Engineering Carbon Vacancy Defects in Conjugated Microporous Polymer-Derived Electrocatalysts for Boosting Oxygen Reduction

Single-atom iron–nitrogen–carbon catalysts (Fe–N–C SACs) are promising nonprecious metal catalysts that play an important role in improving the energy conversion and storage of zinc–air batteries (ZABs). Nevertheless, the synergistic design and control of the structural characteristics of active sites to enhance the catalytic activity and stability still remain challenging. In this work, a series of Fe–N–C SACs with abundant carbon vacancies were constructed from conjugated microporous polymers (CMPs) containing pyridine-N through the rational molecular design of CMP precursors and urea-assisted defect engineering. The phenanthroline units in the CMP skeletons stabilize the Fe atoms by forming well-defined Fe–N 4 coordination structures within the carbon matrix, and urea-assisted etching further modulates the active sites by creating abundant carbon vacancies, which not only increase the exposure of the Fe centers but also optimize the electronic structure of the active sites. As expected, the resulting CMP-derived catalyst, particularly TET-FeVc-800, exhibited high ORR activity with an onset potential of 0.985 V and a limited current density of 5.54 mA cm –2, following an efficient four-electron transfer pathway with excellent cycling stability and methanol tolerance. Moreover, when applied in a ZAB device, TET-FeVc-800 exhibited a competitive specific capacity of 786 mA h g –1 and an impressive long-term durability exceeding 240 h, outperforming Pt/C+RuO 2 catalysts (558 mAh g –1, 85 h), demonstrating its great potential for practical use. This work not only provides a rational design strategy for the effective construction of SAC catalysts from CMPs but also presents a synergistic approach to enhance the electrocatalytic performance of ZABs through defect engineering.