Abstract
In this study, various solid uranium oxycompounds and TiO2-supported materials based on nanocrystalline anatase TiO2 are synthesized using uranyl nitrate hexahydrate as a precursor. All uranium-contained samples are characterized using N2 adsorption, XRD, UV–vis, Raman, TEM, XPS and tested in the oxidation of a volatile organic compound under visible light of the blue region to find correlations between their physicochemical characteristics and photocatalytic activity. Both uranium oxycompounds and TiO2-supported materials are photocatalytically active and are able to completely oxidize gaseous organic compounds under visible light. If compared to the commercial visible-light TiO2 KRONOS® vlp 7000 photocatalyst used as a benchmark, solid uranium oxycompounds exhibit lower or comparable photocatalytic activity under blue light. At the same time, uranium compounds contained uranyl ion with a uranium charge state of 6+, exhibiting much higher activity than other compounds with a lower charge state of uranium. Immobilization of uranyl ions on the surface of nanocrystalline anatase TiO2 allows for substantial increase in visible-light activity. The photonic efficiency of reaction over uranyl-grafted TiO2, 12.2%, is 17 times higher than the efficiency for commercial vlp 7000 photocatalyst. Uranyl-grafted TiO2 has the potential as a visible-light photocatalyst for special areas of application where there is no strict control for use of uranium compounds (e.g., in spaceships or submarines).
Highlights
One of the simple methods for the synthesis of uranium oxides is the thermal decomposition of uranyl nitrate that can lead to the formation of UO3 and U3 O8 oxides
All the synthesized solid uranium oxycompounds and TiO2 -supported materials have a photocatalytic activity in oxidation reactions and are able to completely oxidize acetone in the gas-phase under blue (450 nm) light
It confirms that the potentials of excited states or charge carriers photogenerated under blue light are high enough that they can be involved in redox interactions with organic molecules and oxygen
Summary
Semiconductor photocatalysis has the potential for efficient utilization of light energy reaching the Earth from the Sun [1]. Semiconducting materials can be used for utilization of solar radiation via a number of routes: (i) to convert the energy of light directly into electricity by the photovoltaic effect using various silicon, cadmium telluride, copper indium gallium selenide, dye-sensitized ( well-known as Grätzel cells), perovskite, and other solar cells [2,3]; (ii) to store the energy in a form of chemical bond energy in fuels via photocatalytic or photoelectrochemical hydrogen evolution [4,5,6,7] and reduction of carbon dioxide [8,9,10]; (iii) to carry out useful chemical reactions, for instance, to synthesize highvalue products via partial selective photocatalytic or photoelectrochemical oxidation [11,12]. The photocatalytic processes can solve both energy and environmental issues
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