Fabrication of Fuel Cells with Ceramic Gas Separation Membrane

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Ceramic gas separation membrane has been regarded to be thermally stable and resistant to various atmospheres. The present investigation aims at the application of the ceramic separation membrane to the phosphoric acid fuel cell without gas sealing. One of two electrode for the phosphoric acid fuel cell is covered with the membrane with hydrogen selective permeation, whereas the other electrode is open to the atmosphere. This structure may enables to produce voltage from the gaseous mixture of fuel and oxidant. The change of the atmosphere from H_2 to N_2 resulted in transient positive voltage for phosphoric acid fuel cell with Al_2O_3 membrane. On the contrary the switch of gaseous atmosphere from N_2 to H_2 produces negative voltage, whereas the terminal voltage rapidly approaches to zero. A current could be also derived from the above-mentioned fuel cell without gas sealing. However, it was not possible to obtain output voltage continuously because of the insufficient permeation selectivity. The Al_2O_3 plate, Al_2O_3 membrane, and Rh-Al_2O_3 membrane were respectively used for the membrane reactor for methanol steam reforming reaction (CH_3OH+H_2O*3H_2+CO_2). The conversion rose up quite steeply in every case with increasing temperature to 250ﾟC.Complete conversion of methanol was attained in the case of the membrane reactors. Following sequence was obtained for the conversion of methanol ; Fixed bed reactor <reactor with porous Al_2O_3 plate <Al_2O_3 membrane rector <Rh-Al_2O_3 membrane reactor. The produced hydrogen could be effectively removed from the reaction system by the membrane. This situation gave rise to the high overall conversion, especially by use of Rh-Al_2O_3 membrane. High H_2/CO_2 ratio was attained for the gas in the permeation side.