The effect of Zr loading in Zr/TiO ₂ prepared by pressurized hot water on its surface, morphological and photocatalytic properties

Zr/TiO ₂ anatase photocatalysts with 0.5, 1, 2, 5 and 7.5 mol.% Zr were prepared using pressurized hot water crystallization and their photocatalytic activity was explored in acid orange 7 photodegradation. Parent TiO ₂ was also prepared and tested. From all tested photocatalysts, 2 mol.% Zr/TiO ₂ showed the highest photoactivity, and 7.5 mol.% Zr/TiO ₂ showed the lowest photoactivity. The poor photoactivity of 7.5 mol.% Zr/TiO ₂ can be explained by the amorphous ZrO ₂ present in the surface layer (~1–3 μm depth) of TiO ₂ anatase nanocrystallite agregates which changed the aggregate morphology and shielded the anatase nanocrystallite surface. The type and amount of defects (e.g., oxygen vacancies, lattice defects) did not effect the photoactivity of Zr/TiO ₂ in AO7 photodegradation. The addition of Zr to TiO ₂ significantly affects the photocatalyst morphology and the location where amorphous ZrO ₂ forms. The optimal Zr loading in TiO ₂ was determined to be 2 mol.%. [Figure not available: see fulltext.]