The operating temperature range of low-temperature proton-exchange membrane (PEM) fuel cells can be increased by using proton-conducting inorganic membranes instead of polymeric PEM electrolytes. This Small Business Innovation Research (SBIR) Phase I project will develop proton-conducting, membrane-like zeolites for use in low-temperature fuel cells. Prototype fuel cells will also be developed and tested. Low-temperature ionic conductivity in zeolites will be induced by incorporating proton-conducting hydrous salt ions as cations in the zeolite lattice. The cations in zeolites, along with protons, reside in the microscopic channels, cages, and cavities of the zeolite framework. The structure and chemistry of cations in proton-conducting zeolites will be investigated by spectroscopic techniques: extended X-ray-absorption fine structure (EXAFS), X-ray-absorption near edge structure (XANES), X-ray photoelectron spectroscopy (XPS), and nuclear magnetic resonance (NMR) spectroscopy. Ionic conductivity will be determined by AC impedance and DC conductivity measurements. The structural and chemical information, to be obtained by spectroscopic studies, will be used to optimize the chemical composition and crystal structure of proton-conducting zeolites. In Phase I, proton-conducting mordenite and ZSM-5 zeolite thin films on conductive porous substrates will be synthesized. The zeolite films will be prepared by hydrothermal crystallization from aluminosilicate gels followed by ion-exchange treatments and heat-treatments for drying and calcination. These low-temperature fuel cells with proton-conducting zeolite electrolytes are expected to work in a temperature range of about 90-125o Centigrade. With inorganic electrolytes they will generate power using methanol or hydrogen fuel and serve potentially as the power supply for the electric-car Next Generation Vehicle (NGV). In addition to zero-emission automotive applications, they may have commercial application in submarines and other watercraft.
