Optimizing Fe-3d Electron Delocalization by Asymmetric Fe–Cu Diatomic Configurations for Efficient Anion Exchange Membrane Fuel Cells

Precisely designing asymmetric diatomic configurations and studying their electronic regulation effect for improving the oxygen reduction reaction (ORR) performance are important for anion exchange membrane fuel cells (AEMFCs). Here, a Fe, Cu co-doped 2D crystalline IISERP-MOF27 nanosheet derived FeN₃O-CuN₄ diatomic site nanocatalyst (named as FeCu-NC) is synthesized for the cathodes of AEMFCs. Thanks to the optimal electronic structure of FeN₃O-CuN₄ in the FeCu-NC catalyst, it shows enhanced half-wave potential (0.910 V), turnover frequency (0.165e s⁻¹ site⁻¹), and decreased activation energy (19.96 kJ mol⁻¹) in KOH. The FeCu-NC-based AEMFC achieves extremely high kinetic current (0.138 A cm⁻² at 0.9 V) and rated power density (1.09 W cm⁻²), surpassing the best-reported transition metal-based cathodes. Density functional theory calculations further demonstrate that the Cu-N₄ can break the localization of Fe-3d orbitals, accelerate the electron transport, and optimize the OH adsorption, thus facilitating the ORR process.