Coupling of iron phthalocyanine at carbon defect site via π-π stacking for enhanced oxygen reduction reaction

Abstract

The intrinsic activity of transition metal catalytic centers for oxygen reduction reaction (ORR) depends heavily on its electronic structure, which with an electron-rich environment will boost the ORR performance. In this work, we firstly revealed the defective graphene (DG) substrate with 585 defects could efficiently mediate charge redistribution of the attached exfoliated monolayer Iron Phthalocyanine (FePc) by using density functional theory (DFT) calculation. The electrons transfer to FePc from 585 defects forms an electron-rich region on Fe atom, and high-density electrons further raise the d-band center of Fe atom. Apparently, this adjustment of electronic structure for Fe atoms is beneficial to the adsorption and reaction of O2 molecules, inducing more positive initial potential and larger current density for ORR. Based on this finding, DG obtained by the heat treatment was prepared to couple exfoliated monolayer FePc through stable π-π stacking. As expected, FePc/DG hybrid exhibits outstanding electrocatalytic ORR performance with a positive initial potential (0.98 V vs. RHE) and a high current density (5.45 mA·cm−2) in 0.1 M KOH electrolytes. In addition, the FePc/DG hybrid was utilized to assemble a zinc-air battery device, which reveals the power density of 190 mW·cm−2.