Zeolite Proton Conducting Membrane for Micro Fuel Cell Applications

Supported and self-supporting ZSM-5 membranes (Si/Al = 25) were prepared, assembled and tested for hydrogen fuel cell performance. A Grotthus-like mechanism is proposed for the proton conduction in hydrated zeolites, where the protons hop between neighbouring aluminium sites along a water bridge in the zeolite pores. The supported ZSM-5 membrane was prepared by seeding and secondary regrowth method on cellulose paper, whereas the self-supporting zeolite membrane consists of an array of micromembranes on silicon substrate. The self-supporting HZSM-5 membrane had an open-circuit voltage (OCV) of 0.77 V compared to 0.90 V for supported HZSM-5 and 0.98 V for Nafion 117. The differences are attributed to the contact between the electrode, catalyst and membrane layers in the assembly. The self-supporting HZSM-5 yielded a maximum power density (MPD) of 19.4 mW cm(-2) compared to 14.4 mW cm(-2) for supported HZSM-5 and 35 mW cm(-2) for Nafion 117.