Fe/N co-doped carbon materials with controllable structure as highly efficient electrocatalysts for oxygen reduction reaction in Al-air batteries

A novel template-free strategy was developed to synthesize a series of iron and nitrogen co-doped carbon materials (Fe-N-C) with different structures and active sites for oxygen reduction reaction (ORR). These catalysts with well-defined structures not only possess remarkable ORR activity but also provide unique models for probing active sites of Fe-N-C composites. Among these catalysts, the unique Fe-1-N-G consisting of N-doped graphene-like nanosheets, carbon nanotubes and iron-based nanoparticles encapsulated in graphitic carbon layers showed the highest ORR activity with the half-wave potential of similar to 0.86 V, even outperforming the commercial 20 wt% Pt/C. This catalyst also exhibited better durability and discharge performance in practical Al-air batteries than the commercial Pt/C. It is worth noting that the BET surface area of Fe1-N-G is much smaller than that of N-G and Fe-0.1-N-G. The superior electrocatalytic activity should be mainly attributed to the synergistic effect between non-crystalline FeNxCy moieties and the iron-based nanoparticles towards ORR in Fe1-N-G catalyst.