Boosting the ORR active and Zn-air battery performance through ameliorating the coordination environment of iron phthalocyanine

Abstract

Iron phthalocyanine (FePc) with unique iron-pyrrolic nitrogen (Fe-N) structure has attracted an increasing attention on the oxygen reduction reaction (ORR). Unfortunately, the Fe-N site is not “active” because of its symmetry in the plane and always exhibits unsatisfactory ORR activity. Herein, we design a non-contact scheme of axial carbon substrate induced Fe-N electron localization to improve its ORR performance. Theoretical calculation indicates that the addition of MWCNTs causes the aggregation of electron cloud around Fe-N, enhances the oxygen adsorption capacity and accelerates the ORR rate. The obtained catalyst shows a Tafel slope of 35.8 mV·dec−1, an initial potential of 0.979 V vs. RHE, a half-wave potential of 0.902 V vs. RHE and a limiting current density of 5.42 mA·cm−2 in alkaline medium. The Zn-air battery assembled by this catalyst also demonstrates a large discharge voltage of 1.296 V, considerable power density of 102 mW·cm−2 and superior cycling stability (500 cycles). This work not only simplifies the process of preparing high efficiency transition metal catalysts but also does some tentative explore for realizing the practical use of Zn-air battery.