Effect of pore orientation on proton conductivity of porous phosphosilicate glass films

Proton conductivity of ordered mesoporous phosphosilicate glass films, prepared by an interfacial self-assembly technique, was related with the water molecules absorbed in the ordered pores. The mixed solutions of hydrolyzed-alkoxides and cationic surfactant CH3(CH2)15N+(CH3)3Br− were coated on the substrates, followed by heating to remove the surfactant at 400 °C. Pore channels parallel to the substrate surface were formed by dip-coating the solution, which did not offer a pathway for proton transfer, resulting in the low conductivity of the film. The aging of the precursor solutions before coating caused the pores to orient from two- to three-dimensionally ordered structure. The water molecules absorbed in the three dimensionally connected pores acted as the pathway for proton transfer, resulting in the increased conductivity.