Assessment of Methanol Crossover Phenomenon of SPEEK/TPA/MCM-41 and SPEEK/TPA/Y-zeolite Composite Membranes for Fuel Cell Application

Abstract

Development of alternative membranes different from Nafion® membranes is among the approaches being pursued to resolve the methanol crossover problem in the direct methanol fuel cell (DMFC). This paper reports comparison of methanol crossover behavior of SPEEK-based composite membranes prepared for use in the DMFC. The composite membranes were prepared by embedding different proportions (10-40 wt %) of inorganic proton conducting material (tungstophosphoric acid (TPA)/MCM-41) and (TPA)/Y-zeolite) into SPEEK polymer matrix. Methanol transport through these membranes was studied using potentiometric technique. The SPEEK/TPA/MCM-41 composite membranes showed lower permeability values of 0.57 x 10-8 cm 2 s-1 - 1.73 x 10-8 cm 2 s-1 compared to the SPEEK/TPA/Y-zeolite composite membranes, which showed permeability values of 2.12 x 10-8 cm2 s-1 - 7.04 x 10-8 cm 2 s-1. These values are low compared to that of pure SPEEK membrane; 4.41 x 10-8 cm2s-1 except the 40wt % TPA/Y-zeolite loading that has a higher permeability value of 7.04 x 10-8 cm2 s-1. Better reduction in methanol permeation was observed with lower loadings of the inorganic material (TPA/MCM-41 or TPA/Y-zeolite) than with higher loadings. The membranes are thermally stable up to 160 ºC. Therefore, these membranes have potential to be used in direct methanol fuel cell due to their low methanol permeability, good thermal stability and moderate cost.