N-doped carbon nanocages with high catalytic activity and durability for oxygen reduction

Abstract

The development of a carbon based non-precious metal catalyst for oxygen reduction reaction (ORR) is of paramount importance for the essential implementation of both proton exchange membrane fuel cells and metal–air batteries. In this work, we report a feasible strategy to synthesize N-doped carbon nanocages (NCNC) with high activity and durability. This is achieved by the pyrolysis of pyridine and iron carbonyl and subsequent heat treatment in the presence of NH₄Cl. Based on detailed studies on the pore structure, the type and transformation of nitrogen-related functional groups, we find that the sample after heat treatment with NH₄Cl has a high specific surface area up to 1093 m² g⁻¹. Also, the sample with high graphitic N doping possesses much better ORR catalytic activity than those dominated by pyridinic and pyrrolic N. The half-wave potential for the final NCNC catalyst is only 40 mV less than a commercial Pt/C catalyst at the initial stage. But the NCNC catalyst shows much better durability than the Pt/C catalyst in acidic electrolytes, and thus provides a new opportunity for Pt replacement.