Meso-Structured Aluminosilicate-Nafion Hybrid Membranes for DMFCs

Novel organic-inorganic hybrid membranes have been prepared comprising Nafion and acid functionalized meso-structured molecular sieves (MMS) with varying structures and surface areas. Acid functionalized aluminosilicate mesostructured cellular foam framework Al-MSU-F type, of surface area 463 m/g, aluminosilicate molecular sieve, Al-HMS type, of surface area 651 m/g and aluminosilicate, mesostructured hexagonal frame network Al-MCM-41 type, of surface area 799 m/g have been employed as potential filler materials to form hybrid membranes with Nafion frameworks. The structural behavior, water uptake, ion exchange capacity, proton conductivity and methanol permeability of the hybrid membranes have been extensively investigated. DMFCs employing Nafion-Al-HMS and Nafion-Al-MCM-41 hybrid membranes deliver peak power densities of 170 mW/cm and 246 mW/cm, respectively; while a peak power density of only 45 mW/cm is obtained for the DMFC employing pristine Nafion membrane under identical operating conditions as shown in Fig. 1. The unique properties associated with hybrid membranes could be exclusively credited to the presence of pendant sulfonic acid groups in the filler, which provides fairly continuous proton-conducting pathways between filler and matrix in the hybrid membranes and thus facilitates the proton transport without the anticipated trade-off between conductivity and methanol crossover. Fig. 1. Performance curves for DMFCs with pristine Nafion, Nafion-Al-MCM-41 hybrid membrane as a function of temperature 0 200 400 600 80