Abstract
Graphene oxide (GO), oxidized unzipped carbon nanotube (O-UCNT), and GO/O-UCNT composites were used as the carbon precursors to synthesize nitrogen-doped graphene (NG), nitrogen-doped unzipped carbon nanotube (NUCNT), and nitrogen-doped graphene/unzipped carbon nanotube (NG-NUCNT) composites. The influence of these carbon precursors on the synthesis of their corresponding nitrogen-doped carbon materials was systematically investigated. The results show that the synthesis of nitrogen-doped carbon materials not only depends upon the structure and composition of their corresponding carbon precursors, but also the morphology and surface property. As for single carbon precursor, the carbon precursor with higher oxygen content tends to make the nitrogen-doped carbon material with higher nitrogen content. Besides, we find that carbon precursor composites with 3D morphology and large specific surface areas contribute to fabricating nitrogen-doped carbon material with sufficient catalytic sites and high nitrogen content. It is the difference of structure, composition, morphology, and surface property for the three carbon precursors that results in the as-prepared 3D NG-NUCNT nework having the most catalytic sites and highest nitrogen content, which further makes the best ORB. performance. Therefore, our results provide good guidance on the synthesis of nitrogen-doped carbon materials with controllable structure and composition and advanced ORR performance.