N-doped carbon nanotubes containing a high concentration of single iron atoms for efficient oxygen reduction

Fe-N-C has emerged as a promising noble-metal-free catalyst for the oxygen reduction reaction (ORR). However, achieving a catalytic activity comparable to that of Pt in acidic medium remains a great challenge. Here we report a N-doped carbon nanotube (CNT) catalyst in which a high concentration of single Fe atoms has been dispersed (CNT@Fe-N-PC). The catalyst was prepared by a simple and scalable atomic isolation method, in which a metal isolation agent was introduced to isolate Fe atoms and was then evaporated to produce abundant micropores that host single Fe atom active sites. The CNT@Fe-N-PC catalyst contained a high concentration of single Fe atom active sites and exhibited ultrahigh ORR activity with a half-wave potential of 0.82 V, comparable to that of Pt/C in an acidic medium. A high concentration of Fe-N-x active sites was created on a flexible single-wall CNT film and carbon cloth using this technique, and these materials showed even better ORR performance, that is, 40-60 mV more positive onset potentials than those of a commercial Pt/C catalyst. These catalysts exhibit excellent catalytic activity, good durability and low cost, and show great potential for commercial use as substitutes for current Pt-based catalysts.