Covalent-Bridged Heterointerfaces via Grafted Triazine Organic Polymers Enable Directed Charge Transfer for Efficient Oxygen Reduction in Zn–Air Batteries

Covalent triazine framework (CTF) derivatives have emerged as promising metal-free electrocatalysts due to their high nitrogen content and intrinsic porosity. However, their performance remains limited by sluggish interfacial charge transport and the inaccessibility of active sites. Herein, we report an interfacial covalent bridging strategy based on grafting polymerization to construct a carbon heterostructure electrocatalyst, featuring vertically aligned nitrogen-doped nanosheets covalently anchored onto graphene (v-N/CNS/Gr) support. The covalently bridged interface promotes interfacial charge transfer across the heterostructure, activating otherwise dormant nitrogen active sites and amplifying the oxygen reduction reaction (ORR) reactivity. In situ spectroscopic analyses and theoretical simulations reveal that the covalent bridged bonding promotes charge transport and oxygen activation, and optimizes the adsorption/desorption of intermediates, collectively contributing to reduced energy barriers along the 4e^- ORR pathway. As a result, the v-N/CNS/Gr delivers excellent ORR activity with a half-wave potential of 0.85 V (vs RHE). When employed as the cathode in a Zn-air battery, v-N/CNS/Gr achieves a high-power density and stable operation over 850 h. This work demonstrates a generalizable triazine-polymer-based interfacial bridge strategy for enhancing active site accessibility and charge transport in metal-free electrocatalysts.