Electrochemically Controlled Deposition of Low-Crystalline Covalent Organic Frameworks on Nanocarbon Electrode Toward Metal-Free Oxygen Reduction Electrocatalyst.

Morphology-controlled synthesis of covalent organic frameworks (COFs) offers significant potential for electrochemical applications. However, controlling the deposition of nanometer-scale COFs on carbon supports remains challenging due to the need for a slow COF generation rate and the dispersion of carbon supports in liquid-phase synthesis. In this study, nanometer-scale COF/carbon composites are fabricated using electrochemically generated acid (EGA) to assist in the formation of imine-type COFs, which are then deposited onto pre-cast nanocarbon supports on an electrode. A monomer combination of tri(4-aminophenyl)-1,3,5-triazine and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde is utilized due to their suitable oxidation potentials, with 1,2-diphenylhydrazine serving as the EGA source. Through proton generation driven by electrolysis conditions, controlled COF formation is achieved at the single nanometer scale, ranging from 6 to 30 nm, on various nanocarbon supports. The COF/carbon electrode is evaluated as an oxygen reduction reaction (ORR) electrocatalyst, demonstrating superior performance compared to other COF-based electrode materials containing the 1,3,5-triazine moiety. The findings experimentally validate the efficacy of the EGA-assisted COF deposition method for nanostructure construction and its ability to enhance the properties of COF-based electrodes through morphology tuning.