Engineering SmPO4-integrated N, P-doped porous carbon nanosheets for enhanced oxygen reduction in zinc-air batteries

Abstract

Developing cost-effective and high-performance oxygen reduction reaction (ORR) catalysts is essential for advancing rechargeable zinc-air batteries (ZABs). Herein, we report a rationally designed catalyst composed of samarium phosphate nanoparticles uniformly embedded in nitrogen and phosphorus co-doped porous carbon nanosheets (SmPO₄@PN/C). The synergistic integration of SmPO₄ and N, P co-doped carbon not only enhances the electronic conductivity and surface defect density but also ensures strong interfacial interactions through robust POSm covalent bonding, effectively preventing Sm³⁺ leaching. The optimized SmPO₄@PN/C catalyst exhibits outstanding ORR activity with a high onset potential of 1.05 V and a half-wave potential of 0.86 V in alkaline media, along with remarkable long-term electrochemical stability and structural robustness. Even after 48000 s of continuous operation, the catalyst maintains over 87 % of its initial current response. Density functional theory (DFT) calculations demonstrate favorable ORR energetics, supporting the observed catalytic activity and providing mechanistic insights. When employed as the air cathode in ZABs, the SmPO₄@PN/C + RuO₂ hybrid delivers a high peak power density of 133 mW·cm⁻² and maintains superior cycling durability over extended operation, surpassing commercial Pt/C + RuO₂-based systems. This work provides a scalable and efficient strategy for designing rare-earth phosphate-carbon hybrid catalysts and offers a promising pathway toward the development of next-generation metal-air batteries.