An effective strategy for the preparation of nitrogen-doped carbon from Imperata cylindrica panicle and its use as a metal-free catalyst for the oxygen reduction reaction

Developing an effective strategy for the large-scale preparation of metal-free catalysts for the oxygen reduction reaction (ORR) is a great challenge. The use of a natural biomass as a green and sustainable precursor for the synthesis of functional materials has attracted significant interest recently. We have successfully synthesized nitrogen-doped carbon as a high-activity catalyst by using Imperata cylindrica panicle as a raw material by combining a simple hydrothermal process with an effective nitrogen-doping technique for thermal annealing in an NH3 atmosphere. Compared to the control sample without nitrogen-doping, the typical product (total N content 2.2 at %) shows a higher catalytic activity in terms of its positive onset potential (0.040 V, vs. Hg/HgO), high current density (5.73 mA cm−2 at −0.8 V vs. Hg/HgO) and approximate four-electron reaction pathway in alkaline media (3.87, at −0.8 V vs. Hg/HgO). In acidic media, these values are approximately 0.500 V (vs. Ag/AgCl), 5.03 mA cm−2 and 3.94 (at −0.2 V vs. Ag/AgCl), respectively. The product also shows superior tolerance to methanol poisoning and outstanding durability in both alkaline and acidic media. In addition, our novel approach to the synthesis of nitrogen-doped carbon materials, in terms of the raw material and preparation method, may guide future efforts for the preparation of carbon-based materials.