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 in shape, were widely 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 that
the interface between TiO2 and the pore was not sharp. A density gradient of
around 40–60 A ° at the pore wall (i.e. the interface between the pore and the
TiO2 matrix) was estimated using both constant and semi-sigmoidal interface
models. This gradient may be due to the presence of fluorine and carbon
partially absorbed by the pore wall from the fluoride-containing electrolyte or to
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%(v/v) 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 was around
939–1003 m2 cm3 (283–302 m2 g1).
