Electrochemical oxygen reduction on carbon nitride

Electrochemical oxygen reduction via non-precious, Fe-macrocycle-derived catalysts has potential to reduce the cost and increase acceptance of hydrogen-powered polymer electrolyte membrane fuel cells. However since these materials are a complex mixture of carbon, nitrogen and iron, the nature of the active site is still much debated. By using carbon nitride as an ideal, nitrogen-rich, iron-free catalyst we shed light on the role of carbon-nitrogen bonding in electrochemical oxygen reduction. Carbon nitride was synthesized on a carbon black support via a simple solvothermal process. The resulting material was pyrolyzed and characterized via a variety of techniques. Electrochemical testing revealed that carbon nitride pyrolyzed at 1000°C displayed the best oxygen reduction activity, with an onset potential of 0.90V and a low selectivity to H₂O₂ formation, indicating a 4-electron oxygen reduction pathway. The enhanced activity is attributed to enriched quaternary nitrogen in the material at this temperature, as confirmed by X-ray photoelectron spectroscopy.