N-doped carbon nanotube/particle composite as highly efficient electrocatalyst towards oxygen reduction reaction

Optimizing the microstructure is crucial to design the N-doped carbon-based electrocatalysts towards oxygen reduction reaction (ORR). Herein, a 1D/0D composited catalyst (L-Fe-CN-C) is prepared by using graphitic carbon nitride, iron chloride and carbon black as the raw materials. The resultant catalyst is consisted of N-doped carbon nanotubes and nanoparticles. The nanotubes are dramatically shrunk and smaller carbon nanoparticles are simultaneously generated with the pre-addition of carbon black, both contributing to the large specific surface area, high space utilization and to construct a mesopore-dominated microstructure. Moreover, the content of active pyridinic N is increased in the resultant catalyst. Benefiting from the modulation, the catalyst exhibits an excellent ORR activity with 0.850 V of half wave potential, 6.224 mA cm-2 of limited diffusion current density and high selectivity to 4e-path of ORR in 0.1 M KOH. The zinc-air battery with the catalyst on air electrode outputs a high peak power density, high specific capacity and excellent long-term durability, being comparable to those of the benchmark Pt/C based battery. This work provides a rational strategy to controllably synthesize an N-doped carbon ORR catalyst with hierarchical structure and preferable performance.