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Water pollution abatement is a problem in today’s society that requires urgent attention. Moreover, photocatalysts are an effective method to treat environmental pollution, and SnO2/reduced graphene oxide composite photocatalysts have been extensively studied in recent years. The synthesis parameters for these photocatalysts significantly affect their morphologies, structures, and properties. In this study, we investigated the effects of annealing temperatures on the properties of SnO2/reduced graphene oxide nanocomposites, which were hydrothermally fabricated at 180 °C for 24 h and annealed at 200 °C–800 °C. The structural characteristics of the fabricated nanocomposites were studied via x-ray diffraction, field emission scanning electron microscopy, and Raman scattering analyses. The observed results indicated that increasing the annealing temperature from 200 °C to 800 °C increased the average SnO2 nanoparticle size from 4.60 nm to 9.27 nm; in addition, the Raman scattering peaks of the SnO2 increased, and those of the reduced graphene oxide significantly decreased as the annealing temperature was increased. Furthermore, the specific surface area of the samples decreased due to the increase in calcination temperature. The amount of reduced graphene oxide content in all the samples was measured using thermo-gravimetric analysis. The optical properties of the samples were studied using ltraviolet–visible absorption spectra, and their photocatalytic activity was evaluated by decomposing methylene blue under visible light using the samples as catalysts. In particular, the photocatalytic properties of nanocomposites decreased significantly with increasing annealing temperature. Among the samples, the photocatalytic activity of that annealed at 200 °C is most satisfactory as it has the smallest particle size and the largest specific surface area. The results of our research could facilitate the production of efficient catalysts with suitable properties.

Recently, nanosized metal oxides play an essential role in the photocatalytic system due to their ability to create charge carriers during the light irradiation. Metal oxide nanoparticles display excellent light absorption properties, outstanding charge transport characteristics, which are suitable in the photocatalytic system for the treatment of wastewater. Most of the photocatalysts found in the literature are in the form of powders. Only a few supported photocatalytic systems have been reported. The advantages of supported photocatalysts, such as that they produce a small pressure drop, have good mechanical stability and are easily separated from the reaction medium, make them superior to conventional powder photocatalysts. In this chapter, the definition of supported-metal oxide nanoparticles as the photocatalyst and their synthesis methodology are detailed discussed.

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For the first time, the nanoflower-like zinc borate compound was obtained by precipitation at room temperature using zinc oxide nanoparticles as a precursor. The obtained zinc borates were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), thermal gravimetric analysis (TGA), and Raman spectroscopy analysis. Monoclinic of zinc borate 2ZnO. 3B 2 O 3 .3.5H 2 O was achieved under the XRD pattern and the elemental chemical analysis. The particle size of the obtained materials is approximately 5 nm using TEM analysis. The TGA shows that the achieved zinc borate is outstanding stable at high temperatures. The result of this work provides a new route for the fabrication of zinc borate nanoparticle, which could be widely used in many applications.