Tuning the spin state of FePc via selectively defected carbon for enhanced oxygen reduction reaction

Tuning the spin state of the FeN₄ site to optimize its adsorption strength for the ORR intermediates remains a challenge. Herein, we demonstrate that a defect-engineered carbon material via CO₂ selective etching can effectively raise the spin state of Fe center of FePc/NC-CO₂-900 compared to that of FePc. It shows a higher half-wave potential of 0.90 V and kinetic current density of 110.6 mA cm^-2 at 0.8 V than those of Pt/C and FePc. Theoretical calculations reveal that FePc with increased spin state in FePc/NC-CO₂-900 facilitates the activation of oxygen molecules compared to the FePc catalyst.