A metal and nitrogen doped carbon composites with both oxygen reduction and evolution active sites for rechargeable zinc-air batteries

Rechargeable zinc-air batteries (ZABs) are promising renewable energy storage devices due to their high energy density and preeminent safety. However, they still require highly active and stable oxygen reduction/evolution reactions (ORR/OER) bi-functional catalysts to promote their performance. Here, we report the synthesis of Fe,Ni on N doped carbon sheets supported on N doped carbon nanotubes (Fe,Ni-N-C/N-CNT), which shows ORR activity of half wave potential of 0.879 V and OER activity of 315 mV overpotential at current density of 10 mA cm–2. Using the Fe,Ni-N-C/N-CNT as the air electrode, the fabricated primary ZAB shows a high peak power density of 271 mW cm−2, and the rechargeable ZAB can stability operate for more than 200 h with a high energy efficiency of 61%, surpassed the conventional ZABs using Pt/C-IrO2. We find that the ORR activity related to the Fe-N-C species in the catalysts, while the in-situ generated NiFe2O4 nanoparticles at the OER condition are beneficial for the OER activity. The poly(ethylene imine) used in the synthesis was found important to obtain the high performance catalyst, which helps the binding of the carbon sheets containing the Fe-N-C sites to carbon nanotubes, and also helps the capture of the in-situ generated NiFe2O4 nanoparticles. These results demonstrated the high potential of functionalized carbon composites in the application of rechargeable ZABs.