HIGH PROTON CONDUCTIVITY OF MESOPOROUS Al₂O₃

Mesoporous Al₂O₃ was synthesized by the sol-gel method and the pore size was controlled over the range of 3-15nm. Proton conductivity of these samples was examined, which was as high as 0.004 S·cm-1 at 25°C. A systematic dependence of conductivity upon pore size was observed, in which the conductivity increased with increasing the pore size. Meanwhile the conductivity increased with increasing the humidity. Two peaks were observed in ¹H NMR spectra, assigned to a "mobile" and an "immobile" proton, respectively. It can be seen that the conductivity of mesoporous-Al₂O₃ increased with increasing the "mobile" proton concentration. From TG-DTA measurement, proton species were categorized into three groups. It is suggested the group II protons have close relation with the NMR observed "mobile" protons.