An Axially Directed Cobalt-Phthalocyanine Covalent Organic Polymer as High-Efficient Bifunctional Catalyst for Zn-Air Battery

Abstract

Own to the stable metal-nitrogen-carbon structures, metallophthalocyanines (MPcs) have been extensively studied as building blocks to develop metal incorporated covalent organic polymers (COPs) based catalytic materials. However, it is difficult to obtain MPc-COPs with satisfactory catalytic properties due to the severe stacking nature of MPcs. Herein we proposed an axially coordination method to subduct the π–π interactions of MPcs and facilitate their polymerization. Two alkyl imidazoles have been selected as the axial ligands to direct the condensation of cobalt tetraaminophthalocyanine with p-phthalaldehyde to form a novel linear CoPc based COPs with well-defined structures. The novel COPs provide a reversible excess potential of around 0.74 V for the oxygen reduction/evolution reaction in 1.0 M KOH and a round-trip efficiency of over 57% after 1000 cycles in a homemade zinc-air battery, outperforming the batteries using COPs prepared by conventional methods and commercially available Pt/C@RuO2 catalysts.

Keywords: Cobalt-phthalocyanine, Covalent Organic Polymer, Bifunctional Catalyst, Oxygen reduction reaction, Oxygen evolution reaction, Zn-Air Battery