DFT Study of Oxygen Reduction Reaction on N-substituted Carbon Electrodes. Adsorption

Carbon alloys attract attention as metal-free cathode catalysts. Mechanisms of oxygen reduction reactions are investigated using the DFT calculations and molecular models such as N-substituted coronene, circum pyrene, and corannulene. The overall oxygen reduction reaction (ORR) is decomposed into five elementary reactions. Adsorption of O₂ is important as the first step of reduction, and it depends strongly on the spin density on C atoms, introduced by the N atom. Secondly the peripheral C atoms have an advantage due to the rehybridization freedom to the sp³ configuration. Based on the reversible electrode potential (REP) for each elementary reaction, the overpotential is expected for the first reduction of O₂ to OOH and the final reduction of OH to H²O. These features indicate that N-substituted carbon electrode resembles Pt electrode compared to other less active metals, such as Au.