Iron tuning electronic structure of nano-TiN embedded in carbon nanofibers as efficient single-atom catalyst for oxygen reduction reaction

Despite having a similar electronic structure to Pt, TiN exhibits poor catalytic activity for oxygen reduction reaction (ORR). Doping transition metal (M) atoms into TiN can enhance its ORR catalytic activity by creating MNx structures similar to those found in M and N codoped carbon materials. Notably, TiN demonstrates better stability than carbon materials. Herein, a hybrid of M-doped TiN and N-doped carbon nanofibers (M-TiN/NCNFs) was prepared via electrospinning followed by thermal treatment. Among the prepared M-TiN/NCNFs, Fe-TiN/NCNFs exhibited the highest ORR catalytic activity and excellent stability. The FeN5 structure in Fe-TiN/NCNFs was identified as the active site. Density functional theory calculations indicated the moderate interaction between Fe and O (Fe–O bond) is a key factor for the optimal ORR catalytic activity of Fe-TiN/NCNFs. The number of antibonding electrons in molecular orbital of M–O bond can serve as a descriptor for distinguishing the ORR catalytic activities of M-TiN/NCNFs.