Temperature-controlled synthesis and photocatalytic properties of ZnO–SnO2 nanocomposites

The objective of this work was the synthesis of a zinc oxide‑tin oxide (ZnO‑SnO2; ZT) nanocomposite while controlling the growth structure with the calcination temperature and the photocatalytic degradation of a rhodamine B (RhB) dye solution. Zinc acetate, tin chloride, and sodium hydroxide were used as the precursor. In the study of the effect of the reaction temperature on the synthesis, the synthesis of the ZT nanocomposite had a temperature change in the range of 300–800 °C when the mole ratio of the precursors and other factors were held constant. The effect of the synthesis reaction temperature on the photocatalytic activity was examined. The synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (UV–DRS), and photoluminescence (PL) spectroscopy. Results showed that the synthesized ZT nanocomposites consisted of hexagonal ZnO and tetragonal SnO2. The content of SnO2 in the sample increased evidently with increasing reaction temperature. The experimental findings showed that increasing the reaction temperature resulted in favorable chemical and physical properties for the ZT nanocomposite photocatalytic reactions, such as high-purity phases, high crystallinity, and lower rates of electron–hole pair recombination. RhB was used as the representative pollutant for evaluating the photocatalytic activity under UV illumination. The ZT nanocomposite synthesized at 800 °C showed the highest photodegradation efficiency of 79.53% and a first-order kinetic rate constant of 0.0139 min−1 in 120 min. The most influential factors affecting the photocatalytic activity were the phase proportions and the phase purity of the ZT nanocomposite, which were controlled via the calcination temperature.