Structurally Tailored Covalent Triazine Frameworks as Multitasking Electrodes for Supercapacitors, HER, ORR, and Zinc-Air Batteries

Abstract

Integrating multiple functionalities within a single material system is critical for the development of cost-effective, sustainable, and technologically advanced clean energy devices. We report a series of highly porous nitrogen-/oxygen-codoped covalent triazine frameworks (Azo-Oxy-CTFs), synthesized through dynamic cyclotrimerization of a low-cost azo-/hydroxy-functionalized benzonitrile monomer (Azo-Oxy-CN) in molten ZnCl2. The ionothermal synthetic conditions induce partial in situ structural rearrangement of initially formed organized triazine frameworks via carbonization and decomposition processes, generating amorphous architectures with well-defined porosity embedded with graphitic domains combining carbon defects and electroactive sites (pyridinic-N, graphitic-N, and carbonyl). The extent of rearrangement is strongly governed by the synthesis temperature, imparting distinct electrochemical properties across the series. Electrochemical assessment reveals trifunctionality: as supercapacitors, Azo-Oxy-CTFs deliver a specific capacitance of 216 F g-1, remarkable cyclic stability over 30000 cycles, and impressive specific energy (16.7 Wh kg-1) and power (3407 W kg-1); as electrocatalysts, they exhibit high performance for both oxygen reduction (E 1/2 = 0.78 V) and hydrogen evolution reactions, with low overpotentials of 74.6 and 157.6 mV at 10 and 50 mA cm-2, respectively. When integrated as Zn-air battery cathodes, they deliver 144.8 mW cm-2 peak power density and stable operation for 100 h at 10 mA cm-2 with 3.5% voltage variation, surpassing commercial 20 wt % Pt/C.