Heteroengineered Fe ₂ N/CrN <i> _x </i> with Accelerated Proton‐Coupled Electron Transfer for Efficient Oxygen Reduction in Aluminum‐Air Batteries

The sluggish kinetics of the oxygen reduction reaction (ORR) impede the widespread adoption of renewable energy technologies. Here, a heterostructured Fe₂N/CrN_x@NC catalyst is presented, where CrN_x clusters promote H₂O dissociation and, in concert with Fe₂N nanoparticles, optimize oxygen intermediates adsorption within an N-doped carbon matrix. The CrN_x-induced synergy is further confirmed by in situ Raman and infrared spectroscopy, kinetic isotope effect measurements, and theoretical analyses, which collectively reveal that the elaborate Fe₂N-CrN_x interface is pivotal in accelerating proton-coupled electron transfer for ORR. As a result, Fe₂N/CrN_x@NC achieves a half-wave potential of 0.935 V in 0.1 m KOH, exceeding Pt/C. When deployed as the air cathode in aluminum-air batteries, Fe₂N/CrN_x@NC enables a high discharge voltage at 100 mA cm^-2 and an outstanding specific capacity of 2286 mA h g_Al ^-1. This heterostructure engineering strategy, cooperatively manipulating water dissociation and intermediate adsorption, provides a generalized design paradigm for efficient aluminum-air battery cathodes.