Pyridinic-Nitrogen-Dominated Graphene Aerogels with Fe-N-C Coordination for Highly Efficient Oxygen Reduction Reaction

Here, pyridinic nitrogen dominated graphene aerogels with/without iron incorporation (Fe-NG and NG) are prepared via a facile and effective process including freeze-drying of chemically reduced graphene oxide with/without iron precursor and thermal treatment in NH3. A high doping level of nitrogen has been achieved (up to 12.2 at% for NG and 11.3 at% for Fe-NG) with striking enrichment of pyridinic nitrogen (up to 90.4% of the total nitrogen content for NG, and 82.4% for Fe-NG). It is found that the Fe-NG catalysts display a more positive onset potential, higher current density, and better four-electron selectivity for ORR than their counterpart without iron incorporation. The most active Fe-NG exhibits outstanding ORR catalytic activity, high durability, and methanol tolerance ability that are comparable to or even superior to those of the commercial Pt/C catalyst at the same catalyst loading in alkaline environment. The excellent ORR performance can be ascribed to the synergistic effect of pyridinic N and Fe-N (x) sites (where iron probably coordinates with pyridinic N) that serve as active centers for ORR. Our Fe-NG can be developed into cost-effective and durable catalysts as viable replacements of the expensive Pt-based catalysts in practical fuel cell applications.