Novel Fluoroboric Acid Additive for Blend Membrane to be Used in PEM Fuel Cell, Characterization Studies, and Performance Test

This study focuses on developing an alternative membrane for PEMFC due to the disadvantages of using Nafion. Fluoroboric acid (FBA) was used as an additive material to SPEEK-PVA blend membranes at different weight ratios (1%, 5%, 7.5%, 10%, and 12.5%), and a synthesis procedure was carried out with the solution-casting. Thermal crosslinking was performed with all membranes. Utilizing FBA, with its highly electronegative fluorine groups, is a novel approach expected to enhance proton conductivity. The structural, morphological, and thermal properties of the synthesized membranes were determined by FTIR, XRD, SEM, TGA-DTG, and DSC. Water uptake capacity (WUC), swelling property, area change, dynamic mechanical analysis, ion exchange capacity (IEC), AC impedance analysis, hydrolytic stability, and oxidative stability analyses were performed for fuel cell applications. Although FBA does not have a crystal structure, the synergy it created with the SPEEK-PVA membrane increased the crystallinity of the membrane and, accordingly, glass transition temperature. SEM images of membranes at a ratio above 7.5% show that agglomerations occur in the structure and this is supported by other analyses. It was determined that the membrane composition with the highest WUC (16.44%), IEC (1.55 meq/g), and proton conductivity (0.57 S/cm) values contained 7.5% FBA from the characterization studies, and a single-cell performance test was actualized with this. 418 mA/cm2 current density and 250.8 mW/cm2 power density were obtained at 0.6 V cell potential, with the membrane containing 7.5% FBA. This study shows that the synthesized membrane, especially the FBA, is a promising option for PEMFC application.