Air plasma etching towards rich active sites in Fe/N-porous carbon for the oxygen reduction reaction with superior catalytic performance

Abstract

Herein, an electrocatalyst consisting of iron and nitrogen co-doped porous carbon (Fe–N/C) was prepared by catalytic carbonization of chitin with the assistance of FeCl₃ and ZnCl₂. The catalytic activity of Fe–N/C towards the oxygen reduction reaction (ORR) in both acidic and alkaline electrolytes was significantly enhanced by air-plasma etching for only 120 s, showing a four-electron ORR process with an onset potential and limiting current comparable to those of Pt catalysts. This performance enhancement originated from the removal of less stable sp³ and amorphous sp² carbons which would expose more active catalytic FeN₄ centers, as well as the transformation of a small fraction of iron-based nanoparticles into FeN₄ species.