Shape-Controlled Synthesis of Nitrogen-Doped Carbon Encapsulated CoSn Intermetallic Electrocatalyst for Neutral and Alkaline Zinc–Air Batteries

Aqueous rechargeable zinc-air batteries (ZABs) are promising candidates for next-generation sustainable energy storage in the post-lithium-ion battery era. However, suboptimal catalytic activity and structural degradation during prolonged cycles often limit their performance. The development of high-performance ZABs requires durable bifunctional oxygen electrocatalysts. Herein, we report an electrocatalytically active nitrogen-doped carbon-encapsulated CoSn intermetallic catalyst (CoSn@NC), synthesized via a novel shape-controlled approach using a Co-Sn bimetallic charge-transfer complex precursor, for the development of neutral and alkaline ZABs. The surface-engineered CoSn@NC catalyst exhibits exceptional pH-universal oxygen reduction reaction (ORR) activity, enabling a four-electron oxygen reduction to water across a wide pH range. It retains its structural and chemical integrity during the accelerated ORR durability test over 25 000 cycles. The rechargeable ZAB delivers a high peak power density of 282 mW cm^-2 at 463 mA cm^-2 in alkaline electrolyte, and 44 mW cm^-2 at 80 mA cm^-2 in neutral electrolyte. Furthermore, the device shows excellent charge-discharge cycling stability for >99 h in alkaline and 270 h in neutral media, with negligible voltage decay, highlighting the robust bifunctional activity of the catalyst in both environments. The ordered structure and the graphitic carbon encapsulation of the intermetallic contribute to its enhanced activity and durability.