We study the oxygen reduction reaction (ORR) mechanism on a Pt(1 1 1) surface using density functional theory calculations. We find that at low overpotentials the surface is covered with a half dissociated water layer. We estimate the barrier for proton transfer to this surface and the barrier for proton transport parallel to the surface within the half dissociated water network. We find both barriers to be small. The only potentially dependent step is the proton transfer from water to the half dissociated water layer. We find that ORR proceeds via four direct e- reductions without significant peroxide formation. We show that the oxygen-oxygen bond breaking is dependent on the local surface environment. The minimum energy pathway is constructed and we confirm that OH removal from the surface determines the overpotential.
- Oxygen reduction reaction
- Reaction mechanism