A Ship-in-a-Bottle strategy to anchor CoFe nanoparticles inside carbon nanowall-assembled frameworks for high-efficiency bifunctional oxygen electrocatalysis

Elaborate design of cost-effective and highly-efficiency bifunctional electrocatalysts towards the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critically essential for the advancement of rechargeable metal-air batteries. Herein, we develop a straightforward and scalable hydrogel-bridged pyrolysis strategy for the exquisite construction of a ship-in-a-bottle-structured bifunctional catalyst consisting of fine CoFe nanoparticles encapsulated inside the carbon nanowall-assembled frameworks (abbreviated as CoFe@N-CNWF hereafter). The deliberate design of such intriguing hierarchical honeycomb-like architecture with tightly confined CoFe nanoparticles and open configuration endows the as-fabricated CoFe@N-CNWF with sufficient well-dispersed active sites, rapid charge transfer efficiency, accelerated mass diffusion and robust mechanical strength. Consequently, the resultant CoFe@N-CNWF catalyst shows outstanding catalytic performance toward the ORR and OER with high activity and long-term stability. More encouragingly, a rechargeable Zn-air battery using CoFe@N-CNWF as the air cathode displays superb energy density, high energy efficiency and robust reversibility, surpassing the state-of-the-art precious Pt/C + RuO2-assembled counterpart. The developed methodology for the fabrication of ship-in-a-bottle architectures may open new opportunities to low-cost, mass production of high-efficiency bifunctional oxygen electrocatalysts for a variety of renewable energy technologies and beyond.

Automated summary

The development of a straightforward and scalable strategy for the fabrication of high-efficiency bifunctional electrocatalysts is crucial for enhancing the performance of rechargeable metal-air batteries. The CoFe@N-CNWF catalyst shows outstanding catalytic performance and long-term stability, making it suitable for various renewable energy technologies.