Fabrication of Fuel Cells with Ceramic Gas Separation Membrane

陶瓷气体分离膜被认为是热稳定的，并且耐受各种气氛。本研究旨在将陶瓷分离膜应用于无气封磷酸燃料电池。磷酸燃料电池的两个电极之一覆盖有具有氢选择性渗透的膜，而另一个电极向大气开放。该结构可以使得能够从燃料和氧化剂的气体混合物产生电压。当气氛由H_2转变为N_2时，Al_2O_3膜磷酸燃料电池产生了瞬态正电压。相反，当气氛由N_2切换到H_2时，端电压迅速趋于零，而当气氛由N_2切换到H_2时，端电压迅速趋于零。也可以从上述没有气体密封的燃料电池获得电流。然而，由于渗透选择性不足，不可能连续获得输出电压。将Al_2O_3平板、Al_2O_3膜和Rh-Al_2 O_3膜分别用于甲醇水蒸气重整反应（CH_3OH+H_2O*3H_2+CO_2）的膜反应器。在每种情况下，随着温度升高到250 ℃，转化率都急剧上升。在膜反应器的情况下，甲醇完全转化。甲醇转化率的顺序为：固定床反应器<多孔Al_2O_3板反应器<Al_2O_3膜反应器<Rh-Al_2 O_3膜反应器。该膜可有效地将生成的氢气从反应体系中去除。这种情况导致了高的总转化率，特别是使用Rh-Al_2 O_3膜。渗透侧气体的H_2/CO_2比较高。

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.