Abstract
The structure of porous TiO2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small angle neutron scattering (SANS) and ultra small angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular shape, were broadly distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating the interface between TiO2 and the pore was not sharp. A density gradient of around 40 ~ 60 Å at the pore wall (i.e. interface between the pore and the TiO2 matrix) was estimated using both constant and semi-sigmoidal interface models. This may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte and sorbed water molecules on the wall. The neutron contrast-matching point between the TiO2 matrix and the pores filled with liquid H2O/D2O mixtures was 51/49 vol/vol H2O/D2O, yielding an estimated mass density of 3.32 g/cm3. The specific surface area of the sample derived from the (U)SANS data, S/V, was around 939 ~ 1003 m2/cm3 (283~ 302m2/g).
