Nitrogen-Doped Carbon Foam as a Highly Durable Metal-Free Electrocatalyst for the Oxygen Reduction Reaction in Alkaline Solution

Abstract

Nitrogen-doped carbon foam (CFN) with large surface area is synthesized via a template-free, scalable combustion technique using diethanolamine as a nitrogen source. The resulting macroporous, open-cell foam has micron-scale hollow cells, surrounded by thin, graphene-like walls. This material is applied as a metal-free electrocatalyst for the oxygen reduction reaction (ORR) in alkaline KOH solution. The activity of this metal-free electrocatalyst at the half-wave potential is just 43 mV lower than that of platinum-decorated carbon (Pt/CB), but 87 mV lower than a commercially available Fe-containing non-precious electrocatalyst (Pajarito Powder, PP), suggesting that iron is important in achieving the highest activities. In durability tests measured over 60,000 potential cycles, Pt/CB and PP undergo significant degradation, whilst the non-precious CFN electrocatalyst shows negligible change, indicating high stability of the electrochemical active sites compared with platinum or iron. Such metal-free catalysts therefore show great promise as electrocatalysts for specific alkaline ion exchange membrane fuel cell (AEMFC) applications where long lifetimes are most important.