F-doped carbon hollow nanospheres for efficient electrochemical oxygen reduction

Herein, a metal-free catalyst F-CHNS-900 has been prepared through a one-step pyrolysis of polytetrafluoroethylene and ZnCl2 at 900 °C. According to the transmission electron microscope, powder X-ray diffraction, and X-ray photoelectron spectroscopy analysis, F-CHNS-900 has hollow nanosphere structure with rich F atoms doped into the carbon matrix and highly graphitized walls. Owing to its unique structure, F-CHNS-900 catalyst shows excellent ORR performance in 0.1 M KOH with an onset potential of 1.060 V versus reversible hydrogen electrode (RHE), and a half-wave potential of 0.969 V versus RHE, long-time durability, and free of methanol tolerance, superior to Pt/C (20 wt%). Moreover, the ORR property of F-CHNS in acid media is also on a competitive level with Pt/C (20 wt%). Additionally, we also demonstrated the application potential of F-CHNS-900 in Zn-air batteries. This work should be beneficial to designing and preparing new metal-free ORR catalysts with high performance.Graphical abstractA metal-free catalyst with F-doped hollow nanosphere structure has been prepared, which displays an excellent ORR activity and long-time durability in both acidic and alkaline electrolytes.