs/G performs high electocatalytic performance (dominating four-electron pathway), long-term stability and resistance to methanol crossover. Moreover, we demonstrate that the type of N specie plays an important role in ORR, especially, the pyridinic-N.