Boost the Utilization of Dense FeN₄ Sites for High-Performance Proton Exchange Membrane Fuel Cells

Iron-nitrogen-carbon (Fe-N-C) catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) have seriously been hindered by their poor ORR performance of Fe-N-C due to the low active site density (SD) and site utilization. Herein, we reported a melamine-assisted vapor deposition approach to overcome these hindrances. The melamine not only compensates for the loss of nitrogen caused by high-temperature pyrolysis but also effectively etches the carbon substrate, increasing the external surface area and mesoporous porosity of the carbon substrate. These can provide more useful area for subsequent vapor deposition on active sites. The prepared 0.20Mela-FeNC catalyst shows a fourfold higher SD value and site utilization than the FeNC without the treatment of melamine. As a result, 0.20Mela-FeNC catalyst exhibits a high ORR activity with a half-wave potential (E-1/2) of 0.861 V and 12-fold higher ORR mass activity than the FeNC in acidic media. As the cathode in a H-2-O-2 PEMFCs, 0.20Mela-FeNC catalyst demonstrates a high peak power density of 1.30 W cm(-2), outstripping most of the reported Fe-N-C catalysts. The developed melamine-assisted vapor deposition approach for boosting the SD and utilization of Fe-N-C catalysts offers a new insight into high-performance ORR electrocatalysts.