Abstract
The glasses prepared by a sol-gel technique are porous, the surfaces of which are composed of the hydroxyl bonds and covered with water molecules. We found that the proton conductivities proportionally increase in log-log scale with the increasing content of both the hydroxyl and water molecules in the pores. The pore structure primarily determines the adsorption of the water molecules. In glasses having pores with size smaller than about 5 nm, the water molecules totally fill the pores, in which the motion of the water molecules is restricted in the pore and the adsorbed waters are well retained even under low humidity. The glass compositions were also investigated to relate with the proton conduction. The conductivities of these glasses were high in temperature range down to -20°C and∼170 mS/cm at 150°C. Thus, the sol-gel-derived glasses have potential for the electrolyte of the fuel cell operating in the wide temperature range.
