Active Sites Regulation and Mass Production of a Hierarchically Porous Fe–N–C Catalyst for Zinc–Air Batteries

Although the iron–nitrogen–carbon (Fe–N–C) catalyst has great potential in zinc–air batteries (ZABs), the insufficient performance and low production of the Fe–N–C catalyst are still the key factors that greatly limit the commercial application. In this study, first, a simple dual melt-salt template method is developed to prepare the hierarchically porous HPFe–N–C catalyst with abundant highly stable Fe-pyridinic-N sites. Then, HPFe–N–C and Fe-phenanthroline are mixed and heated for the mass production of THPFe–N–C with rich highly active Fe-pyrrolic-N sites. Under the synergistic effect of the different active sites, THPFe–N–C exhibits better activity and stability of oxygen reduction reaction (ORR) than Pt/C. Density functional theory is utilized to reveal the changing of the free energy for the ORR process of active sites. COMSOL multiphysics simulations are used to prove that the hierarchically porous THPFe–N–C is beneficial to the O2 mass-transfer process. Therefore, THPFe–N–C shows a better discharge performance and peak power density than Pt/C in the ZABs.