Preparation and performance study of ionic liquid @ boron nitride modified polyimide proton exchange membrane

Proton exchange membrane (PEM) plays a relatively significant part in PEM fuel cells (PEMFCs). In this study, ionic liquid were grafted onto boron nitride (ILs@BN) were prepared by wet ball milling, and the polyimide (PI) composite films with different contents (1, 2, 3, 4, and 5 wt%) of ILs@BN were fabricated by solution-casting method. Results showed that compared with the original polyimide films, the performance of the obtained composite films has been significantly improved. Tensile strength of film containing 4 wt% ILs@BN was enormously enhanced by 93.62% (from 47 to 91.8 MPa), respectively, in contrast to pure PI film. Compared with pure PI film, film containing with 4 wt% ILs@BN was reduced from 71.2 degrees to 63.2 degrees, which indicated the better hydrophilicity of the film and potential proton transport channels. The composite film exhibited excellent proton conductivity, which was tremendously elevated by 58.35% (from 0.1215 S cm(-1) for pure PI to 0.1924 S cm(-1) for film containing with 4 wt% ILs@BN). Comprehensively, the film containing with 4 wt% ILs@BN presenting excellent mechanical properties (91.8 MPa), contact angle (63.2 degrees) and proton conductivity (0.1924 S cm(-1)) demonstrating strong potential applications in fuel cells.

Automated summary

This study prepared ionic liquid grafted boron nitride (ILs@BN) using wet ball milling, and fabricated polyimide (PI) composite films with different contents (1, 2, 3, 4, and 5 wt%) of ILs@BN by solution-casting method. The obtained composite films showed significantly improved performance compared to the original polyimide films. The film containing 4 wt% ILs@BN exhibited enhanced tensile strength, better hydrophilicity, and excellent proton conductivity, showing great potential applications in fuel cells.