Proton-Conductive Matrix-Mixed Membrane Based on Sulfonated Polyimide Functionalized Vermiculite Clay

Abstract

Fuel cell technology offers a promising alternative for clean energy, with polymer electrolyte fuel cells (PEMFCs) attracting significant interest. Herein, Sulfonated polyimide (SPI) membranes were synthesized via high-temperature direct imidization using two different sulfonated diamines. Subsequently, 3-aminopropyltriethoxysilane (APTES)-functionalized vermiculite (VMT) clay was incorporated into the SPI matrix using a solution casting method to create SPI/VMT nanocomposite membranes. Characterization techniques, including FTIR and Raman spectroscopy, XRD, TGA, and DSC analyses confirmed the successful incorporation of VMT clay into the SPI matrix. SEM analysis performed to investigate surface morphology of synthesized SPI/VMT composite membranes. The resulting SPI/VMT membranes exhibited enhanced proton conductivity (i.e., 2.142 × 10⁻⁵ to 2.075 × 10⁻⁶ S. cm⁻¹) and improved thermal, mechanical, and chemical stability compared to pristine SPI. Physicochemical and EIS analyses revealed key properties: IEC ranging from 2.43 to 3.20 mmol/g, water uptake (WU%) between 2.38% and 3.82%, hydrolytic stability 202 h, oxidative resistance of 24–25 h at 80°C, and anisotropic dimensional changes (∆t/∆l) ranging from 2.40 to 5.92. These findings highlight the potential of grafted- VMT modified SPI membranes for durable and efficient PEMFCs in applications. Future research will focus on further enhancing the VMT clay to improve membrane performance and durability.