DBSA-doped PEG/SiO2 proton-conducting hybrid membranes for low-temperature fuel cell applications

Hybrid membranes were made through a sol-gel process from 3-(triethoxysilyl)propyl isocyanate functionalized by polyethylene glycol (PEG). 4-Dodecylbenzene sulfonic acid (DBSA) was incorporated into the matrix as a proton source. DBSA-doped PEG/SiO2 hybrid membranes exhibit reasonable proton conductivity, and some of them show extremely low methanol permeability, which resulted in higher value of the ratio of proton conductivity to methanol permeability than that of Nafion membrane. Therefore, DBSA-doped PEG/SiO2 hybrid membranes can reduce the problem associated with methanol cross-over in direct methanol fuel cells (DMFC). The feasibility of these materials as a polymer electrolyte in hydrogen/oxygen fuel cells (H-2/O-2 FC) as well as DMFC is investigated with the aim of developing a suitable membrane electrode assembly (MEA) fabrication method for hybrid membranes utilizing the membrane consisting of 80 wt.% monophenyl trimethoxysilane (MPh) as silica phase modifier and 20 wt.% DBSA (MPh80DBSA20) as a model material. Fuel cell measurements were carried out at low temperature and atmospheric pressure. The preliminary results are presented and made into comparison with the performance of similar hybrid membranes and Nafion. (C) 2004 Elsevier B.V. All rights reserved.