Nitrogen-Doped Carbon Nanotube-Supported CoNiFe Medium-Entropy Catalysts for High-Performance and Durable Seawater Zinc-Air Batteries

Seawater zinc–air batteries (S-ZABs) are promising for sustainable energy storage and seawater utilization, but their practical application is severely hindered by slow oxygen reduction kinetics and chloride-induced corrosion. Herein, a robust catalyst design strategy inspired by medium-entropy alloys (MEAs) is proposed to address these two key issues simultaneously. A nitrogen-doped carbon nanotube-supported CoNiFe trimetallic catalyst (CoNiFe@N-CNTs) is synthesized, where the multi-element synergy produces abundant M–N x active sites and a dual-protection interface, greatly enhancing oxygen reduction activity and corrosion resistance. The presence of Fe–N x sites and pyridinic N may protect active sites from Cl – erosion, endowing the catalyst with exceptional corrosion resistance. The catalyst shows a half-wave potential of 0.92 V in alkaline seawater with a negligible decay after 100 h. When assembled into S-ZABs, it delivers a peak power density of 198 mW cm –2 and unprecedented long-term stability, operating stably for 2000 h in alkaline freshwater and 1300 h in natural seawater, far exceeding the performance of commercial Pt/C. Density functional theory calculations verify its optimized d-band center, higher electron density near the Fermi level, and stronger Cl – adsorption, supporting its outstanding activity and durability. This work offers a scalable route for durable electrocatalysts in marine energy storage and seawater electrochemistry.