Construction of Dual-Atom Fe via Face-to-Face Assembly of Molecular Phthalocyanine for Superior Oxygen Reduction Reaction

Porphyry-type aromatic macrocycles such as metallo-phthalocyanines and metallo-porphyrins as single-atomic-site catalysts usually have good catalytic oxygen reduction reaction (ORR) performance. However, the construction of dual active sites using these molecules and the interaction between the active sites have not been much explored. Herein, we developed a facile approach to construct the dual-atom Fe by organizing the face-to-face self-assembly of molecular iron phthalocyanine (FePc) and transforming it into nanorod-like architectures under microwave irradiation. The (001)-oriented growth induced by strong intermolecular π–π-stacking to frame the stable-phase FePc was observed in the self-assembled FePc nanorods. The nanorods exhibited superior ORR performance than molecular FePc and state-of-the-art 20% Pt/C in alkaline media (260 and 60 mV positive shifting in half-wave potential compared with the molecular FePc/C and 20% Pt/C). Theoretical studies on crystal structures and reaction mechanisms revealed that the self-tailored space (4.92) between two neighboring Fe active sites facilitated mutual coordination with dioxygen by forming a dual-atom Fe species of a trans-bridged peroxo adduct (Fe–O–O–Fe), which favored the cleavage of the O–O bond and the release of OH* intermediates, resulting in an increase in ORR activity. This investigation revealed the possibility of enhancing the electrocatalysts' performances by assembly and tailoring of the active sites' interactions.