Formation of Tilted FeN<sub>4</sub> Configuration as the Origin of Oxygen Reduction Reaction Activity Enhancement on a Pyrolyzed Fe-N-C Catalyst with FeN<sub>4</sub>-Edge Active Sites
Adhitya Gandaryus Saputro, Arifin Luthfi Maulana, Fadjar Fathurrahman, Muhammad Haris Mahyuddin, Mohammad Kemal Agusta, Ganes Shukri, Hadi Teguh Yudistira, I Gede Wenten, Hermawan Kresno Dipojono
Abstract
We elucidate the origin of oxygen reduction reaction (ORR) activity enhancement on the FeN4 site at the edge of a pyrolyzed Fe-N-C catalyst (FeN4-edge) using a combination of density functional theory calculations and microkinetic simulations. The presence of graphitic edges facilitates the formation of FeN4 active sites. Majority of these edge active sites have quite similar activities as in the case of a typical FeN4 active site in the interior of graphene (FeN4G). The ORR activity enhancement of this catalyst originates from the formation of two unique tilted-FeN4 configurations at the edge of graphene, which have remarkable ORR activities. The first configuration is the tilted FeN4 site at the zigzag edge, which can positively shift the onset potential for the associative reduction mechanism about 0.13 V higher than that on the typical FeN4G system. The second configuration is the tilted FeN4 site at the armchair edge, which has a low O2 dissociation energy and a high onset potential for the dissociative reduction mechanism (0.26 V higher than the FeN4G system).