Density functional theory study of the copper phthalocyanine based metal−organic frameworks as the highly active electrocatalysts for the oxygen reduction

Recently, the copper phthalocyanine based 2D conjugated MOFs have been demonstrated that it can efficiently catalyze the oxygen reduction reaction (ORR) experimentally. Herein, the inherent properties and ORR mechanism of PcCu-O8-M (M = Fe, Co, Ni, Cu) containing two potential active sites (M–O4 and Cu–N4 sites) are investigated by density functional theory methods. The binding energy of oxygen-containing intermediates on PcCu-O8-M indicates that the binding strength of ∗OOH, ∗O, and ∗OH at the M–O4 site is more moderate than that at the Cu–N4 site. For all studied sites, their potential-determining steps are the step of O2 → ∗OOH except for the Ni–O4 site of PcCu-O8-Ni (∗OH → H2O). Among all sites of PcCu-O8-M, the Fe–O4 and Co–O4 sites have excellent ORR activity with the overpotentials of 0.46 and 0.49 V, respectively, and the Cu–N4 site of PcCu-O8-Co possesses the relatively high ORR activity with the overpotential of 0.79 V. It can be concluded that compared with the Cu–N4 site, the M–O4 site plays major role for each PcCu-O8-M during the ORR process. Moreover, the charge analysis of PcCu-O8-Co suggests that the ORR activities of the Co–O4 and Cu–N4 sites are mainly originated from metal atoms (Co atom and Cu atom) as well as the O and N atoms (O and N-1) coordinated with metal atoms. In addition, PcCu-O8-Co has high poisoning-tolerance ability to NO, NH3, CO, SO2, and H2S.