Ultrafine Fe2C nanocrystals encapsulated in interconnected hollow carbon spheres as ORR electrocatalysts for Alkaline/Neutral Zn- Air batteries

The development of high -performance non -noble metal electrocatalysts for oxygen reduction reaction (ORR) superior to commercial Pt/C in both alkaline and neutral medium is critical for renewable energy technology such as metal -air battery, but remains a great challenge. Herein, hollow spherical framework structure is introduced during the solid -state reaction, enabling the active sites to exist with smaller size and more uniform dispersion. Specifically, a grape -cluster -like ORR catalyst (Fc@Fe -NHCS) is synthesized in which Fe2C nanocrystals and Fe -Nx sites are embedded in carbon layers supported by nitrogen -doped hollow carbon spheres. The resultant Fc@Fe -NHCS exhibits an ORR half -wave potential of 0.85 V in alkaline medium compared to 0.86 V for Pt/C. For neutral ORR, the half -wave potential of Fc@Fe -NHCS is 0.76 V, which is equal to that of Pt/C. Furthermore, Fc@Fe -NHCS demonstrates satisfactory peak power density and open -circuit voltage comparable to Pt/C when utilized as air cathode in self -prepared alkaline and neutral zinc -air batteries (ZABs). The co -action of the spherical framework structure with active sites of Fe2C nanocrystals and Fe -Nx sites ensures excellent ORR electrocatalytic performance, which provides a favorable electrocatalyst for various energy devices including alkaline and neutral ZABs.

Automated summary

The introduction of a hollow spherical framework structure during the solid-state reaction has enabled the synthesis of an excellent ORR catalyst, demonstrating comparable or even superior electrocatalytic performance to commercial Pt/C.