Orientation dependence of O2 dissociation from heme–O2 adduct

We report that by controlling the orientation of the impinging O 2 before it binds to heme, we can lower the activation barrier of O 2 dissociation from the heme–O 2 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–O 2 configuration is lower than that for the end-on heme–O 2 configuration. Our results suggest that heme may be utilized as a cathode electrode catalyst in polymer electrolyte fuel cells (PEFCs).