DFT study of oxygen reduction reaction on n-substituted carbon electrodes. Adsorption

Abstract

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. © 2011 Ceramic Society of Japan.