Hybrid Inorganic-Organic Phosphosilicate Membranes for Medium Temperature H2/O2 Fuel Cells
M. Mika, B. Klapste, M. Paidar, K. Bouzek, J. Vondrak
Institute of Chemical Technology, CZ
H2/O2 fuel cell, phosphosilicate polymer
We developed a new fast proton conducting membrane based on the hybrid inorganic-organic phosphosilicate polymer. The membrane keeps it high conductivity in dry conditions at temperatures above 100°C. The backbone of the membrane is the polydimethylsiloxan polymer with phosphorus heteroatoms. The developed preparation procedure ensures a high concentration of hydroxyl groups in the polymer that facilitate fast proton migration at low humidity. The temperature dependence of the proton conductivity was measured using electrochemical impedance spectroscopy. In a dry atmosphere the conductivity was about 0.02 S/cm at 120°C. We tested our membranes in a commercial H2/O2 fuel cell operating in the temperature range from 22 to 120°C using dry H2 and O2 gases. We employed standard commercial electrodes made of carbon paper with Pt/C catalyst. The performance of the fuel cell significantly improved as the temperature increased; the maximum of power density increased and moved to higher current densities and the absolute value of the slope of the voltage/current characteristic decreased. In our paper we report and discuss the observed effects of composition and preparation conditions on the measured properties of our membranes and on their performance in the H2/O2 fuel cell at elevated temperatures using dry reactant streams.
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