Proton conductivity of mesoporous MCM type of zirconium and titanium phosphates

A family of novel mesoporous zirconium(IV) and titanium(IV) phosphate mater ials has been prepared by sol-gel synthesis in the presence of cetyltrimeth ylammonium bromide, a structure-directing cationic surfactant. The solids o btained after removal of the surfactant by acid-ethanol extraction or by ca lcination have high BET surface areas of 240-330 m(2)g(-1) and a narrow por e size distribution in the mesopore range. AC conductivity measurements of these solids were carried out by impedance spectroscopy. The data indicate that two electric relaxation processes are present; one at low frequency, a ssociated with the grain boundary and one at higher frequency related to a relaxation within the pores. Although a partial contribution of electronic conduction cannot be excluded, the major contribution comes from proton mob ility along the channels. (C) 1999 Elsevier Science B.V. All rights reserve d.