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

The PEMFC performance of MEAs prepared from Nafion-212 (thickness 50 mu m, Du Pont Co), porous poly(tetrafluoro ethylene) (PTFE, thickness 15 similar to 18 mu m) film reinforced Nafion (NF, thickness 20 +/- 2 mu m), silicate hybridized NF (NF-Si, thickness 21 +/- 2 mu m), and zirconium phosphate hybridized NF (NF-Zr, thickness 21 +/- 2 mu m) membranes were investigated at 110 A degrees C/ 51.7% RH, 120 A degrees C/ 38.2% RH, and 130 A degrees 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 A degrees 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 A degrees 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 H-3 O+ and HPO4-Zr- and between H-2 +PO4-Zr- and HPO4-Zr-. Thus NF-Zr has a higher conductivity and better PEMFC performance than NF and NF-Si.