How do cyclic functional groups in the Cl-iron 3,5-diisopentoxyphenyl porphyrin complex influence the oxygen reduction reaction?

To improve the efficiency of proton exchange membrane fuel cells and air batteries, one must solve the slow kinetics of the oxygen reduction reaction (ORR) on the cathode by using catalysts, which satisfy low-cost, high durability, and environmental friendliness. Recently, nitrogen and iron-based macrocycles such as iron porphyrins have attracted much attention. Although experiments have investigated the ORR activity of the Cl-iron 3,5-diisopentoxyphenyl porphyrin macromolecules (ClFeM), the effects of adding cyclic functional groups such as hydroxyphenyl, carboxylphenyl, aminophenyl, thiophenyl, and pyridyl to ClFeM on the ORR mechanisms and activity remain unknown. Here, we explored this issue using the van der Waals-corrected density functional theory calculations. The research will answer three questions: (1) How do the cyclic functional groups modify the ORR mechanisms and activity? (2) How do the cyclic functional groups affect the stability of the catalysts via studying dissolution potentials? And what is the role of the Cl atom in the stability of the ClFeM-based catalysts? Furthermore, we also elucidated the physical insights into the interaction of the intermediates with the ClFeM-based complexes.