Maximizing the Active Site Densities of Single-Atomic Fe–N–C Electrocatalysts for High-Performance Anion Membrane Fuel Cells

Iron- and nitrogen-doped carbon (Fe–N–C) catalysts have received significant attention owing to their high oxygen reduction reaction (ORR) activities, which are comparable to those of state-of-the-art Pt/C catalysts. This high ORR activity originates from the atomically dispersed Fe coordinated with the nitrogen atom (Fe–Nx) active site. Increasing the Fe–Nx active site density can enhance the ORR activity. In this study, we suggest a facile and effective method for maximizing the active site densities using a simple ZnCl2 activation method. ZnCl2 activation was applied to the metal organic framework-derived Fe–N–C catalyst that exhibits superior ORR activity compared to Pt/C and a recently reported nonprecious metal catalyst. Through various electrochemical analyses, we confirmed that this activity originates from the effectively increased active site density. The anion-exchange membrane fuel cell (AEMFC) performance was measured to confirm practical applicability, and we obtained a significantly high performance of 1076 mA cm–2 at 0.6 V, which is significantly higher than the currently reported performance of carbon-based Fe–N–C AEMFC cathode catalysts. We demonstrate the potential of our strategy for applications in various carbon-based materials that can be used for the development of high-efficiency electrochemical energy devices.