Enhancing oxygen reduction of Fe-N-C active sites onto graphene via bismuth sacrifice for Zn-air batteries

Synthesizing low-cost electrocatalysts with rich metal-nitrogen-carbon active sites for the oxygen reduction reaction (ORR) is critical for developing high-performance Zn-air batteries. However, it is challenging for the pyrolysis cheap molecular precursors (such as melamine and iron salts) is challenging because of the spontaneous aggregation of metal components and undesired byproducts during pyrolysis. Herein, we describe an approach to generate graphene-supported accessible Fe-N-C active sites by introducing a removable bismuth compound that efficiently inhibits the formation of iron-related particles and tubular carbon structures. The graphene-supported Fe(Bi)-N-C electrocatalyst exhibited high ORR activity under both alkaline (E1/2 ~0.916 V) and acidic (E1/2 ~0.784 V) conditions, along with excellent durability (15 mV degradation after 10 k cycles accelerated test). Using the catalytic material as the cathode, the Zn-air battery delivered a high power density of 201.4 mW cm–2 and a high stability over 1000 cycles. This investigation presents a promising controlled pyrolysis solution for the scalable synthesis of low-cost, high-performance metal-nitrogen-carbon-based catalytic materials.