Titanate Nanofiber Reactivity: Fabrication of MTiO3 (M = Ca, Sr, and Ba) Perovskite Oxides

Titanate nanofiber, as an important morphology of one-dimensional nanostructured titanate, not only can be regarded as the final product derived from alkaline-hydrothermal treatment of bulk TiO2 but also can serve as initial reactant for fabricating complex functional materials with their parent morphology, which may be difficult to achieve using their bulk material counterparts under mild hydrothermal conditions. Based on titanate nanofiber reactivity, ternary MTiO3 (M = Ca, Sr, and Ba) perovskite oxides with specific morphologies have been fabricated in alkaline solution at low temperature via a soft chemical route. The resulting CaTiO3 products possessed a microtubular structure with rectangular cross-section, while SrTiO3 and BaTiO3 showed the assemblies consisting of aggregated particles in a compact fashion. On the basis of the experimental results, we have proposed two types of growth mechanisms to elucidate the formation processes of CaTiO3, SrTiO3, and BaTiO3 microstructures, respectively. The fabrication of microtubular CaTiO3 undergoes the initial dissolution of titanate nanofibers by Ostwald ripening process to convert into micrometer-sized fiber-bundles, while recrystallization occurs simultaneously until tubular microstrucures are obtained. The formation of SrTiO3 and BaTiO3 microstructures involves ion exchange reaction and in situ growth process at the self-sacrifice of titanate nanofibers framework based on the chemical reactivity. In addition, the photoelectrochemical properties of the as-obtained products are presented, and CaTiO3 microtubes exhibit better photoeletrochemical response relative to SrTiO3 and BaTiO3 microstructures.