Preparation of nano-structured proton conductive ceramic membranes and membrane electrode assembly (MEA) system

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Titanium phosphorus oxide (TiP) and composites with titania (Ti/TiP) were prepared by a sol-gel method. Tip membranes coated on slide glasses showed high electrical conductivities based on surface resistivity measurements at 150℃. The conductivities increased drastically with the partial pressure of water in the range of 0 to 10 kPa, and showed an electrical conductivity as high as 10^<-2> S/cm at a vapor pressure of 2.5 kPa (relative humidity of 0.5 RH%). Two types of membrane-electrode assemblies (MEAs) : a pore-filling-type and a thin-film-type, were constructed using Anodisc【○!R】, a porous alumina membrane (pore size : 100 nm ; thickness 60 μm). The proton transport number through the pore-filling type MEA was found to be approximately one. The two types of MEAs were successfully used in fuel cell experiments in a hydrogen/ air system. The performance of the thin-film-type MEA was superior to the pore-filling-type MEA. Moreover, two types of thin-film type of MEAs were prepared using electrically-conductive porous carbon substrates. MEA-2, which were prepared after fabricating an intermediate layer consisting of mixtures of carbon particles and polyimide, showed a better i-v performance than MEA-1, which were prepared directly on porous carbon substrate.