Proton Conduction in Nanopore-Controlled Silica Glasses

The proton conduction in the sol–gel-derived silica glasses was discussed to be related with the pore structure. The porous glasses with the pore size of 2 to 20 nm in diameter were prepared by the sol–gel method of Si-alkoxides. The proton conduction is promoted by the dissociation of proton from the hydroxyl bonds and the proton hopping through water molecules. The conductivities follow the Arrhenius equation and the activation energy decreases with increasing the logarithm of the product of proton and water concentration. The pore size plays an important role to absorb the water in pores, resulting into the determination of proton transfer. The glass having ∼5 nm diameter is more appropriate for the fast proton-conduction. The preparation of pore-controlled glass films exhibiting high conductivity is also described.