Iron-nitrogen co-doped carbon nanospheres prepared by template-free melting salt-assisted pyrolysis as efficient and durable oxygen reduction catalysts.

It is necessary to seek oxygen reduction reactions (ORRs) electrocatalyst that can replace commercial Pt/C for new energy conversion devices. Herein, we used molten salt-assisted pyrolysis to successfully convert small nitrogen-containing carbon molecules directly into iron-nitrogen codoped carbon nanospheres (Fe–N–Cs) without the need for external templates. Molten salts provide a solvo-like environment for the high-temperature pyrolysis of small carbon molecules and bulk oxides. Small molecules containing nitrogen and carbon are subjected to spatial domain-limiting effect, reducing volatilization in the calcination processes. Besides, the strong polarity provided by molten salts can not only dissolve bulk oxides but also prevent free metal atoms from gathering again to form particles or clusters. The synthesized Fe–N–Cs exhibit excellent ORR activity. The half wave potential (E 1/2 , 0.67 V vs. RHE) in acidic solution is almost equivalent to Pt/C. Furthermore, Fe–N–Cs have the ability to prevent methanol poisoning and its stability is strong. [Display omitted] • Small molecules containing nitrogen were directly converted into carbon nanospheres. • The Fe–N–Cs was prepared by template-free melting salt-assisted pyrolysis. • The molten salts can provide a high polarity environment. • The Fe–N–Cs showed excellent ORR activity in alkaline and acidic solution. [ABSTRACT FROM AUTHOR]