Composite of Hierarchically Porous N-Doped Carbon/Carbon Nanotube with Greatly Improved Catalytic Performance for Oxygen Reduction Reaction

In this work, a series of catalysts were synthesized by pyrolysis of in situ formed hybrids of metal–organic framework MIL-101(Fe) and polypyrrole (PPy) nanotube followed by acid etching. The obtained catalysts exhibit composite structure of hierarchically porous carbon and carbon nanotube, which endowed the catalysts high surface areas, plenty of active sites and high conductivity, and thus high electrocatalytic performance on oxygen reduction reaction (ORR). The optimum onset and half-wave potential of +17 and −116 mV (vs Ag/AgCl) have been obtained, respectively, which is even 4 and 12 mV positive than commercial Pt/C (20%) in alkaline. The catalyst also exhibits superior long-term stability and durability against methanol. Kinetic investigations have shown that ORR on the catalyst tended to a more effective 4e– dominant transfer process, which makes it a promising nonprecious metal ORR catalyst for fuel cell.