High-performance COF-based composite anion exchange membrane sandwiched by GO layers for alkaline H2/O2 fuel cell application

Abstract

With well-defined structure and high stability, covalent organic framework (COF) inspires the preparation of new ion-conducting materials for anion exchange membrane (AEM) in alkaline fuel cell. In order to reveal the influence of micro-nano structure within COF ordered channels on the hydroxide diffusion, we construct a multi-dimensional composite membrane by combining two-dimensional lamellar COF with one-dimensional polymer chains. The quaternary ammonium-modified COF-LZU1 (QAmCOF-LZU1) is incorporated into quaternized poly (2,6-dimethyl-1,4-phenylene oxide) (QAPPO) to fabricate QAmCOF-LZU1/PPO composite membranes. The rapidly diffusion of hydroxide ions in the first solvent shell formed by the huge amount of quaternary ammonium groups in the ordered COF channels is investigated by molecular dynamics simulations. Afterwards, sulfonated graphene oxide (GO) is coated on both surfaces of the membranes via ionic interactions and π-π interactions to obtain GO@QAmCOF-LZU1/PPO sandwich membranes, which would avoid excessive swelling of membranes and leakage of QA groups. Especially, the GO-sandwiched membrane exhibits strikingly high stabilities and excellent H2/O2 fuel cell performance with a peak power density of 242 mW cm−2 at 60 °C. This study provides an effective strategy to construct ion-conducting COF-based composite membranes for high-performance alkaline fuel cell.