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Unraveling the Multiple Effects Originating the Increased Oxidative Photoactivity of {001}-Facet Enriched Anatase TiO2

Maisano, Michela, Dozzi, Maria Vittoria, Coduri, Mauro, Artiglia, Luca, Granozzi, Gaetano, Selli, Elena
ACS Applied Materials & Interfaces 2016 v.8 no.15 pp. 9745-9754
adsorption, annealing, crystals, fluorine, formic acid, heat treatment, photocatalysis, photocatalysts, photooxidation, physicochemical properties, titanium dioxide
Crystal shape control on a series of anatase photocatalysts was achieved by varying the amount of HF employed as a capping agent in their hydrothermal synthesis. A systematic comparison between their physicochemical properties, determined by several complementary surface and bulk techniques before and after thermal treatment at 500 °C, allowed one to discern the influence of the relative amount of exposed {001} crystal facets among a series of effects simultaneously affecting their oxidative photocatalytic activity. The results of both formic acid and terephthalic acid photo-oxidation test reactions point to the primary role played by calcination in making {001} facets effectively photoactive. Annealing not only removes most of the residual fluorine capping agent from the photocatalyst surface, thus favoring substrate adsorption, but also produces morphological modifications to a crystal packing that makes accessible a larger portion of surface {001} facets due to the unpiling of platelike crystals. The photocatalyst bearing the highest amount of exposed {001} facets (60%) shows the highest photoactivity in both the direct and the •OH-radical-mediated photocatalytic test reaction.