Synthesis and Characterization of a Self-Assembled Nafion/Silica Nanocomposite Membrane for Polymer Electrolyte Membrane Fuel Cells

A novel Nafion/SiO 2 nanocomposite membrane has been developed by combining the self-assembly route and Nafion/SiO 2 hybrids. Nafion-stabilized SiO 2 nanoparticles were synthesized by using the self-assembly route. The hydrolysis procedure has significant influence on the size and distribution of SiO 2 nanoparticles and the quality and performance of the composite membranes. Best results were obtained on the Nafion/SiO 2 composite membrane recast from Nafion−SiO 2 (5 wt %) nanoparticles with a H 2 O:TEOS ratio of 4:1. The Nafion/SiO 2 composite membrane prepared by the self-assembled Nafion–SiO 2 nanoparticles shows remarkable durability as compared to the Nafion/SiO 2 composite membrane prepared by the conventional sol−gel method and pure Nafion 212 membrane, most likely due to the intimate interface between the self-assembled Nafion–SiO 2 nanoparticles and Nafion polymeric matrix. The tensile strength and proton conductivity of the self-assembled Nafion/SiO 2 nanocomposite membranes are 27.5 MPa and 0.090 S/cm, respectively, close to that of the pure Nafion 212 membrane. The λ H 2 O/SO 3 H of the self-assembled Nafion/SiO 2 composite membrane at 60 °C is 7.02, ∼5 times higher than 1.33 of the Nafion 212 membrane. Very different from the pure Nafion 212 membrane, the PEM fuel cells assembled with a self-assembled Nafion/SiO 2 nanocomposite membrane show good performance and negligible performance decay when the RH of the inlet gases changes from 100% to 50% under a constant current load of 600 mA cm −2 at 60 °C. This work demonstrates the promising potential of the self-assembled Nafion/SiO 2 composite membranes for the development of high-performance and high-stability PEM fuel cells with high tolerance to RH variations at elevated high temperatures.