Abstract
Abstract Mesoporous hierarchical TiO 2 microspheres (MSs) with a size of 1–3 μm and an average pore size of 12.2–17.5 nm composed of smaller spherical 40–60-nm aggregates of discrete ∼10-nm anatase nanocrystals (NCs) were produced by the sol-gel transformation of Ti(IV) tetra butoxide in the presence of dibenzo-18-crown-6. Photocatalytic and photoelectrochemical properties of the TiO 2 MSs were studied in several processes important for the sustainable light-to-energy conversion and environmental photocatalysis. In particular, the TiO 2 MSs were found to be a much more efficient photocatalyst of the water reduction and the gas-phase oxidation of benzene and ethanol than irregularly aggregated mesoporous TiO 2 and a benchmark Evonik P25 TiO 2 . The MSs also revealed an advanced photoelectrochemical activity. The most probable reasons for the high photochemical activity of the MSs are (i) the effect of multiple scattering and reflection of light passing through the MSs that increases the probability of light absorption and (ii) the electron transport through the framework of interconnected loosely aggregated anatase NCs that results in suppression of the electron-hole recombination. In the photoelectrochemical cells based on the MS/CdS heterostructures the light is absorbed by a thin layer of the visible-light-sensitive CdS NCs and the advantages of the MSs are leveled off, the activity of TiO 2 as an electron transporting layer most probably limited by electrons leakage to the electrolyte.
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More From: Journal of Photochemistry and Photobiology A: Chemistry
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