Characterization and photoactivity of coupled ZnO–ZnWO4 catalysts prepared by a sol–gel method

• ZnO–ZnWO4 nanocomposites were prepared by a facile sol–gel synthesis.
• The photoactivity of the samples was studied using the degradation of 4-nitrophenol.
• The photocatalytic activity depended on the ZnO/ZnWO4 molar ratio.
• The high photoactivity was attributed to the presence of heterojunctions ZnO–ZnWO4.

ZnO–ZnWO4 nanocomposites were synthesized by a novel sol–gel method and characterized through X-ray diffraction, BET specific surface area analysis, UV–Vis diffuse reflectance spectroscopy, scanning electron microscopy and transmission electron microscopy. The photocatalytic activity of the samples was evaluated using the degradation of 4-nitrophenol under UV light as probe reaction. The ZnO/ZnWO4 molar ratio was varied in order to study its influence on the photoefficiency of the mixed samples. The ZnO–ZnWO4 nanocomposites showed higher photoactivity than ZnO and ZnWO4. The high efficiency of the mixed samples was explained by the coupling and the intimate contact of two different semiconductors having suitable energy levels of their conduction and valence bands that allow an improved charge separation of the photogenerated electron–hole pairs.

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