Single-Atom Mn-N₄ Sites Engineered in Carbon Nanofiber Networks for AEMFC Oxygen Reduction

The advancement of catalysts that are both platinum-group-metal (PGM)-free and iron-free is essential for the oxygen reduction reaction (ORR), which is kinetically slow, particularly in anion-exchange membrane fuel cells (AEMFCs). One of the primary obstacles lies in achieving adequate activity and stability within the membrane electrode assembly (MEA) under real-world hydrogen-air operating conditions. Herein, an effective MnN₄ site encased within N-doped carbon nanofibers (denoted as MnN₄@N-CNFs) is designed for efficient ORR electrocatalysis. Benefiting from the electronic structure modulation of MnN₄ moieties through strong interfacial coupling with the carbon matrix, and structural advantages of the 3D hierarchical porosity synergizing with N-doped carbon-MnN₄ coordination systems, the as-resultant MnN₄@N-CNFs demonstrate a high half-wave potential of 0.89 V, outstanding durability, and impressive methanol tolerance under alkaline environments, outperforming commercial Pt/C and a diversity of reported counterparts. Notably, the engineered catalyst demonstrates remarkable fuel cell performance with a peak power density of 222.0 mW cm^-2 during practical AEMFC operation, while maintaining stable operation for over 15 h, representing a 3-fold enhancement over conventional Pt/C-based counterparts. This study establishes fundamental design principles for high-efficiency AEMFCs through atomic-level engineering of precisely coordinated metal-N-C active sites, providing a robust framework for next-generation electrocatalyst development.