Photocatalytic activity of nanostructured γ-Al2O3/TiO2 composite powder formed via a polyelectrolyte-multilayer-assisted sol–gel reaction

Highlights: ► PEM assisted synthesis for γ-Al2O3/TiO2 composite powder is developed. ► Nanoparticulate TiO2 layer results in high specific surface area composite powder. ► γ-Al2O3/TiO2 composite powder exhibit enhanced photocatalytic activity. -- Abstract: Nanostructured, γ-Al2O3/TiO2 composite powder was fabricated via an in situ, sol–gel reaction of titanium iso-propoxide in a self-assembled, polyelectrolyte multilayer (PEM) formed on the surface of high-specific-area, polycrystalline, γ-Al2O3 lamellas. The infiltration of the titanium precursor into the PEM, followed by the hydrolysis and condensation reactions with the water absorbed in the PEM after annealing, resulted in the formation of a nanostructured TiO2 layer on the surface of the γ-Al2O3 lamellas. Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) were employed to evaluate the morphology, the chemical composition and the crystallinity of the γ-Al2O3/TiO2 particles of the composite powder. The as-formed, nanostructured, γ-Al2O3/TiO2 composite powder exhibited a 2.7-times-higher photo-activity in the near-UV region compared to commercially available TiO2 (Degusa P25), as monitored by the photo-decomposition of a methylene blue (MB) dye.