Oxygen Reduction Reaction Studies of Phosphorus and Nitrogen Co‐Doped Mesoporous Carbon Synthesized via Microwave Technique

Abstract

Abstract Metal‐free mesoporous P and N co‐doped carbon (PNDC) composites are evaluated for their electrocatalytic activity towards the oxygen reduction reaction (ORR). Carbonization of melamine and hexamine‐modified tannin in the presence of polyphosophoric acid produces PNDCs with prominent oxygen reduction properties in alkaline media. The effect of the P and N content in the carbon material is evaluated in terms of the ORR activity. The compound containing a high amount of N (8.3 atom %) and P (6.8 atom %), denoted PNDC‐1, shows high electrocatalytic activity, stability, durability, and selectivity towards the ORR. PNDC‐1 has an onset potential of 0.10 V versus a reversible hydrogen reference electrode and shows a significantly improved performance in comparison to the carbon materials containing less P and N dopant atoms. PNDCs exhibit superior ORR current densities to that of the 20 % Pt/C catalyst because of the synergetic effect of P and N co‐doping. X‐ray photoelectron spectroscopy studies indicate the presence of pyridinic and graphitic N species, which are responsible for oxygen reduction that results in higher current densities. Rotating disk electrode and rotating ring‐disk electrode studies support a four electron oxygen reduction to water, with negligible generation of hydrogen peroxide.