Near neutrality of an oxygen molecule adsorbed on a Pt(111) surface.

The charge state of paramagnetic or nonmagnetic O2 adsorbed on a Pt(111) surface is analyzed using density functional theory. We find no significant charge transfer between Pt and the two adsorbed molecular precursors, suggesting these oxygen reduction reaction (ORR) intermediates are nearly neutral, and changes in magnetic moment come from self adjustment of O2 spin-orbital occupations. Our findings support a greatly simplified model of electrocatalyzed ORR, and also point to more subtle pictures of adsorbates or impurities interacting with crystal than literal integer charge transfers.