Porous substrate-reinforced composite proton exchange membranes have drawn considerable attention due to their promising application to polymer electrolyte membrane fuel cells (PEMFCs). In the present study, we develop silica (SiO2) nanoparticles/polyetherimide (PEI) binders-coated polyimide (PI) nonwoven porous substrates (referred to as " S-PI substrates" ) for reinforced composite membranes. The properties of S-PI substrates, which crucially affect the performance of resulting reinforced composite membranes, are significantly improved by controlling the hygroscopic SiO2 particle size. The 40nm S-PI substrate (herein, 40nm SiO2 particles are employed) shows the stronger hydrophilicity and highly porous structure than the 530nm S-PI substrate due to the larger specific surface area of 40nm SiO2 particles. Based on the comprehensive understanding of the S-PI substrates, the structures and performances of the S-PI substrates-reinforced composite membranes are elucidated. In comparison with the 530nm S-PI substrate, the hydrophilicity/porous structure-tuned 40nm S-PI substrate enables the impregnation of a large amount of a perfluorosulfonic acid ionomer (Nafion), which thus contributes to the improved proton conductivity of the reinforced Nafion composite membrane. Meanwhile, the reinforced Nafion composite membranes effectively mitigate the steep decline of proton conductivity with time at low humidity conditions, as compared to the pristine Nafion membrane. This intriguing finding is further discussed by considering the unusual features of the S-PI substrates and the state of water in the reinforced Nafion composite membranes.
Bibliographical noteFunding Information:
This work was supported by the New & Renewable Energy R&D Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) Grant funded by the Korea government Ministry of Knowledge Economy (2008-N-FC12-J-01-2-100). This research was also supported by a Grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy. This work was also supported by the National Research Foundation of Korea Grant funded by the Korean Government (MEST) (NRF-2009-C1AAA001-2009-0093307).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Surfaces, Coatings and Films
- Colloid and Surface Chemistry