Boosting electrocatalytic oxygen reduction of Fe-Co polyphthalocyanine via the synergy of metal component optimization and axial ligand modification

Conjugated metal polyphthalocyanine (MPPc) organic skeletons, a kind of novel porous materials containing inherent M-N4 highly active sites, are of great significance for oxygen reduction reaction (ORR). Herein, bimetallic Fe-Co phthalocyanine covalent polymers (denoted as FeCoPPc) were prepared as ORR electrocatalysts through a solvothermal process and subsequent oxidation treatment. Meanwhile, the effect of axial oxygen- containing ligands of metal centers on the catalytic kinetic processes was also investigated. Benefiting from the highly exposed bimetal active sites and the finely designed ligand structure, FeCoPPc with optimized Fe/Co ratio and ClO3- coordination (Fe0.9Co0.1PPc-ClO3) displayed an outstanding ORR electrocatalytic activity and superior durability compared to 20 % Pt/C, manifested by an onset potential of 0.986 V vs. reversible hydrogen electrode (RHE) and a half-wave potential of 0.923 V vs. RHE in a 0.1 M KOH solution. This work may guide the rational design of high-performance electrocatalysts to regulate the catalytic activity.