Formation, structure, and stability of titanate nanotubes and their proton conductivity

High-yield H-form trititanate nanotubes have been synthesized, and their structures have been characterized by using X-ray diffraction and high-resolution transmission electron microscopy. According to combined TGA/XRD studies, the nanotubes are not stable at high temperature. Thermal analysis suggests that the stoichiometry of the material is H2Ti3O7 center dot 0.8H(2)O(abs). Conductivity measurements indicate that mainly protonic transport occurs at temperatures below 150 degrees C and that with increasing temperature and progressive breakdown of nanotubes and formation of crystalline TiO2 phases protonic conductivity is lost, leaving only residual defect electronic conduction. The proton conductivity is ca. 5.5 x 10(-6) S cm(-1) at 300 K. The structural protons and trapped water were confirmed by solid-state NMR.