Mechanistic Understanding of the pH-Dependent Oxygen Reduction Reaction on the Fe–N–C Surface: Linking Surface Charge to Adsorbed Oxygen-Containing Species

cluster near the Fe active center or creating an edge-type Fe-N-C structure can effectively reduce the local charge density around the Fe atom. This reduction hinders the transition of *OH to *O, thereby enhancing ORR activity at a high electrode potential in acidic environments. Our work revealed the underlying explanation of the pH-dependent ORR activity for the Fe-N-C catalyst and sheds light on the future design and synthesis of high-performance Fe-N-C catalysts.