Surface X-ray diffraction study and photocatalytic activity of HF-treated single crystal rutile TiO2(001) surface

The photocatalytic activity of a hydrogen fluoride (HF)-treated rutile TiO2(001) surface for the decomposition reaction of linoleic acid was lower than that of an as-received (polished) rutile TiO2(001) surface. The surfaces of as-received TiO2(001) and HF-treated TiO2(001) were investigated using low-energy electron diffraction (LEED) and surface X-ray diffraction (SXRD) to elucidate differences in their photocatalytic activities. The as-received (polished) surface did not yield good LEED patterns, which implied that the surface was not well-ordered and was thus not examined using SXRD. In contrast, the HF-treated surface produced good LEED patterns with a 1 x 1 structure and was thus studied using SXRD. The analysis of crystal truncation rods indicated that all atoms in the four layers of the surface moved toward the bulk and that the HF-treated surface was (101)-faceted with terraces. On average, the facet was found to be four layers deep. The difference in the condition of the surface influences the photocatalytic activity of the surface.