Exploration of Oxygen Reduction Reaction Catalyzed by FePPc and Pz-FeTPr Conjugated Organic Polymer: Insights From Grand-Canonical Density Functional Theory.

This report examines the oxygen reduction reaction (ORR) catalyzed by iron-polyphthalocyanine (FePPc) and pyrazine-linked iron-coordinated tetrapyrrole (Pz-FeTPr) conjugated organic polymer (COP) catalysts, utilizing grand-canonical density functional theory (GC-DFT) and microkinetic (MK) simulations. The computed half-wave potential for AA stacking FePPc under alkaline conditions is in strong agreement with experimental findings. The ORR mechanism for AA stacking FePPc is characterized by the O mechanism ( ), with the Fe site serving as the active site. In the case of Pz-FeTPr, the ORR mechanism is similarly governed by the O mechanism, with the Fe site remaining the active site at lower potentials (less than 0.5 V, vs reversible hydrogen electrode). However, at higher potentials (greater than 0.5 V), the Fe site becomes obstructed by , resulting in a shift of the active site from the Fe site to a neighboring C site (designated as type A3). The corresponding ORR mechanism at the C site is denoted as mechanism ( ). This mechanism yields a calculated half-wave potential that aligns well with experimental observations. The mechanisms identified for FePPc and Pz-FeTPr can be substantiated by the Raman signals detected in experimental studies.