Preparation and properties of transition metal nitrides caged in N-doped hollow porous carbon sphere for oxygen reduction reaction

A series of transition metal nitrides (MxNy, M=Fe, Co, Ni) nanoparticle (NP) composites caged in N-doped hollow porous carbon sphere (NHPCS) were prepared by impregnation and heat treatment methods. These composites combine the high catalytic activity of nitrides and the high-efficiency mass transfer characteristics of NHPCS. The oxygen reduction reaction results indicate that Fe2N/NHPCS has the synergistic catalytic performance of higher onset potential (0.96 V), higher electron transfer number (similar to 4) and higher limited current density (1.4 times as high as that of commercial Pt/C). In addition, this material is implemented as the air catalyst for zinc-air battery that exhibits considerable specific capacity (795.1 mA.h/g) comparable to that of Pt/C, higher durability and maximum power density (173.1 mW/cm(2)).