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Orthorhombic molybdenum trioxide (α-MoO3) is well known as a photocatalyst, adsorbent, and inhibitor during methyl orange photocatalytic degradation via TiO2. Therefore, besides the latter, other active photocatalysts, such as AgBr, ZnO, BiOI, and Cu2O, were assessed via the degradation of methyl orange and phenol in the presence of α-MoO3 using UV-A- and visible-light irradiation. Even though α-MoO3 could be used as a visible-light-driven photocatalyst, our results demonstrated that its presence in the reaction medium strongly inhibits the photocatalytic activity of TiO2, BiOI, Cu2O, and ZnO, while only the activity AgBr is not affected. Therefore, α-MoO3 might be an effective and stable inhibitor for photocatalytic processes to evaluate the newly explored photocatalysts. Quenching the photocatalytic reactions can offer information about the reaction mechanism. Moreover, the absence of photocatalytic inhibition suggests that besides photocatalytic processes, parallel reactions take place. [ABSTRACT FROM AUTHOR]

Bismuth oxychloride photocatalysts were obtained using solvothermal synthesis and different additives (CTAB—cetyltrimethylammonium bromide, CTAC—cetyltrimethylammonium chloride, PVP–polyvinylpyrrolidone, SDS–sodium dodecylsulphate, U—urea and TU—thiourea). The effect of the previously mentioned compounds was analyzed applying structural (primary crystallite size, crystal phase composition, etc.), morphological (particle geometry), optical (band gap energy) parameters, surface related properties (surface atoms' oxidation states), and the resulted photocatalytic activity. A strong dependency was found between the surface tension of the synthesis solutions and the overall morpho-structural parameters. The main finding was that the characteristics of the semiconductors can be tuned by modifying the surface tension of the synthesis mixture. It was observed after the photocatalytic degradation, that the white semiconductor turned to grey. Furthermore, we attempted to explain the gray color of BiOCl catalysts after the photocatalytic decompositions by Raman and XPS studies. [ABSTRACT FROM AUTHOR]