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We study the adsorption and the dissociation of O molecules on the active sites of a boron-doped pyrolyzed Fe-N-C catalyst using density functional theory. Initially, we determine the possible structure of the FeN active site of the pyrolyzed Fe-N-C catalyst doped with a boron atom by considering the presence of a nitrogen atom as a metal-free site. The most stable configuration of the structure occurs when the boron and nitrogen atoms coalesce with the FeN site forming a complex site. This structure has higher stability compared to the undoped FeN site. The doped FeN possesses the unique ability to adsorb an oxygen molecule in a side-on mode due to the presence of the boron-nitrogen pair acting as a supporting site. One O atom of the O molecule sticks strongly to the top of the iron atom, while the other binds with the boron atom. This O side-on adsorption stretches the O-O bond length by 15%. Furthermore, the examined catalyst surface can dissociate the oxygen molecule easily with only half the energy barrier of the undoped FeN structure.

We study the oxygen reduction reaction (ORR) mechanism on the neighboring active sites of a B-doped pyrolyzed Fe−N−C catalyst using a combination of density functional theorybased calculations and microkinetic simulations. The structure of the neighboring FeN 4 and B-doped active sites facilitates the O 2 side-on adsorption for a facile dissociation process. This situation gives the B-doped catalyst system a flexibility to access both associative and dissociative reduction mechanisms. Such a mechanism does not exist in the undoped catalyst system because its dissociative mechanism is greatly hindered by the high activation energy for the O 2 dissociation reaction. The lowest calculated ORR overpotentials for the B-doped catalyst system through the associative and dissociative reduction mechanisms are 0.74 and 0.65 V, respectively. The ease of access to the dissociative reduction mechanism improves the ORR overpotential of the catalyst by ∼0.1 V with respect to the associative reduction mechanism. These results demonstrate the origin of superior performance of the B-doped pyrolyzed Fe−N−C catalyst system, which has been observed from experiments.

The interaction between neighbouring FeN4 and Psubs sites of a P-doped pyrolyzed Fe/N/C catalyst promotes four-electron reduction through associative and dissociative mechanisms.