Nanosized titanium dioxide (TiO2) is currently being actively studied by the global scientific community, since it has a number of properties that are important from a practical point of view. One of these properties is a large specific surface, which makes this material promising for use in photocatalysts, sensors, solar cells, etc. In this work, we prepared photocatalysts based on TiO2 nanotubes for converting carbon dioxide (CO2) into energy-intensive hydrocarbon compounds. Efficient gas-phase CO2 conversion in the prepared single-walled TiO2 nanotube-CuxO composites was investigated. Parameters of defects (radicals) in composites were studied. Methanol and methane were detected during the CO2 photoreduction process. In single-walled TiO2 nanotubes, only Ti3+/oxygen vacancy defects were detected. The Cu2+ centers and O2− radicals were found in TiO2 nanotube-CuxO composites using the EPR technique. It has been established that copper oxide nanoparticles are present in the TiO2 nanotube-CuxO composites in the form of the CuO phase. A phase transformation of CuO to Cu2O takes place during illumination, as has been shown by EPR spectroscopy. It is shown that defects accumulate photoinduced charge carriers. The mechanism of methane and methanol formation is discussed. The results obtained are completely original and show high promise for the use of TiO2-CuxO nanotube composites as photocatalysts for CO2 conversion into hydrocarbon fuel precursors.
Titania is very famous photocatalyst for decomposition of organic pollutants. Its photocatalytic properties significantly depend on the morphology and chemical composition of the samples. Herein, the TiO2 nanotubes/CuxO nanoheterostructures have been synthesized and the effect of heat treatment performed in molecular atmospheres of air and argon on their photoelectrochemical and photocatalytic properties has been studied. The prepared samples have a higher reaction rate constant compared to TiO2 nanotubes in the decomposition reaction of methylene blue molecules. It is established that in argon treated nanoheterostructures, the copper oxide is present in two phases, CuO and Cu2O, while in air treated ones there is only CuO. In the TiO2 nanotubes/CuxO samples, Cu2+ ions and molecular O2− radicals were detected while in TiO2 nanotubes only carbon dangling bond defects are present. The dynamics of O2− radicals under illumination are discussed. It was shown that the TiO2 nanotubes do not exhibit photocatalytic activity under visible light. The mechanism of the photocatalytic reaction on the surface of the TiO2 nanotubes/CuxO samples was proposed. It is assumed that a photocatalytic decomposition of organic molecules under visible light at the surface of the nanoheterostructures under investigation is realized mainly by the reaction of these molecules with photogenerated O2− radicals. The results obtained are completely original and indicate the high promise of the prepared photocatalysts.
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