Carbon composites from iron-chelating pyridine nitrogen-rich coordinated nanosheets for oxygen reduction

The exploration of a noble-metal-free and nitrogen-doped carbon (M–N/C) composite electrocatalyst for the oxygen reduction reaction (ORR) remains a great challenge. The activities of the M–N/C composite electrocatalysts are mainly affected by the metal active sites, pyridinic nitrogen, and graphitic nitrogen. In the present work, the iron-coordinated self-assembly is proposed for the preparation of iron-chelating pyridine nitrogen-rich coordinated nanosheet (IPNCN) composites as electrocatalysts. Due to the highly conjugated structure of the IPNCN precursor, the pyridine nitrogen elements at both ends of the tetrapyrido [3,2-a:2',3'-c:3'',2''-h:2''',3'''-j] phenazine (TP) provide the multiple ligands, and the coordination interactions between the irons and the pyridine nitrogen further improve the thermodynamic stability, where the metal active sites and nitrogen elements are uniformly distributed in the whole structure. The resultant IPNCN composites exhibit excellent ORR performance with an onset potential of 0.93 V and a half potential of 0.84 V. Furthermore, the IPNCN composite electrocatalysts show the higher methanol resistance and electrochemical durability than the commercial Pt/C catalysts. It could be convinced that the as-designed IPNCN composite catalysts would be a promising alternative to the noble metal Pt-based catalysts in the practical applications.