Abstract
We evaluate the influence of the use of different titania precursors, calcination rate, and ligand addition on the morphology, texture and phase content of synthesized mesoporous titania samples, parameters which, in turn, can play a key role in titania photocatalytic performances. The powders, obtained through the evaporation-induced self-assembly method, are characterized by means of ex situ X-Ray Powder Diffraction (XRPD) measurements, N2 physisorption isotherms and transmission electron microscopy. The precursors are selected basing on two different approaches: the acid-base pair, using TiCl4 and Ti(OBu)4, and a more classic route with Ti(OiPr)4 and HCl. For both precursors, different specimens were prepared by resorting to different calcination rates and with and without the addition of acetylacetone, that creates coordinated species with lower hydrolysis rates, and with different calcination rates. Each sample was employed as photoanode and tested in the water splitting reaction by recording I-V curves and comparing the results with commercial P25 powders. The complex data framework suggests that a narrow pore size distribution, due to the use of acetylacetone, plays a major role in the photoactivity, leading to a current density value higher than that of P25.
Highlights
Titania is one of the most studied materials because of its unique properties that include chemical stability, low cost, nontoxicity together with optimal electronic, and optical capacity, that make it a promising candidate for photocatalytic applications [1,2,3,4,5,6,7]
We report the synthesis of mesoporous crystalline titania powders by the evaporation-induced self-assembly (EISA) method according to the acid-base pairs concept by using TiCl4 and Ti(OBu)4 as precursors or a more “classic”
In order to find clear evidence on the effect of these parameters on the photocatalytic activity of the powders, all titania samples were tested as photoanodes in a photoelectrochemical cell (PEC) for the water splitting reaction and their performances were compared to the corresponding data of P25 powders, considered as a reference material
Summary
Titania is one of the most studied materials because of its unique properties that include chemical stability, low cost, nontoxicity together with optimal electronic, and optical capacity, that make it a promising candidate for photocatalytic applications [1,2,3,4,5,6,7]. In order to slow down the reaction kinetics of titania precursors, usually alkoxides, the initial solution is kept at low pH levels by adding hydrocloric acid, implying the addition of water to the organic solvent and leading to uncontrolled processes. A valid alternative to HCl is represented by the addtion of titanium tetrachloride together with a titanium alkoxide in a so-called acid-base pairs approach [15,16], with the former being the pH “adjustor” and hydrolysis-condensation controller Another suitable method of controlling the high reactivity of transition metals is the addition of coordinating molecules like acetylacetone that chelate the precursor forming metal complexes with lower hydrolysis kinetics [17]. On the photocatalytic activity of the powders, all titania samples were tested as photoanodes in a photoelectrochemical cell (PEC) for the water splitting reaction and their performances were compared to the corresponding data of P25 powders, considered as a reference material
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