The set of Al-doped titania x-Al-TiO 2 (x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, 1.1 wt% Al) has been synthetized by sol-gel method and tested in the reaction of photocatalytic degradation of phenol in aqueous suspension. XRD and Raman studies show that TiO 2 samples have mixedphase rutile-anatase crystalline structure with linear increase of anatase fraction from 0.0 wt% for 0.0-Al-TiO 2 up to 18 wt% for 1.1-Al-TiO 2 . The decrease of the particle size from ∼ 800 nm to 50 nm and the increase of specific surface area from 1.7 m 2 /g up to 28 m 2 /g with increased content of Al have been observed. The data of XRD, XPS, Raman spectroscopy and EDS

This article reports on two novel visible-light-active strontium bismuthate photocatalysts (Sr 6 Bi 2 O 11 and Sr 3 Bi 2 O 6) prepared by solid-state synthesis for which the number of strontium atoms exceeded the number of bismuth atoms in the cation sublattice; for comparison, the bismuthate Sr 2 Bi 2 O 5 was also reexamined. All three bismuthates were characterized by a variety of spectroscopic techniques (XRD, XPS, EDX, DR, Raman, SEM, and EIS). Both newly as-synthesized bismuthates displayed photocatalytic activity toward the photodegradation of substrates in the gas phase (acetaldehyde) and in aqueous media (phenol), with the Sr 6 Bi 2 O 11 phase exhibiting a significantly greater photoactivity than the Sr 3 Bi 2 O 6 phase; by comparison, the bismuthate Sr 2 Bi 2 O 5 was photocatalytically inactive. Detailed photocatalytic mechanisms have been proposed to explain how composition and structure of the three bismuthates affect their photocatalytic activity. The role of point defects in their crystal lattice is described for processes in which the photocatalytic activity was inhibited. Inferences made were aided by examining the UV-induced coloration of these ternary metal oxides that provided information regarding defect levels within their respective bandgaps; such defects acted as electron traps and thus affected the photocatalytic performance of the bismuthates.

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