Pyrolysis-Free Covalent Organic Polymer Efficiently Driving Proton-Exchange-Membrane Fuel Cells by Covalent Grafting Strategy

Abstract

Covalent organic polymers (COPs) have emerged as promising oxygen reduction reaction (ORR) catalysts due to their structural tunability and well-defined active sites. However, their practical application is hindered by inherent electrical conductivity and restricted active site accessibility in bulk configurations. While van der Waals-assembled COP-carbon composites enhance conductivity, persistent stacking, and weak interfaces still impede electron/mass transport during ORR. Herein, a covalent grafting strategy is proposed to fabricate a lamellar COP network COP@G, which is achieved by edge-functionalizing COP with aromatic primary amine groups, followed by diazotization reactions and covalent attachment of graphene dispersions. The resulting hybrid exhibits significantly improved active site accessibility and a tenfold increase in conductivity compared to pristine COP. As a result, in 0.1 M HClO₄, COP@G delivers an exceptional acidic ORR performance, with a record half-wave potential of 801 mV, surpassing van der Waals-assembled COP-G by 194 mV. When integrated into proton-exchange-membrane fuel cell (PEMFC) cathodes, COP@G demonstrates an order-of-magnitude enhancement in maximum power density compared to conventional COP-carbon composites.