Silicate and zirconium phosphate modified Nafion/PTFE composite membranes for high temperature PEMFC

The PEMFC performance of MEAs prepared from Nafion-212 (thickness 50 μm, Du Pont Co), porous poly(tetrafluoro ethylene) (PTFE, thickness 15 ~ 18 μm) film reinforced Nafion (NF, thickness 20 ± 2 μm), silicate hybridized NF (NF-Si, thickness 21 ± 2 μm), and zirconium phosphate hybridized NF (NF-Zr, thickness 21 ± 2 μm) membranes were investigated at 110 °C/ 51.7% RH, 120 °C/ 38.2% RH, and 130 °C/ 28.6% RH. We show PEMFC performances of these MEAs decrease in the sequence of: NF-Zr> NF-Si> NF> Nafion-212. The NF, NF-Si, and NF-Zr membranes have lower membrane thickness and lower Nafion content and require less water for proton transport than Nafion-212 at temperatures above 110 °C, and thus have higher conductivity and better PEMFC performance than Nafion-212. Incorporating silicate and zirconium phosphate into NF membranes enhances water retention of membranes at temperatures above 110 °C and improves PEMFC performances. Besides enhancing water retention, incorporating zirconium phosphate into membranes also provides more routes for proton transport via H⁺ exchange between H₃ ⁺O and HPO₄-Zr- and between H₂ ⁺PO₄-Zr- and HPO₄-Zr-. Thus NF-Zr has a higher conductivity and better PEMFC performance than NF and NF-Si.