Some sintered oxides based on BaCeO3 were found to exhibit appreciable proton conduction under hydrogen= containing atmosphere at high temperature. The verification of proton conduction was made by studying the EMF of various gas cells using the specimen ceramics as the solid electrolyte. The protonic conductivity in the Nd203 doped BaCeO3 was higher than that in the SrCeO3-based proton conductor found previously by us. These materials could be applied to the solid electrolyte for a hydrogen fuel cell, a hydrogen pump, and a steam electrolyzer to produce hydrogen.

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The iodine-modified Ag(111) substrate was employed as an electrode to investigate the adsorption of 5,10,-15,20-tetrakis(N-methylpyridinium-4-yl)-21H,23H-porphine tetrakis(p-toluenesulfonate) (TMPyP) in an alkaline solution containing KI. It was found by using in situ scanning tunneling microscopy (STM) that water soluble TMPyP molecules were irreversibly adsorbed and formed highly ordered molecular adlayers on the surface of the iodine-modified Ag(111) electrode within the potential range of -0.35 to -0.10 V vs Ag/AgI. STM images revealed the characterstic shape, internal molecular structure, and molecular orientation of each TMPyP molecule in ordered adlayers. The ordered TMPyP adlayer usually consisted of stripes of several straight molecular rows with different orientations along the 3 direction of the underlying iodine adlayers. In each row, molecules were aligned with the same orientation. From the time-dependent imaging, the ordered molecular adlayer was found to grow in the specific 3 direction with an averaged growth rate of ca. 6 nm/s.

ChemInform Abstract Some sintered BaCeO3-based ceramics are found to exhibit appreciable protonic conductivity in water or hydrogen containing atmospheres, although they are p-type conductors in dry atmospheres. The protonic conductivities of Nd2O3-, La2O3-, or Y2O3-doped BaCeO3 ceramics are higher than that of Yb2O3-doped SrCeO3. The BaCeO3-based materials may be applicable as solid electrolytes in hydrogen fuel cells, hydrogen pumps, and steam electrolyzers.

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