Enhanced oxygen reduction reaction on La-Fe bimetal in porous N-doped carbon dodecahedra with CNTs wrapping

The oxygen reduction reaction (ORR) is a crucial process in Zn-air systems, and the catalyst plays a significant role in this reaction. However, reported catalysts often suffer from poor durability and stability during the ORR process. Herein, we synthesized La-Fe bimetallic nanoparticles encapsulated in a N-doped porous carbon dodecahedron (La-Fe/NC) originated from ZIF-8 by a simple direct carbonization. The La-Fe/NC catalyst had a numerous mesopores and dendritic outer layer generated by carbon nanotubes (CNTs), forming a high conductivity network that helped to optimize electron transfer and mass transport in the ORR process. The effect of different doping transition metals and metal ratios on the ORR activity of Zn-air batteries was investigated. In alkaline media, the La-Fe/NC showed the highest ORR catalytic activity, with a half-wave potential (E1/2) of 0.879 V (vs. RHE, Pt/C 0.845 V). After 5000 cycles, the E1/2 of the La-Fe/NC catalyst only decreased by 7 mV, and its performance in stability tests and methanol tolerance tests was superior to Pt/C. When used as the air electrode in a Zn-air battery, the La-Fe/NC catalyst demonstrated an excellent specific capacity of 755 mAh/g and a peak power density of 179.8 mW/cm2. The results provide important insights for the development of high-performance Zn-air batteries and new directions for the design of ORR catalysts.