Rare-earth-mediated electronic engineering in high entropy alloy catalysts for enhanced performance in rechargeable...

The development of rechargeable zinc-air batteries (ZABs) is fundamentally constrained by the sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which govern the discharge and charge processes, respectively. Although high-entropy alloys (HEAs) offer tunable electronic structures and multi-metal synergy, precisely controlling the adsorption strength of oxygenated species to achieve superior bifunctional activity remains challenging when limited to conventional 3d transition metals. Herein, we report a melamine-assisted pyrolysis strategy to synthesize a series of rare-earth (RE = Ce, Gd, La) integrated FeCoNiMn high-entropy alloy nanoparticles encapsulated within N-doped carbon nanotubes. Among these, the FeCoNiMnCe@NCNTs catalyst demonstrates exceptional bifunctional performance with a half-wave potential of 0.853 V for ORR and an overpotential of 273 mV at 10 mA cm^-2 for OER, yielding a small potential gap (ΔE = 0.65 V). Experimental and theoretical analyses reveal that Ce integration induces favorable electronic structure modulation and enhanced orbital hybridization, which collectively optimize the adsorption free energy of oxygen intermediates and lower the energy barrier of the potential-determining step for both reactions. When applied as an air cathode in ZAB, the catalyst enables a high power density of 188.7 mW cm^-2 and remarkable long-term charge-discharge stability exceeding 325 h. This work highlights the potential of RE-tuned HEAs as robust and efficient bifunctional electrocatalysts for next-generation energy conversion systems.