Covalent organic polymer with Fe-N4 single-atom anchored on hierarchically porous carbon as efficient oxygen reduction composite electrocatalyst for long-term stable zinc-air batteries

Covalent organic polymers (COPs) are regarded as prospective catalysts toward the oxygen reduction reaction (ORR) owing to their tailorable skeleton structures and precisely identifiable catalytic sites. Nevertheless, their intrinsically low conductivity and insufficiently exposed active sites constitute critical bottlenecks that greatly restrict ORR catalytic performance and cycling durability in practical applications. Herein, we propose a structural engineering strategy to construct high-efficiency and durable composite electrocatalysts (COP@HPC) with well-defined Fe-N 4 active sites, which is achieved by integrating a fully π-conjugated iron-phthalocyanine-based COP with a three-dimensional hierarchically porous carbon substrate via strong π-π interactions. The interconnected conductive network can effectively accelerate electron transfer and mass transport kinetics, while the conjugated COP offers atomically dispersed Fe-N 4 active sites with tunable electronic properties. Consequently, COP@HPC composite catalyst delivers outstanding electrocatalytic performance toward ORR with a high half-wave potential ( E 1/2 ) of 0.92 V, which is superior to that of the composite supported on a dense carbon substrate. In-situ Raman and density functional theory (DFT) calculations confirm the dynamic evolution of ORR intermediates on π-π modulated Fe-N 4 sites, verifying that strong interfacial coupling optimizes intermediate adsorption energy and reduces the rate-determining step energy barrier. When integrated into a liquid zinc-air battery, COP@HPC displays an excellent power density of 227 mW cm −2 and retains stable cycling for over 1000 h (1538 cycles). This work establishes a universal structural engineering methodology for developing high-efficiency single-atom electrocatalysts. A π-π assembly non-pyrolysis strategy is developed to synthesize COP@HPC single-atom electrocatalysts with well-defined Fe-N 4 sites. The 3D porous conductive matrix facilitates electron/mass transfer, while interlayer π-π interactions lower the ORR rate-determining barrier. Download: Download high-res image (189KB) Download: Download full-size image