Orientation dependence of O2 dissociation from heme–O2 adduct

We report that by controlling the orientation of the impinging O2 before it binds to heme, we can lower the activation barrier of O2 dissociation from the heme–O2 adduct to a value comparable to the activation barrier of the well-known platinum catalyst, using ab initio calculations based on density functional theory (DFT). The activation barrier for the O–O bond cleavage for the side-on heme–O2 configuration is lower than that for the end-on heme–O2 configuration. Our results suggest that heme may be utilized as a cathode electrode catalyst in polymer electrolyte fuel cells (PEFCs).