Highly efficient rutile TiO_{2}$ photocatalysts with single Cu(II) and Fe(III) surface catalytic sites
| Autor: | Radim Beranek, Wojciech Macyk, Dariusz Mitoraj, Zhengxiao Guo, Krzysztof Kruczała, Stephen A. Shevlin, Manuel Heimann, Susann Neubert, Yonghua Du, Stuart Turner, Petra Pulisova, Rosalie K. Hocking, Gregory K. L. Goh, Michał Pacia |
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| Jazyk: | angličtina |
| Rok vydání: | 2016 |
| Předmět: |
Reaction mechanism
Radical Inorganic chemistry 02 engineering and technology 010402 general chemistry Photochemistry 01 natural sciences 7. Clean energy Redox Catalysis law.invention law Oxidizing agent General Materials Science Electron paramagnetic resonance Renewable Energy Sustainability and the Environment Chemistry Physics General Chemistry 021001 nanoscience & nanotechnology 0104 chemical sciences Rutile Photocatalysis 0210 nano-technology Engineering sciences. Technology |
| Zdroj: | Journal of materials chemistry A : materials for energy and sustainability BASE-Bielefeld Academic Search Engine |
| ISSN: | 2050-7488 |
| Popis: | Highly active photocatalysts were obtained by impregnation of nanocrystalline rutile TiO2 powders with small amounts of Cu(II) and Fe(III) ions, resulting in the enhancement of initial rates of photocatalytic degradation of 4-chlorophenol in water by factors of 7 and 4, compared to pristine rutile, respectively. Detailed structural analysis by EPR and X-ray absorption spectroscopy (EXAFS) revealed that Cu(II) and Fe(III) are present as single species on the rutile surface. The mechanism of the photoactivity enhancement was elucidated by a combination of DFT calculations and detailed experimental mechanistic studies including photoluminescence measurements, photocatalytic experiments using scavengers, OH radical detection, and photopotential transient measurements. The results demonstrate that the single Cu(II) and Fe(III) ions act as effective cocatalytic sites, enhancing the charge separation, catalyzing "dark" redox reactions at the interface, thus improving the normally very low quantum yields of UV light-activated TiO2 photocatalysts. The exact mechanism of the photoactivity enhancement differs depending on the nature of the cocatalyst. Cu(II)-decorated samples exhibit fast transfer of photogenerated electrons to Cu(II/I) sites, followed by enhanced catalysis of dioxygen reduction, resulting in improved charge separation and higher photocatalytic degradation rates. At Fe(III)-modified rutile the rate of dioxygen reduction is not improved and the photocatalytic enhancement is attributed to higher production of highly oxidizing hydroxyl radicals produced by alternative oxygen reduction pathways opened by the presence of catalytic Fe(III/II) sites. Importantly, it was demonstrated that excessive heat treatment (at 450 degrees C) of photocatalysts leads to loss of activity due to migration of Cu(II) and Fe(III) ions from TiO2 surface to the bulk, accompanied by formation of oxygen vacancies. The demonstrated variety of mechanisms of photoactivity enhancement at single site catalyst-modified photocatalysts holds promise for developing further tailored photocatalysts for various applications. |
| Databáze: | OpenAIRE |
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