Electronic structure of intermediates in oxygen reduction reaction on Pt electrode
Oxygen reduction reaction (ORR) on PEM fuel cell cathode is a complex multi-electron process and there has been a long debate on the charge states of its intermediates, such as O2*, OOH*, O* and OH*. In our studies the charge states of ORR intermediates on Pt (111) surface are analyzed in detail based on density functional theory. We find no significant charge transfer between Pt surface and these intermediates; the changes in magnetic moment are achieved by intramolecular spin transition (Qi, et. al, Phys. Rev. Lett. 101, 146101 (2008)). Further calculations under strong external field (0.5 volt/) and monolayer water adsorption confirm that there are only small changes in both electron transfer and induced dipole moment. The near-neutrality, thus validated, enables one to greatly simplify the analysis and modeling of ORR electrocatalysis for a wide range of electrode potentials (Nrskov, J. Phys. Chem. B, 108 (46), 17886, 2004).